Digestibility experiments have been conducted to determine the nutritional value of an enhanced torula yeast derived from forestry by-products. Results of these experiments indicated that enhanced torula yeast has a greater digestibility of amino acids and P than fish meal, and a concentration of metabolizable energy that is not different from that in fish meal. Therefore, it is believed that the enhanced torula yeast can be included in diets for weanling pigs at the expense of fish meal and other animal protein sources. Therefore, the objective of this experiment was to determine the effects on growth performance, fecal score, and blood characteristics of including the enhanced torula yeast at the expense of fish meal and plasma protein in diets fed to weanling pigs.

Experimental Procedures

The enhanced torula yeast was produced by Arbiom Inc. (Durham, NC). Commercial sources of fish meal and spray dried plasma protein were also used. A total of 128 weanling pigs (20 ± 2 days of age; initial BW: 6.71 ± 0.76 kg) were allotted to 4 dietary treatments with 4 pigs per pen and 8 replicate pens per diet. The 4 diets were based on corn and soybean meal and the control diet also contained fish meal and plasma protein. Three additional diets contained fish meal and enhanced torula yeast, plasma protein and enhanced torula yeast, and a diet with only enhanced torula yeast, but no fish meal or plasma. The inclusion of the enhanced torula yeast in diets was calculated to replace the amount of standardized ileal digestible Lys provided by fish meal, plasma, or both in the control diet. Pigs were fed the experimental diets during phase 1 (d 1 to 14 post-weaning), whereas a common diet was fed during phase 2 (d 14 to 27 post-weaning). Therefore, a total of 5 diets were formulated and provided ad libitum (Table 1). Growth performance parameters were calculated in the 2 phases and for the overall experimental period. However, fecal scores were determined only in phase 1, and at the end of phase 1, a blood sample was collected from one pig per pen. Blood samples were analyzed for tumor necrosis factor-α (TNF-α), immuno globulin G (IgG), peptide YY (PYY), blood urea nitrogen (BUN), total protein, and albumin.

Results

There were no differences in final BW, ADG, ADFI, and G:F among dietary treatments in phase 1, phase 2, or for the overall experimental period (Table 2). Likewise, there were no differences among the 4 dietary treatments for fecal score or frequency of fecal score ≥ 3 (Table 3). There were also no effect of diet on plasma concentration of TNF-α, IgG, PYY, BUN, total protein, or albumin when the enhanced torula yeast replaced plasma protein, fish meal, or both (Table 4).

Key points

• There was no negative effects of replacing fish meal or plasma protein with enhanced torula yeast on growth performance or fecal score.
• Feed intake, inflammatory immune response, energy metabolism, and protein utilization are not affected if plasma protein or fish meal are replaced by enhanced torula yeast.

Table 1. Composition of experimental diets

Table 2. Growth performance of pigs fed the experimental diets

Table 3. Fecal score and frequency of diarrhea of pigs fed the phase 1 experimental diets (d 1 to 14)¹

²Frequency = number of pen days with fecal score ≥ 3.

Table 4. Blood parameters of pigs fed the phase 1 experimental diets¹