150 J. Indonesian Trop. Anim. Agric. 48(2):150-158, June 2023 J I T A A Journal of the Indonesian Tropical Animal Agriculture Accredited by Ditjen Riset, Teknologi dan Pengabdian kepada Masyarakat No. 164/E/KPT/2021 J. Indonesian Trop. Anim. Agric. pISSN 2087-8273 eISSN 2460-6278 http://ejournal.undip.ac.id/index.php/jitaa 48(2):150-158, June 2023 DOI: 10.14710/jitaa.48.2.150-158 The stressing effect of shearing in mid-pregnancy of Zandi ewes on live weight and body sizes of twin lambs at the time of birth M. Kalhor, N. Eila * , A. Zarei, and A. Noshary Department of Animal Science, Faculty of Agriculture and Natural Resources, Islamic Azad University, Karaj Branch, Karaj, Iran Corresponding E-mail: nima.eila@kiau.ac.ir Received February 08, 2023; Accepted May 06, 2023 ABSTRACT This research investigated the effect of stress of mid-pregnancy shorn Zandi ewes on the live birth weight and body sizes of twin lambs. A total of 96 Zandi ewes, confirmed pregnant with twins, were randomly allocated on day 80 of pregnancy into 4 groups, each group containing 6 replicates (each replicate containing 4 sheep). The experimental groups included: 1. Control, 2. Crutched, 3. Sham-Shorn, and 4. Shorn. Blood cortisol concentrations of the ewes in the experimental shorn treat- ment group increased significantly compared to control (P<0.05). The average length of pregnancy in the ewes of the shorn treatment group was 2 and 1.5 days longer than the control and Sham-Shorn groups (P<0.05). Lambs born from ewes given the shorn treatment were heavier at birth as compared to the lambs of the other treatments, as well as having longer body lengths, arms, and legs (P<0.05). In general, the results showed that the ewes that were shorn in mid-pregnancy had a higher cortisol con- centration, and it had a significant effect on the birth weight and sizes of the lambs compared to other treatments. Keywords: Lamb, Live weight, Shearing, Stress, Zandi ewes INTRODUCTION The survival of lambs is affected by lamb birth weight and size as well as by the maternal behavior of the ewe. The main reasons for death of lambs include difficult birth, starvation, lack of acceptance by the mother ewe, and low birth weight (Hinch and Brien, 2013; Slozhenkina et al., 2020). Lamb birth weight has a linear rela- tionship with survival rate, with the light lambs have the highest mortality rate (Nowak and Piondron, 2006). It was reported that the birth weight range suitable for lamb survival was from 3 to 5.5 kg for New Zealand hill sheep (Dalton et al., 1980). In previous studies, it has been deter- mined that lambs with a birth weight of less than 3 kg are at a high risk of starvation, and exposure to starvation due to insufficient body reserves and reduced body strength. Additionally, lambs that weigh more than 5.5 kg experience more starvation, birth defects, cardiac complications and difficult birthing (Nowak and Poindron, 2006). Kerslake et al. (2005) noted that the aver- age weight of twin and triplet lambs that died