Effects of Diet Forage-to-Concentrate Ratio and Intake on Energy Metabolism in Growing Beef Heifers: Net Nutrient Metabolism by Visceral Tissues

Summary

This controlled trial examined how diet composition (forage vs. concentrate) and metabolizable energy intake influence nutrient metabolism in growing beef heifers, specifically measuring net flux of glucose, nitrogen compounds and ketone bodies across visceral tissues. Higher energy intake increased glucose and urea nitrogen removal by portal-drained viscera and increased release of ammonia nitrogen and amino acids. Heifers fed high-concentrate diets (75% concentrate) showed lower net glucose removal from the portal-drained viscera, reduced ammonia nitrogen metabolism, and lower ketone body production compared to those fed high-forage diets (75% alfalfa), despite equivalent metabolizable energy intake—differences that correlated with improved tissue energy retention on the concentrate diet.

Regional applicability

Although conducted in the United States, this mechanistic study of visceral nutrient metabolism in beef cattle is directly relevant to understanding energy metabolism in intensive beef production systems in the United Kingdom. The findings on forage-to-concentrate ratio effects on metabolic efficiency could inform feeding strategies and energy assessment models used in British beef production and research.

Key measures

Net nutrient metabolism (glucose, urea nitrogen, ammonia nitrogen, amino acids, lactate, beta-hydroxybutyrate) by portal-drained viscera, liver, and kidneys; metabolizable energy intake; tissue energy retention

Outcomes reported

The study measured net nutrient metabolism by portal-drained viscera, liver and kidneys in growing beef heifers fed diets with different forage-to-concentrate ratios at two metabolizable energy intakes. Key metabolic outcomes included glucose removal, ammonia and amino nitrogen metabolism, and ketone body release across visceral tissues.

Topic tags