ABSTRACT
The study was conducted to investigate the effect of different forms of trivalent chromium on growth hormone (GH) secretion and pituitary mRNA expression in finishing pigs.A total of 96 finishing pigs with an initial average body weight 65 kg were blocked by body weight and randomly assigned to four treatments with three replicates.Pigs were offered one of four diets including a control diet or the control diet supplemented with 200 μg/kg chromium from either chromium chloride (CrCl3),chromium picolinate (CrPic) or Chromium nanocomposite (CrNano) for 40 days.During the trial,all pigs were given free access to feed and water.At the end of the feeding trial,blood samples were taken via auriculares at 15 min intervals for 3 hours.Eight pigs from each treatment were slaughtered for backfat thickness and longissimus muscle area (LMA),and three pituitaries were collected to determine GH mRNA level.The results showed that average daily gain of pigs fed supplemental CrNano was increased by 6.31 (P<0.05),feed gain ratio was decreased by 4.61% (P<0.05),backfat thickness was decreased by 24.32 % (P<0.05),and LMA was increased by 20.22% (P<0.05).The results of GH dynamic secretion showed that supplemental CrNano increased the mean level,lowest value,peak value and peak duration of GH by 42.62% (P<0.05),87.94%(P<0.05),26.60% (P<0.05),and 17.19%(P<0.05),respectively.The mean level and peak value of GH in pigs fed Supplemental CrPic was increased by 36.58% (P<0.05),27.18%(P<0.05),respectively.Pituitary mRNA expression of GH in pigs fed diet containing chromium from CrNano was increased by 27.63%(P<0.05).These results indicated that chromium nanocomposite increased GH mRNA expression and secretion in finishing pigs,through which growth was promoted and carcass characteristic was improved.