Effect of forage:concentrate ratio in the diet on concentrations of IGF-1, insulin, glucagon and volatile fatty acids appearing across the splanchnic tissues of steers

Abstract

Steen (1992) demonstrated that grass silage diets sustained lower carcass lean gain per MJ digestible energy (DE) intake than diets of low forage: concentrate ratios (F:CR), at equal levels of DE intake. Jugular concentrations of IGF-1, insulin and glucagon were significantly elevated in animals offered the latter diets while rumen VFA were unaffected (Thorp et al1994). Both IGF-1 and insulin stimulate protein synthesis (Abdul-Razzaq and Bickerstaffe 1989, Douglas et al1991) and it is generally accepted that insulin and glucagon influence carbohydrate metabolism in the ruminant. Plasma propionate and butyrate stimulate insulin and glucagon secretion (Harmon 1991). This experiment was part of a series designed to investigate the control of lean and fat deposition in beef cattle and aimed to determine concentrations of IGF-1, insulin, glucagon and VFA appearing across the splanchnic tissues.