Changes in Cu concentration in the livers of adult Scottish Blackface (B), Welsh Mountain (W) and B x W ewes fed diets containing 4, 9, 17 and 29 mg Cu/kg D.M. were measured over a 28-week period. Measurement continued during two further periods of 18 weeks when first all sheep were fed the diet containing 4 mg Cu/kg D.M. and finally, when 4 mg Mo/kg D.M. was added to this diet.During the first period the increase on all diets was least in B ewes and, apart from the 4 mg Cu/kg D.M. diet, greatest in W ewes; this difference increased as the Cu in the diet increased. The rate of increase for all ewes diminished towards the end of the period. All breed types retained proportionately less Cu in their livers as the Cu in the diet increased; at one extreme B ewes fed 17 or 29 mg Cu/kg D.M. retained equal amounts.When during the second period all sheep were fed the 4 mg Cu/kg D.M. diet the Cu concentration in their livers decreased, the rate of decrease being greatest for ewes whose mean concentration in the liver was highest, but at similar concentrations the decrease was greater in B than W ewes. During the final period the decrease was faster and was again associated with the mean Cu concentration, but the decrease was not significantly affected by breed.Throughout the trial, W ewes had the highest concentration of Cu in their plasma, whilst B ewes and ewes fed the 4 mg Cu/kg D.M. diet throughout had the lowest concentrations both in plasma and in their kidneys at slaughter.The results show that breeds differ in their ability to retain Cu from the diet in their livers. The magnitude of these differences depends on the intake of Cu and Mo from the diet and is affected by the concentration of Cu in the liver. Breed differences in the absorption and endogenous loss of Cu are suggested.

The incidence of lamb mortality from birth to 8 months of age has been studied over a 6-year period in an upland, grassland flock of sheep comprising the Scottish Blackface, Cheviot and Welsh Mountain breeds and the crosses among these breeds. Each breed and cross-bred type was maintained at varying levels of inbreeding. Approximately half the lambs which died were stillborn or dead on the day of birth, nearly 40 % died thereafter but before weaning and about 10% after weaning.Post-mortem examinations on 586 of the 632 lambs which died from among the 2453 born attributed death on average to two causes per lamb. Approximately 11 % of the causes were stillbirths or delayed births; 11 % were cases of dystokia; congenital defects of various types accounted for about 10% of the causes; 25% made reference to weakly lamb, exposure or starvation; 14% to infectious diseases and 16% to noninfectious diseases. The extent to which causes of death occur together is examined.Breeds differed in mortality rate with the Welsh the lowest and Cheviot the highest. Cross-breds were better than the average of the pure breeds but this advantage emerged only in the period between 3 days and. 6 weeks of age. Inbreeding, both of dam and of lamb, increased mortality. Lambs from dams which were crosses of inbred lines had the best survival. Litter size, type of rearing, parity of dam, sex of lamb and birth weight also had significant effects on mortality rate. INTRODUCTION describe breed differences in relation to specific causes of death. Many studies of sheep flock performance provideThe present study was initiated primarily with information on the incidence of lamb mortality in the latter end in view: to document the lamb different countries and farming circumstances and mortality rate in relation to three breeds and their at different periods between birth and weaning, crosses kept together as a single flock and also subSome describe the effect of factors such as number jected to intense inbreeding. The effects of breed, of lambs born, parity, management, nutrition and cross-breeding and inbreeding were further studied other environmental variables and a smaller number m relation to the causes of death as identified at of papers present information on causes of death, post-mortem examination. Other factors affecting Although these reports encompass many breeds and variation in overall mortality and the incidence of crosses of sheep, only a few can be interpreted as different causes are also examined, showing whether genetic variation contributes sigAn early finding in this flock was that both breed nificantly to lamb survival and even fewer papers a n d breeding system affected overall lamb mortality

Lambs, 9 weeks of age, the offspring of sires of the Scottish Blackface, East Friesland, Finnish Landrace, Suffolk and Texel breeds mated to Scottish Blackface females, as a common maternal breed, were given diets containing 12 or 20 mg copper per kg dry matter for 13 weeks. Concentrations of liver copper and of copper and aspartate amino-transferase in the plasma were measured regularly, and the concentrations of copper in the kidney, mandible and cheek muscle were also measured terminally. Livers were examined for histological symptoms of copper toxicity.Wide breed variation was apparent in liver copper concentration after 6 weeks and in plasma aspartate aminotransferase concentration after 9 weeks. At slaughter, total liver copper and kidney copper concentration showed significant breed variation. For all traits, the Texel-cross lambs had the highest concentrations, followed by the Suffolk crosses, and the Blackface had the lowest. The proportion of ingested copper retained in the liver of the Texel-cross lambs was twice that of the Blackface lambs (0·137 v. 0·056), with the other breed crosses intermediate.There was a significant difference between diets for liver, kidney and mandible copper concentrations, plasma aspartate amino-transferase concentration, and for total liver copper but not for cheek muscle. Both diets produced elevated plasma aspartate amino-transferase concentration and histological symptoms of copper toxicity in the livers of some lambs.The results show large breed differences in the susceptibility to copper poisoning, some breeds being at risk when given diets containing 12mg copper per kg dry matter for long periods. There was no suggestion that breeds differed in resistance to poisoning other than through different retentions of copper consumed

Growth rate and the concentrations of various biochemical constituents were measured in 2 years in lambs from two lines, selected on low (L) and high (H) copper (Cu) concentrations in plasma, and from two unselected pure breeds, Scottish Blackface (B) and Welsh Mountain (W). The lambs grazed improved hill pastures and half were given Cu supplements.H lambs were always heavier and were fattened for slaughter earlier than were L lambs, differences that were not completely eliminated when supplementary Cu was given. In both years, the improvements in growth rate due to supplementary Cu varied with genetic type (average L 20·5 (s.e. 2·5); H 5·7 (s.e. 2·6); B 25·1 (s.e. 3·7); W 8·1 (s.e. 3·3) g/day). Growth rates of supplemented lambs were L 100 (s.e. 2), H 104 (s.e. 2), B 134 (s.e. 5), W 103 (s.e. 3) g/day.At 6 weeks of age, unsupplemented lambs trom all genetic types were hypocupraemic and, at all ages, unsupplemented L and B lambs had lower concentrations of Cu in plasma and superoxide dismutase (SOD) activity than had unsupplemented H and W lambs. Supplemented lambs always had greater concentrations of Cu in plasma and SOD activities than had their unsupplemented counterparts. Supplementation increased the haemoglobin concentration for B (in year 2) and L lambs but not for H and W lambs. Cholesterol concentrations in plasma were unaffected by selection but were slightly higher in unsupplemented lambs. The concentration of total protein and the activity of aspartate transaminase were unaffected by genotype or Cu supplementation. In the liver of lambs at slaughter, the concentration of Cu was lower for unsupplemented lambs and inversely related to the concentration of iron.It was concluded that (i) genotype was an important determinant of hypocuprosis; (ii) the degree of hypocuprosis could not be predicted from herbage analyses alone, but instead may be predicted from biochemical assessment of the lamb; and (iii) the dose of Cu supplement used was inadequate for L and B lambs and recommended levels could be increased, within limits, without risk of toxicity.

1. The progression of Heinz body anaemia was studied in groups of lambs of low- and high-copper status, produced through breeding or Cu supplementation, when they were transferred from improved pasture to rape (Brassica napus L.) in autumn. Some lambs had previously received selenium by injection. The Cu and Se supplements markedly increased superoxide dismutase (EC 1. 15. 1. 1; SOD) and glutathione peroxidase (EC 1. 11. 1. 9; GSHPx) activities respectively in the erythrocytes, and both supplements had elicited growth responses at pasture.2. At the time of transfer to rape, lambs not treated with Cu had lower whole-blood haemoglobin (Hb) concentrations and a higher percentage of erythrocytes containing Heinz bodies (6.6 v. 3.7%, P < 0.01) than Cu-treated lambs: the corresponding effects of Se treatment were similar in direction but lower in magnitude (P < 005).3. After grazing rape for 2 weeks the mean Hb concentration had fallen by 30 g/l while Heinz body count had increased from 5 to 25%. However, counts were negatively correlated with the initial values and were unaffected by the Cu and Se treatments which maintained high plasma Cu concentrations and SOD and GSHPx activities.4. The results provide the first evidence that Cu deficiency can induce Heinz body formation and the anaemia in grazing Cu-deficient lambs may be partly haemolytic in origin. The concomitant Se deficiency added marginally to the problem but neither the separate nor combined deficiencies increased the susceptibility of lambs to brassica anaemia.