Postpartum progesterone profiles in cows with different milk yields

Postpartum progesterone profi les in cows with different milk yields. The aim of the study was to determine progesterone profi les in postpartum dairy cows depending on their milk yield. Analysis was also made of the effect of milk production level and milk progesterone concentration on date of fi rst estrus in cows. The study was performed with two herds of Polish Black-and-White Holstein-Friesian dairy cows. Twenty six cows in the Wielkopolska herd and 17 cows in the Małopolska herd were investigated. The full lactation milk yield of the cows from these herds averaged 9,921 and 7,640 kg, respectively. The cows were kept in a loose-housing system and received TMR diets. Milk progesterone concentration was measured with the FT Multilyser analyser. Milk samples were collected in the morning and evening on days 12, 19, 21, 28, 35, 40 and 42 postpartum. Data on milk yield and milk urea concentration from the fi rst and second test-day milking were taken from RW-2 recording reports. The herd had a statistically signifi cant effect on progesterone concentration in cow’s milk, which for all the tested days averaged 15.5 mg/l in the Małopolska herd and 24.5 mg/l in the Wielkopolska herd. The level of the cow’s daily milk yield had no signifi cant effect on the milk progesterone concentration. Large individual variation was observed between the cows in milk progesterone concentration. The milk progesterone content was negatively correlated with the number of days from calving to fi rst estrus. Daily milk yield had a signifi cant effect on the date of fi rst estrus after calving.