There have been many attempts to use the measurement of cell wall fractions to predict the digestibility in vivo of untreated and alkali treated straws (see far example Sundstøl et al, 1978; Reid and Ørskov, 1987). All these attempts have shown this approach to have very low predictive ability for straws. Accordingly extensive use has been made of digestibility measurements in vitro using either rumen fluid (eg Sundstøl et al, 1978) or cellulase type enzymes (eg Jewell et al, 1986).

Whilst in vitro methods appear to be useful predictors of digestibility in straws, they are slow and relatively expensive. The work reported here has compared their predictive power with that of near infra-red reflectance spectroscopy (NIR).

A total of 123 cereal straws were used. These included 54 wheat, 43 barley and 4 oat straws all untreated and the 9 wheat, 9 barley and 4 oat straws oven-treated with ammonia previously described by Mason et al (1988).

Reference is first made to antibiotics and relates to the use of low, sub-therapeutic levels of such products given daily in the feed over long periods of time. EEC legislation has followed UK policy in restricting their use as growth enhancers almost exclusively to those of non-therapeutic use in man. In their role as growth enhancers their inclusion in the feed results in increases in liveweight gain and/or feed conversion efficiency and thus increase the efficiency of production. In the EEC it has been calculated that the benefit of using growth promoting antibiotics saved the equivalent at 1982 prices of 480 x 10 e.c.u. There would be some additional benefit from reduced incidence of disease in certain cases. Since the early 1950's, when antibiotics were first introduced as growth enhancers, to the present time there have been numerous scientific publications concerning their efficacy. Thus, from experiments involving many thousands of poultry and of pigs the following values have been given relating to percentage weight gain in poultry and pigs respectively 5.0 ± 0.6 and 6.5 ± 0.5; corresponding values for increase in feed conversion efficiency are 3.5 ± 0.4 and 4.1 ± 0.04; all four values quoted are percentage increases over controls. Relating to ruminants, use of monensin, an ionphore antibiotic at levels of 25-33mg kg-1 feed in 35 trials, resulted in increases over controls in weight gain and feed conversion efficiency of 5.2% and 8.65% respectively.

The factors that affect output in animal production systems are growth rate, feed conversion efficiency (FCE), carcass conformation, muscle and fat content, and kill out percentage. These factors are affected by genetic potential, provision of optimal nutrition and environmental conditions to disease free animals. In addition, certain exogenous chemicals are known to affect animal performance, and these can be classified as follows:

• i)use of chemical messengers which bind to specific receptors in target tissue

• ii)use of anti-microbial compounds which alter the microflora in the gastro-intestinal tract and thereby improve performance.

This paper will deal specifically with the use of beta adrenergic agonists and growth hormone (GH) which are currently being researched.

Quality can be described under various headings. Deficiencies in muscle colour and structure lead in the extreme to pale, soft, exudative (PSE) or dark, firm, dry (DFO) meat. Intramuscular fat content (marbling) may be important but this varies between species. Eating quality relates to three major components. Texture is most important, followed by juiciness and flavour intensity. Flavour becomes more important when associated with unusual or ‘off’ odours.

The conversion of muscle to meat is accompanied by two major changes, the onset and resolution of rigor mortis and acidification of the tissue. Both the rate and extent of acidification may vary. If the rate is rapid, so that the pH reaches a low value when the temperature of the carcass is still high, PSE meat can result. The rate of acidification is largely determined by the degree of muscle stimulation immediately before and at slaughter.

The growth and manner of the use of the five hormone products in the European Community will be reviewed.

The circumstances leading to the decision by the European Council to ban the use of steroid hormones in beef production will be discussed. This will include reference to the Lamming report and to the attempts by the UK government and the Agro-chemical industry to have the decision reversed.

The coat of the cashmere goat consists of two types of fibre, a coarse outer coat of guard hair produced by the primary skin follicles and a fine undercoat of cashmere (˂18.5 microns diameter) produced by the secondary follicles. In the spring both the primary and secondary follicles shed their fibres and a sparse coat of mainly guard hair is maintained over the summer. Many temperate mammalian species display photoperiodically regulated changes in the pelage which alter the insulating properties of the coat and prepare the animal for large variations in ambient temperature. The timing of the moult can be manipulated by changes in photoperiod (Allain et al, 1986) or treatment with melatonin or prolactin. Smith et al (1987) demonstrated that melatonin treatment from August in the male Blue-fox prevented both the onset of the moult and the spring rise in prolactin. In the Djungarian hamster prolactin treatment induced the spring moult and the suppression of prolactin by bromoergocriptine inhibited the moult (Duncan and Goldman, 1984).

Winter clipping of breeding ewes has given variable increases in lamb birth weight associated mainly with increased ewe voluntary food intake (Rutter, Laird and Broadbent, 1972; Vipond, King, Inglis and Hunter, 1987). The requirement for energy is greatest during the last six weeks of pregnancy but increasing uterine occupation of rumen volume may limit the ewe's ability to increase intake after clipping in late pregnancy. The additional influence of forage quality on intake after clipping is not clear. The present experiment was designed to study the independent and interacting effects of clipping regime and silage quality on lambing performance.

Sixty Greyface ewes of uniform age were individually penned 14 weeks before lambing. Precision chop silage offered ad libitum was either early cut [188.3 g dry matter (DM)/kg, 155.7 g crude protein (CP)/kg DM, 740 g digestible organic matter (DOM)/kg DM] or late cut (184.5 g DM/kg, 100.9 g CP/kg DM, 689 g DOM/kg DM). For all treatments concentrate feeding was introduced 7 weeks before lambing, on an increasing scale to provide a total of 21 kg/ewe. Silage type was factorially arranged with 6 clipping regimes.

It has been shown that giving mule ewes a soluble glass bolus which contained 150 rag melatonin on 2 July, advanced the onset of the oestrus cycle. This experiment was designed to investigate whether the dose rate of melatonin could be reduced.

• 1.40 ewes not treated (control).

• 2.40 ewes given glass bolus containing 150 mg melatonin.

• 3.40 ewes given glass bolus containing 100 mg melatonin.

120 mule ewes (Blue-faced Leicester x Swaledale) aged between 4 and 6 years all of proven breeding ability were divided into 3 similar groups by age, weight and body condition on 2 July. One group was left untreated and 2 groups received a polymer-bonded soluble phosphate glass bolus (Pilkingtons P.L.C.) which contained the appropriate level of melatonin (Sigma Chemicals Corporation). Each bolus was cylyndrical in shape measuring 1.8 cm in diameter and 3.0 cm in length. Tho average mass and specific gravity of boluses were 23 g and and 3.0 respectively.

Early lamb production is a specialist enterprise in which profitability is highly dependent on getting all the lambs sold while prices are still high in Spring when lamb is in short supply. This involves lambing in late December/early January. Hence ewes must be mated in August. Conventionally in the UK, this has been achieved by the use of progesterone-impregnated sponges and pregnant mare's serum gonadotropin (PMSG). The ram effect is a powerful technique for the control of sheep reproduction. The objective of the present study was to reinvestigate the value of teasers for the stimulation of seasonal activity in the ewe.

125 (2-3 yr) Mule ewes (Blue-faced Leicester x Swaledale or Blackface), isolated from rams for two months, were used to investigate the effect of different durations of teasing on the stimulation of seasonal activity. Groups of 25 ewes were exposed to either teaser vasectomised rams and teaser ovariectomised ewes (induced into behavioural oestrus by an intramuscular injection of 0.2 mg of oestradiol benzoate) for 1 month (group l), 3 weeks (group 2) and 2 weeks (group 3); or vasectomised rams only for 2 weeks (group4); or left untreated (group 5). At the imposition of treatments, groups were isolated from each other and from contact with other 3heep by a distance of at least 1 km. Plasma progesterone was measured twice weekly on 8 animals, per group to determine ovarian activity.

Supplementation of finishing lambs fed swedes in situ has been traditionally achieved with cereals or 14% CP compound feeds. Crowing of winter cereals has reduced the availability of protein-rich grass runbacks and on most farms where lambs are consuming mainly swede bulbs there is likely to be a daily deficit of RDP of around 16 g RDP/day (0.15 of total requirement). Recent MLURI work (Milne pers comm) indicates that the normal RDP:ME ratio of ruminant diets of 7.8:1 may be inadequate in the unusual conditions of high rumen turnover rates and rapid fermentation associated with root feeding. Rowett feed evaluation work indicates higher ME values for swedes than previous estimates increasing energy:protein imbalance.

This trial had two objectives; to study response to supplementation of swedes with soya bean meal compared to barley and to study whether holding lambs for 3 months inside on a straw based diet prior to finishing was an effective alternative to holding lambs on autumn grass outside. The potential advantages of this alternative are reduced competition for autumn grass between breeding ewes and finishing stock and better utilisation of sheep housing and arable by-products.

The first objective of this trial was to evaluate swedes of different dry matter content developed by the Scottish Crop Research Institute in particular to determine whether dry matter content and related hardness were appropriate for the grazing situation. The second objective was to study the performance of Highland Mule wether lambs (Bluefaced Leicester x Blackface) (BFLX) compared to Suffolk x Blackface (SX) and Cheviot (C) wether lambs. The Highland Mule wether lamb is a by-product in the production of Highland Mule ewe lambs for breeding and the specific interest was in whether there was any deleterious effect on finishing performance associated with the Bluefaced Leicester sire.

Representative lambs of the genotypes involved were purchased in September and run on grass and stubbles until the start of the swede feeding period (2 November) with the aim of maintaining liveweight. Liveweight was 33, 33 and 36 kg for BFLX, S and C respectively on 2 November. Adjacent plots of the swede varieties Dryden (D), Melfort (M) and Doon Major (DO) were grown in one field (two replicates) and 33 lambs of each genotype grouped and allocated to each variety.

The ARC (1980) energy system sees growth in the single dimension of energy retention (ER) which increases, with diminishing marginal efficiency, as ME intake increases. The quantitative relationship between ME intake and ER is predicted from q, the proportion of the gross energy which is metabolisable. An experiment on growing sheep on controlled feeding of different feeds was carried out to provide data suitable for testing ARC (1980) and other energy systems.

Scottish Blackface wether sheep in single pens, entered the experiment at 25 kg liveweight (LW), when 11 were slaughtered. The remainder were allocated to 3 x 3 x 3 treatments with an intended 4 replicates per treatment. The factors were (i) feeds: feeds B, U and M shown in Table 1, (ii) levels of feeding. L, M and H where H was 936 g/d at 25 kg and was increased by 52 g/d each week, L was half H and M half-way between L and H, (iii) slaughter point, after 9 or 18 weeks, or at 40 kg liveweight.

The physical limitation of rumen capacity frequently restricts forage intake of ruminants to be within that needed to achieve their nutrient requirements for maintenance and production. It has been observed that, in some circumstances, supplementation can enhance the intake of forages, particularly those of low digestibility, while forage intake will reduce at high levels of supplementation, but in ways which are difficult to predict (Weston, 1982).

In a previous trial it was observed that in sheep with an adequate supply of protein, barley supplements caused a decline in hay intake equivalent to 1:1 on a dry matter basis (Eayres el al, 1988). The present study was designed to investigate further the influence of barley and protein supplements on the intakes of hay and straw by sheep.

Thirty two wether sheep (12 months old; Greyface) were placed in individual pens with wire floors and offered chopped hay ad libitum for 21 days in order to allow adaptation to the pens and to a forage based diet.

Muscle: bone ratio is a term commonly used in studies of growth and meat production. It is perceived to affect carcass value (Kempster et al., 1982) even though it is positively correlated with the fat: muscle ratio. Both ratios increase during post-natal growth but the literature is lacking in a detailed description of how this occurs.

Bone and muscle are closely related due to their roles in movement. Much evidence exists to support the hypothesis of Hooper (1978) that bone is the “pacemaker” for muscle growth. Certainly, muscle appears to display a more passive role in growth, responding to changes in length or loading by altering its length and diameter (eg. Holly et al., 1980; Sivachelvan and Davies, 1986), while bone growth in length is progressive and finite, appearing to follow a genetically determined plan. Thus the fundamental importance of bone to growth of muscle cannot be over-emphasized.

Relatively greater increases in diameter than in length occur during post-natal growth of bone and muscle. The relative magnitude of these changes has been little studied due, in part, to the difficulty in definition of shape. Consequently conformation has normally been quantified subjectively or indirectly in terms of weight.

The trial reported here forms part of a long term research project at Newcastle investigating the suitability or a bacterial inoculant (Pioneer Hi-bred Int. Inc. brand 1177) for U.K. silage production. In designing the feeding experiment, note was taken of previously conducted trials with both beef animals (Hooper et al. 1988) and sheep (Hooper et al. 1984; Hooper and Armstrong, 1987). Results to date have indicated nutritional advantages to those silages prepared with the inoculant when compared to control silages produced from the same material but without any additive treatment. This response to inoculation in terms of higher apparent digestibility coefficients and higher intake levels when fed on an ad libitum level have generally been associated with quantified improvements in silage quality, though this has not always been the case. The inoculant used in this experiment though of the same bacterial composition as used previously, was applied as a liquid additive rather than in a granular formulation.

In a previous experiment outlined at last year's conference (Hyslop and Roberts, 1988), it was demonstrated that replacement of a proprietary pelleted concentrate with malt distillers grains (draff), should be limited to 15% of total dry matter intake (DMI) when draff is offered in two feeds per day. However there is little evidence to validate such a limitation when draff is used as a concentrate replacement in complete diets. This experiment examined the effect of replacing barley/soya with draff plus additional minerals in silage based complete diets.

In a cyclic changeover design experiment consisting of 4 three week periods, fifteen British Friesian cows in early lactation were offered five treatments. Cows were given ad libitum access to one of five complete diets based on grass silage (69 “D”). Draff plus additional minerals gradually replaced barley/soya at increasing rates in diets 0-4 respectively.

Of the cereals grown in the UK oats, and especially the recently developed naked oats, contain relatively large amounts of C18 fatty acids. Consistent with this, in a series of change-over type experiments substitution of oats or naked oats for barley in dairy cows’ rations reduced the proportion of saturated fatty acids and increased that of monounsaturated fatty acids in milk fat (Martin & Thomas, 1988a, b). These results indicated the inclusion of oats in cows’ diets to be a means of increasing the appeal of milk and milk products to the health-conscious consumer. The present experiment was conducted to assess the likely potential for dietary manipulation of milk fat composition using naked oats under commercial farming conditions.

Thirty-two Friesian cows and heifers were used in a continuous design feeding trial which extended from week 3 to week 18 of lactation. The animals were paired on the basis of calving date, lactation number and pre-trial milk yield and, within pairs, were allocated at random to one of two diets.

The importance of lameness in dairy cattle in UK in terms of its economic consequences and welfare considerations is well documented (Russel and others, 1982). While such epidemiological work has identified factors of importance in the aetiology of the various conditions associated with lameness it has been less successful in apportioning their relative importance, particularly for those conditions affecting the hoof. A series of experiments has been conducted at the West of Scotland College over the period 1983 to 1989 mainly investigating the relationship of nutrition and lameness. In one of these Manson and Leaver (1988) found a significant difference in the prevalence of lameness between two groups of cattle fed complete diets containing either 16.1 or 19.8% crude protein. They also found a significant increase in mean locomotion score (LS) and commented that further studies were needed to understand the dietary processes by which the hoof of the cow was predisposed to such problems.

The objective of this experiment was to investigate the influence of the type of protein source in the concentrate upon the locomotion of the cows, the incidence and prevalence of lameness and finally on hoof hardness, shape, growth and wear.

Multiple ovulation and embryo transfer techniques increase the possibility of improving the reproductive efficiency of beef cows by twinning. However, the gestation length of cows carrying twin calves is approximately 10 days shorter than cows carrying a single foetus and twin calves at birth are lighter (0.85 of controls) and growth rate to weaning is less (0.85 of controls) compared with single born calves (Dickerson and Anderson 1988). Changes in gestation length and the low birth weight of the twin calf may partly be associated with changes in the nutritional status of the dam and the increased nutrient requirement. It is important to define the nutritional requirements of twin bearing cows if twin calves are to be successfully produced and reared.

The cows were a mixture of Hereford and Charolais cross Friesian suckler cows and heifers. Animals used for the measurement of heat production were paired where possible according to parity and live weight, one member of each pair carrying a single calf and the other twins.

Due to collinearity among the independent varlates, intake prediction models based on least squares multiple regression are likely to predict poorly with independent data. In addition, the regression coefficients are sensitive to small changes in the estimation data and tend not to reflect causal relationships expected from the results of controlled experimentation. Ridge regression (Hoerl and Kennard, 1970) allows the estimation of new coefficients for the independent variables which overcome these effects of collinearity. In order to assess the usefulness of the method for Intake prediction, ordinary least squares (OLS) models, obtained using backward elimination of variables, and ridge regression models were constructed from the same data and then tested with independent data.

Estimation data consisted of results of experiments of IGAP, Hurley and Greenmount College of Agriculture in which growing cattle were individually fed grass silage ad-libitum with or without supplementary feeds. Two subsets of the estimation data were used. Subset A included 395 animals and 36 silages; subset B included 192 animals and 16 silages and was for Hurley data only.