Factores reproductivos y su efecto sobre la persistencia de la producción lechera de vacas de raza Jersey en Ecuador.

Abstract

The objective of the research was to determine the reproductive factors of age at first calving (AFC) and the Calving-conception period (CCP), persistency (Per) to study the effect of the AFC and CCP factors on Per, based on these studies to propose a viable animal selection system. Data registered by the Holstein Friesian Association of Ecuador (AHFE) on the period 2010 – 2018 was used. The Total milk production (TOTALM) was estimated by the Fleischmann method (1945). The data were analyzed with mixed linear modeling using PROC MIXED and the descriptive statistics of AFC, CCP, and (TotalM), through PROC MEANS in SAS vw.9.4. For the comparison of the minimum mean square, the Tukey-Kramer test (1956) was used. Also, for the contrasts of orthogonal to detect the linear, square, and cubic effects. Per was estimated according to the criteria of Johansson and Hansson (1940). It is concluded that the AFC was, 30.61 ± 0.67 months, CCP, 120 ± 0.96 days, TotalM, 2977.55 ± 64.44 kg; milk production adjusted to 305 days (AdjustM), 3009.52 ± 151.24 kg; Per, 41.79 ± 0.74%. The estimated correlations between Per and AFC were -0.5421 (P = 0.2665) and, between Per and CCP, 0.1082 (P = 0.3911). The phenotypic value of the AFC and Per was -0.0626 ± 0.0957 (P> 0.5596) and, of the CCP and Per was -0.6968 ± 0.4502 (P>0.2194). The use of the methodology generated in this study is recommended for the selection of Jersey cows in the production of milk in Ecuador.