Carcass classification essentially has two functions: to provide information on aspects of carcass value which are of importance in subsequent marketing operations, and to provide a formal basis for a producer payment system which would thus encourage the production of carcass types demanded by the trade. There are examples of characteristics which have a market value unjustified in the light of objective analytical data, carcass conformation in sheep, and particularly cattle, being a prominent example. Idealistic carcass classification schemes would convey estimates of the amount of lean meat in a carcass and of the proportions of lean and fat in different carcass parts. They would include measurements of meat quality, not only extremes such as pale, soft, exudative (PSE) or dark, firm, dry muscle, (DFD) and soft, oily fat, but also measures indicative of eating quality, particularly texture, within the range of ‘normal’ meat.

Successive UK Governments have supported the market for finished cattle by various subsidy schemes. One of these depended on making up the difference between the average market price and a predetermined guaranteed price on an individual animal basis when market prices fell below the guaranteed price. To operate this deficiency payment scheme the classes of stock eligible for payment had to be defined and their average market price calculated, and so the concept of a “certification standard” or grade evolved.

In recent years big bale silage (BBS) made in large plastic bags has become an increasingly popular method of grass conservation with one estimate (Catt, 1986) suggesting that 30% of all grass silage in the UK was conserved in this way in 1985.

In general BBS is drier than clamp silage (CS) (Butler, 1983) primarily for economic reasons related to contracters.charges for baling the reduced number of bales compared to wet silage. There are however few comparative data on concentrations of fermentation acids and it is not clear whether the fermentation characteristics of BBS are different from CS or merely a function of differences in dry matter content.

The growth rates of weaned spring born suckler calves can be poor during their first winter because of low silage intakes. Feeding high levels of supplements is expensive and the increased growth rate is largely lost with a check at turnout. The objective of this trial was to improve the winter liveweight gains of suckled calves without affecting subsequent performance at grass.

It is generally accepted that although both plane of nutrition and chemical composition of the diet can have a major effect on body composition when comparisons are made between animals of the same age, these differences are substantially reduced when comparisons are made at the same body weight (Black 1974). There is considerable emphasis being placed on the production of lean meat for human consumption, while at the same time the retail trade is pressing for heavier carcass weights. These two requirements appear incompatible given the fact that the proportion of fat in weight gain increases as the live weight of the animal increases. We suggested (Williams and Macdearmid 1985) that compensatory growth may be used as a method of controlling body composition in beef cattle since the initial phase of compensation may be characterised by rapidly increased muscle growth combined with a reduction in the initial rate of fat deposition. Reports in the literature indicate that animals compensating after a period of feed restriction tend to have a greater appetite than animals of the same weight but grown continuously. The present experiment was designed : o compare and measure appetite and nitrogen balance in beef cattle which were fed continuously or allowed to realimentate after a period of feed restriction.

Consumer resistance to overfat meat is growing because of its wastefulness and increasing concern about the probable link between fat consumption and health. Despite this, there is little evidence to indicate any material change in the fatness of British beef carcasses over the past 10 years. The average separable fat content of beef carcasses in both 1974/76 and 1984 is estimated to be 220g/kg (Kempster, Cook and Grantley-Smith, 1986).

Clenbuterol, a β adrenergic agonist has been shown to increase nitrogen retention and decrease lipid deposition in cattle, sheep, pigs, poultry and laboratory rodents. Effects on nitrogen retention occur primarily in skeletal muscle (Williams et al 1987) and results suggest that reduced protein degradation is mainly responsible for the increased N retention. Reductions in N excretion were insufficient to account for the increased N retention in muscle and we demonstrated (Williams et al 1987) that increased N retention in skeletal muscle was occurring partly as a result of a nitrogen repartitioning in the body with reduced N retention in the viscera. Growth hormone also stimulates skeletal and muscle growth furthermore the mechanism whereby growth hormone stimulates N retention was considered to act primarily via a stimulation of protein synthesis (Eismann et al 1986). It would therefore appear that clenbuterol and growth hormone both increase N retention but by different mechanisms leading to the possibility of achieving an additive effect from the use of the two compounds in combination. The present experiment was designed to study the effects of clenbuterol and growth hormone individually and in combination on the N balance, creatinine excretion, protein and lipid accretion of veal calves.

The energetic efficiency of microbial protein yield from the rumen (E) is a major element of uncertainty in systems describing the supply and utilisation of dietary protein in ruminants. The relationship between microbial growth rate and E can be described with some precision in vitro but the situation is complicated in vivo by the necessity to determine microbial outflow rate from the rumen. The Agricultural Research Council (ARC 1984) assumed a fixed value of 32g microbial N/kg DOMR (organic matter apparently digested in the rumen) or 1.34g microbial N/MJ Metabolizable Energy (1.34g MN/MJME) while recognising that there are sound theoretical reasons why the relationship might better be described by a variable function.

The proposed Agricultural Research Council (ARC 1984) protein evaluation system for ruminants provides lower nitrogen allowances than any other. (National Research Council 1985; Alderman 1987). A U.K. Interdepartmental Working Party (IDWP) was set up to consider the ARC (1980) proposals and recommend a practical protein evaluation system for ruminants for use by the advisory services. Its provisional proposals have been reported by Webster (1987). This trial was set up to provide a practical evaluation of the two systems in a commercial dairy herd.

Animals. Thirty-three Friesian cows (mean livewewight 590kg, mean previous milk yield 6120 kg), in early lactation were blocked according to (a) previous treatment, (b) number of previous lactations and (c) previous milk yield. The cows were randomly allocated within blocks to one of three dietary treatments.

Treatments. Dietary nitrogen allowances were calculated, according to (1) ARC(1984) and (2) IDWP (Webster, 1987) except that the ARC (1984) concept of essential amino acid nitrogen was included in the IDWP calculations. The difference in nitrogen allowances between the two systems was so great as to warrant a third intermediate treatment (INT), calculated to provide allowances mid-way between the other two.

There is a considerable literature on the effect of grinding and pelleting roughages on their intake and digestibility by ruminants. It is also well established that intake is correlated with digestibility, which parameters are themselves correlated with the rumen degradability of the roughages concerned (Hovell et al. (1986)). However there is little information in which the effect of processing on the intake and digestibility of roughages of known degradation characteristics has been examined. The objective of the experiment reported here was to examine the effect of grinding and pelleting on the voluntary intake and digestibility of two roughages whose degradation characteristics had been defined.

Four mature 63-69 kg Finn-Dorset ewes fitted with permanent rumen cannulae were used. The roughages were a hay (potential degradability 0.81), and a barley straw (potential degradability 0.57) given coarsely chopped, or ground and pelleted. The composition of the hay and straw is shown in Table 1, and the particle size distribution of the two forms is given in Fig. 1. Urea was added to the straw at 18 g/kg and to the hay at 3.6 g/kg (air dry), with 0.13 g sodium sulphate per g urea. A mineral/vitamin supplement was also given. The experimental design was a latin-square with 21 d periods. Food was offered to 10-15% excess of voluntary intake. Voluntary intakes and digestibility were measured during the last 7 d of each period.

ARC (1980), in its Chapter 2, gives a method for predicting the rate of feed intake of a sheep of a given weight, W, on a given feed (feed class and energy metabolisability, q). In its Chapter 3 a method is given for predicting the growth rate, GR, of a sheep of a given sex and W from its ME intake. Where GR and W are known the latter procedure can be used to predict the rate at which feed, needs to be eaten, from the ME content and q values of the feed, to support the observed GR. A third method is that of Emmans (1985), which predicts the rate of intake of a non-constraining feed with energy as the first limiting resource by a given animal in a given initial state in a thermally neutral environment; the animal is described by its mature protein weight, Pm kg, its mature lipid:protein ratio, LPRm, its Gompertz rate parameter for protein growth, B/day, and its fattening rate parameter, b, where (b + 1) is the allometric exponent for body lipid on body protein in potential growth.

The three methods were used to predict the intakes of Suffolk rams and the predictions compared with the intakes observed in an experiment.

The data were from 66 Suffolk rams born in mid-January, weaned at 8 weeks into single pens and given free and continuous access to the feed shown in Table 1. Their intakes and weights were recorded for successive periods of 2, 2, 2, 2, and 3 weeks from 20th March. The sheep were split into three groups on the basis of their weights on 20th March with mean values of 22, 27 and 33 kg. On the basis of their weights the second and third groups were judged to be 9 and 19 days respectively ahead of the first group.

It is generally accepted that leanness of terminal sire sheep breeds should be increased. However, it is very difficult to define formally a selection goal for these breeds. Put loosely, at a given age, we probably require terminal sires with as much extra lean meat as possible, whilst minimising any increase in fat weight. In the past, selection has been mainly on weight for age, but this may actually increase fatness at the age of selection.

Intuitively we expect some in vivo measurements of carcass composition to help in achieving the selection goal. In practice, in vivo measurements of carcass composition in sheep are often imprecise, though the treatment of the animals can affect the relative precision. Ad libitum feeding on a high energy, high protein feed appears to increase the variation in carcass composition of ram lambs compared to those on a lower plane of nutrition (Simm et al, 1985 compared to Cuthbertson et al, 1983). Under these conditions we were able to predict carcass composition reasonably precisely from live weight and ultrasonic measurements (means and original and residual s.d.s for carcass lean weight: 18.30, 1.60 and l.00 kg and for fat weight 13.74, 2.70 and 0.96 kg).

The optimal balance of amino acids in the diet of the growing pig was estimated by ARC (1981) on the basis of a number of disparate studies augmented by data on the amino acid composition of the whole body on the premise that the amino acids incorporated into accreted body proteins are the major determinant of requirements and that this pattern is not distorted by inequalities in the utilisation of individual amino acids. In an accompanying paper (Wang & Fuller, paper no. 91) an optimal pattern was derived by direct experiment which was shown to be utilised better than that described by ARC (1981). That pattern, however, which related to one particular rate of nitrogen input and the particular rate of protein accretion which that input supported, includes two components, a requirement for maintenance and a requirement for protein accretion. There is clear evidence from studies with rats and chicks that the optimal pattern of amino acids for maintenance and growth are quite different and so the optimal pattern for any particular rate of growth will depend on the relative contributions of the two components. The purpose of this experiment was to estimate both.

There has been recent interest in all the red meat species in a group of compounds known as β-agonists which reduce the proportion of fat in the carcass when added to the diet. In this work the effects of the novel Glaxo compound GAH/034 are reported.

Sixty crossbred (Large White x Landrace) gilts from 16 litters were used. From 25 to 80 kg live weight, 2 groups of 10 were fed a control diet (C) containing 13 MJDE and 190g crude protein/kg. Four treatment (T) groups of 10 were fed the same diet containing 4 ppm GAH/034. All groups were fed on the same time-based feeding scale which allowed 1.2 kg/pig/d at 25 kg Increasing by 0.2 kg/d each week to an upper limit of 3.0 kg/day. All pigs were fed the control diet for four days before slaughter at the IFR abattoir at 80 kg live weight after which a range of carcass and meat quality tests were applied. Half the pigs were fully dissected into lean, bone, skin, subcutaneous fat and intermuscular fat.

The reproductive performance of the sow may be associated with the amount of fat stored in the body and the rate at which fat may be depleted. As body fat represents the easily mobilisable reserves of energy, an accurate and practical measurement of fat content is crucial. King et al (1986) have shown that linear baekfat measurements are the best single predictors of body fat compared to any other indirect indices of body composition. However practical experience has also suggested that fat measurements over the tuber coxae of the ileum (hip bone) will also provide an assessment of the fat status of a sow although its relationship to back fat depth is uncertain. Furthermore ultrasound techniques have not been tested in commercial conditions and the effectiveness of normal commercial practice in maintaining body fat reserves has not been previously examined.

The object of the investigation was to assess whether the fat status of the sow as determined by ultrasonic fat measurements at the P2 position (6.5 mm from the midline of the backbone at the last rib) and hip bone would give an objective assessment of the condition and performance of the sow. The effectiveness of normal commercial practice in maintaining herd condition was also assessed.

Weight gains can occur with substantial fat losses and therefore liveweight change is unlikely to form the basis of feeding strategies, whereas the fatness of the animal may be a more appropriate criterion. Eighty Large White x Landrace gilts were first mated at 123.5 kg ± 1.54 with a P2 of 14.5 mm ± 0.24 [Meritronics] and 12.7 mm ± 0.19 (Vetscan]. Half these gilts were fed to be fat [F] at parturition [target 20-24 mm P2) and half were fed to be thin [T] [target 10-14 mm P2). F gilts consumed more feed during pregnancy and gained more weight and backfat than T gilts [all differences between the 2 treatments were significant P˂0.001). The number of piglets born and the number of live births were not affected by feeding gilts to be fat or thin, but fat gilts produced significantly heavier piglets. After parturition, half of both F and T gilts were offered either 7 kg of food per day [H] or 3 kg per day [L] and half were sucked by litters of 5 piglets and half by litters of 10 piglets during a 28 day lactation. Piglets were not given creep feed. Fatness of the gilts at parturition, feed level during lactation and sucking litter size all significantly influenced both the absolute and the change in liveweight and backfat from farrowing to weaning. Weight and P2 changes are shown in Figures 1 and 2. The performance of the litter was also significantly affected by the fatness of the gilt at parturition and by the number of piglets sucking. Results for each treatment group are given in Table 1. Animals offered the high level of feed during lactation had a significantly shorter interval between weaning and conception. There were also positive relationships between readiness to rebreed and absolute liveweight and absolute fatness.

Piglet mortality between birth and weaning represents a considerable economic loss to the national pig herd. Despite general reductions in pre-weaning losses, mortality figures from the better producers would suggest that improvement is possible. In attempting to reduce piglet losses it is important to establish when the deaths occur and their underlying causes. Together, starvation and overlying has been reported to account for 75% of all pre-weaning losses. Furthermore, chilling predisposes newborn piglets to starvation, overlying and disease, (Curtis, 1974). Piglets require a much greater environmental temperature than the farrowing sow, and therefore heated creep areas are provided to satisfy their needs. In addition the creep offers a safe area away from the danger of overlying by the sow. The greater the time piglets spend in the creep areas, the lower is the likelihood of them being chilled or overlain. Most studies show that 50% of pre-weaning mortalities occur during the first two days after farrowing, (Pomeroy, 1960 and English et al., 1977), therefore use of the creep during this period would seem important to piglet survival. This study provides information on piglet behaviour during the first week of life in relation to farrowing pen temperature and two designs of creep.

A feeding trial with young cattle, supported by measurements of digestibility and intake in lambs, was carried out to compare dried poultry manure (DPM) with cottonseed meal (CSM) or a urea maize mix (UM) as supplements to unimproved dry season grazing.

Eighty Mashona steers, aged 9 months, initial live-weight 157 kg, were divided into eight groups, one of which was used as an initial slaughter group. The remainder were grazed by day and penned overnight (119 days). Whilst in the pens they received either no supplement (C) or DPM; CSM; UM; DPM + CSM; CSM + CSM; UM + CSM. The single supplements contained 150g crude protein and the double supplements 250 g crude protein per day. All animals were offered a mineral supplement and water was available during the day. At the end of the dry season half of the animals from each group were slaughtered and half retained to measure compensatory growth.

Twelve lambs housed in crates each received one of the treatments (C, DPM, CSM, UM) with veld hay ad libitum (CP 2.5%) to measure digestibility and intake.

Ammonium bicarbonate is a solid, non toxic compound wich could be easily handled and applied to roughages as an alternative source of ammonia. The preliminary experiments reported here were designed to study the possibility of using ammonium bicarbonate for treating wheat straw.

In the first experiment samples of 100 g of wheat straw were placed in 28 glass jars (11 volume). The jars were then assigned in a factorial design to four levels of ammonium bicarbonate (0, 25, 50 and 75 g/kg on ammonia basis) and to seven temperatures of treatment (0, 20, 40, 60, 80, 100 and 120°C for 3 hours). After the treatment the straw samples were ground with a laboratory hammer mill (5 mm sieve). Two g of each sample were incubated in two replicated nylon bags (Ørskov, Hovell and Mould, 1980) into the rumen of two cannulated cows and withdrawn after 48 hours. The cows (mean live weight 550 kg) were fed 1.8 kg/100 kg live weight of a diet based on 0.80 hay, 0.15 dried sugar beet pulp and 0.05 soyabean meal, supplemented with vitamins and minerals.

Wahed and Owen (1986) reported a 0.33 increase in barley straw dry matter (DM) intake when stall-fed goats were allowed to refuse 0.5 of the amount offered rather than the 0.2, or less, allowed in conventional ad lib feeding. This approach offers a possible strategy for maximising intake and improving utilization of straw in Third World countries developing stall feeding systems for goats based on crop residues and other by-products. Generous feeding of straw (say allowing refusal-rates of 0.5 of amounts offered) could be followed by the refeeding of refusals after treating them with ammonia.

The experiment was undertaken to investigate refeeding straw previously refused by goats and to measure the effect of ammonia-treating such refusals on Intake and digestibility. Barley straw and refusals (0.5 of amount offered) of the same straw were chopped and half of each material treated with ammonia (0.11 of 330 g NH3/kg solution per kg straw in sealed plastic bags for 30 days).