Comprehensive Evaluation of Forage Provision on the Serum Biochemical Indicators, Behavior and Health of Dairy Calves

Forage may boost dairy calf health, yet findings vary. We conducted a meta-analysis to assess forage's impact on serum biomarkers, fecal scores, diarrhea, and feeding habits, reviewing 29 studies from 2000 to 2023 across Google Scholar, ScienceDirect, and X-Mol. The results showed that forage supplementation increased the concentration of β-hydroxybutyrate (BHBA) in the postweaning calves. Furthermore, Dairy calves with forage access showed higher ruminal pH, more rumination, longer eating times, and less non-nutritive oral behavior than those without forage, in both preweaning and postweaning periods. Subgroup analysis reported that feeding forage as a free-choice (FC) had a greater effect on BHBA concentration than feeding it as a total mixed ration (TMR; defined as a mixture of calf starter and forage), and straw supplementation had a greater effect than alfalfa hay (AH) or oat hay (OH) during the postweaning period. Our findings indicate an optimal 9% forage supplementation on a dry matter basis for preweaning calf health.