8 NUTRIENT REQUIREMENTS OF ANIMALS
NUTRIENT REQUIREMENTS OF YAK ANDMITHUN
ICAR
Indian Council of Agricultural Research New Delhi
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Dr R P Sharma Reena Kandwal Dr V K Bharti Punit Bhasin
Dr V K Bharti and Punit Bhasin
Correct Citation: Nutrient Requirements of Animals - Yak and Mithun (ICAR-NIANP), 2013
Š 2013, All rights reserved Indian Council of Agricultural Research, New Delhi
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Published by Dr Rameshwar Singh, Project Director, Directorate of Knowledge Management in Agriculture, Indian Council of Agricultural Research, New Delhi 110 012; Lasertypeset at M/s Dot & Design, D-35, Ranjeet Nagar Comm. Complex, New Delhi 110 008 and printed at M/s Royal Offset Printers, A-89/1, Naraina Industrial Area, Phase I, New Delhi 110 028.
CONTENTS SI. No. Title
Page No.
Yak 1. 2. 3.
Introduction Feeding Systems Nutrient Requirements Feed Intake Protein Requirements Energy Requirments Fasting Heat Production Mineral Requirements
References Annexures A1 Tree leaves commonly fed to yak in A2 Chemical composition of tree fodder (% on DM basis) commonly fed to yaks in Arunachal Pradesh List of Tables
1 2 3 3 6 7 8 9 10 14 14
15
16
Mithun 1. 2. 3.
Introduction Feeding Systems Nutrient Requirements Dry-matter Intake Protein Requirements Energy Requirments Mineral and Vitamin Requirements
References Annexures A1 Nutrients and condensed tannin (CT) contents in different forest foliages in mithun grazing areas of North-Eastern Hilly region of India A2 Variations in macro- and micro-mineral concentration of important forest based foliages in mithun grazing areas of North-Eastern Hilly region of India List of Tables
16 17 17 17 18 20 21 22 24
27
28
YAK Introduction The yak (Poephagus grunniens or Bos grunniens), the hairy bovine of snow-covered high altitude, has a long linkage with the mankind inhabiting in the .remote mountainous regions of India, Bhutan, China, Mongolia, Nepal and other parts of central Asia. The population of yak in India is about 83,000 (DAHDF, 2007), maximum being in Jammu and Kashmir followed by Sikkim and Arunachal Pradesh. It belongs to the order Artiodactyla, family Bovidae, sub-family Bovine, genus Bos, and species grunniens and mutus. The yak was domesticated from its wild form (Bos mutus) and some of them are still found in the remote mountains of Tibet plateau, and adjacent highlands of neighbouring regions ofIndia and China. It is a multipurpose animal adapted to harsh environment of high altitudes ranging between 3,000 to 6,000 m above sea level. The chromosome numbers of yak, Bos taurus andBos indicus are the same (2n=60) and hence these animals are inter-breedable. Yaks have thicker coat of hair with outer coarse hair and inner dense fine hair, better lung capacity and ability to climb on hilly terrains and better adaptation to the hypoxic condition of high altitude due to higher haemoglobin content and larger (4.83/A) red blood cells (RBC) than the cattle (4.38/A). The RBC number is also higher, thus increasing its blood capacity to retain more oxygen (Zhang etal., 1994). A low pulmonary vasoconstriction (Anand et al, 1988) and high oxygen affinity of haemogobin (Weber et al., 1988) favour the survival of yaks at high altitude. Cup-shapedhooves help yaks to walk on steep hills and slippery snow-covered grounds for carrying loads. The surface area of yaks is relatively less per unit of body weight. This is a quite useful adaptive characteristic for living at high altitude. Yaks have great craving HH mm for salt. This habit has been used to attract animals. They return from pastures for obtaining salt on the fixed jPIPBj day and time. Salt is fed at weekly or fortnightly * , intervals. In hilly yak-rearing regions leaching of minerals * by rain water is very common, hence soil is deficient in important .
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NUTRIENT REQUIREMENTS OF YAK AND MITHUN
mineral elements thereby reducing the level of minerals in vegetation. Yak herdsmen realize the need of salt and they generally offer salt along with about 200 g of wheat floor. The conversion of carotenes into vitamin A is less efficient in yak as in cattle.It is evident from the highyellow pigmentation of butter fat in yak milk. The Indian Council of Agricultural Research, Govt, of India initiated the research on yak on various aspects of yak husbandry by establishing a dedicatedinstitute “National Research Centre on Yak� at Dirang, Arunachal Pradesh in 1989. This versatile bovidis a major source of livelihood in highlands, where agricultural activities are not remunerative due to non-availability of arable land. Yale products include meat, milk, wool andleather for clothing, blankets, bags, implements, rugs and tents and, bone for carving. Besides, it is also an important pack animal for transport, trade, agriculture and eco tourism. It serves as a financial asset and security for investment and during family ceremonies.
Feeding Systems Yaks are reared under free-range system by the highlanders. The yak herdsmen (Brokpas or Drokpas) migrate with their animals during May to alpine pastures (4,500 to 6,000 m above sea level) for summer grazing. At the beginning of winter during October, they move down to mid-altitude (3,000 m above sea level) so that these animals live on almost same environment as cattle. From October to April, yak herdsmen stay in villages and rear them in adjoining pasture lands, which are simultaneously grazed by the sheep, hill cattle and ponies. Over-grazing and snowfall have resulted in the deterioration of pasture land. Yaks are taxed heavily in winter due to inadequate fodder resulting in the loss of body weight (25 to 30 per cent). Several trials at NRC Yak, Dirang have shown that there was reduction in milk yield but not complete cessation. Yak herdsmen usually feed these animals with salt at regular interval. Generally milch and pregnant animals are fed small amounts of concentrates in the form of wheat flour or maize flour etc. to support optimum milk production and normal foetal development (Chatterjee 2003; Buragohain etal. 2004) . The quality of some of the pastures where the yaks graze in Arunachal Pradesh have been evaluated (Basu and Chatterjee 2002; Basu etal. 2005). Some tree leaves and shrubs available in Arunachal Pradesh are very much relished by yaks (Chatterjee et al. 2001; Chatterjee etal. 2003a). Tree leaves andshrubs in this area have been identified, and their chemical composition estimated (Annexures 1 & 2). During peak winter due to shortage of feed the yak migrates to lower altitude in search of fodder.
NUTRIENT REQUIREMENTS OF ANIMALS
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Nutrient Requirements Not many investigations have been carried out on nutrient requirement of yaks due to natural and social constraints. Scientific feeding of yaks is generally not followed. The nutrition research group of Qinghai Academy of Animal and Veterinary Science, China has been studying systematically the digestion, energy and nitrogen metabolism in yaks since last two decades. The available information is based on the limited studies carried out on the nutrient requirement of yaks under free-range conditions in China and stallfed conditions in India.
Feed Intake Dry matter (DM) intake in yak depends on factors such as age, body weight, sex, nature of feed, climatic condition and management. The feed intake per unit body weight under grazing is higher compared to stall feeding. Lesser feed intake under stall feeding might be due to the restriction of feed offered (Liu et al. 1997). Yaks generally consume less DM than the cattle and buffaloes, probably because of their smaller rumen capacity. There is a correlation between the DM intake (DMI) and body weight in yak. Liu et al. (1997) developed an equation to estimate the DMIin growing yak under grazing on natural pasture: DMI (kg/day) = 0.0165 W + 0.0486 (r= 0.959)
where ‘W’ is body weight in kg Han etal. (1990a) studied the feed intake in 2- to 3-year-old castrated yaks under stall-fed condition, and observed that DMI varied from 1.38 to 2.34 kg/ 100 kg body weight when the animals are maintained on green forages, dry roughages, or on diets based on dry roughages and concentrates (Table 1). They also observed that feed intake increased at lower temperature both under stall fed and grazing conditions. The faster rate of passage of feed at lower temperature might be the reason for higher intake. In grazing yaks the DMI was 3.01 and 3.38 kg/ 100 kg body weight (Table 1), when they were maintained on mature and premature forages respectively (Liu et al. 1997). The DMI was two per cent of the body weight in adult yaks (average body weight, 212 kg) maintained under grazing at an altitude of 4,242 m above sea level (Basu et al. 2005). Yaks graze comfortably at a temperature as low as -30°C to -40°C or even lower. In contrast, at higher temperature, their grazing activity is reduced resulting in lower feed intake. Yak cows need extra feed to meet the requirement for milk yield. Lactating yaks consume more feed at low temperature. Dong et al. (2000)
NUTRIENT REQUIREMENTS OF YAK AND MITHUN
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Table 1. Dry matter intake of growing yaks kept on diets under stall feeding and grazing Diets
Stall-fed condition* 87 % cone. + 13 % wheat straw (n=6) 48 % cone. + 52 % wheat straw (n=8) 28 % cone. + 72 % wheat straw (n=6) 40 % fresh grass + 40 % fresh bluestem + 20 % fresh alfalfa (n=4) (n=10) Oat hay (n=10) Oat straw (n=10) Wheat straw Grazing on natural grassland** Premature forage (n=7) Mature forage (n=7)
Intake (kg)/100kg BW
g/kg075
Body wt. (kg)
(kg)/day
134.1 159.3 166.5 178.3
3.1 3.4 3.0 3.7
2.31 2.13 1.80 2.07
79 76 65 76
145.2 145.2 145.2
3.4 3.4 2.0
2.34 2.34 1.38
81 81 48
115.3 125.9
3.9 3.8
3.38 3.01
111 101
Source: *Han etal. 1990a; **Liu etal. 1997
developed the following equation to estimate the DMI in lactating yaks: DMI = 0.008 W052 + 1.369y (r=0.992) where ‘W0 52’ is the metabolic body weight (kg) and cy’ is the milk yield (kg/ day, 4 per cent milk fat) The DMIin yak depends on the type of feed resources. It was observed that feed blocks with area-specific mineral mixture can supply adequate nutrients to yaks for supporting optimum growth rate during winter months (Ghosh and Chatterjee 2011a; Ghosh and Chatterjee 2011b). The DMI on feeding various feed blocks is shown in Table 2. Table 2. Composition of complete feed blocks and Dry matter intake in yaks
Ingredients Paddy straw Maize stover Tree leaves Maize crush Deoiled rice bran Rice polish Deoiled groundnut cake Deoiled mustard cake Molasses Lime Salt DM intake (kg/ 100 kg BW)
1 50.0
2
Complete feed block 5 4 3
40.0 10.0
30.0 10.0
8.0
25.0 25.0 8.0
15.0 13.0 13.0 7.0 1.0 1.0 2.17
13.0 20.0 18.0 7.0 1.0 1.0 2.29
14.0 10.0 13.0 3.0 1.0 1.0 2.38
24.0 5.0 8.0 3.0 1.0 1.0 2.42
50.0 8.0 10.0
50.0 8.0 20.0
10.0 13.0 7.0 1.0 1.0 2.70
5.0 8.0 7.0 1.0 1.0 2.68
6
Vitamin AD3 20g/ 100 kg b.wt.; area-specific mineral mixture of Zn, Cu, Co, Mn 40:20:10:10. Source: Baruah etal. 2011, 2012
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The intake of DM, protein and energy, and body weight gain in growing yak calves maintained on diets containing different levels of protein and
energy under stall-fed condition are shown in Table 3. Table 3. Intake of DM, protein and energy, and body weight gain in growing yak calves fed diets (240 days) containing different levels of protein and energy Parameters Protein (NRC 1989) Energy (NRC 1989) Initial body weight (kg) Male Female Average Final body weight (kg) Male Female Average Total body weight gain (kg) Male Female Average Average daily gain (g) Male Female Average DMI (kg/day) Male Female Average DMI (kg/100 kg BW/day) Male Female Average DMI (g/kgW0J5/day) Male Female Average DCPI (g/kg BW gain) Male Female Average TDNI (kg/kg gain) . Male Female Average
Experimental groups LP-LE LP-HE HP-LE 75 per cent 100 per cent 75 per cent 75 per cent 100 per cent 75 per cent
100 per cent 100 per cent
98.3 83.1 90.7
96.5 84.1 90.1
97.7 82.4 89.9
95.7 84.3 90.3
182.3 159.3 170.8
192.7 174.3 183.5
195.6 176.7 186.2
200.3 181.7 191.1
83.9 76.3 80.1
96.3 90.3 93.3
98.1 94.3 96.2
104.6 97.3 100.9
349.9 318.1 334.2
401.4 376.4 388.9
408.3 393.1 400.7
436.1 405.8 420.9
4.6 3.8 4.2
4.7 4.1 4.4
4.6 4.0 4.3
4.5
2.5 2.4 2.5
2.4 2.3 2.4
2.3 2.2 2.3
2.3 2.2 2.2
93.3 87.4 90.3
92.2 89.9 91.1
86.5 81.8 84.2
84.2 83.7 83.9
593.8 616.1 604.9
519.5 520.4 519.9
696.2 707.1 701.7
686.8 700.7 693.8
5.4 5.7 5.6
4.8 5.0 4.9
4.6 4.7 4.7
4.7 4.6
HP-HE
4.4 4.5
4.5
LP-LE, low protein-low energy; LP-FIE, low protein-high energy; FIP-LE, high protein-low energy; HP-HE, high protein-high energy Source: Santra and Baruah (2012)
NUTRIENT REQUIREMENTS OF YAK AND MITHUN
6
In China, the supplementation of molasses-urea block (40 per cent molasses, 10 per cent urea, 13.5 per cent rape seed cake, 10 per cent wheat bran, 13.5 per cent grass, 2 per cent salt, 1 per cent trace element and 10 per cent binder elements) has been found to be good for maintaining yaks during winter months (Xie et al. 1995; Chai etal. 1996). Chatterjee etal. (2004) studied the intake and nutrient utilization in yaks fed paddy straw supplemented with concentrate mixture. Pourouchottamane et al. (2006a, 2007) studied the feed intake and growth performance of yak calves. Ghosh and Bandyopadhyay (2008) studied the effect of feeding regimes on growth performance and nutrient digestibility of Indian Yaks under semi-intensive system.
Protein Requirements The protein requirements for maintenance are equal to the nitrogen lost in urine together with the nitrogen required for the growth of hair as well as that lost as dead skin cells. Endogenous urinary nitrogen excretion in yak is lower than in cattle. This might be due to more nitrogen recycled to the rumen than in cattle. Currently information on protein requirements for maintenance, growth, lactation and hair growth in yak is meagre. Xue et al. (1994) conducted two trials on the protein requirements for maintenance and growth in yak. In the first trial, animals were given a low nitrogen ration (0.98 per cent) to study the degradation of endogenous nitrogen andlowest maintenance nitrogen. In the second trial, three different rations having 6.7, 10.1 and 13.4 per cent CP were fed to 18 growing yaks with 6 animals in each group. Based on the body weight gain (kg/day), nitrogen balance and the deposit, the following equations were developed: 1. DCP requirement for minimum maintenance = 2.012 W0 52 (g/day) 2. DCP requirement for maintenance (DCPBJH) =6.61 W"-52 (g/ day) obtained with low nitrogen ration 3. DCPRm= 6.09 W0 52 (g/day), obtained with nitrogen balance trial 4. DCP requirement for growth (DCPRg) = (0.0011548/AW+
Wo-52)-1 (g/day) 5. Total DCP requirement= 6.09 W째-52+ (0.0011548/AW+ 0.0509/ W052) 1 (g/day) From the above equations, digestible protein requirements for maintenance and growth (100 to 500 g body weight gain per day) were calculated (Table 4). During May and June (budding season) the protein content in grass is adequate to allow 500 g body weight gain per day followed by 300 to 400 g body weight gain per day duringJuly to September. During the periods of October to November and December to April, the DCP level in the grasses is not adequate to maintain the body weight. Animals
NUTRIENT REQUIREMENTS OF ANIMALS
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loose body weight and hence nitrogen supplement is necessary to support optimum growth and maintenance (Liu et al. 1997). The protein intake and requirement of growing yaks during different phenological seasons is shown in Table 4. Table 4. CP intake and requirement for growing yaks Parameters
Body weight (kg) Biomass (g/m2) CP intake (g/head/day) Requirement for maintenance (g/head/day) Growth (g/day) 100 200 300 400 500
May-June (Budding) 122.60 49.18 732.77
July-Sept. (Green) 115.34 80.69 258.38
Oct.-Nov. (Yellow) 125.96 57.92 159.97
Dec.-April (Dry) 120.11 43.55 50.98
92.85
89.94
64.16
91.86
79.50 125.64 155.78 176.99 192.75
78.82 123.96 153.20 173.68 188.83
79.79 126.38 156.91 178.47 194.50
79.27 125.08 154.91 175.88 191.43
Source: Xue etal. 1994
Long et al. (1999) observed a daily fasting nitrogen excretion of 316 mg per kg W0 75 per day for yak cows. The low EUN excretion could be due to more nitrogen recycled to the rumen. Xue et al. (1994) estimated the rumen degradable crude protein requirement for maintenance (RDCPm) as g/day and reported a value of 6.09 W0 52 g/day for growing yaks. They also suggested using the following equation for estimating the crude protein requirement of growing yaks. This includes maintenance and gain in body weight (RDCPg). RDCP (g/day) = 6.09 W0 52 + (1.16/DG + 0.05 W0.52)'1 where DG is daily gain in g/day. However, these calculations were based on limited observations and hence further studies are necessary to support their claim. Saikia et al. (2009) reported that optimum gain of 450g/day can be achieved based on 100 per cent protein requirement of Kearl’s (1982) feeding standard. Information on the proteinrequirements for growth, lactation, gestation and for pack animal is very meagre. Hence, the protein requirements for different physiological functions such as growth, lactation, gestation and pack purpose may be used as recommended by NRC (1989) for dairy cattle.
Energy Requirements Energy is required for maintaining all the vital processes of the body. Even when an animal is in fasting it produces appreciable quantities of metabolic heat. This indicates that it draws energy from body reserves to
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NUTRIENT REQUIREMENTS OF YAK AND MITHUN
support its energy- demanding basal processes (Mac Rae 1987). The utilization of energy differs based on sex, age and physiological functions of an animal. It also depends on the composition of diet and the level of feeding. Lactating yaks utilized dietary energy more efficiently than dry yak cows when they are fed at the same level with oat hay. However, yak cows utilized metabolizable energy less efficiently for milk production compared to dairy catde (Long et al. 1998).
Fasting Heat Production Fasting heat production (FHP, KJ/ kgW0 75/ day) in growing yaks remains constant compared to that in yellow cattle. This might be related to the ability of yak to take more oxygen at higher altitudes. Like other ruminants, FHP for one-year-old calf is higher than that for three-year-old heifer. Hu (1994) observed that the respiratory quotient (RQ) of growing yaks decreased significantly with increasing altitude from 0.74 (2261 m) to 0.69 (3250 m) and 0.54 (4272 m), but it did not vary among the different age groups. Lower atmospheric pressure and oxygen contents at higher altitudes might be the factors for die reduction of RQ of growing yaks. He further observed that ambient temperature had a great influence on FHP and other physiological attributes in yaks. However FHP remained constant and the body temperature, heart rate and respiratory rate of yaks were stable within the environmental temperature range of 8° to -14°C. Hence, the thermal neutral zone for yaks was suggested as 8° to -14°C. Krishnan et al. (2009) observed that yaks experienced stress at an environmental temperature above 10°C. They further reported that with increasing environmental temperature the thermal adaptability of yak decreases, but it increases with the decrease in environmental temperature. Hu (1994, 1997) investigated the relationship of body weight (W) and surface area in growing yaks. The highest correlation was observed between the surface area and w0 52, and an equation of FHP = 916 KJ/ kg W0'52/ day (n=25, r=0.8469, p<0.01) was proposed. He further suggested that FHP value of yak calves is lower than the dairy catde calves andHolstein heifers, and heat lost per 1 kg W° 52 in yak is lower than in catde. Heat production in fasting yaks remains constant even at high altitudes, whereas in cattle heat production increases with increasing elevation (Hu 1994). Themetabolizable energy requirement for maintenance (MEm) of growing yaks is 460 KJ per kg W075 per day. Han et al. (1990b) estimated metabolizable energy requirements for growth (MEg) by energy balance trial and suggested the following equation: ME (MJ/day) =0.45 W075 + (8.73+0.091W) DG
NUTRIENT REQUIREMENTS OF ANIMALS
9
Where, W is the body weight and DG is daily gain (kg) The efficiency of utilization of metabolizable energy for growth (K ) in yak is 0.49 (Han etd. 1990b). Similar values were reported by Han et aL (1992) and Dong etd. (2000), when animals were given matured forages. Han etal. (1989) estimated the energy requirements for standing and walking in yaks. They reported that energy expenditure of yaks was higher while standing and walking than of yellow cattle. Higher heat production could be due to difference in body size andbreed as smaller animals generate more heat during walking (Blaxter, 1962).
Mineral Requirements No information is available on the mineral requirement of yaks. There are reports on mineral constituents in yak milk (Chatterjee et d. 2003b), mineral constituents in yak hair (Bhattacharya et d. 2004; Chatterjee et d. 2005; Chatterjee and Sheikh et d. 2011), blood biochemical constituents (Pourouchottamane etd. 2006a), mineral concentrationin feeds and fodder (Chatterjee et d. 2011a; Chatterjee et d. 2011b). The macro and micro element status in yak under semi range system have been reported by Chatterjee et d. (2006) and Ghosh et d. (2009). Yaks are not usually supplemented with any kind of mineral supplement. There couldbe mineral deficiency due to non-availability of feed during winter months and also due to leaching during summer in draining water of melted snow. Ghosh (2009) reported that blood calcium profiles in some parts of Arunachal Pradesh, viz. Grander and Mandala and Lachung of Sikkim were low. Similarly, most of the soil samples of Arunachal Pradesh and Sikkim are also deficient in copper (Cu), zinc (Zn), cobalt (Co) and manganese (Mn). Therefore, the supplementation of trace minerals Zn, Cu, Co and Mn in the ratio of 40:20:2:1 could be beneficial to solve the reproductive problems like anoestrus, repeat breeding and longer interÂŹ calving period in yaks. Pourouchottamane et al. (2012) reported that mean values of Cu, Co and Zn in blood were 0.255, 0.654 and 1.064 mg/litre respectively. The mean value for Cu was much lower than the critical level compared to the value reported by McDowell (1985). This indicates lower Cu level in yaks under traditional migratory system in both summer and winter grazing pasture. However, the mean Co and Zn values were significantly higher in animals grazing in summer pasture than those grazing in winter pasture. Dong et al. (2000) reported that calcium and phosphorus were in negative balance when fed oat and hay diet as sole feed. The available information indicates that seasonal deficiency of minerals exists in different parts of a yak-rearing region.
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NUTRIENT REQUIREMENTS OF YAK AND MITHUN
Conclusion Yak is a multi-purpose animal and has several contributions to the economy of people living at high altitude. The information on nutrient requirement of yak is meagre. The limiteddata available on feeding practices and nutrient requirement have been compiled from India and abroad, and presented in this publication. Further, detailed studies on protein, energy, minerals and vitamins involving large sample size are necessary for determining precisely the nutrient requirements for this species.
References AnandI, Health D, Williams D, Deen M, Ferrari R, Bergel D andHarris P. 1988. The pulmonary circulation of some domestic animals at high altitude. International Journal ofBiometeorokgy 32: 56-64. Anonymous. 2008. AICRP on Feed Resources and Nutrient Utilization for Raising Animal Production. National Research Centre on Yak, ICAR, Dirang, Arunachal Pradesh. Baruah K K, Chakravarty P, Paul V, Sarma H, Ahmed F A and Das K C. 2011. Effect of feeding complete feed block based on unconventional feeds on growth performance and nutrient utilization of yak calves. Indian Veterinary Journal 88: 134-36. Baruah K K, Paul V, Ahmed F A, Chakravarty P, Deori S, Sarma H and Saikia A. 2012. Effect of strategic feed supplementation on growth performance and nutrient utilization in yak calves during winter. IndianJournal ofAnimal Sciences 82: 220-22. Basu A and Chatterjee A. 2002. Nutritional Evaluation of a pasture for yak. Indian Journal ofAnimalnutrition 19: 159-61. Basu A, Chatterjee A, Baruah K K and BhattacharyaM. 2005. Voluntary feed intake and live weight gain in yaks (Poephagusjyrunniens L.) grazed on high altitude grassland. IndianJournal ofAnimal Sciences 75: 81-83. Bhattacharya M, Chatterjee A, Ram Kishore, Sudarshan M and Chakraborty A. 2004. Elemental concentration in hair of domestic animals - a SEM-EDS study. Indian Journal of VeterinaryAnatomy 14: 80-82. Blaxter K L. 1962. The Energy Metabolisum of Ruminants. Hutchinson Scientific and Technical, London. Buragohain R, Chatterjee A, Ghosh K, Pathak P K and BhattacharyaM. 2004. Prospects of yak husbandry in Arunachal Pradesh. Livestock International 8: 20-23. Chai S T, Liu S J, Xie A Y, Zhao Y P, Zhang X W and Qiu G F. 1996. Study on utilization rate of feed nitrogen content in growing yak. China Herbivores 4: 36-39. Chatterjee A, Basu A and Sarkar M. 2004. Nutrient utilization in yaks fed paddy straw supplemented with concentrate mixture.Indian VeterinaryJournal 81: 263-65. Chatterjee A. 2003. Feeding Management of Yaks. North East Veterinarian 3: 18. Chatterjee A and SheikhIU. 2011. Mineral status in Yak through hair tissue mineral Analysis: Effect of age and sex. Veterinary Science ResearchJournal 2: 16-18. Chatterjee A, De D and SheikhIU. 2011a. Macro and micro elemental concentrations in some locally available tree fodder of Sikkim. Indian Journal of Animal Sciences 81: 984-87.
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