9 COMPARATIVE EFFICACY OF AN 8-DAY Cue-Mate^®/ESTRADIOL BENZOATE PROGRAM WITH OR WITHOUT INCLUSION OF EQUINE CHORIONIC GONADOTROPIN IN ANESTROUS DAIRY COWS

Abstract

The objective was to quantify and compare the reproductive response of lactating, seasonally calving dairy cows diagnosed with anovulatory anestrus (AA) to treatment with two separate progesterone (Cue-Mate^®, Bioniche Animal Health, Australasia, Armidale, NSW, Australia) and oestradiol benzoate (ODB) treatment regimes, either including or excluding eCG. Cows on six commercial seasonal-calving dairy farms in New Zealand (n = 2355) were presented following 3 weeks of tailpainting and a subsequent non-observed estrus. Cows which were confirmed in anestrus with no detectable corpus luteum (CL) by rectal palpation were selected for trial inclusion (n = 1382). All cows received the standard anestrous protocol, consisting of an 8-day insertion of the progesterone device containing 1.56 g of progesterone (Cue-Mate; injection of 2 mg of ODB at the time of insertion and further injection of 1 mg of ODB 24 h after Cue-Mate removal (Day 9)). Approximately half of the cows were randomly allocated (using the RAND function within Excel, Microsoft) to a further intervention consisting of an injection of 400 IU of eCG (Pregnecol^®, Bioniche) on the day of Cue-Mate removal (Day 8). This became the Treatment group with the standard treatment the Control group. Cows were then mated to detected heats; all cows not detected in estrus and inseminated were blanket-mated 36 h after the second ODB treatment. Cows were scanned ultrasonically 10 weeks post-treatment and all pregnancies were aged to the nearest half-week. Where two matings were recorded within 7 days of each other, the later mating was used. Data were analyzed using both a matched logistic regression analysis and survival analysis, using SPSS (SPSS.com) and SAS (SAS.com). Pregnecol-treated cows were more likely to conceive in the first 48 h following treatment (48.84% v. 43.10%; P = 0.06), and were more likely to be in calf within 7 days following treatment (P = 0.07). The effect of Pregnecol was greater in cows over 5 years of age, such that this stratum of cows was significantly more likely to conceive within 48 h [58.33% v. 38.10%; P = 0.00; adjusted relative risk (RR) 1.51; 95% lower confidence interval (LCI) 1.15; 95% upper confidence interval (UCI) 2.00], and was significantly more likely to be in calf within 7 days (55.20% v. 37.86%; P = 0.00; RR 1.44; LCI 1.41; UCI 1.82). Pregnecol-treated cows over 5 years of age were significantly more likely to be in calf at 4 weeks (72.22% v. 59.57%; P = 0.02; RR 1.21; LCI 1.03; UCI 1.42). Cows that had calved less than 50 days were significantly less likely to be in calf by 4 weeks (62.26% v. 69.35%; P = 0.04). In summary, the addition of a 400 IU treatment of eCG (Pregnecol) at the time of Cue-Mate removal in a standard 8-day progesterone device/ODB anestrous treatment program increased the risk of pregnancy. The effects of eCG on cows over 5 years of age were very strong and highly significant.