Factors Affecting Body Condition Score, Live Weight and Reproductive Performance in Spring-Calving Suckler Cows

The objective was to identify factors affecting live weight (LW), body condition score (BCS), calving rate and calving interval in spring-calving suckler cows. A total of 925 records on 299 cows from the years 1987 to 1999 were used and the data were analyzed using mixed models and generalised estimating equations. Cows calving early in the year (< day 65 of the year) were significantly heavier at the start of winter, had greater BCS at the subsequent calving but lost most LW in winter. Despite having higher LW gain at pasture, annual LW gain of early-calving cows was lower than that of late-calving cows (> day 90 of the year). Trends in BCS were similar to LW but there was no effect of calving date on annual BCS change. Cows in parity 1, 2, 3 to 7 and >7 had initial LW of 523, 549, 614 and 623 kg, winter LW losses of 61, 52, 65 and 67 kg and LW gains at pasture of 81, 99, 94 and 75 kg, respectively. First parity animals had higher BCS at the start of winter but had greater BCS loss in winter and lower BCS gain at pasture than the other three parity groups. Overall pregnancy rate was 93.6% and was not affected by either previous calving date or cow parity. Mean calving interval was 367 days and was affected by previous calving date but there was no effect of either cow parity or previous calving difficulty. Mean calving interval for cows calving early, mid-season or late were 378, 364 and 353 days, respectively. The results show that good reproduction performance can be achieved in spring-calving suckler cows subjected to low feeding levels during the winter period but grazed on well-managed pasture in summer.