Earlier work at this institute with calves indicated that a concentrate containing a mixture of fibre and fat allowed higher voluntary intakes than a concentrate containing barley. The objective of the current trial was to compare the immediate and residual effects on milk yield and composition of supplements containing starch or a mixture of fibre and fat.

Primary growths of perennial ryegrass were cut on 22 May and 12 June and wilted for 24 h prior to ensiling. The earlier cut material was preserved with an additive containing a mixture of formic acid, sulphuric acid and formalin at 4 l/t, whilst the later cut herbage was ensiled with formic acid at 3 l/t. A 60:40 mixture of the two silages was offered ad_ libitum with 2 pelleted supplements. Supplement Ba was a mixture of (DM basis) rolled barley (932 g/kg) and fishmeal (68 g/kg). Supplement SBP/FF consisted of unmolassed beet pulp (555 g/kg), extracted rice bran (315 g/kg), fat prills (56 g/kg) and soya bean meal (75 g/kg). Sources of protein differed in an attempt to balance RDP:UDP supply. The factorial combination of the two supplements (Ba and SBP/FF) given at two levels, 6 kg DM (L) or 12 kg DM (H), provided the 4 treatments imposed over weeks 3 to 10 of lactation on 40 British Friesian cows. During weeks 12 to 20 of lactation (Post experiment period) the cows were given an equal mixture of the two concentrates at 9 kg DM/day. Milk output was adjusted by covariance according to yield in week 2 of lactation.

A large number of studies have been carried out on the effect of level of crude protein in the concentrate supplement on cow performance. However, there is little information on the effect on milk output of different vegetable protein sources fed as a supplement to cows (on grass silage). This experiment was designed to compare the influence of 4 vegetable protein sources in the supplement, soyabean meal, groundnut meal, cottonseed meal and rapeseed meal on milk yield, intake and diet digestibility by cows in early lactation offered grass silage ad-libitum.

The basis of the proposed scheme introduced by the A.R.C. (1980) for calculating the protein requirements of ruminants is the division of the protein requirement into two parts, (1) a minimum rumen degradable protein (RDP) supply to satisfy the requirements of the rumen microflora for cell wall synthesis, (2) a minimum undegradable protein (UDP) supply (protein that passes through the rumen to the intestine) which supplements the microbial protein produced in the rumen ensuring the tissue protein requirements of the ruminant can be met. The purpose of the experiment reported here was to investigate the effects on lactation parameters of feeding early lactation cattle levels of UDP or RDP above the minimum requirements proposed by the A.R.C. (1980).

Compound feeds are frequently used at a fixed rate of 0.36kg to 0.40kg/kg milk produced, in addition to forage and other home-grown feeds. Such linear scales take no account of the curvilinear response of milk yield to concentrate feed intake, nor of the substitution effect of concentrate feed upon forage intake. In high-yielding herds, the use of fixed rate scales can result in the provision of concentrate feeds in excess of 10kg/d. An experiment was designed to evaluate whether milk yields could be maintained while reducing concentrate feed intake, and therefore placing greater reliance on forage intake, and including sugar-beet pulp as a source of highly digestible but non-starchy concentrate, and fish meal as a source of high quality undegraded dietary protein

Dairy cows mobilise fat during early lactation to meet the energy deficit produced by increasing milk yield and reduced appetite. This can result in the deposition of fat in liver, kidney, muscle and other tissues. This “fatty liver syndrome” is associated with reduced fertility and an increased susceptibility to metabolic and infectious disease. Attempts to prevent the development of fatty liver are aimed at reducing fat mobilisation by: 1) calving cows in lean condition, thus increasing appetite and 2) by encouraging high feed intakes immediately after calving by the provision of feed of high energy density on a little and often basis. A useful system in this context might be out-of-parlour concentrate dispensers

The introduction of fully controlled out-of-parlour concentrate dispensers has brought new opportunities to concentrate feeding for dairy cows. While there may be a number of possible justifications for their use on an individual farm, it is likely that their effect on milk output and efficiency of concentrate use, will be a major factor when assessing their potential use. It has been argued that their ability to not only allow accurate concentrate rationing for each individual animal, based on milk yield, but also the fact that they can increase the frequency with which readily degradable materials, such as concentrates, are fed will provide nutritional benefits which will result in improved animal performance. In contrast the simple flat rate feeding approach implies a uniform feed input to all animals irrespective of stage of lactation or milk yield and also is generally operated on no more than two or three feeds over the 24 hour period. The purpose of the present study was therefore to compare two systems of concentrate feeding involving either the use of an out-of-parlour feeder, in which concentrates were allocated according to the milk yield of the individual animal, or the flat-rate approach. In view of the possibility that there could be an interaction between feeding system and total concentrate input both systems of feeding were compared at two levels of concentrate feeding.

The traditional system of feeding concentrates according to milk yield implies that higher levels of concentrates are offered during early lactation and that animals of higher yield potential receive greater concentrate inputs than their lower yielding herd-mates. However the results from recent studies would suggest that, when forage is offered ad libitum such an approach will result in no better herd performance than a flat rate system which takes neither of these two factors into consideration. The aim of the present study was to provide further information on this topic for autumn-calving cows, by examining the effects of variations in both the pattern of concentrate allocation over the lactation and the distribution of concentrates between animals within the herd. In the present study step feeding and flat rate feeding systems were compared with each system being operated with either all animals offered similar concentrate levels per animal or alternatively animals of higher yield potential being offered greater concentrate inputs than lower yielding animals.

Two trials have compared flat rate feeding in which cows received the same amount of concentrates each day, with a step system in which higher levels were fed in early lactation. Whereas step feeding is similar to traditional methods of concentrate allocation, flat rate feeding is a recently developed system. It is practised with success on some farms and has the advantage of simplicity, since it is not necessary to separate or identify cows-for concentrate feeding.

Results of previous experiments with store lambs have shown that intake of grass silage harvested with a flail chop harvester is quite lew but can be considerably increased if harvested with a precision chop harvester, resulting in much better lamb performance. A series of experiments. (El, E2) were, therefore, carried out to determine the optimum chop length of ryegrass silage as a basic source of winter feed for finishing store lambs.

Factors affecting voluntary food intake (VFI) in ruminants are well documented and suggest that both physical and chemical factors are involved. An understanding of VFI controls is important for the formulation of economical diets to achieve maximum levels of production.

The effect of protein supply on VFI is unclear. While the need for rumen degradable protein (RDP) to maximise microbial activity and consequently VFI is clearly established ARC (1960), the effect of undegraded dietary protein (UDP) on VFI is equivocal.

Silage based diets fed to store lambs have often produced unsatisfactory growth rates. The factors affecting silage dry matter intake and the utilisation of silage by store lambs are not clearly understood.

In each of two years 1981/2 and 1982/3 spring born store lambs (initial liveweight 31 kg) were housed from October until January. Three types of silage were fed ad-libitum:-

• 1. Unwilted + additive (UN + A).

• 2. Wilted + additive (W + A).

• 3. Wilted without additive (W).

Two groups of 23 lambs were fed on each type of silage; one group without supplementation (Nil) and the other at 60 g white fishmeal per lamb per day (WFM).

Sheep production economics are dominated by the overhead costs of maintaining the ewe and it lias been suggested that breeding from ewe lambs is an important means of increasing lifetime productivity and thus flock returns. Numerous trials have shown that ewe lambs can be successfully mated providing the animals achieve a threshold bodyweight within the breeding season. There is evidence to suggest that the subsequent performance of the ewe lamb is not impaired and may even be improved providing the nutritional management is adequate to sustain foetal and maternal tissue growth in pregnancy; the rearing burden and duration of lactation is restricted. A study of commercial flock records reveals great variation in performance and many doubt the validity of the practice on the basis of management difficulties and subsequent production. This trial looks at the effect of alternative management treatments on current and subsequent performance of ewe lambs.

While the functions of many hormones controlling milk production are known, there is little information concerning the inter-relationships between different hormones and between hormones and blood metabolites. The aim of this work was to investigate milk production, endocrine status and associated nutrient partitioning throughout lactation, in Greyface ewes rearing either single or twin lambs. Experiments were performed with ewes lambing in January and April. The seasonal differences in prolactin concentrations permits investigation of the importance of differences in concentrations of this hormone in the control of nutrient partitioning and milk production.

High levels of feed and rapid growth before puberty can result in small functional mammary glands and lower milk yields in dairy heifers. One hypothesis suggests this effect may be mediated via changes in the circulating levels of certain metabolic hormones (in particular a reduction in GH), that are known to accompany high levels of food intake, and that may normally exert some mammogenic influence. Preliminary studies indicated that rapid rearing in sheep can result in similar metabolic changes, reductions in prepubertal mammary development and lower first lactation milk yields.

In high prolificacy sheep production many ewes produce more than 2 lambs. The trial reported here was designed to look at triplet rearing as a system of dealing with the extra lamb. The effects of the method on both ewe and lamb performance were recorded.

The trial involved 32 Cambridge and Suffolk x Cambridge ewes, aged 3 to 5 years, and their progenies (32 twin and 48 triplet lambs). From 8 to 36 days post partum the effect of rearing type was investigated in combination with the feeding of the ewe with a complete diet containing either 25% or 40% coarsely milled hay (table 1).

Responses in lamb birthweight to supplements of dietary protein in late pregnancy usually arise from increases in the quantity of protein reaching the abomasum and subsequently absorbed in the small intestine. This principle is now embodied in new systems for estimating the protein needs of ruminants (see for example ARC 1980) and quantitative data are now being accumulated on dietary factors that influence protein flow to the small intestine. Although dietary factors are extremely important in determining the amounts of protein that escape from the rumen undegraded, there is evidence that the physiological state of the animal, through its effect on the retention time of food in the rumen, can also influence the amount of protein reaching the abomasum. For example, Thompson, Robinson and McHattie (1978) showed that when the energy and protein intakes of ewes remained constant there was a shorter retention time of food in the rumen and more non-ammonia nitrogen reaching the abomasum in late pregnancy than in early lactation or post weaning. The present study demonstrates a similar phenomenon following shearing.

The beneficial effects of shearing housed pregnant sheep are well recognised, but most workers have allowed ad libitum access to food. This trial was set up to investigate the effects of shearing when feed intake is restricted.

In a previous study (Phillips and Leaver, 1983) grass silage was offered indoors overnight to dairy cows which were set-stocked during the day. The intakes of herbage DM were high in spring and declined thereafter, with silage DM intakes showing the reverse trend. This suggested that a single daytime stocking rate could be practised throughout the grazing season if silage was available ad libitum as a buffer feed. In this experiment, three daytime stocking rates were compared.

In a continuous design experiment lasting 24 weeks (17 April to 5 October 1983) 36 late winter calving Friesian dairy cows and heifers were housed and offered grass silage ad libitum overnight in a feeding passage. During the daytime the cows were set-stocked at 8, 10 or 12 cows/ha. Concentrates were fed at a level of 3 kg/day for weeks 1-16 and 22-24; 5 kg/day were fed for weeks 17-21.

Hodgson (1975) has shown that herbage intake of the grazing dairy cow is maximised when the daily herbage allowance on offer is equivalent to four times the amount eaten, with a rapid decline in intake when herbage allowance falls below 40g organic matter/kg liveweight/day. This relationship between herbage intake and allowance results from the increasing difficulty of prehending herbage as the sward is grazed closer to the ground. Under a rotational grazing system, the height to which grass is grazed (residual herbage height) is a useful estimate of the amount of herbage available to the grazing animal. The present study was designed to establish the relationship between residual herbage height and milk production.

The nitrogen fixing and nutritional benefits of including white clover in a pasture are well documented. However, where attempts have been made to increase herbage yield by the application of fertilizer nitrogen, only the grass component of the mixture is stimulated. The white clover is placed at a competitive disadvantage for other aspects of the environment, especially light, and is adversely affected.

In many practical grazing systems, where defoliation is continuous rather than intermittent, it might be possible to maintain the crop canopy at a level where shading is unimportant. Similarly, if modest amounts of fertilizer nitrogen are applied when clover is least likely to be affected, the adverse effects may be minimized. Thus, the objectives of this study are to examine the extent to which fertilizer nitrogen can be used to improve animal production from a grass/clover sward by increasing herbage production whilst maintaining an effective clover population.