GM 19. Age at first calving and its relation to first lactation milk yield, in dual purpose cows

• A. Perez ^[1] ; R. Khalil ^[1] ; Lucia Vaccaro ^[1] ; M. I. Rodriguez ^[1]
  1. [1] Universidad Central de Venezuela

     Universidad Central de Venezuela

     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
• Enlaces
  • Texto completo
• Resumen

  • The objective of the present study was to determine age at first calving in 4 Venezuelan dual purpose herds and its relation to first lactation milk yield. Data were obtained from 763 heifers raised with restricted suckling, grazing and no supplementation. They were milked by hand, with calf, once daily. Only one farm had a fixed criterion for service (>300 kg). Data were analysed with a linear model including the factors farm, breed group (zebu-type, crossbreds with medium or high grades of European inheritance), year (1985..93) and season of birth. The correlations of age with milk yield were calculated within breed groups, within farms and overall. Mean adjusted calving age was 38.3 months, with 32 %, 47 % and 21 % calving before 3 years, at 3-4 years, and after 4 years of age, respectively. The effect of farm was highly significant (P