Resumo

GALVIS, Rubén D; MUNERA, Edwin A  e  MARIN, Andrés M. Influence of genetic merit for milk production of a holstein herd, on energy balance, metabolic profiles and the postpartum ovarian resumption. Rev Colom Cienc Pecua [online]. 2007, vol.20, n.4, pp.455-471. ISSN 0120-0690.

The aim of this research was to establish the genetic merit for milk yield influence on energy balance, energy metabolic profiles and the postpartum ovarian resumption. In this research, 10 pure-Holstein Friesian dairy cows, varying in genetic merit values for milk yield and fed on a rotational-grazing system with a supplementary concentrate ration were used. A serial of examinations were performed on10.4 (± 2.5), 21.6 (± 4.3), 31.8 (± 4.5), 42.3 (± 4.2), and 51.9 (± 3.9) postpartum days. In every sampling day animals were weighed by tape measure, their body condition score were calculated and the energy balance was estimated for every cow. In addition, blood serum tests were performed to analyze glucose and cholesterol blood concentration and an ultrasonographic assessment was executed to determine ovarian resumption. Nearly all cows had an ovarian resumption on the second week postpartum and more than a half had shown their first postpartum ovulation on the trial period. The genetic merit values for milk yield were not related with production values, therefore, the dependent variables of milk yield did not fluctuated with genetic merit. There was a significant negative relationship (p<0.05) between genetic merit for milk production and the nadir extent of net energy balance (NEB). Although, the genetic merit did not have significant influence on the number of days between calving to the nadir-attaining day, because high genetic merit cows as low genetic merit cows increased the intake and milk yield following similar patterns, but with different extents. In the same way, the genetic merit did not have significant relationship with the interval of calving to first ovulation. Furthermore, no one of the energy balance variables or blood metabolites influenced the interval of calving to first ovulation or the amount of follicles classified by size. In spite of these facts, the ovulating-cow group in the trial period had plasmatic cholesterol concentration significantly higher (p=0.07) and plasmatic glucose concentration significantly lower (p<0.05) than non-ovulating-cow group in the same period. These results suggest that, genetic improvement for milk production could influence the cow energy balance on early postpartum; in spite of these results, the genetic merit for milk production did not affect, by itself, the postpartum ovarian resumption.

Palavras-chave : energy balance; genetic improvement; negative energetic balance nadir; ovulation in cows; metabolic profiles.

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