Two farm trials were made to investigate the response to a second implant with the anabolic agent zeranol. Seventy cattle were implanted at the start of the growing period, at 10 to 12 months of age, the remaining 49 cattle being left as controls. Five months later, at the beginning of the fattening period, some cattle from each of the treatments during the growing period were implanted. The response to implantation in both periods was significant on both farms (P<0·05). During the fattening period there was no significant difference in the performance of cattle implanted only at the start of the growing period and that of the control animals, which suggested that the response to the earlier implant was permanent. Although differences in performance during fattening for cattle implanted twice, compared with that for cattle implanted for the first time at the start of fattening, were not statistically significant, on both farms performance was lower for the cattle implanted twice. These results suggest that the response to zeranol in the fattening period may be reduced by approximately 0·30 for cattle previously implanted. Over the combined growing and fattening period, cattle implanted twice showed a significant response in comparison with cattle given only one implant (P < 0·05).

Theory that successfully explains the magnitude and range of estimates of protein retention (PR) efficiency from the cost of turnover of existing protein indicates that conventional curves for growth description are inappropriate for protein growth. A solution to this problem is found in the consideration that the rate-limiting steps for protein synthesis (PS) and breakdown are likely to be associated with the diffusion of metabolites in and between cells. The algebraic scaling of nuclear and cellular diffusion capacity with tissue or total body protein leads to a parameterization of the primal differential equation for PR (kg/day) based on two terms representing PS and breakdown, viz.where c is an arbitrary constant, Q is the proportion of nuclei active in cell growth or division in a tissue or the whole body, α is the limit mass for protein (P, kg) in a tissue or the whole body, the power X+Z represents the rate-limiting steps in protein breakdown and Y is the power of the relationship between cell volume and the amount of tissue protein. For the whole body, the contribution of the different tissues should be weighted in proportion to their PS rates with, on average, Y = 1/2. The constant 4/9 arises from the scaling of the specific diffusion rate of DNA activator precursors from nuclear dimensions and from the relationship between nuclear and cell volume. Experimental evidence on protein breakdown rate as well as protein and body mass points of inflection indicates that the range of theoretically possible numerical values of the rate-limiting powers X+Z = (i+ 3)/9 for i = 1, 2, … ,12 seems adequate for the description of the range of observed whole body protein and body mass growth patterns for mammals. Q = 1 represents maximal protein retention, and for 0 < Q < 1, experimental evidence exists in support of a theoretical relationship between Q and food ingestion. The conclusion follows that some knowledge of the protein limit mass (α) and of the point of inflection (related to X + Z) is the main requirement for the application of the theory for description and prediction in animal nutrition and breeding.

The effect of monensin supplementation on suckling male dairy calves was studied on a commercial farm. Twenty-eight calves were given monensin supplements from the age of 1 week and compared with a similar group not given monensin. During a 52-day suckling period, the supplemented calves gained 0·12 faster, with little difference in the conversion ratio of metabolizable energy into live weight. During the subsequent 42 days, there was no difference in daily gain, but the supplemented animals were 0·064 more efficient in the conversion of metabolizable energy into live weight.

The potential problems concerning the use of manioc, from the processed roots of cassava (Manihot esculenta), have been reviewed by Oke (1978) and Walker (1983). Although current legislation has ensured that in recent years the levels of cyanogenic glucoside in imported cassava have been negligible (Walker, 1985), there is still conflicting evidence on the maximum level of manioc which can be included in pig diets without adverse effects on digestion and performance. In a previous study (Partridge, 1985), 300 g manioc per kg tended to increase the proportion of energy apparently absorbed from the large intestine compared with lower levels. This may have been partially responsible for some of the digestive upsets found with young pigs by O'Grady and Hanrahan (1979). Evidence of the effect of manioc on performance can be misleading due to palatability problems and therefore lower food intakes (Müller, Chou and Nah, 1975; Papodopoulos, Ziras and Kalaissakis, 1983).

1. The primary growth of perennial ryegrass was cut between 7 and 9 June and ensiled with formic acid at 2·5 1/t. The regrowth was cut on 24 July; part was dried at high temperature (dried grass), the remainder was left to dry in the field (hay). The dried grass (DG) and part of the hay were ground and pelleted, the hay being pelleted alone (PH) or with the addition of formaldehyde at 20 g/kg crude protein (PHF). The remainder of the hay was offered in the chopped form (CH). The four supplements (CH, PH, PHF, DG) were offered at two levels, 6·5 (L) and 130 (H) g dry matter per kg live weight to 54 British Friesian steers (initial live weight, 110 kg) receiving the silage ad libitum.

2. The silage had a high pH and a high proportion of the total nitrogen was in the form of ammonia, indicating poor fermentation. The solubility of nitrogen in the supplements was highest (262 g/kg total nitrogen) in CH, progressively less in PH and PHF and lowest (122 g/kg total nitrogen) in DG.

3. Total dry-matter intake was highest with DG at the higher level of inclusion. Dry-matter intake was significantly higher for PH and PHF than for CH (P < 0·001). However, intake of digestible energy did not differ between hays. Live-weight gain was increased from a low level of 0·24 kg/day (silage alone) by all supplements, but this effect was greater with DG than with the hays (P < 0·001). Level of supplementation increased live-weight gain from 0·54 to 0·74 kg/day.

4. Supplements of dried grass gave higher live-weight gains than did hay made from the same sward. However, the results indicate that supplementation of badly preserved silage with grass hay of good quality can produce acceptable levels of performance of up to 0·70 kg/day in 4-month-old steers. Processing of the hay had little effect on animal performance.

Two field trials were conducted with 138 and 123 bacon-weight pigs respectively from one farm to determine the effect on bacon yield of feeding the animals sugar solutions prior to slaughter. Three treatments were tested: immediate slaughter on arrival at the abattoir; lairage overnight with access to water only (15 h); and overnight lairage with access to a sugar solution (6 h) followed by water only (9 h) prior to slaughter. A glucose syrup solution was used in one trial and a sucrose solution of similar hexose-equivalent concentration (550 g/kg) in the other. Access to either of the sugar solutions, relative to water only or immediate slaughter, increased bacon yield. This was entirely due to glucose-fed pigs having a higher carcass yield (2·3 % and 1·5 % respectively) and a trend in this direction for the sucrose-fed animals (0·9% and 1·0% respectively). Carcasses of glucose-fed pigs actually gained less weight than those of their counterparts during the curing process, but this did not occur with the sucrose solution. Access to sucrose relative to water only and immediate slaughter increased liver weights by 32% and 42% respectively. Lower hepatic responses were obtained with glucose syrup (18% and 12%). Both sugar solutions reduced muscle ultimate pH (0·1 to 0·2 unit) relative to water only in overnight lairage.

In a trial to investigate an ill-thrift problem in lambs on an Exmoor farm frequent oral drenching with cobalt sulphate was compared with pasture spraying. There were two groups of twin lambs reared respectively on sprayed and unsprayed pasture. One partner from each twin set was drenched with cobalt sulphate every two weeks. There were no significant differences in live-weight gain up to weaning time. Thereafter there was little difference in the progress of the twins on sprayed pasture. On the unsprayed pasture, however, the drenched lambs had gained an average of 9 lb live weight more than their partners over a period of 15 weeks but were still about 7 lb lighter than the lambs on sprayed pasture.

Blood vitamin B12 concentration, assayed with Lactobacillus leichmannii, was not well correlated with the treatment of the groups and all values were above commonly accepted critical levels.

The objective of this study was to investigate the effect of various factors on average pig weight at weaning on farms using early weaning. Farms were selected based on average weaning age and whether they recorded lactation food intake and litter weights at weaning. The database contained 9834 litter weights and 8903 food intake records. Average pig weight at weaning, litter size at weaning, weaning age, and average daily food intake during lactation (ADFl) were 4·9 (s.d. 1·0) kg, 9·3 (s.d. 1·6) pigs, 16·8 (s.d. 2·8) days, and 4·9 (s.d. 1·1) kg, respectively. Litter size, weaning age, parity, farrowing season, and ADFl groups influenced average pig weight at weaning (P < 0·01). Three two-way interactions between parity and season, weaning age and farrowing season, and weaning age and ADFl groups were found fP < 0·01). Average pig weights for litter sizes between six and 10 were higher than those between litter sizes one and four, and 11 and 22. Parity 1 sows produced lighter pig weights than any other parity group during any other season (P < 0·01). Average weights of weaned pigs farrowed during the summer in all parities groups were lighter (P < 0·01) than those during the autumn. Pig weights for weaning ages between 22 and 21 days during the summer tended to be lighter than those during the autumn. Pigs weaned between days 16 and 22 of age in the high ADFI group (>5·6 kg) were heavier (P < 0·01) than those in the low ADFl (> 4·2 kg) group.

Starter diets of low acid binding capacity (ABC) are sometimes recommended to ensure an acidic environment in the stomach of newly weaned pigs. A low stomach pH aids protein digestion and provides a barrier against the passage of bacteria into the small intestine. A diet of low ABC can be formulated through careful selection of ingredients (Jasaitis et al., 1987). The present study was undertaken to measure the ABC of feed ingredients commonly used in pig starter feeds and to determine if diet ABC can be predicted from the ABC of the ingredients.

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.

The number of entire male pigs slaughtered in Great Britain has increased steadily over the past 10 years and they now constitute some 45 per cent of the national population. Although there has been concern about possible boar taint, the industry has apparently experienced few problems. However, boar taint continues to be a major concern in other countries, possibly reflecting heavier slaughter weights and breed differences. Limited evidence indicates that earlier maturing breeds, such as the Pietrain and Duroc, tend to have more taint than other breeds of the same weight or age. This has implications for the wider use of specialist meat type sires which now supply atleast 10 per cent of the genes in the commercial British slaughter population.

Both level of feeding and dietary composition have been demonstrated to influence bacterial colonisation and diarrhoea in the weaned pig. Specifically, Bertschinger et al (1979) demonstrated that diets low in protein and energy and high in fibre content could protect the weaned pig against challenge with live pathogenic E. coli. However, pig growth was so compromised that it proved to be unsatisfactory for commercial practice. Miller et al (1984) demonstrated that a diet in which the protein (casein) had been hydrolysed to constituent amino acids or peptides, thus markedly reducing its antigenicity, also could prevent post-weaning diarrhoea and minimise associated gut changes. They therefore, suggeted that one of the factors which may contribute to the aetiology of post-weaning diarrhoea is a transient hypersensitivity to dietary antigens prior to tolerance development.

The aim of this present work was to attempt to combine these two approaches yet achieve acceptable piglet performance, the long-term aim being to design weaner diets which effectively control post-weaning diarrhoea on commercial farms without resulting in the use of antibiotics either prophylactically or therapeutically.

Daily oral dosing in mid afternoon with 3 mg of the indoleamine, melatonin, from early June onwards is highly effective in advancing the breeding season of both Greyface and Scottish Blackface ewes kept under a natural photoperiod; the mean reaction interval from initial dosing to the onset of ovarian activity in Scottish Blackface ewes being around 65 days compared with 110 days for untreated controls (Robinson et al 1985). Advancing the starting time for the melatonin treatment to mid-March gave a similar reaction interval with behavioural oestrus occurring in late May/early June (Wigzell et al 1986a). Following this reversal of the breeding season by melatonin, continued melatonin treatment in unmated ewes resulted in a period of oestrous cyclicity lasting 4 to 5 months. Thereafter the ewes became refractory to melatonin and returned to anoestrus at a time when untreated controls were commencing ovarian activity (Wigzell et al 1986b). These observations prompted us to investigate the effects of different durations of melatonin treatment on ovarian activity.

Little is known about the cobalt requirements of goats, or of ‘normal values’ for related diagnostic parameters. Consequently an experiment was set up, to define their minimum cobalt requirement and to establish critical levels of some diagnostic parameters.

24 wether goats were housed, fed a cobalt deficient diet of urea treated hay and cereal, and randomly allocated into 4 groups. Groups 2-4 received a cobalt supplement as detailed below in addition to the 0.04 mg Co/kg DM supplied by the diet. The goats were weighed weekly and blood sampled fortnightly.

A previous investigation, reported at the Winter Meeting 1985, showed significant effects of growth promoters on carcass composition and on the eating quality of sirloin steaks. The growth promoters investigated factorially were (a) hormonal implants (heifers, Zeranol; steers, Zeranol + Trembolone acetate), (b) feed additive (Avotan) and (c) fishmeal. The experiment was repeated during the winter of 1984/85, with the eating quality investigation expanded to cover some 192 households, using sirloin steaks from all 64 cattle involved in the investigation. In addition, the rate of carcass cooling in the left-hand side of each animal was measured using electronic probe thermometers placed in the longissimus dorsi immediately after slaughter. This data was used to test the hypothesis that rate of carcass cooling was negatively related to the fat content of the carcass and with overall eating quality due to the effects of cold shortening.

The Slaughter of Animals (Humane conditions) Act 1990 prohibits killing animals within sight of another. There is a need to produce scientific evidence to show whether the sight of sticking (exsanguination) is stressful to animals that happen to observe this procedure. This has important consequences on the design of stunning and sticking areas in the abattoir. Sticking in a separate are can lead to a delay between stunning and sticking and increase the chance of animals regaining consciousness.

In this study experiments were carried out to determine whether sheep did responded in a way which could suggest they found the experience of witnessing sticking distressing.

Legislation to control veterinary medicinal products is undergoing continual development in the EEC and UK and therefore the risks are continually reassessed. In the present paper current and future legislation together with consumer concerns both real and imaginary are reviewed.

Since the EEC ban on hormonal growth promoter implants in 1986 the remaining legal products are all feed additives. Registration of feed additives in the EEC is controlled under Directive 70/524 and its various amending directives. this directive is concerned with all products added to feed and mainly includes substances used to affect the quality of the feedstuff i.e., emulsifiers, stabilisers, antioxidants, colorants and binding agents and also vitamins and micronutrients. The majority of growth promoters exert their affects by antimicrobial activity and these and certain prophylactic medicinal products such as coccidiostats are also included. All products with a therapeutic action are controlled under the Veterinary Medicine Directives 81/851 and 81/852, quite separate legislation and under the responsibility of a different department within the EEC Coimdssion. However, there is provision under Directive 84/587 amending 70/524 to transfer the medicinal feed additives to 81/851 and 81/852.

Different sources of dietary fibre (defined here as non-starch polysaccharides, NSP) are hydrolysed to varying degrees in the GI tract of pigs. Unlike starch, NSP cannot be digested to its monomeric constituents by mammalian enzymes, but instead must be fermented by the gut microflora, to yeild volatile fatty acids (VFA). These VFA, like the glucose derived from the digestion of starch, are subsequently absorbed and metabolised to yeild ATP, but with a lower efficiency than glucose. Clearly, therefore, knowledge of the relative amounts of products of fermentation and digestion which are absorbed, will enable the nutritive value of a feed to be described more accurately. We report the time course of absorption of glucose, VFA, lactate, and α-amino N from semi-purified diets containing two contrasting sources of NSP, wheatstraw (WS) and sugar beet pulp (SBP), by growing pigs.

In a recent study of the efficacy of two methods of oestrous synchronisation in dairy heifers, progesterone profiles and ultrasound results showed that late embryonic/early foetal loss had a small but nevertheless important effect upon pregnancy rates (Logue & others 1991). Since some preliminary results were available which showed that the use of a 3 mg norgestomet ear implant alone, rather than in combination with a 3 mg norgestomet and 5 mg oestradiol valerate injection (Crestar Intervet UK Ltd), enhanced pregnancy rates in beef heifers (Favero & others 1989) and the technique was being used in Embryo transfer (ET) recipients (Broadbent pers com) it was felt that a further investigation of the technique was merited.