Production of hybrid rye in North America is increasing after being introduced to Canada and the United States in 2014 and 2016, respectively. Compared with corn, hybrid rye contains similar amounts of standardized ileal digestible amino acids, a greater concentration of standardized total tract digestible P, and approximately 94% of the metabolizable energy. Hybrid rye contains more fermentable dietary fiber than corn, which has the potential to improve gut health, but its reduced digestibility of amino acids may simultaneously have a negative impact on the health of the large intestine. Two experiments were conducted to determine the maximum amount of hybrid rye that can be included in diets for weanling pigs without influencing growth performance or diarrhea incidence.

Experimental Procedures

Exp. 1

A total of 160 weanling pigs were randomly allotted at approximately 21 days of age to 5 treatment groups. Four pigs were housed per pen, and there were 8 replicate pens per treatment. Pigs were fed for 34 days in a 3-phase feeding program. Phase 1 diets were fed for 7 days post-weaning, phase 2 diets were fed from day 7 to 21, and phase 3 diets were fed from day 21 to 34. In each phase, a basal diet primarily based on corn and soybean meal was formulated and 4 diets included increasing concentrations of hybrid rye at the expense of corn (Table 1). In phase 1, the replacement rate of corn with hybrid rye was 0, 7.5, 15.0, 22.5, and 30%, respectively. In phase 2, the replacement rate of corn with hybrid rye was 0, 10, 20, 30, and 40%, respectively, and in phase 3, the replacement rate of corn with hybrid rye was 0, 25, 50, 75, and 100%. Growth performance data were summarized for each phase and for the overall duration of the experiment, and fecal scores were assessed visually every other day throughout the experiment.

Exp. 2

A total of 128 weanling pigs were randomly allotted at approximately 21 days of age to 4 treatments, with 8 pens of 4 pigs per treatment. The feeding regimen was identical to Exp. 1, with the exception that phase 3 concluded on day 35, rather than day 34 (Table 2). The replacement rates of corn with hybrid rye in Exp. 2 diets were: phase 1 = 0, 20, 40, and 60%; phase 2 = 0, 30, 60, and 90%; and phase 3 = 0, 33, 66, and 100%. Growth performance data were summarized for each phase and for the overall duration of the experiment, and fecal scores were assessed visually every other day throughout the experiment.

Results

Exp. 1

There were no differences in body weight nor ADG at any point during the experiment (Table 3). During phase 3, there was a quadratic response (P < 0.05) for ADFI, where the pigs fed diets with 100% hybrid rye replacement for corn consumed the most feed. Similarly, there was a quadratic response (P < 0.05) for ADFI overall. Consequently, G:F in phase 3 and overall also showed a quadratic response(P < 0.05). There were no differences for average fecal scores during the experiment (Table 4). However, but diarrhea incidence decreased with 6 and 9% hybrid rye inclusion in phase 1, but not with 12% hybrid rye inclusion (quadratic, P < 0.05).

Exp. 2

Average daily gain in phase 1 linearly increased (P < 0.05) as the inclusion of hybrid rye increased, but there were no other differences in body weights or ADG during the experiment (Table 5). Average daily feed intake linearly increased (P < 0.05) during phase 1, phase 3, and overall as hybrid rye was added to the diets. Thus, G:F was negatively impacted by inclusion of hybrid rye in the diet (quadratic, P < 0.05). No differences in average fecal scores nor diarrhea incidence were observed (Table 6).

Key Points

• Nursery pigs appear to tolerate up to 24, 48, and 60% hybrid rye in phase 1, 2, and 3 diets, respectively, without exhibiting any reduction in growth.
• As hybrid rye is added to diets, pigs consume more feed, likely as a result of hybrid rye’s reduced metabolizable energy compared with corn. Thus, G:F is expected to be reduced in proportion to the increase in feed intake when nursery pigs are fed hybrid rye.
• In Exp. 1, inclusion of hybrid rye at up to 9% in phase 1 nursery diets appeared to have a positive effect on reducing diarrhea, but there were no observable differences in fecal scores or diarrhea incidence in the second experiment.

Table 1. Cereal grain inclusion rates in experimental diets for nursery pigs in Exp. 1

Table 2. Cereal grain inclusion rates in experimental diets for nursery pigs in Exp. 2

Table 3. Growth performance of nursery pigs fed increasing rates of hybrid rye in Exp. 1

Table 4. Fecal score and incidence of diarrhea of pigs fed increasing levels of hybrid rye in Exp. 1

¹Fecal scores: 1 = normal feces; 2 = moist feces; 3 = mild diarrhea; 4 = severe diarrhea;                     and 5 = watery diarrhea.

²Incidence of diarrhea calculated as number of days with fecal score ≥ 3 divided by                             total number of observations.

Table 5. Growth performance of nursery pigs fed increasing rates of hybrid rye in Exp. 2

Table 6. Fecal score and incidence of diarrhea of pigs fed increasing levels of hybrid rye in Exp. 1

¹Fecal scores: 1 = normal feces; 2 = moist feces; 3 = mild diarrhea; 4 = severe diarrhea;                       and 5 = watery diarrhea.

²Incidence of diarrhea calculated as number of days with fecal score ≥ 3 divided by                               total number of observations.