Calving-to-conception interval of dairy cows in a farm in Trinidad and Tobago.

ABSTRACT

Factors affecting calving-to-conception interval (CCI) in dairy cows on a farm in Trinidad and Tobago were studied. Retrospective data from the period January 200 to December 2004 were collected from records (n=178) of the University Field Station dairy herd and analysed using a multivariable regression model. Predictor variables included parity, season of calving [wet vs. dry- dry season (mean rainfall 48.8mm) runs from January to May and the wet season (mean rainfall 194.9mm) from June to December], presence or absence of periparturient disease (PPD), and milk yield. Milk production data were adjusted to an annual yield by correcting the yield between calving intervals to a 365-day production. The natural logarithm transformation of the CCI (LCCI) was fitted as the response of variable in a regression model. The regression coefficients for parity and season of calving were not significant and were 1.4 days longer than females without periparturient disease (P=0.04). Higher milk- producing cows had shorter CCIs. For each kilogramme increase in milk yield, there was a one-day decrease in CCI (P=0.0001). The adjusted R squared was 24% and the predictive regression equation was LCCI=5.22+0.33 (PPD)-0.0001 (milk yield). The findings in this study support the need for more comprehensive investigations at national and regional levels in order to screen for other predictors in an effort to deliver better dairy herd programs health.