What question did this study set out to answer?

The study aims to investigate the impact of heat stress during the peripubertal period on testicular physiology and assess if NCG and MEL supplementation can alleviate these effects.

April 4, 2026

N-carbamylglutamate and Melatonin Supplementation Modulate Testicular Physiology in Peripubertal Rams Subjected to Unmitigated Heat Load

Key Points

The study aims to investigate the impact of heat stress during the peripubertal period on testicular physiology and assess if NCG and MEL supplementation can alleviate these effects.
Subjects included 35 peripubertal Dorper rams divided into three groups by sire and body weight.
Groups were subjected to cooled conditions, heat stress without supplementation, and heat stress with NCG and MEL supplementation.
Testicular artery blood flow, circumference, and temperature were measured using Doppler ultrasound and thermal imaging.
Statistical analysis was performed using MIXED measures in SAS v 9.4.
Testicular blood flow significantly decreased in the heat-stressed group without supplementation compared to cooled controls and supplemented rams.
Final testicular circumference was also reduced in heat-stressed rams without supplementation.
Heat-stressed rams with supplementation maintained testicular weight comparable to controls.
A negative correlation between testicular temperature and blood flow was observed.

Abstract

Abstract Chronic exposure to elevated temperatures affects livestock production and welfare resulting in decreased performance and testicular function during breeding season. Nevertheless, there is a lack of research on the effects of heat stress during the peripubertal growth period. The objective of this study was to identify the effects of heat stress exposure during peripubertal growth on testicular physiology and evaluate if N-carbamylglutamate (NCG) and melatonin (MEL) supplementation could mitigate the adverse effects. We hypothesized that supplementation of NCG and MEL will increase testicular artery blood flow mitigating the effects of heat stress. This study utilized peripubertal Dorper rams (n = 35) placed into 1 of 3 groups balanced by sire, testicular circumference and body weight. These groups consisted of a cooled environment with shade without supplementation (CL-CON; n = 11), a heat stressed environment without supplementation (HS-CON; n = 12), and a heat stressed environment supplemented with 1.4g/h/d of NCG and 8mg/h/d of melatonin (HS-NCGMEL; n = 12). Temperature humidity index was recorded during the trial with an average of 77.23. On day 49, testicular artery blood flow, testicular circumference, and testicular temperature were assessed. Testicular blood flow was evaluated using a Doppler ultrasound, whereas a thermal imaging camera was used to collect testicular temperature. On day 54, rams were slaughtered, and testicular weights were collected. Data were evaluated through MIXED measures using SAS v 9.4. There was a significant difference in testicular blood flow between treatment groups (P = 0.033), where HS-CON had a decreased testicular blood flow (21.90±2.30 mL/min) compared with CL-CON (29.14±2.39 mL/min) and HS-NCGMEL (28.60±2.27 mL/min). There was no significant difference in testicular blood flow between CL-CON and HS-NCGMEL (P 0.05). Final testicular circumference was decreased (P = 0.037) in HS-CON (27.42±0.7074 cm) compared with CL-CON (30.00±0.7389 cm) and HS-NCGMEL (29.75±0.7074 cm), with no significant difference in testicular circumference between CL-CON and HS-NCGMEL (P 0.05). In addition, HS-CON had a decreased testicular weight (414.77±33.18 g) compared with CL-CON (544.45±34.66 g; P = 0.015). However, the testicular weight of HS-NCGMEL rams was not different from any of the aforementioned groups (P 0.05). Lastly, testicular temperature was not different between treatments (P 0.05), although a negative correlation between testicular temperature and testicular artery blood flow was observed (r = -0.46; P = 0.007). An increase in testicular artery blood flow and final testicular circumference in HS-NCGMEL suggests that supplementation of N-carbamylglutamate (NCG) and melatonin (MEL) to heat stressed peripubertal rams enhance testicular parameters.

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