Effects of bedding type and forage provision on growth performance, health, and rumen fermentation in dairy calves

The objective of this study was to determine the effects of different diets (concentrate [CON] or concentrate with oat hay [FOR]) and bedding materials (straw [STR] or rice husks [RIC]) on growth performance, rumen fermentation, and blood metabolites in dairy calves. Holstein dairy calves (initial BW 41.2 ± 4.03 kg; n = 15 calves per treatment) were randomly assigned to 4 dietary treatments in a 2 × 2 factorial design: (1) CON-STR, (2) CON-RIC, (3) FOR-STR, and (4) FOR-RIC. Calves were offered similar volumes of pasteurized whole milk twice daily until complete weaning at the end of wk 8. All calves received a commercial pelleted starter concentrate, whereas those fed forage received oat hay for 12 wk. The bedding materials were renewed weekly. From wk 13 to 28, all calves were housed together and fed identical diets. Feed intake and refusals were recorded daily for wk 1 to 12. Body weight and structural measurements were taken on the day of birth and subsequently, every 2 wk until wk 12; BW was also recorded on the last day of wk 28. Rumen samples were taken at the end of wk 1, 5, 12, and 28 of age via esophageal tube, and blood samples were taken at the end of wk 12 for determination of metabolic and immunity related indicators. Three-way interactions (diet × bedding × time) were observed for milk and solid feed nutrient intakes, rumen pH, acetate and total VFA (TVFA). The FOR group had greater milk intake, total solid feed DMI, total DMI, and ADG than the CON group from wk 1 to 12, leading to higher BW at the end of wk 28. Calves on RIC bedding consumed more forage compared with those on STR during wk 1 to 12. Although the FOR group had greater dietary NDF, physically adjusted NDF, and ADF intakes compared with CON from wk 1 to 8, the FOR-RIC calves showed the highest intakes and CON-RIC had the lowest (wk 9 to 12 and wk 1 to 12). A significant bedding × day interaction was observed for ADG, withers height, and heart girth. Compared with RIC-bedded calves, STR-bedded calves had lower ADG for wk 1 to 8 but higher ADG for wk 9 to 12. Straw bedding was associated with lower blood urea and IL-6 and higher total antioxidant capacity compared with RIC. Rumen pH was higher in STR-bedded calves than in RIC-bedded calves, with no effect of diet. Calves on CON-STR had the lowest concentration of acetate and TVFA at the end of wk 12. In conclusion, this study showed rice husk bedding had significant effect on dietary intake, calf health and immunity, and performance of the calf during wk 1 to 28. In contrast, forage feeding can mitigate the negative effects, especially during wk 9 to 12.