EFFECT OF SIRE AND DAM BREED ON COPPER STATUS OF FAT LAMBS

To determine the effect of breed on copper status of crossbred (Fl) lambs, a study was conducted using 187 crossbred wether lambs. Wether lambs were progeny of five ram breeds (Dorset, Finnsheep, Montadale, Romanov, and Texel) and two ewe breeds (Rambouillet and a composite breed [1/2 Columbia, 1/4 Suffolk, 1/4 Hampshire]). Diets were adjusted to decrease crude protein twice during the experimental period, with analyzed copper levels for the three diets of 5.2, 4.4, and 3.6 ppm. All means were adjusted to a constant carcass weight of 27.265 kg using a covariate analysis. Least squares means of the liver copper concentration for sire breeds ranged from 307 to 458 mug/g on a DM basis. Romanov- (307 mug/g) and Finnsheep-sired (327 mug/g) lambs had the lowest liver copper concentration, whereas Montadale-(359 mug/g) and Dorset-sired (360 mug/g) lambs were intermediate and Texel-sired (458 mug/g) lambs were significantly higher compared with other lamb breeds. Least squares means for total liver copper for the five ram breeds ranged from 69 to 101 mg. Finnsheep- (69 mg), Romanov- (72 mg), and Montadale-sired (80 mg) lambs were lowest, Dorset-sired (85 mg) lambs were intermediate, and Texel-sired (101 mg) lambs were higher (P < .02) compared with other lamb breeds for total liver copper. Least squares means for serum copper ranged from .86 to 1.05 ppm. Levels of serum copper were similar for Montadale- (.86 ppm), Finnsheep- (.90 ppm), Texel- (.93 ppm), and Dorset-sired (.94 ppm) lambs and higher (P < .02) for Romanov-sired (1.05 ppm) lambs. Progeny of composite ewes had lower (P < .01) serum copper (.88 ppm) than progeny of Rambouillet ewes (.99 ppm). At dietary copper levels fed in this experiment, Texel-sired progeny had higher liver copper levels than other breeds; however, both liver and serum copper levels for all breed types were in the normal nontoxic range.