Pre-partum shearing of ewes under pastoral conditions improves the early vigour of both single and twin lambs

Abstract

This study tested the hypothesis that ewes bearing single or twin lambs shorn at 70 or 120 days of pregnancy would give birth to lambs more vigorous than those born to unshorn ewes, increasing the chances of lamb survival. This was tested in two experiments. In the first, 57 adult Corriedale ewes bearing single lambs were allocated to three treatments; shearing at Day 70 of gestation (S70, n = 18), shearing at Day 120 of gestation (S120, n = 19) or unshorn (US, n = 20). In the second, 57 Corriedale ewes bearing twins were allocated to the same treatments: S70, n = 18; S120, n = 20; or US, n = 19. All ewes grazed native pasture until penned and fed individually to requirements during the last 10 days of pregnancy. Gestation length, lamb birthweight, lamb behaviour during their first hour of life, blood glucose and colostrum amount and composition were measured. In the first experiment, with single lambs, birthweights were similar (4.8, 4.7 and 4.7 kg for S70, S120 and US ewes, respectively; s.e. = 0.17, P = 0.47) and the ewes had lengths of gestation of 149 ± 0.6, 148 ± 0.5 and 147 ± 0.6 days respectively. Seventy-eight percent of S70 and 61% of S120 lambs sucked compared with 21% of US lambs (P < 0.001). In the second experiment, with twin lambs, S70 lambs were heavier than S120, which were heavier than US lambs (3.9, 3.4 and 3.1 kg; s.e. = 0.1, P < 0.0001). Ninety-seven percent of S70 and 92% of S120 lambs stood in their first hour of life compared with 68% of US lambs (P < 0.05). Sixty-seven percent of S70 and 63% of S120 lambs sucked compared with 22% of US lambs (P < 0.001). The length of gestation was 148 ± 0.4, 147 ± 0.5 and 144 ± 0.5 days for S70, S120 and US ewes. In both experiments there was no difference in the amount or quality of the colostrum produced by the ewes of the different treatments. We conclude that pre-partum shearing improves lambs’ behaviour independently of their birthweight and suggest that this could be because the lambs are more physiologically mature at birth.

Epigenetics and developmental programming of welfare and production traits in farm animals

“…Shearing pregnant ewes has consistently been reported to increase lamb birthweight, particularly if conducted during early to mid-gestation ( Figure S3). Associated with this response are increases in maternal feed intake, gestation length and maternal plasma glucose concentrations (Symonds et al 1988;Morris et al 2000;Keady and Hanrahan 2009;Banchero et al 2010). Although shearing is associated with a robust stress response in the ewe, these data suggest that its primary effect on birthweight is through increased feed intake, and hence nutrition of the developing lamb.…”

“…In goats, aversive handling in pregnancy led to placental alterations and increased fetal loss compared with gentle or minimal handling (Baxter et al 2016), whereas positive handling improved neonatal behavioural development. In addition, shearing studies in late gestation that did not elicit an increase in birthweight have been reported to improve lamb behavioural progression to sucking (Banchero et al 2010), although none of the maternal stress studies reported changes in lamb survival. The mechanisms underlying these effects are largely unknown.…”

Effect of Shearing During Pregnancy on Productive Performance in the Post-Partum Period of Ewes on Extensive Husbandry

“…This finding agrees with the study by Sphor et al (26) , who found a mean increase of 22.2% in the milk yield of ewes that were sheared at 53 days of pregnancy compared to non-sheared ewes. Finally, we verified lambs from sheared ewes were more active, as 78% of them fed in the first hour of life compared to only 21% of lambs from control group, suggesting more vigor and a greater stimulus to the mother to produce more milk (5) . In conclusion, Corriedale sheep raised under extensive system, sheared around 74 days of pregnancy, showed more efficiency in developing heavier lambs at birth and during the initial phase of growing, consequently minimizing the risk factors that contribute to perinatal mortality.…”

“…It is believed that the effect of shearing on placenta size occurs when it is carried out before the placentation period is complete (28) . Banchero et al (5) found an increase of 16% in the placenta weight in ewes sheared at 70 days of pregnancy, with a resulting increase of 8.2% in the body weight of the newborn lambs. Most works suggest shearing, when carry out up to 90 days of pregnancy, can contribute to a higher development of fetus and placenta (12) .…”

“…In New Zealand, perinatal death rate is over 80% in lambs born with body weight lighter than 2.0 kg and the survival rate is higher in animals born with a body weight heavier than 3.0 kg (3) . Some strategies can be adopted in order to diminish perinatal death in lambs, such as improving weight at birth (4) , which involves enhancing fetal development (5) , especially in periods of scarce grass or in winter. For this purpose, shearing during gestation has been used as an alternative, because it alters the metabolism and the placenta of ewes (6) .…”