Calculations based on conventional feeding standards suggest that cows grazing well-managed pasture are frequently consuming excessive quantities of protein in relation to their requirements and to the starch equivalent consumed. They also suggest that milk production from potentially high-yielding cows is limited primarily by the supply of dietary energy. This paper describes two experiments on the effects of low-protein supplements on the performance of grazing dairy cows and reports the main results on yield and composition of milk and herbage consumption. Full details and results, and some other aspects of the experiments, are being reported elsewhere.

It is now widely accepted that the subcutaneous implantation of stilboestrol or hexoestrol increases the rate of live-weight gain in lambs and cattle. In sheep it is generally considered that for a feeding period of up to 12 weeks a single implantation of hormone produces an adequate growth response. Perry et al.(1951), Stephens & Thompson (1952) and Bell et al.(1954) reported no advantage from repeated implantations during the experimental period. In a series of experiments at this Institute (Preston & Gee, 1957a) it has been noticed that the major part of the increased weight gain takes place during the first six weeks after hexoestrol implantation.

The past few years have seen the development in Great Britain of the ‘contemporary comparison’ method for evaluating progeny tests of dairy sires (Macarthur, 1954; Robertson, Stewart and Ashton 1956). The final overall figure attached to a sire is the mean difference between the yield of his daughters and that of other heifers milking in the same herd in the same year, with due regard for the numbers of animals in the two groups. Although it has some imperfections in special cases, this is probably the most informative simple method of evaluating a sire for yield and, fortunately, one which could be easily integrated with the existing recording system. The method has been turned into a simple routine in the Bureau of Records of the Milk Marketing Board and several thousand bulls have now been evaluated. In this paper, we shall be mostly concerned to use this material to investigate the heritabilities of milk yield and fat content and the relationship between the two in the different breeds. The information that we shall use consists, for each bull, of the mean contemporary comparison, with its effective ‘weight’, and the average fat percentage of the daughters. Before we deal with the observed results, we should go into rather more detail into the nature of these two figures and into the factors affecting them.

A number of metabolism crates for the separate collection of faeces and urine from sheep have been described by various workers. These fall into two main categories, collection of excreta by bag and funnel of the pattern described by Raymond, Harris and Harker (1953), and separation without harness by the use of wire screens which deflect the faeces into a container and permit the urine to flow through a metal funnel into a collection bottle. Bratzler (1951) has described in detail a metabolism crate of this latter type which has the advantage that it can be used for sheep of either sex.

The successful outcome of early weaning and dry feeding of calves would appear to depend upon, among other things, the early establishment in the calf’s rumen of a microbial association similar to that in the adult ruminant. Inoculating the rumen of such calves with’ rumen contents from older animals might be a method of hastening this development.

In an earlier experiment in this series (Preston, 1956), it was found that by substituting linseed cake meal in place of dried skimmed milk in the meal mixture caused a reduction in consumption of the mixture and adversely affected growth rate. This indicated that it might be beneficial to incorporate in the diet some form of sweetening agent.

The influence of oestradiol, and of synthetic substitutes for the natural hormones such as stilboestrol and hexoestrol, on growth and fattening in livestock has been investigated by many workers. In particular the emphasis given to work at Iowa State College (Burroughs et al., 1955), led to a very rapid and widespread adoption of the technique of oral administration to fattening beef animals in the U.S.A., and to a resurgence of interest in techniques of administration in other countries. Workers in Great Britain have investigated the results of administration of oestrogens, both orally and by implantation, in beef cattle, sheep, pigs and poultry.

During the past decade investigations have been in progress, first at Drayton, nr. Stratford-on-Avon, and later at Hurley, into the production and utilisation of winter grass. Over the period 1951-4, overwintering methods were compared for 2-year-old store cattle (Hughes et al.,1955). These cattle were destined to be fattened on summer grass, but with the change in emphasis in market conditions whereby an animal of 9 to 10 cwt. giving a carcass of about 600-650 lb. is required, it is desirable that cattle approaching 2 years old at the beginning of the winter should where possible be fattened and not maintained in store condition. On most farms there is insufficient yard space for both young and older animals, also on dairy farms winter grass would be a valuable feed if it could be used for wintering growing heifers.

For these reasons it was decided to investigate the possibilities of using winter grass for overwintering cattle beginning the winter at 1 year old or younger. Two experiments were carried out with Hereford colour-marked steers during the winters of 1954-5 and 1955-6.

An objective measure of conformation is desirable in the study of fatstock nutrition and genetics. Conformation of the beef carcass can be defined as the proportions of joints of different tissue composition, food value and meat quality. While these can be judged by eye and measurement both in the live animal and the carcass, the most accurate and objective measure of conformation would be obtained by weighing joints of known quality. To use for this purpose the butcher’s separation of the carcass into wholesale joints, the London and Home Counties cutting system was applied to forty bullocks from experiments at the Grassland Research Institute in 1955 and 1956.

Many thousands of cast-for-age Blackface ewes in Scotland and England are transferred each year to lower ground after producing four or five lamb crops on their native hill farms. It is then customary to use on them rams of another breed, often the Border Leicester, with a view to the production of more profitable lambs than can be obtained from pure-breeding (Bywater, 1945). Such is the scale on which this procedure is practised that it becomes an important consideration in any breeding plan for hill sheep that the cast ewes should be adapted to this phase of their careers as well as to that which precedes it on the hills. The outcome of selection work with Blackface sheep consequently cannot be fully assessed until the cast ewes have reared crossbred lambs, and have been finally disposed of.

It is difficult for the visitor to New Zealand to realise that practically all of the five million acres of pasture land now devoted to dairying was, a matter of seventy years ago, dense rain-forest, scrubland or undrained swamp. Practically the whole of the Manawatu and Taranaki and large portions of the Waikato and North Auckland, which are the principal dairying districts today, were in forest when the introduction of refrigerated ocean transport in 1882 made possible the development of New Zealand’s dairy industry.

The first step in bringing in forest was the felling of giant trees such as rimu, matai and totara and the undergrowth of smaller trees and vines. Sometimes the bigger timber trees were milled, but too often they were merely felled and the fire-stick was applied to leave an indescribable mess of partially burned trunks and stumps.

New Zealand is primarily an agricultural country. Sixty per cent of all its production, including nearly 100% of its exports, comes from farms and is produced by only 17% of the total labour force. Within the agricultural industry sheep farming is dominant. Wool provides between one-third and one-half of the total exports and lamb and mutton about one-sixth. Over 90% of the wool and lamb produced and about 50% of the mutton is exported.

The prominent place that wool occupies in New Zealand’s farming strikes any visitor from Britain. The wool cheque naturally exceeds the income from other sources on the sheep stations of the Southern Alps where Merino sheep are grazed, but on lower hill farms selling cast-for-age or surplus two-tooth ewes to fat-lamb breeding farms and store lambs to hogget fatteners the wool cheque is still usually more than half the income.