Alternatives to monthly sampling in herd recording

Abstract

Two investigations were made in South Australia to assess the accuracy of methods alternative to monthly sampling in herd recording. In the first, lactation records for 15,482 cows completing lactations in 1971-72 and tested monthly at that time were examined. The average lactation yields were 3988 kg, 3974 kg, 4033 kg, 3971 kg and 4004 kg for monthly testing, bimonthly testing (even months), bimonthly testing (odd months), alternate p.m.-a.m. testing, alternate a.m.-p.m. testing respectively. Only 5 per cent of all alternate p.m.-a.m. and alternate a.m.-p.m. estimates differed by more than 5 per cent from monthly estimates, whereas 12.3 per cent of bimonthly (even) and 19.7 per cent of bimonthly (odd) estimates differed by greater than 5 per cent. The second investigation was made over six months using a Research Centre herd to determine the accuracy of alternate a.m.-p.m. sampling for milk fat and milk protein. Cows recorded six times gave average fat percentages of 3.56, 3.65 and 3.60 under alternate p.m.-a.m., alternate a.m.-p.m. and monthly testing schemes. Average protein percentages were 3.47, 3.44 and 3.46 respectively. It is concluded that alternate a.m.-p.m. sampling could be satisfactorily adopted as an alternative method of sampling in herd recording,