Correction factors for length of lactation, age at calving and lactation number in Sahiwal cows
2001
Shafiq, M. (Livestock Production Research Inst., Okara (Pakistan)) | Javed, K. | Khan, M.A.
The data on Sahiwal cows maintained a Livestock Experiment Station, Bahadurnagar (Okara) during 1970 to 1999 were used to develop correction factors for length of lactation, age at calving and lactation number by regression method. The linear trend was observed in milk yield for lactation length. The milk yield increased by 6.0446 kg for each day increase in lactation length. The correction factors for length of lactation ranged from 3.2507 to 0.6054 at 100-102 and 493-500 days of lactation, respectively. A curvilinear trend was found in milk yield for age at calving and lactation number. The milk yield increased @ 12.9884 kg upto 164 months of age and then decreased @ 0.0515 kg for each month increase in age at calving. while it increased @ 1742.5894 kg upto 6th lactation number and thereafter, decreased @ 11.9755 kg for. each lactation with the increase in lactation number, respectively. The correction factors for age at calving ranged from 1.3101 to 1.0003 at the age 32 and 124 months, respectively. The constants were calculated as - 66.0002, 1108.7733 and 1515.2251 for lactation length, age at calving and lactation number, respectively. These correction factors may be used to adjust the lactation records on 305-day mature equivalent (ME) basis for comparison in the selection of Sahiwal cows for higher milk yield.
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