In order to investigate the antagonism between meat quantity and quality, halothane-positive (HP) and -negative (HN) Belgian Landrace pigs (B) and Pietrain × Belgian Landrace crosses (PB) were compared for several carcass and meat quality traits. They originated from three commercial farms and were slaughtered in a commercial abattoir. Carcass quality was determined by a SKGlI-device. Meat quality traits were measured on the warm and cold carcass, and on a loin slice. HP and PB pigs showed better carcass quality, and inferior meat quality, compared with HN and B pigs respectively. No significant halothane sensitivity × breed interaction was apparent for most traits. Sex did not affect meat quality. Slaughter day variance was considerable. The inverse relationship between lean content or conformation score and meat quality was generally more pronounced in the HP group compared to the HN group (except for drip and cooking losses). Irrespective of halothane status, carcass conformational score was more negatively related to meat quality than was lean content.

The intestinal production of skatole and its deposition in backfat was investigated in 35 uncastrated crossbred male pigs. The pigs were fed five purified non-commercial diets containing either casein or brewers yeast slurry as protein source. The yeast slurry diet was used alone or supplemented with either wheat bran (200 g/kg), sugar-beet pulp (200 g/kg), or soya oil (100 g/kg).

Skatole concentrations in backfat, and in digesta in different sections of the gastro-intestinal tract were measured at slaughter (mean weight 112 kg). There were large variations in skatole concentrations in the hind gut of different animals given the same diet. Although there was some correlation between skatole in intestinal contents and deposition in adipose tissue, there were also large variations between individual animals in their response to intestinal skatole. Nevertheless, there was a clear effect of diet on both intestinal skatole production and skatole deposition in backfat. The use of casein as a protein source decreased microbial skatole production, the total amount in the gut, and the concentration in the backfat. Addition of sugar-beet pulp to the yeast slurry diet increased microbial activity in the intestine (measured as ATP content, concentration of short-chain fatty acids, and lowering of digesta pH). There was a decreased rate of skatole production during in vitro incubations of intestinal content, and less skatole in the hind gut and backfat.

In vitro fermentations of freeze-dried Heal effluent inoculated with faecal bacteria, and addition of substrates to in vitro incubations of intestinal contents, demonstrated that tryptophan availability rather than microbial activity was the limiting factor for skatole production.

The results show that skatole production depends on the amount of protein entering the hind gut and the proteolytic activity of the intestinal microbiota. Protein fermentation in the hind gut can be decreased either by using more readily digestible protein sources (for example casein rather than yeast slurry) which reduce the amount of protein passing through to the hind gut, or by adding an alternative energy source which is more readily metabolized by the hind gut microbiota (for example supplementation of the yeast slurry diet with sugar-beet pulp). This provides a basis for the rational design of diets which will decrease skatole concentrations in the carcass.

Forty days after mating, 16 pregnant sows were randomly allocated to two diets containing either sugar-beet pulp (SBP) or wheat straw (WS) each offered at two levels (1·0 or 1·5 × maintenance energy requirement (M), where M = 460 kJ digestible energy (DE) per kg0·75 per day). Diets were iso-nitrogenous, and contained similar levels of DE together with 260 g non-starch polysaccharides (NSP) per kg dry matter (DM) largely derived from either the SBP or the WS. A 7-day NSP and DM balance was made between day 60 and 100 of gestation. During lactation sows had ad libitum access to a conventional sow diet which contained neither SBP or WS.

Outputs of both fresh and dry faeces from sows given diet WS were significantly greater than the outputs from sows given the corresponding SBP diets (P <0·05), and outputs were significantly greater at the higher feeding level for both diets (P < 0·05). There was a tendency for higher urinary outputs from sows given diet WS, but these were variable and not significantly different from those from sows given diet SBP. The apparent digestibility and retention of DM was significantly greater for the SBP diet than for diet WS but were not significantly affected by feeding level. The apparent digestibilities of the total NSP and each of the individual constituent monomers were significantly higher for diet SBP than for diet WS (P < 0·001), but were independent of feeding level (P> 0·05). Xylose was the most poorly digested NSP constituent from both diets. Apparent digestibility coefficients for the remaining NSP constituents in diet SBP were > 0·8 and were > 0·52 in diet WS, with the uronic acids and mannose being the most highly digested NSP fractions from diets SBP and WS respectively.

Computerized food intake recording systems of various designs are used by research, centres and breeding companies to monitor the individual food intake of pigs kept in groups. In the present experiment, three feeder designs are compared in order to estimate the effect on performance and feeding behaviour. Ninety entire male pigs (34 (s.e. 0·6) kg) were allocated in three replicates to pens of 10 pigs; each pen containing one of three different feeder entrance designs: low (head-guard), medium (full-length standard race), and high (enclosed pneumatic race) protection against disturbance of the feeding pig. No significant differences were found between treatments in daily food intake, daily live-weight gain, food conversion ratio, number of visits per day and daily feeder occupation. Pigs with access to an enclosed race had longer visits than pigs on the two other treatments, and they also ate more per visit (4·8, 4·8 and 6·2 (s.e.d. = 0·37) min per visit; 172, 157, and 202 (s.e.d. = 11·1) g per visit; means of low, medium and high protection, respectively). The enclosed race was not only the most protective, it was also the most difficult to enter, and this decreased accessibility of the food may have given rise to the changed feeding pattern displayed by pigs using this type of race. Access to a feeder with low protection resulted in a faster rate of eating (36·9, 33·2, and 32·8 (s.e.d. = 0·82) g/min; means of low, medium and high protection, respectively) indicative of a more forced feeding behaviour.

A study was conducted to evaluate the effect of decreasing age of puberty on lifetime productivity in sows. Two lines of gilts from the Nebraska Gene Pool population were used in this study: a line that had been selected for decreased age at puberty (AP) and a line in which selection had been random (RS). The study was conducted in two parts. In part one, 75 gilts were mated at second oestrus and the productivity measured over five parities. A second experiment utilizing 68 gilts was conducted to provide further data for comparing litter size at parity 1, and also to compare ovulation rates in the two lines at second oestrus. Results showed that litter size was similar in both lines across parities. After five parities the percentage of sows farrowing relative to parity 1 was 58-8% for the AP line but only 39·4% for the RS line (P = 0·17). Litter birth weight, litter size and weight at 21 days, number weaned, and lactation food consumption were similar for both lines. Lactation weight loss was not significantly different between the two lines (60·9 (s.e. 5·9) v. 527 (s.e. 5·0) kg, for RS and AP gilts, respectively) but was consistent with the slightly longer weaning to remating intervals in the RS line (7·8 (s.e. 0·7) v. 6·6 (s.e. 0·7) days, P = 0·22). Ovulation rate at second oestrus did not differ between the two lines (14·1 (s.e. 0·9) v. 14·3 (s.e. 0·5), for RS and AP gilts, respectively). The regression of mean accumulative productivity on time was in favour of the AP line (P = 0·05). These results suggest that reproductive performance is not impaired in gilts which have been selected to reach puberty at earlier ages, and productivity at a specific age may be enhanced.

Six sport horses were given 1·26 times the measured maintenance energy requirement (MEm) from each of the four following diets: H1, meadow hay in the long form (organic matter digestibility OMD = 0·541); HMI, 700g/kg the same hay and 300 g/kg pelleted maize; HSBPI, 600g/kg hay and 400g/kg pelleted dehydrated sugar-beet pulp; SCFI, 500g/kg wheat straw and 500g/kg pelleted compound food (experiment 1). In experiment 2, eight sport horses were equipped with a portable device for recording feeding behaviour and fed at 1·31 MEm diet HI (meadow hay in the long form: OMD = 0·574).Circadian energy expenditure (EE) of horses was determined by indirect calorimetry using two large open-circuit respiration chambers. Horses were continuously standing. Increase in metabolic rate (IMR) during eating was calculated from the difference between the mean EE obtained during each eatingperiod and the corresponding resting EE. The mean daily ingestion rate of hay H2 amounted to 148 (s.d. 27)mg dry matter per kg metabolic body weight per min. IMR during the two main meals averaged 0·388 (s.d. 0·059) and was not significantly different between diets H1, H2, HM1 and SCF1. Expressed per kg dry matter intake, energy cost of eating (ECE) was similar for diets H2, H1 and SCF1 but significantly lower for HSBP1 and HM1 (P<0·05). ECE of simple foods was calculated from those of the diets and of hay: proportionately 0·010, 0·042, 0·102 and 0·285 metabolizable energy intake for pelleted maize, pelleted SBP, long hay and wheat straw, respectively.

The genotype with feeding regime interaction was examined by testing pigs from four selection groups on both ad libitum and restricted feeding regimes. Within each selection group, there were high, low and control lines, which had been selected for lean food conversion ratio (LFC), daily food intake (DFI) or lean growth rate on ad libitum (LGA) or on restricted (LGS) feeding, in Large White-Edinburgh (LW) and Landrace-Wye (LR) populations. There were 1187 LW pigs and 768 LR pigs in the study, with 344 LW and 133 LR pigs tested on the alternative feeding regime.

In the LW population, pigs in the high LGS line grew significantly faster than the high LGA and LFC lines with ad libitum feeding (919 v. 847 and 786 (s.e.d. 31) g/day), but had similar food conversion ratios and backfat depths. The high LGS and high DFI lines were similar for growth rate, daily food intake and food conversion ratio, but backfat depth was significantly lower in the high LGS line than in the high DFI line (12·0 v. 25·9 (s.e.d. 0·7) mm). On restricting feeding, the rankings of the selection lines for growth rate, food conversion ratio and mid-back fat depth were broadly similar to those with ad libitum feeding, except for the high LFC line. In the LR population, the high LGS, LGA and LFC lines did not differ significantly in growth rate, daily food intake, food conversion ratio and backfat depth within either the ad libitum or restricted feeding regimes. Growth rate of the high LGS line was similar to the high DFI line on ad libitum feeding (828 v. 836 (s.e.d. 40) g/day), but significantly higher on restricted feeding (704 v. 636 (s.e.d. 23) g/day). On both feeding regimes, food conversion ratio and backfat depth were significantly lower in the high LGS line compared with the high DFI line.

In the LW population, the genetic correlation between feeding regimes for growth rate was significantly less than one (0·4 (s.e. 0·20)), but was not significantly different from unity (0·8 (s.e. 0·14)) for backfat depths. Based on the performance test results, selection for lean growth with testing on a restricted feeding regime may be preferable to testing animals on an ad libitum feeding regime.

The requirement for a training period prior to a choice feeding regime was assessed using 36 weaned piglets whose initial live weight was 6·2 (s.d. 1·21) kg. Two foods (H and L) were offered ad libitum as the choice and these were similar in energy but differed in crude protein (CP) concentration (291 g/kg and 155 g/kg fresh matter respectively). The pigs ivere subjected to one of three training treatments: treatment ALTERNATE allowed piglets the two foods separately on alternate days for 6 days, followed by a free choice of the two foods; treatment THREE allowed 3 days of one food followed by 3 days of the other prior to the free choice; treatment CHOICE gave the animals free choice immediately. Piglets on a fourth treatment, CONTROL, were given a single food M (242 g CP per kg fresh food) as a control. Weight gain (0·60, 0·59, 0·59 and 0·61 (s.e. 0·005) kg/day) and food intake (0·776, 0·752, 0·771 and 0·747 (s.e. 0·010) kg/day) did not differ significantly between treatments ALTERNATE, THREE, CHOICE and CONTROL respectively in the 19-day post-training period. A significant difference was seen in the protein consumption (0·145, 0·150, 0·139 and 0·177 (s.e. 0·005) kg/day). This together with a tendency for the proportion of food H selected to decline as the growth period progressed, indicated that newly weaned piglets are capable of regulating their protein intake when offered a free choice of two foods differing in their CP concentration, without a necessity for an initial training period.

Quantitive collection of night-time urine every 2nd week was used to elucidate the temporal relationship between changes in melatonin production, weight gain, and priming of the winter pelage under natural light conditions and under a long photoperiod (18L: 6D) imposed at different times in four groups of female mink during autumn. In mink maintained outdoors under the natural photoperiod (group 1), melatonin excretion was 1·80 (s.d. 0·80) ng per night (no. = 3) at the beginning of September, thereafter it began to decrease slowly until November when it was only 0·62 (s.d. 0·32) ng per night. These mink had a normal autumn moult during the first half of October and the winter pelage was mature at the end of November. When mink maintained outdoors were transferred to 18L: 6D on 7 September (group 2), excretion of melatonin decreased promptly, autumn moult was disrupted and winter fur priming delayed. Long photoperiod after mid October (group 3), did not interfere with pelage maturation despite the decrease in melatonin production. Mink implanted with melatonin on 14 July (group 4) showed very high melatonin excretion in early September. In these animals the winter pelage growth was unaffected by the long-day conditions; the pelage matured in mid October. Body weight increased in mink of all groups during autumn. This increase levelled off or a weight loss (group 2) was seen along with the final hair maturation. Activation of hair follicles occurred during a 4 to 6 week period. According to these results, melatonin is the photoperiodic signal to autumnal weight increase and autumn moult but seems not to be necessary for later pelage growth and maturation.

Twenty crossbred (Large Wliite × Piétrain) boars were used to investigate the effect of energy intake (0·71, 0·80, 0·90, 1·00 ad libitum) and body weight (BW) on growth performance, and rates of protein (PD) and lipid (LD) deposition between 40 and 100 kg BW. Daily crude protein intake was kept constant. Total PD and LD were measured according to the comparative slaughter technique (CST) during total experiment and according to nitrogen and energy balance technique at 45, 65, 80 and 94 kg mean BW. Average daily gain increased linearly with metabolizable energy (ME) intake (+36 g/MJ ME) whereas food conversion ratio was not affected by energy level (28·0 M] ME per kg BW gain). Daily PD increased from 126 to 171 g/day, and LD from 70 to 187 glday between 0·71 ad libitum and ad libitum ME intake. Maintenance ME requirement was constant when expressed per kg BW'60 (992 kJ/day). PD varied with ME intake above maintenance (MEp) according to a linear-plateau relationship. The slope decreased with BW (+11·5 g/MJ MEp at 65 kg BW and +9·0 g/MJ MEp at 94 kg BW). LD was linearly related to MEp (+16 g/M} MEp). The LD: PD ratio in marginal empty BW gain was constant within BW class, but increased from 1/5 to 1/9 between 65 and 94 kg BW.

Two experiments were performed to examine the effects of immunoneutralizing PMSG at the onset of oestrus on the reproductive performance of sows. In experiment 1, 12 multiparous sows received 750 i.u. PMSG at weaning and six sozus acted as controls and were injected with saline. At 84 h after PMSG injection, all sows received an injection of 500 i.u. human chorionic gonadotropin (hCG) and six of the PMSG-treated sows also received an injection of 750 i.u. of a monoclonal anti-PMSG serum. The ovaries of all sows were examined by real time ultrasonography at 60-min intervals from 36 to 48 h after hCG injection for evidence of ovulation. In sows observed to ovulate, there was no significant effect of treatment on the interval from hCG injection to the start of ovulation, the duration of ovulation or subsequent litter size. In experiment 2, 253 primiparous sows received injections at weaning of 750 i.u. PMSG (no. = 134), 400 i.u. PMSG plus 200 i.u. hCG (no. = 69) or served as controls (no. = 50). At breeding, 67 of the PMSG-treated sows received an injection of 750 i.u. of monoclonal anti-PMSG serum.

More gonadotropin-treated than control sows were bred by 7 days after weaning (P < 0·05). Farrowing rates were higher in sows receiving the PMSG followed by anti-PMSG and PMSG plus hCG than in controls (P < 0·05), with those receiving PMSG alone being intermediate. There was no effect of treatment on subsequent litter sizes. These data indicate that the reproductive performance of primiparous sows may be improved by gonadotropin administration at the time of weaning. However, there was no advantage to using any particular hormone combination or anti-PMSG.

On the basis of their respective metabolizable energy contents, supplemental marine oil was partially replaced with a maize starch/dextrin mixture in diets containing approximately 500 g crude protein per kg food thus lowering the total dietary lipid concentration from 141·6 to 100·9 g/kg. The basal diets were then supplemented with thiamin hydrochloride at 0·5, 5·0 and 10·0 mg/kg food to produce six test diets in all. After 182 days of feeding, the fish given the diets containing the higher lipid content with a thiamin supplement of 10·0 mg/kg had shown significantly better growth and food utilization (food conversion efficiency and apparent net protein utilization) than the fish presented with the remaining five diets. Thiamin supplements of 5 mg/kg or less resulted in poorer performance amongst the fish given the high lipid diets. The fish given all three of the low oil diets performed poorly by comparison with those given the high lipid, high thiamin diet and performance was comparable with that of the fish given the high lipid diets containing thiamin at 5 mg/kg or less. Proximate carcass composition in terms of moisture, protein and lipid was unaffected in response to diet. Glycogen accumulation in the liver was significantly elevated amongst the fish given the low lipid diet where the thiamin supplement was 5·0 mg/kg or more. The haematology of the fish was not significantly altered in response to diet although elevated haematocrit was associated with decreasing thiamin supplementation. It would appear that for the seabream, lipid and carbohydrate are not exchangeable on the basis of their metabolizable energy content. When given high lipid diets the thiamin requirement of the seabream is in excess of 5·0 mg/kg and increasing the thiamin supplement to 10 mg/kg in high carbohydrate diets made no impact on performance.

A pedigree originally designed for pig genome mapping was used in order to study carcass and muscle development as well as meat quality of F2-crosses between the European Wild Pig and the domestic Large White pig (no. = 191). As a marker for the influence of genes inherited from the ‘wild’ and domestic grandparents, grouping based on the length of the small intestine was used. The pigs were also typed for genetic polymorphism at the calcium release channel (CRO locus controlling halothane susceptibility in pigs, and one of the Wild boars was found to be a carrier of the halothane mutation. At assessment, the carcasses were divided into cuts, the back and ham were defatted, and m. longissimus dorsi and the large muscles of the ham were weighed separately.

Wlien grouped according to length of the small intestine, those animals with a short small intestine were more similar to Wild Pig, e.g. they were older at slaughter and had a slower growth rate than the other group. Their carcasses contained less lean meat, more flare fat and more subcutaneous fat. No difference in meat quality could be discerned between the groups, except for a tendency to greater pigment content and higher shear force value in the group with a short small intestine.

The effect of the halothane mutation at the CRC locus was very prominent, although no animals had the gene in homozygous form. Carriers of the gene were leaner and had a higher reflectance value, lower water-holding capacity, lower pHu, higher protein denaturation and higher shear force value.

The relationships between reflectance values measured with an EEL reflectometer, and C1ELAB L* a* b* coordinates measured with a tristimulus meter, were determined using 572 samples of pork m. longissimus dorsi. These samples covered the muscle colour/condition range from extreme pale, soft, exudative (PSE) to extreme dark, firm, dry (DFD). There was a good (r = 0·91) and slightly curvilinear relationship between L* value and reflectance, the other relationships being significantly poorer. Based on these findings, pork loins with L* values between 49 and 60 would on average have consistently good visual appeal using criteria in the Meat and Livestock Commission blueprint for quality pork.

The growth hormone-insulin-like growth factor (GH-IGF) axis is involved in the control of postnatal growth in all animals studied to date. At birth, blood levels of IGF-1 are low, although levels of GH are high. Thus a switching occurs during the postnatal period, which involves an increase in liver GH-receptors (GHR). This study investigates the changes in serum IGF-1 and IGF-1 and GHR mRNA in liver and skeletal muscle of growing pigs. The period from birth to 20 days of age showed a gradual increase in both IGF-1 and GHR mRNA expression by the liver, thus accounting for the gradual increase in serum IGF-1. The IGF-1 mRNA expressed was found to be predominantly class 1 transcripts with very few class 2 transcripts. There was a plateau of liver IGF-1 mRNA levels after 20 days and up to 140 days, even though the expression of GHR mRNA continued to increase. The levels of expression of the two genes were found to correlate in the first 20-day period (r = 0·76, P < 0·005), but not in the later period (r = 0·44, P > 0·05).

Levels of expression of both genes in the LD muscle were highly variable, with no age related changes being observed. However, a significant negative correlation of expression of the two genes was observed (R = 0·60, P < 0·001), with the correlation still being significant in the two age periods.

The data are consistent with a likely initial dependence for postnatal growth upon GH-stimulated IGF-1 mRNA expression by the liver, up to 20 days of age. After this time, hepatic expression of IGF-1 mRNA reaches a plateau, even though the serum IGF-1 and hepatic GHR mRNA levels continue to rise. A possible explanation for this could be an increase in either turn-over or stability of IGF-1 mRNA, giving rise to increased levels of peptide with no apparent change in mRNA level. Another possibility is that an increased expression/production of the IGF-binding proteins leads to an increase in the half-life of the peptide in the circulation.

Data from experimental programmes designed to investigate the effect of chemical structure of fats upon their apparent digestible energy (DE) value for pigs were subjected to regression analysis. For growing pigs, over the approximate live-weight range 30 to 90 kg, 25 data points were available, with fats evaluated having a range in the ratio of unsaturated to saturated fatty acids (U/S) from 0·66 to 15·67 and in free fatty acid (FFA) content from 8 to 818 g/kg. Sixteen data points were available for young pigs of approximately 12 kg live weight with a range in U/S from 0·62 to 5·71 and in FFA content from 54 to 756 g/kg. The wide range of values for U/S and FFA content had been obtained by blending different fats and, therefore, represented both the range and extremes likely to be found in the formulation of pig diets. Derivation of prediction equations for DE were based upon a series of non-linear regression analyses employing, in sequence, U/S, U/S + FFA content and U/S × FFA content. The DE offats could be predicted from U/S and FFA content with equations accounting for 0·802 and 0·768 of the variation in DE values for growing and young pigs respectively. The most appropriate equation for pigs of all live weights employed U/S and FFA content additively (U/S + FFA content). The equation for growing pigs was DE (MJ/kg) = 36·898 – (0·0046FFA (g/kg)) — 7·33e(–0·906U/S) and for young pigs was DE (MJ/kg) = 37·890 — (0·0051FFA (g/kg)) –8·20e(–0·515U/S). Comparisons revealed that differences between the two age groups, with lower values achieved with younger pigs, -were more pronounced the lower U/S and the higher FFA content of the fat.

Two lines of pigs that had been selected for five generations for lean tissue growth rate (LTGR) on a high (HP) or low (LP) protein diet were evaluated on a commercial diet (165 g crude protein per kg diet). The growth characteristics of 534 animals were measured, and carcass data were obtained on 405 animals. Differences between lines were tested for significance taking genetic drift into account. The animals from the HP-line grew faster both before and during the test and were 6·5 days younger at slaughter than the LP-line pigs. The HP-line pigs had a higher lean content (587 v. 558 g/kg) and a thinner backfat layer (17·8 v. 22·7 mm) than the LP-line. LTGR was higher in the HP-line (374 v. 347 g/day). No significant differences between lines were found in meat quality or in the incidence of osteochondrosis in elbow or knee. The realized differences between lines confirm that selection for LTGR on a high protein diet was more effective in improving both leanness and growth rate compared with selection for LTGR on a low protein diet.

The effect of nutritional growth restriction on reproductive development in red deer stags reared in constant photoperiod was investigated and the correlation between reproductive status and circulating concentrations of growth hormone (GH) and insulin-like growth factor-1 (IGF-1) examined.

Stags were reared from birth in constant photoperiod (12 h light: 12 h dark). They were offered a ‘complete diet’ ad libitum until they reached 52-5 kg live weight (LW) and were then maintained at this LWby restricting daily food dry-matter intake (DMI)for either a long (LR, 26 to 51 weeks of age, no. = 5) or short (SR, 21 to 33 weeks, no. = 6) period before being returned to ad libitum feeding.

Relative to SR stags, antlers hardened later in LR stags (72·0 v. 57·5 weeks of age, P < 0·001); sustained elevations in plasma testosterone also began later (55·2 v. 38·5 weeks, P < 0·001) but at lower LW (54·0 v. 60·6 kg, P < 0·05). In both groups, the testosterone rise followed the return to ad libitum food by 4 to 5 weeks. Plasma IGF-1 was closely correlated with DMI (LR, r = 0·84, P < 0·001; SR, r = 0-93, P < 0·001) and with plasma testosterone (LR, r = 0·42, P < 0·001; SR, r = 0·38, P < 0·01). Also the increase in plasma IGF-1 preceded that of testosterone (by 2·8 (s.e. 0·94) weeks) and was associated with a transient plasma GH peak (P < 0·05) and elevated LH concentrations (SR, P < 0·01; LR, P < 0·05).

The timing of reproductive development in growth-restricted male red deer in constant photoperiod may therefore be more sensitive to DMI than LW, and changes in plasma IGF-1 concentrations are consistent with a putative permissive role in relaying this information.