Effect of dry matter intake on visceral organ mass, cellularity, and the protein expression of ATP synthase, Na+/K+-ATPase, proliferating cell nuclear antigen and ubiquitin in feedlot steers

Abstract

Twenty-four steers [467 ± 7.2 kg initial body weight (BW)] predominately of Angus breeding were used to determine the effect of dry matter intake (1.25, 1.50, 1.75, and 2.00% of BW) on visceral mass, cellularity, and the protein expression of ATP synthase, Na+/K+-ATPase, proliferating cell nuclear antigen (PCNA) and ubiquitin. There were linear increases (P ≤ 0.05) in weights of total viscera, total digestive tract, liver, kidney, heart, lung, spleen, rumen, and abomasum with increasing dry matter intake (DMI). Protein concentration decreased linearly (P < 0.05) in small intestinal mucosa as DMI increased. PCNA expression increased linearly (P < 0.01) in liver as DMI increased. PCNA expression was affected quadratically (P < 0.05) in pancreas and small intestinal mucosa with an increase when DMI increased from 1.25 to 1.75% of BW, and a decrease when DMI increased from 1.75 to 2% of BW. ATP synthase, Na+/K+-ATPase, and ubiquitin expression in pancreas and ubiquitin expression in small intestinal mucosa increased linearly (P < 0.05) as DMI increased. These results indicate that increasing DMI increases the mass of visceral organs and carcass and influences expression of proteins influencing energy utilization and efficiency in pancreas, small intestine, liver, and sternomandibularis muscle.Key words: Dry matter intake, visceral organ mass, cellular energy metabolism, steer