Abstract:
386 Proc. Aust. Soc. Anim. Prod. Vol. 17 REPRODUCTIVE PERFORMANCE OF DAIRY HERDS IN NORTH EAST VICTORIA R.T. CURRIE* AND P.L. BRIDGE* The dairy herd management practice of concentrating calving patterns has been the focus for mating management programs over the last decade in Victoria. Calving cows over a six to eight week period produces benefits to management as well as potential financial gains (Currie 1985 ). In 1985 a survey was conducted in North East Victoria to establish and describe the level of dairy herd reproductive performance and management practices. Data were gathered from 38 randomly selected farms, representing about 8% of dairy herds in the region. The method used to describe calving spread was developed in New Zealand by McMillan (1985) and involved dividing the calving pattern into four intervals. These four intervals were; (i) Planned Start of Calving (PSC) to Mid-point (MP). MP is the date on which half of the cows in the herd (excluding first calvers) had calved; (ii) MP to 75%; (iii)75% to end-of-calving (when 95% of the herd had calved) and (iv) total calving spread (TCS, the interval between PSC and end-of-calving). Table 1 Mean reproductive performance data from 38 dairy herds (Av 102 cows) in North East Victoria. Figures in brackets are Standard Deviations The average TCS was around 13 weeks (91 days), although farmers indicated they wanted to have their herds calve within eight weeks (56 days). The results from the survey revealed that cows either in-calf or recently calved when mating commenced reduced the submission rate of the herd., A comparison between herds with the shortest TCS and the rest, revealed that fewer farmers within the top 20% used calving induction, and those that did, used it earlier (7 weeks after calving started cf 11 weeks). Seventy per cent of the top group,mated cows on their first heat after calving compared with 48% for the remainder. There was no significant difference between first service NRR of the two groups. CURRIE, R.T. (1985) Dairy Industry Newsletter 2~8 McMILLAN, K.L.(1985) Proc. Conf. The Challange: Efficient Dairy Production. Aust. & N.Z. Soc. Anim. Prod. 297. * Department of Agriculture and Rural Affairs, P.O. Box 551, Wodonga, 3690.