Live weight changes during lactation in Montbéliarde cows

Anotace: This research was conducted on 147 cows of purebred Montbéliarde dairy cattle during their first to seventh lactation. On average, each dairy cow provided 161 values on live weight during lactation via the automatic milking system (AMS). The average live weight of a dairy cow of said herd was 699.94 kg, the daily milk yield was 33.67 kg on average and the average day of lactation (DIM) was 111.75. This research discovered a statistically significant decrease of live weight in dairy cattle before the 60th day of lactation in every observed lactation. On the contrary, the changes in live weight in the last 60 days of standardized lactation proved to be inconclusive. Between days 60 and 240 of the lactation, an increase of live weight of varying intensities was observed, mainly in cows who had undergone less lactation cycles in the past. Similarly, the research has proven an impact of the number of lactation cycles the cow has undergone in the past on the live weight of the cow during the first, second and third lactation (645.21 kg, 700.35 kg and 752.10 kg respectively). On the contrary, there was no conclusive difference in live weight between the third and more lactation cycles. The results have also shown that the changes in live weight during lactation were significantly different in first-calf heifers, as opposed to cows after more lactation cycles, similarly to the differences in milk yield.