Abstract

Lactating dairy cows, either during postpartum anoestrus (LA; n=10) or returned to oestrous cyclicity (LC; n=10), and cycling non-lactating dairy cows (DC; n=10) were superovulated with follicle-stimulating hormone during a progesterone supplementation treatment, inseminated and embryos recovered non-surgically 7 days later. Blood samples were obtained during the period of oestrus to determine plasma concentrations of luteinising hormone (LH). Number of corpora lutea varied (14.6±1.6, 8.1±1.5, and 8.7±1.9 for LC, LA and DC cows, respectively; P<0.02), but not the total number of all ova and embryos, or the total number of transferable embryos per cow. There were no significant differences between groups in either mean time from start of sampling to peak LH (37.0±3.9, 34.5±3.6 and 36.2±4.5 hours for LC, LA and DC cows, respectively) or mean LH peak (12.5±3.6, 16.6±3.3 and 13.4±4.2 ng/ml for LC, LA and DC cows, respectively).

GA, Verkerk, VK Taufa, and R Hooper

Proceedings of the New Zealand Society of Animal Production, Volume 60, Hamilton, 295-296, 2000