Browsing by Author "Wahlroos, Taru"

Live weight data of cows is needed when preparing feeding plans and monitoring body condition of cows. Live weight is also important in medication; underestimating live weight is a major factor in the development of drug resistance. Live weight of dairy cows has increased in the years 2007–2017. The weight of primaparous cows has increased 21,4 kg (8,8 %), in the second parity 29,2 kg (9,7 %) and in the third parity 34,4 kg (10,8 %). The live weight is affected by both genetics and environment. Higher live weight leads to increased maintenance energy and feed consumption and thereby also increased emissions of greenhouse gases. For these reasons, the body weight should be lowered, or at least its increase should be slowed down. In this study, the objective was to estimate heritability of live weight and body conformation traits in Finnish Ayrshire. In addition, the possibility to include live weight into Nordic Total Merit index (NTM) using breeding values of the frame traits is assessed. From the original data outliers and incorrect observations were deleted. The data were also constrained by fixed effect subclass size. The final data contained 39,550 live weight observations and 12,928 measurements or scores conformation. The heritabilities of this study were: live weight 0,45 (standard error 0,02), stature 0,53 (0,04) and other conformation traits 0,11–0,32 (0,02–0,03). Genetic correlations between live weigh at different ages were very high 0,96–0,98 (0,01–0,03) and the phenotypic correlations were 0,43–0,76. The correlations between the live weight and body characteristics were computed only for the first calving. The genetic correlation between live weight and stature was 0,65 (0,03) and between live weight and other frame traits -0,14–0,59 (0,05–0,09). Based on the results, live weight could be predicted with frame traits. Hence it is possible to calculate the estimates of breeding values to live weight by using the composite index of body characteristics. Adding live weight index into NTM with a negative weight would restrain the growth of cow size.