Effect of feed restriction on performance and postprandial nutrient metabolism in pigs co-infected with Mycoplasma hyopneumoniae and swine influenza virus

Abstract

As nutritional status and inflammation are strongly connected, feeding and nutritional strategies could be effective to improve the ability of pigs to cope with disease. The aims of this study were to investigate the impact of a feed restriction on the ability of pigs to resist and be tolerant to a coinfection with Mycoplasma hyopneumoniae (Mhp) and the European H1N1 swine influenza virus, and the consequences for nutrient metabolism, with a focus on amino acids. Two groups of specific pathogen-free pigs were inoculated with Mhp and H1N1 21 days apart. One group was fed ad libitum, the other group was subjected to a two-week 40% feed restriction starting one week before H1N1 infection. The two respective mock control groups were included. Three days post-H1N1 infection, 200 g of feed was given to pigs previously fasted overnight and serial blood samples were taken over 4 hours to measure plasma nutrient concentrations. Throughout the study, clinical signs were observed and pathogens were detected in nasal swabs and lung tissues. Feed-restricted pigs presented shorter hyperthermia and a positive mean weight gain over the 3 days post-H1N1 infection whereas animals fed ad libitum lost weight. Both infection and feed restriction reduced postprandial glucose concentrations, indicating changes in glucose metabolism. Post-prandial plasma concentrations of the essential amino acids histidine, arginine and threonine were lower in co-infected pigs suggesting a greater use of those amino acids for metabolic purposes associated with the immune response. Altogether, these results indicate that modifying feeding practices could help to prepare animals to overcome an influenza infection. Connections with metabolism changes are discussed.

Figure 1. Mean rectal temperatures (°C) of pigs.

Mean rectal temperatures in co-infected (MH1N1) and control (C) pigs fed ad libitum (AL) or feed restricted (FR) : C-AL (black dashed line), C-FR (gray dashed line), MH1N1-AL (black solid line) and MH1N1-FR groups (gray solid line), from the day of Mhp inoculation (day 0) until the end of the experiment. Arrows indicate the day of the beginning of the feed restriction (day 15) and the day of H1N1 inoculation (day 21).

Figure 2. Mean daily weight gain (kg) of pigs after Mhp and H1N1 inoculations.

Mean daily weight gains between Day (D) 14 and D21 (the week before H1N1 infection), between D21 and D24 (between 0 and 3 DPI H1N1), between D21 and D28 (between 0 and 7 DPI H1N1) and between D14 and D28, for control (C) or co-infected (MH1N1) groups fed ad libitum (AL) or feed restricted (FR): C-AL (hatched black), C-FR (hatched gray), MH1N1-AL (black) and MH1N1-FR (gray) groups. Mean daily weight gains with different letters are significantly different with P<0.05.

Figure 3. Postprandial kinetics of plasma glucose (3a) and urea (3b) concentrations (mg/L) measured in pigs.

Average plasma concentrations were measured after an overnight fasting and then during the 4ïc fluid administration in co-infected (MH1N1) and control (C) pigs fed ad libitum (AL) or feed restricted (FR): C-AL (black dashed line), C-FR (gray dashed line), MH1N1-AL (black solid line) and MH1N1-FR groups (gray solid line). Values are means +/− SD. P values for glucose: P_I<0.05 at fasted basal state, 15 and 30 min after the meal, then from 105 to 210 min; P_FR<0.05 from 15 to 60 min after the meal. P values for urea: P_I<0.01 from 60 to 240 min.

Figure 4. Postprandial kinetics of plasma threonine (3a) and arginine (3b) concentrations (µM) measured in pigs.

Average plasma concentrations were measured after an overnight fasting and then during the 4ïc fluid administration in co-infected (MH1N1) and control (C) pigs fed ad libitum (AL) or feed restricted (FR): C-AL (black dashed line), C-FR (gray dashed line), MH1N1-AL (black solid line) and MH1N1-FR groups (gray solid line). Values are means +/− SD. P values for threonine: P_I<0.05 from basal to 240 min; P_FR<0.05 from 180 to 240 min; P_I×FR<0.05 from 180 to 240 min. P values for arginine: P_I<0.01 from basal to 240 min; P_FR<0.05 from 150 to 240 min; P_I×FR<0.05 from 180 to 240 min.