Consumption of lamb in the UK has declined from 149g per person per week in 1970 to 93g in 1985 despite a reduction, in real terms, in its cost. Circumstantial evidence suggests that the decline is, in part, due to its excessive fatness. The use of entire male cattle and pigs increases the efficient production of lean meat and boars are now widely used. Although a similar potential has been recognised for lamb, British producers have maintained a policy of castration of lambs and butchers seem reluctant to sell meat from ram lambs because they suspect it may be inferior in eating quality. This work on sensory and consumer evaluation of meat from ram, castrate and ewe lambs was therefore conducted and forms part of an assessment of carcass and meat quality of entire Down cross lambs from crossbred ewes on improved hill grazing.

Forty-two lambs, comprising a balance of seven of each of entire male, castrate and ewe lambs from both Dorset Down and Suffolk sires, were reared at Redesdale EHF and slaughtered in August in a commercial abattoir. Hot carcasses ranged from 13 to 22 kg. To avoid the likelihood of induced toughness using conventional chilling conditions, all the carcasses were placed, at 2 hours after slaughter in a refrigerated vehicle operating at 10°C for transportation to Bristol.

It has been known for many years that the annual breeding cycle of the sheep is controlled by photoperiod. More recently it has become apparent that this process involves the pineal gland. Light is effectively monitored by retinal photoreceptors within the eye which transmit a neural signal to the pineal gland, and this in turn responds by secreting melatonin during the period of darkness. As daylength decreases in the autumn, the duration of elevated melatonin secretion increases, and this changing ratio of high:low melatonin during each 24h period stimulates breeding activity.

Both timed (by afternoon feeding or injection) and continuous (by subcutaneous or vaginal implant) administration of exogenous melatonin to ewes in mid-summer have recently been shown to mimic the effects of decreasing photoperiod by advancing the onset of the breeding season. The present experiment was undertaken to investigate the ability of a subcutaneous implant of melatonin to manipulate reproductive activity of ewes under field conditions in the U.K.

In many breeds of ewe, body condition at mating is a major determinant of ovulation rate and lambing rate. It has been shown that differences in body condition are associated with differences in the number of large, potentially ovulatory ovarian follicles (McNeilly, Jonassen and Rhind, 1987) and mean circulating FSH concentrations (Rhind and McNeilly, 1986). Differences in circulating gonadotrophin concentrations could be a function of parallel differences in either hypothalamic activity or pituitary sensitivity to GnRH; either or both of these factors could be affected by ovarian steroid feedback. The aim of this experiment was to investigate the effect of ewe body condition on these parameters in the absence of ovarian steroidal feedback.

LH secretion was used as an indirect measure of the secretion of GnRH from the hypothalamus since LH secretion closely mirrors GnRH secretion (Clarke and Cummins, 1982). Pituitary sensitivity was assessed by measurement of LH release following injection of a GnRH bolus.

At 2 and 7 days after bilateral ovariectomy, blood samples were collected from each of 2 groups of 12 mature Scottish Blackface ewes in condition scores of 2.75/3.00 (H) or 1.75/2.00 (L) and with mean(+ s.c.) liveweights of 53.4 ± 1.47 kg and 38.2 ± 1.80 kg respectively. Samples were collected every 15 mins for 8 h and then for a further 3 h after each ewe was injected (I.V.) with 10 μg GnRH. They were analysed for concentrations of FSH and LH.

A previous report from this laboratory recorded a yield of 60 per cent of embryos recovered at the morulae/blastocyst stage of development after the in vitro maturation and fertilization of bovine follicular oocytes and their subsequent culture in vivo in the sheep oviduct (Lu et al., 1987). When these embryos were transferred by non-surgical procedures to recipient heifers, they established normal pregnancy rates (12/18, 67%) which resulted in the birth of seven sets of twins and five single calves. The objective of the present study was to examine the possibility of large-scale production of cattle embryos using the oocyte maturation and IVF procedures previously employed. A further objective was to determine the effect on embryo yield of transferring varying numbers of fertilized eggs (zygotes) to the sheep oviduct for in vivo culture.

Ovaries were collected fran beef heifers shortly after slaughter and brought to the laboratory within one hour, held at 30°C in phosphate buffered saline supplemented with 0.3 per cent bovine serun albumin and 0.05 mg kanemycin/ml. Non-atretic vesicular follicles (2 - 6 mm diameter) were dissected fran the ovaries and the oocytes liberated by follicule rupture, particular care being taken to preserve the integrity of the oocyte-cumulus-corplex.

Previous studies have shown that for Scottish Blackface ewes kept under a natural photoperiod and exposed to the ram the daily administration of the indoleamine melatonin from June onwards advanced the breeding season and appeared to increase ovulation rate and subsequent litter size (Wigzell et al., 1986). In the primate, exposure to melatonin has been shown to stimulate progesterone production by the corpus luteum in an in vivo perfusion system (Webley & Hearn, 1987). Similarly melatonin administered at physiological concentrations stimulated progesterone production by bovine and human granulosa cell cultures (Webley & Luck, 1986).

The present experiments were carried out to determine:-

• (a) whether or not melatonin enhances progesterone production and thereby the establishment of pregnancy and embryo survival in the ewe.

• (b) whether melatonin acts directly on the corpus luteum or indirectly via increased activity of the hypothalamic GnRH pulse generator.

• (c) whether or not the presence of the ram in the immediate post-oestrus period alters the endocrine status of the ewe and thereby influences conception.

High food intake in early pregnancy resulted in increased prenatal mortality and reduced subsequent litter size in many studies using gilts (den Hartog and Van Kempen, 1980). With multiparous sows there is generally no difference in the rate of embryo survival or litter size with high feeding in early pregnancy (Toplis et al, 1983, Dyck & Cole, 1986).

Limited evidence suggests that sows fed low levels in lactation and then a high level early in the following pregnancy may show increased rates of embryo mortality (Pike and Boaz, 1972; Hughes et al, 1984). The effect of high feeding may be due to low plasma progesterone concentrations (Hughes et al 1984; Dyck et al, 1980) in early pregnancy which may be associated with reduced embryo survival and litter size.

This study was designed to investigate the effects of high or low feed intake in lactation and early pregnancy on plasma progesterone concentrations in early pregnancy and subsequent litter size using multiparous sows.

Probiotics are becoming increasingly advocated as being of benefit to calf rearers as a feed additive to improve the growth rates and health of rearing calves. There are several organisms and mixtures of organisms that are now commercially available which may prove to be a realistic alternative to the widespread use of antibiotic growth promoters. There is a lack of published work by independent researchers on the efficacy of probiotics for rearing calves but a wealth of manufacturers literature. Two experiments at Drayton E.H.F. investigated the use of Enterococcus faecium as a probiotic agent during the rearing period of purchased calves.

Feed accounts for over 75 per cent of the variable costs in beef production systems. Any improvement in feed conversion efficiency will therefore have a beneficial effect on enterprise profitability. Growth promoters are commonly used to improve animal performance by increasing liveweight gain and/or improving feed conversion efficiency. With the recent ban on hormone implants in EEC countries, more emphasis has been put on the use of feed additives to improve performance.

Producer experience would suggest that the routine inclusion of sodium bicarbonate into barley beef rations can show beneficial responses in terms of animal performance. The magnitude of these responses is not well quantified, nor is the potential interaction between sodium bicarbonate and other feed additives.

Rogers and Davis (1982) reported that sodium bicarbonate decreases the in vivo production rate of propionate, decreases retention time of liquids and alters digestibility of nutrients. Increasing ruminal bypass of nutrients may improve utilisation by altering the site of digestion with a subsequent improvement in animal performance. Rogers and Davis (1982) also described the effect of monensin; which increased in vivo ruminal production of propionate, increased ruminal retention time of solids and liquids and improved digestibility of nutrients.

Results from a previous experiment with growing steers showed that straw from varieties of winter and spring barley or winter wheat supported different intakes and rates of gain. It was possible to identify those cereal straws most suitable for inclusion in low cost diets for beef cattle. The object of this work was to assess whether complete diets containing a minimum of 35% “good” straw could sustain a high rate of gain in finishing cattle. The trial used 45 Hereford cross steers that weighed 360 kg at the start. There were three types of straw examined; straw from the spring barley variety Corgi, untreated (UC) and ammonia treated (AC) together with ammonia treated winter wheat (AW) cv. Longbow;. Each straw type was included in a complete diet containing either 0.35 (L), 0.45 (M) or 0.55 (H) straw. Ammonia treatment was carried out in an oven with 0.03 anhydrous ammonia for 24 hours. The straw was processed through a tub grinder and the chopped material was transferred to a mixer wagon for diet preparation. All the diets contained fishmeal and urea and equal proportions of rolled barley and molassed sugar beet pulp substituted for the straw. The complete diets were offered ad libitum and the steers were weighed fortnightly until they were estimated to provide carcasses in MLC fat class 4L. Digestibility data for each diet was derived in a subsidary trial using cattle fed ad libitum. The digestibility coefficients for D11 were 0.67 UC; 0.68 AW; 0.69 AC and 0.66 H; 0.68 M; 0.70 L (S.E.D. ± 0.66).

The increasing sales of beef through retail supermarket outlets has been reflected in specification buying by wholesalers being more apparent. The objective of supermarket buyers is to obtain continuity of supplies throughout the year and this trend is likely to increase. Faced with these requirements producers of grass finished cattle (representing 40 per cent of beef supplies) have little objective information on which to plan their production systems. The limited scientific data available tends to be short-term with little, if any, information available on eventual carcass and eating quality.

A long-term project has therefore been initiated at Edinburgh to examine the effects of production variables on the performance and carcass characteristics of grass-finished cattle within a 20 month beef system. One aspect of this work has centred its attention on providing information on the rates of change (with time) of carcass characteristics, during the grazing season, in relation to breed, sex and variation in grass availability.

It has been demonstrated previously that sward height has a large effect on herbage intake and performance of spring calving cows and their calves (Wright and Russel, 1986) with maximum cow and calf live-weight gain occurring when sward height is maintained at 8 to 10 cm. No comparable information is available for autumn calving cows, and the aims of the present experiment were to examine the effect of sward height on cow and calf performance, in the pre- and post-weaning periods in cows that were turned out to pasture in late lactation at two levels of body condition.

The experiment was a 2 x 2 x 2 factorial, with two levels of winter feeding, two sward heights from turn-out to weaning, and two sward heights from weaning to housing. During the summer grazing periods there were two replicates. Thirty-nine Hereford x Friesian cows (mean calving date 17 Sept, 1986) with Charolais-cross calves were used. The experiment started on 30 October 1986 when the cows and calves were housed in two groups. One group (L) was fed silage alone and the other group (H) was fed silage plus barley. Estimated daily metabolisable energy intakes were 63 MJ (L) and 92 MJ (H). Calves were fed 1 kg barley/day plus hay ad 1ibitum. The cows were mated to Charolais bulls for 8 weeks from 15 November 1986.

Protected fat has been used successfully in diets for lactating and growing ruminants. This study was carried out to investigate the effects of including a source of protected fat - Megalac ® -in complete diets for artificially reared lambs.

The trial involved 39 lambs which were weaned at 30 to 35 days following a period of artificial rearing on a ewe milk replacer containing 60 g fat per kg and fed at a restricted level.

The lambs were penned individually on sawdust and were given access to one of three complete diets from 20 days of age. The diets were in pellet form and differed mainly in the level of Megalac included (Table 1). Megalac is a protected fat which is a calcium soap and contains (g/kg) oil 850, calcium 90 and has the approximate fatty acid composition (g/kg) C14 15, C16 110, C18 50, C18:1 400, C18:2 95. Lambs were allocated to diets within blocks which varied according to sex (entire male or female) and breed (Cambridge or Suffolk x Cambridge).

The presence of high concentrations of branched-chain fatty acids in lamb fat results in soft discoloured tissue and objectionable flavours and odours. However, the factors regulating their synthesis and deposition are Incompletely understood. In some studies, but not others, excessive deposition is associated with high cereal diets. Their concentrations may be higher in rams than wethers and there is circumstantial evidence for differences between breeds. We have Investigated their concentration in ewe and ram lambs of three breeds: East Friesland, Oxford and Texel.

Ten lambs of each breed and sex, born in March, were fed to appetite twice daily a concentrate (barley 683 g/kg, crude protein 170 g/kg DM ME 12.1 MJ/kg D.M) with hay available ad libitum. Animals were slaughtered together, by conventional procedures, at 27 weeks of age (± 4 days) and the hind loin was removed and dissected. The subcutaneous fat was analysed for fatty acid composition by capillary gas-liquid chromatography on Chrompack CP Sil 88 and CP wax 57 CB.

Various beta-agonists appear to be effective compounds to improve carcass quality. They do this by reducing fatness, repartitioning the energy into extra lean tissue and improving killing-out proportion. Potentially though, they could also have undesirable effects on meat quality since catecholamines can stimulate glycogenolysis ante-mortem and so reduce the potential for muscle acidification after death. However, in contrast to the large amount of work on the effects of beta-agonists on carcass quality there appears to be little on meat quality. In this work therefore we examined the influence of two beta-agonists on aspects of lean meat quality in sheep. Twenty-four castrated male sheep were divided into three groups and Individually fed a complete pelleted diet containing 12.9% protein. One group was a control, one was given Cimaterol (10 mg/kg diet) and one was fed Clenbuterol (2 mg/kg diet).

Both the quality and physical properties of fat are important attributes of pig carcass quality. The physical properties of fatty tissue, particularly its softness, affect its appearance, ease of cutting and carcasses with excessively soft fat are unsuitable for processing. Concern about soft fat is highlighted as one of the most serious problems judging from the level of industrial complaints and queries.

Softness judged by a sensory thumb test may vary considerably between assessors and therefore a portable pentrometer which measures the resistance to penetration by a small probe was developed. The probe indicates firmness in units from 0 to 100O. Units less than 575 are equivalent to a sensory score of 1 or 2, values of 575 to 775 a score of 3 or 4; 776 to 875 a score of 5 or 6 and values more than 875, a score of 7 or 8 on a firmness scale of 1 to 8. Six probes were used by MLC regional officers in 28 meat plants which were stratified by size and throughput and chosen from diferent regions of the country.

There is a growing concern in the UK meat industry over carcasses containing soft fat, which prove difficult to cut and process. This may be caused by the feeding of high levels of unsaturated fatty acids resulting in high levels in carcass fat, and hence soft fat. This trial examined the critical levels of linoleic acid affecting fat firmness.

It is well known that feeding excess linoleic acid, which is preferentially deposited, has the effect of producing soft backfat in pigs. However, the firmness of this adipose tissue, as measured by mechanical probe, can often be better related to the proportion of stearate in the lipid than to linoleate. This study attempted to harden the backfat of bacon pigs by feeding a high-fat diet containing a high concentration of stearate. For comparison, pigs were fed a diet similar in all respects including linoleic acid concentration, except that the proportion of stearate was low, while that of oleate - the most abundant fatty acid in backfat, but previously found to be of low importance for its mechanical consistency - was high.

Increasing concern has been expressed about deterioration in the handling and eating quality of pigmeat produced in modern U.K. circumstances. Many of the problems are attributed to excessive leanness. It has been suggested that the Duroc breed may produce a better quality product than current U.K. white breeds as a result of its higher level of intramuscular fat. Diet composition has also changed over time, with increasing use of a wider variety of ingredients and added fats. This experiment was carried out to examine the effects of breed and dietary fat on pigmeat quality characteristics.

Genetic variation in pig meat composition and quality offers the possibility of manipulating both between and within line composition in order to Improve the end product. The extent of this variation has been evaluated on batches of PIC pigs sent to the Meat and Livestock Commission for carcass assessment and full side dissection. In the last two years, hind loin samples from these carcasses have gone to the Institute of Food Research, Bristol for taste panel assessment, chemical analysis, and measurements of fat firmness and androstenone concentration.

289 entire males of eight pure lines (20-55 per line) were slaughtered at 90-100 kg liveweight following performance test on ad libitum feeding from 33 kg. The ration contained 13.8 MJ DE, 200g crude protein and 10g lysine per kg. Standard MLC dissection procedures were followed. At IFR, the SOXHLET method was used to determine the concentrations of extractable fat, moisture, total nitrogen and ash In the m. longissimus.

The chemical composition of pig backfat determines its physical properties of firmness and cohesiveness as well as its nutritional value. The firmness of the tissue depends upon its content of saturated fatty acids, particularly stearic, which make it harder; and unsaturated fatty acids, particularly linoleic, which make it softer. Cohesiveness depends upon the connective tissue and fat content and the compositon of these; soft fat and low cohesiveness frequently being found together. Nutritional value may be judged by the energy content of the tissue, which increases in proportion to its lipid content, or by the ratio of polyunsaturated fatty acids to saturated fatty acids (P:S ratio), used by COMA to indicate the desirability of the fat as a risk factor for cardiovascular disease. There is evidence that as fatness has been reduced in British pigs, composition has changed with consequences for these characteristics.