|Frank, J - UNIVERSITY OF MISSOURI|
|Mellencamp, M - PIC USA, INC.|
|Boyd, R - PIC USA, INC|
|Allee, G - UNIVERSITY OF MISSOURI|
Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 11, 2005
Publication Date: July 15, 2005
Citation: Frank, J.W., Mellencamp, M.A., Carroll, J.A., Boyd, R.D., Allee, G.L. 2005. Acute feed intake and acute-phase protein responses following a lipopolysaccharide challenge in pigs from two dam lines. Veterinary Immunology and Immunopathology. 107:179-187. Interpretive Summary: Currently, it is believed that pigs which exhibit high rates of muscle growth are more susceptible to immune challenges than pigs which have lower rates of muscle growth. Therefore, this study was conducted to determine if two different genetic lines of pigs would respond differently to an immune challenge. To determine the overall impact of the immune challenge on the well-being and productivity of the pigs, we measured various blood proteins and feed intake for 48 hours after an immune challenge. While we found that feed intake was a good indicator that the pigs were stressed because of the immune challenge, we did not find any difference between the two groups of pigs. Additionally, we found that feed intake was primarily associated with only one of the blood proteins examined, which may be utilized in the future as an indicator of an animal's overall well-being. Finally, we found that male castrated pigs where more susceptible to the immune challenge than female pigs, as more of the male pigs died due to the immune challenge compared to the female pigs. This information will be helpful with regard to developing optimal management practices to ensure the overall well-being and productivity of swine in the future. Additionally, this information will be of interest to scientists working in the areas of swine immunology and swine genetics, and to commercial swine producers.
Technical Abstract: This study was conducted to evaluate the response of two genetic lines of pigs to acute increases of endotoxin (LPS). Acute-phase proteins were also measured to determine their potential use as biological indicators of the immune response. Thirty-six pigs (initial body weight = 21.3 + or - 0.48 kg) were allotted by genotype (Line 1 and Line 2) and sex (castrates and gilts) to one of three LPS dose treatments and penned individually. Treatments were a single i.m. injection of 0 (LPS-0), 25 (LPS-25), or 50 ug LPS/kg body weight (LPS-50). Acute changes in feed intake were related to a pre-injection baseline intake. Feeders were weighed daily to establish baseline feed intake (average daily feed intake -48 to 0 h prior to injection). The acute feed intake response (AFIR) was computed as the average daily feed intake 0 to 48 h after injection divided by baseline intake. Serum was harvested at time 0 and 48 h after injection. LPS-0 pigs grew faster and consumed more feed than the LPS-25 or LPS-50 pigs (0.79 vs. 0.51 and 0.50; 1.15 vs. 0.96 and 0.89 kg/d, respectively; P < 0.001). The AFIR of Line 1 castrates and Line 2 gilts was similar for LPS-25 and LPS-50 treatments, while Line 1 gilts and Line 2 castrates had decreased AFIR with increased LPS dose (sex x genotype x LPS, P < 0.05). Three of eighteen castrates died but no gilts died following the LPS challenge (P < 0.10). Castrates had higher haptoglobin (HPT) concentrations than gilts on d 0 (18.1 vs. 13.1 units of absorption/mg of protein; P < 0.03). Line 1 pigs had higher C-reactive protein (CRP) concentrations than Line 2 pigs (P < 0.05) on d 0. LPS treatment did not change serum concentrations of CRP, HPT, or ceruloplasmin. However, the change in serum amyloid A (SAA) concentration decreased quadratically (from 0 to 48 hr) with increasing LPS dose (P < 0.02). This change in SAA was negatively correlated with the AFIR (r = -0.80; P < 0.001). In general, castrates appear to be more sensitive to endotoxin challenges than gilts. Serum amyloid A, but not the other acute-phase proteins evaluated, was a good biological indicator of immune system activation following an acute lipopolysaccharide challenge when compared to the acute change in feed intake (AFIR).