Effect of season and breed group on the follicular population and cyclicity of heifers under tropical conditions

• Published in: Tropical animal health and production 2017, Vol.49 (1), p.207-211
• Main Authors: Peralta-Torres, Jorge Alonso, Aké-López, Jesús Ricardo, Centurión-Castro, Fernando Gerardo, Segura-Correa, José C.
• Format: Article
• Language: English
• Subjects: Animals; Biomedical and Life Sciences; Body Weight; Breeding; Cattle; Climate; Corpus Luteum - physiology; Female; Humidity; Life Sciences; Mexico; Ovarian Follicle - physiology; Regular Articles; Seasons; Temperature; Variance analysis; Veterinary Medicine/Veterinary Science; Zoology
• ISSN: 0049-4747; 1573-7438
• DOI: 10.1007/s11250-016-1182-7

The aim was to determine the effect of season and breed group on follicular population, and presence and size of CL of heifers under tropical conditions. The seasons were hot-dry (March–June), hot-humid (July–October), and fresh-humid (November–February). Thirty Zebu (Brahman) and 38 F1 (Simmental × Brahman) heifers were used. Five evaluations were made in each season, at intervals of 7 days, to assess ovarian activity by ultrasound. Follicles were classified as small (≤4 mm), middle (4.1–8 mm), and large (≥8.1 mm) sizes, and also the size of CL, when present, was measured. Data were analyzed using analysis of variance and logistic regression procedures. Mean number of small follicles was 11.6 ± 2.3 with no effect of season, breed group, or their interaction ( P  > 0.05). Mean number of middle follicles was influenced by season and breed group; the highest average was found in the fresh-humid season (4.0 ± 0.2) and in F1 heifers (3.6 ± 0.2; P