The methods which we use in this country to calculate the rations for our livestock are based on studies made in Germany during the period 1890-1909, and in America at about the same time. These methods have been amended from time to time as the results of other studies have accrued, but, in the main, their basis lies in a few dozen experiments made by Kellner and Kuhn at Leipzig with steers and a very much smaller number made with milking cows. This basic information, expanded in many respects and certainly extrapolated well beyond its admittedly limited experimental foundation, is collected in two sets of tables in the books dealing with the feeding of livestock. One gives the requirements of different classes of stock in terms of energy values and the other gives the energy value of the common feeding stuffs.

The variations in the incidence of mastitis and infection with stage in lactation of dairy cattle have been the subject of a number of investigations (Oliver, 1955) but until recent years the udder health of dry cows has been given little attention. This is surprising, because many cows are dry for almost three months in each year and the dry period is immediately followed by a few weeks when the incidence of mastitis is high (Oliver et al .,1956a).

During the last ten years a study has been made at this Institute of the importance of the dry period to the control of mastitis in dairy cattle. The object of this article is to review the progress made.

In the Proceedings of this Society two years ago, A. T. G. Macarthur (1954) presented a method for the evaluation of dairy sires under farm conditions. Since that time, considerable use has been made of this technique in the Bureau of Records of the Milk Marketing Board and in this paper we propose to discuss the method critically, in the light of the results obtained on over 1,500 bulls.

As the experience we have gained has considerable bearing on the validity of this method, it would perhaps be valuable at the beginning to view the general problem of testing dairy bulls under British conditions. What evidence have we that the use of contemporary comparisons is the best tool that we have available for the assessment of dairy bulls? We must bear in mind here that we have two distinct problems. The first is the assessment of bulls used in A.I. whose daughters have been bred and milked in many herds. The second is the assessment of bulls used in natural service.

The ingenious biochemical system, which we generally call heredity, directs the body development and regulates the reaction of the individual in relation to the environmental conditions. It is this genetically determined adaptiveness of the individual which makes it possible for organic life to survive even when the climatic conditions and the supply of nutriment vary within wide limits in nature.

The interaction of heredity and environment involves several problems of vital importance for animal production. One such problem is the influence of level of nutrition during the rearing period on body development, fertility, milk production and longevity. When investigating the relative importance of heredity and various environmental factors on the production traits in dairy cattle, we have concentrated much of our effort on this special problem.

To wean calves early and then feed them dry meal, hay and water is thought to have a number of advantages over more conventional methods of calf rearing. These advantages include: a considerable saving of milk or milk substitutes, an early build-up of the microbial population of the rumen (thus permitting the use of simple inexpensive foods), and the saving of labour concomitant with early weaning.

Accordingly, a number of small experiments were set up to test the practicability of early weaning, the effect of different dry feeds and of a variety of types of flooring for calf pens.

It is generally recognised that spring grass does not provide a balanced ration for the grazing animal, since it contains excess of nitrogenous substances in relation to carbohydrate. Young lucerne similarly contains more nitrogen than is necessary to provide a balanced feed. When grazing these types of herbage, the animal wastes much of the ingested nitrogen. If the ration included carbohydrate rich foods in addition to the high quality herbage, the animal might be able to utilise more of the nitrogen it is consuming.

In this country little experimental evidence is available on the use of carbohydrate supplements for beef cattle, although several firms produce high carbohydrate cakes with low fibre content, for feeding in conjunction with young succulent grass.

The growth of grass varies considerably from month to month. Where stock numbers are constant, as in a dairy herd, it is difficult to use grassland efficiently by grazing alone. But where grassland is used for meat production, livestock numbers may be subject to a considerable fluctuation, and with skilful adjustment of classes of stock this fluctuation can be made to approximate to the seasonal pattern of growth in the pasture.

The adjustment of stock numbers to the quantity of grass present is an art which is part of successful grazing management. Understocking will lead to an accumulation of pasture which will then have to be grazed at a more mature stage, while overstocking will result in a lower plane of nutrition for the animals. The efficiency of equating stocking intensity to the pasture available in a given period will be reflected in the progress of the individual animal (in terms of daily milk yield or live-weight gain) and in the output per acre of pasture.

The objects of this investigation were to discover the amount of current inbreeding, the extent of any genetic divergence between the beef and dairy types, and whether the breed was dominated by an élite group of herds as for example, in the British Friesian (Robertson, 1953). An extensive investigation by Sewall Wright (1923a), (1923b) and McPhee and Wright (1925), (1926) established that there was at that time little current inbreeding and that genetic divergence between Dairy and Beef Shorthorns was negligible. This work adds to and corroborates their findings and throws some light on breed structure.

The sampling technique in this investigation is based upon Wright (1925). If consisted of noting the number, parents, grandparents and great-grandparents of a randomly selected sample of 128 females registered in Coates’ Herd Book, Vol. 94, 1948. Simple random lines were traced back from each great-grandparent as far as 1900, a toss of a coin deciding whether to record a sire or a dam. The information contained in Coates’ Herd Book made it a simple matter to record in addition the mate of the randomly selected ancestor, thus providing 16 random lines behind the eight great-grandparents.

A Number of authors (Bonsma and Neser, 1951; Bisschop, 1954; Wiener and Donald, 1955) have recently provided experimental evidence on the age at which the eruption of permanent incisors occurs in cattle and, in view of the wide ranges generally encountered, criticised the practice of estimating age from dental development. Though factors such as individuality, breed, plane of nutrition and type of grazing are frequently quoted as being responsible for deviations from the ‘accepted’ means (Miller and Robertson, 1952; Zorn, 1953), apparently little support is to be found in the scientific literature on the subject.