Efeito do aumento da concentração de sólidos totais da dieta líquida sobre o comportamento de bezerras

Abstract

The objective of this study was to evaluate the behavior of Holstein ×Gyr crossbred heifers (N = 60) from the 2nd to 13th week of age receiving whole milk with milk replacer powder during the suckling phase, aiming to increase the concentrations of total solids (TS). Heifers were housed in individual hutches and assigned to four treatments (N = 15). Replacer powder was added to whole milk to adjust TS to 13.5, 16.1, 18.2, and 20.4%. Heifers received 6 L/d of the liquid diet, divided into two equal meals (08h00 and 16h00), provided in buckets, from 5 to 55 days of age. From 56 to 59 days, the volume was reduced by half (3 L/d) and at 60 days the calves were weaned. In the post-weaning phase, starting from 70 days of age, corn silage was included in the diet. Behavioral assessments were performed weekly for nine consecutive hours (08h00 to 17h00). In the weaning period (N = 9), evaluations were carried out on the volume-reduction day and remaining days until weaning, at 60 days age, one hour before and one hour after the afternoon feeding, totaling two hours of consecutive assessments (15h00 to 17h00).The number of play behaviors, vocalizations, sucking the hutch or utensils, licking the hutch or utensils, licking the body, visits to the water bucket, urinations, and defecations was observed continuously, considering their frequency of occurrence. We used the scan sampling method with 10-min intervals to evaluate the time spent standing, lying, inside the hutch, outside the hutch, consuming forage, visiting the silage trough, visiting the concentrate trough, ruminating, and idle. The increase in TS content in the liquid diet from the 2nd to the 13th week of age moderately changed the stereotyped behaviors of vocalizing, licking, or sucking the hutch or utensils, though with no defined pattern. During weaning, the treatment with 20.4% TS in the liquid diet resulted in a higher number of play behaviors, shorter duration of standing, and longer time spent ruminating compared with calves fed 13.5% TS in the liquid diet. Irrespective of the TS content in the liquid diet, there was an increase in the number of vocalizations in response to the weaning stress on the 9th week.