Dry Period in Cattle: I. Influence on Milk Yield and Reproductive Performance

Purpose of this study was to investigate the relations of dry period lengths (DPL) with subsequent lactation (305-d) milk yield (MY) and reproductive performance of Holstein cattle. Data were obtained from 800 Holstein cows raised in a private dairy operation and which were in different parity (2nd, 3rd and >= 4th). DPL was classified in 5 categories as; <= 40, 41-50, 51-60, 61-70 and >= 71 days. The differences in lactation milk yields of experimental DPL groups were not significant. The highest MY (7808.6 +/- 135.1 Lt) was obtained from >= 71 days DPL group and the lowest MY (7529.4 +/- 159.8 Lt) was obtained from <= 40 days DPL group. DPL had significant effect on the number of inseminations resulted in pregnancy (P<0.01). The greatest pregnancy ratio (53.0%) in the first insemination was obtained from <= 40 days DPL group and the lowest pregnancy ratio (30.8%) was obtained from 61-70 days dry period group. There was a positive correlation (0.056) between DPL and 305-d MY and a highly significant positive correlation (0.141) between DPL and the number of insemination resulted in pregnancy. Present findings revealed that longer DPL might have positive effects on lactation MY, but shorter DPL practices might have better outcomes for pregnancy ratios of the first insemination for this farm.