The fatness of 34 non-pregnant Scottish Blackface ewes was estimated subjectively by lumbar palpation. The sheep were separated into groups of ‘fat’ (more than 27 % body fat) and ‘thin’ animals (less than 20% body fat). The voluntary intake of dried grass by these sheep was measured over a 6-week period.

The mean daily dry-matter intake by the thin sheep was 1·9 kg or 106 g/kg W0·73 and by the fat sheep was 1·4 kg or 68 g/kg W0·73.

Crimp, a distinguishing feature of sheep fibres, significantly affects wool value, processing and final fabric attributes. Several explanations for fibre bending have been proposed. Most concentrate on relative differences in the physicochemical properties of the cortical cells, which comprise the bulk of the fibre. However, the associations between cortical properties and fibre crimp are not consistent and may not reflect the underlying causation of fibre curvature (FC). We have formulated a mechanistic model in which fibre shape is dictated primarily by the degree of asymmetry in cell supply from the follicle bulb, and the point at which keratinisation is completed within the follicle. If this hypothesis is correct, one would anticipate that most variations in fibre crimp would be accounted for by quantitative differences in both the degree of mitotic asymmetry in follicle bulbs and the distance from the bulb to the point at which keratinisation is completed. To test this hypothesis, we took skin biopsies from Merino sheep from sites producing wool differing widely in fibre crimp frequency and FC. Mitotic asymmetry in follicle bulbs was measured using a DNA-labelling technique and the site of final keratinisation was defined by picric acid staining of the fibre. The proportion of para- to ortho-cortical cell area was determined in the cross-sections of fibres within biopsy samples. Mitotic asymmetry in the follicle bulb accounted for 0.64 (P < 0.0001) of the total variance in objectively measured FC, while the point of final keratinisation of the fibre accounted for an additional 0.05 (P < 0.05) of the variance. There was no association between ortho- to para-cortical cell ratio and FC. FC was positively associated with a subjective follicle curvature score (P < 0.01). We conclude that fibre crimp is caused predominantly by asymmetric cell division in follicles that are highly curved. Differential pressures exerted by the subsequent asymmetric cell supply and cell hardening in the lower follicle cause fibre bending. The extent of bending is then modulated by the point at which keratinisation is completed; later hardening means the fibre remains pliable for longer, thereby reducing the pressure differential and reducing fibre bending. This means that even highly asymmetric follicles may produce a straight fibre if keratinisation is sufficiently delayed, as is the case in deficiencies of zinc and copper, or when keratinisation is perturbed by transgenesis. The model presented here can account for the many variations in fibre shape found in mammals.

Fertility performance is intrinsically linked to the quality of the animal environment, overall management and nutrition. This review describes the use of dairy herd records, metabolic profiles and ultrasonographic findings at veterinary fertility examinations to monitor and manage dairy herd fertility. After calving, a cow has to overcome a series of physiological hurdles before establishing a pregnancy. The selection of timely key performance indicators (KPIs) that monitor specific events in the postpartum and service periods is vital to correctly identify problems and their potential causes that hopefully can be rectified. Cumulative sum charts are the timeliest monitors of efficiency of detection of oestrus, insemination outcome and relationship between postpartum events and fertility, with the point of inflection indicating when a change took place. Other KPIs use data from specific cohorts, adding an inherent delay to when change is indicated. Metabolic profiles and milk constituent data allow monitoring of nutritional adequacy and developments to offer new possibilities of on-farm systems for regular measurements of milk constituents (including progesterone) and energy status. Examination of the reproductive tract can be used to indicate individual and herd fertility status but the currently available detail is under used. Recent advances in ultrasonography can improve the diagnosis of reproductive tract pathophysiology still further but the clinical use of these methods in veterinary practice needs further evaluation. Development of new KPIs to exploit research findings are needed to ensure this knowledge is used to improve on-farm performance.

The rôle of protein in food intake regulation is complex in ruminants. Previous research has shown that a deficiency in degradable nitrogen (N) could affect microbial activity and decrease intake. On the other hand, an increase in metabolizable protein content of the diet seems to stimulate food intake in lactating dairy cows. The aim of this experiment was to determine whether metabolizable protein supply plays a direct rôle in the stimulation of food intake. Treatments comprised two infusions of soya protein isolate (800 g/day) either into the rumen (RP) or into the duodenum (DP), which were compared with two iso-energy infusions of glucose (880 g/day) either into the rumen (RG) or into the duodenum (DG). Four ruminally and duodenally cannulated cows producing 36·5 kg/day of milk were assigned to a 4 ✕ 4 Latin-square design with periods of 4 weeks. Duodenal infusions of protein (DP) significantly increased (P < 0·05) dry-matter intake (DMI) ( +1·9 kg/day), rate of intake ( + 8·2 g DMI per min), milk yield ( + 4 kg/day), protein content ( + 2·3 g/kg) and protein yield ( +191 g/day) compared with the glucose infusion in the duodenum (DG). No significant effect was observed with ruminal infusion of protein (RP) compared with the glucose infusion in the rumen (RG). The protein infusions had no effect (P > 0·05) on the apparent digestibility of dry matter, organic matter, neutral-detergent fibre or acid-detergent fibre and also no or only small effects on ruminal fermentation variables. Plasma concentrations of most of the essential amino acids increased significantly with the duodenal infusion of protein, whereas ruminal infusion of protein had no significant effect. It is concluded that direct supply of metabolizable protein stimulates intake independently of ruminal digestion effects.

In pikeperch, Sander lucioperca, aquaculture hormonal treatment is usually applied to synchronize ovulation. However, the effect of dopamine (DA) receptor antagonists, in particular those blocking the D1 DA receptors, remains unknown. Thus, the aim of the present study was to investigate and compare the effects of D1 and D2 DA receptor antagonists on the sex-steroid production and reproductive performance of the species. Two experiments were performed during which mature pikeperch females were injected with different molecules: NaCl 0.9% (negative control) or human chorionic gonadotropin 500 IU/kg (positive control) in both experiments, metoclopramide (a D2 receptor antagonist; 4 mg/kg or 20 mg/kg) or SCH23390 (a D1 receptor antagonist; 0.8 mg/kg or 4 mg/kg) alone (experiment 1) or in combination with a salmon gonadotropin-releasing hormone analogue (sGnRHa at 25 µg/kg; experiment 2). In experiment 2, fish were also injected with sGnRHa (25 µg/kg) as positive control. Samplings of oocytes and blood were performed on the day of injection and after 24 h (both experiments), after 48 h (experiment 2) and at the time of ovulation (both experiments). In non-ovulating fish, samplings were performed 7 days (experiment 1) or 14 days (experiment 2) after injection. In experiment 2, various zootechnical parameters of fertilized eggs were recorded (survival, hatching and malformation rates). The two antagonists alone were ineffective in inducing the final stages and regulating sex-steroid (testosterone, 11 ketotestosterone, 17β estradiol and 17,20β-dihydroxy-4-pregnen-3-one) production. When administered with sGnRHa, both SCH23390 and metoclopramide induced the final stages. However, only SCH23390 stimulated testosterone (4 mg/kg) and 17β estradiol (0.8 mg/kg) production compared with sGnRHa alone. None of the treatments affected the survival, hatching or malformation rates. This is the first report suggesting that in pikeperch the D1, but not the D2, DA receptor antagonist would be involved in the testosterone and 17β estradiol production as a potentiator of the sGnRHa effect.

A deterministic bio-economic model simulating beef production during the life cycle of a cow and her offspring was used to estimate biological and economic values of daily gain, marbling score, birth weight, weaning weight and mature weight for three production systems (cow-calf, feedlot and integrated) and alternative production circumstances in Japan. Biological efficiency (live-weight basis and lean-weight basis) and economic efficiency (returns over costs) were regarded as breeding objectives. Alternatives included reducing the maximum number of reproductive cycles, marketing by constant slaughter weight (BASE), constant age or constant carcass fat content, lighter slaughter weight and doubling food prices. Biological efficiency on a live-weight basis for the cow-calf system was most influenced by increasing weaning weight; for the feedlot and integrated system, increasing daily gain had the largest influence. For biological efficiency of lean production, increasing daily gain and mature weight had the largest influence in the feedlot and integrated systems, respectively. For economic efficiency, increasing weaning weight was most beneficial in the cow-calf system and increasing marbling score was most beneficial in the feedlot and integrated systems. Economic values of daily gain and weaning weight decreased markedly with increasing genetic levels of these traits. Marketing by age decreased the biological values of daily gain but increased the economic value of daily gain. Marketing at a constant carcass fat content decreased biological values of mature weight but increased the economic value of mature weight. Decreasing slaughter weight provided negative economic values of daily gain and weaning weight. Economic values were reduced when food prices were doubled.

The feeding of housed lambs on conserved forages and pelleted rations is accompanied by a high risk of chronic copper (Cu) poisoning (CCP) which might be reduced by selecting sires for low liver Cu status. Livers were therefore retrieved from Suffolk, Texel and Charollais lambs, slaughtered during the course of a performance trial, to ascertain sire and possibly breed effects on the rate of Cu accretion in the liver. In total, 160 livers were obtained, 100 from Suffolk, 40 from Texel and 20 from Charollais lambs, the progeny of 14, eight and eight sires, respectively. Lambs came from three separately managed flocks but were brought together at 8 weeks of age, weaned onto a common complete diet containing 6·1 mg Cu per kg dry matter (DM) and offered ad libitum. One-fifth of each breed group was slaughtered at 14, 18 or 22 weeks and the remaining 40% at 26 weeks of age. Mean (s.e. ) liver Cu concentrations at those ages were 3220 (450), 4639 (464), 6426 (468), and 6513 (370) µmol/kg DM for Suffolk, and 5843 (811), 6579 (857), 8017 (811) and 10406 (589) µmol/kg DM for Texel, respectively. The pattern of liver Cu accretion differed, the Suffolk starting at a low value yet reaching a plateau at about 22 weeks of age (significant quadratic regression coefficient), the Texel, continually increasing from a high initial value at an average rate of 53·7 (s.e.10·6) µmol/kg DM per day. There was a significant effect of sire on liver Cu in the Suffolk (P 0·05) with a heritability of 0·85 (s.e. 0·44); in the Suffolk and Texel combined, the heritability was 0·60 (s.e. 0·33). The data available on the Charollais were too limited to test for sire effects but at 26 weeks of age, where most information was available, the mean liver Cu concentration was 7285 (s.e.826) µmol/kg DM. At a given age, food intake, liver weight and live weight were each lowest in the Texel but when expressed as a proportion of live weight (LW), both food intake (43 g/kg LW) and liver weight (5·15 g DM per kg LW) were similar among breeds (P 0·05). Thus, differences in liver Cu accretion are unlikely to reflect differences in Cu intake per unit liver weight. There was a tendency for liver size per kg LW to decrease as liver Cu rose in the Texel but not in the Suffolk. Continued hepatic Cu accretion in the Texel may reflect a breed-specific inability to cope with Cu overload. Increases in liver Cu to marginally toxic levels in some Suffolk, some Charollais and most Texel lambs, and to a level commonly associated with toxicity in one Texel lamb, on a ration of moderate Cu concentration highlights the difficulty of controlling risk of CCP by manipulating dietary composition. The current EC limit for Cu in ovine diets, 17 mg Cu per kg DM, is clearly too high for the breeds and dietary conditions used in this study. However a safe limit would be hard to achieve and hence the need to exploit sire variation in propensity to accumulate liver Cu to reduce disease risk.

A study urns conducted to determine the best method of preparation of silage and freshly cut forage samples for the estimation of rumen degradability by the nylon bag technique. Three types of forage were evaluated: a grass silage, a fresh grass (ryegrass) and a fresh legume (white clover). For each forage, six preparation methods were compared: chopping fresh (FRS); chopping and macerating fresh (FMC); chopping, freezing, thawing and macerating (FRZ); freeze-drying (FD); low-temperature oven-drying (45°C, 72 h) (OVD); high-temperature oven-drying (160°C, 90 min) (DHD). Dried samples were hammer-milled (2·5-mm screen). Chemical composition and rumen degradability were affected by the method of preparation. Protein fractions were sensitive to drying method, and oven-drying reduced nitrogen (N) solubility and degradability as the severity of the heating was increased. OVD and DHD gave lower estimates of N and dry matter (DM) solubility and degradability than FD. The effect of drying method on DM degradability was to reduce solubility and effective degradability, calculated for an outflow rate of 0·033 per h, but not potential degradability.

Silage DM degradability was less affected than that of fresh forages. Freshly prepared samples (FRS, FMC, FRZ) gave lower estimates of N and DM solubility and degradability than FD, the differences being least with silage and FRZ, which was the most effective at rupturing plant structures of the FRS, FMC and FRZ methods. Of the six preparation methods, freeze-drying was the most effective preparation method. FRZ and OVD were less effective, but similar to each other. The small particles (calculated) produced by grinding dried samples may result in an overestimation of zero time losses and hence the degradability of the sample. These undesirable effects might be minimized by coarser grinding (4-mm screen) and correction for particulate matter loss.

Quality of pork depends on genotype, rearing and pre- and post-slaughter conditions. However, no information is available on rearing system changes and oleic acid supplementation on carcass characteristics and fatty acid (FA) profile of pork from the Alentejano (AL) pig, an obese breed. This study evaluates the effects of feeding low (LO) or high oleic acid diets (HO) to AL pigs reared in individual pens (IND) or outdoor (OUT) with access to pasture. Carcass composition was obtained and longissimus dorsi and semimembranosus samples were collected to analyse chemical composition and neutral and polar intramuscular lipids FA profile by gas chromatography. Statistical analysis was performed by a two-way ANOVA for rearing system and diet effects. OUT-reared pigs presented leaner carcasses than IND-reared ones. Both muscles presented lower intramuscular lipid content in OUT-reared pigs. Treatments affected the FA profile of muscles. Overall, OUT-reared pigs presented lower n-6/n-3 FA ratios, whereas pigs fed the HO diet exhibited lower saturated fatty acids (SFA), higher monounsaturated fatty acids (MUFA) levels and lower thrombogenic indexes on neutral intramuscular lipids than LO-fed pigs. On the polar fraction, OUT-reared pigs presented lower SAT and n-6/n-3 FA ratio, and higher polyunsaturated fatty acids (PUFA) levels on both muscles. Pigs fed the HO diet exhibited higher MUFA and lower PUFA levels on both muscles, and lower SAT levels on semimembranosus. This study shows rearing system and oleic acid supplementation have complementary effects and influence carcass composition and the nutritional quality of meat.

To evaluate the ability of the eel to use diets with high carbohydrate content, a comparative study was made by using the rainbow trout, a carnivorous fish, as a reference species. Four isoenergenetic diets (in terms of gross energy) were formulated incorporating different protein/carbohydrate ratios (450/200, 370/300, 290/400 and 210/500 as g/kg dry matter, respectively) and each one was tested in three replicates groups of eels and trout. The data on growth, food conversion and utilization of dietary protein and energy show that the eel has a comparatively greater ability than the rainbow trout for using diets with a high carbohydrate level. Thus it is postulated that higher carbohydrate levels could be used for formulating cheaper diets.

Ova ageing is the most important factor affecting fish egg quality after ovulation. Long-term storage of fish ova, using cryopreservation and vitrification techniques, has been unsuccessful to date. Instead, short-term in vitro ova storage has been used successfully and optimized in some cultured fish species. In vitro ova storage can drastically improve mass production of larvae and juveniles in the hatcheries by providing the possibility of the synchronous artificial fertilization for different females. To study how long unfertilized eggs of Eurasian perch (Perca fluviatilis L.) can retain their fertilizing ability after stripping, eggs were stored at temperatures of 4°C, 8°C and 12°C for 72 h post-stripping (HPS). The stored eggs of four female perch were separately fertilized at 0 h (i.e. control eggs fertilized before storage) and at 6-hour intervals during the experimental period of 72 h. The embryos reaching the eyed-egg and hatched-larvae stages, eyed-egg mortality and larval malformation rates were recorded as indices of egg quality. The results indicated that the maximum eyed eggs and hatched larvae (86% and 63%, respectively) were observed for eggs fertilized immediately after stripping, whereas the storage of the eggs at 4°C for 48 HPS decreased the eyed-egg and hatched-larvae rates to 46% and 17%, respectively. The use of a higher storage temperature resulted in a more rapid decrease in egg viability: eyed-egg and hatched-larvae rates of 23% and 9%, respectively, were obtained after 48 HPS storage at 8°C and 2% and 1% for eggs stored at 12°C. Eyed-egg mortality and larval malformation rates were not significantly affected by post-stripping ova ageing for at least up to 36 h. Thereafter, both values increased significantly and were measured to be the highest in the most aged ova. The present study demonstrated that stripped Eurasian perch eggs can be stored for at least 12 h at 4°C to 12°C without a significant reduction in their quality.

Ninety entire male pigs were used in two experiments to investigate the effects of energy concentration on the performance of growing pigs given diets containing relatively high or low levels of fibre. A blended fat product was also compared with tallow as a source of dietary energy for pigs in the first experiment.

In experiment 1, 60 pigs growing between 20 and 45 kg live weight were given 10 diets containing approximately 120 g acid-detergent fibre per kg (80 g crude fibre per kg), and 10, 30, 50, 75 or 100 g/kg of either tallow or the blended fat product.

Although the source of fat had no significant effect on food intake or growth performance, voluntary energy intake and growth rate increased with increase in the level of fat added to the diet and with concomitant increase in dietary digestible energy (DE) concentration up to 50 g/kg and 13·2 MJ/kg respectively. Further increase in the level of fat added to the diet and in DE concentration resulted in a decline in voluntary food intake, whilst energy intake and growth rate remained relatively constant at 27 MJ/day and 720 g/day respectively.

In experiment 2, 30 pigs were used to investigate the animals' response to five levels of dietary DE concentration (11·8 to 15·1 MJ DE per kg) between 20 and 50 kg live weight. The highest level of acid-detergent fibre in the diets was 62 g/kg (50 g crude fibre per kg) and this declined with increase in energy concentration to 30 g/kg (25 g crude fibre per kg) in the diet of highest energy concentration.

Voluntary food intake was not significantly affected by dietary energy concentration, and voluntary energy intake and growth rate increased linearly with increase in dietary energy concentration up to 14·5 MJ DE per kg. Maximum energy intake (31 MJ DE per day) and growth rate (905 g/day) in experiment 2 was proportionately 0·15 and 0·26 higher than that achieved by pigs given the higher fibre diets in experiment 1.

The results for voluntary food intake and growth rate suggested that the pig's demand for energy and consequently its response to dietary energy concentration was affected by dietary fibre concentration.

1. Twenty-two Scottish Blackface, 51 Welsh Mountain and 22 Tasmanian Merino lambs aged between 6 and 75 h were tested for resistance to body cooling in a climate chamber. Blackface lambs had long birthcoats, Merinos were short-coated. Welsh lambs were from two strains with long (L) and short (S) types of birthcoat. Some lambs were clipped before cold exposure.

2. Clipping reduced cold resistance in Welsh (S) and (L) lambs by factors of 3 and 13 respectively.

3. Undipped lambs showed significant breed differences, Welsh (L) and Blackfaces having the greatest cold resistance and Merinos the least. Long-coated lambs (Blackface and Welsh (L)) were on average six times more cold resistant than the average of Welsh (S) and Merino lambs; and Welsh (L) lambs were four times more resistant than the Welsh (S) type. Birth weight and age did not significantly influence cold resistance.

4. In clipped lambs there was a significant positive linear regression between cold resistance and birth weight. Breed differences in cold resistance were still significant if no adjustment was made for the effect of breed differences in birth weight.

5. Cold resistance was strongly influenced by breed differences in birthcoat morphology and probably by other physiological factors partly attributable to the different genetic backgrounds associated with birthcoat type. The breed differences in cold resistance were generally consistent with field data on mortality and body temperature regulation of lambs in severe weather, suggesting that climate chamber tests might be used to evaluate potential viability in the field.

Salinization of groundwater and soil is a prevalent global issue with serious consequences on animal health and production. The present study was conducted to investigate the capacity of Boer goats to adjust their salt intake from saline drinking water in a free-choice system. In total, 12 non-pregnant Boer goats aged between 1 and 8 years with an average BW of 46.4±8.3 kg were kept in individual pens for 4 weeks. In the control phase (1 week), only fresh water was supplied in five identical buckets for each pen. During the subsequent treatment phase (3 weeks), fresh water and four different concentrations (0.75, 1.0, 1.25 and 1.5% NaCl) of saline water were offered simultaneously in a free-choice system. The positions of the concentrations were changed daily at random. Cut hay and water were provided ad libitum, and a mineral supplement was allocated. Feed and water intake, mineral supplement intake, ambient temperature and relative humidity were recorded daily, whereas BW and body condition score were measured weekly. Dry matter intake, total water intake and total sodium intake were significantly (P<0.001) higher during the treatment phase. Body weight and body condition were not affected by saline water intake. Across the treatment phase, saline water consumption was significantly (P<0.001) lower in young (19.6±27.1 g/kg BW0.82 per day) than in adult goats (27.9±31.5 g/kg BW0.82 per day), indicating that young goats were more sensitive towards the saline water. All goats had a significant preference for fresh water (0% salt) over saline water. At the first offering of the simultaneous choice situation (week 2), animals did not differentiate between the salt concentration of 0.75% and 1.0%. However, with successive treatment (weeks 3 and 4), animals distinguished between saline water concentrations and preferred the 0.75% salt concentration. Salt concentrations of 1% to 1.5% were avoided. The total sodium intake of the goats ranged between 0.37 and 0.55 g /kg BW0.75 per day during the treatment phase, being 8- to 11-fold higher than the daily requirements of sodium for body maintenance. The results suggest that goats are able to differentiate between saline water concentrations and to adjust their sodium intake by quick adjustments in self-selection in a free-choice system. Compared with two-choice preference tests, the present free-choice situation allows evaluating changes in saline water acceptance with prolonged exposure.

Electrical conductivity was measured during the oestrous cycle of cows with electrodes implanted in the vaginal wall. Conductivity was considerably higher during oestrus than during the preceding or following cycle stage. Conductivity was also high in the fresh surgical wound, whereas the healing process was accompanied by a decrease.

Genetic and phenotypic relationships between performance test and reproduction traits were estimated, after five generations of divergent selection for components of efficient lean growth, in a population of Large Wltite pigs. On ad-libitum feeding, a total of 4334 pigs were performance tested, of which 884 selected gilts had measurements of reproduction traits. On a restricted feeding regime, 1558 pigs were tested, which included 336 selected gilts with reproduction records. For pigs given food ad libitum, genetic correlations between litter weights at birth and weaning with daily food intake (0·48 and 0·42, s.e. 0·16) and with growth rate on test (0·65 and 0·52) were positive, but correlations with backfat depths were not significantly different from zero. For pigs given food at a restricted level, litter birth weight was positively genetically correlated with growth rate (0·50, s.e. 0·18) and negatively correlated with backfat depths (-0·48, s.e. 0·16). Phenotypic and environmental correlations between performance test and reproduction traits were all less than 0·10 in magnitude, for pigs tested on either feeding regime. The variation in backfat depth enabled detection of a non-linear relationship between predicted breeding values for litter weight at birth with predicted breeding values for average backfat depth of farrowing gilts performance tested on ad-libitum feeding, but not for gilts tested on restricted feeding. The positive genetic correlations between growth rate and daily food intake with litter traits suggested that selection strategies which change growth and daily food intake may result in relatively greater genetic changes in piglet growth rate than in litter size.

1. Experiments were done to assess the reaction of sheep to small artificial shelters and to study the effect of these shelters on the live-weight gain of young lambs in the springs of 1958, 1959 and 1960.

2. Lambs sought shelter particularly when it was raining. They were sensitive to high wind speed and low temperature but did not usually shelter in mild dry weather.

3. Ewes were indifferent to rain and remained in the open in wet weather while many of their lambs sheltered. They occasionally used the shelters for shade in warm sunny weather when their lambs usually went with them.

4. Because of these differences between ewes and lambs in their response to shelter, during wet weather ewes were less closely associated with their lambs where they had access to shelter than where there was no shelter.

5. In the wet spring of 1958, lambs with access to shelter gained weight more slowly than those without shelter. It is postulated that the lambs with shelter may have consumed less milk than the others due to a weaker social bond with their dams.

6. None of the experiments showed that shelter improved the live-weight performance of young lambs.

1. The influence of seasonal, maternal and genetic variation on body weight and fleece characters of Welsh Mountain sheep is reported.

2. Fertility and rearing ability of ewes improved from first to third lamb crop.

3. Male lambs were on average 0·4 lb. heavier at birth than females. Birth weight increased with number of pregnancies of the dam.

4. Early growth of the lamb between birth and marking (24 days old) used partly as a measure of milk production of the ewe, was greater in males than in females. Lambs born to older ewes made the greatest gains over this period, although the trend was not significant.

5. Weaning weight of the lamb was affected by the dam's weight at tupping, the number of preceeding pregnancies, her milk yield and also by the season in which the lamb was born. Despite these effects weaning weight proved a good guide to the weight (at subsequent matings) at 1½ and 2½ years old.

Heritability by intra-sire parent-offspring regression was 0·51±0·07 (P<0·001) and repeatability was 0·43 (P<0·001).

6. Fleece weight was not affected by season or age of ewe. However, the heaviest lambs at weaning tended to have heaviest fleeces the following year.

Heritability by intra-sire daughter-dam comparison was 0·58±0·11 (P<0·001) and repeatability was 0·46 (P<0·001).

7. Staple length measured on the mid-side of the animal had a repeatability between years of 0·56 (P<0·001) while heritability by daughter-dam regression was 0·38±0·ll (P<0·001).

8. Fourteen Welsh Mountain rams were progeny tested. Nine of the rams were purchased at local sales and 5 were home bred. They were not selected for the traits examined.

No statistically significant differences were obtained between sire progeny groups for weaning weight and fleece weight.

Log-linear relationships between various measurements of the chemical and physical body composition of the pig were obtained in four datasets representing a range of sexes, genotypes and feeding treatments. One of these datasets (dataset 1) comprised genetic control and selection line Large White pigs. There were significant differences between datasets for most of the relationships investigated. The causes of the differences cannot be determined. Within datasets, relationships between various body components and the weight of crude protein in the whole body were unaffected by genotype or sex. The relationships of both intermuscular fat and trimmed carcass lipid with whole body lipid differed significantly between the control and selection lines in dataset 1. Fat thickness measurements taken over the m. longissimus at the last rib were less at the same body lipid in the selection line than the control line suggesting a redistribution of fat away from this area as a result of selection. Relationships between viscera, lungs and empty body weight were significantly affected by line while those between trimmed carcass, liver, kidneys and empty body weight were significantly affected by sex. Selection line pigs had less perinephric and retroperitoneal fat than controls at the same whole body fat weight and less subcutaneous fat at the same cold carcass weight. There were no significant line effects on lean or bone weight distribution. Selection line pigs had significantly less subcutaneous fat in the collar joint and more intermuscular fat in the ham. There were few significant sex effects on tissue weight distribution.

On many Australian commercial pig farms, groups of growing pigs are mass-medicated through their drinking water with selected antimicrobials for short periods to manage herd health. However, delivery of medication in drinking water cannot be assumed to deliver an equal dose to all animals in a group. There is substantial between-animal variability in systemic exposure to an antimicrobial (i.e. the antimicrobial concentration in plasma), resulting in under-dosing or over-dosing of many pigs. Three sources of this between-animal variability during a water medication dosing event are differences in: (1) concentration of the active constituent of the antimicrobial product in water available to pigs at drinking appliances in each pen over time, (2) medicated water consumption patterns of pigs in each pen over time, and (3) pharmacokinetics (i.e. oral bioavailability, volume of distribution and clearance between pigs and within pigs over time). It is essential that factors operating on each farm that influence the range of systemic exposures of pigs to an antimicrobial are factored into antimicrobial administration regimens to reduce under-dosing and over-dosing.