Birth Weight In Sheep Research Articles

Qualitative traits and their effects on litter size and birth weight in sheep in the Sudano-Sahelian zone of Cameroon

Qualitative traits and their effects on litter size and birth weight in sheep in the Sudano-Sahelian zone of Cameroon

Placental MRI Predicts Fetal Oxygenation and Growth Rates in Sheep and Human Pregnancy.

Magnetic resonance imaging (MRI) assessment of fetal blood oxygen saturation (SO2) can transform the clinical management of high‐risk pregnancies affected by fetal growth restriction (FGR). Here, a novel MRI method assesses the feasibility of identifying normally grown and FGR fetuses in sheep and is then applied to humans. MRI scans are performed in pregnant ewes at 110 and 140 days (term = 150d) gestation and in pregnant women at 28+3 ± 2+5 weeks to measure feto‐placental SO2. Birth weight is collected and, in sheep, fetal blood SO2 is measured with a blood gas analyzer (BGA). Fetal arterial SO2 measured by BGA predicts fetal birth weight in sheep and distinguishes between fetuses that are normally grown, small for gestational age, and FGR. MRI feto‐placental SO2 in late gestation is related to fetal blood SO2 measured by BGA and body weight. In sheep, MRI feto‐placental SO2 in mid‐gestation is related to fetal SO2 later in gestation. MRI feto‐placental SO2 distinguishes between normally grown and FGR fetuses, as well as distinguishing FGR fetuses with and without normal Doppler in humans. Thus, a multi‐compartment placental MRI model detects low placental SO2 and distinguishes between small hypoxemic fetuses and normally grown fetuses.

Variation in the Ovine Glycogen Synthase Kinase 3 Beta-Interaction Protein Gene (GSKIP) Affects Carcass and Growth Traits in Romney Sheep.

Simple SummaryThe glycogen synthase kinase 3 beta (GSK3β)-interacting protein plays a role in regulating glycogen metabolism, protein synthesis, the cell cycle, and in regulating gene expression. To date, physiological function research into the GSK3β-interacting protein has been focused on cell lines, gene ‘knockout’ models, and over-expression studies, and to our knowledge, there have been no reports on how variation in the GSK3β-interacting protein gene (GSKIP) may affect phenotypic traits. In this study, PCR-SSCP methods were used to screen for variation in exon 1 and exon 2 of GSKIP in 840 New Zealand (NZ) Romney sheep. Two variant sequences were identified in exon 1 and this variation in GSKIP was associated with variation in lamb birth weight, hot carcass weight, and fat depth at the 12th rib.The glycogen synthase kinase 3 beta (GSK3β)-interacting protein (encoded by the gene GSKIP) is a small A-kinase anchoring protein, which complexes with GSK3βand protein kinase A (PKA) and acts synergistically with cAMP/PKA signaling to inhibit GSK3β activity. The protein plays a role in regulating glycogen metabolism, protein synthesis, the cell cycle, and in regulating gene expression. In this study, PCR-single strand conformation polymorphism (PCR-SSCP) analyses were used to screen for variation in exon 1 and exon 2 of GSKIP in 840 New Zealand (NZ) Romney sheep. Two SSCP banding patterns representing two different nucleotide variants (A and B) were detected in an exon 1 region, whereas in an exon 2 region only one pattern was detected. Variants A and B of exon 1 had one non-synonymous nucleotide difference c.37A/G (p.Met13Val). The birthweight of sheep of genotype AA (5.9 ± 0.06 kg) was different (p = 0.023) to sheep of genotype AB (5.7 ± 0.06 kg) and BB (5.7 ± 0.06 kg). The hot carcass weight (HCW) of sheep of genotype AA (17.2 ± 0.22 kg) was different (p = 0.012) to sheep of genotype AB (17.6 ± 0.22 kg) and BB (18.0 ± 0.29 kg), and the fat depth at the 12th rib (V-GR) of sheep of genotype AA (7.7 ± 0.31 mm) was different (p = 0.016) to sheep of genotype AB (8.3 ± 0.30 mm) and BB (8.5 ± 0.39 mm). The results suggest that the c.37A/G substitution in ovine GSKIP may affect sheep growth and carcass traits.

Genome-wide association study of birth weight in sheep

Birth weight is the earliest available growth trait with considerable impacts on lamb survivability and growth performance traits. This study was conducted to perform a genome-wide association study of birth weight in a meat-type sheep. A total of 132 Lori-Bakhtiari sheep were selected based on estimated of breeding values (EBVs) for BW analyses. The selected animals were genotyped using Illumina Ovine SNP50 Bead Chip. After quality control, a total of 41 323 single-nucleotide polymorphisms (SNPs) and 130 sheep were used for subsequent analyses. Plink 1.90 beta software was used for the analyses. Seven SNPs on chromosomes 1, 16, 19 and 22 were detected based on genome-wide unadjusted P-values (P <10−6), which jointly accounted for 1.2% of total genetic variation. However, based on Bonferroni-adjusted P-values, only three SNPs on chromosome 1 had significant associations with EBVs for birth weight (P <0.05), which jointly explained 0.8% of total genetic variation. A total of seven genes were found in 50 kb intervals from the three significant SNPs on chromosome 1, but only three genes, including RAB6B (a member of RAS oncogene family), Tf serotransferrin and GIGYF2 (a GRB10 interacting GYF protein 2), could be considered as candidate genes for birth weight in future studies. The results of this study may facilitate potential use of the genes involving in growth and production traits for genetic improvement of productivity in sheep.

1137 Effects of parity and mid-gestation nutrient restriction on umbilical blood flow, fetal and placental measurements, and birth weight in sheep

1137 Effects of parity and mid-gestation nutrient restriction on umbilical blood flow, fetal and placental measurements, and birth weight in sheep

4E-4 Climate affects birth weight in sheep

4E-4 Climate affects birth weight in sheep

Identifying when weather influences life‐history traits of grazing herbivores

1. There is increasing evidence that density-independent weather effects influence life-history traits and hence the dynamics of populations of animals. Here, we present a novel statistical approach to estimate when such influences are strongest. The method is demonstrated by analyses investigating the timing of the influence of weather on the birth weight of sheep and deer. 2. The statistical technique allowed for the pattern of temporal correlation in the weather data enabling the effects of weather in many fine-scale time intervals to be investigated simultaneously. Thus, while previous studies have typically considered weather averaged across a single broad time interval during pregnancy, our approach enabled examination simultaneously of the relationships with weekly and fortnightly averages throughout the whole of pregnancy. 3. We detected a positive effect of temperature on the birth weight of deer, which is strongest in late pregnancy (mid-March to mid-April), and a negative effect of rainfall on the birthweight of sheep, which is strongest during mid-pregnancy (late January to early February). The possible mechanisms underlying these weather-birth weight relationships are discussed. 4. This study enhances our insight into the pattern of the timing of influence of weather on early development. The method is of much more general application and could provide valuable insights in other areas of ecology in which sequences of intercorrelated explanatory variables have been collected in space or in time.

Factors affecting birth weight in sheep: maternal environment

Knowledge of factors affecting variation in birth weight is especially important given the relationship of birth weight to neonatal and adult health. The present study utilises two large contemporary datasets in sheep of differing breeds to explore factors that influence weight at term. For dataset one (Study 1; n=154 Blue-faced Leicester x Swaledale (Mule) and 87 Welsh Mountain ewes, 315 separate cases of birth weight), lamb birth weight as the outcome measure was related to maternal characteristics and individual energy intake of the ewe during specified periods of gestation, i.e. early (1-30 days; term ~147 days gestation), mid (31-80 days) or late (110-147 days) pregnancy. For dataset two (Study 2; n=856 Mule ewes and 5821 cases of birth weight), we investigated using multilevel modelling the influence of ewe weight, parity, barrenness, lamb sex, litter size, lamb mortality and year of birth on lamb birth weight. For a subset of these ewes (n=283), the effect of the ewes' own birth weight was also examined. Interactions between combinations of variables were selectively investigated. Litter size, as expected, had the single greatest influence on birth weight with other significant effects being year of birth, maternal birth weight, maternal nutrition, sex of the lamb, ewe barrenness and maternal body composition at mating. The results of the present study have practical implications not only for sheep husbandry but also for the increased knowledge of factors that significantly influence variation in birth weight; as birth weight itself has become a significant predictor of later health outcomes.

Embryo viability, duration of gestation and birth weight in sheep after transfer of in vitro matured and in vitro fertilized zygotes cultured in vitro or in vivo.

The influence of various in vitro procedures on embryo survival and the production of normal offspring was investigated in sheep. Zygotes produced from in vitro matured (IVM) and fertilized (IVF) oocytes derived from slaughtered Merino ewes were allocated to three culture treatments for 6.5 days. Two groups were cultured in vitro in the absence or presence of oviduct epithelial cells while the third group was cultured in vivo in the oviducts of synchronized ewes. A fourth group of zygotes obtained from superovulated Merino ewes was also cultured in vivo and served as controls. After culture, IVM-IVF morulae and blastocysts, and control embryos were transferred to final recipient ewes. Pregnancy was diagnosed at day 50 of gestation by ultrasonography and pregnancies were allowed to go to term. The survival to term of IVM-IVF zygotes cultured in vitro was reduced compared with both in vivo cultured IVM-IVF zygotes and control zygotes (25-35% versus 51-60%, respectively, P < 0.05). Day 6.5 IVM-IVF morulae had a lower survival rate than did control morulae regardless of culture treatment (P < 0.05), while survival rates of day 6.5 IVM-IVF blastocysts cultured in vivo did not differ from those of control blastocysts (P > 0.1). Both the gestation period and birth weight of IVM-IVF lambs were increased when compared with controls, the former significantly in all groups (154.0-154.9 days versus 150.6 days; P < 0.01), while the latter increase was on the borderline of significance (4.5-4.8 kg versus 4.0 kg; 0.01 < or = P < or = 0.1, respectively) and dependent on the prolongation of the gestation period. It is concluded that in vitro maturation and fertilization compromise subsequent embryonic and fetal development in sheep irrespective of the subsequent in vivo or in vitro culture treatment. Subjecting IVM-IVF zygotes to in vivo culture for 6.5 days minimizes only some of these effects, thus leading to the aberrant production of some offspring.

Seasonal effects on birth weight in sheep are associated with changes in placental development

Abstract Lambs born in the autumn or winter have substantially lower birth weights than those born in the spring, but the physiological basis of this difference is unknown. This study examined the effects of season on foetal growth and placental development in ewes managed under controlled grazing to minimise the confounding effects of maternal liveweight change. Mature Romney ewes pregnant to matings in December (n = 13) or March (n ‐ 13), with similar liveweights at mating, were managed to achieve similar liveweights at Day 140 of gestation. At that time, measures of foetal growth and placental development, adjusted for litter size, were (December‐ versus March‐mated): foetal weight (4.15 ± 0.16 versus 5.07 ± 0.16 kg, P 0.10); placentome number (89.4 ± 4.2 versus 106.9 ± 4.3, P < 0.01); number of placentomes per number of caruncles (0.79 + 0.03 versus 0.88 ± 0.03, P < ...

Lamb birthweight in sheep differently acclimatized to a hot environment

Two groups of ewes were selected from a flock of 151 ewes in the semi-arid tropics of northern Australia, according to their rectal temperature measured at 1600 hours on each of 3 consecutive days when maximum daily ambient temperature was 36� 0.5�C. Low temperature status (LRT) ewes had a rectal temperature of &lt;39.8�C at 1600 hours on each of the 3 days, while high temperature status (HRT) ewes had a rectal temperature of &gt;39.9�C. These ewes were mated 8 months later and exposed to a summer gestation under normal grazing conditions. Maximum and minimum daily ambient temperatures during pregnancy were 37�0.3�C and 21�0.3�C respectively. Rectal temperature measured at both 0800 and 1600 hours for HRT ewes was higher (P &lt; 0.01) than for LRT ewes during pregnancy. LRT ewes produced lambs of higher (P &lt; 0.05) birthweight and ponderal index than HRT ewes. The physiological basis for the difference in fetal growth in ewes which respond differently to a hot climate has not been identified, but possible mechanisms are discussed.

128: Observations on experimental intrauterine growth retardation in sheep

Low birthweight in sheep is associated with increased perinatal mortality. The sheep uterus contains folds of endometrium (caruncles) which form the maternal cotyledon in pregnancy. Alexander (1964) removed caruncles & in a subsequent pregnancy observed a reduction of placental & fetal weight, increased incidence of premature labour & stillbirths. 4 small fetuses have been produced using this technique. Catheters were implanted into the ewe & the fetus between 105 & 110 d. Serial measurements of blood gases, pH, metabolites, cortisol & ACTH were made. The mean fetal carotid PaO2 & haematocrit were 15.9 ± 1.3 mm Hg & 37.4 ± 2.2% compared to 21.6 ± 1.0 mm Hg & 30.3 ± 0.6% in 7 control fetuses (P < 0.01). There were no significant changes in PaCO2 or pH. Plasma glucose (0.66 ± 0.03 μmol/ml), lactate (0.9 ± 0.02 μmol/ml) and a amino nitrogen (aNH2, 6.11 ± 0.25 μmol/ml) were lower than in control fetuses (glucose 1.19 ± 0.02 μmol/ml, lactate 1.47 ± 0.02 μmol/ml and a NH2 7.64 ± 0.02 μmol/ml)suggesting a limitation of placental transfer. We have previously observed increased ACTH with hypoxaemia or hypoglycaemia. However, the concentration of ACTH (69.2 ± 29.7 pg/ml) and cortisol (21 ± 8.2 ng/ml) in the small fetuses was not significantly different from controls.

Variation in Fleece Weight, Weaning Weight and Birth Weight of Sheep under Farm Conditions1

Variation in Fleece Weight, Weaning Weight and Birth Weight of Sheep under Farm Conditions1