Twin-bearing Ewes Research Articles

The influence of perinatal undernutrition of twin-bearing ewes on milk yields and lamb performance and the effects of postnatal nutrition on live weight gain and carcass composition

1. Studies were conducted to measure the influence of perinatal undernutrition of twin-bearing ewes on ewe milk yields and lamb performance in early lactation. Comparative studies were conducted with lambs to measure the effects of postnatal nutrition on lamb performance and carcass composition. The major objective of this work was to determine the extent of the influence of postnatal nutritional deprivation of lambs.2. From 8 weeks prepartum to 4 weeks postpartum each of forty twin-bearing ewes was given daily 0.30 MJ of ME/kg body-weight (W)0.75. Measurements were made of ewe body-weight changes, milk yields during the first 4 weeks of lactation, and of lamb performance.3. There were three postnatal experiments with lambs of ‘light’ and ‘normal’ birth weights, wcaned from the ewes at 72 h. One hundred and four lambs were used and they were individually reared on separate allowances of lamb milk-substitute for 8 weeks. They were subsequently given a lamb concentrate ration. In Expts 1 and 2 the lamb concentrate was fed ad lib. to ‘slaughter’ live weight. In Expt 3 the concentrate was restricted for 8 weeks post weaning and then fed ad lib. A carcass analysis (bone, muscle, fat content) was conducted on all lambs after slaughter. In the first experiment, half the lambs were slaughtered at 8 weeks of age on being weaned off the milk substitute, and a carcass analysis was carried out.4. The mean net body-weight loss per ewe from commencement of late pregnancy to 28 d post partum was 23.8 kg. The over-all mean daily milk yield was 843 g/d. The mean growth rate of the lambs was 97 g/d during the 4-week measurement of ewe milk yields.5. Live weight gain of lambs subjected to restricted milk-substitute allowance (125 g/dry matter (DM) per d) was low, irrespective of lamb birth weight. The average daily gain over the 8-week postnatal period was 86.5 g/d on restricted milk allowance compared with 244 g/d for those fed ad lib. Conversely, the food intake and growth rate of these lambs were almost identical during feeding on ad lib. concentrates. This clearly reflected a response to compensatory food intake which was independent of either birth weight or postnatal milk allowance. The average daily gain of lambs, before weaning, on the restricted milk allowance was very similar to that of the lambs being suckled by ewes subjected to perinatal undernutrition. The effects of postnatal undernutrition of lambs was particularly reflected in the time required to reach ‘slaughter’ live weight. The period of time varied from 117 d for those on ad lib. food intake to 169 d for lambs on restricted food intake.6. The major effect of postnatal undernutrition on carcass composition was evident in the lambs slaughtered at 8 weeks in Expt 1. The percentage carcass fat was 4.7 for those on the low milk allowance. The carcass composition of all lambs at ‘slaughter’ live weight was similar. It would appear that lambs on a restricted milk intake before weaning deposited more fat during the subsequent period of compensatory food intake.7. It is evident from the present results that postnatal growth retardation in lambs reflects either perinatal undernutrition of twin-bearing ewes, or postnatal undernutrition of the lambs due to inadequate milk availability from the dam.

Relationship between plasma corticosteroids and weight change in recently parous lactating and dry sheep

Twin-bearing ewes were assigned to three treatments at lambing. Treatment 1 was the adult with both lambs retained; treatment 2 was the adult with one lamb retained; and treatment 3 was the adult alone. All sheep were fed on an amount calculated to maintain an adult and one lamb, and consequently animals in treatments 1, 2 and 3 lost, maintained and gained weight respectively. Chronic under-nutrition of the lactating ewe (treatment 1) resulted in a small increase in the maximum corticosteroid binding capacity and a large increase in total corticosteroid levels in peripheral plasma, resulting in a significant increase in biologically active (free) corticosteroid concentrations. In dry sheep (treatment 3) no such increase in free hormone concentration occurred. There was a significant negative relationship between free corticosteroid concentrations and weight change during both the 2-week intervals and the entire 6-week experimental period.

Relationship between plasma progesterone in late gestation and the incidence of dystocia in romney ewes

Thirty-eight percent ( 6 16 ) of the ewes with a previous history of dystocia and 15% ( 2 13 ) of the ewes with no dystocia in 4 lambings, had difficult births in 1976. Despite large variations in plasma progesterone concentrations among ewes at the same stage of gestation there were no differences in the progesterone concentration during the last 30 days of gestation for both single- and twin-bearing ewes with or without a history of dystocia, nor for single-bearing ewes with or without a dystocia. The progesterone concentrations declined during the last 10 days before parturition in ewes with and without dystocia. The lambs from single-bearing ewes with a dystocia did not have heavier birth weights than the lambs from single-bearing ewes without a dystocia.

Prediction of the onset of parturition in sheep from observations of rectal temperature changes

The rectal temperatures of 106 single and twin-bearing Corriedale ewes with 9 months fleece were recorded over the period commencing at least 1 week prior to lambing. A fall in rectal temperature below 39.20°C or 39.85°C occurred respectively in more than 80% of single and twin-bearing ewes within 48 h of lambing. Similar falls in rectal temperature were also recorded in about 20% of ewes more than 48 h from lambing. Variations in weather conditions probably influenced the accuracy of selection.

Effect of salt water ingestion on pregnancy in the ewe and on lamb survival

The addition ot sodium chloride, to provide concentrations of 1.0 and 1.3?, to the drinking water of pregnant ewes caused distress at parturition to some of the ewes and neonatal mortalities in their lambs. The effects were more evident in older sheep (aged 7 years) than in younger (3-year-old) animals and were associated, in general, with ewes which carried twin lambs. Progesterone levels in the blood plasma of sheep were higher in twin-bearing ewes than in ewes with single lambs, both for control ewes drinking fresh water and for ewes drinking saline. Drinking 1.3% saline augmented the increase in progesterone levels in older ewes bearing twins. Cortisol levels were normal in all ewes.Plasma levels of potassium and chloride were significantly higher and calcium and magnesium levels lower in pregnant ewes which received saline.It is suggested that the adverse effects of salt water ingestion in twin-bearing pregnant ewes could be due to an excessive retention of potassium and chloride, brought about by a disturbance of normal sodium homeostatic mechanisms associated with the pregnant state of the animals.

Variation in intake among group-fed pregnant Scottish Blackface ewes given restricted amounts of food

SUMMARYThe intakes of concentrates and hay by individuals in three groups of ewes were estimated at three-weekly intervals in late pregnancy from faecal output; chromic oxide was incorporated as a marker in the concentrates. The groups were: (1) 16 mature ewes, (2) 16 2-year-old ewes, (3) eight mature and eight 2-year-old ewes. A constant daily hay allowance of 734 g dry matter (DM)/sheep was given but the concentrate was increased from an equivalent of 96 g DM/sheep at the beginning of the experiment to 435 g at the end. Individual concentrate intakes were most variable when the group allowance was small (CV over 50% in the mixed group) but variation decreased when amounts of concentrates were increased to contribute up to 47% of the total digestible DM intake. The CV for the total digestible DM intake ranged from 13 to 24%.The younger sheep were at no disadvantage when penned with mature ewes. Intakes by individual ewes were compared with their calculated requirements and several twin-bearing ewes were shown to have a substantial energy deficit which was confirmed by their higher plasma ketone concentrations.A major practical difficulty in group-feeding pregnant ewes is to ensure that the ewes with the highest foetal burden are adequately fed.

Energy supplementation of silage for ewes in late pregnancy

SUMMARY1. Four groups of 20 ewes were individually fed in late pregnancy on: (1) silage ad libitum, (2) silage ad libitum and 12 kg rolled barley, (3) silage ad libitum and 23 kg rolled barley, (4) pelleted milled dried grass ad libitum. The concentrate was offered on a rising plane over the last 6 weeks of pregnancy. After parturition the ewes and lambs were put on spring pasture.2. The intake of silage by twin-bearing ewes fell slightly but nonsignificantly during week 16 of pregnancy but thereafter remained steady up to lambing. There was no other decline in intake on any of the treatments. Barley, however, significantly depressed silage intake when the quantity was increased above 282 g per day.3. Single-bearing ewes, except those on treatment 1, gained in net body weight during late pregnancy. Twin-bearing ewes on treatment 4 gained in net body weight while those on the other treatments lost weight.4. Birth weights of single lambs from ewes on treatment 1 were significantly lower than those from treatment 3. This was the only significant difference in birth weight or subsequent growth rates of single lambs. Birth weights of twin lambs on treatment 1 were significantly lower than those on the other treatments.5. The birth weight of twin lambs appeared to be an important determinant of subsequent performance, and may thus be a valuable criterion of the adequacy of the ewe's diet in late pregnancy.6. With medium-quality autumn silages, 12 kg of barley given during late pregnancy is sufficient to ensure good reproductive performance in ewes.

A study of food intake and production in grazing ewes II. The interrelationships between food intake and productive output

1. Observations were made during the autumn and spring of 1959–60, 1960–61, and 1961–62 on pregnant and lactating Clun ewes of mixed ages grazing under natural conditions. The pattern of food intake during pregnancy and lactation, the output achieved in the form of weight of lambs produced at parturition, milk yield, and bodyweight change of the ewes themselves was investigated. The interrelationships between these factors, as influenced by the feeding of supplementary concentrate, either for 7 weeks before or 7 weeks after lambing, or during both periods, was elucidated.2. Daily dry-matter intake was found to be of the order of 1·5–2·0 kg. for this type of ewe, but there was considerable individual variation (coefficient of variation about 20%). Intake did not increase concurrently with the demands of the foetus during the later stages of pregnancy, and even became depressed as parturition approached. Immediately after lambing there was a spectacular increase in intake, which, after rising to a peak, was maintained at a high level during the lactation. Ewes receiving supplementary concentrates showed an increase in food intake over those unsupplemented, but this increase was less than the amount of dry matter fed in the supplement, even on rather bare pasture.3. During the early stages of pregnancy there was no apparent difference in the weight gains of singleand twin-bearing ewes, but during the last 8 weeks prior to lambing twin-bearing ewes made greater weight gains. In relation to weights taken just after parturition ewes producing twins had lost most weight. Unsupplemented ewes lost more weight than those receiving supplements. Lack of supplementation prior to lambing only limited production in the case of twin-bearing ewes.

Studies on the carbohydrate metabolism of sheep. XVIII. The metabolism of glucose, free fatty acids, ketones, and amino acids in late pregnancy and lactation

The metabolism of glucose, free fatty acids (FFA), ketone bodies, and amino acids in late pregnancy and lactation was studied at three levels of feeding in an experiment designed to measure the increase in nutrient requirements of ewes with advancing pregnancy.The plasma FFA level is a more sensitive criterion of undernutrition during pregnancy than the level of blood glucose or ketones. In ewes on a constant feed intake and in medium body condition approaching late pregnancy, the rate of mobilization of fat reserves necessary to maintain caloric homeostasis, as indicated by plasma FFA level, was closely correlated with total foetal weight in late pregnancy and with the level of milk production in the first month of lactation. However, these ewes were unable to maintain blood glucose levels in the normal range in late pregnancy; severe hypoglycaemia was present in twin-bearing ewes. Caloric homeostasis was best maintained in fat ewes fed ad libitum; variation in blood glucose and FFA levels during late pregnancy and early lactation was minimal, in spite of a marked and variable decline in feed intake in twin-bearing ewes in late pregnancy. Reduction of foetal demand for nutrients may prevent or defer the breakdown of homeostatic meohanisms, but appears to play a minor role in the maintenance of caloric homeostasis in the undernourished pregnant ewe. However, reduction in the level of milk production is a major factor in the undernourished lactating ewe; severe hypoglycaemia and hyperketonaemia are thus prevented. The metabolic effects of high foetal requirements of amino acids are discussed in relation to observed variations in plasma amino acid Level in late pregnancy.

Studies on the carbohydrate metabolism of sheep. XVII. Feed requirements and voluntary feed intake in late pregnancy, with particular reference to prevention of hypoglycaemia and hyperketonaemia.

The increase in nutrient requirements of ewes with advancing pregnancy has been measured in terms of the additional feed necessary to prevent hyperketonaemia, with particular reference to the difference between ewes carrying single and those carrying twin lambs. The additional feed required during late pregnancy to prevent the ewe drawing appreciably on body reserves depended on the total foetal weight. In twin-bearing ewes the increase in the last 2 weeks of pregnancy was as high as 80% of the ewe's own maintenance requirements; the total requirement usually exceeded the voluntary feed intake during this period. It is concluded that the efficiency of utilization of the metabolizable energy of the additional feed is low, and that the additional feed requirement depends on the bodily condition of the ewe. In contrast to ewes in medium body condition, the voluntary feed intake of fat, twin-bearing ewes declined markedly in late pregnancy. This decline was not simply a consequence of reduction in abdominal space due to the large volume occupied by twin foetuses or by abdominal fat. The fat pregnant ewe, when undernourished as a result of a marked decline in voluntary feed intake, was better able to maintain blood glucose, and hence blood ketone levels, in the normal range than the ewe in medium body condition, but there was evidence that birth weights and viability of twins were low. In consequence, the usefulness of ketone level as a general criterion of undernutrition during pregnancy is restricted, but it is suggested that the technique used has special applications in nutritional studies on pregnant ewes.