The influence of types of roughage, barley straw (diet B) versus lucerne hay (diet L), on the patho-physiology of a T. congolense infection was compared in eight pairs of Scottish Blackface male twin lambs. One animal of each twin pair was infected and the other used as a pair-fed control. Voluntary food intake, body weight, digestive function, various blood haematological and biochemical measurements were made.

Voluntary organic matter intake decreased significantly after the T. congolense infection, the decrease being greater in the diet L group than in the diet B group lambs (P < 0·01). The apparent digestibility coefficients of crude protein and organic matter were significantly lower in the infected lambs (P < 0·01). Mean retention time of the roughage through the digestive tract in the animals given barley straw was significantly longer (P < 0·05) due to a lower rumen outflow rate constant (P < 0·01). Infection resulted in longer mean retention times (P < 0·01).

Packed cell volume (PCV) was significantly lower before infection in the animals given diet B (P < 0·01). After infection, diet (P < 0·01) and infection (P < 0·01) had an additive effect on PCV. The anaemia was both macrocytic (P < 0·05) and hypochromic (P < 0·01).

Diet B resulted in higher plasma cholesterol (P < 0·05), but lower plasma urea (P < 0·01) and albumin (P < 0·01) concentrations before infection than diet L. The T. congolense infection significantly lowered plasma cholesterol (P < 0·01) and increased plasma urea (P < 0·01) concentrations compared with the uninfected controls. Plasma albumin concentrations decreased, but were more affected by nutrition (P < 0·01) than by infection (P < 0·05).

It ivas concluded that the patho-physiological effects of the T. congolense infection in the Scottish Blackface lambs were affected by the type of roughage offered, but that these effects were additive rather than interactive to the effects of infection.

The efficiency of utilization of protein for retention was analysed in pre-ruminant kid goats of the Granadina breed. Sixty male kids were used. Six were slaughtered at birth and the remaining 54 were offered different protein and fat intakes using nine different milk replacers. The protein concentrations were 200, 240 and 280g/kg dry matter (DM) and those of fat were 200, 240 and 280 g/kg DM. Animals were maintained on experiment until they were 60 days old. All were slaughtered on day 61. Nitrogen (N) balance trials were performed during the last 8 days of the 1st and 2nd months. Body composition of the animals slaughtered at birth and at 61 days were determined. Rates of energy retained as protein and as fat were determined (kJ/kg M0·75 per day) and the corresponding rates of metabolizable energy intake as protein and as fat (kJ/kg M0·75 per day) estimated.

Once the relationships between the rates ofN retained and those of digestible N ingested had been established, it was evident that by increasing the protein content of the diet the efficiency of protein retention was decreased. In contrast, increasing the fat content of the milk replacer increased the efficiency of protein retention. The latter effect was noted for the milk replacers containing the high and medium levels of protein but not for those that contained the lowest level of protein, indicating that the level of protein was then the limiting factor. Having recorded this protein-sparing effect of the fat, the results obtained from the slaughter trials were used to develop generalized equations expressing the rates of energy retention in the form of protein or fat as a function of the rates of metabolizable energy intake achieved as both protein and fat. From the analysis of these equations conclusions are drawn about the variable contribution to protein retention in these animals of energy ingested as fat. This contribution depended on the energy intake achieved both in the form of protein and in the form of fat.

Texel (T) and Suffolk (S) sired ram, wether and ewe lambs (no = 180) were kept at grass with their dams until weaned at 20 weeks and then taken to slaughter weights of 40, 44 and 48 kg, also at grass. Sex type, but not sire breed, affected lamb growth rate (rams 293, wethers 253, ewes 224 g/day; P < 0·001). Both T and S ewe lambs were fatter at slaughter in all fat depots compared with their ram and wether siblings such that rams could be slaughtered at a calculated 7·7 kg greater live weight than ewes at equal carcass fat cover. T carcasses were greater than S carcasses in eye-muscle area (793 v. 732 mm2; P < 0·001) and killing-out proportion (481 v. 476 g/kg; P < 0·05) but not in any fat measurement. Slaughter weight influenced killing-out proportion (P < 0·001) and all fat measurements (P < 0·01) but did not significantly affect eye-muscle area.

Mean serum insulin-like growth factor-1 (IGF-1) concentrations (μig/l), determined during weeks 8,11, 14, 17 and 20 in a balanced subset of 84 lambs, were higher in T than in S lambs (P < 0·05), in singles than in twins (P < 0·01; rams and wethers only) and in rams than in either wethers or ewes (P < 0·001). Mean serum IGF-1 concentration decreased between week 8 and week 20 with a greater rate of decline in singles than in twins (P < 0·001). IGF-1 was more strongly correlated with live weight at 8 weeks (r = 0·629; P< 0·001) than at 20 weeks (r = 0·293; P < 0·05). Mean IGF-1 (weeks 8 to 20) was correlated with rate of live-weight change (r = 0·576; P < 0·001). Significant differences for T and S lambs were found in the relationships between mean serum IGF-1 (weeks 8 to 20) and daily live-weight gain (weeks 8 to 20) and between mean IGF-1 and eye-muscle area at slaughter. Metabolite concentrations differed little between sire breeds and not at all between sex types.

Ewe live iveights were recorded 4 weeks prior to mating, at the beginning of mating and 22 to 23 days later over a period of 3 years in a flock of some 300 breeding ewes comprising approximately equal numbers of Australian Merino, Ideal (Polwarth), Merilin and Corriedale breeds in a pastorally based grazing system in Uruguay. Multiple-bearing ewes were generally heavier than single-bearing ewes which in turn were heavier than ewes which did not conceive, these differences being greatest in 3- and 4-year-old ewes (i.e. in their second and third breeding seasons). Body condition scores of non-pregnant ewes were lower than those of pregnant ewes, particularly in the 3-and 4-year-old age groups. Ewe live weights achieved prior to, during and at the end of the mating period and the body condition score achieved 4 weeks prior to mating all had significant influences on the number of lambs born (P < 0·01) but there were no significant effects of changes in either live weight or body condition over the 4 weeks prior to mating or during the mating period. The effect of body condition score over the range from 2·0 to 4·0 was to increase the proportions of single- and multiple-bearing ewes and to decrease the proportion of non-pregnant ewes such that the number of lambs born per ewe mated increased from 0·94 to 1·38. Fleece weights differed significantly between breeds, Corriedales having the heaviest fleeces and Merilins the lightest (4·26 and 3·22 kg respectively). Wool production was also significantly and positively affected by age (P < 0·01) and by ewe weight at mating (P < 0·01). The results demonstrate the importance of giving preferential nutritional treatment to younger ewes to ensure a satisfactory subsequent lambing performance and improved wool production.

Eleven maize silages with crude protein (CP) and neutral detergent fibre (NDF) ranging from 77 to 93 and 359 to 542 g/kg dry matter (DM) respectively, were used to study the relationship between ear content, chemical composition, fermentative characteristics, in vitro DM digestibility and ruminal degradation characteristics, on the one hand, and the voluntary DM intake by sheep or in vivo organic matter apparent digestibility (OM digestibility), on the other.

The silages were offered ad libitum to mature ewes given a daily supplement of 85 g of soya-bean meal. DM intake varied from 41·1 to 68·6 g DM per kg M0·75 daily. OM digestibility and NDF apparent digestibility were measured, using the same ewes in a period subsequent to that of voluntary intake measurement. The silages, in this case, were offered at a feeding level of 1·2 maintenance. OM digestibility and NDF apparent digestibility ranged from 0·622 to 0·757 and from 0·377 to 0·605, respectively. Rumen DM disappearance was measured by incubating samples in nylon bags in the rumen of three silage-fed rumen-cannulated wethers for 3, 6, 12, 24, 48 and 72 h and by fitting the exponential model to the results. Potential degradabilities (defined as a + b) for DM ranged from 728 to 815 g/kg.

Accurate prediction of DM intake (r = 0·93; P < 0·01; residual s.d. = 3·9) and OM digestibility (r = 0·86; P < 0·01; residual s.d. = 0·022) was achieved using the soluble fraction (a) and the insoluble but fermentable matter (B) and the insoluble but potentially degradable fraction (b), respectively. However, looking for a compromise between accuracy and simplicity, reliability and inexpensiveness, ear content is proposed as a predictor of OM digestibility (r = 0·85; P < 0·01) and the pH and acetic acid concentration of the silages may be used as a predictor of DM intake (r = 0·80; P < 0·05).

A flock of Cheviot ewes carrying the Thoka gene for fecundity was established in southern Scotland through the importation of frozen semen from two Icelandic rams. Ewes considered to be probable carriers of the Thoka gene were identified on the basis of measurements of ovulation rate as juveniles at 1·5 years of age and again as adults. Analysis of 3 years' records of 8926 Cheviot lambings and lambings of 351 Icelandic × Cheviot ewes considered to be probable carriers showed that fecundity increased with age in both genotypes, the number of lambs born per ewe mated being 1·07, 1·19, 1·31 and 1·41 in the Cheviots and 1·55, 1·74, 2·33 and 2·30 in the Icelandic-Cheviot crosses at first to fourth lambings respectively. The apparent effect of the crossbreeding on fecundity thus also increased with age, values at first to fourth lambings being 0·48, 0·55, 1·02 and 0·89 lambs per ewe mated, giving a weighted mean value of 0·61 (1·20 v. 1·81 lambs per ewe mated in Cheviot and Icelandic × Cheviot ewes respectively). There was a positive effect of the proportion of Icelandic ancestry on the number of lambs born per ewe mated and thus the observed increases in fecundity, although attributed principally to the effects of the Thoka gene, are also due in part to other genetic factors introduced from the Icelandic sheep in the crossbreeding programme. Lamb mortality to 6 weeks of age was only marginally higher in Icelandic × Cheviots (0·10) than in Cheviots (0·08). The increase in fecundity was achieved without an excessive proportion of large litters (<0·02 of probable carriers gave birth to quadruplets). The results demonstrate that the introduction of the Thoka gene to breeds such as the Cheviot can increase fecundity and hence the potential for more efficient lamb production.

The objective of this study was to evaluate the influences of age and condition score on the live weight of ewes of three Greek dairy breeds. Boutsko (no. = 225), Serres (no. = 292) and Karagouniko (no. = 301) ewes from individually recorded purebred flocks were weighed (±0·5 kg) and condition scored, on a six-point scale, to the nearest 0·5 unit. Within each breed and age group the relationship between live weight and condition score was derived by linear regression. There was a highly significant relationship between condition score and live weight in all of the groups (P < 0·01). Live weight, adjusted to a standard condition score, increased with increasing age up to 3·5 years; beyond this age there was no effect of age on condition score. The live weight and condition score data for ages 3·5 years and upwards were used to derive a single regression between live weight and condition score for each breed. This provides a means to estimate adult live weights standardized to a given condition score. The values of the regression coefficients were directly proportional to the breed mature weight; on average the increase in live weight associated with a unit of condition score was 0·129 kg/kg of mature weight for the three breeds studied. Mature weight was estimated as the weight at a condition score of 5. Using published information, a similar value was found to apply to a wide range of sheep breeds and also to cattle. This robust value permits the live-weight change associated with a unit of condition score to be calculated, for any breed.

Divergent breeding lines of Romney sheep, selected as lambs for consistently low or high faecal worm egg count (FEC) following natural multispecific challenge by nematode parasites, have been maintained at Wallaceville Animal Research Centre since 1979. From the start of the trial until 1992, 821 and 736 experimental lambs in lines selected for increased resistance (R) and increased susceptibility (S), respectively, were generated, with the use of 44 different sires. In order to assess genetic responses to selection, FEC and productivity data were analysed using restricted maximum likelihood procedures. By 1988 the two lines had diverged in average loge (FEC+100) by 0·67 log units, and by 1992 divergence had increased to 1·48 log units, representing 2·90 genetic standard deviations of divergence. No significant correlated responses were observed in live weights. However, by 1992 the mean score for breech soiling (dags) in the R line was proportionally 0·41 greater than in the S line (F < 0·001). Yearling fleece weight was proportionally 0·15 greater in S-line than in R-line animals when grazed together under identical levels of challenge (P < 0·001) but the lines did not differ significantly in fleece weight when they were grazed apart. The R line had significantly higher reproductive success than the S line (P < 0·05), as measured by lambs weaned per ewe mated (1·01 v. 0·92, respectively). It is concluded that selective breeding can change the degree of resistance or susceptibility to nematode infection in Romney sheep, and selection for productivity needs to be continued at the same time in any practical breeding programme.

Juice was extracted from a ryegrass silage after fermentation times of 0, 51 or 291 h. Three solutions of D/L lactic acid were prepared to have the same neutralizing values (NV) as the silage juices. Experiment A measured the mtakes by sheep of dried silage residues remaining after juice extraction. Experiment B measured the effect of adding each of the juices and lactic acid solutions (1·5 l/kg) on intake of unmolassed sugar-beet nuts. Intakes were measured daily and also over 3 h following an overnight fast.

Fermentation time had no effect on the composition or intake of the residues (P < 0·05). Increasing fermentation time from 0 to 51 to 291 h reduced silage juice pH (5·07, 4·96 and 4·10), increased lactic acid (gfl 6·2, 7·1, 18·7), NV (meq/l 29, 40, 157) and osmolality (mosmol/l 1000, 1010, 1390). Corresponding values for the lactic acid solutions were 2·82, 2·74, 2·41 (pH), 3·1, 4·3,18·3 (lactic), 26, 38,154 (NV) and 32, 42,176 (osmolality).

Total daily DM intake (g/kg live weight1·473) was unaffected by NV but was significantly higher overall (P < 0·05) for the silage juices (7·49) than for the lactic acid solutions (6·64) although this difference was mostly due to the extra dry matter (DM) contained in the added silage juice. Short-term DM intake (g per 3 h per kg live weight1·473) decreased with increasing NV, being significantly lower (P < 0·05) for the highest NV than for the others (3·58, 3·34 and 3·11) but lactic acid and silage juice gave similar responses (P > 0·05). Effects on short-term intake were influenced mainly by NV and suggested effects on immediate feedback mechanisms or palatability.

Twelve adult male alpacas were given either 0·67 (low) or 2·0 (high) × assumed maintenance requirements for a period of 6 weeks after which time each was transferred to the alternative level of nutrition for a further 6 weeks. Fibre samples were taken from two 10-cm2 areas on the mid-side position of each animal at 2, 6, 8 and 12 weeks, and measurements of fibre weight, yield (clean fibre weight/raw fibre weight), fibre diameter and fibre length made on the samples collected at weeks 6 and 12. The higher level of feeding resulted in higher clean fibre weight (low = 0·42 (s.e. 0·03); high = 0·53 (s.e. 0·04)mg/cm2 per day, P < 0·001) and fibre growth rate (low = 186 (s.e. 10); high = 223 (s.e. 14) yon/day, P < 0·05). Changes in yield (low = 0·917 (s.e. 0·006); high = 0·929 (s.e. 0·009)) and mean fibre diameter (low = 31·4 (s.e. 1·9); high = 32·1 (s.e. 1.6) \xm) were not statistically significant. Calculations showed that the increased weight of fibre attributed to the higher level of nutrition could be explained in terms of the observed increases in fibre-length and diameter but that, unlike the sheep in which the ratio fibre length: diameter remains relatively constant under varying nutritional regimes, the effect of nutrition in the alpaca has a proportionally larger effect on fibre length than on fibre diameter.

A study was conducted to evaluate increasing dietary levels of threonine on performance and carcass quality of growing gilt pigs (live-weight period of 50 to 95 kg; no. = 384) by using two different types of basal diets. One basal diet (basal A) was composed of highly digestible food ingredients and the other diet (basal B) of less well digested food ingredients. Before starting the growth trial, Heal apparent digestibility ofamino acids of both basal diets was determined in an in vivo digestibility trial with pigs. Both basal diets were composed in such a way as to obtain equal contents for net energy and Heal digestible threonine, lysine, methionine + cystine and tryptophan. The content of Heal digestible threonine in both basal diets was approximately 3·3 g/kg, corresponding with a total threonine content of 4·8 g/kg in basal diet A and 5·4 g/kg in basal diet B. To both diets three graded dose levels (0·4, 0·8 and 1·2 g/kg) of L-threonine were added, providing at the highest supplemented level 4·5 g/kg Heal digestible threonine. The requirement for Heal digestible threonine was estimated to be 4·1 g/kg regardless of diet composition. This estimated requirement was mainly based on the results for food conversion efficiency. For obtaining maximum weight gain, the requirement for Heal digestible threonine was found to be somewhat higher than for maximum efficiency of food utilization. The estimated requirement figure of 4·1 g Heal digestible threonine corresponded with approximately 5·6 g total threonine per kg in basal diet A and 6·2 g/kg in basal diet B. Carcass quality was not affected by the content of threonine in the diets.

Two experiments were conducted to compare the performance and behaviour of lactating sows and piglets in farrowing pens with crates or multisuckling systems (group housing of sows and piglets in the second half of lactation). All sows were farrowed in commercial accommodation based on farrowing pens with crates. In experiment 1, fifteen purebred Landrace or Large White sows and litters were recorded in crates as a control (C). Three replicates of six sows and litters were recorded in a multisuckling system (M) in which the sows and litters were group-housed from 2 weeks after farrowing until weaning. Experiment 2 involved 30 Manor Meishan sows (0·25 Meishan genes). The sows and litters were arranged into three treatments and two replicates with five sows and litters in each group. Treatments comprised a control farrowing pen with crate system and two multisuckling systems differing in degree of accessibility of the piglet creep area. Multisuckling 1 (Ml) had a solid creep front with an open doorway (0·5 X 0·9 m) for piglet access. In multisuckling 2 (Ml), the lower 30 cm of the solid creep front was removed to facilitate piglet access and allow visual contact with the sows. Piglets were weaned at 31 days in experiment 1 and 29 days in experiment 2. After weaning, piglets were moved to controiled-environment, fully slatted accommodation and monitored for 7 days in experiment 1 and for 12 days in experiment 2. Mortality rate in the two systems was not significantly different. However, some piglets in the M system were crushed after grouping (0·3 and 0·2 piglets per litter in experiments 1 and 2, respectively). Growth rate was reduced in M piglets in the week after grouping (256, 184 (s.e.d. 21·4) g/day, P < 0·01 for C and M respectively in experiment 1 and 243, 150 and 209 (s.e.d. 12·2) g/day, P < 0·01 for C, Ml and Ml respectively in experiment 2) but was higher after weaning (271, 313 (s.e.d. 35·7) g/day, P > 0·05 for C and M respectively in experiment 1 and 148, 280 and 222 (s.e.d. 15·0) g/day, P < 0·01 for C, Ml and Ml respectively in experiment 2). In consequence, piglet live weight at 1 week after weaning did not differ between treatments (9·33, 9·74 (s.e.d. 0·36) kg for C and M respectively in experiment 1 and 9·30, 914 and 9·53 (s.e.d. Oil) kg for C, Ml and Ml respectively in experiment 2). Sucking behaviour of M piglets in both experiments was severely disrupted (P < 0·01) on the day of grouping and the day after grouping. Despite synchronized suckling, M litters had a high incidence of cross suckling (> 50%) throughout lactation. M piglets spent more time than C outside the creep area, even with a more open creep (Ml). The Meishan sows tended to be more docile and fought less at grouping than the white breeds (0·39 and 1-71 fights per sow per h). Immediately after weaning, C piglets spent more time fighting (8·0 and 1·0 (s.e.d. 0·99) % of time, P < 0·01 for C and M respectively in experiment 1 and 4·51, 0·09 and 0·09 (s.e.d. 019) % of time, P < 0·01 for C, Ml and M2 respectively in experiment 2). These studies demonstrate that, in a multisuckling system, piglets achieved similar overall growth rate to C piglets, since both received checks in growth at different times and for different reasons.

All pig nutrition models to date predict growth responses of either an individual animal or the average animal of a given population over time. Translating the predicted nutrient requirements from the average animal to the population introduces a number of errors as the cause-and-effect response of the average animal is different from the population response. To overcome the problem of estimating the requirements for a given population using models it is necessary to simulate a number of individuals representative of a population and then average these results. This approach however, requires a knowledge of those animal characteristics that vary between individuals and the nature of their distribution. In this paper a scaled growth rate constant (B*), protein weight at maturity (Pm) and the ratio of lipid to protein at maturity (LPRm) are the parameters used to define an individual animal. As no data existed from which the nature of the distribution of B*, Pm and LPRm can be estimated for pigs of different strains and sexes, and due to the impracticality of determining this variability by experimentation, a simulation model was used to estimate the variations within each parameter. In addition this paper quantifies the subsequent effects these distributions have on the genetic variability of average daily gains (ADG) and daily food intake (TI) over a live-weight range of 25 to 90 kg. Comparisons were made between the genetic variation determined by modelling and those published in the literature. The results indicated coefficients of variation for B*, Pm and LPRm of 0·01, 0·05 and 0·10, respectively. An increase in the variability of all three parameters resulted in an increase in the variation in ADG whilst only an increase in the variation of B* and LPRm affected the distribution of FI.

Three ewes, three female goats and three male fallow deer, aged between 7 and 12 months and weighing 24·0 to 32·2 kg, were used in this experiment to outline the main differences in digestion among the three species. Dietary treatments were three diets with three forage: concentrate ratios of 10: 90, 50: 50, and 90:10 and two different feeding levels (45 and 90 g/kg M0·75 per day). The three diets were given to the three animals of each species in a Latin-square design; the two levels of feeding were compared ivithin diet in each period of the Latin square. The diet selected, apparent digestibility, and rumen retention time of Cr-mordanted neutral-detergent fibre were significantly different among species and dietary treatments. Interactions between species and dietary treatments were also significant for all the above variables. Sheep showed the highest intakes and apparent digestibilities of the forage-rich diets, and the longest rumen mean retention times. Goats tended to select diet components, despite allowance of diets being limited, and had lower food intakes than sheep. Apparent digestibility of forage-rich diet was also lower. Rumen mean retention times were shorter and less influenced by dietary treatments. Fallow deer had an apparent digestibility of forage-rich diets which was even lower than that of goats. Food intake was similar to that of sheep, with no evidence of selection. Rumen mean retention time was shorter than that of goats.

Low winter growth is a characteristic of male red deer and is caused, in part by a combination of reduced appetite and higher energy expenditure due to cold weather. This study aimed to determine whether housing during winter would reduce energy expenditure and increase the growth rate of male red deer calves. An additional aim was to investigate whether food restriction in winter would be compensated for by increased spring growth. In each of two consecutive years, 80 calves were randomly allocated to eight groups (no. = 10) comprising two replicates of four treatments during winter. Groups were housed inside (I) or outside (O) and given food either ad libitum (AL) or restricted (R) to maintain live weight. Winter treatments (southern hemisphere) ran from 22 May to 25 August (year 1) and from 5 June to 5 September (year 2). During these periods, animals were weighed weekly and group food intake recorded daily. At the end of winter animals were moved outside onto pasture and weighed monthly until the end of spring (27 November, year 1 and 7 December, year 2). In year 2 weighing continued during summer, until 4 April. The animals were slaughtered on 28 November and 18 January (year 1) and 5 April (year 2). The effect of housing on live-weight gain (LWG) and dry-matter intake (DM1) in AL groups was not significant in either year. However in R groups, O had a higher DMI than I in both years (P < 0·05) and a higher LWG than I in year 1 (P < 0·05). LWG was loiver in R than in AL groups in winter in year 1 (P < 0·05) and year 2 (P < 0·001) and live weight was lower in R than in AL groups at the end of winter in both years. Live weight was still lower in R than in AL groups at the end of spring in both years (P < 0·01). In year 2, this live-weight difference was not significant by the end of summer. Hot carcass weight (HCW) was greater in AL animals than R animals (P < 0·05) and dressing proportion was higher in R than in AL (P < 0·05) in year 1. GR (an index of body fatness) was greater (P < 0·05) in O than I in year 1 and was greater (P < 0·05) in AL than in R animals in year 2. Differences in GR between treatments were not significant in either year, with HCW as a covariate.

In conclusion, housing calves given food ad libitum during winter did not reduce DMI or increase growth rate. When normal growth rates were prevented by restricting food intake, housing lowered DMI requirement, although such a situation is unlikely to be a useful farm management practice as recovery from the growth check was slow. Annual variations in climate may determine both the food savings made by housing and the extent of compensatory growth of food-restricted animals in spring.

The aim of this work was to evaluate the effect of a short-term addition of an antibiotic food additive (50 mg zinc bacitracin per kg food) on skatole concentration in faeces, blood (vena jugularis) and backfat of boars kept under two housing conditions at summer temperatures. They were kept clean or were heavily fouled with faeces plus urine. The experimental material consisted of six litters in each of four replicates, in total 24 litters, each litter of four boars. Fourteen days before slaughter the boars were distributed to the four treatments in four equally large pens according to litter and start weight. Two pens had a wholly slatted floor and two pens had a concrete floor, and each pen held six boars allowing 0·6 m2 per boar. All boars were kept at high pig house temperatures (22°C). In the two wholly slatted-floor pens the boars were kept very clean and in the two concrete floor pens boars were kept heavily fouled with faeces and urine during the final 14 days before slaughter. Boars in half the pens of both floor types were given an antibiotic food additive (50 mg zinc bacitracin per kg food) in the last week before slaughter.

Administration of the food additive zinc bacitracin significantly decreased the skatole level in blood and backfat in both clean and dirty boars when used for 3 and 7 days before slaughter. The experiment further confirmed that boars at high stocking rate and lying in copious amounts of warm faeces and urine at temperatures of 25°C or more, for at least a week, had higher indole and skatole levels in blood and subcutaneous fat than pigs which were kept clean. The androstenone concentration in backfat was not significantly influenced by either of the two treatments. A highly significant correlation between skatole in blood (vena jugularis) and in backfat was found at the day of slaughter (r = 0·98).

Heart size of purebred boars (13 Landrace, 12 Yorkshire, and 14 Duroc) and crossbred (Landrace × Yorkshire × Duroc) boars (no. =18) and gilts (no. = 24) was studied. Purebred boars were raised from 30 kg for 110 days and slaughtered. Crossbred pigs of various body weights (30 to 110 kg) were selected and their plasma and blood volume were measured before sacrifice. The variation of heart size of pigs was studied and its correlation with growth performance or to vascular space was investigated. According to the principal component analysis heart size was best expressed by its weight, followed by the thickness of the anterior ventricle septum or the thickness of the left ventricle (LV) wall. The food/gain ratio of boars during testing period was significantly correlated with some size characteristics of their heart including weight, width, and LV thickness. The back fat thickness at 100 kg was significantly negatively correlated with heart weight, heart/body weight ratio, and LV thickness. Thus, selection for growth performance would result in a bigger heart in domestic pigs. In the crossbred study, an allometry fitting of H = 12·18B0·73 (r = 0·96) was obtained between heart weight (H, g) and body weight (B, kg). The fittings of heart weight to blood/plasma volume generated values of r of between 0·79 and 0·75 in allometry models or between 0·84 and 0·80 in linear models. Thus, vascular space is no better than fractional body weight as the basis to express relative heart weight in pigs. It is suggested that the normal exponent relating heart size to body weight in growing pig is effectively 0·75, similar to the exponent of metabolic size, 0·734 or 0·75. Therefore, the size of the heart of domestic pigs varies in size proportionally with the changes of metabolism seen in terms of growth or maybe even reproduction. The wild boar, the ancestor of domestic pigs, has a heart proportionately about 0·5 bigger than modern pigs when scaled according to M0·75. The attribution of metabolic difference to the bigger heart of wild boar is uncertain and needs further elucidation. The trend to bigger hearts in domestic pigs under current selection pressure for leanness should not necessarily be interpreted as returning to a natural form but may reflect a pathophysiological change.

The effects of olive (MONO) or sunflower (POLY) oil-enriched (30 g/kg) diets with either a basal (10 mg/kg food) or supplemented (200 mg/kg) level of a-tocopheryl acetate on some measures of production, fatty acid composition of animal tissues and susceptibility to oxidation of rabbit meat and membrane extracts have been studied. MONO diet produced higher levels of C18:1 in animal tissues. Animals that received POLY diet had a higher level of C18:2 in perirenal and neutral fraction of intramuscular fat and higher levels of C18:2, C20:4, C22:4 and C22:5 in phospholipid, reaching a higher overall unsaturation (P = 0·001). Muscle samples from rabbits given the POLY diet were more susceptible to lipid oxidation (P = 0·0001). Differences in membrane lipid oxidation, between groups followed a similar pattern to that of meat. Diets rich in C18:2 resulted in increases in concentration of pentanal (P < 0·001), hexanal (P = 0·0001) and total volatile aldehydes (P = 0·0001) in meat as monitored by headspace gas liquid chromatography. Dietary supplementation with α-tocopheryl acetate reduced the overall concentration of volatile aldehydes (P < 0·05), particularly hexanal (P < 0·05). Dietary administration of monounsaturated fatty acids not only reduces membrane and meat lipid oxidation but also modifies the relative proportion of volatile aldehydes generated upon heating, with a specific decrease in those generally related to rancidity and off-flavour of meats.

Ninety-six entire male Large White XLandrace pigs were assigned at 13 kg to one of six dietary crude protein (P) treatments (230 g/kg (P1), 201 g/kg (P2), 178 g/kg (P3), 151 g/kg (P4), 125 g/kg (P5), 93 g/kg (P6)) and one of four temperatures (T) (no. = 4) (18°C, 22°C, 26°C, 30°C), and were given food ad libitum until slaughter weight of 30 kg. At all temperatures gut fill was a constant proportion of food intake (Fl) (1·56) but this ratio varied with different protein concentrations. Food intake increased with decreasing temperature and with decreasing protein content to a maximum rate on P4 (1·347 kg) whereafter FI declined. There was a linear decrease in average daily gain (ADG) with decreasing protein content while temperature had a significant curvilinear effect on ADG and food conversion ratio (FCR) with maximum ADG (0·680 kg/day) at 26°C. Body protein content decreased as the dietary protein concentration declined below P3 and there was a corresponding increase in lipid content. Temperature had no effect on body protein content but had a significant effect on lipid content. Similar trends occurred in the rate of protein (PR) and lipid (LR) retention with maximum PR (117·1 g/day) attained on PI, P2 and P3. Protein and temperature had a significant effect on total heat loss (THL). Maximum THL occurred in the protein treatment that resulted in pigs consuming maximum FI. The efficiency of protein utilization increased with increasing temperature but the response was dependent on the protein supply. It is concluded that on low protein diets pigs increase their Fl to maintain potential protein growth until a point is reached where the animal can no longer compensate and FI will decline. The extent of the compensation will depend on the amount of heat the animal can lose which in turn is dependent on the environmental temperature.

An experiment was carried out to study the effect of changes in either the quality or the quantity of dietary protein intake on the free essential amino acid profiles in plasma, muscle or liver of growing chickens. Following a randomized paired-feeding design based on metabolic body weight (kg M0·75), White Rock male broilers were allocated to one of three isoenergetic (14·5 kJ metabolizable energy per g dry matter (DM)) semisynthetic diets containing different levels of protein (60, 120, 180 or 240 g/kg DM). All diets were based on soya-bean meal, as the sole source of protein, either unsupplemented (diets S) or supplemented with 20 g/kg L-lysine (diets SL) or 2 g/kg DL-methionine (diets SM). Samples of blood, biceps muscle and liver were taken and amino acid analysis was determined by high performance liquid chromatography. Plasma was only adequate to detect the effect of the supplementation with methionine to balance the dietary amino acid (AA) profile. Plasma concentrations of free methionine significantly increased as a result of the supplementation with methionine (P < 0·001) and remained unaffected by the amount of protein ingested. When lysine was added to diets S to induce an AA imbalance, a significant increase in muscle concentrations of free valine, isoleucine and phenylalanine (P <0·05) and a significant decrease in liver concentrations of free arginine and phenylalanine were observed (P<0·05). The supplementation with DL-methionine gave rise to a significant fall in the concentrations of free histidine, glycine and threonine (P < 0·05) and increased those of isoleucine and methionine in the skeletal muscle (P < 0·05), while in liver it significantly lowered the concentrations of free arginine, valine, leucine, phenylalanine and methionine (P < 0·001 to P < 0·05) and raised that of free glycine (P < 0·001). The ratios lysine: phenylalanine, lysine: valine and methionine: glycine in muscle together with that of methionine: glycine in liver seem to be appropriate indexes of the adequacy of the dietary AA profile to requirements.