It is now a well established fact that high-level nutrition of the in-lamb ewe during the later stages of pregnancy results in heavy lambs of high vitality at birth and in good milking ewes. On the other hand, when ewes are poorly fed during the same period, or suffer a check, they produce underweight lambs of low vitality and have poor milk yields. While it is agreed that underweight lambs are undesirable, one is often asked whether the larger and sturdier lambs at birth maintain their superiority in later life, a problem on which relatively few results have been published. A study has therefore been made of a large number of birth and weaning weights collected as a normal routine at the Rowett Institute during the past few years.

It has been shown (Robinson, 1951) that in the ewe the number of ova shed can be increased by the injection of a single dose of mare serum gonadotrophin (P.M.S.) if this is given during the follicular phase of the oestrous cycle. The investigations described here were made to examine the usefulness of this treatment for increasing the lamb crop in commercial flocks.

Observations were made on 594 ewes of 3 breeds in 11 flocks (Romneys, 9; Cheviot, 1; Southdown, 1). Most ewes were purebred from old-established flocks. The Romneys were running on the marshlands and mixed farms of Kent and East Sussex, the South-downs were near Glynde, in Sussex, and the Cheviots were on a farm near Brampton in Cumberland. Management within the flocks followed the practice normal for the different breeds. Most ewes were 2½ to 4½ years old at the start of treatment; a few younger ewes (1½years) and some aged ewes were also involved.

In an earlier publication (Johansson and Hansson, 1940) it was shown that under the management conditions of the Red-and-White Cattle in Sweden the dam-daughter correlation was considerably higher for the first lactation yield than for the second, and it was also somewhat higher than that for the third lactation. The second lactation yield was found to be much more sensitive to variations in length of the preceding calving interval, or dry period, than was the yield in the later lactations, and probably it is also more sensitive to environmental influences. The yield during the first lactation is influenced by the age and the nutritional state of the cow at calving, but here no preceding dry period enters in as a variable. It was concluded that a preliminary evaluation of the production capacity of the cow can safely be based on her first lactation yield. Furthermore it was suggested that even when records are available for two or more lactations of a cow, the record for the second lactation should not be considered.

The incidence of hypomagnesaemic tetany in cattle and sheep can be reduced considerably by increasing the dietary intake of magnesium (Allcroft, R., 1954; Allcroft, W. M., 1947; Bartlett et al., 1954; Stewart, 1954) and the commonest method of supplementing the ration is to provide a mineral mixture containing magnesium oxide. While the feeding of these mineral supplements to animals wintered indoors is relatively straightforward, ensuring that animals grazing on hill and marginal land will obtain a regular supply of the mineral raises a problem. Where animals are receiving silage in addition to natural grazings during the winter, the inclusion of a magnesium compound in the grass at the time of ensiling is one method of increasing the magnesium content of the diet. The oxide and carbonate of magnesium are probably the safest compounds for feeding to stock, but unfortunately these are likely to have an adverse effect on the preservation, resulting in inferior silage. Experiments carried out in small silo units at Boghall Farm proved this to be the case (E.E.S.C.A. Ann. Rep. 1955). Magnesium sulphate is likely to have little effect upon the preservation of silage, and although this compound is not ideally suitable as a magnesium supplement owing to its laxative properties, it was decided to investigate the value of using it in restricted quantity and intimately mixed with the silage, as a suitable means of preventing hypo-magnesaemia when fed during the winter to a herd of 18 outwintered Galloway cows.

Bloat in ruminants is a digestive disorder arising from an abnormal distension of the rumen with gas, and may prove fatal. It is termed chronic when protracted due to physiological disorders and acute when transitory due to feed factors (Cole et al., 1945). Bloat in grazing ruminants is recognised as acute, although the chronic condition at pasture is known (Lyons, 1928). Acute bloat may result from a frothy admixture of gas and ingesta, or from free gas in the rumen (McIntosh, 1941).

The incidence of bloat is world-wide. It is reported most frequently in association with grazing highjy productive pastures and its unpredictability and rapid onset seriously hamper animal and pasture husbandry.

With the increased utilisation of land throughout the West of Scotland by the Forestry Commission, the problems arising from the integration of forestry and sheep-farming demand special attention. The Hill Farming Research Station at Lephinmore in Argyll has provided an opportunity over the past four years for the initiation of long-term experiments. These involve various preparatory studies and this paper describes a preliminary survey of the fragments of herbage in the rumen of sheep (after slaughter) with the object of assessing the seasonal variation in their grazing selectivity for heather. The Lephinmore hill is predominantly of heather. Since there are many divergent views as to the preference of sheep for heather, this survey was designed in a rather novel, indirect way to obtain more precise information. The rôle of heather as a dietary constituent is of added significance because, after the afforestation of the lower slopes of a hill, the sheep are then restricted to higher ground where there is greater snow cover in the winter.

For any programme of livestock improvement to be successful it is necessary to investigate the mode of inheritance of the various economic characters and their relative importance in the given set of circumstances. Many practical attempts at agricultural improvements have failed to give satisfactory results because the objective has not been well co-ordinated with the overall economic, environmental and even social conditions.

In this paper the possibilities of genetic improvement of a flock of Welsh Mountain sheep will be reviewed in the light of the results of investigations carried on at the College Farm of the University College of North Wales, Bangor, from 1949 to 1955. The investigations were made to determine the relative values and mode of inheritance of several basic measurable characters in the flock of 600 breeding ewes managed under typical hill conditions.

Toxaemia of late pregnancy (twin-lamb disease) is one of the principal causes of loss of in-lamb ewes in Great Britain. The mortality rate from this disorder alone in individual lowland flocks reaches 20% in certain seasons and occasionally 25% of the flock, even in winters when exceptionally severe weather is not experienced. In hill sheep with their lower lambing rate the disease is said to be infrequent. While no data are available for the loss from this disorder for the whole country, a conservative estimate, based on my own figures, is that 2% of the lowland lambing flocks die in an average season. If half of the 11 million breeding ewes in the United Kingdom are considered as lowland sheep, the total deaths each year from toxaemia are probably about 100,000 ewes and 200,000 lambs, representing a loss to the sheep industry of between £1 and £2 million per annum. In a difficult season such as 1954-55, the loss is probably nearer £2-5 million. As the disease is widespread in many of the principal sheep-rearing areas of the world, the annual loss in the Commonwealth, with over 100 million breeding ewes, is probably of the order of £10 million per annum.

Among the most important of the parasites of grazing animals are the nematodes inhabiting the alimentary tract of the sheep. The losses due to the presence of these worms are difficult to estimate but are certainly not confined to the results of disease outbreaks. In fact, recent research (Tayler, 1953; Spedding, 1953) has emphasised the losses which occur at sub-clinical levels of infestation, that is, at levels sustained by normal sheep.

Control of these parasites may be either ameliorative or preventive in character. Supplementary feeding and the use of anthelmintic drugs are of the former type; grazing management is essentially preventive. For the most part, anthelmintic drugs are now capable of preventing the outbreak of clinical disease, but they allow the presence of sub-clinical levels of infestation, as do most types of grazing management.

Dividing the meat carcass into its three main component tissues, bone, muscle and fat, it is known that they develop in a well-defined order, bone being the earliest maturing and fat the latest (Hammond, 1932). Of the three, muscle is the most important from the viewpoint of human nutrition and the factors influencing its growth obviously demand serious consideration. The literature on qualitative growth contains numerous references to microscopical meat studies, but, due to the diversity of conditions under which the observations were made, the results obtained cannot easily be co-ordinated. An investigation was therefore planned in which most of the major factors influencing growth and development of muscle in general, and the muscle fibre in particular, could be studied.

Existing information about the effect of inbreeding on production characteristics in dairy cattle leaves much to be desired. Sources are two-fold ; from experiments specially designed to get information on this and other aspects of inbreeding and also from the analysis of records made in closed herds. However, the experiments are few and in many of the second type of analysis the degree of inbreeding is not high. Furthermore, an examination of the detailed results in one breed, Holstein-Friesians in the U.S.A., shows little agreement in the results obtained. While agreeing in finding a decline in production as inbreeding progressed, the different investigators disagreed as to the magnitude of the effect. Even under ideal conditons, one should perhaps not expect too close an agreement because the genetic situation may well be quite different in the initial stock in the different experiments and genetic drift during inbreeding may further obscure the picture. In addition, if the inbreeding each generation is small, any selection that is practised may complicate the situation. Most of the programmes of deliberate inbreeding were not started simply to investigate the effects of the breeding system but rather to try to produce superior inbred stock.

Body length has long been emphasized by the Scandinavian breeders as being of paramount economic importance in the selection of pigs for the British market. (Rozycki; Jespersen and Madsen ; cited by Smith and Robison, 1934). The development of strains or breeds of pigs possessing some uniformity regarding body length may well assist materially in producing at home the type of bacon which the British housewife needs instead of the continued importation of such bacon from those countries which have for so long dominated our markets. The difficulty of assessing in the live pig what its carcass grade will be, or of forecasting in the weaner its potential quality as a baconer, calls for scientific investigation into the ways and means of doing this, particularly for the selection of pigs for breeding and improvement policies.

There is little doubt that the lowest costs of beef or milk production are achieved when the animals are grazed on pastures from which they obtain most or all of their sustenance. On the other hand the most expensive phase of cattle production is the winter period when stock are usually housed and must be hand-fed. The results from numerous investigations firmly support these assertions. In the large mixed farming area of the North-East of Scotland virtually no grazing is normally available from the middle or end of October until the beginning of May when normal grass growth has resumed.

There are two schools of thought concerning the most appropriate environment in which to select breeding animals. One says ‘ Always select animals under environmental conditions similar to those where they are to be used ‘. The other says ‘ Select breeding animals in the optimum environment so that they have the best chance of revealing their genetic capabilities ‘. Experiments on growth of laboratory mice and experience with European cattle in the tropics have shown the advisability of the first course in these cases. In regard to hill sheep and dairy cattle in Britain, on the other hand, practice favours the second course, but there is little experimental evidence to support it.

Selection work with the Rhode Island Red breed, involving the extensive collection of records, was first started at Wye College in 1948. Since that time the methods of selection employed have changed substantially in the light of the experience gained and the scheme, as it is operated at present, is shown diagrammatically in Fig. 1.

Sixty full-sister groups are recorded from first egg to the end of November. At least three full brothers of each of these sister groups.

In pasture research and feeding trials using the growing or fattening animal to provide a measure of output, a first essential is the accurate determination of liveweight.Recent reports of trials using bullocks, sheep and dairy stock (Grassl. Res. Sta. Rep., 1953; Waite et al., 1952; Dodsworth and Campbell, 1953) have emphasised that liveweight gains can be misleading when a large and unknown proportion of the gain is due to contents of the stomachs and intestines. This ‘ fill ’ in the capacious alimentary tract of the ruminant provides a large source of experimental error in the measurement of liveweight; it can also obscure the trend of useful liveweight gain, i.e. carcass increase.

The number of breeding sheep in a flock and the number of generations under selection will directly affect the genetic improvement possible. Both in cattle (Donald and El Itriby, 1945, 1946) and in pigs (Donald and Auerbach, 1942) a small average herd size and short life were found to have set severe limits to the breeding policies possible. The present report discusses this problem in lowland registered sheep flocks.

This paper is a report on preliminary work carried out at the Rowett Research Institute during the winter of 1951-52, in cooperation with Mr. Gill and Mr. Thomson.

What is known as stratification of the sheep industry in Scotland is the differentiation of enterprise into fairly distinctive types, roughly according to the altitude of the holdings. In the production of mutton, four main types of enterprise are concerned:—

• (1) breeding of hill ewes for replacement of hill stocks

• (2) breeding of first-cross ewes

• (3) breeding of second-cross lambs

• (4) fattening of second-cross lambs.