Effect of the first and next calvings of cows and their milk production level on the relationship between dry period length and milk yield and its composition in the subsequent lactation
The effect cow age and milk production level was analized on the relationship between dry period length and milk yield and composition in the subsequent lactation. The GLM and CORR PEARSON procedures of the SAS package were used in the statistical calculations. It is shown that in terms of milk yield in the subsequent lactation, a dry period of 40–60 days was the most favourable. In particular in primiparous cows it was found that in terms of milk yield, shortening the dry period is less favourable than extending it beyond the 41- to 60-day standard. A dry period of 21–40 days can be offered to multiparous cows without significant milk losses in the subsequent lactation. Eliminating or shortening the dry period should exclude cows after first calving. It seems that a dry period of 21–40 days can also be offered to high-producing cows (≥ 8 000 kg milk) because their milk yield, in relation to cows dried for 41–60 days, was lower by 3.5 %. Shortening the dry period has a positive effect on the concentration of basic milk components such as fat and protein, causing them to increase. Dry period length had no effect on milk lactose content.