Efecto del período inter- parto en la curva de lactancia de vacas Holstein friesian en Ecuador.

Abstract

The present research aimed to study the effect of the Inter Calving Period (ICP) on the Lactation Curve (LC) of Holstein Friesian cows in Ecuador, to establish the ICP at the national level, studying the mathematical model that best adjusts the LC, which allows proposing a selection system based on the effect of the ICP on the LC. For this purpose 132, 619 productive data were used and 13 641 reproductive animals were registered by the Holstein Friesian Association of Ecuador _AHFE, on the period 2010 - 2017. Total milk production (Ltotal) and Adjusted at 305 days (L305) were estimated, from the day control productions (DCP) by the method of Fleischman (1945), recommended methodology by the International Committee for Animal Recording _ICAR. The data were analyzed with mixed linear modeling using the PROC GLIMMIX (Generalized linear mixed models). It was evaluated by Inverse polynomial linear function _InvP, and not linear, incomplete Gamma _IG. The estimation of LC parameters was performed employing non-linear regression with the modified Gaussian method Newton at PROC NLIM. The determination of descriptive statistics of the ICP parameter and the LC went through the MEANS procedure in SAS ww.9.4. The results obtained for the ICP were 440.16 ± 16.33 days; the highest production levels were determined at 33.11 days postpartum with a peak production of 19.26 kg milk/day. The best fit curve was by IG model (R² = 0.88), corroborated by the Durbin Watson _DW analytical test equal to 1.73; the phenotypic correlation between ICP and PP was 0.07 (P = 0.6093). It is recommended to select cows that conform to the parameters analyzed such as ICP and LC.