Evaluation of age, weaning weight, body condition score, and reproductive tract score in pre-selected beef heifers relative to reproductive potential

Abstract

Background Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer’s reproductive life span. As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season. Results None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable (‘pregnant to artificial insemination’, ‘pregnant to natural service’, ‘not pregnant’). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination (49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season (89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season, compared to 87.5% if the heifers were older than 368 days. Conclusion Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season. Electronic supplementary material The online version of this article (10.1186/s40104-019-0329-6) contains supplementary material, which is available to authorized users.

Beef heifer fertility: importance of management practices and technological advancements

“…Heifer reproductive success in the first calving season is highly linked with lifetime reproductive efficiency [9][10][11]. A compilation of data from multiple studies demonstrated that first breeding season pregnancy rates in beef heifers range from 64 to 95% under natural breeding (NB) alone or the combination of artificial insemination (AI) followed by NB ( [12][13][14][15][16][17][18][19][20][21][22][23] (Fig. 1)).…”

“…By comparison, first service conception rates to artificial insemination are lower and range from 36% to 69% [12,14,17,18,20,21,23,24]. Our recent analysis of breeding records from 7 yrs (2011-2017) indicated that 43%, 42%, and 15% of heifers became pregnant by AI, NB, or failed to become pregnant during their first breeding season, respectively [23]. Under current production systems, the most efficient scenario occurs when replacement heifers conceive early in the breeding season.…”

Productivity, absence of a bull and endoparasitic nematodiosis in beef cattle farms in an upland area of East Java, Indonesia

“…In industrial beef production setting, among reproductive targets are, age at first mating of 12 months [ 5 ], first calving time of 24 months of age, calving interval of 12 months, weaning rate of >95% of cows, and culling rate of lower than 5% of cows [ 6 ]. In practice, some modern beef farms reach an average first mating time at 13.7 months of age [ 7 ] and a calving interval of 13 months [ 8 ] while pregnancy rate can be varied from 53% to 95% under natural service or reduced to 48-69% when artificial insemination was utilized [ 7 ]. These figures indicate that there are opportunities to improve the productivity of beef cattle farming in the upland area of East Java.…”

Rewiring of gene expression in circulating white blood cells is associated with pregnancy outcome in heifers (Bos taurus)

“…Infertility is a common problem in humans and agriculturally important large mammals. For instance, prevalence of infertility may reach 16% 2 and 15% 3 in humans and beef female calves, respectively. Similar to what has been observed in humans 4 , the genetic architecture of fertility in beef heifers is very complex 5,6,7,8,9,10,11,12 .…”