FBA Issue 23: November / December 2008
Trace mineral supplementation in hog rearing: Less is better
by  B. FUCHS, P. SCHLEGEL &  U. GEIER,   Wroclaw University of Environmental and Life Science, Wroclaw, Poland; Josera of Kleinheubach, Germany and Pancosma of Geneva, Switzerland.
Strategies in trace mineral (Cu, Fe, Mn and Zn) supplementation to sow, piglet and growing/finishing pig diets are constantly discussed for optimization. In the European Union, the safety margins between officially recommended concentrations and legal maxima (EC Regulation 1334/2003) have become very narrow in order to limit environmental pollution, mainly for Cu and Zn. Mateos et al. (2005) investigated the current trace mineral supplementations on the Iberian peninsula and analyzed concentrations generally beyond official recommendations. This practice suggests a lack of confidence by industry in the recommendations currently available, which originate on research conducted more than 30 years ago and are most likely no longer appropriate. 
Within the EU context the dietary trace minerals have to be utilized at a maximum rate by animals to limit potential trace mineral deficiencies. To such conclusions also came several scientists during the first International Symposium of Trace Elements in Animal Production Systems held in Geneva on the 14th and 15th of June 2007. The replacement of inorganic trace mineral sources by iso-dosed or reduced levels of organic sources are mostly recommended and have been successful in not impairing animal productivity as Close (2003); Creech et al. (2004); Revy et al. (2004) or Pierce et al. (2005) communicated. 
Two types of organic trace mineral (OTM) forms are currently allowed in the European Union either using hydrolyzed soy protein or glycine as ligand to the mineral. The bioavailability of these two types was recently compared in piglets by two research groups using apparent absorbability, blood and plasma contents and performance as criteria (Männer et al., 2006; Ettle et al. 2008). The mineral bioavailability of the tested glycinate was clearly improved when compared with the several soy protein based sources.
Within this context, a study was conducted by the Wrocław University of Environmental and Life Sciences in Poland to measure the effect of reduced trace mineral supplementation using partially OTM either in form of soy based chelates or glycinates on the fertility, performance and status of sows and their offspring.
Comparative study of reduced trace mineral supplementation using two organic sources in sows and their offspring
Sows were allocated to three dietary treatments on their insemination day, according to their body weight (BW) and the litter weight from previous lactation. Their offspring remained on the same treatment until reaching slaughter weight. Piglets were injected twice with Fe (day 4, 200 mg Fe-dextran, Ferrovit; day 21, 7 mg Fe3+, Suiferrovit). At weaning (day 21) piglets were fed their first solid feed and allocated within each treatment to 3 pens according to their body weight (light, medium, heavy). On day 90, piglets were moved from post-weaning pens to grower/finisher pens. 
All diets were based on wheat, barley, triticale and soybean meal. Sows were fed a gestation diet (11.5 MJ ME, 13.5% CP) restrictively, followed by a lactation diet (13.0 MJ ME, 17.2% CP) ad-libitum. The offspring were fed from day 21 to 42 a prestarter (13.8 MJ ME, 19.0% CP) diet, from day 43 to 72 a starter I (13.5 MJ ME, 20.0% CP) diet, from day 73 to 90 a starter II diet (13.2 MJ ME, 17.9% CP), a grower diet (13.0 MJ ME, 17.5% CP) from day 91 to 135 and a finisher diet (12.7 MJ ME, 16.0% CP) from day 136 until slaughter.
The three dietary treatments were defined as "Control" (inorganic trace mineral supplementation at common industry levels); "Chelate" (inorganic and soy protein based OTM supplementation at reduced levels) and "Glycinate" (inorganic and crystalline glycinate OTM supplementation at reduced levels). The treatment trace minerals were supplemented via mineralfeeds (Sauenglück, Sauen-Profi, Ferkel-Profi or Josamin) provided by Josera, Kleinheubach, Germany. The incorporated crystalline glycinate sources (B-TRAXIM® 2C) were provided by Pancosma, Geneva, Switzerland. 
All collected data were run through an analysis of variance and differences between treatment means were tested using Ducan test. Average values differing with letters in small superscripts were significant (P<0.05); Average values differing with letters in capita superscripts were significant (P<0.01). 
Sow and newborn piglet performance and status
Reducing Cu, Mn and Zn supplementation and using to half OTM in gestating and lactating sows did not negatively affect their performance nor the ones of their offspring (Table 2). In contrary, the treatments Chelate and Glycinate even increased (P<0.05) sow's success of insemination 30 days after farrowing the piglets on study.
During pregnancy, sows gained in average 40 kg BW without treatment differences (data not shown), but during lactation, sows fed OTM, especially Glycinate tended to loose less weight. The offspring from sows fed OTM were heavier (P<0.05) at birth, which induced less removals (P<0.05; when BW on day 2 was < 1.2 kg). There was no significant difference between Chelate and Glycinate to these parameters, but there was a consistent numerical advantage for Glycinate.
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