Parity effects on feed intake and feed efficiency in four dairy breeds fed ad libitum two different diets

Abstract

Parity effects on feed intake and feed efficiency for milk production were analysed in Jerseys, Holstein Friesians, Dutch Friesians and Dutch Red and Whites. These cows were fed at libitum a complete diet of roughage only (R), or a complete diet of the same roughage and 50% concentrates on a dry-matter basis (C), for at least 39 weeks in first and second or in first and third lactation. Of 159 cows in total, 265 lactations were analysed. A significant three-way interaction parity × breed × diet was found, caused by unequal variances between breeds in the different parity × diet groups and by differences in ranking for the breed in the different parity × diet groups. In general, the differences between the C- and R-diet groups decreased with increasing parity. No differences existed between parities in the ratio between milk energy production and net energy intake. Repeatabilities for fat concentration (0.75), protein concentration (0.68) and average body weight (0.69) were high. Repeatability for dry-matter intake (0.39), milk yield (0.47) and biological efficiency (0.46) were lower. Gain during lactation had a low repeatability (0.27).