Variability impact weather of Mexico humid tropical regions on pregnancy rate of in vitro produced bos indicus embryos
DOI:
https://doi.org/10.5965/22381171e28178Keywords:
Embryo transfer, Heat stress, Temperature-humidity index, Corpus luteum, Embryo recipient, CowsAbstract
Livestock production in the humid tropical regions of Mexico faces several changes derived from weather variability, particularly heat stress, measured by the temperature humidity index (THI), which compromises reproductive efficiency. The aim of this study was to evaluate the impact of environmental variables on the pregnancy rate (PR) of embryo recipient cows (RC) to which Bos indicus embryos, in vitro produced (IVP), were transferred. 3610 embryo transfers were analyzed (2021-2024) in the humid tropics. Temperature, relative humidity, rainfall and prevailing winds were measured, and the THI was calculated and categorized (comfort, alert, danger, emergency). Pregnancy was verified through ultrasound scan (45-50th day) after the embryo transfer. χ² tests, logistic regression and multivariate analyses (Principal Component Analysis, PCA) were applied. Global PR was 40%. According to the annual analysis, 2023 had the highest rate (47.9 %) and the lowest were observed in 2021-2022 (37-38 %). In the seasonal analysis, winter and fall registered the best results (43-44 %), while the least favorable season was summer (34.9 %). Dry period showed better results than rainy (42.7 % vs. 37.8 %; p<0.05). Big corpus luteum (CL3 ≥25 mm) were associated with greater successful PR (p<0.05). The logistic regression indicated a reduction from 56.8 % (THI 59.1) to 32.2 % (THI 87.4) in the possibility of a successful pregnancy. PCA explained 61.6 % of the variation, showing a negative correlation between PR and Temperature. Weather variability in the humid tropics of Mexico reduces the efficiency of in vitro embryo transfers under extreme heat and humidity conditions. These findings provide a basis for seasonal management and reproductive biotechnology adaptation strategies under tropical climates.
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