Proceedings of the New Zealand Society of Animal Production. 1997,
57: 43-45
Proceedings of the New Zealand Society of Animal Production. 1997,
57: 43-45
Across-breed estimated breeding values (EBVs) for total lactation milk yield adjusted for days in milk (MYA), unadjusted milk yield (MYU) and days in milk (DIM) of Saanen, Nubian, British, Toggenburg and crossbred dairy goats spread across 20 herds were estimated by Best Linear Unbiased Prediction (BLUP) procedures. A repeatability model was used to analyse lactation yields and included effects of herd-year-month, age, additive genetic merit and permanent environment. Coefficients of breed composition and heterosis (assuming equal heterosis among any of the breeds) and days in milk (MYA only) were considered as covariables. Heritability and repeatability assumed were 0.25 and 0.55. Evaluations were based on 6,517 lactation records of 3,856 does and 83 sires.
Average milk production was 548 l from an average of 200 DIM. Two year old does produced an extra 150 l of milk compared to one year old does. Peak production was at 5 years of age then production declined gradually with age. Young does had longer lactations than old does. Pure-bred Saanen does had more DIM and out-produced other breeds in MYA and MYU. Average EBVs (including breed group effects) for different breeds compared to a Saanen base were for MYU Nubian -291, British -242 and Toggenburg -106 l, MYA -177, -193 and -51 l and DIM -40, -17 and -19 days for each breed respectively. First cross heterosis was 105 l (19%) for MYU, 52 l (9.5%) for MYA and 18 days (9%) for DIM.
This prototype evaluation allows the selection of animals to be used as parents based on their estimated genetic merit and culling of lactating does based on producing ability.
Keywords: NZSAPAB; dairy goats; milk yield; genetic evaluation; heterosis.
