Animal proteins such as milk products, blood products, fish meal, chicken meal, and poultry by-product meal are usually used as amino acid sources in diets for weanling pigs because the nutrients in these ingredients are highly digestible and because they do not contain the anti-nutritional factors that are present  in conventional soybean meal. Due to the cost of animal protein sources, other alternatives have been investigated. One alternative is soybean meal which has been fermented to destroy antinutritional factors and increase protein digestibility. Fermented soybean meal (FSBM) may partly replace milk and blood proteins in diets fed to weanling pigs from seven to 21 days post-weaning. However, there are no data on the inclusion of more than 10% FSBM in diets fed to weanling pigs. Therefore, two experiments were conducted to test the hypothesis that FSBM may be included in diets fed to weanling pigs to replace all animal protein sources.

Experiment 1 was designed to test the hypothesis that FSBM can replace fish meal in diets fed to weanling pigs during the initial 26 days post-weaning without negatively affecting growth performance. A total of 192 weanling pigs were allotted to four dietary treatments with two phases (14 and 12 d, respectively).In Phase 1, the positive control diet contained 8% fish meal, 15% whey powder, and 3.5% protein plasma; in the negative control diet, these ingredients were replaced with corn and conventional soybean meal. In the two experimental diets, fermented soybean meal replaced fish meal (FSBM-Low), or fish meal and protein plasma (FSBM-High). Phase 2 diets were similar except that the positive control diet contained 8% fish meal and 5% whey powder, and fermented soybean meal replaced whey powder in the FSBM-High diet.

Table 1. Inclusion rates of selected ingredients in Phase 1 and Phase 2 diets, Experiment 1

In Phase 1, ending body weight was less (P < 0.01) in pigs fed the the FSBM-High diet than in pigs fed the FSBM-Low or positive control diets, and did not differ from body weight in pigs fed the negative control diet (Table 2). Average daily gain was greater (P < 0.05) in pigs fed FSBM-Low than in pigs fed the FSBM-High or negative control diets, and did not differ from average daily gain in pigs fed the positive control diet. Average daily feed intake and gain:feed ratio did not differ among pigs fed any of the diets.

In Phase 2, the gain:feed ratio was less (P < 0.01) for pigs fed the FSBM-Low than for pigs fed the positive control or FSBM-High diets, and did not differ from the gain:feed ration for pigs fed the negative control diet. There were no differences in any of the other growth performance measures between pigs fed any of the diets.

Over the course of the entire experiment, there was no difference in final body weight, average daily gain, average daily feed intake, or gain:feed ratio among pigs fed the four diets.

Table 2. Growth performance of nursery pigs fed experimental diets, Experiment 1

^a-bMeans within a row lacking a common superscript letter are different (P< 0.05).

A total of 175 pigs were allotted to five dietary treatments in three phases (seven, seven, and 14 days, respectively). The positive control diet contained fish meal and whey powder in all phases in addition to protein plasma in Phases 1 and 2, but these ingredients were not included in the negative control diet. Three experimental diets were also formulated. Fermented soybean meal replaced fish meal in all experimental diets. FSBM also replaced whey powder in the FSBM-Low diet, protein plasma in the FSBM-Medium diet, and both protein plasma and whey powder in the FSBM-High diet.

Table 3. Inclusion rates of selected ingredients in Phase 1, Phase 2, and Phase 3 diets, Experiment 2

In Phase 1, ending body weight and average daily gain were greatest (P < 0.01) in pigs fed the positive control and FSBM-Low diets, less in pigs fed the FSBM-Medium diet, and least in pigs fed the FSBM-High and negative control diets (Table 4). Pigs fed the FSBM-High and negative control diets lost weight in Phase 1.

In Phases 2 and 3, no differences were observed in average daily gain, average daily feed intake, or gain:feed ratio among pigs fed the different diets. Pigs fed the positive control, FSBM-Low, and FSBM-Medium diets had the greatest average daily gain over the course of the entire experiment. However, the average daily gain for pigs fed the FSBM-Low and FSBM-Medium diets did not differ significantly from that of pigs fed the FSBM-High or negative control diets. No differences were observed over the full 28 days in average daily feed intake and gain:feed ratio.

The fact that average daily gain did not differ among treatments in the second week post-weaning indicates that FSBM may replace whey powder in diets after one week post-weaning. Weanling pigs digest the lactose in whey powder easily, but lactase activity in the small intestine starts decreasing at three days after weaning and continues to decrease as pigs get older. Protein plasma contains immunoglobulins that may enhance the immune system of newly weaned pigs while their own immune systems are still developing. The absence of these immunoglobins and resulting vulnerability to diarrhea may have contributed to slower growth in the pigs fed  the FSBM-High diet in the first week post-weaning.

Table 4. Growth performance of nursery pigs fed experimental diets, Experiment 2

^a-cMeans within a row lacking a common superscript letter are different (P< 0.05).

• Fermented soybean meal may replace fish meal in diets fed to pigs during the initial 28 days post-weaning without affecting average daily gain or body weight.
• Fermented soybean meal cannot replace protein plasma and whey powder during the first week post-weaning without negatively affecting growth performance.
• During the second and third week after weaning, it is possible to use FSBM rather than protein plasma and whey powder. This is most likely because the lactose in whey powder and the immunoglobulins in protein plasma are most beneficial to the pig in the first week post-weaning.

This research report is based on unpublished research by O. J. Rojas and H. H. Stein.