A total of 96 Large White weaner pigs, comprising equal numbers of entire males and females, and of controls and eighth generation index-selected genotypes, were fed ad libitum until 40 kg live weight. From 40 kg until slaughter at 85 kg live weight pigs within genotype and sex groups were fed either ad libitum or 2·2 times maintenance. The left sides of the carcasses were divided into shoulder, middle and ham portions and the middles further divided into eye, wedge and belly dorso-ventral portions. Tissue dissection was performed on all portions separately.

Selected pigs yielded proportionately 0·15 less fat, 0·08 more muscle, a smaller muscle: bone ratio and 4·05 mm less P2 backfat depth than the controls. When the data were adjusted to the same mean P2 fat depth, the carcasses of selected pigs had 0·07 less fat and 0·03 more muscle. There were no appreciable differences between the genotypes in cranio-caudal tissue distribution. However, there were differences in dorso-ventral tissue distribution since the middles of selected pigs had proportionately and absolutely more of each tissue in the belly. There was no evidence that selection against fat at the P2 site had caused any increase in fat lateral to the m. longissimus.

Food restriction increased carcass muscle by 0·10 and decreased fat by 0·17, but had no effect on muscle: bone ratio or cranio-caudal or dorso-ventral tissue distribution. At the same carcass side weight and P2 fat depth, restricted feeding decreased fat by 0·10 and increased muscle by 0·06 in the carcass side.

It is concluded that carcasses of the selected pigs would be undervalued relative to the controls due to less fat and more muscle at the same weight and P2 fat depth. Also, restriction on food intake can cause carcasses to be undervalued relative to feeding ad libitum.

Masham ewes carrying single, twin or triplet foetuses were offered a ration of concentrates which increased from 200 to 650 g per ewe per day over the last 7 weeks of pregnancy in 2 years. Silage was offered ad libitum and the voluntary intake of each ewe was measured. In the first year, 30 ewes were offered a poorly-preserved, wet silage (A) which had a low digestibility, followed by a better-preserved silage (B) which had a higher digestibility and dry-matter concentration. There was an increase in silage intake when the change was made from A to B. In the following year, 32 ewes were offered silage (C) which was well preserved, similar in digestibility to B but with a lower dry-matter concentration. The ewes ate more silage organic matter (g/kg live weight) with C than A (12·77 v. 9·34) in weeks 15 to 17 of pregnancy but more of B than C (13·76 v. 10·38) in weeks 19 to 20. Ewes carrying single lambs ate more silage and had a slower rate of decrease in silage intake when the concentrate ration was increased as pregnancy progressed. As litter size increased there-was either greater loss or smaller gain in body condition score.

Outdoor farrowing huts facilitate a less restricted maternal behaviour in sows compared with sows kept indoors in farrowing pens. The aim of our study was to investigate whether there are behavioural differences between primiparous sows kept outdoors in farrowing huts and indoors in pens, and whether the maternal behaviour during the second parity, when all sows were kept outdoors in farrowing huts, would differ between sows that have experienced the indoor or the outdoor environment, respectively, during their first parturition. A total of 26 Yorkshire×Swedish Landrace sows were studied. Of these, 11 sows were housed outdoors in farrowing huts during both parturitions (group=OUTOUT). The other 15 sows were kept indoors in a barn with single farrowing pens during their first parturition. During their second parturition, sows were kept outdoors in farrowing huts (group=INOUT). The behaviour was video recorded from 2 h prepartum to 48 h postpartum. The sows’ responsiveness to playbacks of a piglet’s screams was tested on days 2 to 3 postpartum. Parity 1: during the last 2 h prepartum, OUTOUT sows had a higher proportion of observations in the sternal lying position (P<0.01). During parturition, OUTOUT sows changed posture more often (P<0.05) and were lying less (P<0.05) than INOUT sows. All sows in both groups responded with ‘lifting head’ towards the playback of piglet scream, whereas 100% of OUTOUT sows and only 43% of INOUT sows thereafter were ‘getting up’ (P <0.01). Parity 2: There were no behavioural differences between INOUT and OUTOUT sows. In conclusion, it is not problematic for a second parity sow with initial maternal experience from an indoor farrowing pen to be kept outdoors in farrowing huts during its following farrowing.

The link between circulating glucocorticoids and leptin in beef calves has not been explored but has been noted in several studies. The aim of this study is to determine the effects of exogenous glucocorticoids given at birth and 1 day of age on serum leptin concentrations in beef calves. Ruminant animals secrete leptin, which is thought to be important for the programming of the hypothalamic appetite centers. Angus crossbred cows (n = 31) bred via natural service were utilized for this experiment. At parturition (day 0), calf BW was recorded and each calf was infused intravenously with either a hydrocortisol sodium succinate solution (HC, 8 males and 8 females) at a dosage of 3.5 μg/kg of BW or a similar volume of saline solution (CONT, 7 males and 8 females). Each calf was given a second infusion of its respective treatment 24 h postpartum at 1.5 μg/kg of BW for HC treatment. Calf treatment was blocked by sex, dam body condition score (BCS), and dam age. Blood samples were taken via jugular venipuncture before infusion, daily from days 0 to 5, then every other day up to day 17. Serum leptin and cortisol concentrations were analyzed via radioimmunoassay. Dam age, dam BCS, calf BW, and serum leptin and cortisol concentrations were analyzed using MIXED procedure of SAS. Dam age was not different (P = 0.81) among HC and CONT calves (4.9±0.5 and 4.7±0.5, respectively). Dam BCS was not different between treatments (5.7±0.2 and 5.6±0.2 HC and CONT, respectively; P = 0.66). There was no difference in calf birth BW between treatments (P = 0.87) and averaged 38.3±1.4 kg. Cortisol concentrations were not different between both treatments (P = 0.23) from birth to day 4 of age. Calves that received the HC treatment showed significantly reduced (P = 0.03) leptin concentrations on days 1 to 13. Calf BW from 60 to 150 days of age was not different between CONT and HC treated calves (P = 0.65). These data indicate that exogenous glucocorticoids can be used to suppress neonatal leptin levels in calves. This could lead to changes in voluntary feed intake of treated calves.

Least cost rations for specific rates of growth in the growing and finishing periods were given to pigs slaughtered at 200 lb. live-weight. During the growing period pigs grew very close to the planned rates in spite of the fact that some food was rejected. Pigs given rations for a low growth rate in the growing period grew slightly faster than planned in the finishing period. In the finishing period pigs given rations for the high growth rate grew on average very near to this rate. The pigs given the ration for the low growth rate grew slightly faster than planned. Food conversion efficiency was for all pigs very near to, or slightly better than, that planned. The rations had no adverse effect on carcass quality.

Silage cut twice annually (June and August) from a tetraploid red clover/grass sward and three times annually (May, July and September) from a low nitrogen (N) and high N perennial ryegrass/white clover sward was fed in proportion to dry-matter yield from each cut, over a 10-week period, each winter for 3 years to castrated male cattle of initial live weight 401 kg in year 1 and 425 kg in years 2 and 3. The silages were supplemented with 0, 1, 2 and 3 kg concentrate per head daily.

Total dry-matter yield from the red clover/grass sward was similar to that from the perennial ryegrass/white clover sward (high N grass) receiving 360 kg N per ha but the digestibility, particularly of first cut material was much lower. Dry-matter production of the low N grass/white clover sward was 0·73 of high N grass sward and produced silages of similar digestibility and fermentation.

Dry-matter intakes by the cattle were higher on the legume-based silages in years when clover made a worthwhile contribution to total yield, but this did not significantly improve utilization or animal performance compared with high N grass silage. Mean daily carcass gain per head on red clover/grass silage was 0·41 kg which was significantly less than the 0·61 kg on white clover/grass silage and 0·59 on high N grass (P < 0·001). Carcass output from red clover/grass silage was 618 kg/ha and 629 kg/ha from white clover/grass, both of which were significantly less than the 863 kg/ha from the high N grass silage (P < 0·001). Dressing proportion was also significantly poorer in animals fed red clover/grass silage compared with the other silage types.

Five years' records of unculled White Wyandotte flocks at Hillsborough, Northern Ireland, were analysed to give estimates of heritabilities and of genetic and environmental correlations by two methods. Pooling data for four years and eliminating hatch effects gave heritabilities of 0·28 for eggs laid by survivors to 500 days; 0·61 for weight of pullets at penning; 0·51 for weight of pullets at 8 weeks; 0·18 for days to first egg; and 0·71 for spring egg weight. These are in general agreement with most other published figures, as are most of the genetic correlations. A suggestion of sex-linkage in the genetic correlations between weight at 8 weeks and days to maturity was not supported by other figures from the data. The method of eliminating hatch effects, unexpectedly, gave higher heritability figures where heritability was already moderate or high. It gave numerically greater figures in most genetic correlations, but did not lead to an expected reduction in the environmental correlations. The data were probably inadequate for a rigorous test of the method.

A comparison was made of various devices to obtain preantral follicles from bovine ovaries. The most productive collection methods in terms of number of follicles obtained were the tissue chopper and the grinder method, with an average number of 122·25 (s.e. 5·06) and 120·45 (s.e. 6·89) preantral follicles, respectively. These were followed by ficoll gradation (119·90, s.e. 7·95), mincer (101·75, s.e. 3·98), cell dissociation sieve (100·50, s.e. 3·42) and homogenizer (95·75, s.e. 6·38). For enzymatic digestion, more time was needed and the method was less productive. Microdissection could supply good quality (80% live when collected), larger sized follicles (120 to 220 µm) but with the lowest yield (10·65, s.e. 0·94) per ovary. The isolated follicles did not show any difference (P > 0·05) in viability until day 7 of in-vitro culture irrespective of method used to harvest follicles. Accordingly the new grinding device can be recommended as a replacement for the existing mechanical devices as it can yield the same percentage (47%) of live preantral follicles but of a wider diameter range (40 to 180 µm) per ovary.

1. Twenty-eight calves fed reconstituted buttermilk for 20 days and then concentrates, hay and water were allocated to 4 treatments consisting of the addition of chlortetracycline to both the buttermilk and the concentrate mixture, to the buttermilk alone, to the concentrates alone, or to neither.

2. Live-weight gains from 3 to 28 days and the incidence of scouring were not affected significantly by any of the treatments.

3. The addition of chlortetracycline to the concentrate mixture increased significantly: (a) rate of live-weight gain from 28 to 56 days and from 56 o t 84 days: (b) skeletal growth from 3 to 84 days: (c) the consumption of concentrates from 14 to 56 and from 14 to 84 days; and (d) the concentrate conversion rate.

4. The addition of chlortetracycline to the buttermilk had no significant effect on any of the above measurements neither did it make any significant difference to the effect of adding chlortetracycline to the concentrate mixture.

5. There was a direct relationship between quantity of concentrates consumed on the one hand, and rate of live-weight gain and efficiency of conversion of the concentrate, on the other. None of the treatment effects was significant after the data were corrected for differences in the quantities of concentrates consumed.

6. From the results of this experiment and from evidence in the literature it is postulated that one of the effects of feeding antibiotics to calves is to reduce the fermentative activity of rumen bacteria and consequently the amount of gas produced in the rumen, the net result being that the antibiotic-fed animal eats more food and hence grows more quickly.

Histological examination of the rumen wall in intensively managed beef cattle confirmed the superficial nature of many of the lesions present and failed to reveal evidence of secondary bacterial infection. Of the lesions described, only intra-mucosal abscesses and their subsequent erosions proved to be significantly related to the occurrence of hyperkeratosis of the rumen mucosa. The remaining lesions, vacuolation of the stratum granulosum, acute microscopic ulceration, congestion of the submucosa and the presence of leucocyte aggregations in the submucosa, were all independent of this hyperkeratosis.

This study was conducted to investigate the pattern of plasma carotenoid concentration (PCC) in lambs switching from a low to a high dietary carotenoid level. A total of 12 Romane lambs were individually penned indoors and fed a low dietary carotenoid level for 23 days (period 1) and then a high dietary carotenoid level for 15 days (period 2). At the beginning of period 2, the lambs were 15 weeks old and weighed 29.9 kg (s.d. 2.7) on average. Lambs were fed daily (dry matter) 0.558 kg alfalfa pellets, 0.181 kg straw and 0.181 kg barley. Plasma content of total carotenoids was measured daily in period 2 by spectrophotometry. PCC (μg/l) varied with the animal (P < 0.001) and with time elapsed since the beginning of alfalfa distribution (P < 0.001). Mean PCC was 8 μg/l (s.d. 3.3) at the beginning of period 2, then increased curvilinearly with the time elapsed since the beginning of alfalfa distribution. As early as 24 h on the alfalfa diet, PCC was already higher than before the switch (P < 0.001). Mean PCC continued to increase until day 6 on average and reached a plateau thereafter. We propose a monomolecular function to model this pattern, the equation obtained on the mean data being: PCC = 97 (s.e. 2.2) × (1−exp(−0.3378 (s.e. 0.0282)×d)), where r2 = 0.997, r.s.d. = 4.47, n = 15 and d = day. The percentage of variance explained by the model ranged between 95.9% and 99.2%, depending on the animal. The parameters of the monomolecular function varied among animals, confirming the interindividual variability in animal response. Plateau for PCC was reached slightly earlier for the six lambs with the lowest values of the asymptote than for the six lambs with the highest values of the asymptote.

Three methods were used to make differential counts of living and dead bull spermatozoa in samples of frozen semen in an egg-yolk citrate medium containing glycerol.

With two methods (‘phase’ and ‘nigrosin’ methods) dead spermatozoa were identified by their altered structure. With a third method (nigrosineosin) dead spermatozoa were identified by their staining affinity. With the phase method spermatozoa were immobilised by treatment with approximately M/40 sodium fluoride and were examined by phase-contrast microscopy in unfixed wet preparations. With the other two methods the spermatozoa were examined in smears stained either with nigrosin alone (nigrosin method) or with nigrosin and eosin (nigrosin-eosin method).

Analysis of variance of the results of a factorial experiment involving fluoride-treated and untreated samples from 6 bulls with the three methods showed that differences between semen samples contributed 66% of the variation. A defect of the phase method was that the variance between counts was greater than the theoretically expected value.

All spermatozoa in nigrosin-eosin stained preparations were stained with eosin within a few days of the smears being made, so that living and dead spermatozoa could not be distinguished by their differing affinities for eosin. Repeat counts on nigrosin-stained preparations did not differ significantly from counts made several days previously. Sodium fluoride in the concentration used here (M/40) tended to reduce the percentage of dead spermatozoa.

1. Pelleted grass and a concentrate containing 90% rolled barley and 10% soya bean meal were offered to cows in three combinations, 25: 75, 50: 50 and 75: 25 respectively, together with a constant low level of coarse roughage.

2. The experiment was carried out in two stages, in early lactation as a randomized block design involving 18 Jersey cows fed to appetite and in mid-lactation as a 3 × 3 Latin square change-over design involving 12 cows, rationed according to milk yield.

3. There were no significant between-treatment differences in either milk yield or milk fat content in either stage of the experiment.

Four central performance tests of growth in Hereford bulls from about 10 to 19 months of age on pasture were conducted in New Zealand. From the 100 bulls performance tested 63 were representatively sampled, including bulls with high and low performance test rankings, and progeny tested in dairy herds. Crossbred progeny were purchased from the dairy herds at 3 to 4 months of age, assembled in one location and reared together on pasture for 14 to 15 months prior to slaughter. Regressions of progeny growth and carcass traits on a number of different performance traits for growth of their sires were in almost all cases not statistically significant. The effective heritability, from offspring-sire regression, was 0·07 (s.e. 0·05) for final live weight and 009 (s.e. 0·06) for post weaning gain from about 200 to 550 days of age. It is concluded that central performance tests, as presently conducted in New Zealand, are of limited value for ranking breeding values of bulls for growth. Possible reasons for these results are discussed. It is suggested that pre-test environmental effects and age at the start of the central test are critical factors.

1. A growth and digestibility trial was carried out with 27 British Friesian calves given diets having either 3·1, 2·8 or 2·4 Meal metabolizable energy per kg dry matter and either the same concentration of protein or the same protein-to-energy ratio.

2. Daily dry-matter intake and rate of gain in live weight increased significantly as the energy concentration of the diet was reduced. There were no significant differences in digestible-energy intake between calves given the different diets, although the trend was the same as for dry-matter intake.

3. Both dry-matter digestibility and energy digestibility were lowest for the low-energy diet.

Micronization followed by grinding of brown-seeded sorghum increased starch availability in vitro but had no effect on proximate composition of the grain. In diets containing 70% of sorghum in ground or micronized and ground form, apparent digestibility of dry matter and nitrogen and nitrogen retention by growing pigs were improved (2·5, 5·0 and 12·2% respectively). Addition to the diet of 0*2 g polyethylene glycol per g crude protein in the sorghum fraction produced similar effects. In the ground cereal diet inclusion of polyethylene glycol increased apparent digestibility of gross energy (3·8%) and improved metabolizable energy content by 5·5%, but i n the micronized and ground cereal diet the additive had no effect.

Finn Dorset ewes were offered forage ad libitum from week 16 of pregnancy until lambing and were either unsupplemented (U) or given 600 g/day of concentrates (S). Grass silage and white clover silage, ensiled separately and having similar dry matter concentrations, were offered in four mixtures with white clover proportions of 0, 0·20, 0·40 and 0·60 on a fresh basis. Forage intake was significantly higher for mixtures containing higher proportions of clover (9·1, 10·5, 12·3 and 13·6 g organic matter (OM) per kg live weight) and the ewes gained more weight (33, 65, 178 and 174 g/day) and had smaller losses in body condition score (–0·59, –0·49, –0·39 and –0·17). Higher proportions of clover in the diet in late pregnancy also resulted in significantly higher growth rates of lambs during lactation, when a common diet was offered.

The number of foetuses carried in pregnancy had significant effects on intake and some aspects of performance. For ewes carrying singles, twins and multiples respectively, mean daily forage intakes were 12·2, 11·9 and 10·4 g OM per kg live weight and losses in body condition score were –0·05, –0·40 and –0·62.

Offering the supplement reduced forage intake and for treatments U and S respectively, mean daily values were 12·6 and 10·2 g OM per kg live weight. Whilst the supplemented ewes had smaller losses in body condition score in late pregnancy (–0·54 v. –0·28), lamb birth weights and growth rates were significantly increased only for ewes which had carried three or more foetuses in pregnancy and reared their two heaviest lambs.

The effect of pregnancy on the fat and protein contents of milk was studied on a 414-lactation sample. One hundred and forty-nine lactations of non-pregnant cows managed under identical conditions served as controls. The difference between individual fat or protein contents of each pregnant animal and the mean corresponding values in controls was computed weekly from the week of conception. The effect of pregnancy on fat and protein concentrations began to be significant from the 20th week of pregnancy, regardless of the week of conception. It was higher in the Friesian breed than in Holstein or Montbeliarde cows. In Holstein and Montbeliarde cows, the effect of pregnancy was higher in high producing multiparous cows (+2·8 and +2·9 g/kg for fat and protein concentrations, respectively, at the 29th pregnancy week) than in primiparous or low producing multiparous cows (+2·0 and +1·4 g/kg, for fat and protein concentration, respectively). In each of these three lactation groups (Friesian, high producing multiparous Holstein and Montbeliarde cows, other Holstein and Montbeliarde cows) the following linear model

was fitted, where Y is the difference between fat or protein concentration of pregnant and non pregnant cows at a given stage (week), Pw is the pregnancy week, and a and b are parameters. This increase in milk fat and protein concentrations in late pregnancy cannot compensate the concomitant decrease in milk yield, so that fat and protein yield decreased in the same manner as milk yield during pregnancy (-77 glday and -68 glday at the 29th week of pregnancy, for fat and protein yield, respectively).

The European Community's plan to create a single European market by the end of 1992 emphasises that this will be achieved when the Community has done away with physical, technical and fiscal barriers to trade. Physical barriers refer to frontier controls on goods and persons (eg customs, animal and plant health checks, transport restrictions). Fiscal barriers comprise all obstacles and significant distortions among member states that derive from differences in the rates of both VAT and excise duty. Any other obstacles are categorised as technical barriers (eg food compositional laws, additive regulations).

Nineteen field trials were conducted in eight 1 uropean countries to examine the effects of tylosin, administered in the food at a level of 20mg/kg to healthy pigs under good management conditions. Average daily gain and food conversion ratio were improved by 33 g and 0·17 respectively over untreated control animals, with no change in average daily food consumption. These improvements in growth performance were similar in the grower and finisher phases, and the response to tylosin was not affected by sex, initial weight or year. Absolute responses in average daily gain and efficiency of food utilization were constant, whatever the level of performance in the controls.