The effect of mid-pregnancy shearing and litter size on lamb birth weight and postnatal plasma cortisol response

Corner, R.A.; Kenyon, P. R.; Stafford, KJ; West, D.M.; Oliver, Mark

doi:10.1016/j.smallrumres.2006.12.003

Cited by 13 publications

(14 citation statements)

References 43 publications

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“…However, Kenyon et al (2006) reported midpregnancy shearing to result in an increase in the survival rate of twin and triplet lambs due to a reduction in the proportion of lambs that weighed less than 3.5 kg at birth, which is economically important to the sheep industry. Despite the small difference of 100 grams in weight of the media made between the groups in our work, we work with lambs at 6 pounds, close to the results presented in the work of Corner et al (2007), although none of our animals have reached the final stage of pregnancy and rising off the weight was quite close to the findings of this author, both in late pregnancy in which he found in the middle of gestation was 3.5 kg and next to our work. Thus agreeing with the findings of the Kenyon et al (2006) shearing performed during pregnancy causes increase in birth weight of lambs.…”

Section: Discussionsupporting

confidence: 88%

“…A number of studies have showed that the midpregnancy shearing resulted in increase in the birth weight of both singleton and twin lambs. Corner et al (2007) showed that increases in lamb birth weight have generally been reported in either singleton (Morris et al, 2000;Kenyon et al, 2002;Revell et al, 2002) or twin-born lambs (Morris and McCutcheon, 1997;Smeaton et al, 2000;Kenyon et al, 2004), but less frequently for both (Kenyon et al, 2002;Corner et al, 2006). According to results obtained by Revell et al (2000), the shearing protocol results in an increase of over 1.0 kg in the mean birth weight of twin lambs in response to mid-pregnancy shearing, without any change in the birth weight of singletons.…”

Section: Discussionmentioning

confidence: 99%

“…Alternatively, shearing during mid-pregnancy has also been shown not to alter the proportion of lambs born weighing less than 3.5 kg (Corner et al, 2007).…”

Section: Discussionmentioning

confidence: 99%

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Mid-pregnancy ewe shearing and the effects on fetus liver and muscle glycoprotein deposits

Morini

Motta

et al. 2018

Anim Reprod

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The reason why shearing ewes in midpregnancy does increase the lamb birth weight is not completely clears. Therefore, we focused on the analyses of the deposition of glycogen in different fetal tissues to investigate this issue. Thirteen pregnant Australian Merino ewes, raised in native pasture, were separated in two groups. One group (n = 7) was shorn (SE) at 70 days of pregnancy, whereas another group (n = 6) remained unshorn (NSE). Cesarean section was conducted in all the ewes at near parturition, when placenta and fetuses sampling were collected. Placenta, liver and muscle samples were fixed and stained with glycoproteinreactive acid-Schiff acid for analysis under light microscopy. The quantification of these glycoproteins was performed with the support of a program that analyzes the measurement of the intensity of staining by field. Five random fields from each sample were used, where statistical analyzes was used as normal test T. Among the analyzed regions, the deposition of glycoprotein between SE and NSE groups was statistically different in the hepatic portal vein (54,499.23 µm 2 in SE and 34,830.73 µm 2 in NSE) and in the total muscle area of the sample fragment (41,128, 7 µm 2 and 31,942.7 µm 2 , respectively; P < 0.05). We conclude that shearing ewes at the 70th day of gestation lead to accumulation of glycoproteins in the liver and muscle of fetuses, which may be responsible for the increase in birth weights in that group.

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Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

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Mid-pregnancy ewe shearing and the effects on fetus liver and muscle glycoprotein deposits

Morini

Motta

et al. 2018

Anim Reprod

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“…Mid-pregnancy shearing in winter and under outdoor pastoral grazing systems results in an increase in the birth weight of both singleton (Morris et al, 2000;Sherlock et al, 2003;Corner et al, 2006 and2007b) and multiple-born lambs (Morris and McCutcheon, 1997;Smeaton et al, 2000;Kenyon et al, 2004;Corner et al, 2006 and2007a) and has been shown to increase lamb survival rates (Morris et al, 1999;Kenyon et al, 2006). The birth weight response to mid-pregnancy shearing has also been observed in winterhoused ewes (Dyrmundsson 1991, Cam andKuran, 2004) and summer-shorn, autumn-lambing ewes grazed on pasture (de Nicolo et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

The effect of different types of stressors during mid- and late pregnancy on lamb weight and body size at birth

Corner

Kenyon

Stafford

et al. 2010

Animal

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Mid-pregnancy shearing has consistently been shown to increase lamb birth weight, which can lead to an increase in lamb survival rates. However, shearing ewes during the winter months and under outdoor pastoral farming conditions can expose the recently shorn ewe to a greater risk of hypothermia. The aim of this study was to determine if exposure of ewes to repeated stressors, in mid-and late pregnancy, would result in an increase in lamb birth weight. This information may assist in the elucidation of the mechanism for the birth weight response to mid-pregnancy shearing, which in turn could assist in the design of management options to increase lamb birth weight without placing the ewe at risk. One hundred and forty-four twin-bearing Romney ewes were allocated to one of six mid-pregnancy treatments: control, isolation on 2 or 10 occasions, sham-shearing on 10 occasions, intramuscular cortisol injection on 10 occasions or shearing. Isolation, sham-shearing and cortisol treatments were conducted twice a week beginning, on average, day 74 of pregnancy and shearing occurred on day 76. During pregnancy, ewe treatment had no effect on ewe live weight. However, average ewe body condition scores were higher in the shorn group than in the sham-shorn or cortisol groups ( P , 0.05). Intramuscular injections of cortisol had a greater effect on ewe plasma cortisol concentrations than all other treatments ( P , 0.05). Shearing produced a greater plasma cortisol response than isolation 3 10 and sham-shearing ( P , 0.05). Ewe plasma cortisol responses decreased during the 5 weeks of isolation and sham-shearing but cortisol injections produced a greater response during the fifth treatment than the first or ninth treatments ( P , 0.05). Lambs born to shorn ewes were heavier and had a longer crown rump, forelimb and hind limb lengths than all other lambs ( P , 0.05). In addition, lambs born to ewes in the cortisol treatment were lighter than lambs born to control, isolation 3 2, isolation 3 10 and shorn ewes ( P , 0.05). The plasma cortisol concentrations observed for ewes injected with cortisol were far greater than those observed in all other groups, which is likely to explain the low birth weights of lambs born to ewes in that group. These results indicate that the mechanism by which mid-pregnancy shearing increases lamb birth weight is unlikely to be repeated stressors.

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“…Shearing ewes between days 50 and 100 of pregnancy has been identified as a technique that consistently increases lamb birth weight under pastoral (Kenyon et al 2004;Corner et al 2007) and winter-housed, sheep management systems (Dyrmundsson 1991). This increased birth weight has also been associated with an increase in lamb survival rates to weaning (Morris et al 1999;Kenyon et al 2006).…”

Section: Introductionmentioning

confidence: 99%

Birth weight effect in twin‐born lambs from mid‐pregnancy shearing is associated with changes in maternal IGF‐I concentration

Jenkinson¹,

Kenyon

Blair

et al. 2009

New Zealand Journal of Agricultural Research

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A number of studies have shown an increase in the birth weight of lambs in response to mid pregnancy shearing. The present study sought to determine whether the birth weight effect of midpregnancy shearing is mediated through changes in maternal insulin-like growth factor-I (IGF-I) and insulin-like growth factor binding protein-I (IGFBP-I) concentrations. Single-and twin-bearing ewes from three genetically divergent IGF-I lines were either left unshorn or shorn at a mean day 90 of pregnancy (P90). Maternal plasma concentrations of IGF-I and IGFBP-I were measured at P89, P108 Shearing increased the birth weight of twin lambs by over 350 g (P < 0.05) without having any effect on singleton birth weight. The increased birth weight of twin lambs born to shorn ewes was associated with a decline in maternal plasma IGF-I concentration (P < 0.05) from P108 toP136. Low IGF-I line ewes had lower (P < 0.001) plasma IGF-I than high IGF-I line ewes at each stage measured but higher plasma IGFBP-I at P89 and P108. Birth weights were higher in lambs born to low IGF-I line ewes than in those born to high IGF line ewes.These results suggest that the difference in birth weight between twin lambs from shorn and unshorn dams was mediated through a decline in maternal plasma IGF-I concentrations in late pregnancy. In support of previous studies, there was an inverse relationship between IGF-I selection line and lamb birth weight.

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The effect of mid-pregnancy shearing and litter size on lamb birth weight and postnatal plasma cortisol response

Cited by 13 publications

References 43 publications

Mid-pregnancy ewe shearing and the effects on fetus liver and muscle glycoprotein deposits

Mid-pregnancy ewe shearing and the effects on fetus liver and muscle glycoprotein deposits

The effect of different types of stressors during mid- and late pregnancy on lamb weight and body size at birth

Birth weight effect in twin‐born lambs from mid‐pregnancy shearing is associated with changes in maternal IGF‐I concentration

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