Document Type

Thesis - Open Access

Award Date

2025

Degree Name

Master of Science (MS)

Department / School

Veterinary and Biomedical Sciences

First Advisor

Manuel Alexander Vasquez-Hidalgo

Abstract

Studies outside the USA have reported that shearing pregnant ewes during mid to late gestation increases lamb birth weight. Our hypothesis was that shearing pregnant ewes on day 50 of gestation would increase umbilical blood flow (UBF), fetal size, lambing and placental weights. Twenty-eight Polypay ewes were randomly assigned to two treatments: shorn (S) and sham-shorn (Control, CON) and divided in singleton (S: n=4; CON: n=4), twins (S: n=5; CON: n=5) and triplets (S: n=5; CON: n=5). Umbilical BF and fetal and placental measurements were obtained via ultrasonography every 10 days from day 50 to 110 of gestation. Lamb birth and cotyledonary weights were recorded. Data overall (ALL; singletons, twins and triplets) and by multiple pregnancies (M; twins and triplets) were analyzed using the MIXED procedure of SAS. There was no significant (P = 0.51) treatment by day interaction in ALL or M on UBF. However, in both, here was a main effect of treatment (P < 0.05) with UBF tending to be greater (P ≤ 0.10) on days 90 and 100 and being greater (P = 0.03) on day 110 (ALL: 282.21 vs 238.76 ± 12.96 ml/min; M: 317.55 vs 227.88 ± 21.37 ml/min) in S compared to CON, respectively. There was no significant treatment by day interaction or main effect of treatment (P ≥ 0.37) in ALL or M for placentome size. There was no significant (P ≥ 0.11) treatment by day interaction or main effect of treatment for fetal biparietal distance (BP) in ALL. There was no significant (P = 0.81) treatment by day interaction for BP in M, however, there was a main effect of treatment (P = 0.01) with BP tending (P = 0.07) to be greater on day 60 and being greater (P ≤ 0.05) on days 80 (36.92 vs 34.08 ± 0.98 mm), 90 (43.03 vs 39.59 ± 0.98 mm) and 110 (51.27 vs 48.32 ± 0.98 mm) in S vs CON, respectively. There was no significant treatment by day interaction or main effect of treatment (P ≥ 0.10) in ALL or M for fetal AD. At birth, there were no differences (P ≥ 0.27) between S and CON in cotyledonary weights. There were no differences (P ≥ 0.22) for lamb weights at birth or 24h in ALL. There was no difference (P = 0.17) in lamb weights at 24h in M. However, M lambs born from S ewes tended (P = 0.08) to be heavier at birth compared to lambs born from CON ewes (5.02 vs 4.56 ± 0.18 kg, respectively). There was a tendency (P = 0.10) for lambs from S ewes to be heavier at 60 days of age (34.73 ± 1.67 kg) compared with lambs from CON ewes (30.81 ± 1.61 kg). Our findings suggest that shearing pregnant ewes on day 50 of gestation increases UBF and fetal size (BP) and tends to increase birth and weaning weights in lambs born from multiple carrying pregnancies.

Publisher

South Dakota State University

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Rights Statement

In Copyright