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Interrelationships of Exogenous Porcine Growth Hormone Administration and Feed Intake Level Affecting Various Tissue Levels of Iron, Copper, Zinc and Bone Calcium of Growing Pigs

U.S. Department of Agriculture^,3,4,, Beltsville, MD 20705

Abstract

Trace mineral status was evaluated in a 2 x 3 factorial treatment array with a total of 34 barrows growing from 25 to 55 kg live weight. Treatments included three levels of feed intake (100, 80 and 60% of ad libitum intake) and exogenous pituitary growth hormone (pGH) therapy (0 and 100 µg/kg BW daily). Blood was collected prior to slaughter for the determination of hematocrit and serum trace metal concentrations; tissues (liver, heart, kidney, bone and muscle) were obtained when pigs were slaughtered at 55 kg. Hematocrits and serum Fe were lower in pGH-treated pigs than in controls at all levels of feed intake. Serum Cu was increased by feed restriction but was not altered by pGH therapy. The concentration of serum Zn was not affected by either treatment. Concentrations of hepatic Fe and Cu were lower in pGH-treated pigs than in controls but were higher in feed-restricted pigs than in ad libitum-fed pigs. However, the total amounts of hepatic Fe and Cu were similar in pGH-treated pigs to concentrations in controls. The concentration of hepatic Zn was not influenced by either pGH treatment or feed intake. Femur weights were marginally greater in pGH-treated pigs, probably due to elevated water content. Iron concentration in bone was higher in pGH-treated pigs than in control pigs, whereas Ca, Cu and Zn were not influenced by pGH treatment or feed restriction. Feed intake and pGH treatment did not influence the concentrations of Fe, Cu or Zn in muscle. These findings indicate that pGH therapy affects the metabolism of Fe but has little impact on the overall composition of body ash.

¹ USDA, ARS, Beltsville Agric. Res. Center, Livest. and Poult. Sci. Inst., Nonruminant Anim. Nutr. Lab., Beltsville, MD 20705.

² Anim. Res. Inst., Werribee, Victoria 3030, Australia.

³ Special appreciation is extended to D. J. Bolt for his assistance in obtaining pituitary-derived porcine growth hormone and to S. Blanchard for statistical analyses. The authors acknowledge the excellent technical assistance of C. Dove and E. G. Brown. M. L. Failla is thanked for helpful discussions and critical review of this manuscript.

⁴ Mention of trade name, proprietary product or vendor does not constitute a guarantee or warranty of the product by USDA or imply its approval to the exclusion of other products or vendors that also may be suitable.