Effects of lamb early starter feeding on the expression of genes involved in volatile fatty acid transport and pH regulation in rumen tissue

• Ruminal pH may not be heavily dependent on diet but may be age-related.
• Ruminal TVFA concentration increases with age and with early starter feeding.
• The potential increase in bicarbonate-dependent transport mediated via DRA for ruminants fed highly fermentable diets would also help regulate ruminal pH.
• MCT1 expression is important for maintaining pH homeostasis.
• Early starter feeding affects gene expression levels in the ruminal epithelium.

The objective of this study was to investigate the effects of early starter feeding on ruminal pH regulation and the expression levels of genes involved in rumen volatile fatty acid (VFA) metabolism in lambs. A total of 78 male Hu lambs with similar born body weights were selected. Six lambs were slaughtered immediately after birth, and the remaining 72 were equally divided into a group fed by starter diet 1 at day 7 or a group fed by starter diet 1 at day 42. The lambs from both groups were weaned at day 56 and transacted to starter diet 2 at day 59. Six lambs from each group were randomly slaughtered at days 14, 28, 42, 56, 70 and 84, respectively. The results revealed that the ruminal VFA concentration in the early provision group was higher (P < 0.05) than that in late provision group, while the rumen pH was not affected (P > 0.05) by early or late starter feeding. Treatment-age interactions (P < 0.05) and age alone (P < 0.05) affected the expressions of NHE2, NHE3, DRA, HMGCL and MCT1. The expression of NHE2, DRA and HMGCL in early provision group were lower (P < 0.05) than that in late provision group. However, the expression of MCT1 in early provision group was higher (P < 0.05) than that in the late provision group. The findings of this study show that early starter feeding in lambs can increase the ruminal VFA concentration and affect the expression levels of genes involved in VFA transport and pH regulation in the ruminal epithelium.