Controlled field study investigating effects of 2 methods of enriching moderate-quality maternal colostrum on transfer of passive immunity and well-being of neonatal dairy calves

Enriching low- or moderate-quality maternal colostrum (MC) by directly adding dry commercial colostrum replacement (CR) powder into MC is convenient, but it is unknown whether this may increase osmolality of the CR-MC mixture to levels that could potentially interfere with gut motility and calf health. Conversely, first reconstituting CR in water before mixing into MC should not increase osmolality but will result in a greater final volume to deliver to the calf. Our major objective was to describe the effect of either mixing dry unreconstituted CR powder directly into moderate-quality MC, or first reconstituting CR with water before mixing into moderate-quality MC, compared with feeding unenriched moderate- or high-quality MC, on calf serum IgG levels at 24 h. Secondary objectives were to investigate the effect of colostrum treatments on calf behavior during and shortly after colostrum feeding, and on appetite, health, and growth during the 3 d following birth. The study was conducted on a large commercial dairy in Minnesota. Each day, study technicians used a Brix refractometer to create 1 batch of moderate-quality MC (MC60; target ≈60 g/L IgG) and 1 batch of high-quality MC (MC90; target ≈90 g/L IgG). Following heat-treatment, MC60 and MC90 colostrum were frozen in 3-L or 3.8-L aliquots, intended to feed small and large calves, respectively. Eligible newborn calves were randomized to 1 of 4 colostrum treatments (33/group) delivered by esophageal tube feeder within 2 h of birth: moderate-quality MC (MC60), high-quality MC (MC90), dry CR powder mixed directly into moderate-quality MC (CR-MC60), or CR reconstituted in water before mixing into moderate-quality MC (CR-H2O-MC60). Total IgG dose fed was adjusted for small and large calves, respectively, with the goal being for the 2 CR-enriched groups to match the total IgG dose delivered to the MC90 group. Calf behavior was recorded via video during colostrum feeding and for 1 h following colostrum delivery in a subset of calves. Blood was collected from all calves at 24 h to measure serum IgG (g/L). Appetite and health scores were recorded daily for 3 d following enrollment, and calves were reweighed on d 3. Ranked from lowest to highest, mean serum IgG levels were 34.2 ± 1.2, 36.5 ± 1.2, 38.1 ± 1.1, and 40.4 ± 1.2 g/L in the MC60, CR-H2O-MC60, CR-MC60, and MC90 groups, respectively, with levels in both the MC90 and CR-MC60 groups statistically exceeding those in the MC60 group, and levels in the MC90 group statistically exceeding those in the CR-H2O-MC60 group. Neither approach to enriching moderate-quality MC negatively affected calf behavior, appetite, health, or growth in the first 3 d following enrollment. Results suggest that the commercial CR product studied may be safely added directly (dry) into moderate-quality MC to improve calf serum IgG levels. Caution should be used before generalizing study findings to other commercial CR products.