PSIII-8 Shearing during early mid-gestation increases umbilical blood flow and fetal size in ewes.

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, SS) and divided in singleton (S: n=4; SS: n=4), twins (S: n=5; SS: n=5) and triplets (S: n=5; SS: 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, tin 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 SS, 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 SS, respectively. There was no significant treatment by day interaction or main effect of treatment (P ≥ 0.10) in ALL or M for fetal abdominal distance. At birth, there were no differences (P ≥ 0.27) between S and SS 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 SS ewes (5.02 vs 4.56 ± 0.18 kg, respectively). Our findings suggest that shearing pregnant ewes on day 50 of gestation increases UBF and fetal size (BP) and tends to increase birthweight in lambs born from multiple carrying pregnancies.