Twin-bearing Ewes Research Articles

SOME INDICES OF METABOLIC PROFILE AND OXIDATIVE STRESS IN SOHAGI EWES DURING TRANSITION PERIOD

The present study was carried out to assess some metabolic indices and nitric oxide in sexually mature, cycling; apparently healthy Sohagi ewes during transition period. At the beginning of the study, 40 ewes were randomly separated into two main groups: pregnant (n = 25) and non pregnant (n = 15) groups. Pregnant group was further subdivided retrospectively into single and twin bearing ewes’ subgroups. Blood samples were collected from both main groups. Samples from pregnant ewes were collected at two weeks before and after parturition. Samples were assayed for serum total protein, glucose, urea nitrogen, creatinine, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and nitric oxide. The results of this study showed no marked change in serum metabolites in single-bearing transition Sohagi ewes except for nitric oxide level. On the other hand, significantly lower (p < 0.05) levels of serum total protein and glucose concentrations were recorded in twin-bearing ewes while liver enzymes and serum urea nitrogen showed significant higher (p < 0.05) compared to control group. Marked improvement in serum metabolites had been recorded after parturition. Only level of nitric oxide production showed significant increase in both single and twin-bearing ewes before parturition compared to control one. While this study indicates the susceptibility of full-term twin-bearing pregnant Sohagi ewes to negative energy balance and oxidative stress before parturition, it showed tolerance of single-bearing pregnant ewes to energy disturbance. Additionally, twin-bearing pregnant Sohagi ewes showed high degree of metabolic adaptation as indicated by remarkable improvement in the blood glucose level shortly after parturition.

Effect of twin-bearing ewe body condition score and late pregnancy nutrition on lamb performance

This study aimed to investigate the effects of ewe body condition score and nutrition on twin-bearing ewes and their offspring. At maximum Day 112 of pregnancy (range 96–112 days), 185 twin-bearing ewes were allocated to either a ‘Medium’ or ‘ad libitum’ (Adlib) feeding treatment for the following 25 days (P112–P136). Each feeding treatment included ewes of body condition score: 2.0 (CS2.0, Medium n = 32, Adlib n = 28), CS2.5 (Medium n = 31, Adlib n = 33) or CS3.0 (Medium n = 30, Adlib n = 31). After P136 ewes were offered Adlib feeding conditions. Medium treatment ewes were lighter (P &lt; 0.05) than Adlib ewes at P136 and P142 and displayed lower (P &lt; 0.05) body condition score at P136 and back-fat depths at P142. CS2.0 ewes had lower (P &lt; 0.05) liveweights and body condition score at P112, P136 and P142 than CS2.5 ewes, which in turn had lower (P &lt; 0.05) liveweight and body condition scores than CS3.0 ewes. Ewe feeding treatment had no effect (P &gt; 0.05) on lamb liveweight or apparent colostrum intake. Ewe body condition score had no effect (P &gt; 0.05) on lamb birthweight or apparent colostrum intake. Lambs born to CS2.0 ewes had greater (P &lt; 0.05) survival than lambs born to CS2.5 ewes. At the end of the study lambs born to CS2.0 ewes were lighter (P &lt; 0.05) than those born to CS2.5 and CS3.0 ewes although, there was (P &gt; 0.05) no effect of condition score on total litter liveweight. In conclusion, these results suggest twin-bearing ewes of body condition 2.0–3.0 can be offered restricted feeding levels to at least Day 136 of pregnancy with few implications for their lambs.

Ewe nutrition in early and mid- to late pregnancy has few effects on fetal development

Maternal nutrition affects fetal development, with potential lifelong consequences. The study reported here compared the anatomical development (dimensions and organs) of twin fetuses at Day 140 of gestation, from 58 twin-bearing ewes fed at one of three different nutritional treatments in early pregnancy [Day 21–50, Low (LD21–50) versus Medium (MD21–50) versus High (HD21–50)] and one of two different nutritional treatments in mid- to late pregnancy (Day 50–140, Medium (MD50–140) versus High (HD50–140)]. There were no effects (P &gt; 0.05) of either early or mid- to late pregnancy nutrition on placental weight and fetal bodyweight or size measurements at Day 140. Semitendinosus muscles from LD21–50-HD50–140 fetuses were heavier (P &lt; 0.05) than those from LD21–50-MD50–140 and HD21–50-HD50–140 fetuses, and fetuses from LD21–50 dams had lighter (P &lt; 0.05) mammary glands compared with those from MD21–50 and HD21–50 dams, even after adjustment for fetal weight. Maternal nutrition also affected (P &lt; 0.05) the weights of the fetal thyroid and brain. These results suggest that farmers can limit ewe nutrition in early pregnancy with only minor effects on the fetus. To investigate potential lifetime effects, a larger cohort of these animals is currently being monitored.

Caloric restriction, but not caloric loading, affects circulating fetal and maternal C-type natriuretic peptide concentrations in late ovine gestation

The factors regulating the greatly elevated concentrations of maternal plasma C-type natriuretic peptide (CNP) forms in ruminant pregnancy are largely unknown, but nutrient status is likely to be important. Previous work has shown that increases in maternal plasma CNP, sourced from the placenta, occur in response to caloric restriction in late gestation. Whether oversupply of nutrients also regulates CNP secretion in pregnancy has not been studied. Hypothesising that CNP in fetal and maternal tissues will be responsive to both deficiency and excess, we studied changes in CNP and a cosecreted fragment, namely N-terminal pro-CNP (NTproCNP), during short-term periods of caloric restriction (CR) and loading (CL). Twin-bearing ewes received CR (fasted Days 121-124), CL (Days 110-124) or control maintenance diets. During CR, fetal plasma CNP forms, insulin-like growth factor (IGF)-1 and liveweight all fell, and maternal plasma NTproCNP increased. During CL, fetal IGF-1 increased, whereas CNP forms and liveweight were unchanged, as were maternal concentrations of CNP forms. The high abundance of CNP peptides in placental tissues was unaffected by these short-term changes in nutrient supply. We conclude that CNP in the fetal-maternal unit is acutely responsive to undernutrition, but is unaffected by oversupply in late gestation.

Effects of Level of Feeding During Early to Mid-Pregnancy on Placental and Fetal Development in the Sheep

Objective: This study was designed to determine the effect of maternal undernutrition during early to mid-pregnancy (i.e. 28 &ndash; 80 days gestation; term &asymp; 147 days) on placental and fatal development in the sheep. Materials and Methods: Singleton and twin- bearing ewes were malnourished between 28 to 80 days of pregnancy and its effects on both placental and fatal components determined. Malnourished ewes were fed 3.2 - 3.8 MJ day-1 of metabolisable energy (ME) (~ 60% of ME requirements). Diet comprised of chopped hay and barley-based concentrates. Results: Maternal malnourishment had no effect on total placental weight, but caused a significant increase (P&lt;0.05) in the weight of the fetal placenta of the uterine horn occupied by the fetus in singleton bearing ewes. Fetal development in singletons was not affected, but limb length was significantly reduced (P&lt;0.05). Total placental weight and fetal placental weight were significantly reduced (P&lt;0.05) in the twin-bearing ewes. Undernutrition caused a reduction (P&lt;0.05) in fetal weight in the twins. Maternal malnourishment had no effect on cell development in the maternal placenta of the twin-bearing ewes, but blood supply to the maternal placenta was stimulated. In contrast to the maternal placenta, undernutrition did not only cause a reduction (P&lt;0.05) in cell number in the fetal placenta, but also a reduction (P&lt;0.05) in the supply of blood. Undernutrition had no effect on cell size or blood supply to the maternal liver. Conclusion: These findings demonstrate the differential effects of maternal malnourishment on placental and fetal development in singleton and twin-bearing ewes.Key words: Feeding level, Early to mid pregnancy, placenta, fetal development, ewe

Olfactory Cue Mediated Neonatal Recognition in Sheep, Ovis aries

The strong bond between ewe and lamb formed shortly after parturition is an important factor in lamb survival. Evidence exists that a ewe can distinguish her lamb by its unique smell, but the constituents of such a putative olfactory cue have not yet been identified. We have now identified 133 volatile organic compounds associated with the wool of Döhne Merino lambs that we presume may be involved in neonatal recognition. Quantitative analysis and comparison of odor profiles of the twins of 16 ewes (9.69% sample group) of a flock of 165 twin-bearing ewes revealed that the wool volatiles of twins are qualitatively and quantitatively similar, but differ from those of other twins or non-twin lambs in the flock. The 88 constituents present in at least 20% of the analyzed wool samples were considered as variables for multivariate analysis. A P-value < 0.001 was calculated, indicating that the pairing of twins according to the qualitative and quantitative composition of the wool was significant. Bioassays carried out during the lambing seasons of 2009 and 2010 confirmed the previously established role of lamb odor in ewe-lamb recognition. However, when alien lambs were dressed in jackets sprayed with synthetic mixtures formulated to match the chemical composition of the effluvia of the ewes' own lambs, ewes rejected the aliens. This is possibly because the VOCs were not released in quantitative ratios sufficiently accurate to emulate the odor of the ewes' own lambs.

Do ewe size and nutrition during pregnancy affect foetus and foetal organ weight in twins?

This study set out to investigate the effects of ewe size and nutrition during pregnancy on the development of twin-foetuses and was part of a large study investigating life-time effect of maternal size and nutrition on the offspring. Heavy (H) and light (L) Romney ewes were allocated to ad libitum (A) or maintenance (M) nutritional regimens from day 21 to day 140 of pregnancy (P21–P140). At P65, P100 and P140, five (total of 59 ewes) twin-bearing ewes from each size-by-nutritional-treatment group were euthanized and foetal organs were collected and weighed. L-ewes were lighter and had greater changes in live weight from breeding to P65, P100 and P140 than H-ewes. M-ewes were lighter and had smaller changes in live weight than A-ewes from breeding to P65, P100 and P140. No ewe-size or nutritional effects were found on organ weights measured at P65. At P100, ewe size and nutritional level had no effect on foetal weight. Foetuses from M-ewes had 7% heavier livers after correcting for foetal weight, compared to those from A-ewes at P100. At P140, foetuses from L- and M-ewes were lighter than foetuses from H- and A-ewes. In addition, foetuses from M-ewes had lighter thyroid glands (34%) but heavier livers (14%) and kidneys (11%) than foetuses from A-ewes after correction for foetal weight. In conclusion, ewe size constrained twin foetuses in late gestation, but not in early or mid gestation. Similarly, maternal nutrition had only few effects on foetal development in early- and mid-pregnancy, however, foetal development was more affected in late gestation, suggesting that the twin-foetuses were nutrient deprived in this late period only.

Effect of intra-amniotic lipopolysaccharide on nephron number in preterm fetal sheep

Chorioamnionitis is an antecedent of preterm birth. We aimed to determine the effect of experimental chorioamnionitis in fetal sheep during late gestation on 1) nephron number, 2) renal corpuscle volume, and 3) renal inflammation. We hypothesized that exposure to chorioamnionitis would lead to inflammation in fetal kidneys and adversely impact on the development of nephrons, leading to a reduction in nephron number. At ∼121 days of gestation (term ∼147 days), pregnant ewes bearing twin or singleton fetuses received a single intra-amniotic injection of lipopolysaccharide (n = 6; 3 singletons, 3 twins); controls were either untreated or received an intra-amniotic injection of saline (n = 8; 4 singletons, 4 twins). One twin was used from each twin-bearing ewe. At ∼128 days of gestation, fetuses were delivered via Caesarean section. Kidneys were collected and stereologically analyzed to determine nephron number and renal corpuscle volume. Renal inflammation was assessed using immunohistochemistry. Experimental chorioamnionitis did not affect body weight or relative kidney weight. There was a significant reduction in nephron number but no change in renal corpuscle volume in LPS-exposed fetuses relative to controls. On average, nephron number was significantly reduced by 23 and 18% in singleton and twin LPS-exposed fetuses, respectively. The degree of renal inflammation did not differ between groups. Importantly, this study demonstrates that exposure to experimental chorioamnionitis adversely impacts on nephron number in the developing fetus.

Effects of twin-bearing ewe nutritional treatments on ewe and lamb performance to weaning

Nutrition of the ewe at various stages of pregnancy is known to affect ewe and offspring performance. However, little is known regarding the potential interactions among differing maternal nutrition regimens in early and mid–late pregnancy. The objective of the present study was to examine the effects and potential interactions of three pastoral nutritional treatments from Day 21 of pregnancy (P21) to P50 (Sub-maintenanceP21–50 (total liveweight change achieved, SMP21-50, –0.15 ± 0.02 kg/day) v. MaintenanceP21–50 (MP21-50,–0.02 ± 0.02 kg/day) v. Ad libitumP21–50 (AdP21-50,0.15 ± 0.02 kg/day) and two pastoral nutritional treatments from P50 to P139 [MaintenanceP50–139 (designed to match change in conceptus mass, total liveweight change achieved, 0.19 ± 0.01 kg/day) v. Ad libitumP50–139 (0.26 ± 0.01 kg/day)] on 382 twin-bearing ewes and their offspring until 91 days after the mid-point of lambing (L91). Ewe liveweight and condition scores in pregnancy and lactation, and lamb liveweights, indices of colostrum uptake and survival were recorded. There were no interactions between nutritional periods for lamb liveweight, apparent colostrum intake and survival, and ewe liveweight, condition score and total weight of lamb per ewe at the end of the study. At L91, ewe nutritional treatment during P21–50 or P50–139 had no effect on either ewe liveweight or body condition score. Ewe nutritional treatment during P21–50 had no effect on lamb birthweight. Lambs born to AdP50–139 ewes were lighter (P &lt; 0.05) than those born to MP50–139 ewes (5.32 ± 0.04 v. 5.48 ± 0.04 kg, respectively). Ewe nutritional treatment during P21–50 or P50–139 had no (P &gt; 0.05) effect on indices of colostrum uptake in lambs at 24–36 h of age. At L91, ewe nutritional treatment during P21–50 or P50–139 had no effect on lamb liveweight, survival or total weight of lamb per ewe. In conclusion, although considerable differences in ewe liveweight were observed during pregnancy, the nutritional treatments had no effect on the production parameters measured at the end of the study. These results indicate, first, that farmers can use early pregnancy as a period to control ewe nutrition when ewes are offered at least pregnancy maintenance levels of nutrition in the mid–late pregnancy period and, second, that there is no advantage from offering twin-bearing ewes a level of nutrition above their pregnancy maintenance requirements in mid–late pregnancy.

Improving the nutrition of Merino ewes during pregnancy increases the fleece weight and reduces the fibre diameter of their progeny's wool during their lifetime and these effects can be predicted from the ewe's liveweight profile

Nutrition of ewes during pregnancy can have permanent impacts on the production potential of their progeny. The hypothesis tested in the experiments reported in this paper was that improving the nutrition of Merino ewes during pregnancy and lactation increases the fleece weight and reduces the fibre diameter of their progeny’s wool during their lifetime. In addition, that these effects on the progeny’s wool production can be predicted from the ewe’s liveweight profile. At sites in Victoria and Western Australia in each of 2 years, a wide range in the liveweight and condition score profiles of Merino ewes was generated by varying the amount of supplements fed from joining to Day 100 of pregnancy and the amount of feed on offer grazed from Day 100 to weaning. The site in Victoria was based on perennial pastures and included both single- and twin-bearing ewes whereas the site in Western Australia was based on annual pastures and included single-bearing ewes only. The production and characteristics of wool from the progeny were measured until 51 months of age at the site in Victoria and 33 months of age at the site in Western Australia. The nutritional treatments and the resulting changes in ewe liveweight had significant impacts on the fleece weight and to a lesser extent the fibre diameter of wool produced by their progeny, but there were no consistent effects on other characteristics of progeny fleece wool. The fleece weight of the progeny was related to the liveweight change during pregnancy of their mothers (P &lt; 0.05) and the relationships were similar for the two experiments at each site. At the site in Victoria, a loss of 10 kg in ewe liveweight between joining and Day 100 of pregnancy reduced fleece weight by ~0.2 kg at each shearing until 51 months of age whereas gaining 10 kg from Day 100 of pregnancy to lambing had the opposite effect. The effect of changes in ewe liveweight during late pregnancy on the fleece weight of their progeny at each shearing was of similar magnitude at the site in Western Australia. When evident, the effect of the ewe liveweight profile on the fibre diameter of progeny wool was opposite to the effect on clean fleece weight and the effect of poor nutrition in early to mid pregnancy could be completely overcome by improving nutrition during late pregnancy. Twin-born and reared progeny produced ~0.3 kg less clean wool at each shearing (P &lt; 0.001) that was 0.3-μm broader (P &lt; 0.001) than that from single-born progeny at the site in Victoria. However, the effects of varying ewe nutrition and ewe liveweight change during pregnancy on fleece weight and fibre diameter of progeny wool were similar (P &gt; 0.05) for both single- and twin-born or reared progeny. Overall, these results supported our hypothesis and it is clear that the nutritional management of Merino ewes during pregnancy is important for optimal wool production from their progeny during their lifetime.

Managing the nutrition of twin-bearing ewes during pregnancy using Lifetimewool recommendations increases production of twin lambs

The effect on ewe and lamb production by differential management of single- and twin-bearing Merino ewes during pregnancy and lactation was examined. The hypothesis that the survival and productivity of single- and twin-born progeny is not affected by differential management of single- and twin-bearing ewes was tested. To test this hypothesis, two ewe flocks were monitored on a commercial property in the south-east of South Australia. The body condition score of one flock of ewes was managed according to Lifetimewool recommendations for southern Australian (Lifetimewool flock; n = 464). Lifetimewool recommendations are that body condition score should be 3.0 at mating and then allowed to decline to an average of 2.7, which is maintained until lambing. Twin- and single-bearing ewes were managed as separate mobs after pregnancy scanning to meet their energy requirements. The second flock was managed similarly to the commercial ewe flock and was representative of ewe management practices in the region (normal-practice flock; n = 464). At lambing, the condition score of the Lifetimewool flock was 0.7 condition scores units greater than the normal-practice flock. Ewe clean fleece weight and fibre diameter were greater in the Lifetimewool flock and their lambs had higher survival rates to weaning. Over three shearings, progeny from Lifetimewool ewe flocks produced more clean wool (P &lt; 0.0001) but there was no consistent effect on fibre diameter, staple length or staple strength. Twin-born lambs from ewes managed to Lifetimewool guidelines had a similar liveweight and produced similar quantity and quality of wool to single-born lambs managed to Lifetimewool guidelines, but still suffered higher rates of mortality to weaning. This suggests that it is possible to manage ewes pregnant with twins to ensure that their surviving progeny perform at a level similar to single-born progeny managed under similar targets.

Survival of twin lambs is increased with shrub belts

Abstract Perinatal lamb mortality is a major source of reproductive loss, particularly for twins. A study was conducted to determine whether provision of shelter in the form of shrub belts (a ‘maternity ward’) could increase survival of twin lambs compared with hedgerows, and whether hedgerows improve survival of single lambs compared with unsheltered paddocks. Measurements were recorded for Merino × Poll Dorset cross twin lambs born in hedgerows (phalaris or hessian) or shrub belts and single lambs born in hedgerows or unsheltered paddocks over the years 2007–2009. Records for 382 single and 726 twin lambs were used. The survival of single lambs was not increased (P = 0.06) by hedgerow shelter. The survival of twin lambs in shrubs was 10% higher (P &lt; 0.05) than that in hessian hedgerow shelter in 2008–2009 (0.77 cf. 0.70), associated with a reduction in deaths from starvation and/or mismothering and/or exposure. The hessian shelter was associated with an increased (P &lt; 0.05) growth rate to weaning of single lambs, but the growth rates of twin lambs were lower (P &lt; 0.05) in shrub than in hessian shelter. In 2010, a second study of 178 twin Merino × Poll Dorset cross lambs found that survival of lambs born alive was not improved by shrubs compared with unsheltered paddocks (0.80 versus 0.77; P &gt; 0.05). It is concluded that shrub belts which forced twin-bearing ewes to lamb in a sheltered environment reduced perinatal mortality in one of three datasets, but was not repeated. The shrubs take time to establish, and the benefit will be small if weather is mild during lambing.

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.

Merino ewes bred for parasite resistance reduce larval contamination onto pasture during the peri-parturient period

The peri-parturient period is crucial for controlling worms as the acquired immunity of ewes is disrupted, resulting in an increase in faecal worm egg counts. Two hypotheses were tested in this experiment – that ewes bred for worm resistance would have lower faecal worm egg counts than unselected control ewes, during late pregnancy and lactation, under similar but separate grazing areas; and also that numbers of infective nematode larvae would be lower on pastures grazed by resistant ewes than pastures grazed by unselected control ewes. Faecal samples were collected from resistant and unselected ewes in late pregnancy and early lactation, during the winter rainfall season, and analysed for numbers of Trichostrongylus colubriformis and Teladorsagia circumcincta. Pasture samples were taken 1 week before and 7 weeks after lambing started and analysed for infective larvae. In all sheep, worm egg counts rose 2 weeks prior to lambing and continued into lactation. Worm egg counts were significantly lower in the resistant ewes from 1 week before lambing to 2 weeks after lambing. There were no differences in egg counts between single- and twin-bearing ewes in the resistant line. However, twin-bearing control ewes had significantly higher egg counts than single-bearing control ewes. Following lactation, plots grazed by resistant ewes had substantially less contamination with T. colubriformis larvae, but there were no differences in numbers of T. circumcincta larvae. Our results demonstrate that sheep bred for worm resistance has lower worm burdens during the peri-parturient phase and that lambs born to resistant ewes face a lower larval challenge during their introduction to grazing. In our environment, selection for low worm egg counts has produced sheep highly resistant to T. colubriformis, but has had less impact on resistance towards T. circumcincta.

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 source and level of fish oil supplementation in late pregnancy on feed intake, colostrum production and lamb output of ewes

Supplementing pregnant ewes with fish oil to enhance the dietary supply of 20:4 n-6 and 22:6 n-3 has the potential to improve neonatal vigour and increase lamb survival rates. However, dietary fish oil has been shown to reduce colostrum production of ewes which can adversely affect lamb survival. To investigate the effects of source and level of fish oil in this response, 55 twin-bearing ewes were offered grass silage (0.5 kg dry matter per day) plus concentrates (0.5 kg/d) and supplemented with 0, 20 or 40 g/d herring (H) or salmon oil (S) during the final 6 weeks of pregnancy, giving a total of 5 treatments being control, H20, H40, S20 and S40. Salmon oil increased the supply of 18:2 n-6 (2.37) and 22:4 n-6 (1.98) but reduced the supply of 22:6 n-3 (0.84) relative to herring oil. Silage DM intake was marginally lower for S40 ewes ( P<0.05) but there were no dietary effects on ewe live weight or body condition score. Plasma non-esterified fatty acids (NEFA) ( P<0.05) and urea ( P<0.001) concentrations were elevated in ewes fed fish oil. Lambs born to control ewes had higher serum IgG concentrations than those fed herring oil ( P<0.01). Colostrum output at 10 h ( P<0.01) and total yield of colostrum ( P<0.05) were lower for fish oil-supplemented ewes. Concentrations of 10 h IgG ( P<0.05), 18 h fat ( P<0.001), 18 h total solids ( P<0.05) as well as outputs of fat ( P<0.05), protein ( P<0.01), casein ( P<0.05), IgG ( P<0.001) and total solids ( P<0.05) were reduced by feeding fish oil. Compared with controls, ewes fed herring oil had a higher 10 h lactose concentration ( P<0.05) while those fed salmon oil had lower outputs of 18 h protein ( P<0.05) and 18 h casein ( P<0.05). Offering 20 g/d, but not 40 g/d, fish oil increased the number of lambs weaned (+0.55 lambs/ewe; P=0.06) and the total output of weaned lamb (19.4 kg; P<0.05), but otherwise there were no effects of fish oil level and source on ewe or lamb performance. Results indicate that low levels of crude fish oil supplementation (up to 20 g/d) during late pregnancy improved lamb survival and output at weaning, but these benefits disappeared at higher inclusion rates.

The effect of late pregnancy supplementation of ewes with vitamin E on lamb vigour

The experiment measured lamb responses to supplementation of the pregnant ewe diet with vitamin E above requirement. Crossbred ewes were mated with either Suffolk or Texel rams. Twin-bearing ewes were randomly allocated (approximately 21 months of age at allocation) to one of four treatment groups (20 ewes per group, 10 mated with Suffolk and 10 with Texel rams). Treatments imposed were 50, 100, 150 or 250 IU supplementary vitamin E per ewe per day to give a four treatment by two sire-type factorial experimental design. Ewes were fed concentrates to meet energy requirements for stage of pregnancy and hay ad libitum. Diets were introduced approximately 6 weeks before lambing. Blood samples were obtained prior to introduction of diets, 17 days after introduction of diets and within 24 h of lambing from a subset of eight ewes per treatment (32 total). Colostrum samples were obtained from 10 ewes per treatment, 12 h after birth of the first lamb. All births were observed and a lamb vigour score was assigned to each lamb 5 min after birth. At 1 and 12 h after birth, rectal temperature, and at 12 h after birth, sex, crown-rump length and BW of each lamb were recorded. Mean ewe plasma α-tocopherol concentration prior to introduction of the diets was 1.5 μg/ml (s.e.m. 0.09) and did not differ between groups. There were positive linear (P < 0.001) effects of dietary vitamin E on plasma (17 days after introduction of diets) and colostrum (12 h after birth) α-tocopherol concentrations. Lamb vigour scores were superior (P < 0.001) for lambs sired by Texel rather than Suffolk rams but there were no differences as a result of vitamin E supplementation. Lamb mortality was low and unrelated to either sire or supplementary vitamin E. Lamb birth and weaning weights were also unaffected by vitamin E supplementation. Supplementing the ewe with vitamin E therefore had no effect on any lamb measurements.

Evaluation of 'Ceres Tonic' plantain (Plantago lanceolata) as a lactation feed for twin-bearing ewes

A field experiment evaluated the effect of plantain (Plantago lanceolata) on ewe and lamb liveweight changes and ewe faecal egg count (FEC) during lactation. Pregnant ewes were randomly allocated to either plantain or perennial ryegrass (Lolium perenne) pastures. Ewes remained on the treatments from one week before lambing until weaning. Keywords: lactating ewe, lamb, lactation, carrying capacity, internal parasites

Can Romney ram lambs whose scrotums had been shortened by the use of a rubber ring be used as an alternative to vasectomised Perendale rams for inducing early breeding activity in Romney ewe lambs?

AIM: To determine if exposure to ram lambs whose scrotums had been shortened by the use of a rubber ring would induce reproductive activity in ewe lambs, and determine if this technique was an effective alternative to vasectomised mature rams. METHODS: Seven hundred and forty-nine Romney ewe lambs, 7–8 months of age, were randomly assigned to one of three treatment groups. Treatments included exposure for 17 days prior to breeding to either mature vasectomised rams (Vasec), or ram lambs whose scrotums has been shortened via a rubber ring (Ram SS), or not being exposed to either vasectomised or short-scrotum ram lambs (Unteased). Using crayon marks, ewe lambs were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were weighed on the day of introduction of entire rams. All ewe lambs were diagnosed for pregnancy status using ultrasound. RESULTS: Unteased ewe lambs and those exposed to ram lambs whose scrotums had been shortened by the use of a rubber ring were less (p<0.05) likely to be marked and pregnant to the first 17 days of breeding than ewe lambs exposed to mature vasectomised rams. Twin-bearing ewe lambs were heavier (p<0.05) than their single-bearing counterparts at introduction of the rams. CONCLUSION: Exposure of ewe lambs to mature vasectomised rams is an effective means of increasing the numbers of ewe lambs bred and pregnant to the first 17 days of breeding. In contrast, a 17-day exposure to ram lambs whose scrotums had been shortened by the use of a rubber ring, at the ratios utilised in the present study, were not a suitable alternative to mature vasectomised rams for inducing early breeding activity in ewe lambs.

Effects of digestible undegradable protein (DUP) supply and fish oil supplementation of ewes during late pregnancy on colostrum production and lamb output

Studies in pregnant ewes have shown that fish oil supplementation during late pregnancy can increase lamb vigour at birth and may provide a means of reducing neonatal mortality in the sheep flock. However, fish oil also reduces colostrum production by the ewe which could offset the developmental benefits for lamb survival. To counteract the detrimental effects on colostrum, an experiment was carried out to investigate the effects of supplementing late gestation ewes with fish oil and digestible undegradable protein (DUP) on colostrum output and lamb performance. For 6 weeks prior to lambing, 32 twin-bearing ewes were offered grass silage ad libitum plus 550 g/d of one of four concentrates. The concentrates were iso-nitrogenous (195 g crude protein/kg dry-matter) and were formulated to supply 0 or 40 g/ewe/d fish oil and 55 g DUP/kg dry-matter (High, H) or 25 g DUP/kg dry-matter (Low, L) giving a total of four treatments: H0, H40, L0 and L40. Ewes offered fish oil had depressed intakes of silage dry-matter (DM), metabolisable energy (ME) and crude protein (CP) ( P<0.001) and lost on average 3.8 kg more live weight ( P<0.001) between 6 weeks pre-lambing and 24 h post-lambing. Mean plasma concentrations of globulin ( P<0.05) and urea ( P<0.001) during late pregnancy were elevated by fish oil. L40 ewes produced 681 g less colostrum ( P<0.01) and had lower energy ( P<0.001), total solids ( P<0.01), crude protein ( P<0.05) and ash ( P<0.05) outputs in colostrum during the first 18 h after lambing than all other treatments. Total lamb birth weights of ewes were similar for all diets but lamb output at weaning was 16.5 kg lower ( P<0.05) for L40 ewes, due to a reduction in litter size at weaning of 0.51 lambs/ewe ( P<0.05). Despite depressed forage intakes, the results of this study indicate that late gestation ewes can be supplemented with 40 g/d fish oil without detrimental effects on colostrum production or lamb output, providing the intake of metabolisable protein is maintained by increasing the level of DUP in the concentrate portion of the diet.