Inclusion of hybrid rye in diets for weanling pigs does not compromise daily gain, but may reduce diarrhea incidence despite pigs having preference for consuming corn over hybrid rye

Two experiments were conducted to test the hypotheses that feed preference and growth performance will not differ if hybrid rye replaces some of the corn in diets for nursery pigs. In experiment 1, 40 barrows (9.2 ± 1.0 kg) were housed in 20 pens for eight days. Each pen had two identical feeders containing a corn-based diet or a diet in which 500 g/kg of the corn was substituted with hybrid rye, and feeder positions were switched daily. In experiment 2, 160 pigs (6.0 ± 0.7 kg) were randomly allotted to 40 pens and five treatments. Phase 1 diets were fed from day 1–7 (0, 30, 60, 90, or 120 g/kg rye), whereas phase 2 (0, 50, 110, 160, or 210 g/kg rye) and phase 3 (0, 150, 300, 450, or 600 g/kg rye) diets were fed from day 7–21 and day 21–34, respectively. Body weights were recorded at the start and end of each phase, fecal scores were recorded every other day, and blood samples were obtained from one pig per pen on day 21 and 34. Results of experiment 1 indicated that preference was greater (P < 0.05) for the corn-based diet than for the corn-hybrid rye mixed diet on days 2, 3, 6, and 8, and for the overall period. Overall, pigs preferred the corn-based diet over the rye-based diet by a ratio of 5.7–4.3. In experiment 2, there were no differences among treatments for final body weight or average daily gain. During phase 3 and overall experiment, pigs fed diets with 600 g/kg hybrid rye and no corn consumed the most feed (quadratic, P < 0.05). Consequently, gain:feed in phase 3 and overall was reduced (quadratic, P < 0.05) as hybrid rye replaced corn in the diet. Diarrhea incidence decreased (quadratic, P < 0.05) with 60 or 90 g/kg hybrid rye in the phase 1 diet. Blood urea N was elevated (day 21, quadratic, P < 0.05; day 34, linear, P < 0.05) as dietary hybrid rye inclusion increased. In conclusion, castrated male weaned pigs had a preference for corn-based diets over diets containing a mix of corn and hybrid rye, but replacing up to 300, 400, or 1000 g per kg of corn in phase 1, 2, and 3 diets for weanling pigs did not result in differences in average daily gain or final body weight of pigs, but gain to feed ratio was reduced for pigs fed the diets with the greatest inclusion of hybrid rye because feed intake was increased. Hybrid rye may also modulate the immune response by influencing blood cell concentrations and reducing diarrhea incidence in pigs.