Heat stress in dairy cattle

007000

RURAL CHEMICAL INDUSTRIES (AUST) PTY. LTD.

007000

Heat Stress in Dairy Cattle This publication discusses the significance of Dietary Electrolyte Balance, it explains the reason the effects are so wide-ranging, examines some aspects of the cellular chemistry involved and evaluates the benefits of controlling deep body temperature while maintaining D.E.B. It addresses the treatment and control measures which can be used to minimise preventable production wastage caused by an inadequate D.E.B. level during heat stress.

Presented by: Rural Chemical Industries (Aust) Pty Ltd PO Box 6316 South Sydney Business Hub Alexandria NSW 2015 Australia Phone: 61 2 9667 0700 Fax: 61 2 9669 0430 E-mail: info@rci.com.au Web Sites: www.rci.com.au,

www.anigane.info www.heatstress.info www.selectolyte.info

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Heat Stress in Dairy Cattle in production-limiting environments

An Overview In the last decade the importance of Dietary Electrolyte Balance (D.E.B.), has assumed significance in the feeding of dairy cattle.

Research has shown it is especially important in locations where environmental temperatures exceed 24°C and is exacerbated if relative humidity is in excess of 50%.

These hostile conditions are known as production-limiting environments.

Production losses in these locations are mainly due to Heat Stress.

Dairy production in these climatic conditions requires heavily capitalised enterprises and demands different management standards from those of conventional temperate zone dairy farming.

•

Comparisons of productivity and efficiency should only be made with similar enterprises in the same general location. Comparing your herd performance with herd performance in countries where the gene profile originated is misleading and quite invalid.

•

Under these hostile climatic conditions it is most profitable to concentrate on those areas of preventable production wastage which arise from health problems associated with production-limiting environments.

The main components of a successful enterprise are: •

Nutrition

•

Inheritance

•

Accommodation and Environment

•

Herd management with Stress Minimisation

•

Preventable production wastage caused by environmentally-induced health problems.

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To evaluate preventable production wastage we need to know:

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That the impact of the stressful conditions of heat and humidity is now recognised as being responsible for 60% (or more) of all the wastage of animal production in hostile environments This is described in the literature as HEAT STRESS resulting in the loss of DIETARY ELECTROLYTE BALANCE (ions) and ACID/BASE BALANCE.

•

Research has now demonstrated that the balance between "Anions" and "Cations" has fundamental effects on the performance of all animal species.

This effect is quite separate from the importance of the individual mineral ions in the diet.

Ions generate acid or base according to metabolic reactions in which they are involved thus impacting on acid/base balance.

•

There are between species differences and these differences appear to differ according to the physiological phase of the animal. These phenomena are widespread throughout the animal kingdom and reflect their fundamental importance in production especially in production-limiting environments.

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Optimal D.E.B. values for different stages of production have not yet been fully researched. It is not surprising that research into the effects of temperatures above 32°C is scarce. However it is clear that it is the disturbance of D.E.B. balance which results in the major production losses associated with Heat Stress.

•

That the major electrolytes involved in Dietary Electrolyte Balance are Sodium Na+, Potassium K+, Chlorine Cl- and the buffer Bicarbonate. HCO3-. Sulphur, S= is not considered so critical in the equation for dairy cattle.

For details of the functions of these ions turn to pages 29-31.

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The effects of loss of D.E.B. and ACID/BASE BALANCE associated with HEAT STRESS are insidious and widespread.

• Appetite is depressed, there is some indigestibility of feed and gut motility is slowed.

• Milk Yield - at 35°C there is up to 33 % depression and at 40°C, as much as 50%.

• There is loss of milk quality - fat and protein content declines • There is loss of body weight • The incidence of milk fever increases.

• Metritis is more widespread • Uterine prolapse is more common • Mammary gland infections increase • There are increased uterine infections • Udder oedema is more severe • Laminitis is more frequent • Keto-acidosis is a recurring problem • Fertility is lowered - insemination success rate falls, embryo mortality increases • Calves are often premature and small • Growing animals have markedly reduced weight gains.

• Drinking water intake increases •

Nutrient deficiencies occur in marginally adequate diets

Refer to Chart 1, page 6

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EFFECT OF HEAT STRESS ON LACTATION

MILK PRODUCTION PER LACTATION

Zone of comfort 0 0 4 C - 24 C - above this deep body temperature rises

Increased water intake up to 135L or more

Stand around

Panting Sweating

More ions lost

Loss of appetite

Acid/base balance disturbed produces metabolic alkalosis Loss of ions

More urine

Loss in - milk production - milk quality

More ions lost +

+

Reduced dry matter intake

-

Na K HCO3 + - especially K Loss increases 5 times if shade is not provided

Fertility declines with increased embryo mortality Calving disorders Calves tend to be premature

Overall loss of resistance to disease

TIME

Assessment of Nutritional and D.E.B. status and programs to reduce preventable production wastage.

A. Cows in full production • Calculate D.E.B. value of the total dietary intake. (See page 23 for method of calculation) In production-limiting environments this should always exceed 400-450 mEq/Kg • To replenish loss of electrolytes and to correct D.E.B. imbalance immediately add Selectolyte to the drinking water at 1-2 g/L • To stimulate appetite add Anigane to the drinking water at 1 L/3000L. To further fortify the diet with key electrolytes, ammonia-reducing agents, osmolytes and ion-exchangers add DEB++9 to the concentrate feed at 20 Kg/tonne.

Refer to Chart 2, page 8

• Reduce identified chloride levels of the diet by 50% This can be achieved by * Removing salt from the ration * Removing salt blocks and licks from the area * Reducing the total dissolved salts in the drinking water Many areas rely entirely on underground water which is high in T.D.S. The level of key electrolytes in the water should be taken into account when calculating and manipulating D.E.B. Dissolved elements cannot be filtered from the water supply. To reduce T.D.S. three approaches may be considered: • Desalination to remove chloride • Reverse osmosis to reduce levels of all dissolved minerals • Evaporate and collect condensate to remove all dissolved elements Consult with your local authority for the best method in your area

Note: Total dietary intake includes food and drinking water.

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MILK PRODUCTION PER LACTATION

MANAGED D.E.B. AND PRODUCTION IN HEAT STRESS CONDITIONS

Offsets the effects of Heat Stress

Higher milk yield and quality

Added ions restore acid/base balance

Dry matter intake increased

Less calving disorders (milk fever) & laminitis, mastitis and keto acidosis may also be reduced

Paresis is reduced

Prolonged lactation

CONCURRENT ANIMAL HUSBANDRY PROGRAMME

MANAGED D.E.B. PROGRAM * SELECTOLYTE - replaces lost electrolytes * DEB++9

- restores acid/base balance - supplies ion exchangers, osmolytes

* ANIGANE

- to stimulate appetite

Increases mEq/Kg value of the diet to compensate for constant losses

TIME TIME

* * * * * * *

Provide good shade and ventilation Increase feeding frequency Protect water lines and tanks from the sun Increase protein early in lactation (to 20%) Reduce chlorine levels by 50% Reduce roughage Increase nutrient density

B. Dry Cows - 30 day period pre-calving - at steaming up • Add 0.5 Kg Negalyte to the concentrate feed twice daily Add 60 mL Anigane to each concentrate feed • Increase protein level of diet to 20% After calving gradually switch to the Cows in Full Production program

Refer to Chart 3, page 10

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DRY COW MANAGEMENT

MILK PRODUCTION PER LACTATION

Critical pre-calving “Dry Cow” period D.E.B to be reduced drastically from strongly cationic to anionic eg from +400 mEq/KgDM to -100 to -150 mEq IMPROVES overall lactation output by say 500 Kg

DRASTICALLY REDUCES * Milk fever * Udder oedema

Pre-Calving:

After calving switch to:

MANAGED PROGRAMME

and REDUCES RISK of

* NEGALYTE Introduced gradually to 1 Kg/Head/Day

* * * *

Dystochia Retained foetal membranes Metritis Prolapsed uterus

MANAGED D.EB. PROGRAMME * SELECTOLYTE * DEB++9 * ANIGANE

CALVING 30 DAYS

TIME M:\P\G\DEB.CDR P3

SUMMARY OF RCI REFERENCES ON LACTATING AND DRY COW D.E.B. VALUES AND THEIR MANIPULATION [1984-1996] 1, 3,4,etc

•

• • • • • • • •

• •

See pages 32 and 33 for details of references

Alteration of the Dietary Electrolyte Balance is proving beneficial in both dry and lactating dairy cow diets. The response is mediated through the acid-base chemistry of the cow and the desired balance depends on whether the cow is dry or lactating.

Use of Dietary Electrolyte Balance techniques requires skilful nutritional formulation and good feeding management is necessary for success.1 D.E.B. manipulation demonstrates how different are the needs of the cow depending on her lactational status.

Exact data required includes sodium and potassium ratios in the D.E.B. equation for heat-stressed cows. 1 Based on 1989 N.R.C. standards for Na. K and Cl., the calculated D.E.B. is 238 mEq/Kg DM for a lactating cow in temperate conditions.

Greater milk yield was reported when D.E.B. was 324 mEq/Kg DM. This response was similar whether there were cool or hot environmental conditions.4 Hot weather results support Texas work where 320 mEq/Kg DM improved DM intake and milk yield when compared with D.E.B. values of 168 or 191.3 The DMI of cows improved linearly as D.E.B. values increased from 120 to 464 mEq/Kg DM. in hot, summer conditions. 4 Heat stressed cows produced better when potassium values above NRC (1989) recommendations were used.5 Sulphur should also be used in the equation [Na + K -Cl] ie.

[Na + K] - [Cl + S] but the absorption of sulphur is more difficult to quantify.

However in general for lactating cows [Na + K-CI] is an adequate formula as the positive D.E.B. value is high (alkaline) and sulphur (an acidifying agent) is less important. 5 Intake response occurs over a wide range and was greatest around 350-400 mEq when milk yield peaked. 7

DRY COWS AND D.E.B. •

• • •

Metabolic disorders at calving may have long-lasting effects. Milk fever not only causes downer cows (and deaths) but is a risk factor for dystochia, retained foetal membranes, metritis and prolapsed uterus.9 Loss of ruminal contractions, disturbed digestive processes frequently arise before signs of hypocalcaemia.6 Udder oedema regresses more rapidly for cows fed low D.E.B. diets.7 Pre-partum diets made alkaline (high D.E.B. value) with buffers caused a high incidence of milk fever while the same diet supplemented with sulphates and chlorides (acidifying to low D.E.B.) resulted in mostly healthy cows. 11

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The high incidence of milk fever in high cationic diets, with high D.E.B. + 449 mEq/Kg DM which resulted in 47.4% incidence could be reduced to zero by adding anionic salts which produced a low D.E.B. - 172 mEq/Kg DM pre-partum. Subsequent milk production was 7142 and 6656 Kg for anionic and cationic diets respectively. 12 Dietary sulphur was the variable most highly correlated with milk fever and it was concluded that sulphur and chlorine had similar effects on Acid-Base status. 15 1.5% CaCl2 (DM Basis) fed for 21 days before expected calving date reduced the severity of oedema and DM intake pre-partum but a compensatory increase followed post-partum.

Hence feeding CaCl2 pre-partum to prevent milk fever may also reduce the severity of udder oedema pre-partum and increase feed intake during early lactation.20

HEAT STRESS AND DIETARY ELECTROLYTE IMBALANCE • •

• •

The zone of comfort of the cow is 4°C-24°C. Performance declines above 24°C. Experiments in Florida, Georgia and Kentucky showed that potassium requirements in the diet. increased from 1.5% (DM basis) in winter, to 1.9% in summer.

Sodium levels remained the same for both seasons at 0.65%.

Chlorine, at 0.55% DMB in winter reduced to 0.25% in summer. When chlorine was increased in either summer or winter, milk yield declined. 12. 17.

Combined effects of elevated potassium loss from the skin, and reduced dry matter (and potassium) intake during heat stress, suggest that lactating dairy cows may benefit from supplemental potassium 18 Increasing D.E.B. improves DMI lactating cows during heat stress and is probably mediated through improved acid-base chemistry of the cow.5

D.E.B. AND DAIRY CALVES • • •

Increasing Cation-Anion Balance stimulates dry matter intake and average daily live weight gain.21 Optimal D.E.B. (in the experiment) was 320 mEq/Kg DM.. This result agrees with many published reports on the value of buffering standard rations of beef calves in temperate zones.

In heat stress conditions higher D.E.B. values have been required for optimal gains

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HEAT STRESS IN DAIRY CATTLE THE APPLICATION OF RCI PRODUCTS

HEAT STRESS is the major cause of lost production in dairy cattle in hostile “production-limiting” regions.

The rationale behind RCI's Heat Stress Programme is based on the known physiology underlying bovine response to hostile climates

The zone of comfort for the cow is 4°C to 24°C. Cattle react to Heat Stress conditions by eating less food, thus naturally controlling the rise in deep body temperature caused by digestion. They also drink at least 5 times the amount of water they would under temperate conditions, urine output increases and many mineral ions are lost.

•

As a result Dietary Electrolyte Balance (D.E.B.) is altered. (D.E.B. is measured in mEq (milli-equivalents)).

•

Heat Stress increases the dietary needs for key electrolytes, Na+, K+ and HCO3-

•

In hostile conditions Lactating cows need D.E.B. levels as high as +550 mEq for optimum milk yield to compensate for the high rate of loss of ions.

.

•

On the other hand, dry cows need negative D.E.B. levels.

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Research has demonstrated that cows fed rations containing a D.E.B. of - 100 to -150 mEq in the month prior to calving have far less problems around calving time and better total milk yield over the subsequent milking.

The constant addition of Selectolyte through the drinking water restores lost ions and helps to preserve electrolyte balance. Drinking water medication is preferred because the cows will drink when they will not eat.

Anigane in the drinking water stimulates appetite and the central nervous system. This helps to increase the amount of food eaten resulting in increased milk output.

DEB++9, a feed supplement, adds key electrolytes, reduces free ammonia in the gut (which reduces toxicity), facilitates, restores and accelerates ion exchange, protects cells from osmotic stress and enzymes from structural change and assists in the stimulation of appetite.

Negalyte is a feed supplement, used in the month prior to calving. It reverses the D.E.B. of the normal diet and this alteration has been shown to reduce the incidence of milk fever and to reduce the risk factors for dystochia, retained foetal membranes, metritis and uterine prolapse.

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The products are registered for veterinary use in Australia. A Certificate of Free Sale is available if required.

Milkers: *ANIGANE

above 25ºC below 25ºC

*SELECTOLYTE DEB++9

1 litre/ 3000 litres of drinking water 1 litre/1500 litres of drinking water 4 Kg / 3000 litres of drinking water 20kg/tonne feed

*Continuously in the drinking water

1st Calf Heifers: ANIGANE SELECTOLYTE DEB++9

75 mL twice daily on concentrate ration 1 g/litre of drinking water 20kg/tonne feed

Weaner Calves: ANIGANE SELECTOLYTE

25 mL twice daily in milk 1 g/litre of all fluids taken

NEGALYTE ANIGANE SELECTOLYTE

0.5 Kg/head twice daily in the concentrate 60 mL sprinkled over the concentrate 2 g/litre of drinking water.

Dry Cows:

MILK IS NOT TAINTED BY THE USE OF THESE RCI PRODUCTS

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ADDITIONAL READING

1.

HEAT STRESS AND DAIRY CATTLE

2.

D.E.B. & DAIRY COW FEEDING

3.

RCI MANAGEMENT PROGRAM

4.

D.E.B - USEFUL FACTS

5.

ELECTROLYTE BIOLOGY

6.

IONS, ELECTROLYTES AND THEIR FUNCTION

7.

REFERENCES

8.

APPENDICES

Much remains to be clarified by ongoing research programmes and therefore adjustments and improvements to treatment and control regimes can be expected from time to time. You can visit our web site at www.rci.com.au where you will find the latest recommendations.

The information contained in this publication comes from the accumulated scientific literature of the last 20 years or so, although principally from recent years, and from the Company's extensive field experience in Australia, Asia and the Arabian Gulf countries

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1. HEAT STRESS AND DAIRY CATTLE

It is now accepted that HEAT STRESS is the major cause of lost production in dairy cattle in hostile “production-limiting” regions.

The Thermal Comfort Zone for dairy cattle is between 4°C and 25°C. The upper critical temperature limit remains constant regardless of age or lactation status.

When temperature exceeds 25°C cattle suffer heat stress. Cellular function in the cow operates optimally at 37°C (deep body temperature). In severe cases of heat stress the deep body temperature rises and production performance is reduced.The effect is increased when the relative humidity is greater than 50%. Some responses to heat stress are: • • • • • •

reduced feed intake reduced lactation performance decreased activity shade or wind seeking increased respiratory rate increased peripheral blood flow and sweating.

Cows capable of producing more milk are at greater risk from heat stress than lower yielding cows.

The immediate response to heat stress is reduced feed intake in an attempt to contain metabolic heat. Lactating cows under continuous heat stress begin to show a decline in intake at 25-27°C with a marked decline of 40% above 30°C. At 40°C intake is usually down by 60% .

Ruminal pH is typically lower in heat stressed cattle. Rates of gut and ruminal motility are reduced, thus slowing passage of feed through the digestive tract.

Lactating dairy cattle are particularly sensitive to heat stress. High environmental temperatures in the last trimester of pregnancy alter blood flow and maternal-foetal hormone concentrations, resulting in lower birth weight of calves and reduced milk yield in the subsequent lactation.

Heat stress dramatically lowers conception rates. The seasonal depression in reproductive performance is one of the most serious problems in the dairy industry in “production-limiting” environments throughout the world.

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The effects of heat stress on dietary electrolyte balance may be summarised as: • Appetite is depressed, there is some indigestibility of feed and gut motility is slowed.

• Milk Yield - at 35°C there is up to 33 % depression and at 40°C, as much as 50%.

• There is loss of milk quality - fat and protein content declines • There is loss of body weight • The incidence of milk fever increases.

• Metritis is more widespread • Uterine prolapse is more common • Mammary gland infections increase • There are increased uterine infections • Udder oedema is more severe • Laminitis is more frequent • Keto-acidosis is a recurring problem • Fertility is lowered - insemination success rate falls, embryo mortality increases • Calves are often premature and small • Growing animals have markedly reduced weight gains.

• Drinking water intake increases • Nutrient deficiencies occur in marginally adequate diets

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2. DIETARY ELECTROLYTE BALANCE (D.E.B.) AND DAIRY COW FEEDING

Any substance dissociating into ions produces a conducting solution. D.E.B. (dietary electrolyte balance) is concerned with the proportion of the specific fixed ions in the diet.

Dietary cations - positively charged - such as Na+ and K+ are alkalogenic while dietary anions - negatively charged such as Cl- and S= are acidogenic.

There are extended equations which include Ca++, Mg+ and P but for practical purposes the equation for calculating D.E.B. is ( Na+ +K+) - ( Cl - + S = )

Sulphur is not as important in cattle as in other species and is often omitted from this equation.

Feedstuffs are electrically neutral and the D.E.B. can be manipulated by adding combinations of these ions to the feed and water.

Required D.E.B. values of cattle diets vary with the physiological status of the cow, i.e. stage of lactation or pregnancy.

The D.E.B. has a direct impact on the blood acid-base metabolism. A negative value in cows approaching calving can prevent hypocalcaemia (milk fever ). This is due to increased calcium in the urine, increase in blood-ionised calcium and greater response to calcium balancing hormones. Paresis is reduced, reproductive performance is improved, calving disorders reduced and 305 day milk yield is greater. By influencing biochemical and transport processes severity of udder oedema is reduced.

Higher positive D.E.B. values in lactating dairy cows improves dry matter intake and increases milk production and quality. Laminitis and keto-acidosis are reduced with high positive values of D.E.B.

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3. RCI MANAGEMENT PROGRAM FOR CONTROL, PREVENTION AND TREATMENT OF PRODUCTION LOSSES DUE TO HEAT STRESS There are two key strategies in minimising the effects of heat stress in lactating cattle.

Animal husbandry program.

• Provide good shade and ventilation • Sprinkle cattle with water to help increase evaporative heat loss • Increase feeding frequency, offer fresh feed during cooler night-time hours.

• Provide abundant cool drinking water • Cool drinking water where possible, protect water lines and tanks from the sun • Increase feed protein to 20% early in lactation • Reduce chloride levels by 50% • Reduce roughage and increase nutrient density of feed.

Management of the D.E.B. Evaporative heat loss through sweating and panting is the primary mechanism for heat loss at high environmental temperatures. As a result of water loss from sweating at high temperatures thirst is increased, more urine is excreted and the huge waterflux resulting from increased water consumption also causes heavy loss of electrolytes. Potassium (K+ ) loss from the skin increases by 500% in unshaded cattle. In attempts to conserve K+, cows increase urinary excretion rates of sodium (Na+).

In severe heat there is panting respiration ( an important reaction in the effort to cool the body by evaporative cooling). The rapid loss of CO2 results in respiratory alkalosis. Cows compensate by increasing urinary output of HCO3-. Since the pH of blood is maintained in the range 7.3 - 7.5 by buffer systems based essentially on HCO3- constant replacement of this ion is critical to management of blood chemistry.

Thus heat stress increases dietary requirements for the key electrolytes, Na+, K+ and HCO3-.

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1. Lactating cows The program is based on water and feed medication using three products.

SELECTOLYTE DEB++9 ANIGANE

in the drinking water in the feed concentrate in the drinking water

which together supply • essential electrolytes to restore and maintain D.E.B. • ion-exchange enhancers to maximise balance and restore control of the composition, regulation and temperature of body fluids • Essential molecules methyl and chromium • Anti-diarrhetic action by control of protozoal and bacterial infections and the reduction of gastro-intestinal irritants such as free ammonia • Ionic stabilisers and osmo-protectants to reduce stresses on cell walls and intra-cellular enzymes • Appetite, and respiratory stimulants

Selectolyte is a balanced source of essential body salts and electrolytes. It replaces key electrolytes Sodium Na+, Potassium K+ and Bicarbonate HCO3- in body fluids without adding unhelpful Chloride ClSelectolyte is of special benefit to dairy cattle suffering from any condition of stress which increases body temperature, fluid intake and output and loss of electrolytes.

Directions for use: Selectolyte may be used in the drinking water, in feed or as a drench.

If adding to the drinking water always mix the required amount of Selectolyte with a small quantity of water first and stir thoroughly. Then add the resulting mixture to the water tanks and again stir thoroughly.

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Milkers 1st Calf Heifers Weaner Calves: Dry Cows

4 Kg / 3000 litres of drinking water 1 Kg/1000 litres of drinking water 1 g/ litre of all fluids taken 2 Kg/1000 litres of drinking water.

In feed

2.5 - 6 Kg per tonne.

As drench

10 g per 100 Kg body weight daily for 5 -7 days

DEB++9 is a unique feed supplement specifically designed for livestock raised in productionlimiting climates.

DEB++9 synergistically supports Selectolyte use in the drinking water to give an overall better direction of Dietary Electrolyte Balance. It also assists by: • • • • • • • • •

Promoting homeostasis (dietary electrolyte balance) Reducing free ammonia in the gut (reduces toxicity) Facilitating, restoring and accelerating ion exchange Supplying osmolytes (protects cells from osmotic stress and enzymes from structural change) Stimulating appetite Assisting the osmoregulation of body fluids, their composition, temperature, volume and distribution within the body Reducing stresses on cell walls and intra-cellular enzymes due to high temperature Reducing mortality Ensuring maximum skeletal development.

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Directions for use: Add 20Kg of DEB++9 to 1 tonne of concentrate feed and mix thoroughly Note:

• Climatic and animal comfort conditions are important.

• When calculating Dietary Electrolyte Balance, total dietary intake (TDI) from all sources, feed and water must be estimated.

Anigane overcomes lethargy, stimulates the appetite and invigorates the essential body systems. Animals continue to eat even at times when appetite and feed consumption would normally drop.

Anigane contains stimulants and appetisers. This helps increase the rate and depth of respiration and enhances the evaporative cooling effect.

Regular users of Anigane report greater resistance to stress from environmental, disease, temperature or management factors.

Directions for use: Anigane is best used continuously in the drinking water.

Milkers: 1st Calf Heifers Weaner Calves: Dry Cows

above 25ºC below 25ºC

1 litre/3000 litres of drinking water 1 litre/1500litres of drinking water 75 mL twice daily on concentrate ration 25 mL twice daily in milk 60 mL sprinkled over the concentrate

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2. Dry cows The target is to reduce the mEq value to -100 to -150 mEq/Kg DM of total diet.

Negalyte is a feed supplement used in the month prior to calving to reverse the D.E.B. in the normal diet. Negalyte assists in reducing the incidence of metabolic disorders such as milk fever. Introduced to the ration from the fourth week before calving Negalyte reduces the risk factors for dystochia, retained foetal membranes, metritis and uterine prolapse.

Directions for use: Introduce gradually to the concentrate portion of the ration during the fourth week before calving. Continue feeding up to calving. Do not feed beyond calving.

During this time remove all salt blocks from the cattle.

Use only mineral mixtures which supply Cobalt, Selenium, Zinc, Copper and Vitamin D3.

Reduce roughage component of the ration - Rhodes grass or alfalfa - from 3.5 to 2.5 Kg per head per day.

Appetite will be stimulated if 60 mL ANIGANE is sprinkled over the concentrate/Negalyte mixture.

Add SELECTOLYTE at the rate of 1 Kg per 500 litres of drinking water during the entire Negalyte feeding program.

Rate of use: Dose rate of 0.5 Kg per head twice daily with the concentrate.

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How To Calculate mEq Multiply % by 10,000 and divide by Molecular Weight (M.W.)

Molecular weights for the key electrolytes are Sodium 23 Potassium 39 Chlorine 35.5 Sulphur 32 (see page10 5) Examples of Hot Climate rations for Milkers #1 0.45% 1.00% 1.00%

Sodium Potassium Chlorine

#2 0.42% 1.43% 0.31%

Multiply % by 10,000 and divide by Molecular Weight (M.W.)

Sodium Potassium Chlorine

#1 4500 ÷ 23 = +195 10,000 ÷39 = +256 10,000 ÷35.5 = -282

#2 4200 ÷ 23 = +183 14,300 ÷ 39 = +409 3100 ÷ 35.5 = -87

= +169mEq/Kg

= +505mEq/Kg

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4. DIETARY ELECTROLYTE BALANCE (D.E.B.) USEFUL FACTS 1.

Minerals are a more integral part of all biological functions in the animal than any other nutrient. These functions include: • • • • • •

2.

Expression and regulation of genes Enzyme systems within cells Osmotic balance Detoxification Acid-Base Balance and Structural tissues eg. bone.

Sodium, Potassium, Chlorine, Sulphur and Bicarbonate form ions. According to their electrical charge ions are either Anions ( +) (positive) or Cations ( - ) (negative) This equation articulates the importance of Dietary Cation Anion Balance ( D.C.A.B.) more popularly known as Dietary Electrolyte Balance ( D.E.B. )

( Na+ +K+) - ( Cl - + S = ) Managing the balance of dietary electrolytes is a key factor in maximising production in production-limiting environments.

Higher values, 300 - 500 mEq/Kg of TDI (total dietary intake) during lactation result in improved dry matter intake and milk production.

The manipulation of D.E.B. must be carefully controlled.

• Optimal mEq range is around 350 - 550 for most lactating cows under heat stress conditions Negative values such as -100 to -150 mEq/Kg TDI in cows approaching calving prevent milk fever, reduce paresis ( temporary paralysis) and improve overall production. They also influence the incidence of udder oedema.

• Target mEq range for dry cows in the month prior to calving is -100 to -150 mEq. Many enterprises are feeding rations similar to those for lactating cattle. Recent work clearly shows the correct strategy is to reduce mEq levels in the month prior to calving, during the "traditional steaming" up period.

This is achieved by adding an Anionic Supplement such as NEGALYTE

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3.

Acid - Base Balance Maintenance of acid-base equilibrium is fundamental to life. Enzyme systems, metabolic functions and performance measures depend on this equilibrium. The pH of blood is maintained in the range 7.3 - 7.5 by buffer systems based essentially on HCO3( bicarbonate ion). Panting respiration is an important reaction in the effort to cool the body by evaporative cooling through loss of water from the lungs. This results in metabolic alkalosis due to rapid loss of CO2 , and the cow compensates by increasing output of HCO3- in the urine. Thirst is increased, more urine is excreted and with it key electrolytes. Constant replacement of Sodium, Potassium and Bicarbonate is required.

4.

When cows are not shaded during the heat of the day the potassium ( K+ ) loss from the skin increases by 500%. Cows increase urinary excretion of Sodium in an attempt to conserve Potassium in the kidney. This loss of Potassium from the skin and Sodium in the urine together with a lowered intake of dry matter during heat stress reduce D.E.B. levels.

5.

Increasing D.E.B. values of the TDI (Total Dietary Intake) by supplementation of Sodium and Potassium improves average daily weight gain of calves. This is particularly so in Heat Stress conditions.

6.

Water is the most important nutrient for lactating dairy cows. Heat stress increases water consumption by at least five times the normal level in temperate zones.

7.

Exposure to heat stress for long periods suppresses the responsiveness of the immune system. Increased levels of corticosteroids in the blood reduce the activity and population of lymphocytes in the blood.

8.

The practice of premilking cows before calving to reduce the effects of udder oedema produces a severe drop in immunoglobin and the colostrum immediately after parturition. This can influence the susceptibility of suckling or dependent calves to intercurrent diseases which may be fatal. The control of udder oedema by manipulation of D.E.B. offers many benefits and avoids many current management practices.

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5. ELECTROLYTE BIOLOGY Scientific research has now demonstrated that the balance between Anions and Cations has fundamental effects on the performance of all animal species.

This effect is quite separate from the importance of the individual mineral ions in the diet. Ions generate acid or base according to metabolic reactions in which they are involved.

There are between species differences and these differences appear to differ according to the physiological phase of the animal. These phenomena are widespread throughout the animal kingdom and reflect their fundamental importance in production.

The combined effects of high environmental temperatures and high relative humidities on D.E.B. balance is not researched judging by the paucity of references in the literature.

As we noted in the Overview, the balance is especially vulnerable in Production-Limiting Environments.

It is the disturbance of D.E.B. balance which results in the major production losses associated with Heat Stress.

Each species, according to its evaluation, has a ‘Zone of Comfort' in which it performs most efficiently. For dairy cattle the range is from 40C to 250 C. KEY COMPONENTS OF ELECTROLYTE BIOLOGY Cell Membranes Cell Membranes are very complex in their structure and are selectively permeable.

All the processes of life are carried out within the cells. Oxygen and nutrients are allowed to enter and waste products are excreted.

Evolution from the earliest forms of life has meant that a high degree of cell specialisation has occurred. There are many kinds of cells, some simple and many highly complex in the structure of their walls (membranes) and in their contents.

The living cell changes in response to the balance and mix of substances within the cell.

Sodium/Potassium Pump The function of the Sodium Potassium pump is an example of how delicately the processes of life are adjusted and balanced.

Some substances are carried across membranes by proteins embedded in the cell wall. Often there is an accumulation of a molecule outside or inside a cell. These substances do not move by passive transport, work must be done; eg. "pushing a load uphill" and therefore energy is expended. This is active transport.

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Many cells have Sodium/Potassium exchange pumps. These are in cell walls and exchange Na+ for K+ ions. The energy is derived from Adenosine triphosphate (ATP) a high energy molecule. For each molecule of ATP used up, three ions of Na+ are pumped out of the cell and two K+ ions are pumped inwards. This system keeps the necessary higher concentration of K+ inside and a higher concentration of Na+ outside the cell. Low Potassium reduces the cell's capacity to retain water and the ability to dissipate heat is seriously reduced.

Active transport of this type is a basic function of all cell membranes in the body.

Osmoregulation is another process of life through which an animal controls its body-fluid and mineral-ion balances.

It is generally said that two thirds of the animal body (cells and fluids) consists of water.

However, the amount of intracellular water is critical as are the various ions within the cells.

The balance of water and ions is maintained by the removal of waste products from metabolism within the cells.

Filtering and excretion in the kidney cells involves active transport. This maintains osmotic conditions and acid-base balances in the blood. Variations in osmotic pressures influence the secretion of hormones from glands throughout the body.

Membrane pumps, Ions and nerve impulses The nerve cell membranes are studded with Sodium/Potassium ion exchange pumps which are complexes of enzymes. Shifting the Sodium ions out of the cell and Potassium ions into it creates concentration gradients and these are the source of potential energy which the nerve cell can use to transmit impulses to the brain or to muscles.

Ions, Enzymes and the Expression and Regulation of Genes Heat can initiate chemical reactions but may affect the functions of enzyme systems. Mineral Balance has a fundamental influence on enzyme functions. pH can influence enzyme action within the cells and most enzymes require a neutral pH7 condition. Changes in the acidity within cells may even reverse the action of enzymes.

Any one enzyme reaction is usually one in a long chain of reactions, all of which are required to keep the cell viable and productive.

Genes are expressed and regulated by enzyme action and have an important role determining the efficiency of the immune system.

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6. IONS, ELECTROLYTES AND THEIR FUNCTION The principle elements and their ions (electrolytes) involved are Sodium, Potassium, Chlorine and Bicarbonate.

Sodium • • • • • • • • • • • • • •

• •

2% of body weight; 70% is in the exchangeable pool.

Has a very active metabolism.

90% of dietary Sodium is absorbed.

Occurs only at low levels in corn and soya bean meal.

Is extracellular in distribution.

Involved in control of blood viscosity and water regulation.

Controls the volume of extracellular fluids.

Participates in the vital energy reaction Na-K-ATPase-Glucose.

Involved in electrical potential and the physics of electrical pulses along nerves, neuromuscular function and muscle contractions.

Works with Calcium, Magnesium and Potassium.

Is an enzyme activator.

The regulation of body Sodium has a high priority.

The kidney is the key to Sodium homeostasis.

Conditions in which Sodium is lost to the body are: - diarrhoea and vomiting - excessive sweating - some types of kidney damage - insufficiency of the cortex of the adrenal glands - heat stress Plants do not usually contain sufficient Sodium for the body's needs.

Salt has been considered an essential addition to foodstuffs long before it was understood that Salt = Sodium + Chlorine.

Potassium • • • • • • • • •

Na+

K+

Approximately 2% of body weight.

Is intracellular in distribution.

Participates in the vital reaction Na-K-ATPase-Glucose.

Is a co-factor, activating enzymes.

Involved in the physics and chemistry of electrical pulses.

Concerned with Acid-Base balance. Acidosis shifts K+ from intra to extra cellular.

Alkalosis reverses this shift.

Has a part to play in cardiac function.

Vital for protein synthesis within cells.

K+ homeostasis is maintained by the kidney.

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Chlorine • • • • • • • •

Is stored in the skin and subcutaneous tissues.

Occurs extra and intracellularly.

Provides about 65% of the total anions in extracellular spaces.

Component of Hydrochloric Acid (HCl) vital for digestion.

Acid-Base balance which is critical to the survival of any animal system is easily disturbed by too little or too much Cl-.

Involved in muscle physiology The "chloride shift" in red blood cells assists the movement of Carbon Dioxide (CO2) from cells to the lung.

Low levels occur in corn and soy bean meal, high levels in fish, meat and bone meals

Bicarbonate • • • • • •

Cl-

HCO3-

Plays an important role in the transport of Carbon Dioxide (CO2) in the blood.

It is an important buffer neutralising acids produced during metabolism.

When H2CO3 (Carbonic Acid) dissociates into H+ + HCO3-, the H+ ions are buffered by haemoglobin in the red blood cells and the HCO3- diffuses out into the plasma joining Na+ ions to give Na2CO3 Some of the effect of H2CO3 is independent of pH control. There is a dietary as well as physiological requirement for this anion.

HCO3- is substituted for Cl- in the kidney and thus spares Cl-.

HCO3- , Lactate and Acetate are metabolisable anions which work towards maintaining electroneutrality by balancing mineral cations eg. Na+, K+, Mg++

Electrolytes in feedstuffs are not absorbed with equal or consistent efficiency. Dietary analysis may therefore be misleading Strong electrolytes dissociate completely and weak ones partially. Strong electrolytes include HCl, NaCl, Na OH, KFl. Weak ones include HFl, NH3, HgCl2, Acetic Acid Unabsorbed minerals may have an effect and there may be interactions between mineral fractions in the gut and after absorption into the bloodstream.

Cell activity requires electrical energy. When electrolytes are added water is a good conductor of electricity

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Water • • • • • • • • • • • • • • •

H2O

As long ago as 400 million years life moved from water to dry land. Skin evolved to provide a barrier between cell contents and surrounding air.

In the process cells of organisms became highly specialised and developed micro-element and enzyme systems which allowed them to regulate the fluids (largely water) within their cell walls.

These cellular systems depend upon electrolytes for their viability. They perform most efficiently at 37 ° C Mechanisms developed to regulate the composition of fluids within the cells and of fluids surrounding the cells.

Water has a high heat capacity and is therefore critical to homeostasis It has a very low viscosity.

It has a high surface tension.

It is distributed 60% intracellularly and 40% extracellularly.

It is a lubricant.

Water transports nutrients, gases, waste products and hormones and is central to Acid Base balance.

It provides the medium in which reactions take place.

It plays a part in heat dissipation Water facilitates the movement of digesta along the gastrointestinal tract and plays a key role in the absorption of nutrients across the gut wall.

Urine is the primary route of elimination of water.

Sweat and respiration are involved in maintaining water balance and achieving homeostasis

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7. REFERENCES I Ia Ib

lc

2 2a 3

3a

4

4a

5 5a

6

6a

7 7a

7b

Mongin, P. 1980. Electrolytes in nutrition. Page 1 Proc. 3rd Ann Intl. Minerals Conf. Orlando, Fla. Feedstuffs May 10 1993. Joe West, at Southwest Nutrition and Management Conference in Phoenix, Arizona.

Tucker, W.B., J.F. Hogue, G.D. Adams, M. Aslam, I.S. Shin and G. Morgan.

1992. Influence of dietary cation-anion balance during the dry period on the occurrence of parturient paresis in cows fed excess calcium. J. Anim. Sci. 70: 1238 Block, E. 1994. Manipulation of dietary cation-anion difference on nutritionally related diseases, productivity, and metabolic responses of dairy cows. J. Dairy Sci., 77:1437.

Dennis, R. J. and R.W. Hemken. 1978. Potassium requirement of dairy cows in early and mid lactation. J. Dairy Sci., 61:757.

West, J.W., B.G. Mullinix and T.G. Sandifer. 1991. Changing dietary electrolyte balance for dairy cows in cool and hot environments. J. Dairy Sci. 74:1662.

Devlin, T.J., W.K. Roberts and V.V.E. St Omer, 1969. Effects of dietary potassium upon growth, serum electrolytes and intrarumen environment of finishing beef steers. J.Anim. Sci., 28:557.

Escobosa, A., C.E. Coppock, L.D. Rowe, Jr., W.L. Jenkins and C.E. Gates, 1984.

Effects of dietary sodium bicarbonate and calcium chloride on physiological responses of lactating dairy cows in hot weather. J. DAIRY Sci. 67:574.

Hutcheson, D.P. N.A. Cole and J.B. McLaren. 1978. Potassium addition to receiving diets of transported feeder calves. Prod. West. Sect. Am. Soc. Anim.

Sci., 45:1426 Tucker, W.B., G.A. Harrison and R.W. Hemken. 1988. Influence of dietary cation-anion balance on milk, blood, urine and rumen fluid in lactating dairy cattle. J. Dairy Sci. 71:346.

Munson, R.D., editor. 1985. Potassium in agriculture. Am. Soc. Agron., Crop Sci/ Soc. Amer., Soil Sci. Soc. Amer., Publishers. Madison, Wis. West, K.W., K.D. Haydon, B.G. Mullinix and T.G. Sandifer. 1992. Dietary cation-anion balance and cation source effects on production and acid base status of heat-stressed cows. J. Dairy Sci. 75:2776.

Preston, R.L. and J.R. Linsner. 1985. Potassium in animal nutrition., R.D. Munson, editor, pg.595-617. Am. Soc. Agron., Crop Sci. Soc. Amer., Soil Sci Soc. Amer., Publishers, Madison Wis. Schneider, L.L., D.K. Beede and C.J. Wilcox. 1986. Responses of lactating cows to dietary sodium source and quantity and potassium quantity during heat stress.

J. Dairy Sci. 69:99.

Oetzel, G.R. 1991. Meta-analysis of nutritional risk factors for milk fever in dairy cattle. J. Dairy Sci., 74:3900.

Sanchez, W.K., D.K. Beede and M.A. DeLorenzo. 1992. Modelling the effects of macrominerals on lactational performance of dairy cattle. Proc. Natl. Feed Ingred.

Assoc. Nutr. Inst. Chicago. Ill. Sanchez, W.K., D.K. Beede and J.A. Cornell. 1994. Interactions of sodium, potassium and chloride on lactation, acid-base status and mineral concentrations.

J. Dairy Sci., 77:1661.

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8 9

9a

10 10a 11 12 13

14 15

16 17 18

19 20

21

National Research Council. 1989. Nutrient requirements of dairy cattle. 6th rev. ed. Natl. Acad. Sci., Washington, D.C. Sanchez, W.K., M.A. McGuire and D.L. Beede. 1994. Macromineral nutrition by heat stress interactions in dairy cattle: Review and original research. J. Dairy Sci.,77:2051.

Grohn, Y.T., II.N. Erb, C.E. McCulloch and H S. Saloniemi. 1990. Epidemiology of reproductive disorders in dairy cattle: Associations among host characteristics, disease and production. Prev. Vet Med. 8:25.

Telle, P.I., R.L. Preston, L.D. Kintner and W.H. Pfander, 1964. Definition of the ovine potassium requirement. J.Anim Sci., 23:59.

Risco, C.A., J.P. Reynolds and D. Hird. 1984. Uterine prolapse and hypocalcaemia in dairy cows. J.Am. Vet. Med. Assoc. 185:1517.

Dishington, I.W. 1975. Prevention of milk fever (hypocalcemic paresis puerperalis) by dietary salt supplements. Acta Vet. Scand. 16:503.

Block, E. 1984. Manipulating dietary anions and cations for prepartum dairy cows to reduce incidence of milk fever. J. Dairy Sci. 67:2939.

Beede, D.K., C.A. Risco, G.A. Donovan, C. Wang, L.F. Archbald and W.K. Sanchez. 1991. Nutritional management of the late pregnant dry cow with particular reference to dietary cation-anion difference and calcium supplementation. Proc. 24th Ann. Conv. Am. Bovine Pract., Orlando, Fla. Oetzel, G.R. and J.A. Barmore. 1992. Palatability of anionic salts fed in a concentrate mix. J. Dairy Sci. 75(Supp.1):297.

Tucker, W.B., J.F. Hogue, D.F. Waterman, T.S. Swenson, Z. Xin, R.W. Hemken, J.A. Jackson, G.D. Adams and L.J. Spicer. 1991. Role of sulfur and chloride in the dietary cation-anion balance equation for lactating dairy cattle. J. Anim. Sci. 69:1205.

Huber, T.L., R.C. Wilson, A.J. Stattelman and D.D. Goetsch. 1981. Effect of hypocalcaemia on motility of the ruminant stomach. Am. J. Vet. Res. 42:1488.

Oetzel, G.R. 1991. Meta-analysis of nutritional risk factors for milk fever in dairy cattle. J. Dairy Sci. 74:3900.

Malunee, Beede, Collier, Wilcox. Production and Physiological Responses of Dairy Cows to varying Dietary Potassium during heat stress. J Dairy Sci 68: 14791487.

Harris, B. Feeding to combat heat stress. Feed International. July 1992.

Lema, W.B. Tucker,M. Aslam, A. Shin, LeRuyet, G.D. Adams Influence of CaCl2 fed prepartum on severity of oedema and lactational performance in dairy heifers.. J Dairy Sci. 75:2388-2393.

Jackson, J.A., Hopkins. Z.Xin, R.W.Hemken Influence of Cation-Anion Balance on feed intake body weight gain and humoral response in dairy calves.. J Dairy Sc. 75:1281-1286.

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8. APPENDICES

Heat Stress and Drinking Water Temperature •

Chilled water reduces heat stress but the effect is only temporary - about 2 ¼ hours.

Used strategically this may assist cows to maintain their temperature below thermoneutrality.19

Partition of heat dissipation between evaporative and non-evaporative cooling as influenced by environmental temperature. 1

Temperature (C°)

(F°)

0 10 20 30 38

32 50 68 86 100

Non-evaporative

Total

Evaporative Surface

Respiratory

(% partition) 78 72 58 25 3

22 28 42 75 97

14 18 30 57 77

8 10 12 18 22

The actual cooling effect of water at 55°F (13°C)can be 20% of the basal heat production. On the other hand, water at environmental temperature would cool less than half this amount.

Chilled drinking water experiments with dairy cows fully support the above concept.

Studies at Texas showed milk yield increases of more than 10% by allowing cows an afternoon consumption of 50°F (10°C) water rather than 82°F (28°C). At the same time feed intake for the chilled water group increased by 13%.18 Effect of water at two temperatures on the amount of heat removed Cooling effect* Water (F°) (C °) 55 7 85 29

(Kcal/hr) 123 52

% Heat Production** 20 8

Based on heat used to warm 30 gal of consumed water to body temperature. **Based on heat production of 625 Kcal/hr.18 Cation and anion support is required because of the large water flux associated with the heat stressed condition. 18

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