Oestrous intensity is positively associated with reproductive outcome in high-producing dairy cows

Oestrous intensity is positively associated with reproductive outcome in high-Abstract This study tested whether strong oestrus symptoms are linked to low lameness score, acceptable pregnancy and calving rates in heifers and first parity dairy cows with a high genetic potential for milk production. In a single Swedish nucleus herd for genetic selection and testing, oestrous intensity was determined by detailed observations of 67 females, 25 balanced in terms of age and breed (37 heifers and 30 first-parity cows; 32 Swedish Red cows and 35 Swedish Holsteins). Animals were inseminated with semen of proven quality on the day of detected oestrus. Pregnancy was diagnosed on day 50 by trans-rectal palpation. More heifers than cows exhibited a strong standing oestrus (46 vs. 10%, P<0.05). The pregnancy rate at day 50 was higher among heifers than cows (72 vs. 37%, P<0.01), as well as the 30 calving rate (64 vs. 33%, P<0.05). Standing oestrus was associated with 4.6 to 4.8-fold higher odds of pregnancy and calving, compared to weaker or solely secondary oestrous signs. Lameness decreased the odds of pregnancy 5.1 times and of calving 3.5 times, but no significant association between lameness and oestrus intensity was found. In conclusion, intensive oestrus signalling and non-lameness relate to high reproductive performance in 35 high-producing dairy cattle.