Influence of seasonality, timing of insemination and rectal temperature on conception rate of crossbred dairy cows

Abstract

This study aimed to evaluate the effects of rectal temperature (RT) on conception rate (CR), as well as the effects of seasonality (spring-summer vs. autumn-winter) and timing of artificial insemination (AI) (morning vs. afternoon) on RT and CR in crossbred dairy cows (Holstein x Gyr). The experiment was conducted on a dairy farm in Centralina, MG, where 1.219 conventional and fixed-time inseminations were analyzed. The RT was measured immediately before AI using a digital thermometer. Pregnancy diagnosis was performed using ultrasonography between 28 and 60 days after AI. T The effects of seasonality and timing of AI on RT were analyzed with a Mann-Whitney U test and the effects of RT (above or below the average), seasonality and timing of AI on CR were analyzed with a Chi-squared test, both using the SAS program. The RT average was 39.4°C. Cows with RT ≥ 39.4°C had lower CR than cows with RT < 39.4°C (25.78% vs. 32.54%; P = 0.0096). During spring-summer, cows had higher RT (39.44°C ± 0.025 vs. 39.27°C ± 0.022; P < 0.0001) and lower CR (25.49% vs. 31.75%; P = 0.0146) compared with autumn-winter. Cows inseminated in the morning had lower RT (38.96°C ± 0.022 vs. 39.60°C ± 0.018; P < 0.0001) and higher CR (32.86% vs. 26.06%; P = 0.0102) than cows inseminated in the afternoon. In conclusion, crossbred dairy cows with rectal temperature equal to or greater than 39.4°C had lower conception rate. Moreover, rectal temperature and conception rate were affected by seasonality and insemination time. Key words: Reproduction efficiency, heat stress, artificial insemination, crossbred cows ResumoObjetivou-se avaliar o efeito da temperatura retal (TR) sobre a taxa de concepção (TC), bem como os efeitos da estação do ano (primavera-verão vs. outono-inverno) e do momento da inseminação artificial (IA) (manhã vs. tarde) sobre a TR e a TC de vacas leiteiras mestiças (Holandês x Gir). O experimento foi realizado em uma fazenda leiteira em Centralina, MG, onde foram analisadas 1219 inseminações, tanto convencionais quanto em tempo fixo. A TR das vacas foi medida imediatamente antes da IA usando termômetro digital. O diagnóstico de gestação foi realizado por ultrassonografia entre 28 e 60 dias após a IA.Os efeitos da sazonalidade e do momento da IA sobre a TR foram analisados pelo teste de MannWhitney U e os efeitos da TR (acima e abaixo da média), sazonalidade e momento da IA sobre a TC foram analisados pelo teste de Qui-quadrado, ambos no programa SAS. A TR média encontrada foi de 39,4°C. Vacas com TR ≥ 39,4°C tiveram TC inferior à de vacas com TR < 39,4°C (25,78% vs. 32 P = 0,0096). Na primavera-verão as vacas apresentaram TR superior (39,44°C ± 0,025 vs. 39,27°C ± 0,022; P < 0,0001) e TC inferior (25,49% vs. 31,75%; P = 0,0146) em relação ao outono-inverno. Vacas inseminadas durante o período da manhã tiveram menor TR (38,96°C ± 0,022 vs. 39,60°C ± 0,018; P < 0,0001) e maior TC (32,86% vs. 26,06%; P = 0,0102) do que as vacas inseminadas à tarde. Conclui-se que vacas leiteiras mestiças com temperatura retal igual ou super...

Influence of Season of Calving, Parity and Flunixin Meglumine Administration on Conception Rate in Repeat Breeder Egyptian Baladi Cows and their Crosses

“…Similar trend was observed in crossbred cows during the two seasons. The obtained results agreed with pervious researches (Hossein-Zadeh et al, 2013;Potdaret al,2016;De Souza et al,2016), who found the pregnancy rate was lower (P<0.05) in summer than in winter season in dairy cows. In addition, Ono et al (2016) reported that pregnancy rates were lower in summer (17.1%) than in winter (40.9%).…”

“…Also, several authors reported that higher environmental temperature and relative humidity lead to decline in endocrine activity and lower reproductive efficiency (De-Rensis et al, 2002;Sartori et al, 2002;Sonmez et al, 2005). Recently, Hossein-Zadeh et al (2013), Potdar et al (2016) and De Souza et al (2016) found that the pregnancy rate (PR) of dairy cows was lower in summer than in winter. In addition, Ono et al (2016) reported that PR was lower in summer than winter.…”

Conforto térmico de vacas leiteiras mestiças durante a inseminação e a relação com a taxa de concepção

“…Pires et al (2002) observaram que o ambiente térmico do verão afetou a taxa de concepção de vacas Holandesas (verão: 45,7%; inverno: 71,2%). No estudo de Souza et al (2016) foi observada menor taxa de concepção em vacas leiteiras mestiças (Holandês x Gir) nas estações primavera-verão em relação ao outono-inverno (25,49% vs. 31.75%, p = 0,0146). Os resultados do presente estudo podem ser explicados pela condição de conforto térmico em que os animais estiveram no momento da inseminação artificial, sendo uma das vantagens da técnica em tempo fixo, pois os animais são inseminados nos períodos mais frescos do dia, amenizando o efeito negativo promovido pelo ambiente térmico (Nebel et al, 1994;Chebel et al, 2004).…”

Association between milk urea nitrogen and first service conception in smallholder dairy farms under heat and humidity stress

“…Elsewhere, the proposed effects of high temperature on impaired fertility were reported to be occurring directly and indirectly, as described below [20]. According to the known relationship between body temperature and environmental temperature, hot season disadvantaged follicular development and fetal implantation [20,21]. Moreover, summer months have been shown to lead to reproductive hormone disturbance, deteriorated oocyte development, and early fetal death [19].…”