A deletion approach was undertaken to identify which amino acids (AA) most limited the growth of mixed ruminal microorganisms on xylan. Ruminal fluid was withdrawn from sheep receiving a mixed grass hay/concentrate diet and incubated for 24 h with oat spelts xylan in the presence or absence of a mixture of 20 AA or the same mixture with a single AA deleted. Gas and volatile fatty acid production were increased by the AA mixture in comparison with incubations in which ammonia was the only added nitrogen (N) source, and the deletion of each of the aromatic AA, tyrosine, phenylalanine and tryptophan, as well as leucine and methionine, led to decreases (P < 0·05) in fermentation rate. The addition of aromatic AA as a mixture to ammonia-only fermentations increased (P < 0·05) the fermentation rate but failed to replicate the benefits of the complete mixture of AA. Although the addition of all 20 AA increased (P < 0·05) the microbial yield by up to 0·56, no single AA deletion had a significant (P > 0·05) influence on microbial yield, and the aromatic AA mixture also did not increase the microbial yield on xylan over the yield with ammonia as sole N source. It was concluded that aromatic AA may be first-limiting for xylan fermentation, but they cannot replace the benefits of a complete mixture of 20 AA in stimulating xylan fermentation by ruminal micro-organisms.

Minerals are limiting factors in animal production, and the knowledge of mineral requirements for livestock is crucial to the success of a commercial enterprise. Hair sheep may have different mineral requirements than those presents by the international committees. A study was carried to evaluate the net calcium (Ca), phosphorus (P), magnesium (Mg), sodium (Na), potassium (K), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) requirements for the growth and maintenance of Brazilian Somali lambs. A total of 48 hair lambs (13.5±1.8 kg) aged 60±15 days were allocated to individual pens. Eight animals were slaughtered at the beginning of the experiment to serve as a reference group to estimate initial empty BW (EBW) and initial body composition. The remaining lambs (n=40) were assigned to a completely randomized design with eight replications in five levels of metabolizable energy (ME; 4.93, 8.65, 9.41, 10.12 and 11.24 MJ/kg DM). When the lambs of a given treatment reached an average BW of 28 kg, they were slaughtered. Initial body composition was used to calculate the retention of minerals. Mineral body composition was fit using a logarithmic equation in the form of a nonlinear model. The maintenance requirements were estimated from regressions of mineral retention in the empty body on mineral intake. The body mineral concentration decreased in lambs with a BW ranging from 15 to 30 kg. The net mineral requirements (100 g/day of average daily gain (ADG)) decreased from 0.52 to 0.51 g for Ca, 0.28 to 0.23 g for P, 0.02 to 0.02 g for Mg, 0.09 to 0.08 g for Na, 0.11 to 0.09 g for K, 1.30 to 1.08 mg for Zn, 3.77 to 3.22 mg for Fe, 0.08 to 0.06 mg for Mn and 0.09 to 0.08 mg for Cu when BW increased from 15 to 30 kg. The daily net requirements for maintenance per kilogram of BW were 30.13 mg of Ca, 27.58 mg of P, 1.26 mg of Mg, 4.12 mg of Na, 8.11 mg of K, 0.133 mg of Zn, 0.271 mg of Fe, 0.002 mg of Mn and 0.014 mg of Cu. The results of this study indicate that the net mineral requirements for weight gain and maintenance in Brazilian Somali lambs are different than the values that are commonly recommended by the main evaluation systems for feed and nutritional requirements for sheep. These results for the nutritional requirements of minerals may help to optimize mineral supply for hair sheep.

A sib selection programme for length of carcass was carried out for five generations within a closed herd of Large White pigs. A generation interval of one year was obtained.

Litter production was good throughout the project and the numbers of pigs born and reared in the final generation were 11·2 and 10·3 respectively.

Overall response to selection was predicted with reasonable success. The increase in length was associated with an increase in number of vertebrae.

Heritability for length of carcass computed from the pooled components of variance was 0·53 ± 0·12. Realized heritability was 0·5 ± 0·1. No control strain was maintained.

Correlated traits moved in the expected directions and responses were beneficial for traits such as backfat measurements and chest depth, but unfavourable for belly thickness and ham conformation. Carcass acceptability was not good initially and this deteriorated during the project. The difficulties involved in maintaining selection pressure and herd size are discussed. Abnormalities and lameness were recorded and did not increase systematically over the experiment.

It is suggested that the specific relationships between ‘conformation’, carcass value and viability require further investigation with particular reference to length of leg and length of carcass.

As a result of the selection for genotypes with greater sow prolificacy, litter size increased and, concomitantly, average litter birth weight and early postnatal survival rates of low birth weight (L-BtW) offspring decreased. This study compared the impact of l-carnitine (CAR) and l-arginine (ARG) supplemented with a milk replacer and fed to L-BtW piglets born from large litters from days 7 to 28 of age on growth performance, carcass composition, organ and Semitendinosus muscle (STM) development. A total of 30 female and castrated Swiss Large White piglets weaned at 7 days of age were assigned to three milk replacer diets containing either no supplement (CON), CAR (0.40 g/piglet per day) or ARG (1.08 g/kg BW per day). Piglets were kept in pairs in rescue decks (0.54 m2). They were weighed daily and daily allowance of both, feed and ARG, was adjusted accordingly. Thus, feed allowance depended on growth. Each day, the milk replacer was prepared with water (1:4). Feed (allowance: 60 g dry matter/kg BW per day) was offered daily in six equal rations. Feed intake and feed efficiency was assessed for the pairs and apparent total tract-energy and -protein digestibility was determined from days 21 to 28 of age. On day 28, piglets were euthanized, blood samples were collected and the whole STM and organs were weighed. In STM, the size and metabolic properties of myofibers were determined. No difference in growth performance was found between dietary treatments, but piglets from the CAR group tended (P<0.10) to grow faster during the 1st experimental week and consume more feed from days 14 to 21 as compared with piglets of the CON group. A setback in growth in the last week in the CAR group coincided with the lower (P<0.05) energy and protein digestibility. Dietary treatments had no effect on STM and organ weight and myofiber size. Compared with the other groups, there were trends (P<0.10) for blood serum urea and glucose level to be greater in CAR and for non-esterified fatty acid level to be greater in ARG piglets. The greater (P<0.05) ratio of lactate dehydrogenase to either citrate synthase or β-hydroxyacyl-CoA dehydrogenase indicated that the relative importance of the glycolytic compared with the oxidative pathway was greater in STM of CAR and ARG compared with CON piglets. These results suggest that ARG and CAR supplements were beneficial for muscle maturation whereas findings on phenotypic traits were rather unsystematic.

In a lifetime study of spring-born cattle in a 20-month beef system the effects of production factors on carcass characteristics were examined using 302 serially slaughtered animals born in three consecutive years. A multifactorial design was used with three animal factors — maturity (early maturing Hereford crosses v. late maturing Charolais crosses), sex (heifer v. steer) and method of rearing (suckled calves v. bucket-reared calves). After an initial rearing period, feeding treatments were imposed during the subsequent winter period, followed by the imposition of two sward heights (low 6 to 8 cm and high 8 to 10 cm) during the subsequent grazing season. An initial representative group of 16 cattle was slaughtered at the start of the grazing season and most of the remaining cattle were subsequently slaughtered off grass at three randomly allocated slaughter times, on average 67, 110 and 154 days post turn-out. Interactions between the main production factors were not significant with the exception of slaughter date with winter feeding levels for fat in rib joint and weight of saleable meat, and slaughter date and sex for live weight, carcass weight and weight of saleable meat. Breed type, sex and method of rearing affected the weight of saleable meat off grass by 14·7, 14·8 and 5·6 kg respectively. The influence of the winter feeding treatments on the weight of saleable meat was small by the time the final group were slaughtered. Sward height had a transient effect on weight, condition and carcass composition, the effects becoming less evident as the grazing season progressed. The effect of delaying slaughter had the largest and most significant influence on carcass composition of all the production factors studied, although changes in body composition between slaughter dates were relatively slow.

Estimates of (co)variance components and genetic parameters were obtained for birth (no. = 3909), weaning (no. = 3425), yearling (no. = 2763), and final weight (no. = 2142) for Gobra cattle at the Centre de Recherches Zootechniques de Dahra (Senegal), using single trait animal models. Data were analysed by restricted maximum likelihood. Four different animal models were fitted for each trait. Model 1 considered the animal as the only random effect. Model 2 included in addition to the additive direct effect of the animal, the environmental effect due to the dam. Model 3 added the maternal additive genetic effects and allowed a covariance between the direct and maternal genetic effects. Model 4 fitted both maternal genetic and permanent environmental effects. Inclusion of both types of maternal effects (genetic and environmental) provided a better fit for birth and weaning weights than models with one maternal effect only. For yearling and final weights, the improvement was not significant. Important maternal effects werefound for all traits. Estimates of direct heritabilities were substantially higher when maternal effects were ignored. Estimates of direct and maternal heritabilities with model 4 were 0·07 (s.e. 0·03) and 0·04 (s.e. 0·02), 0·20 (s.e. 0·05) and 0·21 (s.e. 0.05), 0·24 (s.e. 0·07) and 0·21 (s.e. 0·06), and 0·14 (s.e. 0·06) and 0.16 (s.e. 0·06) for birth, weaning, yearling and final weights, respectively. Correlations between direct and maternal genetic effects were negative for all traits, and large for weaning and yearling weights with estimates of -0·61 (s.e. 0·33) and -0·50 (s.e. 0·31), respectively. There was a significant positive linear phenotypic trend for weaning and yearling weights. Linear trends for additive direct and maternal breeding values were not significant for any trait except maternal breeding value for yearling weight.

With deep frozen bull semen processed in an egg yolk – milk diluent and stored in plastic straws at — 196°C, a lowering of the dose rate from 25 million (3824 inseminations) to 12·5 million total sperm per insemination (3900 inseminations) resulted in a decline in conception rate (CR = 49-day non-return rate) of 6·5 % (60·1 v. 53·6). Development of a processing technique which allowed sperm to be stored at — 196°C at concentrations of 450 or 100 million sperm per ml prior to subsequent rapid thawing and redilution (RDF) allowed dose rates to be reduced to around 5 million total sperm per insemination without any significant reduction in CR. The re-diluted semen was used for inseminations made from 4 to 8 h after thawing and redilution. The use of RDF procedure could reduce semen storage costs, increase the number of inseminations per sire, and has potential application in oestrus synchronization programmes or in countries with developing insemination programmes.

A series of change-over experiments examined the intake and digestibility of straw-based diets in yearling dairy heifers. Voluntary intakes of straws given as the sole food to yearling dairy heifers were 1·28, 1·20 and 0·90 kg dry matter (DM) per 100 kg live weight for barley, wheat and oat straws respectively, and the corresponding digestibility of organic matter was 0·47, 0·53 and 0·48. When supplemented with 2 kg rolled barley the intakes of straw did not alter, nor were they affected by replacing part of the rolled barley with an equal amount of soya-bean meal and thus increasing the dietary concentration of protein from about 50 to 110 g/kg DM. The use of molassed sugar-beet pulp in place of rolled barley reduced the intake of straw. Flaked maize promoted slightly higher intakes of straw than an equal amount of coarsely milled maize. Replacing rolled barley by lucerne hay reduced straw intake. It is estimated that, to provide sufficient energy and protein for a daily gain of 0·5 kg, heifer straw-based diets would require a supplement of 1·2 kg rolled barley and 0·8 kg soya-bean meal.

Differences in insulin binding affinity and in concentrations of insulin receptor, were found in a variety of tissues taken, at slaughter, from mature steers (701 (s.d. 23) kg) and growing lambs (47 (s.d. 2·1) kg). In both species, liver had lower insulin binding affinity than skeletal muscles m. pectineus m. longissimus dorsi and m. rectus capitis (all P < 0·001) and subcutaneous, omental and perirenal adipose depots (all P < 0·001). Site-specific differences in affinity for insulin existed between adipose depots (subcutaneous < omental, P < 0·05; subcutaneous < perirenal, P < 0·001) and between tissue-types (subcutaneous fat < m. pectineus skeletal muscle, P < 0·05; m. rectus capitis < perirenal fat, P < 0·05) in steers. In lambs also, receptor affinity for insulin differed between tissue-type (m. longissimus dorsi < perirenal fat, P < 0·05; m. rectus capitis < subcutaneous fat, P < 0·05 and m. rectus capitis < perirenal fat, P < 0·001) but lambs did not show the adipose depot-specific differences in insulin affinity observed in steers. Insulin receptor concentration differed between adipose depots (subcutaneous < omental, P < 0·05; subcutaneous < perirenal, P < 0·01) and between tissue-type (m. pectineus < perirenal fat P < 0·05) in steers and perirenal and subcutaneous adipose depots of lambs had higher receptor concentrations than m. longissimus dorsi and m. pectineusP < 0·001). This is the first study to demonstrate, in any species, differences in insulin receptor binding affinity and receptor concentration in a wide range of tissues (liver, skeletal muscles and adipose depots) from the same individual. Such differences in meat-producing animals could, through effects on tissue sensitivity and/or responsiveness to insulin, influence nutrient partitioning to tissues and affect overall rates of lipid storage and net protein synthesis.

Factors affecting calving interval (CI) in double-muscled Belgian Blue (DMBB) beef cows were investigated with regard to the BW yield (BWY) of the cow–calf pair, using 834 CI records from 386 females with parities 1 to 6. The effect of parity and CI on BWY was also studied. Cow–calf pair BWY was defined as calf birth weight plus dam BWY per CI. CI (mean±s.e.: 404±1.9 days) was affected by parity, calving season, suckling and calf birth weight/dam weight. Primiparous cows had a shorter CI than cows with three or more calvings (P<0.05), with an intermediate CI for second-calf cows. Spring calvings resulted in a shorter CI than summer and autumn calvings, with intermediate values for winter calvings. Suckling dams had longer CIs than non-suckling dams. There were interactions (P<0.05) between calving season and suckling, and between calving season and mating system. Shortest CIs were observed for spring calvings in case of non-suckling and for summer calvings in case of suckling. Longest CIs were observed for autumn calvings in case of natural service (NS) and for winter calvings in case of artificial insemination (AI). Calf birth weight/dam weight of 6% to 10% resulted in shorter CI than a ratio of <6% (P<0.05). Body condition and mating system (NS v. AI) did not affect CI. Daily cow–calf pair BWY was affected by parity (P<0.001) and CI (P=0.013), with a tendency for an interaction (P=0.094). Daily cow–calf pair BWY did not differ for CIs of <12 to 16 months in primiparous cows and was lowest for a CI of 13 to 15 months in second-calf cows, whereas the effect of CI was more variable in older cows. Dam contribution to cow–calf pair BWY was larger than calf birth weight in first- and second-calf cows, and increased with increasing CI. Dam contribution to cow–calf pair BWY was smaller than calf birth weight in older cows, varying from 0.2 to 1.0 depending on CI. A short CI is advised for DMBB cows because of a larger BWY and more efficient nutrient utilisation.

Digestible (DE) and metabolizable (ME) energy values for five copra meals and a sample of raw copra, with oil contents ranging from 4 to 662 g/kg, were determined with both a high and a low energy basal diet in a metabolism experiment using 16 female pigs. Determined DE values ranged from 12·68 to 29·92 MJ/kg dry matter (DM) and values for ME from 11·95 to 29·08 MJ/kg DM which was a reflexion of their residual oil contents. Regression equations for the six samples were derived with DE and ME as dependent variables and chemical measurements and gross energy as independent variables. The best equation based on a single chemical parameter (ether extract (EE)) was:

Improvements associated with including more than one independent variable in the regression analysis were marginal. The most accurate equation (in terms of minimized residual s.d.) based on EE and crude fibre (CF) was:

Comparative studies were performed on the in-situ rumen degradation rate (kd) and the in-situ rumen undegradable residue (U) of dry matter (DM) and crude protein (CP) in sheep and dairy cows. The effect of different treatmentsfor sheep were investigated together with the validity of using cow-based reference protein values of foods for sheep. The effect of different breeds (Texel ewes and crossbred ewes), dietary roughage: concentrate ratio and shearing (mild cold exposure) were investigated for sheep.

The in-situ rumen incubations were performed in accordance with standard operational procedures which were comparable for both species. The foods under consideration were hay and concentrates. Cows displayed lower (DM 0·53 , CP 0·86) Kds than sheep for concentrates.

For hay a clear trend between cows and sheep was not observed but cows displayed 0·40 lower Kds than Texel ewes and 0·30 higher Kds than crossbred ewes. For concentrates U levels did not differ between species but for hay cows had 0·45 higher U values than Texel ewes. Texel ewes showed 0·45 higher Kd and 0·35 lower U for DM and CP than crossbred ewes. Dietary roughage: concentrate ratio in sheep diets did not influence the Kds and Us of the foods under consideration. Shearing of crossbred ewes increased Kd of CP by 0·25 and reduced U for DM and CP by 0·20 and 0.24 .

In conclusion different in situ rumen degradation rates were found between dairy cows and sheep. This probably makes using reference protein values of foods invalid for sheep since they are based on data for cows. Differences (Kd andU) were also found between sheep breeds and between unshorn and shorn crossbred ewes (mild cold exposure). No effect on rumen degradation kinetics could be attributed to dietary roughage: concentrate ratio.

A 3 ✕ 2 factorial experiment with a total of 60 male castrated pigs, live-weight range 24 to 104 kg, was carried out to test three dietary levels of high fat rapeseed press cake in two crossbreeds differing in carcass lean. The six groups with 10 pigs each representing either crossbreeds of Landrace (LR) ✕ (LR ✕ Large White (LW)) (groups 1, 3 and 5) or Pietrain (Pi) ✕ (LR ✕ LW) (groups 2, 4 and 6) were each offered, ad libitum, diets without rapeseed press cake (groups 1 and 2), or with rapeseed press cake: 75 g/kg diet (groups 3 and 4) or 150 g/kg diet (groups 5 and 6). The press cake produced in a small oil press contained 341 g crude protein per kg dry matter (DM), 181 g ether extract per kg DM and 23·3 mmol glucosinolates per kg DM. Rapeseed press cake, particularly at 150 g (3·2 mmol glucosinolates) per kg diet, lowered food intake and weight gain, though only significantly in the Pi-sired hybrids. There were no effects of the diets on leanness, whereas the 550 g/kg of carcass lean of Pi-sired pigs was significantly higher than the 510 g/kg of LR-sired hybrids. Meat of the Pi-sired crossbreeds showed a lower pH (tendency), higher conductivity, lower impedance and higher drip loss. At 150 g/kg diet rapeseed press cake LR-sired crossbreeds showed the darkest meat and the Pi ✕ LR, LW hybrids the lowest sensory evaluation score. In LR-sired hybrids the rapeseed press cake diets increased the backfat polyunsaturated fatty acids (PUFA) to a lower degree (1·3% per 10 g rape oil increase in 1 kg diet) than in Pi-sired hybrids (2·6% per 10 g rapeseed increase in 1 kg diet). Using simple correlation coefficients, the sensory evaluation results were negatively correlated with carcass lean and tended to be so with meat fat PUFA content. Pigs should receive less than 2 mmol glucosinolates per kg diet corresponding to 50 to 100 g double zero rapeseed products per kg diet. Rape oil should be recommended according to the animals lean and fat status, respectively. Fatter pigs may receive a maximum of 40 g, leaner pigs a maximum of 20 g rape oil per kg diet.

Thirty-six British Friesian castrated male cattle (steers) were included in an experiment to measure the response in live-weight gain and body composition to feeding barley-based diets containing increasing levels of formaldehyde-treated soya bean meal. The response was measured between 100 kg and 350 kg or 450 kg live weight. The basal diet of pelleted whole barley and 10% ground oat straw contained 16·6g to 38·5 g nitrogen per kg dry matter. There were no overall differences in live-weight gain or in feed intake. Between 100 kg and 250 kg live weight, live-weight gain increased significantly from 1 08 to 1·24 kg/day when the lowest and highest nitrogen diets respectively were fed (P<0·05). Animals given the highest nitrogen diets also consumed significantly more feed (P<0·05). Conversely, in the subsequent growth period between 250kg and 350kg live weight, live-weight gain decreased from 109 to 0·89 kg/day when the highest nitrogen diet was fed. There were no significant differences in feed intake.

Groups of four animals per treatment were slaughtered at 365 kg and 465 kg fasted live weight. When animals were fed 23·7 g nitrogen per kg dry matter and slaughtered at 365 kg fasted live weight there was significantly more omental fat (P<0·05) and the fat depth at the 12th rib was greater than in animals fed the higher levels of nitrogen. The differences in omental fat weight between the 23·7 g nitrogen and 16·6g nitrogen per kg dry matter diets were not significant. The proportion of crude protein (nitrogen × 6·25) in the boneless 9-10-1 lth rib of animals fed 23·7 g nitrogen per kg dry matter was the lowest of all diets and significantly less than the two highest nitrogen diets (P<0·05). When similar animals were slaughtered at 465kg there was a non-significant trend for omental fat weight and fat depth at the 12th rib to decrease as the nitrogen content of the diet increased.

1. Pig growth hormone (PGH) concentrations were measured in plasma samples from piglets of 3–4 to 7–8 weeks of age.

2. Plasma PGH concentrations decreased significantly with age. No difference was observed between the hormone concentrations of gilts and barrows.

3. Correlation coefficients were calculated between mean plasma growth hormone concentration over a 4-week period and several carcass characteristics and measures of growth rate. Plasma PGH over this period showed significant negative correlations with several measures of carcass backfat thickness at bacon weight. In barrows only, PGH concentrations showed a significant direct correlation with relative growth rate from 3 to 7 weeks.

Piglet mortality in outdoor production systems varies across the year, and a reason for this variation could be fluctuations in hut climate, as ambient temperature might influence piglet survival, both directly and indirectly. Therefore, the aim of the current study was to investigate the impact of farrowing hut climate and year variation on stillbirth and liveborn mortality. A large-scale observational study was conducted at five commercial organic pig-producing herds in Denmark from June 2015 to August 2016. Both year variation (F3,635=4.40, P=0.004) and farrowing hut temperature (F2,511=6.46, P=0.002) affected the rate of stillbirths. The risk of stillborn piglets was lowest in winter and during this season larger changes in hut temperature between day 1 prepartum and the day of farrowing increased the risk of stillbirths (F1,99=6.39, P=0.013). In addition, during the warm part of the year stillbirth rate increased at temperatures ⩾27°C. Year variation also affected liveborn mortality (F3,561=3.86, P=0.009) with a lower rate of liveborn deaths in spring. However, the hut climate did not influence liveborn deaths. Consequently, other factors than hut climate may explain the influence of year variation on liveborn mortality. These could be light differences causing seasonality in reproduction and lactation.

When supplementing lamb diets with vitamin E, an equivalence factor of 1.36 is used to discriminate between RRR-α-tocopheryl acetate and all-rac-α-tocopheryl acetate. However, more recent studies suggest a need for new equivalence factors for livestock animals. The current study aimed to determine the effect of RRR- and all-rac-α-tocopheryl acetate supplementation on α-tocopherol deposition in lamb tissues. A total of 108 Rasa Aragonesa breed lambs were fed increasing amounts of all-rac-α-tocopheryl acetate (0.25, 0.5, 1.0 and 2.0 g/kg compound feed) or RRR-α-tocopheryl acetate (0.125, 0.25, 0.5 and 1.0 g/kg compound feed) by adding them to a basal diet that contained 0.025 g/kg feed of all-rac-α-tocopheryl acetate as part of the standard vitamin and mineral mixture. The diets were fed for the last 14 days before slaughtering at 25.8±1.67 kg BW. Within 20 min after slaughter samples of muscle, heart, liver, brain and spleen were frozen at −20°C until α-tocopherol analysis. Increased supplementation of either vitamin E sources led to a significant increase (P < 0.001) in α-tocopherol concentration in all tissues studied. The tissue with the highest α-tocopherol concentration was the liver followed by spleen, heart and muscle. At similar supplementation levels (0.25, 0.50 and 1.0 g/kg compound feed), α-tocopherol content in the selected tissues was not affected by α-tocopherol source. However, the ratios between RRR- and all-rac-α-tocopheryl acetate increased with the increasing α-tocopherol supplementation (at 0.25 and 1.0 g/kg compound feed), from 1.06 to 1.16 in muscle, 1.07 to 1.15 in heart, 0.91 to 0.94 in liver and 0.98 to 1.10 in spleen. The highest relative proportion of Ʃ2S (sum of SSS-, SSR-, SRS- and SRR-α-tocopherol)-configured stereoisomers was found in the liver of lambs supplemented with all-rac-α-tocopheryl acetate accounting for up to 35 to 39% of the total α-tocopherol retained, whereas the proportion of Ʃ2S-configured stereoisomers in the other tissues accounted for <14%. Increasing all-rac-α-tocopheryl acetate supplementation was also found to affect the 2R-configured stereoisomer profile in muscle, heart and spleen with increasing proportions of RRS-, RSR- and RSS- at the cost of RRR-α-tocopherol. In all tissues, the relative proportion of all non-RRR-stereoisomers in lambs receiving RRR-α-tocopheryl acetate was lower than RRR-α-tocopherol. These results confirm that the relative bioavailability of RRR- and all-rac-α-tocopheryl acetate is dose- and tissue-dependent and that a single ratio to discriminate the two sources cannot be used.

Samples of cooked muscle of Swamp buffalo, Hereford, Angus, Friesian and Charolais cross steers were sheared and scored by a taste panel for tenderness, flavour, juiciness and palatability. The cattle were given commercial pellets from 9 months of age to slaughter at 12,15 and 18 months. The buffaloes were fed one of four regimens: all pellets, all hay, 3/4 pellets and 1/4 hay or 1/4 pellets and 3/4 hay from 13 to 22 months of age to slaughter at 20 to 34 months.

There was little difference between the buffaloes and the cattle in shear-force or taste panel scores. Age at slaughter had no significant effect on the quality traits measured in either the buffaloes or the cattle. The feeding regime did not influence the tenderness, flavour or palatability of buffalo muscle but the high pellet diets increased juiciness.

Shear-force was not influenced by rectal or muscle temperatures, muscle pH, carcass weight or fatness in the buffaloes but fatness reduced shear-force in cattle m. longissimus.

Buffalo intramuscular fat increased with age and carcass fatness but had no effect on shear-force or taste panel score.

The type of mating system we should use in any plan of livestock improvement requires very careful consideration. By reason of the particulate nature of inheritance and the behaviour of chromosomes in the cell divisions preceding the formation of eggs and sperm, the various mating systems differ in their influence upon the uniformity or otherwise of successive generations, the chances of securing improvement, the scope for control by selection, and finally, our ability to discriminate between the relative contributions of genetic and environmental variations to the population variance. Because of the genetic complexity many misconceptions have flourished about what we may expect with different mating systems, about the effects of inbreeding and the advantages and dangers of outbreeding. Different breeders have often secured different results with similar mating systems and the search for a rule of thumb guide has proved fruitless.

The extent to which grazing intensities of animal production systems in the uplands of the United Kingdom cause impacts on vegetation, soils, birds, mammals and invertebrates, and influence landscape value and water quality are reviewed. It is argued that these impacts need to be considered in an integrated manner in relation to their responses at the field and landscape scales. Evidence is presented which suggests that a range of grazing intensities is required to obtain significant benefits to the natural heritage. This suggests that new approaches are required to the mechanisms of delivering environmental benefits from grazing systems.