Saccharomyces cerevisiae boulardii improves performance of pigs fed low and high energy diets in summer

Reduced feed intake over summer, and the consequential slow growth of finisher pigs is an important issue for the Australian pork industry. Diets with higher starch and lower fibre (e.g. high wheat and low barley or millrun, to increase energy density) have been shown to reduce the digestive heat increment experienced by pigs (Noblet et al. 1985). However, raw material costs can make this much more expensive than feeding diets containing high levels of barley or millrun. Levucell SB (LSB) (Saccharomyces cerevisiae boulardii, CNCM I-1079) is a live yeast used to maintain healthy and balanced gut micro-flora in pigs (Collier et al. 2011). Levucell SB has been found to increase growth and reduce heat stress in cattle and pigs. It is hypothesised that LSB will increase growth performance of finisher pigs over summer in low digestible energy (DE) diets more so than high DE diets.

Eight hundred and forty Improvac vaccinated male pigs (PrimeGro™ Genetics, 57.8 kg ± 0.66 kg) were randomly allocated to four dietary treatments in a 2 × 2 factorial design (high and low DE level and LSB addition at 0 or 10⁹ CFU/kg), with Pen as the experimental unit. Pigs were housed in commercial pens (14 pigs/pen and 15 pens/treatment) with feed and water available ad libitum. The experiment commenced in February 2016 and over the 42 day experimental period there were 25 days with maximum pen temperatures exceeding 30°C and 12 days over 35°C. Diets contained 14.0 or 12.8 MJ DE/kg and 0.62 g standardised ileal digestible lysine/MJ DE. Pen weights and feed use was measured at 0, 21 and 42 d. Carcass fat depth (P2) was measured after slaughter. Statistical analysis was conducted using ANOVA (SPSS v21.0, IBM, Armonk, NY, USA).

As expected, pigs fed diets with higher DE grew faster and more efficiently and had fatter carcasses than those fed a low DE diet (Table 1). The addition of LSB at 10⁹ CFU/kg increased feed intake of pigs fed low-energy, but not high-energy, diets. Pigs fed LSB also had improved feed efficiency, particularly in higher DE diets. There was an interaction between DE and LSB for carcass fat at the P2 site. Pigs fed high DE diets with LSB were leaner than those without LSB, whereas in low DE diets LSB addition produced a fatter carcass. The results support the hypothesis that in hot weather, LSB increased feed intake in pigs fed a low energy diet, most likely due to reduced heat increment during digestion. However, in high DE (high starch) diets feed efficiency is improved. The use of the live yeast Levucell SB is a useful tool for maintaining pig growth performance over hot weather.

Table 1.  Growth performance of finisher pigs fed two digestible energy (DE) levels with and without Levucell SB (LSB)