Shearing Sheep to Improve Growth Performance

Faculty Mentor

Jay Daniel


The purpose of this study was to determine if average daily gain (ADG) is improved in shorn lambs versus non-shorn lambs in the summer months in the upper Midwestern United States. Forty-nine purebred Hampshire and Columbia ram (n = 10 Hampshire and 4 Columbia) and ewe (n = 22 Hampshire and 13 Columbia) lambs were grouped by breed, sex and initial weight (49.6 ±1.6 kg) into shorn (n=26) and non-shom (n=23) groups. After shearing (3 June 2004), shorn sheep had approximately 0.2 cm of woolcover. Lambs were weighed 1, 29, and 57 days following shearing. During the first 28 day period following shearing (period 1), there was no difference in average daily gain between shorn and non-shom lambs (0.36 ± 0.02 vs 0.37 ± 0.02 kg/day, respectively; P=0.8289). In the second 28 day period (period 2), shom lambs had a greater average daily gain than non-shom lambs (0.46 ± 0.03 vs 0.42 ± 0.03 kg/day, respectively; P=0.0362). Period 2 had greater mean (20.56 vs. 17.78 oC, respectively), minimum (8.67 vs 6.72oC, respectively), and maximum (31.94 vs. 32.5oC, respectively) ambient air temperature and greater mean humidity (73.97 vs. 68.2 %, respectively) than period 1. The calculated thermal heat index (THI) was also greater in period 2 than period 1 (66.9 vs. 62.24, respectively). These data indicate that shorn lambs grow more rapidly than non-shom lambs during periods of elevated temperature, humidity, and THI.

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