19 minute read
Leaves and LEAF
Let LEAF be your guide to alfalfa leaves
by David Weakley and Charlie Rodgers
Advertisement
HOW often have you harvested a beautiful field of alfalfa or a newly established stand of a high-quality variety of alfalfa, only to find out later that the lab test results were only average?
Rather than assuming you received inaccurate lab test results or did not obtain the promised benefits from the high-quality alfalfa variety, perhaps the lower than expected lab test was the result of leaf loss.
Leaf loss is one of the major factors negatively impacting harvested alfalfa forage quality. University of Wisconsin research has shown that leaf percentage accounts for 71% of the variation in forage quality. Leaves have a relative forage quality (RFQ) of approximately 550, while stems have an RFQ of only 70 to 80. Therefore, growers must know the percent of leaves in their alfalfa to better manage growing, harvesting, and evaluating their alfalfa.
While there are many forage quality measurements we can perform on alfalfa, until now there has been no reliable rapid test to predict the amount of leaves in a sample of alfalfa that is typically dried, ground, and analyzed in a lab. Researchers at Forage Genetics International (FGI) decided to develop such a test.
LEAF development
During the summer of 2019, 160 samples of standing alfalfa plants were collected from FGI research plots at West Salem, Wis.; Nampa, Idaho; and Davis, Calif. Across all locations, a total of 43 varieties of alfalfa were harvested similarly using a variety of cutting schedules (28, 33, 35, or 38 days) across a range of cuttings (first through third).
Plants were sent to West Salem where they were dried at a temperature less than 140°F, followed by hand separation and weighing of leaf and stem fractions. After recording the weights, the two fractions were recombined and ground over a 1-millimeter (mm) screen. From there, they were forwarded to the FGI in vitro digestibility lab at Gray Summit, Mo., for Calibrate High Quality (HQ) Forage Analysis testing. This included near infrared reflectance spectroscopy (NIRS) and “wet” lab analysis for dry matter (DM), ash, crude protein, neutral detergent fiber (NDF), and 28-hour in vitro NDF digestibility (NDFd28).
These values were then compared with the percent leaf fraction in each sample in a stepwise regression analysis approach to develop an equation to predict percent leaves from the best-fit component models.
During the following year (2020), 40 new whole plant samples were collected from the Davis and West Salem research locations using similar methods to the previous year. Those samples were run through the same protocol to be used to validate the accuracy of the percent leaf prediction equation developed in 2019.
A robust equation
The findings from the 2020 validation set of 40 samples showed that the standard error of the prediction was extremely low (2.86 percentage units of leaves) across a wide range of 35% to 64% leaves in the samples. This indicated that the leaf prediction equation can be “off” by an average of only 2.86 percentage units of leaves on a given sample.
These 40 samples were added to the original 160 samples and a new prediction equation, LEAF (Leaves Enhance Alfalfa Forage), was developed that predicts percent leaves in alfalfa from NDF, protein, and NDFD28 measured in the sample. This equation explained 84% of the variation in leaf percentage in these samples (see Figure 1).
The samples in the calibration dataset represented a wide range in quality, spanning 21% to 48% NDF, 16% to 31% crude protein, and 37% to 60% NDFD28. The measured leaf percentage ranged from 35% to 70%, with an average of 52% (standard deviation [SD] of 8.6%).
What is typical?
The LEAF equation was used to predict the leaf percentage of 360 samples of alfalfa that were collected during 2019 from across the U.S. and analyzed by FGI. The samples represented a wide range in quality, from 16% to 67% NDF, 8% to 30% crude protein, and 34% to 62% NDFD28. The predicted leaf percentage ranged from 10% to 77%, with an average of 48% (SD of 12.6%; Figure 2). Across both sets of data, the average leaf percentage in alfalfa was approximately 50%, with a SD close to 10%. Therefore, two-thirds of the sample population had a leaf percentage between 40% and 60%, which could be considered a “typical” range.
With this in mind, we went a step further and compared the relationship between RFQ and LEAF percent in the 360 samples from 2019. As can be seen in Figure 3, leaves influenced RFQ in a positive manner with a strong relationship. The equation from this relationship was then used to predict the RFQ at various levels of LEAF percent in alfalfa around the average of 50%, which was obtained from the two datasets (Figure 3).
The graph shows the increasing return in RFQ value that can be gained from improving retention of leaves during growing and harvesting of alfalfa. The other discovery is that over the range between 40% and 60% leaves, each 1 percentage unit improvement in leaves resulted in a 4.6-unit bump in RFQ.
What this indicates is that it takes only a little more than 2% additional
DAVID WEAKLEY AND CHARLIE RODGERS
Weakley (pictured) is the director of dairy forage nutrition for Forage Genetics International (FGI) in West Salem, Wis. Rodgers is a senior alfalfa breeder with FGI.
leaves to raise the RFQ of a bale of alfalfa by 10 units. This emphasizes the importance that leaves play in the quality of alfalfa forage and why it is worth spending the extra effort to not lose leaves from the field to the mouth of a ruminant animal.
The following is just a brief listing of factors affecting leaf loss in alfalfa: • Fungal and other alfalfa diseases • Mower-conditioner type and settings • Rake type, excessive raking, or raking when the alfalfa is less than 40% moisture • Baler type and settings • Grinding or excessive mixing of hay before feeding
Using LEAF
Use the LEAF percent value to identify and measure a major source of quality variation in alfalfa. This will result in a more objective conversation when discussing alfalfa sample quality test results. • If the protein and NDF digestibility are lower than expected, and the NDF is higher than expected, check for leaf loss as the cause. • If the LEAF percentage is less than 45%, evaluate areas for alfalfa management improvement. • Consider options such as fungicide application, using more disease or pest-resistant alfalfa varieties, and don’t forget the many harvest management improvements that can be put into action.
The LEAF test has not been validated with alfalfa-grass mixed forages and is currently intended only for pure stands of alfalfa. Furthermore, the LEAF test has only been validated against nutrient inputs from the Calibrate High Quality Forage Analysis Test. Lab variation in these nutrient input measurements from other forage tests could likely affect the accuracy of the percent leaf predictions if they were used as replacement values in the LEAF test.
Currently, the LEAF test is available as part of the Calibrate High Quality Forage Analysis results from Winfield United’s SureTech Laboratories. However, the goal is to make the LEAF test available to all labs providing the Calibrate High Quality Forage Analysis test, now that a year-long field evaluation of the LEAF test has been completed. For more information, contact BDHodne@foragegenetics.com. • Figure 1. Relationship between predicted and measured percent leaves
Measured 75 70 65 60 55 50 45 40 35 30 R2 = 0.84
30 35 40 45 50 55 60 65 70 75
Predicted
Figure 2. Approximate average leaf percent in alfalfa
Number of samples 80
70
60
Average: 48% Std. Dev. 12.6 68
61
50
40
30 31 40 45
39
20 21
10
0 11 3 5 11 11 13 11
Figure 3. Influence of percent leaves on RFQ
RFQ 500 450 400 350 300 250 200 150 100 50 0
% leaves 40 45 50 55 60 RFQ 132 150 172 196 224
R2 = 0.8788
0.0 10 20 30 40 50 60 70 80
Extreme processing boosts feed value
Hay & Forage Grower is featuring results of research projects funded through the Alfalfa Checkoff, officially named the U.S. Alfalfa Farmer Research Initiative, administered by National Alfalfa & Forage Alliance (NAFA). The checkoff program facilitates farmer-funded research.
THE first research trial using “extreme” mechanical processing on wilted alfalfa after chopping is showing great promise in improving alfalfa fiber digestion – and, ultimately, could help dairy farmers save on feed costs.
“Nutritionists have told us that fiber digestion is the next frontier in dairy nutrition. If that’s the case, we think we might have something that might help; we can mechanically manipulate alfalfa and improve its fiber digestion,” said Kevin Shinners, University of Wisconsin (UW) agricultural engineer. Shinners and his colleagues received Alfalfa Checkoff funding to test whether extreme mechanical processing could break down alfalfa plant cells and enhance plant surface area so cows could more readily digest fiber.
Two identical diets consisting of 30% alfalfa haylage, 30% corn silage, and 40% concentrates were fed to 36 lactating dairy cows during a six-week period. The only difference between diets? One was conventionally chopped at a 10 millimeter (mm) theoretical-length-of-cut (TLOC), and the other was conventionally chopped at a 22 mm TLOC, then mechanically processed.
The mechanical processing was done on a modified screenless hammermill that provided processing by impact and shredding. Prior research has shown the combination of impact processing and shredding provided the desired physical results to the alfalfa. The crop was processed through the altered equipment to obtain a processing level that previous research had shown would likely boost fiber digestion.
This initial research’s main goal was to determine if mechanical processing could enhance alfalfa’s feed value, Shinners said. It will likely take time and additional development work before it reaches commercialization, he added. Many questions, including how and when mechanical processing should be done, still need answers. The agricultural engineer envisions processing could be incorporated on the forage harvester during harvest or as the crop is removed from storage and prior to mixing in the TMR.
“We need to find the best mechanical approach to achieve the desired processing level while requiring the least amount of energy,” Shinners said. “This process is going to take significant energy; we can’t break that stem down and fiberize it without putting substantial energy to it. But our initial economic analysis indicates that the benefit we get will more than pay for the extra fuel and power that we believe this is going to take. Hopefully, this will make alfalfa a more competitive feed.” KEVIN SHINNERS Funding: $78,068
Shows promise
The feeding trial showed the mechanical processing (MP) diet was more efficient than the conventional (CON) diet. Cows fed the MP diet consumed less feed than those on the CON diet, with a dry matter intake (DMI) of 60 (MP) compared to 62 (CON) pounds per day. Milk yield was nearly the same (103 [MP] compared to 102 [CON] pounds per day), but milkfat percentage was greater for cows on the MP diet as compared to those on the CON diet (3.94% compared to 3.81% fat). Fat-corrected
MECHANICALLY PROCESSED haylage, right, is shredded and stems are fiberized, said Kevin Shinners. Conventionally chopped material is at left.
PROJECT RESULTS
1. An impact-shredding processor was developed that produced a processing level index of 74% compared to only 38% for the control chopped material. 2. More than 35 tons of wilted alfalfa were processed and successfully conserved for the lactation feeding trial. 3. Dairy cows fed a diet of processed alfalfa produced 3.1 pounds per day greater fatcorrected milk while consuming less dry matter, improving feed efficiency. 4. Income over feed costs was greater for the extreme mechanical processing diet even though the cost to harvest alfalfa haylage was 1.25 to 1.40 times greater than that for conventionally harvested material.
milk (FCM) was also greater for cows fed the MP crop (102 compared to 99 pounds per day), making feed conversion efficiency (FCM/DMI) greater for MP-diet cows than for CON-diet cows (1.69 compared to 1.60).
Future research, said Shinners, may include looking at different crop maturities. “We think we could get a better response if we go with a crop that’s a little more mature than the crop harvested for the feeding trial. What would this process look like when we harvest at a greater maturity or at different moisture contents? Or, what if we set this material not at 30% of the cow’s ration, but at 40% or more?” he asked rhetorically.
“The NAFA funding was excellent seed money and gives us the opportunity to try to sell the USDA on our research. Hopefully, the USDA will invest funding and move this forward,” he said.
Shinners credits David Pintens, an agricultural engineering graduate student, for his outstanding work on the project, despite limitations caused by the pandemic. Others involved in the research included UW agricultural engineers Matthew Digman and Joshua Friede, as well as Kenneth Kalscheur, U.S. Dairy Forage Research Center animal scientist. To view the project final report, visit alfalfa.org. •
SUPPORT THE ALFALFA CHECKOFF!
Buy your seed from these facilitating marketers:
Alfalfa Partners - S&W Alforex Seeds America’s Alfalfa Channel CROPLAN DEKALB Dyna-Gro Fontanelle Hybrids Forage First FS Brand Alfalfa Gold Country Seed Hubner Seed Jung Seed Genetics Kruger Seeds Latham Hi-Tech Seeds Legacy Seeds Lewis Hybrids NEXGROW Pioneer Prairie Creek Seed Rea Hybrids Innvictis Seed Solutions Specialty Stewart Stone Seed W-L Alfalfas
IT’S TIME TO SIMPLIFY YOUR IRRIGATION PROCESS LIKE NO OTHER.
‹ Jim Felton Ashland, MT
Owner after owner can talk about their experience, but one thing stands out with everyone of them … they all own and operate the most reliable, simple to operate center pivot system on the market today.
T-Ls are simple to operate, easy to repair, and deliver the best water pattern which plays big when you are incorporating fertilizer.
EVERY PRODUCER HAS A STORY
Listen to Jim Felton’s story and what other T-L owners are saying at: › bit.ly/2QHLMaq
Contact T-L, your T-L dealer, or visit www.tlirr.com to learn more.
T-L … LIKE NO OTHER.
www.tlirr.com
151 East Hwy 6 & AB Road P.O. Box 1047 Hastings, Nebraska 68902-1047 USA sales@tlirr.com · www.tlirr.com Phone: 1-800-330-4264 Fax: 1-800-330-4268 Phone: (402) 462-4128 Fax: (402) 462-4617
CERTIFIEDISO QUALITY9001
Figure 1. Start of net wrap ball being removed from a cow through the rumen cannula. Approximately 25% of the ball is outside the animal.
Net wrap accumulates in cows fed ground hay
by Adele Harty
PLASTIC net wrap is a common binding material for large round hay bales, but it can present health challenges for cattle due to buildup in the rumen. Net wrapped bales are commonly used for winter feed sources in chopped or ground feed, but the net wrap is rarely removed prior to grinding, resulting in the hay containing pieces of plastic that are then fed to livestock.
Cattle producers have observed cows with diarrhea that lose weight over a relatively short period of time exhibiting symptoms similar to Johne’s or hardware disease. No veterinary treatments have been effective, and when animals were posted following death, a wad of net wrap and digesta was removed from the rumen. This buildup of plastic net wrap has been termed “plastic,” “net wrap,” or “software” disease.
Prompted by the evaluation of research findings at North Dakota State University regarding the digestibility of multiple hay binding materials, results from a Montana study indicated a significant amount of net wrap recovered in the digestive tract of cows postharvest. A project was later conducted at South Dakota State University Cottonwood Field Station to quantify how rapidly net wrap builds up and how it behaves in the rumen.
In order to quantify net wrap buildup, six ruminally cannulated Angus cows were fed a diet of ground hay without net-wrap removal. To determine whether existing net wrap in the rumen would “catch” other pieces of net wrap as they were ingested, a small piece of net wrap (4.7 inches by 4.7 inches) was placed in the rumen of three of the cows on Day 1, while the other three cows did not have any net wrap at the start of the study.
Fed for 140 days
To maintain weight and body condition, the cows were individually fed grass hay that contained 88% dry matter, 12.5% crude protein, and 60% total digestible nutrients over the 140-day feeding period, which represents a typical winter feeding duration in South Dakota. The bales had 1.5 wraps of Pritchett Net Wrap Green per bale, and hay was ground through a 5-inch screen.
To quantify the approximate amount of net wrap fed to the cows, the hay binding was removed from 18 bales from the same lot of hay, and those bales were not ground. All loose hay was removed from the net wrap, and the clean net wrap was weighed to determine the approximate amount of net wrap delivered to each cow throughout the feeding period. The total amount of net wrap offered during the period was estimated at 1.78 pounds per head.
Due to the better quality of the hay and the body condition score (BCS) of the cows at the beginning of the study, cows were limit fed at 74% of predicted intake to maintain weight and BCS. Cows had a BCS greater than 6 at
ADELE HARTY
The author is a cow/calf field specialist with South Dakota State University Extension.
Figure 2. Net wrap after removal from the rumen. Net wrap and feed entangled was approximately 3 feet in length when laid out flat. Figure 3. Net wrap ball with placental tissue wound up in it that was found in a cow that had recently calved.
the start of the study. Adjustments to intake were made as needed to maintain weight and BCS on an individual animal basis.
Four of the cannulated cows were pregnant and calved in March, prior to the end of the 140-day feeding period. Intake was adjusted for the higher nutrient requirements during lactation. On Days 139 and 140, three cows per day were weighed, scored for body condition, and their rumens were evacuated to remove the accumulated net wrap. All net wrap was removed, and the clean digesta was placed back into the rumen of each cow.
Photos were taken of the balls of net wrap that were removed from the cows to document the characteristics of the mass of net wrap and digesta (Figures 1, 2, and 3). Net wrap removed from each cow was dried and weighed to quantify the amount of net wrap in the rumen. To determine the rumen volume displaced by the net wrap, the net wrap collected from each cow was placed in a plastic bag and then submerged in a tub of water to determine the volume of water displaced by the net wrap.
Softball-sized
In all cows, most of the net wrap was tangled together in one ball of material (Figures 1 and 2); however, there were several individual loose pieces of net wrap free-floating in the rumen contents. Once it was sorted and balled up, the accumulated net wrap was about the size of a softball. The material removed from the rumen was not pure net wrap, but instead was a mix of net wrap tangled with feed. Additionally, two samples from the recently calved cows also had placental tissue that had been consumed by the cow tangled in them (Figure 3).
The cows with the additional piece of net wrap placed in the rumen at the beginning of the trial did not have any additional buildup of net wrap compared to those cows that did not have the additional net wrap. The weight of the net wrap was 0.8 to 1.1 pounds. There was no difference in volume displacement with the net wrap displacing 1 to 1.3 gallons of fluid.
Based on the potential net wrap offered compared to the net wrap removed during rumen evacuations, about half (53%) of the potential net wrap offered was recovered. The question remains why a larger portion was not recovered, but these results were similar to the study from Montana, where 47% of the net wrap was recovered throughout the digestive tract. There are multiple possible explanations for where this net wrap disappearance could have occurred, but regardless, the amount of net wrap in the rumen could have a significant effect on rumen capacity and function over the long term.
Unknown fate
This study indicates a significant amount of net wrap accumulated in the rumen of all cows during a single, 140-day feeding period. The fate beyond this single feeding period of the net wrap that accumulated in the rumen is unknown. However, because it is a plastic material that is known to degrade at an extremely slow rate, it is possible that at least a portion of it will remain in the rumen throughout the cow’s life.
Also unknown is whether similar amounts of net wrap will be added to the accumulation during subsequent feeding periods throughout the life of a cow. Potentially, several pounds of net wrap may accumulate over years in an older cow, with several gallons of rumen capacity displaced by net wrap. The cumulative effect on digestive capacity and health of cows is unknown beyond cases of mortality.
During this small study, consistent accumulation of net wrap was documented in all six cows. Additionally, cases of cows dying from complications associated with the buildup of net wrap or other plastic materials in the rumen are being documented more frequently. This short-term project provided a snapshot of the potential long-term implications of not removing net wrap from bales prior to grinding.
Many additional questions remain to be answered regarding long-term impact on cow performance and longevity. How much net wrap in the rumen will stop or slow the flow of digesta? Will the digesta that is wound up in the wad of net wrap ever break down or will it always continue to build? What happens to the placental tissue that is wound up in the net wrap wad? Will the pieces of net wrap that were free floating in the rumen contents end up entangled in the rest of the net wrap and enhance the size of the ball? What is the impact of developing replacement heifers on ground hay without net wrap removal prior to grinding? Will the net wrap stay with the cattle for the entirety of their life, even if they are never allowed access to net wrap in future years?
Further research is needed to fully understand the long-term implications of net wrap in cattle diets. •
