Effects of a wide range of dietary forage-to-concentrate ratios on nutrient utilization and hepatic transcriptional profiles in limit-fed Holstein heifers

Background Improving the efficiency of animal production is a relentless pursuit of ruminant producers. Energy utilization and partition can be affected by dietary composition and nutrient availability. Furthermore, the liver is the central metabolic intersection in cattle. However, the specific metabolic changes in the liver under conditions of limit-feeding remain unclear and require further study. The present study aimed to elucidate the effects of a wide range of dietary forage:concentrate ratios (F:C) on energy utilization, and identify potential changes in molecular metabolism by analyzing hepatic transcriptional profiles. Twenty-four half-sib Holstein heifers were fed four F:C diets (20:80, 40:60, 60:40, and 80:20 on a dry matter basis), with similar intake levels of metabolizable energy (ME) and crude protein. Liver biopsy samples were obtained and RNA sequencing was conducted to identify the hepatic transcriptomic changes. Moreover, the ruminal fermentation profiles, growth characteristics, and levels of metabolites in the liver and plasma of the heifers were monitored.