tailieunhanh - Báo cáo khoa học: "Associations between the time of conception and the shape of the lactation curve in early lactation in Norwegian dairy cattle"

Tuyển tập các báo cáo nghiên cứu về bệnh học thý y được đăng trên tạp chí Acta Veterinaria Scandinavica cung cấp cho các bạn kiến thức về bệnh thú yđề tài: Associations between the time of conception and the shape of the lactation curve in early lactation in Norwegian dairy cattle. | Andersen et al. Acta Veterinaria Scandinavica 2011 53 5 http content 53 1 5 AVS ACTAVETERINARIA Scatand eaaria SCANDINAVICA RESEARCH Open Access Associations between the time of conception and the shape of the lactation curve in early lactation in Norwegian dairy cattle 1 1 1f 1Ỷ 2Ỷ 3Ỷ Fredrik Andersen Olav 0steras Olav Reksen Nils Toft Yrjo T Grohn 1 Abstract Background This study was carried out to determine if an association exists between the shape of the lactation curve before it is influenced by the event of conception and the time from calving to conception in Norwegian dairy cattle. Lactation curves of Norwegian Red cows during 5 to 42 days in milk DIM were compared between cows conceiving between 43 and 93 DIM and cows conceiving after 93 DIM. Methods Data from 23 049 cows represented by one lactation each with 219 538 monthly test days were extracted from the Norwegian Dairy Herd Recording System which represents 97 of all Norwegian dairy cows. Besides veterinary treatments these records also included information on daily milk yield at monthly test days. The data were stratified by parity groups 1 2 and 3 and higher and time to conception periods 43-93 DIM and 93 DIM . The sample was selected using the following selection criteria conception later than 42 DIM calving season July to September no records of veterinary treatment and the level of energy fed as concentrates between and MJ. The shape of the lactation curves were parameterized using a modified Wilmink-model in a mixed model analysis. Differences in the parameters of the lactation curves with different conception times were evaluated using confidence intervals. Results Lactation curves characterized by a low intercept and a steep ascending slope and a steep descending slope were associated with early conception across all parities. The peak milk yield was not associated with time of conception. Conclusions A practical application of the study results is the use of