FR 02. Forty five days breeding season. I: Reproductive performance of heifers

• Dario Montoni ^[1] ; J. R. Vitto ^[1] ; G. Rojas ^[1] ; J. Parra ^[2] ; Milena M. de Montoni ^[1]
  1. [1] Universidad Nacional del Tachira, Venezuela
  2. [2] Fondo Ganadero del Suroeste Andino, Venezuela.
• Localización: Archivos Latinoamericanos de Producción Animal, ISSN 1022-1301, ISSN-e 1022-1301, Vol. 5, Nº. Extra 3, 1997 (Ejemplar dedicado a: Proceedings XV ALPA meeting 2)
• Idioma: inglés
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• Resumen

  • This research was conducted on 272 Brahman heifers at Santa Rosa Ranch located in the humid tropic at the southwest region of Táchira State, Venezuela. Heifers were kept on pasture and supplemented with minerals. The main objective was to evaluate the pregnancy rate (PP, n = 272) and date at first calving (FP, n = 210) of heifers submitted to 45-days-breeding season beginning on march the first (E, n =163) vs the conventional 90-days starting on april the first (C, n = 109). Least-squares analysis of variance were performed on traits including: Treatment (T:E,C), year of mating (A: 1984, 85, ..., 92), heifer’s sire (P:1,2,...,22), T x A, condition score (BC) and linear regressions of heifer’s weights at 720 days (W720) and mating time (WM). Adjusted means for PP and FP were 76.2 (2.0 days, affected by T and A (P < .01). E was 23 and 81 % more efficient. A short calving period was achieved in the E group with 94 % of calves borned prior to january 30th vs 30 % in C. Erratic tendency showed A. BC and WM affected PP (P