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.

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.

Recent work, mainly American, has indicated the possibility of using implanted synthetic oestrogens to induce faster and more economical weight gains in fattening lambs. Little has yet been done in this country to repeat or to extend these observations, and a possible reason for this may lie in the difference between the organisation of the fat lamb industries of the United Kingdom and the United States. Here, as in New Zealand and in other countries rearing sheep principally on pastures, many lambs are sold fat at light weights, while those not so well finished at weaning may either be fattened on grass or other green crops, or be overwintered and fattened as hoggets on grass in the following spring. In the U.K. fat lambs are thus seldom fed dry feeds as they are under U.S. ‘feed-lot’ conditions, and are slaughtered at rather lighter weights than their U.S. counterparts.

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.

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.

The herbage dry matter intake of grazing animals may be estimated by chemical marker and faecal analysis methods (Raymond, 1954) or by pasture sampling methods.

Pasture sampling methods generally involve two main difficulties. The first is the low precision resulting from the variability of pasture yields. When intake is estimated from the difference between the yields of herbage on a given area sampled before and after the grazing period, the estimate bears the error variances of both the sample means. The second difficulty lies in ensuring that the estimated difference in yields is the true difference due to consumption. The samples must be cut below the level to which the animal can graze, and the amount of herbage growth during the grazing period must be estimated and allowed for. Growth can be estimated from the difference between the yield of herbage before grazing and the yield of protected herbage at the end of the grazing period.

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.

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 (1½ years) and some aged ewes were also involved.

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.

One of the advantages of keeping growing fattening pigs outside on pasture is that they are more healthy than those indoors (Fishwick, 1935), provided fresh ground, free from parasitic infections, is available. Reviewing American work, Morrison (1936) concluded that faster liveweight gains and improved efficiency of food utilisation are obtained from pigs full-fed on pasture compared with those full-fed in dry lot (also Fishwick, 1935; Smith et al., 1950). Pigs grazing outside in Great Britain usually receive enough sun on their skin to produce sufficient vitamin D to meet their requirements, except in adverse weather (Braude, 1954). Pigs at pasture have access to soil, which is a source of minerals (Davidson, 1930) and of vitamin B12 (Duckworth, 1955). Cunha et al. (1948) found that 5% of soil in a purified pig ration stimulated appetite and increased the haemoglobin value of the blood. Biggar (reported by Boden, 1952) obtained greater liveweight increases from pigs folded on pasture than from those folded on bare soil, showing that herbage is of value in addition to fresh air, sunlight and soil.

In the analysis of the causes of variation between cows of a given breed in milk production, differences between herds pose some difficult problems. The nature of this variation is of importance from several points of view in the discussion of breed improvement. The situation is complicated by the fact that the herds of any breed type do not form a uniform group but can be classified roughly into a sort of ‘social structure’ (Robertson and Asker, 1951). The discussion of variation between all herds of a given breed type can then be broken down into the variation between strata and that between herds in the same stratum. From the analysis of production data from herds using artificial insemination (Robertson and Rendel, 1954; Korkman, 1953) there is evidence that the genetic component is a small proportion of the total variance in these herds; and also that in Great Britain the genetic difference in yield between the dominant group of herds (which provide many of the bulls used in A.I.) and the herds using A.I. is small. This is in agreement with studies on breed structure. In this paper we shall discuss the genetic differences between members of the small group of important herds which dominate each breed. These usually supply a high proportion of the bulls used. If we have good estimates of the breeding values of such bulls from the production records of their progeny, we can then examine the different breeding herds according to the breeding value of the bulls bred in them. Evidence of this type has been presented for Jersey bulls in New Zealand (Castle, 1952) but without statistical analysis of the results, although inspection suggests that there are definite differences between studs.

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.

The theme of ‘Animal Production from Grass’ proved a most successful choice for the fifth ‘study meeting’ of the European Association for Animal Production, which was held at Reading during July. Representatives of seventeen countries were present, and all stayed in two of the University's halls of residence; this contributed on the social side towards the success of the meeting.

As a preliminary to the meeting, most of the visiting European delegates took part in a tour beginning with a visit to the Royal Show at Nottingham, where the Council of the Royal Agricultural Society extended its hospitality to the visitors. Particular interest was shown in the display of British breeds of livestock. Afterwards, visits were made to the research farm at Thurgarton and the Veterinary Research Unit of Messrs. Boots, and to Mr. Maurice Passmore's farm at Wormleighton.

At Reading, the theme for discussion was introduced by two main papers, each being followed by shorter reports on current research in the various countries.