Maintaining finisher pig performance without dietary organic copper with a mannan-rich fraction of Saccharomyces cerevisiae

Copper (Cu) has been included in growing pig diets for many decades to improve growth performance and general health (Barber et. al. 1955). Copper sulphate (CuSO₄) use is still widespread and organic forms of Cu are also common with increased bioavailability facilitating lower inclusion rates (Coffey et al. 1994). The potential for co-selection of metal and antibiotic resistance (Baker-Austin et al. 2006) as well as environmental build up from pig excretions still raise concern over Cu use. Edwards et al. (2014) evaluated the use of Actigen™ [a mannan-rich fraction derived from a strain of Saccharomyces cerevisiae (Alltech Inc, Nicholasville, KY, USA)] as a total replacement for CuSO₄ in pig diets from 29 kg to sale. The authors reported similar growth performance and survival between the Cu treatment (200 ppm Cu as CuSO₄) and Actigen™ (Actigen™ step-down program 400 ppm/200 ppm, 38 days/42 days). The present study aimed to further explore the use of Actigen™, specifically to determine the replacement and additive effects when included in finisher diets containing organic Cu. The study tested the hypotheses that growth performance, survival and carcass weight would be similar with the total replacement of organic Cu with Actigen™, and that no additive effects would occur from the inclusion of both Actigen™ and Cu in the finisher diet.

A total of 697 male pigs (PrimeGro™ Genetics, Corowa, NSW) were housed in commercial finisher facilities in pens of 12–13 pigs. At 16 weeks of age, all pens were weighed (57.9 ± 0.59 kg; mean ± SE) and randomly allocated (18 pens/treatment) to one of three isoenergetic and isonitrogenous (13.0 MJ digestible energy (DE)/kg, 0.56 g available lysine/MJ DE) diets: Control (standard Bioplex Cu diet; 100 ppm Cu proteinate); Actigen™ (200 ppm) plus Cu (100 ppm Bioplex Cu); and Actigen™ (200 ppm). Diets were offered ad libitum from 16 weeks of age until slaughter at 22 weeks. Growth performance, feed intake and feed efficiency were recorded on a pen basis. Mortality and morbidity were analysed for association with dietary treatment using Chi-square analysis. All other data were analysed using ANOVA with the pen as the experimental unit (Genstat 16th Edition; UK).

Growth performance and measured carcase characteristics were not significantly different between dietary treatments over the entire test period (Table 1). There was a trend for reduced pig mortality and removals for morbidity from the combined Cu plus Actigen™ diet: 6.5%, 3.0% and 7.7% for the three diets, respectively (χ² = 5.16, P = 0.076). This was primarily due to a trend for a reduction in pigs removed for tail bites during the final four weeks of the study (χ² = 4.77, P = 0.092).

Table 1.  Influence of dietary treatment on growth performance and carcass characteristics in grower/finisher pigs grown from 16 weeks to 22 weeks of age

This study suggests Actigen™ may be considered as a replacement for organic Cu in finisher diets without negative effects on growth performance, feed efficiency or carcass characteristics. No additive effects were apparent with the combination of Cu plus Actigen™ on growth performance, feed efficiency or carcass characteristics. The trend for reduced morbidity with the Cu plus Actigen™ combination of was of interest and may warrant further investigation.