Lactation productivity of dairy cows as affected by the length of preceding dry period

摘要

The effect was analysed of the length of preceding dry period on milk, fat and protein yield and somatic cell count (SCC) in forthcoming 305-day lactation of cows kept under the welfare condition. Four groups of dairy cows were distinguished based onlength of their dry period: A - up to 30 days, B - 31-60 days, C - 31-90 days, and D - 91 and more days (25,71,39 and 25 lactations, respectively). The highest milk, fat and protein yield (305 - days) was observed in group C. In groups A, B and D milk yield was lower by 16.39%, 12.59% and 13.40% than in group C, respectively. Differences in milk and protein production between groups were statistically significant (P<0,01) for group pairs with group C with highest yield. Fat production in group A was lower by 6.06%, in group D by 5.37 % and in group B by 1.01%. Protein production in group A was lower by 14.12%, while in group D and B by 12.84% and 9.78%, respectively. Effect of SCC on milk, fat and protein yield was also investigated. Decrease in milk,fat and protein yield was accompanied by the SCC increase. The level of SCC was related to the lactation parity. Shortening of the dry period below 30 days had negative effect on percentage of milk samples with SCC below 400,000/ in dairy cows with fourth and further lactations.