The effect of hydroxychloride trace minerals on the growth performance and carcass quality of grower/finisher pigs: a meta-analysis.

The current study compared the effect of hydroxychloride trace minerals (HTM) with the effect of inorganic trace minerals (ITM) on growth performance and carcass quality in grower-finisher pigs. The results of 6 studies conducted throughout Europe were combined into one meta-analysis. All included studies were performed using pigs from about 19 kg of body weight until slaughter. In all studies, 2 different mineral sources were compared, HTM and sulfates as ITM. Zn from either HTM or ITM was added at a level of 80 ppm to the diet, and Cu was added at a level of 15 ppm from the same source as Zn. In most studies, an additional treatment was included in which 20 ppm Zn was used from either source in combination with 15 ppm Cu from the same source. Diets were fed in 3 phases according to local commercial standards. The body weight, average daily gain, average daily feed intake, and gain:feed ratio were measured at the end of each phase. At the end of each study, the carcass yield, back fat thickness, and lean meat percentage were measured at commercial slaughterhouses. The meta-analysis was conducted using a MIXED model in SAS taking into account the within-study and between-study variation. The comparison was done only between HTM and ITM added at the same Zn level. No statistical differences were observed for growth performance or carcass characteristics between the mineral sources in pigs fed 20 ppm Zn. When 80 ppm Zn was used, a significant improvement in lean meat percentage was observed in pigs fed HTM compared with pigs fed ITM. In the overall study period, there was a tendency towards an increased gain:feed ratio in pigs fed 80 ppm Zn from HTM. In the last feeding phase, before slaughter gain:feed ratio and average daily gain were both significantly improved by 3.9%. In conclusion, HTM addition improved growth performance and lean meat percentage in grower-finisher pigs.