Comparison of the pregnancy rates and costs per calf born after fixed-time artificial insemination or artificial insemination after estrus detection in Bos indicus heifers

Abstract

This study compared pregnancy rates (PRs) and costs per calf born after fixed-time artificial insemination (FTAI) or AI after estrus detection (i.e., estrus detection and AI, EDAI), before and after a single PGF2α treatment in Bos indicus (Brahman-cross) heifers. On Day 0, the body weight, body condition score, and presence of a CL (46% of heifers) were determined. The heifers were then alternately allocated to one of two FTAI groups (FTAI-1, n = 139) and (FTAI-2, n = 141) and an EDAI group (n = 273). Heifers in the FTAI groups received an intravaginal progesterone-releasing device (IPRD; 0.78 g of progesterone) and 1 mg of estradiol benzoate intramuscularly (im) on Day 0. Eight days later, the IPRD was removed and heifers received 500 μg of PGF2α and 300 IU of eCG im; 24 hours later, they received 1 mg estradiol benzoate im and were submitted to FTAI 30 to 34 hours later (54 and 58 hours after IPRD removal). Heifers in the FTAI-2 group started treatment 8 days after those in the FTAI-1 group. Heifers in the EDAI group were inseminated approximately 12 hours after the detection of estrus between Days 4 and 9 at which time the heifers that had not been detected in estrus received 500 μg of PGF2α im and EDAI continued until Day 13. Heifers in the FTAI groups had a higher overall PR (proportion pregnant as per the entire group) than the EDAI group (34.6% vs. 23.2%; P = 0.003), however, conception rate (PR of heifers submitted for AI) tended to favor the estrus detection group (34.6% vs. 44.1%; P = 0.059). The cost per AI calf born was estimated to be $267.67 and $291.37 for the FTAI and EDAI groups, respectively. It was concluded that in Brahman heifers typical of those annually mated in northern Australia FTAI compared with EDAI increases the number of heifers pregnant and reduces the cost per calf born.

Maternal periconceptional and first trimester protein restriction in beef heifers: effects on maternal performance and early fetal growth

“…Overall, the pregnancy rate observed in the present study was lower than anticipated but similar to that reported following fixed-time AI (FTAI) programs in nulliparous heifers of B. indicus type that have undergone treatment to synchronise ovulation (36.3% vs 31-40%; Cavalieri et al 2002;Butler et al 2011a;Edwards et al 2015). This relatively poor conception rate following FTAI has been reported to be associated with a high level of ovarian dysfunction (Butler et al 2011b).…”

Effect of the Estrus Expression on Follicular and Luteal Morphofunctional Characteristics and Fertility in Bos indicus females Synchronized for FTAI

“…Sá Filho et al [46], em um de seus estudos, apontaram também que a ocorrência do estro está intimamente relacionada com um melhor desempenho ovariano. Estes achados podem ser explicados pelo fato de os autores observarem que as vacas que manifestaram estro entre a retirada do implante de progesterona e o momento da realização da inseminação, possuírem elevadas concentração de estradiol circulante, associada a maiores dimensões foliculares [6,20,23,26,27,41]. Neste contexto, o papel do estradiol durante esse período foi plurifacetado, exercendo efeito sobre as células foliculares, as quais se prepararam para ovulação e luteinização; sendo crucial para retomada da meiose oocitária; atuou no transporte espermático por meio de contrações uterinas; ajustou o pH uterino, aumentando a viabilidade espermática; e consequentemente, estes fatores favoreceram o sucesso da fertilização [14,18,31,37,40,42].…”

Can cover sheath model influence semen retention in AI-gun trials and pregnancy rates of cows inseminated at a fixed-time?

“…The success of AI programs is often estimated by the number of pregnant females after artificial insemination and by the final cost per calf produced through this technique (Edwards, Bo, Chandra, Atkinson, & McGowan, 2015). Consequently, for an AI program to be truly effective, it must have a great production capacity, which will depend directly on the fertility of the herd and will be influenced by many factors, such as the health of the female reproductive tract and procedures used to conduct the AI technique, in addition to all of the physicochemical events involved in the gametes fertilization (Thomé et al, 2016).…”