Are mineral supplements really necessary in grower-finisher diets?

Saturday, October 3, 2015

Research suggests that foregoing supplemental microminerals didn't have a negative effect on performance and that doing so offers producers an opportunity for cost savings

by JANICE MURPHY  

Feed represents the greatest cost in commercial swine production units. To maximize returns, producers work with their feed industry partners to formulate least-cost swine diets tailored to maximize growth rate and feed conversion efficiency. In North America, this has traditionally meant swine diets formulated with corn and soybean meal, particularly during the grower-finisher phase.

The current version of the NRC Nutrient Requirements of Swine (2012) indicates that micromineral levels and bioavailabilities for feed ingredients are variable and, in many cases, largely unknown. Accordingly, the micronutrient contributions of these ingredients are generally ignored while formulating diets, making it commonplace to supplement microminerals in excess of the pig's actual requirements.

Research at Ohio State University has investigated the effect of reducing copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) below and up to NRC requirements for grower-finisher pigs, and evaluated the effects of adding Zn or Fe. The goal of this research was to assess the level of these minerals on growth, feed efficiency, carcass characteristics and pork quality, as well as plasma and tissue mineral concentrations, and the liver antioxidant enzymes of which these minerals are a vital component.

Starting at an initial body weight of 24 kilograms, grower pigs were fed one of the following corn-soybean meal diets up to 115 kilograms body weight:

• basal diet without supplemental Cu, Fe, Mn, and Zn
• basal diet + 2.5 mg/ kg Cu, 50 mg/kg Fe, 1.5 mg/kg Mn, and 40 mg/kg Zn (50 per cent NRC)
• basal diet + five mg/kg Cu, 100 mg/kg Fe, 3 mg/kg Mn, and 80 mg/kg Zn (100 per cent NRC)
• basal diet + 25 mg Zn/kg
• basal diet + 50 mg Zn/kg
• basal diet + 50 mg Fe/kg.

The average daily gain, average daily feed intake and gain to feed were not affected by dietary treatment for each of the three dietary phases and throughout the overall trial.  (See Table 1.)

The results also showed (data not shown) that circulating plasma mineral levels were not significantly affected by dietary treatment. The activity of Cu/Zn superoxide dismutase (SOD) was not affected by the increasing micromineral levels. However, the activity of Mn SOD increased slightly to the 50 per cent NRC treatment level.

The level of Zn in the liver was significantly higher as dietary micromineral levels increased and also when Zn was added to the diet on its own. Liver, kidney, and heart Cu and Mn concentrations were similar regardless of the level of dietary micromineral. These results indicate that the additional levels of Cu, Fe, and Mn were not necessary for grower-finisher pigs and that the level of these minerals in a corn-soybean meal diet were sufficient, though there may be a need to provide
supplemental Zn to the diet.

Taken as a whole, these results suggest that feeding corn–soybean meal diets without supplemental microminerals did not have a negative impact on the parameters measured. The pigs in this experiment were healthy and fast-growing. The researchers did point out that, given a situation where disease and/or environmental stresses existed, there may be an increased demand for these minerals. In their estimation, providing these minerals at a rate of 50 per cent of the NRC recommendation (2.5 mg/kg Cu, 50 mg/kg Fe, and 1.5 mg/kg Mn) would be sufficient to meet the requirement of grower–finisher pigs, with perhaps some additional zinc.

Based on these results, it is clear that the availability of microminerals in a basic corn-soybean meal diet is greater than currently recognized. It is obvious that there are sufficient microminerals available to meet the grower-finisher pig's requirement for growth and there are no detrimental effects on carcass characteristics and pork quality.

Removing or decreasing supplemental microminerals in grower-finisher swine diets may allow swine producers the opportunity to reduce feed costs while maintaining the same level of growth and feed efficiency and therefore, increase their bottom line. BP

Janice Murphy is a former Ontario agriculture swine nutritionist who now lives and works in Prince Edward Island.

Sources:
Gowanlock, D.W, Mahan, D.C., Jolliff, J.S., Moeller, S.J. and Hill, G.M. 2012. Evaluating the NRC levels of Cu, Fe, Mn, and Zn using organic minerals for grower-finisher swine. J. Anim. Sci. 2013.91:5680–5686.
Gowanlock, D.W, Mahan, D.C., Jolliff, J.S. and Hill, G.M. 2015. Evaluating the influence of National Research Council levels of copper, iron, manganese and zinc using organic (Bioplex) minerals on resulting tissue mineral concentrations, metallothionei, and liver antioxidant enzymes in grower–finisher swine diets. J. Anim. Sci. 2015.93:1149–1156.