Effects of level and source of copper on copper status of ewes and newborn lambs

Abstract

Experiment one was conducted to determine the Cu status of mature ewes fed two sources Of CU (CUS04 VS CU proteinate) at one of three levels (10, 20 and 30 mg/kg). Ewes were fed a basal diet containing cottonseed hulls, cottonseed meal, and cracked corn at 2.5% BW to meet NRC requirements for protein, energy, macroninerals, and macrominerals excluding Cu. Ewes fed Cu proteinate had higher (P <.05) ceruloplasmin (Cp) than those fed Cu sulfate (33.2 VS 28.2 [ ]M/min/L). Feeding up to 30 mg/kg Cu from these sources did not cause an observable Cu toxicity during the 73-d period. These data support the hypothesis that Cu from Cu proteinate and Cu sulfate have different biological availabilities. The primary goal of experiment two was to observe the effects of Cu deprivation in ewes during gestation on the thermogenic capabilities of neonate lambs. Twelve multiparous, twin bearing ewes were randomly assigned to low (7 ppm Cu) or high (26 ppm Cu) Cu treatment diets 3 mo prior to lambing. Ewes fed low-Cu diets received an oral drench containing ammonium tetrathiomolybdate beginning 2 mo prior to parturition. At the time of birth lambs were assigned to either a treatment (cc- methyl-DL-p-tyrosine, AMPT) or control (saline) injection group, in order to determine the effects of AMPT on the rectal temperatures of newborn lambs. Lambs were housed in environmental chambers (20'C) until time of slaughter (12 h of age). Low-Cu fed ewes had lower (P < .05) liver Cu concentrations than the high-Cu ewes (173 vs 802 ppm Cu, respectively). Lambs born to low-Cu fed ewes had lower (P < .05) liver Cu concentrations than lambs born to high-Cu fed ewes (130 vs 287 ppm Cu, respectively). Lambs from low-Cu fed ewes had lower (P < .05) rectal temperatures than lambs born to high-Cu fed ewes. The data showed that restricting Cu during gestation decreases the copper status of lambs, which in turn limits thermogenesis of newborn lambs.