Natural and artificial abiotic factors: impacts on the seminal quality of Dorper rams in a semiarid region

Abstract

The climatic conditions of northeastern Brazil can induce heat stress, reducing the weight, production, and reproductive rates of sheep. This study aimed to analyze the dynamics of abiotic factors, comfort indices on the seminal quality of Dorper sheep under normal local meteorological conditions and adiabatic evaporative cooling. The study involved 20 rams aged 18 ± 2 months, weighing an average of 70 ± 3 kg, raised in a semiarid region of Brazil from April to June 2023. The animals were kept in an open pen for 22 days and for 43 days under the influence of an adiabatic evaporative cooling system (AECS). Air temperature (AT, ºC), relative humidity (RH, %), and black globe temperature (BGT, ºC) were monitored every 15 min daily, with semen collected and analyzed every three weeks, totaling four collections. Thermal characterization of the pen was determined by temperature and humidity indices, black globe temperature and humidity, and specific enthalpy (kJ kg-1). Semen characteristics were analyzed using a completely randomized design with two treatments and 20 replicates, with means compared using the t-test ( p ≤ 0.05). Meteorological variables and comfort indices underwent descriptive statistical analysis. Principal Component Analysis (PCA) was applied to these variables and seminal characteristics. During the driest periods, AECS increased pen RH by 8% and reduced AT by 1.24 °C, maintaining THI values below critical levels. The PCA revealed that only sperm plasma membrane integrity (PMI) significantly responded to environmental changes, increasing by 16% during AECS operation, allowing a regression model with R² greater than 0.72 for estimating PMI.

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