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The Sheep Nutrition Section was established in 1965. During the IV five year plan the Division of Nutrition, Physiology and Biochemistry including Grassland and Forage Agronomy was organized, which later (VI five year plan) separated as  the Division of Nutrition including grass land and forage agronomy (GFA). At a later date Division of Animal Nutrition was separated from GFA to concentrate its efforts on:

  1. to evaluate various types of feed resources- pasture (grasses, legumes), top feed resources, agro-industrial by-­products and non-conventional feeds,
  2. to determine nutritional requirements for various production functions in sheep,
  3. to develop feeding strategies for sheep, goat production,
  4. to identify and reduce the adverse effect of various anti-nutritional factors in 'the feed
  5. to improve low grade roughages

The significant research developments are:
Feeds and Feeding Practice and Nutritional Intervention: Survey work identified limiting nutrients (protein, energy, macro and micro minerals) based on primary data pertaining to existing feeding practices and the benefit of supplemental concentrate in term of weight and economic gain and demonstrated its advantages to the farmers in the villages. Supplementation of concentrate to lambs at 1.5% of BW during pre-weaning and 2.5% of BW post-weaning improved BW by 25% and fetched 25-40% more price than the conventionally reared lambs (grazing only). Based on nutrient availability and requirement a strategic supplementary schedule is developed to support optimum production, viz. 330 g ground maize to dry non-producing animals (30 kg) only during summer, maize+oil cakes 300+100, 0+115 and 240+200 g to pregnant (30 kg) and 0+125, 0+190 and 220+250 g to lactating animals during monsoon, winter and summer, respectively.

Expanding Feed Resource Base: The nutritive value of various feeds-grasses, legumes, top feeds (Khejri, Pala, Ardu, Mopane, Siris, etc.), pastures (Sewan, Cenchrus, Khimp, Kair etc.) available during different seasons was evaluated. Among top feeds, ardu leaves were found to be the best. A mixture of wheat straw and ardu leaves (50:50) could maintain the adult animals. The pasture had CP content in the range of 6-8% with 40-50% digestibility. Tree leaf based ration supported higher BW gain compared to conventional roughage source and thus fallen tree leaves can be incorporated in the diet of sheep up to 20% (better in the form of feed-block). Nutritive value and animal performance of artificially grown barley fodder (Fometa; yield 10.4q/day; DM 13%, CP 9.4%, TDN ≥80%, intake 3.2-4.0%) can also be used in sheep feeding. Prickly pear cactus (Opuntia) contain CP, 9.2-12.6%, and its feeding with conserved fodder could maintained adult sheep and requires additional N for supporting production and also holds promise to meet partly water requirement (80% moisture) in arid and semi-arid regions. Guar korma may replace groundnut cake up to 35% in concentrate ration without any deleterious effect. Siris and prosopis pods can be included up to 40% in the concentrate mixture. Cotton seed cake could replace groundnut cake on equal N basis in lamb ration. Complete feeds have been developed containing de-oiled rice polish and urea for maintenance purpose. Sugarbeat pulp 53% and sea weed meals 20% and wheat straw 25% with salt and mineral mixtures (3%) can replace expensive ingredients like maize, barley in the ration for lambs.

Nutrient Requirement Studies: 36 g TDN and 5 g of DCP per kg metabolic weight (or 10 g of TDN and 1 g of DCP per kg live weight) has been recommended as the requirement for maintenance. Consumption of TDN and DCP in the ratio of 8.5 at an intake level of 3 g DCP/kg live weight produced the highest growth in weaner lambs. Pregnant ewes during their advanced pregnancy required 7.8 g of DCP and 58.7 g of TDN per kg metabolic weight for producing lambs with 3.5-4.0 kg birth weight.

Attributes Requirement/kgW0.75
  TDN (g) DE (kcal) ME (kcal) Digestible protein (g)
Maintenance 27.30 120.12 98.50 3.0
Growth (per g gain) 1.79 7.87 6.46 0.2
Pregnancy 50.90 223.96 183.65 7.0
Lactation 53.00 233.20 191.22 8.5
Wool production 35.00 154.00 126.28 4.2

Study on energy expenditure of sheep indicated that a housed sheep spent 4.16 MJ/D, while grazing animals spent 43% higher. The expenditure of energy was 4.85 MJ/D during winter, which increased to 6.70 MJ/d during rainy season. The animals exposed to heat stress required more energy to meet their enhanced requirements of thermolysis and maintenance.

Requirement for wool production: Optimum nitrogen-sulphur ratio in the diet of wool producing sheep was found to be 5:1. Sulphur concentration of 0.24% in the diet produced maximum quantity of wool (i.e. 1392 g in 6 months clip with a scouring yield of 80%). The optimum level of CP and TDN in the ration for wool production in Marwari sheep was 10 and 50% respectively. Sulphur supplementation at 0.3% (as Na2SO4) with urea (1% of diet) supported reasonable increase in wool yield and quality (good carpet wool type) in sheep on grazing plus concentrate ration

Nutrition on Pasture: Most of the native grass species were sprouted immediately after rain and constituted the pasture for grazing by sheep viz. Tribulus terrestiris (8.90%), Indigofera cardifolia (16.2%), Crotolaria burhia (12.6%), Satha (16.9%), Zizyphus nummularia (11.4%), Dactyloctenium aegyticum (21.2%), Melilotus indica (9.31%) and other native grasses, during winter C. burhia, Z. nummularia, dead litter and Azardirachta indica leaves at 9.75, 40.3, 24.6 and 23.9 % and in summer Prosopis cineraria (33.3), Cynodon dactylon (28.0) and Z. nummularia (12.2%). Grazing sheep preferred Eluecina indica, Commenlina forsakalaei, Eriochloa polystachyca and C. burhia during onset of monsoon. The main pasture species was Cenchrus ciliaris (digestibility 44%) and the grass legume mixed pasture has cenchrus and dolichos (digestibility 50%). Dry matter production from cenchrus pasture in January was 10 q/ha. The CP% in the native pasture varied from 4.3 to 10.3 % and remained below 7% during September to March. TDN intake was low by 20 to 50% and DCP intake was adequate only during July-September. Phosphorus intake was not adequate for the most part of the year. Vitamin A level declined gradually from September to December and June. Preference index for DM and CP was 0.66 and 1.32, respectively indicating animals prefer to consume succulent material from pasture having high nutritive value.  

A stocking rate of 5 ewes/ha on cenchrus gave satisfactory performance. Sheep could very well be maintained on three, two and single tier silvi-pasture plots (biomass availability ranged from 21.72 - 28.91 q/ha) at stocking density of 12 animals/ha. During winter season, digestibilities of DM, CP, ADF and cellulose were lower than that of monsoon season. The monsoon and summer seasons are critical in terms of dry matter and nutrient intake, necessitating supplementation. Grazing studies under farmers’ management condition on natural rangeland at a stocking density of 3.5 sheep/ha alongwith followers observed to support BW gain and good economic returns.

Assessment of Biomass yield and nutrient composition of Community grazing land: The biomass yield of common grazing land in the month of September, January and May was 4.92, 1.36 and 1.93 DM q/ha. In winter and summer seasons the most of these species were withered off in natural cycles and formed dead litter, which constituted 20.71 % and 17.93% of the total biomass yield. Few plant species were found in winter season, viz. Zizyphus nummularia (34.9%) and Tephrosia hemintonia (44.4%), while in summer Zizyphus nummularia constituted 42.6% and Cynodon dactylon 39.4% of the total biomass. DM, CP, NDF, ADF and Lignin contents of range grasses were 55.0, 10.8, 64.8, 41.0 and 6.94 % during monsoon and 85.5, 10.02, 57.2, 42.3 and 10.01% during winter and 87.7, 5.5, 69.8, 44.9 and 15.2% during summer.

Estimation of soil ingestion in sheep on degraded rangeland of semiarid region: Soil ingestion from plants, as plant’s contaminants and ground in sheep was 92, 52 and 162 g/d during monsoon, 53, 0.0 and 83 g/d during winter and 64, 43 and 230 g/d during summer, respectively. Total soil ingestion during monsoon, winter and summer was 360, 137 and 337 g/day and 26.9, 12.0 and 41.0 g % of DMI.

Digestibility and nutrient selectivity measurements: Amongst different diet collection methods e.g. composite pasture sampling (CPS), mouth grab (MG), hand plucked (HP) and oesophageal extrusa (OE), and faecal collection methods (e.g. use of collection bags and chromic oxide indicator), the CPS, HP and MG methods over estimate DM and DE intake, the OE method had limitation of salivary nitrogen contamination and the double indicator method modified to reduce errors was found to be most appropriate. Oesophageal cannula was also fabricated and fitted in sheep for collection of representative sample of diet of grazing animals. Nutrient selectivity studies using oesophageal cannulated sheep, suggested that animal could preferentially select moderately high protein (CP 13%) diet, even during lean season, when pasture contained about 3-4% CP.

Supplementary Feeding: Besides maize and barley, Jowar (Sorghum), Bajra and damaged wheat can be incorporated in lamb ration. Creep ration containing 14.5% CP and 2.97 Mcal energy was found to be adequate that support higher pre-weaning gain. Milk replacer with coconut oil or a combination of vegetable oil successfully practiced with feed conversion ratio <4.0 and various feed formulations (high grain, inclusion of bypass fat) that can support desired rate of growth are developed for lambs to attain 33 kg body weight at 6 mo of age. The lambs gained at the rate of 150-180 g per day with 18-20% feed efficiency. To avoid higher deposition of carcass fat and to improve the efficiency of feed conversion the lambs can be weaned at 60th day and intensively fed to achieve target finishing weight.  High concentrate feeding (at 2.5 % of body weight) in cull ewes up to 90 days could improve body conditions and market value with better return to the farmers.

Methane Emission and Mitigation strategies: Different feed samples were screened to observe highest methane emission (ml/g digestible OM) in grain byproducts (20.4); amongst grains lower in Jowar (14.1) and higher in guar (18.3); amongst oil cakes higher in cotton seed (17.2) and lower in mustard cake (5.6); in forage samples khejri has lowest value; amongst crop residues higher in barley and lower in til straw. Methane emission reduced with the level of supplementation in both the lamb as well as adult ration. Spices straw can also serve as rumen modulator and ajowin, fenugreek and fennel can be incorporated up to 5-10% with lower methane. Similarly, tree leaves [Jatropha- (Jatropha curcas L), Pala (Ziziphus nummularia), Khejri (Prosopis cineraria), Ardu (Ailanthus excelsa), Neem (Azadirachta indica)] can be used (up to 20%) as a source of PSM for lowering methane production and improving fermentation attributes and digestibility.

Rumen Metabolism, Microbiology and Biotechnology: Under control feeding, dry-matter intake was lower while digestibility of fibre fraction was higher in goats compared to that of sheep, which could be partly due to the greater number of total ciliate protozoa as well as holotrichs and spirotrichs in the rumen medium of goats. Defaunation as a means of rumen metabolic manipulation could deliver more microbial and dietary protein availability, narrower P:E ratio (ruminants on low protein diet benefits more) with better ruminal fermentation efficiency. Further, a reduction in methane emission results in more ME availability for growth and wool production with a better FCR. A simplified cultural test using Fe-2 medium to detect mimosine degradation by the mixed rumen microbes of sheep and goat was performed. Feeding of probiotics, e.g. Lactbacillus acidophilus during pre-weaning and Saccharomyces cerevisiae during post-weaning found to support GI health with improved performance (better FCR).

Micronutrient Profile and Supplementation Strategies: The information on existing feeding practices and gaps in feeding systems for livestock of different agro-climatic zones of semi-arid Rajasthan has been documented. The micronutrient profile in different physiological stages have been worked out and prioritization of these nutrients in livestock feeding has been identified and a suitable strategy with the development of ‘Area specific mineral mixture’ for their supplementation has been practiced with improvement in reproductive efficiency  and milk yield.

Improvement of Poor Quality Roughages: Urea-treatment, feeding of crop residues in the form of ‘Sani’ and fungal (Coprinus fimatarius) treatment improved its nutritive value. Exogenous enzyme pre-treatment of roughages at 30% moisture level showed promise through improvement in nutrient digestibility.

Nutrition-Environment Interaction: Under heat stress the growing lambs, require additional energy to support the priority functions of thermolysis and growth. The adult animals fed 115 and 130% above their maintenance requirement during summer under hot sun not only sustained their weight but could increase it suggesting that the animals had enhanced energy requirement during summer.  With erratic feed and water availability, during migration in hot arid region, the goats could sustain the enhanced stress better than sheep. Goats, despite lower feed and water intake, retained ingesta longer in their gut, thereby, efficiently utilized the feed and sustained their higher body weights. When subjected to graded nutritional stress Malpura and Chokla sheep and Sirohi goats, compared to Avikalin and Avivastra, with their lower body reserve lost more weight and took longer period to regain and the effect was pronounced in winter as compared to that in summer.

Complete Feeds for Small Ruminants: Complete feeds have been developed by incorporating roughages (ground cowpea, and cenchrus hay, Pala, Ardu, and Khejri leaves] and concentrates in mash form or in pellets. Various complete feeds with concentrate and roughage at 50:50, 60:40 or 75:25 have been developed for different production. An economic complete diet could be cenchrus straw (38.6%), dried ardu leaves (37%), wheat bran (14%), mustard cake (7.4%), common salt (1%) and mineral mixture (2%). Dead litter including fallen tree leaves in complete feed blocks could form a maintenance ration during scarcity. Fungal treated straw could also be included in complete feed block.