Abstract:
The objective of this work was to describe the effect of genetic composition on body condition score (BCS), on total lactation production, and on metabolic and hormone profiles of Holstein x Gyr cows under the same pre- and postpartum management conditions. The genetic groups ½ (n=8), – (n=10), and ≥⅞ (n=10) Holstein x Gyr (HG) were evaluated within the same farm, and all of them showed typical lactation curves. The time required to reach peak production did not differ between groups. The groups also did not differ as to time to reach the lowest BCS after calving or to recover BCS after calving, nor as to their BCS values in the week of first ovulation, number of weeks required for first ovulation, and service period. However, ½ HG cows had higher BCS at calving, but also greater BCS loss postpartum. Total lactation production and plasma insulin concentrations of – HG cows postpartum were similar to those of cows specifically selected for milk production. Using parameters obtained with Holstein cows to determine management conditions in farms with crossbred cows can have unwanted consequences, since these animals have different metabolic and hormone profiles.
Index terms:
Bos indicus; Bos taurus; GH; IGF-1; lactation curve; transition period