Abstract:

This study was designed to investigate the effect of dietary pork and beef proteins on growth performance and
physiological responses of growing rats after a long-term intervention. Thirty young male Sprague-Dawley rats were
categorized into three groups and fed a diet containing proteins isolated from pork, beef or casein, respectively. After
90-day intervention, physiological parameters were measured. The results indicated that rats fed pork and beef proteins
showed a decrease in growth rate and fat deposition than those fed casein (P < 0.05), but they had higher activities of alanine
aminotransferase and aspartate transaminase in serum and lower triglyceride level (P < 0.05). Pork and beef protein could
decrease serum concentration of triglyceride (P < 0.05). Rats fed beef protein showed lower serum total cholesterol and glucose
contents than the casein-fed group (P < 0.05), but the pork protein-fed group did not show such an effect (P > 0.05). Rats fed pork
and beef protein had lower concentrations of free amino acids in serum (P < 0.05). Therefore, long-term intervention with
beef and pork proteins had different effects on body metabolism, depending on protein source and variation in digestion and
absorption. Pork and beef protein intakes can control body weight, and beef protein may cause lower hepatic metabolism and
reduce serum lipid levels.

Key words: pork protein, beef protein, blood biochemistry, lipid metabolism