Effects of Salmonella typhimurium Challenge on Swine Growth, Nitrogen Balance, Insulin-like Growth Factor-I, and Acute Phase Proteins

Growing barrows were used to determine the effects of an en teric disease challenge on nutrient balance, growth, acute phase proteins, and IGF-I. Pigs were challenged on d 0 with Salmonella typhimurium (S; N=21), or unchallenged and fed ad libitum (A; n=6), or unchallenged and pair-fed the same amount of feed as a challenged pig (P; n=8). Blood was collected on d -3, 1, 5, 9, and 15. A disease challenge × time interaction was observed for serum haptoglobin (P < 0.05), with greater haptoglobin for S vs A on d 1 and 5 (P < 0.05) and for S vs P on d 5 (P < 0.05). Plasma IGF-I increased from d -3 to 17 (linear, P < 0.05) and was increased for S vs A on d 9 (P < 0.06) and d 15 (P < 0.03), and for S vs P (P < 0.02) on d 9. A disease challenge × time interaction was observed (P < 0.05) for average daily gain as it decreased for S (.62 kg) vs A (1.38 kg; P < 0.01) and P (.95 kg; P < 0.07) from d 0 to 3. A disease challenge×ctime interaction was observed for retained nitrogen (N; P <0.05), indicating reduced lean growth from d 0 to 3 for S (19.6 g/d; P < 0.01) and P (23.2 g/d; P <0.07) vs A (30.1 g/d). Although short-term differences were evident, d 0 to 17 growth performance and N balance were not affected by an acute S. typhimurium challenge (P > 0.20). Results indicate that 66% of the short-term reductions in average daily gain from an acute S. typhimurium disease challenge are due to reductions in feed intake. The remaining differences are due to the acute phase immune response.