Effect of Breeding Protocols and Reproductive Tract Score on Reproductive Performance of Dairy Heifers and Economic Outcome of Breeding Programs

Abstract

The objectives of this study were to evaluate the effect of reproductive protocols and reproductive tract score on reproductive performance of dairy heifers and economic outcomes of breeding programs. Holstein heifers (n = 534), 13 +/- 1 mo of age, were randomly assigned to 1 of 4 reproductive protocols. On the day of enrollment (d 0), heifers were palpated per rectum and received a score according to the maturity of their reproductive tract (1 = prepubertal; 2 = peripubertal; and 3 = puber-tal). Estrous detection-control heifers (CON, n = 146) received no treatment and were inseminated on detection of estrus for 28 d. Prostaglandin F(2alpha)-treated heifers (PGED, n = 137) received 1 injection of PGF(2alpha) on d 0 and were inseminated on detection of estrus; heifers not in-seminated by d 14 received a second injection of PGF(2alpha) and were observed for estrus and artificial insemination (AI) for an additional 14 d. Heifers enrolled in the estrous detection-timed AI (EDTAI, n = 140) treatment received a controlled internal drug-release (CIDR) insert on d 0, and 7 d later, the CIDR was removed and all heifers received an injection of PGF(2alpha), heifers received AI on detection of estrus, and those not inseminated by 72 h after PGF(2alpha) received an injection of GnRH concurrent with AI. Heifers in the GnRH-timed AI (GTAI, n = 111) treatment received 1 injection of GnRH on d 0, on d 6 heifers received a CIDR insert and injections of GnRH and PGF(2alpha), on d 13 the CIDR was removed and heifers received an injection of PGF(2alpha), and 48 h later all heifers received an injection of GnRH and AI. Pregnancy was diagnosed at 32 +/- 3 and 62 +/- 3 d after AI. Cost of reproductive protocols and their economic outcomes were calculated for a 28 d period beginning at enrollment. Heifers in the PGED treatment were inseminated at a faster rate than CON heifers. A smaller proportion of prepubertal and peripubertal heifers were inseminated within 14 d of enrollment compared with pubertal heifers. Pregnancy per AI of CON and PGED heifers was greater compared with EDTAI and GTAI heifers. Proportion of GTAI heifers pregnant at the end of the 28-d breeding program was or tended to be smaller compared with PGED and CON heifers, respectively. Heifers in the CON and PGED treatments had the smallest cost per pregnancy followed by heifers in the EDTAI and GTAI treatments, respectively. When different scenarios were evaluated, however, the mean cost per pregnancy was smallest for PGED heifers. Cost per pregnancy generated was greatest for prepubertal heifers, whereas pubertal heifers had the smallest cost per pregnancy generated. Treatment of dairy heifers with PGF(2alpha) every 14 d until insemination and pregnancy results in the best economic outcomes, and screening heifers according to RTS may prove beneficial to identify heifers that may not be pubertal and would have compromised reproductive and economic performance in a breeding program.

Evaluation of pre-breeding reproductive tract scoring as a predictor of long term reproductive performance in beef heifers

“…A limitation in our data, however, was that different inseminators were used for different parity groups, therefore confounding by inseminator cannot be excluded. In our data, days to calving during the second and subsequent calving seasons did not depend on days to calving of any of the preceding calving seasons (P > 0.05), in contrast to previous findings (Lesmeister et al, 1973, Pence et al, 2007, Stevenson et al, 2008, Cushman et al, 2013.…”

“…In this study RTS predicted the proportion of heifers pregnant and the time to pregnancy during the first breeding season, and to a lesser degree during the second breeding season (Table 4). Other researchers demonstrated that cows that calve early during the first calving season, calve early during subsequent seasons as well and have increased lifetime production (Lesmeister et al, 1973, MacGregor and Casey, 1999, Pence et al, 2007, Stevenson et al, 2008. In a previous report (Holm et al, 2009) we therefore hypothesised that heifers with higher RTS before the start of the first breeding season are likely to calve early during subsequent breeding seasons compared to their herd mates with lower RTS.…”

“…Short term reproductive performance may be predicted by RTS (Andersen et al, 1991, Pence et al, 2007, Holm et al, 2009) and we hypothesised that RTS may predict long-term survival in restricted bred heifers due to its association with pregnancy outcome and days to calving after first breeding, combined with reports that heifers calving early tend to calve early in subsequent seasons and have increased lifetime production (Lesmeister et al, 1973, Pence et al, 2007, Stevenson et al, 2008, Cushman et al, 2013. To the knowledge of the authors, a long-term study of the performance of heifers by RTS category has not been reported.…”

“…Scores 4 and 5 were combined in the analyses, after assuming that both categories were pubertal at the time of scoring (Stevenson et al, 2008), and were used as the reference category in Cox proportional hazards and logistic regression models. It was further assumed that heifers with RTS 3 were peripubertal and that those with RTS 1 or 2 were prepubertal, which were also combined in the analyses (Stevenson et al, 2008). Body condition score (BCS) was determined at the same time by the same operator using a 9-point scale (Marston, 2005).…”

Dairy farm profit according to the herd size, milk yield, and number of cows per worker

“…The difference in the mean age at the first calving between the highest and lowest MY groups was 50 d (Table 1). Many studies suggest that the earlier the age at the first calving the better (Shamay et al 2005;Stevenson et al 2008). Krpálková et al (2014b) concluded that the lowest average milk yield in the lifetime production was observed in the age at the first calving higher than 24.5 months of age.…”