Effects of waste milk on growth performance, immunity, and gut health of dairy calves

Abstract

Liquid feed are the major nutrient source that can have a significant impact on the growth and development of immune system of calves before weaning. The objective of this study was to investigate the effect of different liquid feed on growth, immunity and gut health of dairy calves. A total of 24 Holstein male calves (43.4 ± 0.93 kg of body weight, mean ± standard error) were assigned to 4 blocks based on arrival date according to a completely randomized block design. Animals were fed 4 L of whole milk twice a day after successful transfer of passive immunity until 7 d of age. From 8–56 d of age, calves received 100% milk replacer (MR, n = 8), 50% milk replacer mixed with 50% waste milk (MM, n = 8), or 100% waste milk (WM, n = 8). Starter and fresh water were offered ad libitum throughout the experiment. Blood samples were collected from jugular veins at 8, 49, and 70 d of age for measuring plasma concentrations of immunoglobulins (IgA, IgM, IgG), interleukins (IL-2, IL-6, IL-10) and tumor necrosis factor alpha (TNF-α). Fecal samples were collected at 49, and 70 d of age and subjected to 16 S rRNA gene amplicon sequencing. The results showed that feeding WM improved hip width (P = 0.007), hip height (P = 0.03), heart girth (P = 0.008), final body weight (P = 0.01), and feed efficiency (P = 0.04) of dairy calves compared to MR. Plasma concentrations of IgA (P < 0.001), IgM (P < 0.001), IgG (P < 0.001) and IL-10 (P < 0.001) were higher and TNF-α (P < 0.001) was lower in WM group. In addition, treatment and time interactively affected plasma concentrations of IgG (P = 0.05) and IL-2 (P < 0.001), which increased and decreased in WM group but decreased and increased in MR group, respectively, from 49 to 70 d of age. There was no difference in diarrhea case (P = 0.13) and average days of diarrhea (P = 0.08) among treatments. Difference in fecal microbiota was observed between MR and WM groups only at 49 d of age (P < 0.05). Analysis of differential abundance showed that the increase in the relative abundance of Prevotellaceae NK3B31 group (P = 0.03) and the decrease in that of Bacteroides (P = 0.04) was higher in WM than MM group from 49 to 70 d of age. In conclusion, WM had beneficial effects on growth performance and did not affect health statue, which might be explained by enhanced immune function modulated by fecal microbiota.