Girma Abebe

Interval Method to Estimate Lactation Yield: of Crossbred Cows (Friesian X Arsi) at Agarfa, Bale Girma Abebe

To test the accuracy of 30-day TIM with 15 and 45-day TIM of milk recording to estimate the lactation yield and to measure the effect of genetic group, parity and season of calving on the accuracy, 1220 lactation records of Friesian x Arsi cows were utilized. The lactation yield was estimated for lactation length of 210-305 days. The accuracy was measured in terms of absolute difference and percentage difference between actual and estimated yield. The study revealed that 15, 30 and 45-day time interval can estimate lactation yield accurately to extent of less than five percent bias irrespective of genetic group and parity. The season of calving significantly (P 0.05) affected the percentage difference in 15-day TIM. The lactation yield estimated by 15-day TIM was more accurate with high R2 value 99.62%. The regression analysis indicated that actual yield of 9th period in 15-day, 5th period in 30-day and 3rd period in 45-day TIM predicted reliable estimate of 305-day yield. Thus 30 and 45-day time interval methods of recording can be used in estimation of lactation yield in crossbred cows irrespective of season of calving and parity.