EFFECT OF TEMPORARY CALF REMOVAL NUMBERS IN TIMED ARTIFICIAL INSEMINATION PROTOCOLS ON WEANING WEIGHT FROM NELORE CALVES

Objetivou-se avaliar os efeitos causados pelo número de remoções temporárias de bezerros (RTB) Nelore durante o protocolo de inseminação artificial em tempo fixo (IATF) sobre o peso a desmama, além do efeito do mês de nascimento e da interação entre eles. Vacas (n = 271) com mais de 30 dias pós-parto foram sincronizadas com o seguinte protocolo de IATF: Dia 0: inserção de dispositivo intravaginal de progesterona + 2,0 mg de benzoato de estradiol; Dia 7: aplicação de 12,5 mg de dinoprost-trometamina; Dia 9: remoção do dispositivo de progesterona + 1,0 mg de cipionato de estradiol + RTB; Dia 11: IATF + retorno dos bezerros as vacas. Os bezerros cujas mães emprenharam após a primeira IATF foram submetidos a RTB apenas uma vez, já aquelas encontradas vazias após 30 dias foram ressincronizadas e seus bezerros foram submetidos a RTB pela segunda vez. O peso à desmama foi ajustado para 210 dias. A análise de estatística foi realizada pelo programa SAS. Não houve efeito do número de remoções temporárias no peso ao desmame (P > 0,05), porém, o mês de nascimento afetou esta variável (P <0,05). Concluiu-se que, o número de RTB em protocolos de IATF durante a estação de monta não afetou o peso à desmama dos bezerros. No entanto, o mês de nascimento afetou o peso à desmama de bezerros de corte, uma vez que aqueles que nasceram no início da estação de nascimento foram mais pesados.

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PSVIII-16 Effect of estrous synchronization with natural service or fixed-timed artificial insemination with conventional or gender-skewed semen in beef females

Journal of Animal Science ◽

10.1093/jas/skab235.773 ◽

2021 ◽

Vol 99 (Supplement_3) ◽

pp. 431-432

Author(s):

Julie Walker ◽

George A Perry ◽

Jerica J Rich

Keyword(s):

Artificial Insemination ◽

Reproductive Efficiency ◽

Weaning Weight ◽

Estrous Synchronization ◽

Sexed Semen ◽

Group A ◽

Timed Artificial Insemination ◽

Calving Season ◽

And Gender ◽

Natural Service

Abstract Reproductive efficiency is critical for profitability, and age at weaning critically impacts weaning weight. The objective was to evaluate estrous synchronization and/or AI with conventional (CON) or gender-skewed (SEXED) semen on calving distribution. Beef females (n=1,620) were either 1) synchronized (7-CIDR:Syn) or not synchronized (Nonsyn) and mated to bulls, 2) synchronized (7-d CIDR) and mated to bulls (SynNS) or artificially inseminated (SynAI), or 3) synchronized (7-d CO-Synch plus CIDR) and AIed with CON or SEXED semen. Calving distribution and gender were determined at birth and were analyzed using the GLIMMIX procedure in SAS. Synchronization resulted in more calves born from d1 to 14 (P < 0.01; 62% vs 47%) of the calving season. There was no differences (P = 0.31) between Syn and Nonsyn in the percent of calves born after d21, but between d22 and 42, more (P = 0.04) calves were born in the Nonsyn group. A greater proportion (P < 0.02; 46% vs 38%) of calves were born in SynNS between d1 and 14 compared to SynAI. There was no difference between treatments (P > 0.12) from d1 to 42, but more calves were born for SynAI after d43. With SEXED semen, there were no differences (P > 0.14) between CON and SEXED for the proportion of calves born from d1 to 14 or d1 to 21; however, more of the desired gender were born in the SEXED group during d1 to 14 of the calving season (P < 0.01; 84% vs 68%). More total calves were born from d22 to 42 in the SEXED group compared to the CON group (P < 0.05; 49% vs 33%). In summary, synchronization increased the proportion of females that calved early in the calving season, and SEXED semen increased the proportion of the desired gender born early in the calving season.

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