Dry period length and performance of cows in the subsequent production cycle

Abstract. The effect of dry period length on performance in the next production cycle was investigated in the active population of cows from the Pomerania and Kuyavia regions of Poland. Dry length period of the cows was calculated and classified (0, 1–20, 21–40, 41–60, 61–80, 81–100, >100 days). The GLM, FREQ and CORR PEARSON procedures of the SAS package 9.1 were used in the statistical calculations. The problem of dry period length was found to be debatable. A dry period of 40–60 days would be the most favourable in terms of milk, fat and protein yield in the next lactation, the course of parturition and the proportion of calves born alive, and a dry period of 21–60 days would be the most beneficial in terms of the proportion of cows surviving the next production cycle. Extending or shortening the standard dry period of 40–60 days by 20 days causes a slight decrease in performance determined by the above parameters, whereas extending and especially shortening the dry period by another 20 days, or the absence of a dry period, have a severely negative effect. Compared to cows that had been dry for 40–60 days, the cows whose calving was not preceded by a dry period had lower lactation yield (by 25 % for milk, by 24 % for fat and by 20 % for protein), lower daily milk yield (by 22 %), were significantly more prone to miscarriage, and more frequently gave birth to dead calves, calves with physical defects or grossly malformed calves. Too long a dry period (beyond 100 days) may carry a risk of higher culling levels in the herd, shorter lactations, health abnormalities, and poorer reproductive performance.