Effects on Synchronization and Reproductive Efficiency of Delaying the Removal of the Intravaginal Progesterone Device by 24 h in the 5d Co-Synch Protocol in Heifers

Abstract

In beef herds, increasing animal welfare, improving reproductive performance and easing animal management are key goals in farm economics. We explored whether delaying the removal of the intravaginal progesterone device by 24 h in heifers synchronized with a 5d Co-synch 72-h protocol could improve reproductive efficiency of fixed-time artificial insemination (FTAI). In experiment 1, we examined the total synchronization rate (TSR) in cycling Holstein heifers. Heifers (13.4 ± 0.69 mo.) were randomly assigned to the standard 5d Co-synch 56-h protocol (5dCo56; n = 10), 5d Co-synch 72-h (5dCo72; n = 17), or the modified 5d Co-synch 72-h protocol, in which removal of the progesterone device was delayed by 24 h (6dCo48; n = 19). In experiment 2, 309 cycling beef heifers on 18 commercial farms were subjected to the 5d Co-synch 72-h or 6-d Co-synch 48-h protocol and conception rate (CR) studied. In experiment 1, the three protocols led no differences on TSRs of 80.0% (5dCo56), 88.2% (5dCo72), and 89.5% (6dCo48). In experiment 2, the CR from the beef heifers, observed during two consecutive reproductive seasons did not differ: 59.7% for 5dCo72 and 62.0% for 6dCo48 (p = 0.907). Therefore, delaying removal by 24 h provides satisfactory results without reducing reproductive efficiency of heifers.

MOET Efficiency in a Spanish Herd of Japanese Black Heifers and Analysis of Environmental and Metabolic Determinants

“…Another study [ 27 ] described an average CR after AI of 47.0% in heifers and 47.8% in adult cows, with first, second, and third AIs leading to higher CR values than fourth or subsequent AIs. Higher CRs have been reported for other beef breeds in Europe, such as 59.3% [ 28 ] or 63.6% [ 29 ] for Angus, 63.6% for Charolais, 63.2% for Limousine, and 56.9% for cross-breeds [ 30 ]. Embryo transfer appears to work reasonably well in the Japanese Black breed: in one study, 685 oocytes were collected from 8 multiparous Japanese Black cows and 120 embryos were achieved after in vitro fertilization (IVF), and transferring 36 such embryos into Holstein heifers led to 20 pregnancies [ 31 ].…”

Controlled breeding in dairy cows. Part 1: bovine oestrus cycle and synchronisation

“…While pregnancy rates were optimised, between a fifth and a third of heifers were found to display oestrus and require insemination before the planned time of insemination (Silva and others 2015). For this reason, a modified protocol was devised, dramatically reducing the odds of early oestrus behaviour, while maintaining similar pregnancy rates (Rodriguez Fernandez and others 2017, Fernandez‐Novo and others 2021) (Fig 11).…”