Observations on dystocia in a romney flock

The mating and lambing records for 1964–1972 of a Romney stud that had been experiencing a serious dystocia problem were investigated. Until 1970 between 20 and 31% of ewes required assistance at lambing but this level then fell to 18% in 1971, 11% in 1972, 3.3% in 1973 and 4.0% in 1974. The decline in dystocia evident in the latter years of the investigation is considered to have been brought about largely by the culling of ewes that were repeatedly assisted at parturition and by the selection of rams that sired lambs of lower birth weight.

Dystocia in this flock was highly correlated with the mean birth weight of single lambs ( r =0.84, p<0.01). Fifty nine percent of assisted single lambs were males; ram lambs were heavier at birth than ewe lambs. Apart from the year 1966, primiparous ewes required no more assistance than older ewes and, except for that year, ewes bearing singles required the same levelof assistance as those bearing twins.

An effect of the sire on the incidence of dystocia was demonstrated for four of the eight lambings studied and was related to the birth weight of the lambs. Thirty four percent of ewes that had been assisted to lamb once had to be assisted again the following year as compared with a 16% assistance rate necessary for those ewes that had not been helped at the previous lambing, thus establishing a high level of repeatability for the condition (p<0.001).     

Studies on the epidemiology of Dictyocaulus filaria infection in Blackface sheep on a low-ground Scottish farm.

The excretion of Dictyocaulus filaria larvae in the faeces of Blackface sheep on a heavily stocked lowland farm in south east Scotland, showed considerable individual, week to week and year to year variation. Patent infections were first observed in lambs in May or June but the heaviest and most prevalent infections occurred in the autumn. Infection levels were generally low but infections tended to be prolonged and reinfection occurred following anthelmintic treatment until the late autumn or winter. Only a few very light, short-lived, patent infections were observed in yearlings or adult ewes. Pasture sampling and the use of tracer animals showed that the numbers of infective larvae on the pasture were minimal during the summer months but reached a low peak in the autumn.     

Pregnancy toxemia in a flock of sheep

A high prevalence of metabolic disease was evident in a large flock of sheep early in the lambing season. Pregnancy toxemia and secondary hypocalcemia were diagnosed on the basis of history, physical examination findings, and results of serum biochemical analyses. To decrease costs to the owner, pooled serum samples were used to determine the metabolic health status of the flock. Ewes close to the time of lambing were found to be in severe negative energy balance, which resulted in excessive fat mobilization as well as clinical signs associated with pregnancy toxemia and hepatic lipidosis. By nutrient analysis, it was determined that the ewes had an inadequate amount of fermentable carbohydrates, which provide glucose to support the additional nutrition required during late gestation. The diet provided to sheep during late gestation should contain sufficient glucose precursors to maintain adequate glucose availability to maternal and fetal tissues. To minimize the physiologic decline in dry-matter intake during late gestation (which results in accentuation of negative energy balance), high-quality feed ingredients should be fed to ewes during this period.     

Observations of dye test (DT) titres to Toxoplasma in a non-breeding flock of sheep

In this study nine sheep and one goat were tested by the Sabin Feldman dye test for the presence of antibodies to Toxoplasma spp over a period of 12 months. No significant signs of a seasonal variation in dye test titres of infected animals could be demonstrated. The possible source of infection of two sheep, exhibiting a sudden rise in antibody titre during the course of the observations is discussed.     

Derivation of a scrapie-free sheep flock from the progeny of a flock affected by scrapie

The Cheviot flock at the Institute for Animal Health's Neuropathogenesis Unit (npu) has endemic scrapie, which affects primarily vrq/vrq sheep and at high frequency. A new flock with a full range of PrP genotypes, including the highly susceptible vrq/vrq, has been produced on a separate site, from animals in the npu breeding flock, and it remains scrapie-free after eight years. In contrast, in a parallel flock at the npu farm, scrapie has reappeared after five years, although the animals were kept in separate accommodation from the scrapie-affected sheep. During this time the npu breeding flock continued to have scrapie cases. Although it is known that highly susceptible sheep can remain free of infection in a clean environment, this is the first report of the infection being removed successfully from the bloodlines of scrapie-affected sheep. The results confirm that scrapie is not a genetic disease dependent only on the PrP gene sequence, but requires both genetic susceptibility and an infectious agent.     

Aldicarb toxicosis in a flock of sheep.

Aldicarb toxicosis was diagnosed in 200 sheep that died suddenly. Carbamate insecticide toxicosis was suspected based on observed clinical signs (hypersalivation, diarrhea, urination, paddling, seizures, miosis, and deaths occurring within 1 hour). Tissue samples were submitted from 4 Columbian ewes for pathologic and analytical evaluation. Severe diffuse pulmonary edema was observed on gross and histologic examination. Inhibition of cholinesterase activity in retina (21.2-68.1% of normal activity, n = 3), brain (40.6-45.6% of normal activity, n = 3), and whole blood (27% of normal activity, n = 1) supported a diagnosis of carbamate toxicosis. Reversal of brain and whole blood cholinesterase activities (reactivation factor greater than 1.4) following an in vitro 1 hour incubation at 37 C was also consistent with carbamate poisoning. Aldicarb toxicosis was confirmed following its detection in rumen contents at 1.5, 5.5, and 334 ppm using both high-pressure liquid chromatography with UV detection and gas chromatography with nitrogen/phosphorus detection.     

Immunoglobulin concentrations in Scottish Blackface lambs on a hill farm

The serum immunoglobulin concentration in one- to 11-day-old Scottish Blackface lambs born outdoors on a hill farm were very similar to those in Scottish Blackface lambs born indoors on an experimental lowland farm. The concentrations were significantly higher in single lambs than in twins, and in lambs which survived for six months than in lambs which died, and showed significant annual variations which could not be related to the weather. They were significantly correlated with the ages of the dams, the lambs' gains in weight to weaning, but not with the weights or ratios of weights of the lambs and ewes after lambing, nor with the birth-coat types of sexes of the lambs. There were wide variations in the capacities of the abomasums at birth.