Cattle breed comparison and crossbreeding trials in Europe; A survey prepared by a working party of the European association for animal production

A Working Party of the European Association for Animal Production surveyed the breed comparison and crossbreeding trials which were being carried out in Europe. The survey summarizes the experimental work in the different countries and gives details on 86 separate projects concerned with breed and strain evaluation in pure and crossbreeding situations. The paper gives a general summary of the survey and recommendations on the methodology for future experiments. More detailed abstracts of the individual trials included in the survey are obtainable on request.     

Eine Untersuchung der Frühentwicklung der heterozygoten Kurzschwanzmaus (T/+)*

A study of the early development of the heterozygous short-tail mouse (T/+) Because of the great variability during early development, it is recommended for age determination of mouse embryos to consider also features of growth; in the succeeding stages the somites and the three humps (Buckel) provide firm criteria. Since murine types differ from each other in certain features, there is no uniform conception of the kind and the form of the tissues that are affected in gene disturbances. In contrast to the current conception that in the t-mutant the disturbance arises primarily from the chorda dorsalis, the author's findings lead to the conclusion that the neural tube and the cardiovascular system are primarily involved. Chorda disturbances apparently occur in the so-called normal mouse similar to the way they occur in T/t-mutants. Because of the often observed connection between chorda and neural tube, it is possible that neurectoderm is involved in the formation of the chorda; and because of this anomalies of the neural tube in the heterozygous short-tail mouse gain significance. Mesodermal defects were rarely present in the T/t-mutant, while are very impressive in the early development of the short-tail mouse. They are thougth to be related to a rise in blood pressure occasioned by peripheral disturbance of blood flow.     

THE INCIDENCE OF DYSTOCIA IN DORSET HORN EWES

The incidence of dystocia was recorded in flocks of Dorset Horn ewes lambing in winter, spring or summer and grazed at 8, 12 or 16 ewes per hectare over a ten-year period. The mean incidence of dystocia was 34% of ewes lambing. Significantly more ewes experience a difficult birth at winter (35%) and spring (39%) than summer (26%) lambings. Neither stocking rates nor pre-lambing ewe bodyweight were related to the incidence of dystocia. The incidence of dystocia was significantly greater in 2-year-old ewes than in any other age group. Foetal size was of major importance in the occurrence of dystocia. Approximately 60% of single and twin born lambs that had birth weights greater than 4.5 kg had a difficult birth whereas in lambs weighing less than 3.2 kg only about 10% were affected. Thirty-six per cent of all perinatal mortality was attributable to dystocia. Approximately 27% of single and 73% of twin presentations in assisted births were abnormal, 31% of all lambs assisted had 1 or both legs retained, 4% had posterior (including breech) presentations and the remaining 8% were of varied forms of malpresentation. Significantly more single male than female lambs experienced a difficult birth and the mean birth weights of single, twin and triplet born lambs that had a difficult birth were greater than the birth weights of singles, twins and triplets born normally.