CHANGES IN PERFORMANCE AND IMMUNE RESPONSE IN DAIRY CALVES OFFERED MILK REPLACER OR RAW MILK

Abstract Text: The objective of the present study was to compare intake, growth performance, and immune response in dairy calves fed milk replacer (MR) or raw milk (RM). Seventy dairy female Holstein calves were randomly assigned to either MR or RM treatments and were offered 750 g/d of MR or RM respectively from days 15 to 56 and 375 g/d from 56 to 63 d of life. All the calves were weaned at day 63 and starter feed was offered ad libitum throughout the study. Daily milk and feed intake was recorded from days 2 to 63. Animals were weighed weekly and blood samples were collected at days 14, 28, 42 and 56 to determine glucose and insulin concentrations. Immune response was evaluated in blood samples collected at 35 d of age by measuring TNFa after an in vitro lipopolysaccharide (LPS) challenge in blood. Also, at days 7, 21 and 35, 1-ml of ovoalbumin was injected to calves and blood samples were collected at day 7 and 56 to measure antibody titers against ovoalbumin. Data were analyzed using a mixed-effects model with repeated measures. Data from insulin and insulin to glucose ratio were previously transformed to reach a normal distribution. No differences were found in milk or feed intake, ADG or gain to feed ratio between treatments. Plasma glucose concentrations did not differ between treatments but, plasma insulin concentration was greater (P < 0.05) in MR compared with RM calves (1.36 vs 0.78 ± 0.053 µg/L) as it also was the ratio insulin to glucose (0.12 vs 0.07 ± 0.535). Immune response to the in vitro LPS and the in vivo ovoalbumin challenges were similar in both groups. However, RM calves needed to receive antibiotic treatments (24%) fewer times (P < 0.05) than those fed MR (37%). In conclusion, even no significant differences were found in intake or growth performance, the lower insulin to glucose ratio and the decrease in the number of antibiotic treatments in RM calves compared with those fed MR, suggested an improvement on glucose metabolism, and a potential benefit on calf health when feeding RM to calves compared with feeding MR.

Keywords: calves, performance, raw milk