Effects of late gestation shearing on body weight, feed intake, and plasma metabolite concentrations in Rambouillet ewes managed outdoors during winter

Authors: MURPHY, THOMAS - Montana State University; STEWART, WHIT - University Of Wyoming; SMITH, CASEY - Montana State University; Taylor, Joshua - Bret

Submitted to: Animal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2018
Publication Date: 7/31/2018
Citation: Murphy, T.W., Stewart, W.C., Smith, C.G., Taylor, J.B. 2018. Effects of late gestation shearing on body weight, feed intake, and plasma metabolite concentrations in Rambouillet ewes managed outdoors during winter. Animal. 13(3):600-605. https://doi.org/10.1017/S175173111800191X.
DOI: https://doi.org/10.1017/S175173111800191X

Interpretive Summary: In the northern Rocky Mountain regions of the U.S., many producers shear sheep near (before) the lambing season. Shearing removes the insulative property of a ewe’s fleece and may result in decreased core body temperature in cold climates. Therefore, a common husbandry practice involves providing pregnant ewes with a higher plane of nutrition immediately after shearing in an attempt to limit the negative effects of cold stress. In order to determine if additional nutrition after shearing is warranted, we investigated the effects of shearing pregnant ewes during late winter/early spring on body weight and voluntary feed intake. Under the conditions of the present study, shearing during late pregnancy did not alter ewe body weight or feed intake. Considering the climatic conditions during this study and based on the results, we suggest that finewool-type ewes that are managed in a drylot after shearing may not require additional feed resources in an attempt to lessen the severity of cold stress. We do, however, acknowledge that if climatic conditions were more severe and(or) ewes had been managed on pasture, body weight and voluntary feed intake may have responded differently than in the present study.

Technical Abstract: The majority of lambs in the U.S. are born from late winter to early spring and pregnant ewes are generally sheared in the last third of pregnancy. While there are benefits to shearing prior to parturition, shorn animals may be more vulnerable to the cold, highly variable climatic conditions associated with these seasons. The objective of this study was to determine if late gestation shearing induces differences in individual BW, DM intake (DMI), and plasma metabolite concentration of finewool ewes managed outdoors during winter. Thirty-six mature, pregnant Rambouillet ewes (3.8 +/- 0.45 year; 76.8 +/- 11.4 kg) were managed in a drylot with ad libitum access to pelleted alfalfa in bunks capable of measuring individual daily DMI. The treatment group consisted of ewes sheared at approximately 5 weeks before estimated parturition date (shorn; n = 18). The control ewes (unshorn; n = 18) were sheared following completion of the trial approximately 2 weeks before estimated parturition date. Blood was collected on days 0, 7, 14, and 21 of the trial, and plasma was isolated and analyzed for non-esterified fatty acid (NEFA), beta-hydroxybutyrate (BHB), and glucose (GLU) concentrations. There was no effect of shearing on ewe BW or DMI during the trial (P = 0.35). Plasma NEFA and GLU concentrations were similar (P = 0.36) between shearing groups, though plasma BHB concentration was 1.08 mg/dl greater (24.1%; P < 0.01) in unshorn ewes. Lamb BW at birth was not affected (P = 0.30) by ewe shearing treatment. Under conditions of this study, late-gestation shearing had little effect on economically important aspects of sheep production.