The recent increase of some 40 per cent, in the country’s pig population has been instrumental in bringing about one of those periodic renaissances in pig housing which appear to be not uncommon in the history of agriculture. The importance of good pig housing as an essential factor to efficient pig production and subsequent pig profitability is probably more widely recognised today than ever before. We must have more home-produced food, therefore we must keep more pigs, and if we are to do so profitably we must have good pig housing.

This paper will in the main deal with the possibilities of the use of progeny testing for the improvement of livestock, in particular under British conditions. Before dealing with individual species, it will perhaps be of value to consider the problem generally and create a framework in which the practical discussion may more fruitfully be carried on.

Let us consider first then an ideal case in which we are dealing with a large population of animals all kept under the same general conditions of management. In such a situation, it is possible to predict, using recent advances in population genetics, the probable genetic improvement that could be achieved by different selection programmes. The basic factor that needs to be known for such a calculation is the heritability of the character for which selection is practised—the accuracy with which the breeding value can be predicted from the performance. From the heritability, the accuracy of a progeny test in measuring the breeding value of a sire can be calculated and by this means the probable rate of advance in a progeny testing programme can be evaluated.

The two fundamental methods for genetical improvement of livestock are selection on die basis of performance and mating according to relationship. The most familiar forms of the latter are crossbreeding and inbreeding according as mates are chosen which are less closely or more closely related than the average of the breed.

The possibilities of inbreeding, followed by crossing, were exploited in the production of ‘ hybrid corn’ in U.S.A. and the success achieved led to the hope that similar methods might be successful in livestock breeding. Accordingly the Regional Swinebreeding Laboratory organised a programme of producing inbred lines of pigs and then crossing them. During the 12 years of this programme, about 90 inbred lines have been started and about 50 still survive. Inbreeding degeneration is greatest in those characters, such as fertility and viability, which have been subject to intense natural or artificial selection. The inbreeding decline in growth rate and economy of food utilisation is considerably less. When the lines are crossed in pairs the average performance of the first cross pigs is the same as that of the initial population.

In 1945 the Milk Marketing Board (M.M.B.) of England and Wales undertook responsibility for the development of an A.I. service to cover large areas of the two countries.

By 1951, a total of 24 main Centres had been set up, housing some 600 dairy and beef bulls and supplying semen to 77 Sub-Centres. During the year ending 31st March, 1952, approximately 707,000 first inseminations were carried out, representing 25% of the available cattle population. Further progress continues to be made and it is estimated that this proportion will be raised to 30% for the corresponding year ending in 1953.

From the outset it has been agreed that the rate of cattle improvement through A.I. will be largely dependent upon the use made of the older progeny-recorded bulls available to the scheme. Here it should be noted that the M.M.B. took over responsibility for milk recording under ‘ National Milk Records ‘ in 1943. By adopting a system based upon lactation record cards, it was possible to establish in 1947 a central clearing house for milk records of animals registered with Breed Societies, viz. the Bureau of Records. One of the main services operated by the Bureau is that of progeny recording for sires and summaries of bulls fulfilling certain requirements are now published annually.

I want to correct one or two misconceptions about the way the Danes have sought to improve their native Landrace breed, to try and decide the extent of the improvements which can be fairly attributed to progeny testing, and to describe a few of the features which are characteristic of Danish methods. Owing to the shortage of time I shall refrain from giving any account of the mechanics of testing in Denmark. As this has often been reported you should have sufficient knowledge of the daily procedure at testing stations to provide an adequate background to this paper.

I am very glad to have this opportunity of discussing litter testing, although I imagine tliat most of you are familiar with the work which we are carrying on at Stoke Mandeville. To recapitulate the set-up as briefly as possible, we receive half-litters of three hogs and one gilt (from litters of not less than eight weaned), aged 65-70 days so that the first test weighing can be carried out at exactly ten weeks of age. Environmental conditions have been arranged so that each team of pigs receives as near standard treatment as possible. Each lot has its own 8 foot x 7 foot wooden pig hut facing south, with a 9 foot x 8 foot enclosed concrete run. The pigs are kept bedded down on a good depth of long straw litter and a Fordham automatic drinking bowl (fitted with a soft spring) is available to each house. Feeding is simplified by means of three-compartment Seaford self-feeders which are kept fully supplied with dry Sow & Weaner Meal (No. 1) until the pigs reach 110-120 lbs. liveweight (17 weeks).

The credit for the discovery that antibiotics in stable form added to feedstuffs (in amounts so small that they resemble vitamins) have growth-promoting properties, goes to Lederle Laboratories, a subsidiary of the American Cyanamid Company. This was in 1948 and was revealed during studies with residues following the manufacture of aureomycin. It was found that these were a rich source of vitamin B12 which had been discovered to have growth-promoting properties when added to all-vegetable diets. But the aureomycin residues contained a further stimulus to growth which was later found to be related to the antibiotic itself.

The progeny test is generally regarded as an important aid to selection in livestock improvement. It is by no means a new method, but it seems to be in the limelight today. The usual methods of selection have brought us to a certain standard of performance, and apparently any further imporvement can only result through the application of the progeny test.

It is worth pointing out that cattle, especially dairy cattle, pigs and poultry have received more attention by the scientist than sheep. This may be due to the fact that these animals are more under the direct control of the breeder than sheep. They require daily attention whereas a hill flock of sheep may not be seen for weeks or months by the breeder. Again one has definite objectives in view when breeding dairy cows or hens; one can weigh the milk and count the eggs but the task of the hill sheep worker is considerably more complicated.

The first move to establish an international society for animal breeding was made during the Fourth International Congress of Animal Husbandry held at Zürich in 1939. The idea was revived in 1946 when the Swiss Society of Animal Husbandry again took up the matter, with the result that a meeting was held in Zürich in October 1947, attended by Mr. Alec Hobson and Mr. I. L. Mason representing the British Society of Animal Production. At this meeting it was agreed that an international organisation composed of private societies directly concerned with animal production was highly desirable and a preparatory committee was elected to prepare draft statutes. The United Kingdom was a member of this committee. The secretarial work was entrusted to the FAO Temporary Bureau in Europe, and was in fact mainly carried out by Dr. I. Moskovits of the Animal Production Branch.

I propose taking a pretty wide interpretation of the term progeny testing. When selecting poultry for improved economic characters, most of these characters such as egg numbers, viability and disease resistance in which we are interested have a low heritability and consequently progeny testing is an essential poultry breeding technique. During the last 15 years in England we have mainly been trying to improve the economic characteristics of egg production, but now the Americans are showing us that if we follow closely their broiler industry we can develop a valuable industry for the production of poultry meat in Britain which makes better feed utilisation of scarce concentrated feeds than any other form of meat production. The heritability of meat conformation in poultry is high but I believe progeny testing will come into the picture of selection for better broiler strains, because such strains must be capable of growing fast and evenly with the most efficient feed conversion ratio whilst being housed together in large mobs of manv thousand of chicks.

There is set up under the name “ European Association for Animal Production,” in French “Fédération Européenne de Zootechnie “; in Italian “ Federazione Europea di Zootecnia“; in German “ Europäische Vereinigung fur Tierzucht “ an international organization, whose object is to promote the improvement of the technical and economic conditions of animal production by all means contributing to its better adaptation to the needs of mankind.

As a provisional measure, animal production organizations in non-European countries economically related to the Mediterranean zone may be admitted to the European Association for Animal Production in the same way and under the same conditions as those in the European countries.

The Sixth International Congress of Animal Husbandry held in July, 1952, at Copenhagen was valuable from more than one point of view. While the cynical may say that we suffer from too many conferences the fact remains that we have now entered a period where co-operation of one kind or another between European countries will almost certainly increase. This being the case it is as important that we should find the best way to make international conferences more efficient as it is to listen to papers and discussions arranged at them.

Since 1948 the Animal Breeding Research Organisation has been collecting twin cattle in the West Midlands of England. The dairy cattle population here is dense—an important factor in reducing cost of collection. Propaganda was issued in various forms all directed at getting in touch with farmers owning one-egg twins, i.e. twins originating from the splitting of a single fertilised egg as distinct from two-egg twins coming from two fertilised eggs. As the twinning rate in cattle is only 1-2% of all births, and probably only about 1 in 20 of these twins are one-egg, their purchase and collection under British conditions is rather costly. Up to the end of 1952, 103 pairs of one-egg heifers twins had been collected.

There has been a rapid expansion of pig research at the Rowett Institute during the last two years, and the object of this paper is to give some idea of our facilities, the kind of work we are doing, and a few of our recent findings.

We are now able to feed individually up to 206 growing pigs at any one time, but only rarely will more than 150 be fed individually whilst about the same number will be fed in groups.

Our permanent fattening house has four farrowing pens which are at the moment being used for baby pig experiments. It has three pens in which 36 pigs are individually fed and four pens somewhat similar to those used by the late Mr. McGuckian in Ireland. These house eight groups of seven pigs, which can, if we wish, be individually fed in a ‘ dining room ’ containing sixteen individual feeding compartments.

The progress in animal improvement depends on the accuracy with which the breeding value of each individual in the breed, or herd, is estimated, and how the animals chosen on the basis of our estimates are combined in matings. We are concerned here only with the first part of the problem, i.e. the estimation of breeding values. The estimates are made in regard to certain characters, or traits, which are of particular interest from an economic point of view, and they may be based on the phenotypic merit of the individual, or on the merits of its ancestors or collateral relatives, or on the merits of its progeny, in regard to the character in question. Often a combination of two, or three, or all four methods may be used. Their relative importance depends on the heritability of the character, as will be discussed later.

During the early stages of investigations concerned with the dietary requirement of dairy calves for certain amino-acids (Blaxter & Wood, 1952a), we had occasion to devise rations simulating milk to meet the calves’ basic requirements. These consisted of reconstituted dried skim-milk powder, glucose, trace elements, lard as a source of fat and a concentrated solution of vitamins A and D in arachis oil. The diet was comparatively cheap and the growth of the calves which were given it appeared quite satisfactory, at least for the first month. Then, quite suddenly, some animals developed alarming symptoms of muscular and cardiac derangement and some died. Examination of the calves at post mortem showed the presence of muscular degeneration which appeared comparable to a similar type of degeneration which had been observed in guinea-pigs and rabbits given rations low in vitamin E content (Goettsch & Pappenheimer, 1931). The ration which we had been giving to the calves contained only a few milligrams of vitamin E, since experiments in America had suggested that E deficiency in cattle took several years to produce (Gullickson & Calverley, 1946).

During the last decade or more we have heard a great deal about progeny testing. Discussion has centred round three chief points. Under what conditions can selection by progeny testing lead to an increase in the rate of genetic improvement ? What method of testing and interpretation of results is most efficient and most practical ? How should the results be applied—that is in what way should the tested animals be used ?

In their paper reprinted herein (page 79) Johansson and Robertson have shown to what extent modern genetical theory can answer the second of these questions. It now remains for the executive agencies of livestock improvement to demonstrate the practical utility of the schemes they outline. We must wait some time, especially for slow-breeding animals like cattle, before the results of such a demonstration are available.