Friesian cows of high (126) or low (104) breeding index (BI) were differentially fed during late gestation, early lactation and late lactation, and milkfat (MF) yield and condition score (CS) responses measured. In 40 cows fed to calve in either thin (CS=4) or fat (CS=5.3 in 1981; CS=6.0 in 1982) condition, a similar non-significant response to extra CS at calving was observed in both BI groups (3.0 to 8.6 kg extra MF/extra CS). For up to 4 weeks in early lactation, 24 and 32 cows in 1982 and 1983 respectively, were offered either restricted (12 to 15 kg DM/cow) or generous (50 kg DM/cow) daily allowances of pasture. Feed restriction reduced daily MF yields by 0.2 to 0.4 kg/cow, but subsequent production recovered rapidly. The extent of this recovery was less for cows of low than for cows of high BI in 1983 but not in 1982. In weeks 27 to 30 of lactation in 1983, 24 cows were offered either restricted (18 kg DM/cow) or generous (80 kg DM/cow) daily allowances of pasture. In weeks 28 to 31 of lactation in 1984, 32 cows were offered 30 kg pasture DM daily, either with or without a daily supplement of 5 kg of concentrates. Feed restriction reduced daily MF yields by a similar extent for both BI groups (0.2 to 0.3 kg MF/cow) and recovery during the final 6 weeks of lactation was similar for both groups.
Proceedings of the New Zealand Society of Animal Production, Volume 45, , 1-6, 1985
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