The recent EEC Directive banning the use of anabolic agents as growth promoters in animal production in countries of the EEC and, by implication, prohibiting imports of fresh and processed meats from countries not applying a similar ban, has raised undue concern by research scientists involved in studies of the biochemistry and physiology of growth promoters. In addition to the well established growth response and improved carcass composition obtained from using anabolic agents (both naturally occurring hormones and zenobiotic compounds), there are exciting developments involving new pharmacological agents, new immunological techniques and the possibility of direct manipulation of the genome.

The importance of a high lambing percentage in early lambing flocks is well recognised as is the variability of the dose response to PMSG of early lambing ewes. It was hoped that the integration of the immunogen ovandrotone-albumin (Fecundin ® Coopers Animal Health) into such a system would give a reliable increase in ovulation rate without the danger of superovulation caused by higher doses of PMSG. Unfortunately, last year Logue, Gill and McClelland (1986) and Keeling, King and Gunn (1986) independently reported that although Fecundin treatment in early lambing flocks (using progestagen sponges with and without PMSG)gave an increased litter size over controls there was a considerable reduction infertility which negated this advantage. These groups employed a regime of a sensitising injection, a boosting injection 28-30 days later, and ram introduction to an induced oestrus after a further 28 days(i.e. a Boost Tupping Interval (BTI) of 28 days) for the second group and 35 days for the first.

Seasonal changes in daylength (photoperiod) are effectively monitored by the eye transmitting a neural signal to the pineal gland which responds by secreting a hormone, melatonin, during the hours of darkness. Decreasing daylength is accompanied by an increase in the duration of melatonin secretion and stimulates breeding activity in sheep.

It has been demonstrated that both timed (afternoon feeding and injection) and continuous (subcutaneous and vaginal implant) administration of supplementary melatonin to ewes in mid-summer mimics the effect of short or decreasing photoperiod and can advance the onset of breeding activity. Such treatments can also increase relative fecundity at early mating by phase-advancing the mid-breeding season peak in ovulation rate. As the U.K. is not sufficient in lamb production and bearing in mind the economic pressure for early lamb marketing, effective melatonin treatment offers considerable potential for commercial application.

Compared with other species of farm livestock the reproductive performance of beef cows is poor. Mating and calving periods are frequently extended to avoid having a large proportion of barren Cows. vs. For example the ‘average’ MLC recorded herd has a calving period of over 4months. This makes management of beef cow herds difficult and has a deleterious effect on biological efficiency and profitability.

One of the major limitations to improvement of reproductive efficiency in beef cattle is the extended post-partum anoestrus. Beef cows have longer post-partum anoestrous periods than dairy cows. In one study of three different herds (Peters and Riley, 1982) the mean length of the anovulatory period ranged from 24 to 88 days.

The widespread use of artificial insemination (AI) in the United Kingdom sheep industry has been limited by the poor conception rates obtained after cervical insemination of frozen-thawed semen. The major problem in this respect is the impairment of sperm transport through the cervix, particularly when AI is used in conjunction with oestrus synchronisation.

Previous studies (Killeen and Caffery, 1982; Maxwell, 1984) have indicated that a laparo-scopic technique for intrauterine insemination in ewes may overcome such limitations. At the moment, however, sufficient data on the optimum time of insemination and sperm doses required to maximise fertility in British breeds are not available. The present study was conducted to establish the optimum time of intrauterine insemination using frozen-thawed semen.

The development of an efficient laboratory procedure which would enable cattle ovarian oocytes to be matured in vitro, fertilized and cultured in vitro to the blastocyst stage of development could have important practical and scientific implications. The commercial exploitation of certain embryo transfer techniques applicable in cattle (eg., twinning by embryo transfer) might be facilitated by the development of such a procedure and there would be many advantages to having a cheap source of embryos available for research purposes. The present report deals with some of the studies recently carried out in this laboratory aimed at utilising follicular oocytes recovered from the ovaries of cattle slaughtered for beef at the abattoir. Such studies have been undertaken over a period of almost twenty years, starting with the work of Sreenan (1968)* but it now realised that the oocytes of farm mammals are incapable of normal development until after the completion of complex changes during maturation.

Buffer-feeding of grazing dairy cows, by allowing cows access to forage for a few hours each day, has been widely advocated as a means of maintaining high animal performance whilst enabling efficient sward utilization. However, in practice, responses to buffer-feeding with January/February calving cows have been extremely variable. The objective of this study was to examine if part of the variability in response could be explained by differences in the level of nutrition during the winter feed period.

Lameness in dairy cows has both important animal welfare and economic implications. High concentrate to silage ratios may be an important predisposing factor, whilst trimming has been advocated as an effective preventative measure. This trial examined the effects of these two factors on locomotion, incidence of lameness and hoof measurements.

The “low milk fat” syndrome and “off feed” problems have long been associated with the use of rations incorporting a high proportion of starch based concentrate. These problems can be ameliorated by frequent feeding of concentrate, the use of out of parlour feeders or complete diets. Another approach has been to examine alternatives to cereal starch as the major energy source for concentrate supplements. Since few comparisons of concentrates containing a mixture of high quality fibre sources have been reported, the present trial was designed to compare concentrates based on cereal starch with those containing a mixture of high quality fibre sources when given with ad libitum grass silage from calving. An additional aim was to compare individual feeding through Calan Broadbent gates with groups fed forage at a self-feed clamp.

In a previous experiment it was found that when concentrates were given in large amounts with a fixed ration of hay, cows receiving starchy concentrates gave more milk but with a lower fat concentration than cows receiving the same amount of high quality fibrous concentrates of a similar metabolisable energy (ME) concentration. The purpose of the present experiment was to examine the effects of varying the starch:fibre ratio of the concentrates on milk yield and composition and on hay intake.

Sixty-one Friesian cows in their second or later lactation were given a standard ration for the first two weeks of lactation and were then allocated to one of eight experimental treatments for the following 18 weeks. All the cows were given 13.5 kg/d of one of four concentrates of similar crude protein and estimated ME concentrations. The concentrates varied from high starch (S) based on barley, wheat and cassava to high fibre (F) based on high-quality by-products (citrus pulp, molassed sugar beet pulp and wheatfeed) with two intermediate types (SF and FS).

The introduction of milk quotas has resulted in a trend towards minimising the costs of producing each unit of milk output. The first step in achieving this is through increased forage use and minimising the input of high cost supplementary feeds, an approach widely adopted at present. Further reductions in costs can be achieved if the cost per unit of supplementary feed can be reduced. One such approach is through replacing conventional dairy concentrates, either conventional purchased dairy rations or home mixed barley/soya bean rations, by single feeds which require no mixing or processing prior to feeding to the animals. Maize gluten feed offers potential in this area but although data on its energy and protein values are known there is little direct information available on its value when offered, especially as the sole supplement, to lactating cows. The present study was set up to compare the values for lactating cows of maize gluten feed, either offered as the sole or part of the supplement, with that of more conventional purchased concentrate or a barley/soya bean ration of similar crude protein content.

Mixed swards of perennial ryegrass (Lolium perenne cv. S23) and white clover (Trifolium repens cv. Huia) were maintained at sward surface heights (SSH) of 3 (GC3), 6 (GC6) and 9 cm (GC9) by continuous variable stocking to examine effects on sward and animal performance. In addition, a pure grass sward of S23 was kept at 6 cm (G6) and fertilized with 14 applications of 30 kg N per ha at fortnightly intervals, beginning on 25 March. The swards were sown in August 1983, cut twice in 1984, in May and June, and then grazed thereafter. Fertilizer was applied to the seedbed at 40 kg N per ha, 20 kg P205 per ha and 20 kg K20 per ha. In March 1984 and 1985, 20 kg per ha each of P205 and K2O were applied to all plots.

Dry sheep grazed the paddocks (0.69 ha) to the required SSH's with grazing starting on 4 April, 9 April, 12 April and 24 April for treatments GC3, G6, GC6 and GC9, respectively. On 24 April, two days after lambing, core groups of 8 Scottish Halfbred ewes with twin lambs were put on the plots. Additional ewes, kept on swards similar to the treatment areas, were used to adjust the stocking rate to maintain the SSH's. These were measured three times each week with 200 readings per plot.

Experiments designed to test animal responses to sward manipulation suggest that ewe performance and lamb growth are positively related to herbage mass and thus sward height (1,2,3,). From this component research, it is suggested that to maximise herbage production and animal performance during the main grazing season, sward heights should be maintained within the range of 4 to 6 cm; herbage mass should not exceed 1600 kg DM/ha (4,2). This trial was set up to test the efficacy and sensitivity of this approach in a set-stocked, grass lamb finishing system.

During the early grazing season, when a high proportion of the lambs nutrient requirements are supplied by milk, high rates of growth can be achieved by sward management which maintains a constant surface height (3-5.5 cm) (Maxwell, Lloyd and Dickson, 1985). In late lactation, increasing herbage Intake rarely compensates for reduced milk supply and lamb growth rates are commonly lower than could be achieved with concentrate diets (Doney et al, 1984; Lloyd et al 1987). Lamb growth in this period may be related to increase or decrease of sward height (Alcock, Clark and Harvey, 1986; Maxwell, Lloyd and Dickson, 1985) or to changes in herbage growth rate (Doney, Smith, Sim and White, 1986). The present study investigated the effect on daily live-weight gain (DLWG) in weaned lambs of herbage growth rate (HGR) and pattern of sward height (SH) change when varied independently.

Lamb output in terms of both reproductive performance and lamb growth during lactationof hill gimmers (18 months old at first mating) is typically well below that of their multiparous contemporaries. This paper reports an attempt to evaluate the effects of supplementary feeding during the mating period and mid-pregnancy on gimmer performance.

Three hundred and ninety three Scottish Blackface gimmers from two hirsels (flocks of sheep from contiguous areas of land) of Auchtertyre Farm in west Perthshire were split according to the following design.

Growing lambs are frequently subject to varying planes of nutrition. Knowledge of the response of lambs to the restoration of non-limiting feeding conditions following a period of feed restriction is necessary in order to determine economic systems for finishing lambs.

Thirty Blackface wether lambs (birth weight 3.8 kg s.d. 0.38 kg) were treated in two ways from birth to 25 kg live weight (LW). One half were reared by well-fed ewes at grass (treatment UR). The other lambs sucked poorly-fed ewes up to weaning at 18.2 kg LW (s.d. 1.9); thereafter R lambs were given 700 g/day of a high quality pelleted feed (F) to 25 kg LW. Feed F contained 158 g crude protein/kg dry matter (DM) and had an estimated metabolisable energy yield of 12.5 MJ/kg DM.

From 25kg LW both UR and R lambs had ad libitum access to feed F to a final LW of 45 kg unless slaughtered earlier. The feed intakes and LW of individual sheep were measured weekly. Six lambs from each treatment were slaughtered at 25 kg LW in order to assess the effect of treatment on body composition. Three lambs from each treatment were subsequently slaughtered at 35 kg, 40 kg and 45 kg LW. Weights of gut-fill and organs were recorded and the cold carcass (CC) dissected into lean, bone and fat.

Nutritive value 1n the context of this paper refers to metabolisable energy (ME) content. Silage composition and hence ME content 1s determined essentially by the composition of the ensiled crop, pre-ensiling treatments such as wilting or additive use and the conditions within the silo. Consequently the ME content of silage 1s very variable and means of predicting it are required for routine purposes.

Until 1985 the prediction of ME was based on a series of digestibility trials carried out on MAFF EHFs between 1967 and 1972. A relationship between DOMD content and modified add detergent fibre (MADF) content (Clancey and Wilson, 1966) was calculated and the assumption that ME: (MJ/kg DM)= DOMD (%) X 0.16 was made. This did not take account of the energy contribution from volatile components.

The nutritive value of compound feeds for ruminants has been classically described in terms of starch equivalent for energy and digestible crude protein for the protein fraction. Over the last ten years there has been a move to describe energy in terms of metabolisable energy and protein in terms of rumen degradable (RDP) and rumen undegradable protein (UDP). Both of these descriptions involve measurements on animals in order to derive values for individual ingredients to be used in compound feeds. The assumption is then made that these individual ingredient values are additive when the ingredients are used in the compound.

Metabolisable energy is measured in animals kept in calorimetric chambers or metabolic crates, in the latter case energy loss in the form of methane is assumed to be constant. However, data from the Rowett indicates that this is not the case, losses varying from 1.1-2.5 MJ/kg DM (Table 1). This inaccuracy can have a dramatic economic affect in feed formulation for 1MJ difference is worth £7/tonne of ingredient.

It is axiomatic that the amount of feed eaten by any animal depends on both animal and feed factors. Although there have been a great many investigations of variations of the composition of the diet on feed intake, most of the equations which are available for the prediction of intake rely on animal factors such as live weight and milk yield and on the weight of supplementary feed offered but not its composition. Were it a simple matter to use proximate analysis of forages and concentrates to predict intake then presumably more progress would have been made. The intention of this paper is to point to what achievements have been made and to highlight areas in which further research is required.

The principle of classification is that carcasses are described, using a common language which is understood by everyone trading in the market. The language relates to characteristics of commercial importance to traders but does not normally impute value, the essence being that the individual trader is able to identify the relative value of different classes for his particular business and specify price differentials (grade) accordingly. This encourages the production of carcasses more suited to market requirements.