X. Xiaolin, Y. Rongzhen, X. Jington, L. Quan and W. Yaping
Qinghai Academy of Animal and Veterinary Sciences, Xining 810003, Qinghai, P.R. China
Southern Qinghai is the main habitat of Qinghai yak. This study was conducted to evaluate the growth, development, meat and milk production of the local yak to provide information as a basis for the genetic improvement of yak in the area.
Ten yak cows were divided into two groups: a group of 5 cows, which were in their second lactation; and another group of 5, which were in their first lactation. The milk yield was determined from May to September with milking once a day in May and September and twice a day for the other months.
Seven yak cows with calves and 5 without calves were ear-tagged and weighed on 10 May 1997, 7 November 1997, 15 March 1998 and 7 June 1998.
Six pack animals, consisting of three in advanced age (more than 10 years) and three younger sets (5–7 years of age), were selected from the Xueshan Township for a slaughter experiment on 27 and 28 September 1998.
Local yak, ranging in age from birth to 5 years, were weighed at an interval of 6 months (Table 1). The results showed a rapid growth before 2.5 years. The following years showed little variation until the age of 4. From 4 years on, the body weight varied substantially with seasons. However, the average body weight obtained from this study was lower than the previous investigation in the early 1980's, which indicated degeneration in the performance of the local yak.
Table 1. Body weight (kg) and linear body measurements (cm) of Guoluo yak.
Age (year) |
Body weight |
Height |
Body length |
Heart girth |
Cannon bone circumference |
At birth |
11.74 ± 1.27 |
52.60 |
48.45 |
56.38 |
7.71 |
0.5 |
50.18 ± 10.74 |
79.60 |
76.77 |
96.47 |
10.75 |
1 |
83.01 ± 12.89 |
87.46 |
90.72 |
121.19 |
13.86 |
1.5 |
99.42 ± 16.31 |
89.10 |
91.35 |
115.00 |
12.63 |
2 |
109.68 ± 16.63 |
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2.5 |
134.10 ± 27.77 |
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3 |
135.23 ± 18.59 |
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3.5 |
141.31 ± 40.71 |
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4 |
143.89 ± 25.74 |
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4.5 |
196.68 ± 21.27 |
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5 |
156.42 ± 30.33 |
The data on milk production showed a higher milk yield in cows (1.06 kg) than in the heifers (0.67 kg). However, for both groups (cows and heifers), milk yield was higher in June, July and August than in May and September. Milk fat was 6.57% for cows and 6.69% for heifers.
The body weight of cows in nursing and non-nursing states increased by 3.4 kg (about 2%) and 13.65 kg (7.7%), respectively. The non-nursing cows showed an obvious increase in body weight from later spring to autumn in 1997 but a rapid decrease from the autumn of 1997 to the next spring in 1998 (Table 2).
Table 2. Body weight of cows at different nursing states.
Nursing state |
10 May 1997 |
7 Nov. 1997 |
15 March 1998 |
7 June 1998 |
Nursing |
166.8 ± 27.5 |
185.7 ± 33.2 |
172.7 ± 32.2 |
170.2 ± 19.2 |
Non-nursing |
178.1 ± 17.5 |
243.2 ± 20.6 |
222.0 ± 13.3 |
191.8 ± 11.7 |
Results from the slaughter test indicated that the older yak (over 10 years) were heavier, had a higher dressing weight, produced a higher net meat yield, had heavier bone and a larger eye muscle area than the younger (5–7 year old) animals (Table 3).
Table 3. Meat production of the local yak.
Age |
Live weight |
Dressed weight |
Net meat |
Bone |
Eye muscle area |
>10 |
373.3 ± 25.2 |
210.3 ± 24.7 |
176.4 ± 24.8 |
33.9 ± 2.3 |
53.2 ± 9.4 |
5-7 |
203.3 ± 27.5 |
110.8 ± 25.5 |
90.6 ± 25.3 |
20.1 ± 7.0 |
41.4 ± 10.8 |
Due to the lower meat and milk productivities of the local yak, it was suggested that crossbreeding by introducing wild yak genetics should be considered as a possible approach for their improvement.
The authors are most grateful to the financial support from the Project Office of Qinghai Animal Husbandry Bureau.
