160 Sarda ram management throughout the reproductive season significantly affects their body condition score and metabolic status

During the breeding season of Sarda dairy sheep (June–December), a fertile adult ram can serve at least five ewes daily. In this period, rams are exposed to changes in housing conditions, feeding regimens, social environment, and ambient temperatures. The aim of this study was to evaluate fluctuations in body condition score (BCS) and metabolic status of Sarda rams, during the breeding season, using the circulating concentrations of nonesterified fatty acids (NEFA), urea, triglycerides, and cholesterol and fecal levels of thyroid hormone metabolites (FTMs). Testicular width (ultrasonographic measurements) and tone were also assessed. For this purpose, 21 Sarda rams (2–6 years of age) were examined five times from June to December at ~40-day intervals. All rams received three subcutaneous slow-release melatonin implants (18 mg; MELOVINE® Ceva Salute Animale SPA) between early April and late May to advance mating and increase their fertility rate. Body condition scoring assessed the muscling and subcutaneous fat development on a scale from 1 to 5 (1, emaciated; 2, thin; 3, average; 4, fat; 5, obese), and testicular tone was evaluated by palpation using a 3-point scale (1, soft; 2, intermediate; 3, rigid). Circulating concentrations of blood metabolites were determined with commercial kits (Real Time Diagnostic Systems) and the BS-200 Mindray clinical chemistry analyzer (Adaltis), and FTMs were analyzed by DiaMetra Srl. Statistical analyses used R software to determine the differences in the metabolic and hormonal variables using one-way repeated-measures ANOVA and Tukey HSD test. P-values < 0.05 were considered statistically significant. Mean BCS of rams was greater (P < 0.001) in July (3.10 ± 0.06) than in September (2.87 ± 0.06) and November (2.88 ± 0.06). Circulating concentrations of NEFA and cholesterol peaked (P < 0.001) in November (0.42 ± 0.06 mM and 51.6 ± 1.9 mg dL⁻¹, respectively) and were lowest in September (0.14 ± 0.06 mM and 42.0 ± 1.9 mg dL⁻¹, respectively) and December (0.13 ± 0.06 mM and 42.8 ± 1.9 mg dL⁻¹, respectively). Blood levels of triglycerides were lower (P < 0.05) in November (17.7 ± 2.02 mg dL⁻¹) than in July (25.7 ± 2.02 mg dL⁻¹) and December (26.8 ± 2.02 mg dL⁻¹). Mean urea concentrations were higher (P < 0.0001) in June (23.9 ± 1.3 mg dL⁻¹) and July (23.7 ± 1.3 mg dL⁻¹) than during all other months (17.1 ± 1.3, 17.9 ± 1.3, 14.5 ± 1.3 mg dL⁻¹ for September, November, and December, respectively). FTMs were higher (P < 0.001) in June (82.5 ± 4.7 ng g⁻¹ feces) than in July (61.9 ± 4.7 ng g⁻¹ feces) and December (55.8 ± 4.7 ng g⁻¹ feces). The mean testicular tone was lower (P < 0.0001) in July (1.48 ± 0.14) compared with June (2.19 ± 0.14) and November (2.2 ± 0.14). Lastly, the mean testicular width was less (P < 0.0001) in September (4.77 ± 0.10) than in June (5.22 ± 0.10), July (5.13 ± 0.10), and December (5.15 ± 0.10). Our present observations indicate that rams’ BCS, metabolic status, and testicular size/tone change significantly during the breeding season. A significant decline in the metabolic status occurred in the last month of the breeding season when Sarda rams are typically used for mating yearlings. These fluctuations can potentially impinge on rams’ reproductive efficiency and hence flock fertility.

This study was supported the Italian Ministry of Research and Education under the National Recovery and Resilience Plan (project “Ecosystem of Innovation for Next Generation Sardinia” [ECS 00000038]).