Influencia del tamaño y otras medidas relacionadas con la eficiencia productiva y reproductiva en vacas holstein. Resumen de tesis

Abstract

This work was performed in Tocancipa (Cundlnamarca, Colombia) using 281 Holstein cows with ages ranging from 3 to 10 years. Measurements made reflect body and pelvic size, production efficiency (milk production and composition) as well as reproduction. A two size classification was made according to weight related with thoracic perimeter and age of specimen. Also variate analysis, Duncan tests and variate correlation coefficients were performed. The following aspects were graphically recorded: average production on month/day basis according to age groups, production and reproduction. Studied population average weight was 557 Kg., being the younger cows the heaviest. The largest cows surpassed thoracic perimeter, stature, body lenght as well as pelvic measures but differences were not significant among size and age groups (R : 0.50) excepting for pelvic depth. It was found that milk production (305 days/mature age) was higher among medium size cows for all size/age groups, and average weight of 390 Kg. per lactancy, Milk analysis gave the following results: 3.5% fat, 8.7% non fat solids, and 1.0307 density value in average. As for reproduction area, the cows were covered early (age: 20 months). Medium size cows required the highest mounting rate for conception (2.4). Gestation time was constant for both size groups (283±2 days). Dry and open periods were higher among medium size cows when compared with large size ones on age groups. Intervals between births before actual lactation were high for medium size cows lees than 5 yrs./age as well for large cows more than 5 yrs./age, even If not significant among all variate size (R: 0.50). Birth rate was high (98%) In both sizes and female births percentage (51% ) was high among large size cows when compared with all groups. Correlation coefficients for variates among body, productive and reproductive types when combined reported significance in some cases (Pi0.05 and P10.01) according to size/age but most of the cases were not significant proving that association among them is affected by factors such as age, size, environment, etc. Referring to graphical relation between lactancy and dru period It Is noticeable that production Increased as the period elapsed for large size cows. For medium size cows production Increased as the open period elapsed. For the same group Interval between actual lactation Increased production as the Interval Itself was doing the same. Opposite sizes showed lower levels and after that they increased production when dry days, open days and intervals between births also Increased.