PSXII-19 - Influence of dietary copper concentration and liver sampling location on liver copper concentrations in three breeds (Gulf Coast Native, Suffolk x Hampshire, and Jacob) of sheep.

Abstract: A total of 27 male sheep from three different breeds: 1) Gulf Coast Native (GCN; n=9 wethers), 2) Suffolk x Hampshire (SHC; n=9 wethers), and 3) Jacob (JCB; n=9 intact males) approximately 9 months of age, (38,16 ± 2,43 kg) were stratified by body weight and breed into 3 treatment groups to examine the impact of breed, supplemental copper (Cu) dose, and liver sampling location on liver Cu concentrations. On d 0 of the experiment, liver biopsies were collected from 5 sheep per breed and analyzed for Cu concentrations. Animals were housed in individual pens and received 2% of BW of a pelleted concentrate containing the appropriate Cu treatment once daily and hay in amounts to allow ad libitum access to hay over a 24h period. Treatments consisted of: 1) low Cu (LCu; 15.3 mg Cu/kg DM), 2) moderate Cu (MCu; 17.7 mg Cu/kg DM), and 3) high Cu (HCu; 23.8 mg Cu/kg DM) from CuSO₄∙5H₂O. On d 50 of the experiment, all animals were weighed and transported to an USDA inspected abattoir and harvested. Following harvest, samples were obtained from the left and right lobes of the liver and thoroughly washed with phosphate-buffered saline. All liver samples were dried, ashed, and reconstituted in 5 mL of 1.2 N HCl for Cu analysis. Data were analyzed as a randomized block design using the MIXED procedure in SAS with individual animal as the experimental unit. There was a three-way interaction between breed x treatment x liver lobe (P < 0.04). The right liver lobe in HCu JCB sheep had greater (P < 0.05) Cu concentrations compared to the left liver lobe. Both the left and right lobes of the liver had greater (P < 0.001) Cu concentrations compared to the initial liver Cu concentration in MCu JCB sheep. The right liver lobe of HCu GCN sheep tended (P < 0.07) to have greater liver Cu concentrations compared to the left liver lobe. The Cu concentration in the right liver lobe tended (P < 0.09) to be greater in MCu sheep compared to the left liver lobe. Liver Cu concentrations within the right lobe of HCu GCN sheep were greater (P < 0.05) than liver Cu concentrations in the right and left liver lobe samples in LCu GCN sheep. Liver Cu concentrations in SHC sheep were not influenced by treatment. Future research examining the impact of breed and Cu supplementation on the molecular mechanisms associated with Cu absorption, storage, and excretion is warranted.