Abstract

The aim of this study was to compare the rate of resumption of oestrous cycles and fertility to first insemination of anoestrous cows examined 7 days before the planned start of mating (PSM), which were milked once (OAD) or twice daily (TAD) for at least 28 days and untreated or treated with progesterone and oestradiol benzoate (ODB; CIDR). By 28 days after the start of treatment, oestrus was detected in 65.8%, 76.6%, 93.5% and 97.9% of cows (TAD, OAD, TAD+CIDR and OAD+CIDR, respectively) (p<0.001). Conception rates to first insemination were lower in CIDR treated than untreated cows (40.4% vs 50.3%; p<0.05), but were not affected by milking frequency. The mean (± sem) interval from PSM to conception was shorter in CIDR treated than untreated cows (12.8 ± 1.2 vs 19.0 ± 1.3 days; p<0.001). Daily milk yield decreased by 6.1 ± 0.2 and 2.2 ± 0.2 litres; and milk solids by 0.46 ± 0.02 and 0.19 ± 0.02 kg (p<0.001) in cows milked OAD and TAD, respectively, over the treatment period. Once daily milking increased the rate of spontaneous resumption of oestrous cycles in anoestrous cows compared with TAD, but was associated with a significant decrease in milk production. Compared to treatment with progesterone and ODB, OAD resulted in a longer interval from PSM to conception.

FM, Rhodes, BA Clark, KL Macmillan, and S McDougall

Proceedings of the New Zealand Society of Animal Production, Volume 58, , 44-46, 1998