Effect of strategic feed supplementation on growth performance and nutrient utilization in yak calves during winter

Yaks are reared under free-range system by the highlanders. The yak herdsman (Brokpas or Drokpas) collect yak during April and migrate to alpine pastures about 4,500 to 6,000 m above msl for summer grazing and during winter they move down to 3000 m above msl so that the animals live on almost same environmental conditions. In winter, yak herders stay in the village and graze the yaks in adjoining pasture lands, simultaneously grazed by sheep, hill cattle and ponies. Over grazing has resulted in the deterioration of pasture land to a great extent. Yaks are taxed heavily in winter and loss body wt 25–30% due to inadequate fodder resources (Long et al.1999). There are very meager information on growth performance of yak calves on feeding supplementary feed. The objective of this study was to assess the performance of yak calves on feeding complete feed block with area specific mineral mixture at mid altitude during winter. The study was carried out at Mandala of West Kameng district of Arunachal Pradesh at 10,000 ft above msl. The West Kameng district is situated between 91°30′E to 92°40′ E longitude, 26°54′ N to 28°10′ N latitude encompasses an area of 7422 km. The lowest temperature of Mandala is being –1.08°C in January and highest temperature being 13.62°C in July with an average temperature of 4.8°C. Eighteen male calves 12–15 months of age average body wt. 153 kg belonging to 10 brokpas (yak herder) families were allocated into three groups, viz. G1, G2, and G3 of 6 calves in each group. During first 60 days of experiment, animals of each group were offered complete feed block (CFB) based on maize stover, maize stover + salix leaves and concentrate in the ratio of 50:50 (G1): 25:25:50 (G2) respectively. The third group (G3) was allowed for grazing only. All the experimental animals were fed area specific mineral mixture (Zn, Cu, Co, Mn) in the ratio of 40:20:10:10 (630 mg/d). However, during next 60 days of experiment G1 and G2 were fed same CFB as former feeding period and G3 group was fed CFB based on maize stover + salix leaves and concentrate mixture. Similar to the earlier period all the experimental animals were fed area specific mineral mixture. Yaks of G1 and G2 group were maintained throughout the trial of 120 days in a well ventilated shed and tied up individually where they can move freely. However, G3 group of yaks were tied during next 60 days of experiment in the same shed. Feed was offered in wooden mangers and were provided for each animal separately. Maize stover and salix leaves were chaffed to the size of 1 cm approximately. The chaffed maize stover and salix leaves was then thoroughly mixed with different ingredients. The ingredient composition of CFB offered to animals in