Increased Lamb Birth Weight Research Articles

Effects of prepartum shearing on metabolic and placental parameters of ewes: Impact on productive parameters of their lambs

Prepartum shearing has been associated with increased lamb survival under pastoral conditions. This research aimed to evaluate the effects of early and late prepartum shearing in gestating Corriedale ewes on the metabolic profile and placental parameters of the ewes and how these changes affect the productive parameters of their lambs. On day 70 of gestation, 37 ewes carrying a single foetus were randomly divided into three groups: ewes sheared at day 70 of gestation (early, PS70, n = 12), sheared at day 110 of gestation (late, PS110, n = 12), and ewes unsheared at prepartum (US, n = 13, control group). Energy metabolism (glycaemia, insulin, NEFA, and BHB) and placental parameters (placental weight, number, and characteristics of cotyledons, and placental efficiency) were evaluated in the ewes. Live weight, morphometric measurements, and body composition were determined in the lambs. Prepartum shearing performed on different days (early and late) caused changes in energy metabolism, leading to a decrease in serum insulin and an increase in NEFA and BHB blood values. Early prepartum shearing increased placental weight and the number and weight of the 2–3 cm-cotyledons, while late prepartum shearing increased placental weight and placental efficiency and only changed the weight of the 2–3 cm-cotyledons. Prepartum shearing on both days caused an increase in lamb birth weight. Therefore, prepartum shearing caused changes in the metabolic profile and placenta of the ewes, which resulted in increased weight and development of lambs at birth.

Evaluation of oral citrulline administration as a mitigation strategy for fescue toxicosis in sheep.

Gestating ewes consuming ergot alkaloids, from endophyte-infected (E+) tall fescue seed, suffer from intrauterine growth restriction and produce smaller lambs. Arginine (Arg) supplementation has been shown to increase birth weight and oral citrulline (Cit) administration is reported to increase arginine concentrations. Two experiments were conducted to: 1) evaluate if oral supplementation with Cit or water, to ewes consuming E+ fescue seed, increases lamb birth weight and 2) determine the effectiveness of Cit and citrulline:malate as an oral drench and elevating circulating levels of Cit to determine levels and dose frequency. In experiment 1, gestating Suffolk ewes (n = 10) were assigned to one of two treatments [oral drench of citrulline–malate 2:1 (CITM; 81 mg/kg/d of citrulline) or water (TOX)] to start on d 86 of gestation and continued until parturition. Ewes on CITM treatment had decreased (P < 0.05) plasma Arg and Cit concentrations during gestation. At birth, lambs from CITM ewes had reduced (P < 0.05) crude fat and total fat but did not differ (P > 0.05) in birth weight from lambs born to TOX ewes. In experiment 2, nonpregnant Suffolk ewes (n = 3) were assigned to either oral citrulline (CIT; 81 mg/kg/d), citrulline–malate 2:1 (CITM; 81 mg/kg/d of citrulline), or water (CON) drench in a Latin Square design for a treatment period of 4 d with a washout period of 3 d. On d 4, blood samples were collected at 0, 0.5, 1, 2, 3, 4, 6, 8, 10, 12, and 18 h post drench. Oral drenching of CIT and CITM increased (P < 0.0001) Cit concentrations within 2 h and levels remained elevated for 6 h. Apparent half-life of elimination for CIT and CITM were 8.484 and 10.392 h, respectively. Our results show that lamb birth weight was not altered with a single oral drench of citrulline–malate; however, lamb body composition was altered. The level and frequency of citrulline dosing may need to be greater in order to observe consistent elevation of Cit/Arg concentrations to determine its effectiveness in mitigating fescue toxicosis.

Supplementation of Underfed Twin-Bearing Ewes with Herbal Vitamins C and E: Impacts on Birth Weight, Postnatal Growth, and Pre-Weaning Survival of the Lambs.

Simple SummaryIn twin-bearing ewes, undernourishment during pregnancy lowers the birth weight and increases morbidity and mortality of lambs. One of the causes is oxidative stress, which can be prevented by supplementing antioxidant vitamins. In the present study we tested the effect of supplementation with herbal vitamins C and E alone or in combination with concentrate on pregnancy outcomes and growth and survival of lambs during early postnatal stages (lactation). The results showed that vitamin supplementation increased offspring birth weight and antioxidant capacity, with a trend towards higher body weight (BW) at weaning. Nutritional supplementation only had a positive effect on birth weight, meanwhile combined supplementation of vitamins and concentrate improves the lamb response. Lambs’ survival was not affected by the treatment, although absolute values of survival were higher in vitamin-treated groups. It is concluded that supplementation with herbal vitamins C and E alone or in combination with concentrate during pregnancy may constitute a good nutritional strategy to improve productivity in sheep herds reared in harsh environmental conditions.Twin-bearing pregnancies of sheep reared in harsh environmental conditions result in maternal undernutrition and feto-maternal oxidative stress, leading to intrauterine growth restriction (IUGR). We assessed the efficiency of supplementation with antioxidant herbal vitamins C and E alone or in combination with concentrate throughout gestation on pregnancy outcomes, pre-weaning growth, and survival of twin lambs from grazing ewes at the Magellan Steppe. Four groups (n = 30 each) of twin-bearing ewes received a base natural prairie (P) diet, supplemented with either herbal vitamins C 500 mg and E 350 IU per day (V) or concentrated food (S); groups were: P, P + V, P + S, and P + VS. Vitamins and concentrate were supplemented until parturition. At birth, lambs were weighed, and blood was drawn for total antioxidant capacity (TAC) evaluation. Lamb body weight (BW) and survival rate were evaluated at mid-lactation (60 days) and at weaning (120 days). Vitamin supplementation resulted in increased lamb birth weight and TAC, with a trend towards higher BW at weaning, while nutritional supplementation only had a positive effect on birth weight. Lamb survival was higher in both vitamin supplemented groups. In conclusion, supplementation with herbal vitamins C and E alone or in combination with concentrate food during pregnancy may constitute a good nutritional strategy for sheep reared in harsh environmental conditions.

Shearing during late pregnancy increases size at birth but does not alter placental endocrine responses in sheep

Shearing during the latter half of pregnancy is a common practice to improve flock health and productivity. Previous studies have demonstrated that shearing pregnant ewes at mid or late pregnancy is associated with an increase in lamb birth weight. In the present study, we used singleton Polypay × Dorset pregnant sheep, to investigate the potential roles of placental function and changes in maternal metabolism in underlying this increased birth weight response. Two groups were randomly established and blocked at enrollment by animal BW, body condition score and subcutaneous adipose tissue depth. The groups were shorn (SH; n = 18) or not (C; n = 20) at gestational day (GD) 107 ± 1 (mean ± SEM). Weekly maternal plasma samples were collected between shearing and birth, but only six samples were assayed for progesterone, pregnancy-associated glycoproteins (PAG1), glucose and non-esterified fatty acids (NEFAs). At birth, sex, birth weight, and newborn body mass index (BMI) were recorded. Maternal BW during mid- to late-pregnancy was similar between groups. Shearing resulted in increased lamb birth weight and BMI (P < 0.05) regardless of fetal sex but did not affect the maternal concentration of PAG1 or progesterone from GDs 100 to 142. After shearing (GD100) and up to lambing, shorn females had higher circulating glucose concentrations (P < 0.05), but not NEFA, compared to the control group. Maternal circulating PAG1, progesterone, glucose or NEFA concentration across pregnancy did not differ according to lamb sex. Across pregnancy, birth weight was positively associated with PAG1 (P < 0.001), but not with progesterone concentrations. In conclusion, weight and BMI at birth were higher in both sexes upon shearing in singleton pregnancies. Despite PAG1 being associated with birth weight, late-pregnancy shearing did not alter the placental endocrine response. Whether other placental factors are altered upon shearing and may influence the increase in birth weight and BMI remain to be investigated.

L-Arginine Modulates Maternal Hormonal Profiles and Neonatal Traits during Two Stages of Pregnancy in Sheep

A 2 × 2 factorial arrangement was designed to test effects of supplementation of a low (L, 75 mg/kg BW) vs. high (H, 150 mg/kg BW) L-arginine given at early (first 56 days) vs. late (last 56 days) pregnancy on maternal hormones and neonatal traits. Thirty Najdi pregnant ewes were randomly allocated into 6 groups. Ewes in G1 and G2 served as controls (C), given 50 ml saline at either early (CE) or late (CL) pregnancy, respectively. G3 and G4 ewes in early pregnancy received low (LE) and high L-arginine (HE), respectively. G5 and G6 ewes in late pregnancy received low (LL) and high (HL) L-arginine, respectively. A weekly blood sample was collected from initiation of the treatment till parturition. Serum growth hormone (GH), insulin-like growth factor-I (IGF-I), insulin, progesterone (P4) and estradiol 17 β (E2) profiles were determined. Neonatal traits were also determined. Insulin was higher (P 0.05). Lamb survival rates at birth in LE ewes were highest (100%) compared to other treatments. In conclusion, supplementing pregnant ewes with low dosage of L-arginine at early stage of gestation increased lamb birth weight and survival, and improved maternal health.

Grazing crops: implications for reproducing sheep

Integration of crops and livestock has been revitalised in Australia, initially as an opportunity to increase cropping within the high-rainfall grazing zones, and more recently, to improve enterprise diversification and profitability across the low-, medium- and high-rainfall, and mixed-farming zones. Young crops are highly digestible (&gt;80% dry matter digestibility, DMD) with a high energy density (&gt;12 MJ/kg DM) and, in much of southern Australia, fill a winter feed gap. The quality and time of feed availability also coincide with the high nutrient requirements of ewes in late pregnancy and lactation. In Western Australia and South Australia, young crops are available for lactating ewes and young growing lambs (autumn lambing). For the smaller proportion of growers who lamb later in winter, young crops are available for the last 1–2 months of pregnancy. In the later-lambing states of New South Wales and Victoria, crops may be grazed by ewes at any stage of pregnancy and lactation and/or by young lambs. In Tasmania, crops are more likely to be available during early–mid-gestation. Limited studies on feed budgeting with grazing crops have indicated that ewes can maintain or even increase liveweight, with a much lower level of feed on offer than would be required with traditional pastures (&lt;500 kg DM/ha). This has the potential to increase whole-farm stocking rates and/or reduce fetal mortality, increase lamb birthweight and survival and improve lifetime production. Maintaining or increasing ewe liveweight during pregnancy and lactation may also result in heavier ewes the following year and higher ovulation rates. Pregnancy and lactation are also periods of increased susceptibility to metabolic disturbances. The composition of young crops increases this susceptibility. Pregnancy toxaemia, hypocalcaemia and hypomagnesaemia can influence ewe health and fetal survival. Chronic acidosis and excessive ammonia absorption from rapid introduction of pregnant ewes onto young crops may risk appetite loss and increase susceptibility to pregnancy toxaemia. Low magnesium and sodium combined with high potassium increases the risk of grass tetany. Most young crops (except canola) also have a tetany index &gt;2.2, indicating a high risk of grass tetany. The elevated potassium also contributes to a high dietary cation–anion difference of approximately +49 mEq/100 g DM and this may cause metabolic alkalosis and hypocalcaemia. Pregnancy toxaemia, hypocalcaemia and grass tetany are all potential causes of increased ewe mortality. Pregnancy and/or lactation outcomes will also be influenced by a deficiency of trace elements. Grazing young crops in areas with a history of selenium, copper, iodine and cobalt deficiency will increase susceptibility to deficiency by increasing growth and feed intake. In conclusion, the grazing of young growing crops presents new opportunities for increased production and stocking rates in the mixed-farming zones. The value of this feed source is well recognised by some producers. While growing crops have a highly productive potential, they also come with an increased risk of a range metabolic disturbances and nutritional imbalances. These risks can be minimised by regular monitoring of livestock and crop biomass and the provision of mineral supplements.

FISH OIL SUPPLEMENTATION AND SELENIUM-VITAMIN E INJECTION OF EGYPTIAN EWES AND THEIR FINNISH LANDRACE CROSSBRED DURING LATE PREGNANCY: 2. LAMBS RESPONSE

Received at: 30/5/2013 Accepted: 19/6/2013 This work was designed to study the effects of fish oil supplementation and selenium-vitamin E (Sevit. E) injection of Egyptian ewes and their Finnish Landrace Crossbred during the late stage of pregnancy on lambs response. Neonatal behaviors and growth performance of lambs including birth weight and average daily gain were recorded, while immune status of lambs was determined. Fifty-one pregnant ewes [native breeds (Ossimi and Rahmani, n=30) and their crosses with exotic Finnish Landrace breed (n= 21)] were selected and allocated to 3 experimental groups (n= 17 animals per group). The first group was fed with fish oil supplemented diet for 6 weeks prior to lambing (40 gm Sardine oil /ewe/day); while the second group was injected by 2 successive doses of Sevit. E solution (5ml of 2mg sodium selinate and 100mg vitamin E) at 20 and 10 days before lambing. The third group was kept as a control. Lamb birth weight, neonatal behaviors, body temperature over the first 3d of life, average daily weight gain and mortality rates of lambs from birth until weaning were recorded. Blood samples were collected from each lamb, first sample was collected presuckling and the second one was at 24 h after birth for determination of phagocytic activity, white blood cell counts and serum total protein, including albumin and globulin. Lambs born to ewes of control group weighed less at birth and have an increased latencies to stand, reach the udder and suck successfully, and with a lower pre-suckling body temperature compared with those born to ewes supplemented with fish oil or others injected by selenium-vitamin E. These differences were more particularly observed in lambs born to native ewes than those born to crossbred ewes. Hematological analysis showed significantly higher white blood cell counts and phagocytic activity in lambs born to supplemented ewes than those born to control ones. No significant differences were demonstrated in pre-suckling concentrations of total serum protein, albumin and globulin between lambs born to treated ewes and those born to untreated ones. However, at 24h after birth, lambs born to supplemented ewes exhibited significantly higher concentrations of total protein and globulin than those born to control ewes. Moreover, lambs from supplemented ewes had significantly higher body weight gain with a minimal mortality rates from birth until weaning than those born to untreated ewes, specifically in ewes injected with selenium and vitamin E. We conclude that supplementing pregnant ewes with fish oil or selenium-vitamin E increases lamb birth weight, decreases the latency to stand and suckle and improves pre-suckling body temperature and immunocompetence of neonatal lambs with better lamb performance and survival.

Impact of wool stubble depth after mid pregnancy shearing on Corriedale ewe and lamb performance

The three experiments investigated the effects on physiology and production parameters of Corriedale ewes shorn in mid pregnancy, either using the cover or “R13” combs or leaving them unshorn. The experiments utilised both ewes and hoggets. In both experiments, the R13 comb left a greater stubble depth than the cover comb (P<0.05). The rectal post shearing temperature of ewes shorn either by the traditional cover or by R13 comb was lower than that of unshorn ewes (P<0.05), but between combs did not differ from each other (P>0.05). Shearing treatment had no effect on ewe live weight (P>0.05) and only a transitory (P<0.05) effect on ewe body condition score was observed on some occasions. In general, mid-pregnancy shearing increased lamb birth weight (P<0.05). In one out of three experiments, birth weight was increased by the R13 compared to the cover comb (P>0.05). Therefore, under the extensive grazing situations of Uruguay, shearing Corriedale ewes in mid-pregnancy, is a management tool that does not increase lamb birth weight and weaning weight consistently.

The effects of allowance and frequency of allocation of autumn-saved pasture, when offered to spring lambing ewes in mid pregnancy, on ewe and lamb performance and subsequent herbage yield

The effects of (i) frequency of herbage allocation and (ii) herbage allowance on ewe and subsequent lamb performance, when autumn-saved (extended grazed, deferred grazed) pasture is grazed (between 28 Nov and 30 Jan) by spring lambing ewes during mid gestation, were studied in Experiment 1. This involved 72 crossbred ewes from days 41 to 104 of gestation allocated to one of four treatments; two herbage dry matter (DM) allowances (1.0 and 1.8 kg per ewe) by two frequencies of herbage allocation (daily or twice weekly). From day 105 of gestation to parturition all ewes were housed and offered grass silage ( ad libitum) plus a total of 19 kg concentrate. Increasing herbage allowance improved ewe body condition score (P < 0.01) and live weight (P < 0.01) at the end of deferred grazing, and tended to increase herbage intake (P = 0.08) during deferred grazing. Reducing the frequency of herbage allocation increased lamb birth weight (P < 0.05). Otherwise frequency of herbage allocation did not alter (P > 0.05) forage intake or utilization, or ewe or subsequent lamb performance. In Experiment 2, the effects of herbage allowance (1.0 or 1.8 kg DM per ewe), frequency of allocation (daily, twice weekly) and grazing date (28 Nov. to 4 Dec., 12 to 18 Dec., 2 to 8 Jan. and 23 to 29 Jan.) during deferred grazing on herbage yield and composition at four subsequent harvest dates (4, 18 and 25 Apr., and 25 May) were evaluated in a split-plot design consisting of 128 plots. Delaying grazing date reduced herbage yield (P < 0.05) and the concentrations of neutral detergent fibre (NDF; P < 0.01) and acid detergent fibre (ADF; P < 0.01). Delaying harvest date increased herbage yield (P < 0.001) and reduced (P < 0.001) the concentrations of NDF, ADF and metabolisable energy. Increasing herbage allowance at grazing increased (P < 0.05) subsequent herbage yield. Frequency of herbage allocation during deferred grazing did not affect (P > 0.05) subsequent herbage yield. There was a significant interaction (P < 0.001) between grazing date and harvest date for herbage yield. It is concluded that to maximise stock carrying capacity and reduce labour requirement a herbage DM allowance of 1 kg per ewe per day, allocated twice weekly, is sufficient for ewes on deferred grazed pasture in mid pregnancy.

Sesbania sesban as a fodder tree in Ethiopian livestock farming systems : Feeding practices and farmers' perception of feeding effects on sheep performance

Sesbania sesban is one of the exotic multipurpose fodder trees introduced in the Ethiopian highlands for livestock feed and soil conservation. Several on-station studies showed that supplementation with Sesbania improved intake and digestibility of basal diet and growth rate of animals. However, information about farmers' feeding practices of Sesbania and farmers' perception of the effect of Sesbania feeding on animal performance is limited. The present study was conducted to assess farmers' feeding practices and their perception about effects of Sesbania supplementation on sheep performance in annual (one wheat-based (WheatCL) and one teff-based (TeffCL)) and perennial (coffee-based (CoffeeCL)) crop-based livestock systems in the Ethiopian Highlands. Data were collected from 98 households by interviews using a structured questionnaire. Farmers had on average 6.9 years of experience using Sesbania as a cut and carry supplementary feed. Farmers in the WheatCL and TeffCL fed Sesbania throughout the dry season while farmers in the CoffeeCL had no specific season for feeding Sesbania. Farmers in WheatCL and TeffCL offered significantly (P < 0.05) more frequently and a higher quantity per feeding of Sesbania than farmers in CoffeeCL. Most farmers perceived increased lamb birth weight and increased body weight gain, earlier onset of puberty, and improved pregnancy rate of ewes and rams' libido. Perceived improvement was significantly more (P < 0.05) in WheatCL and TeffCL than in CoffeeCL. We concluded that Sesbania was appreciated across farming systems for its feeding value. The marginal advantage of Sesbania was lowest in the CoffeeCL with relatively good availability of good quality feeds compared to the WheatCL and TeffCL, which explains the less positive perception of production and reproductive performance of Sesbania feeding in CoffeeCL.

Effects of antioxidant vitamins on newborn and placental traits in gestations at high altitude: comparative study in high and low altitude native sheep

The present study evaluated the hypothesis that the effects of hypoxia on sheep pregnancies at high altitude (HA) are mediated by oxidative stress and that antioxidant vitamins may prevent these effects. Both HA native and newcomer ewes were maintained at an altitude of 3,589 m during mating and pregnancy. Control low altitude (LA) native ewes were maintained at sea level. Half of each group received daily oral supplements of vitamins C (500 mg) and E (350 IU) during mating and gestation. Near term, maternal plasma vitamin levels and oxidative stress biomarkers were measured. At delivery, lambs were weighed and measured, and placentas were recovered for macroscopic and microscopic evaluation. Vitamin concentrations in supplemented ewes were two- or threefold greater than in non-supplemented ewes. Plasma carbonyls and malondialdehyde in non-supplemented ewes were consistent with a state of oxidative stress, which was prevented by vitamin supplementation. Vitamin supplementation increased lamb birthweight and cotyledon number in both HA native and newcomer ewes, although placental weight and cotyledon surface were diminished. Placentas from vitamin-supplemented HA ewes were similar to those from ewes at sea level, making these placental traits (weight, number and diameter of cotyledons) similar to those from ewes at sea level. Vitamin supplementation had no effect on LA pregnancies. In conclusion, supplementation with vitamins C and E during pregnancy at HA prevents oxidative stress, improving pregnancy outcomes.

Does offering concentrate supplement during late pregnancy affect twin- and triplet-bearing ewe and lamb performance?

This study investigated the effect of offering concentrate supplement during late pregnancy on twin- and triplet-bearing ewe and lamb performance. Twin- (n=40) and triplet-bearing (n=20) ewes were grazed on a 6 cm herbage height from day 70 of pregnancy until parturition. From pregnancy day 102, half of the ewes from each litter size were offered 400 g/ewe per day of concentrate sheep pellets. From day 102 until day 145 of pregnancy, ewes offered concentrate gained 60 g more liveweight per day than ewes offered pasture only (P<0.01). Ewes offered concentrate were also under less metabolic stress in late pregnancy, as indicated by lower (P<0.05) plasma beta-hydroxybutyrate (BOH) and non-esterified fatty acid (NEFA) concentrations. Offering concentrate increased lamb birth weight from 3.9 to 4.2 kg (P<0.05) and tended to increase lamb plasma gamma-glutamyl-transferase (GGT) concentrations at age 24–36 h (P = 0.08). It had no effect, however, on lamb plasma glucose or immuno-globulin G (IgG) concentrations within 24–36 h of age, lamb growth from birth until day 52 of lactation or lamb survival. Ewes offered concentrate reared a greater total weight of lamb to day 52 of lactation than ewes offered pasture only. The economic viability of offering a concentrate to these ewes grazing a 6 cm sward could not be established.

Communications orales - Séances plénières

Previous studies have shown that shearing pregnant ewes at mid- or late-pregnancy is associated with an increase in lamb birth weight. The present study was designed to investigate metabolic responses that may underlie this response. Single- and twin-bearing ewes were either unshorn or shorn at mid-pregnancy (Day 69 of pregnancy; P69), and insulin, glucose and epinephrine challenges were conducted on P109–111 and P132–134. Shearing increased the birth weight of twin lambs by over 1 kg (P < 0.001) without having any effect on singleton birth weight. This response was associated with a 10–20% reduction in the insulin response to a glucose challenge (P < 0.05) without a change in glucose clearance following either glucose or insulin challenges. The lipolytic response to epinephrine challenge increased as pregnancy progressed, but was not associated with the increased birth weight of twin lambs born to shorn ewes. By late pregnancy, a 25% reduction in maternal IGF-I concentration and a two- to threefold increase in maternal IGFBP-1 concentration (P < 0.05) associated with shearing were observed. The increase in lamb birth weight associated with mid-pregnancy shearing may have been associated with an increase in the non-insulin dependent uptake of glucose by the placental-fetal unit.

Ovelhas esquiladas e não esquiladas durante a gestação no Sul do Brasil: efeito na condição corporal e no peso ao nascer dos cordeiros

No presente trabalho, foi testado o efeito da esquila pré-parto na condição corporal (BCS), no peso de cordeiros ao nascer e no seu desenvolvimento. O grupo experimental foi constituído de 64 ovelhas com 3 anos, cruzas Border Leicester x Texel (49-54 kg), encarneiradas em março, foram divididas, aos 74 dias de gestação, em dois grupos de 32 cada. As ovelhas foram mantidas em campo nativo, 5 ovelhas/ha, com disponibilidade aproximada de 800 kg/ha. Aos 74 dias de gestação, um grupo foi esquilado (S) e o outro foi mantido não esquilado (US). A BCS dos dois grupos foi avaliada no início do experimento (P74), P108 e P135 dias de gestação e aos 15 e 24 dias da lactação. Foi também coletado o peso dos cordeiros ao nascer e a duas e três semanas da lactação. Observou-se uma redução na BCS média das ovelhas, de ambos os grupos, durante a gestação e lactação. O grupo S experimentou uma redução significativamente mais severa (P &lt; 0,05) na BCS. A BCS média desse grupo decresceu de 3,3 no dia P74 para 1,79 e 1,22 nos dias P135 e L24. No mesmo período, os valores da BCS média do grupo US foram de 3,11, 2,19 e 1,21. Ao nascer, o peso dos cordeiros, de ovelhas S foi 0,71 kg maior (P &lt; 0,05) do que o dos cordeiros de ovelhas do grupo US. Não houve diferença entre o ganho de peso dos cordeiros dos dois grupos medido a duas e três semanas de vida. O aumento no peso ao nascer dos cordeiros produzido pela esquila das ovelhas durante a gestação, descrito nesse trabalho, poderá reduzir a mortalidade perinatal de cordeiros, especialmente em anos com escassez de pastagem que pode resultar em uma BCS crítica durante a gestação. Os resultados sugerem também que atenção especial deverá ser dada a BCS das ovelhas durante a gestação, prática que não é comum no Sul do Brasil.

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

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 × 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 × 2, isolation × 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.

Effects of sire breed on ewe dystocia, lamb survival and weaned lamb output in hill sheep systems

A study was carried out on six hill farms, located in the main hill regions of Northern Ireland, over three breeding seasons to investigate the effect of sire breed on ewe dystocia, lamb survival and weaned lamb output. On each farm, groups of 26 to 40 purebred Scottish Blackface ewes (n = 3174) were crossed with Blackface, Swaledale, North Country Cheviot, Lleyn and Texel sires by natural service (year 1) and artificial insemination (years 2 and 3). Each of the mating groups was initially balanced for ewe age, live weight and condition score, and a total of 15 sires of each breed were used over the 3 years. In total, 2272 ewes were recorded at lambing, producing 3451 lambs, over the 3 years. Sire breed had a significant effect (P < 0.001) on lamb birth weight with Blackface and Swaledale the lowest and Texel the highest. The proportion of ewes with dystocia was higher with Texel sires compared with Lleyn, Swaledale and Blackface sires (P < 0.05). Ewes mated to Cheviot sires had more dystocia than those mated to Blackface and Swaledale sires (P < 0.05), while ewes mated to Lleyn sire breed had more dystocia (P < 0.05) than those mated to Blackface sire breed. Most of the incidence of dystocia was attributable to increased lamb birth weight (P < 0.001), and some to litter size (P < 0.05). Swaledale, Cheviot, Lleyn and Texel sire breeds increased the incidence of malpresentations (P < 0.05). Lamb live weight at weaning was higher with Texel- and Cheviot- and Lleyn-sired lambs compared with Blackface- and Swaledale-sired lambs (P < 0.01). The level of lamb mortality at birth was not affected by sire breed. However, lamb mortality at weaning was lower for Lleyn-sired lambs compared with the other lamb genotypes (P < 0.05). These results indicate that the use of sires from larger breeds, such as Lleyn and Texel, within the Blackface ewe flocks can increase lamb output, with no apparent detrimental effects on lamb mortality or ewe survival, but increased assistance at lambing will be required.

Effects of shearing at housing, grass silage feed value and extended grazing herbage allowance on ewe and subsequent lamb performance

The study involved 120 crossbred ewes (sixty 1.5 years old animals and sixty 2.5 years old animals; initial liveweight 67.6 kg, condition score 3.7), that were mated in October. They were assigned to six treatments (two shearing treatments (shorn and unshorn) × two silage feed values (low and medium) and two extended grazed herbage allowances (1.0 and 1.8 kg dry matter (DM)/day)) designed to evaluate the effects of shearing at housing, grass silage feed value and extended-grazed herbage allowance on their performance and the performance of their progeny. Swards, which had silage harvested on 6 September, received fertiliser N (34 kg/ha) for extended (deferred) grazing between 19 December and lambing in mid-March. The herbage was allocated at DM allowances of 1.0 or 1.8 kg/ewe daily until 1 February. For the final 6 weeks of pregnancy, daily herbage DM allowances were 1.5, 1.6, 2.0, 2.0 and 2.0 kg for weeks 6, 5, 4, 3 and 2 to parturition, respectively. Two grass silages (low and medium feed value) were offered from housing on 19 December to lambing in mid-March. At housing, half the ewes were shorn whilst the remainder remained unshorn. Each ewe received 23.4 kg concentrate prior to lambing. For the extended-grazed herbage and the low and medium feed-value silages, DM concentrations were 132, 225 and 265 g/kg, and metabolisable energy (ME) concentrations were 10.0, 10.0 and 10.7 MJ/kg DM, respectively. Treatment did not alter (P > 0.05) litter size or number reared. Grass silage feed value did not significantly alter silage DM intake, or ewe and subsequent lamb performance. Increasing herbage allowance in mid-pregnancy decreased herbage utilisation (P < 0.05) and increased herbage intake (P < 0.05). Shearing increased silage intake (P < 0.05), lamb birth weight (P < 0.01) and tended to increase lamb weaning weight (P = 0.07). Relative to the housed shorn ewes, extended grazing did not alter (P > 0.05) ewe or subsequent lamb performance. It is concluded that shearing ewes at housing increased lamb birth weight due to increased silage intake probably associated with cold stress immediately post shearing and reduced heat stress in late pregnancy. Based on differences in lamb weight at weaning 0.8 kg of grass silage DM intake had the same feed value as a daily extended herbage DM allowance of 1.8 kg per ewe throughout the study. Neither silage feed value nor herbage allowance in mid-pregnancy affected lamb birth weight or subsequent growth rate.

Effect of Injecting with Dexamethasone and Progestagen-PMSG on Reproduction and Rearing of Lambs in Semi-Intensive Conditions

The aim of the present study was to evaluate the effect of different doses dexamethasone and progestagen-PMSG on fertility and prolificacy in Kivircik ewes during the breeding season. For the experiment, 100 ewes were divided into four groups, with 25 females in each group. Groups were fluorgestone acetate (FGA, 30 mg), administered via intravaginal sponges. Experimental groups 2, 3 and 4 mL dexamethasone injection were given 72 h before mating season. The fertility rates control, 2, 3 and 4 mL were 88.0, 92.0, 100.0 and 100.0%, respectively (p<0.05). The prolificacy rates for the same groups were 122.7, 130.4, 144.0 and 156.0%, respectively (p<0.01). The injections dexamethasone significantly increased lamb birth weight and daily weight gain for 60 days (p<0.05).

Effects of nutritional level during late pregnancy on colostral production and blood immunoglobulin levels of Karakul ewes and their lambs

An experiment was conducted to examine the changes in colostral production and composition in Karakul ewes fed at different nutritional levels. Pregnant ewes were randomly allotted to one of four groups ( n = 20 per group) 90 days after artificial insemination. Three groups were fed with total mixed rations supplying 90, 100 and 110% of the NRC requirements, respectively, and the last group served as the control feeding on natural vegetations until parturition. Blood samples were taken from the jugular vein during late pregnancy, and soon after lambing. Fifteen singleton ewes from each group were hand-milked completely at 1, 12 and 24 h post-lambing. Samples of colostrum were obtained and the lambs were fed with their ewe's colostrum (30 g/kg BW) at each milking. Blood samples were taken from the lambs before receiving their first colostrum, and again at 24 and 48 h post-lambing. Ewes on 110% NRC diet produced significantly ( P < 0.01) more colostrum than did the ewes in other groups. Feeding level did not have a significant effect on the IgG level of the colostrums and blood sera of ewes and lambs. Mean IgG concentration in the ewe serum was greatest during late gestation (1–2 months before lambing) and were significantly reduced at 1 h post-lambing. Non-immunoglobulin composition of colostrum was not significantly affected by the treatment. There was a significant correlation between IgG levels of the ewe serum and colostrum ( r = 0.64, P < 0.0001). Mean weight of the ewes on the control ration at lambing and the mean birth weight of their lambs were significantly lower as compared with other dietary groups. The results suggested that hand-feeding of Karakul ewes on poor rangeland vegetation with 110% NRC for 2 months before parturition increased colostral production, decreased the ewe loss and increased lamb birth weight which is beneficial to lamb survival.

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

The study was conducted to determine the effect of mid-pregnancy shearing on lamb birth weight, body dimensions and postnatal plasma cortisol response to a stressor. Fetal exposure to excess maternal glucocorticoids at specific stages of pregnancy may influence postnatal function of the hypothalamic-pituitary-adrenal (HPA) axis. This in turn may have implications on the growth, development and survival of lambs. Romney ewes of various ages, bearing singletons ( n = 47) or twins ( n = 48) were shorn or not (control) on day 80 of pregnancy. Ewes were managed as a single flock throughout pregnancy under general commercial farming conditions. Within 12 h of birth the lamb's live weight and body dimensions were recorded. On day 39 of lactation the plasma cortisol levels of the ram lambs in response to handling or castration was assessed. A random sample of ram lambs born to the control (6 singleton and 9 twins) or shorn (7 singleton and 11 twins) ewes were allocated to either a handling or castration treatment. Singleton and twin lambs born to shorn ewes were 7% heavier at birth than their counterparts. Lambs born to ewes shorn in mid-pregnancy recorded longer ( P < 0.05) crown rump (53.1 cm versus 51.7 cm) and forelimb (30.8 cm versus 30.0 cm) measurements than the counterparts born to control ewes, respectively. However, when the lamb's live weight was considered in the model these differences were not significant. Mid-pregnancy shearing had no effect on the cortisol response of singleton or twin-born ram lambs to handling or castration. The postnatal plasma cortisol response of twin lambs was higher ( P < 0.05) than that of singletons (30.8 mmol l −1 min versus 14.4 mmol l −1 min), regardless of the treatment. Mid-pregnancy shearing resulted in increased lamb live weights and body dimensions in both singleton and twin lambs at birth—while plasma cortisol response of lambs to handling or castration was unaffected. These data suggest that mid-pregnancy shearing had little effect on HPA axis development in singleton or twin offspring and the increase in lamb birth weight caused by mid-pregnancy shearing did not result in altered postnatal HPA function.