Homocysteineinemia, growth performance and immune responses in suckling and weanling piglets
Homocysteine, an intermediary sulfur AA, is recognized as a powerful pro-oxidant with deleterious effects on physiological and immune functions. In piglets, there is an acute 10-fold increase of plasma concentrations of homocysteine (PHcy) during the first 2 wk of life. This project aimed to create wide ranges of PHcy by varying folates and vitamin B12 (B12) supplies to sows and piglets. Growth, immune response and PHcy were studied until 56 d of age. Third-parity sows were randomly assigned to a 2 x 2 split-plot design with 2 dietary treatments (S) during gestation and lactation, S- (1 mg/kg of folates and 20 µg/kg of B12, n = 15) or S+ (S- x 10, n = 16), and 2 treatments to piglets (P) within each half-litter, i.m. injections (150 µg) of B12 (P+) at d 1 and 21 (weaning) or sham-injections of saline (P-). Within each litter of 12 piglets, 3 P+ and 3 P- were studied for growth and the others for immunological responses. During lactation, the decrease of PHcy after i.m. B12 was more pronounced in S- than S+ piglets (S × P, P < 0.02), values were 32 % lower in S+P+ (16.7 ± 0.7 µM) than S-P- piglets (24.7 ± 0.7 µM) at 21 d of age. At 56 d of age, PHcy were lower (P < 0.01) for P+ (15.7 ± 0.5 µM) than P- piglets (18.7 ± 0.5 µM). No treatment effect was observed on growth except for a lower post-weaning G:F in S+P- piglets than in others (S × P, P = 0.03). Positive correlations were observed between PHcy and growth (r > 0.29, P < 0.02). Antibody responses to ovalbumin were not affected by treatments. Proliferation of lymphocytes in response to the mitogen concanavalin A tended to be lower in culture media with sera from S- piglets than S+ (P < 0.08) and P- piglets than P+ (P < 0.10), and this response was more marked (P = 0.04) with high PHcy (> 21 µM) as compared to medium (17-21 µM) or low (< 17 µM). In conclusion, vitamin supplementations to sows and piglets induced large variations of PHcy in piglets. Although apparently not harmful for growth performance, the detrimental effects of S-and P- treatments or high PHcy on some indicators of cell mediated immunity suggest that these young animals are immunologically more fragile.
Keywords: homocysteine, growth and immunity, piglets