# Factors at Insemination and Subsequent Conception of Cattle under Heat-Stress Tie-Stall Environments

## TL;DR

This study identifies factors that improve conception rates in dairy cattle under heat stress in tropical tie-stall barns.

## Contribution

The study introduces optimal insemination timing and identifies specific physiological indicators linked to higher conception rates in heat-stressed cattle.

## Key findings

- Insemination 24 hours after estrus detection resulted in the highest conception rate (67.5%).
- Sticky cervical mucus during insemination increased conception risk.
- Higher body temperature and ambient humidity decreased conception chances.

## Abstract

Heat stress, a significant reproductive performance problem for dairy cattle around the world with different mechanisms in each part of the world, is further exacerbated for cattle in tie-stall barns in the tropics due to the challenge of estrus detection. Our research, which we believe to be of significant importance, aimed to determine factors improving conception rates, including secondary estrus signs, reproductive tract characteristics, body temperature, and ambient temperature, during the insemination of cattle in the specified environment. We found that the best rates of conception were achieved when cattle were bred 24 h after initial secondary signs of estrus detection. Sticky cervical mucus during insemination increased conception risk, while elevated body temperature and increased ambient relative humidity decreased it. These findings, which we consider to be crucial, are instrumental in increasing conception rates for cows housed in tie-stall barns, providing valuable insights for dairy farmers in tropical environments.

This research aimed to compare the conception rates among AI at 12, 24, and 36 h after estrus in cattle living in tie-stall barns in a tropical environment. The second study was to determine factors at insemination at 24 h after estrus, including secondary signs of estrus behavior, reproductive tract characteristics, and heat-stress factors, in relation to conception. The study was conducted on 22 tie-stall dairy farms in Chiang Mai, Thailand. After secondary signs of estrus were observed, all farmers were informed for data collection at the insemination time. Repeated logistic regression models were used to determine factors associated with conception. The results revealed that cattle inseminated 24 h after estrus detection had the highest conception rate (67.5%). The study also found that cattle with three or two secondary estrus signs before insemination had a higher risk of conception than those with only one sign. Interestingly, there was an increased risk of conception when sticky or no cervical mucus was observed during insemination (OR = 6.85 and OR = 5.96, respectively). Moreover, increases in body temperature and ambient relative humidity were related to a decrease in the chances of conception. This study recommends delaying insemination to 24 h after the initiation of secondary estrus signs. Multiple signs of estrus, sticky cervical mucus, and lower body temperature increased conception risk in dairy cattle living in tie-stall barns in a heat-stress environment.