133 Effect of terminal sire breed on grazing performance, parasitism and market grade of crossbred lambs

Abstract

Abstract Improvements in growth and carcass conformation through terminal sire crossbreeding systems may improve lamb value in a pasture-based system. Therefore, the aim of this study was to compare the effects of different terminal sires on parasitism, growth, composition, and marketability of grazing lambs. Suffolk (SU; n = 2) and Texel (TX; n = 2) sires were mated to commercial ewes at the WVU Organic Farm. April-born lambs were managed on pasture as one group until weaning in midJune, then were separated into 3 replicates per sire breed. Lambs were rotationally grazed for 93 d with paddock movement every 10 d. Lambs were supplemented at a rate of 2% of bodyweight with a 16% CP corn-soybean meal supplement. Weights were collected at weaning and then weekly for the duration of the study. Fecal egg counts (FEC) and FAMACHA scores were collected biweekly. Lambs were de-wormed when FAMACHA score was ≥ 3. Ultrasound measures of rib eye area (REA) were obtained at study conclusion and lambs were marketed at a graded auction. Sire breed did not impact weaning weight or growth rate throughout the test. Fecal egg count was slightly higher in TX vs. SU-sired lambs (257 vs 191 eggs/g; P < 0.05). FAMACHA scores were lower in TX vs. SU-sired lambs (1.58 vs. 1.96; P < 0.0001). Fewer deworming treatments were necessary in TX-sired lambs at 10% (4/39) whereas as SU-sired lambs required 55% (22/40) (P < 0.0001). TX-sired lambs had greater REA (11.57 vs 9.42 cm2; P < 0.0001) and graded better at the saleyard. Grading was set to a 6 pt scale with higher equating to higher sale price. Lambs sired by TX rams graded 5.2 and SU-sired lambs graded 3.6 (P < 0.0001). These data demonstrate that Texel-sired lambs required fewer dewormer treatments and were compositionally more desirable when marketed