Two hundred and seventy-seven ewes were used in three experiments during late seasonal anoestrus to evaluate short-term progestogen primings for equine chorionic gonadotropin (eCG)-induced oestrus. In experiment 1, medroxy-progesterone acetate (MAP) sponges were inserted for 6, 9 or 13 days in nulliparous ewes. Percentage of ewes in oestrus (92.3, 85.7 and 96.4%, respectively) and conception rates (66.7, 75.0 and 63.0%, respectively) did not differ among groups (T > 0·05). In experiment 2, MAP sponges were inserted for 1, 2, 3, 6 or 12 days in multiparous ewes. Percentages of ewes in oestrus were higher with 3, 6 or 12 days than with 1 or 2 days of priming (72.2, 93.8 and 87.5% v. 25.0 and 33.3% respectively, P < 0.05) and maximum response was with 6-day priming. From both experiments we conclude that short-term progestogen (6 days) priming is as effective as long-term traditional primings for inducing oestrus. In experiment 3, level of progestogen priming was compared among treatments using a new progesterone releasing device (CIDR) for 6 days, a 6-day used CIDR for 6 days, or an 11-day used CIDR for 6 days. While percentages of oestrous response were similar among groups (95.9, 93.6 and 88.9%, respectively), pregnancy rates were higher with a new CIDR than with one that had been used for 11 days (57.1% v. 27.8%, P < 0.05), with the 6-day used CIDR being intermediate (51.1%). We conclude that a 6-day progestogen priming combined with eCG can be used successfully to induce fertile oestrus in seasonal anoestrous ewes if progestogen levels during priming are kept sufficiently high.

A comparison was made over 2 years of sires of Suffolk and Dutch Texel breeds and ewes of Greyface (Border Leicester × Scottish Blackface), Suffolk Cheviot and Dutch Texel breeds in terms of food intake, prolificacy and lamb growth rates under a grass-based system of production. Suffolk Cheviot ewes consumed significantly more silage dry matter than the Greyface ewes in both years of the study. There was no overall difference between Greyface and Suffolk Cheviot ewes in terms of prolificacy. However lambs from Suffolk Cheviot ewes had a higher growth rate than lambs from Greyface ewes from birth to weaning in year 1 (P < 0·01). In the comparison of the three ewe breeds sired by Dutch Texel rams in year 2, Dutch Texel ewes produced a similar number of lambs to the other genotypes but had a higher incidence of difficult lambings, higher lamb mortality and consequently a lower number of lambs weaned. Purebred Dutch Texel male lambs had lower growth rates than crossbred Dutch Texel lambs (143 compared with 158 glday for lambs from Greyface ewes and 166 (s.e. 13.4) glday for lambs from Suffolk Cheviot ewes in year 1 and 183 compared with 251 and 248 respectively (s.e. 10.9) glday in year 2). Lambs sired by Suffolk rams had higher growth rates than those sired by Dutch Texel rams (252 compared with 224 (s.e. 5.4) glday) in year 2.

Cloning has advanced through the recent demonstrations that it is feasible to produce, in principle and with significant effort, an unlimited number of individuals of identical genotype from differentiated cell lines that have been frozen and thawed. These advances have been based upon understanding the importance of interactions between the stage of the cell cycle of both the oocyte and donor cell for the success of the nuclear transfer. Whilst the impact of the biological advance is immense for biomedicai applications, the significance is less clear for livestock breeding. In our view the scientific issues for breeding programmes lie in whether clones can increase genetic progress without a cost to biodiversity. Biodiversity within a species may be categorized as: (i) betvjeen-breed variation; (ix) genetic variation among parents within breeds; (iii) genetic variation among individuals within a farm; and (iv) allelic variation within an individual. In the face of a rapid global decline in breed diversity, cloning, in particular cloning of adults, may be an important route to protect biodiversity since it may allow far more genetic variation to be made available for new breed development in the future than is practicable at present. For variation among parents, the judicious use of clones may give significantly faster rates of progress without increasing the rate of loss of genetic variation and furthermore can help improve traits associated with health and welfare which are at present less tractable than, say, milk yield. Local diversity within a farm may be greatly affected if cloning is utilized to disseminate genetic progress widely and more answers are required on the importance of genetic variation within any one locality either in buffering diseases or ameliorating other management problems. Experience from clonal forestry can provide some indications but now there are models capable of answering this question directly in livestock. Allelic variation within individuals per se is not generally advantageous but at loci where it is identified to he beneficial, the use of cloning may exploit it more widely.

From 74 to 180 days of age, a complete diet was offered either ad libitum (AL) or at proportionately 0·8 of the observed consumption (R) to two groups of purebred Yorkshire gilts, comprising 128 and 127 animals, respectively. Half of the animals in each group was served at the first detected oestrus, and the other half at the third detected oestrus, according to a plan defined at the start of the experiment. Animals which failed to show oestrus before 240 days of age were culled.

At 100 kg live weight (LW), AL gilts were younger (-20 days) and had thicker backfat (+2.3 mm) than R gilts. At the first detected oestrus, AL females were also younger (198 v. 203 days), heavier (127 v. 117 kg LW) and fatter (17·8 v. 14·7 mm backfat thickness) than R gilts. No difference between feeding treatments during rearing was observed in the percentage of females detected on heat before day 240. Seventy-three animals were culled from the start of the experiment until service, half of them (54%) failing to show oestrus. At service, LW and backfat thickness in the four treatments ranged from 117 to 148 kg LW and 14·9 to 19·7 mm, respectively. The body fatness, estimated from the ratio of backfat to LW, was higher in AL than in R gilts (0·14 and 0·12 , respectively), whereas no difference was observed between E1 and E3 gilts (0·13 on average). After the first service 15% of the gilts came back into heat but the conception rate was not affected by feeding treatment during rearing.

A feeding system, draught cows, disease/work interactions and animal power introduction in a farming system, four areas of recent research on draught ruminants which are important to future development of animal power, are reviewed. A new feeding system for draught animals is described which enables food requirements and the effects of work on live weight and milk production to be calculated.

Recent data on the energy cost of walking are appraised. Research on working cows, mainly in Ethiopia, has shown that undernutrition has a greater effect on milk yield than work, which has a transient effect. The length of the post-partum anoestrous period increases with decrease in body condition. Body-weight loss increases with increasing work load. It is suggested that dairy cows delay conception by 1 day for every day of work done. Work has little effect on food intake or digestive parameters. Although it is associated with an overall increase in food intake of cows, even of un-supplemented forage diets, the increase is not sufficient to meet all the extra energy needs for work. Food intake of both working and non-working cows increases during lactation.

Disease limits the working capacity of draught animals and work can exacerbate disease. These effects were investigated using Trypanosoma evansi in Indonesia and T. congolense in The Gambia. In both studies, infected animals were able to do much less work than non-infected ones and the severity of the effect depended greatly on the strain of trypanosome used. In general, increasing the plane of nutrition did not ameliorate the effects of the disease, nor in the Gambian study did it prevent loss of appetite in infected animals.

The technical and agronomic innovations necessary for the introduction of animal power into an inland valley region of central Nigeria are described and some of the sociological implications discussed.

The pattern of follicle activity and fibre growth on the neck, mid side and rear leg of 12 Scottish Cashmere (SC) and nine Siberian (S) goat kids was examined from birth to 255 days of age. In both genotypes maximum secondary to primary follicle (S/P) ratio was reached earliest on the neck (P < 0·05) but was proportionately 0·21 and 0·28 (P < 0·001) lower than that on the rear leg and mid side respectively. Secondary follicle activity ceased earlier on the rear leg than the mid side or neck (P < 0·001) and this was associated with lower staple lengths and patch weights of undercoat. Fibre weight and diameter were compared on six body parts: neck, front leg, mid side, rear leg, rump and belly at 255 days of age. Patch undercoat weights and diameter were greatest on the neck, front leg and rump and lowest on the belly.

The estimated annual production of undercoat, calculated from patch weights and skin area measurements on the six parts of the body at 255 days of age was 138 (range 42 to 260) g for SC kids and 525 (range 377 to 661) g for S kids (s.e.d. = 39·4, P < 0·001). Mean undercoat diameter was 16·15 (range 15·32 to 17·51) and 18·94 (range 17·25 to 19·89) μm for SC and S kids respectively (s.e.d. = 0·376, P < 0·001).

Correlation coefficients between fibre traits, measured at approximately monthly intervals and estimates of annual production and undercoat diameter at 255 days were calculated. For SC kids mid-side patch undercoat weight was consistently and strongly related to estimated annual production (mean correlation coefficient, 0·85, s.e. 0·036). For S kids the only variable to show a consistently strong relationship with estimated annual production was mid-side undercoat staple length × diameter2 (mean correlation coefficient 0·66, s.e. 0·067). Thus the best fibre traits for ranking annual production differed between genotypes. In both cases the accuracy of the ranking increased with age. Undercoat fibre diameter measured from 4 to 5 months of age was closely related to estimated undercoat diameter at 255 days of age in both SC and S genotypes (mean correlation coefficient 0·92, s.e. 0·009). Prior to 4 months of age the mean correlation coefficient for SC and S genotypes was 0·53 (s.e. 0·20).

It is concluded that goat kids can be ranked for annual production and diameter of the undercoat, prior to first harvesting, based on fibre traits measured on samples of the fleece.

This review addresses the reasons for the lack of progress in the control of superovulation and highlights the importance of understanding the mechanisms underlying follicular development. The present inability to provide large numbers of viable embryos from selected females still restricts genetic improvement, whilst variability in ovarian response to hormones limit the present capacity for increasing reproductive efficiency.

Females are born with a large store of eggs which rapidly declines as puberty approaches. If these oocytes are normal then there is scope for increasing the reproductive potential of selected females. Oocytes must reach a certain size before they can complete all stages of development and the final changes that occur late in follicular development. It is likely that oocytes that do not produce specific factors at precise stages of development will not be viable. Hence, it is important to characterize oocyte secreted factors since there are potential indicators of oocyte quality.

The mechanisms that determine ovulation rate have still not been fully elucidated. Indeed follicular atresia, the process whereby follicles regress, is still not known. A better understanding of these processes should prove pivotal for the synchronization of follicular growth, for more precise oestrous synchronization and improved superovulatory response.

Nutrition can influence a whole range of reproductive parameters however, the pathways through which nutrition acts have not been fully elucidated. Metabolic hormones, particularly insulin and IGFs, appear to interact with gonadotrophins at the level of the gonads. Certainly gonadotropins provide the primary drive for the growth of follicles in the later stages of development and both insulin and IGF-1, possibly IGF-2, synergize with gonadotrophins to stimulate cell proliferation and hormone production. More research is required to determine the effects of other growth factors and their interaction with gonadotropins.

There is evidence, particularly from studies with rodents, that steroids can also modulate follicular growth and development, although information is very limited for ruminants. There may be a rôle for oestrogens in synchronizing follicular waves, to aid in oestrous synchronization regimes and for removing the dominant follicle to achieve improved superovulatory responses. However more information is required to determine whether these are feasible approaches.

Heritability for litter size is higher in sheep than in cattle. Exogenous gonadotropins are a commercially ineffective means of inducing twinning in sheep and cattle. Although there are differences in circulating gonadotropin concentrations, the mechanism(s) responsible for the high ovulation appear to reside essentially within the ovaries. The locus of the Booroola gene, a major gene for ovulation rate, has been established but not specifically identified. However sheep possessing major genes do provide extremely valuable models for investigating the mechanisms controlling ovulation rate, including a direct contrast to mono-ovulatory species such as cattle.

In conclusion, the relationship between oocyte quality, in both healthy follicles and those follicles destined for atresia, must be resolved before the future potential for increasing embryo yield can be predicted. In addition, a greater understanding of the factors affecting folliculogenesis in ruminants should ensure that the full benefits ensuing from the precise control of ovarian function are achieved. The improved use of artificial insemination and embryo transfer that would ensue from a greater understanding of the processes of folliculo genesis, coupled with the new technologies of genome and linkage mapping, should ensure a more rapid rate of genetic gain.

A 2 x 2 factorial experiment was designed in order to study the effects of feeding level during rearing and of mating policy on the reproductive performance and food intake of first- and second-litter sows. Gilts were offered food during rearing either ad libitum (AL) or at 0·8 of the AL level (R) and served either at first (E1) or third (E3) detected oestrus. A total of 160 out of the 243 animals that started the experiment were culled by the end of the second lactation, with significantly more R than AL animals (71 and 60%, respectively). During the first pregnancy, the R sows gained more live weight (LW) and backfat thickness (BF) than their AL contemporaries (+5 kg and +1.2 mm, respectively) and lost less BF during the first lactation (1.2 mm less). At weaning, no difference remained in LW or BF between AL and R sows (174 kg LW on average). The E3 females gained less LW during both pregnancies compared with those on the E1 treatment, but they remained heavier until the second weaning (208 kg, on average). During the first lactation, R consumed more food during the weeks 2 and 3 (by 0·5 kg/day, on average) than those reared previously on the AL regime, and no difference was observed between E3 and E1 females. No difference in food consumption was noted during parity two. However, when measured over the first two parities, lean animals consumed more food than fat animals. The size and the weight of the litter at birth or at weaning were not influenced by the treatment prior to service. The weaning-to-oestrus interval was longer during parity one than during parity two (5·7 and 5·0 days, respectively; P < 0·01) but it was not affected by feeding or mating treatment.

In a previous experiment the provision of straw to group-housed pigs increased the number of daily feeder visits. This effect of straw is comparable with conditions of reduced social competition for access to the feeder. The aim of this experiment was to investigate if changing straw provision within a pen resulted in similar and reversible effects in this behaviour. One hundred and twenty male pigs (41·1 (s.e. 0·43) kg) were used in three blocks each of four pens of 10 pigs. In each block of 42 days duration one pen had no straw throughout (treatment 1); one pen had no straw for 21 days (period 1) followed by straw for 21 days (period 2) (2); one pen had straw followed by no straw (3) and one pen had straw throughout (4). The pens were situated in a naturally ventilated building with light from 06.00 to 20.00 h. Each pen had a kennel, a lying area and a single-space computerized feeder for recording feeding behaviour. The pigs’ activity was recorded on video in the 2nd and 5th weeks of each block. The number of feeder visits was slightly higher for pigs with straw (1: 9·69 v. 4: 10·46) but this was not significant (P > 0·05). The effect was more marked for treatment 2 where the visits increased (P < 0·01) from period 1 (8·52) to period 2 (10·64) and for treatment 3 where they decreased (11·20 v. 10·10). Pigs without straw (treatment 1) spent more time in the kennel than those with straw (treatment 4) (P < 0·05). For treatment 2 the proportion of time spent in the kennel fell from 0·607 in period 1 to 0·288 in period 2 (P < 0·01). There was a general trend for more activity and more lying outside the kennel when straw was provided. The effect of straw provision was not as marked as that seen previously; nevertheless changing straw provision (treatments 2 and 3) did result in an increase in feeder visits with straw, probably related to the increase in general activity and lying outside in the area adjacent to the feeder.

Artificial insemination, superovulation and embryo transfer have had beneficial impacts on animal production but a limiting factor to realizing the full potential of these techniques and of other reproductive technologies is the availability of fertile oocytes. To overcome this problem, methods for maturing oocytes in vitro (IVM) have been developed. The production of bovine embryos by IVM is in commercial use but the rate of success and quality of embryos is low. The lack of success may be due to the quality of oocytes that are being matured and it would be preferable to utilize the abundant source of immature oocytes from preantral and primordial follicles by developing systems for in vitro growth (IVG). Several culture systems that utilize early growing follicles as a source of oocytes have been developed for laboratory species and these have been successful in producing live young. IVG in association with IVM and cryopreservation have the potential to maximize the genetic potential of high genetic merit females and shorten generation intervals. This paper presents the current status of technology for the in vitro growth and development of immature oocytes, in vitro maturation and cryopreservation of germ cells in domestic ruminants.

An experiment was conducted with 48 dairy cows grazed in treatment groups of four, eight or 16 cows per group, whose grazing, social and resting behaviour was recorded over a 53-day period. Cows in groups of four stayed closer to their nearest neighbour, moved their head more rapidly from side to side during grazing and spent more time ruminating than cows in larger groups, suggesting that they were more vigilant against a perceived prédation risk. Cows in the group of 16 were more aggressive, maintained a greater distance to their nearest neighbour and had a faster rate of stepping while they grazed, compared with cows in smaller groups, suggesting increased inter-cow competition. They also spent longer grooming themselves, which normally acts as a displacement activity and may indicate increased stress. Cows in groups of eight had a faster biting rate when grazing than cows in small or large groups and they spent the longest time lying down. There were no effects of group size on milk production but across treatment groups the high yielding cows were the first to initiate grazing and to enter the milking parlour.

Various dairy cattle production and health characteristics were studied with a view to identify easily available and measurable factors associated with the incidence of ketosis. The analyses were carried out using data from the Langhill Dairy Cattle Research Centre. Two approaches were used to assess the relative risk to cows of getting ketosis: one using information known at the beginning of lactation and one using information collected as the lactation progressed. In both approaches analyses were carried out using different amounts of the available information to simulate differences between recording systems. In the first approach the following were found to relate significantly to the level of recorded ketotic incidents: parity; ketosis in the previous lactation; calving condition score; 305-day milk yield in the previous lactation; and the average milk protein percentage in the previous lactation. The effects of these were quantified. In the second approach, where the change in ketosis incidence rate over the weeks of lactation was investigated, the average dry-matter intake in the previous week and changes in live weight and body condition score over the previous week were found to have a significant effect on the probability of getting ketosis in the coming week. The risk assessments varied depending on the information used and a flexible approach is recommended if potential risk factors are to be successfully incorporated into decision support systems.

The influence of environmental stimuli considered biologically relevant for nest building sows, on nursing and suckling behaviour and piglet growth was investigated. Effects of floor type (beach sand v. concrete) and substrate type (straw feeder v. no straw feeder) were examined in a 2 × 2 factorial experiment with nine replicates of four multiparous sows. The sows were kept individually in roofed 7·6 m2 ‘get-aw ay-pens’ from 1 week pre-partum until 13 to 15 days post-partum. The behaviour of sows and piglets were video recorded for 24 h on days 0, 3, 6 and 12 post-partum.

The latency from termination of farrowing until perceptible milk ejection tended to be shorter for experienced sows (parity 4 to 5) kept on sand than on concrete floors (1207 (s.e. 109) min; no. = 7 v. 1725 (s.e. 123) min; no. = 6, respectively; F2,8 = 3·93, P < 0·07) and for experienced sows with access to a straw feeder than without access to a straw feeder (1257 (s.e. 113) min; no. = 8 v. 1666 (s.e. 132) min; no. = 5, respectively; F2,8 = 3·56, P < 0·08). On days 3 and 6 a longer duration of suckling was found for sows on sand v. concrete floors (384 (s.e. 20) v. 327 (s.e. 16) s on day 3; F1,19 = 5·6, P < 0.03 and 377 (s.e. 14) v. 318 (s.e. 13) on day 6; F1,21 = 9·09; P < 0·01, respectively) and with straw feeder v. without straw feeder (385 (s.e. 20) v. 326 (s.e. 18) s on day 3; F1,19 = 5·11, P < 0.04 and 372 (s.e. 14) v. 323 (s.e. 13) on day 6; F1,21 = 6·21; P < 0·03, respectively). On day 3, a tendency for a sand × straw feeder interaction (F11,8 = 3·58, P < 0.08), showed that sows without environmental stimuli terminated more sucklings than sows with access to a straw feeder and sows kept on sand (32 (s.e. 7) %, 16 (s.e. 4) % and 13 (s.e. 5) %, respectively). Similarly, on day 6 a significant sand × straw feeder interaction (F316 = 7·15, P < 0·01) led to increased frequency of foreleg rowing for sows without environmental stimuli compared with the three other treatments (14 (s.e. 2) v. 7 (s.e. 1), 5 (s.e. 1) and 6 (s.e. 1) foreleg rowings per h, respectively). During the stay in the experimental pens, the growth rate of piglets kept on sand tended to be higher than for piglets kept on concrete floors (261 (s.e. 33) v. 240 (s.e. 30) g per piglet per day; F1,25 = 3·38; P < 0·08).

The results of the present experiment indicate that provision of biologically relevant stimuli affect the nursing and suckling behaviour of sows and piglets. The reduced termination of sucklings, the reduced frequency of foreleg rowing, the increased duration of suckling as well as the earlier development of suckling behaviour might have been advantageous for the early milk intake of the piglets.

The effects of high and low dietary dietary intake on reproduction in female cattle and sheep will be considered at the level of the pituitary gland, ovary and uterus. In sheep, increased dietary intake for a relatively short time will increase ovulation rate, by increasing gonadotropin secretion. Dietary intake can affect steroids such as progesterone and also intra-follicular concentrations of some growth factors such as IGF-1 and IGF-2. The effects of altered energy intake on gonadotropins and steroids in cattle are not as repeatable as those in sheep but follicular growth rates can be altered. High nutrition has a negative effect on oocyte quality, with animals on ad-libitum high energy diets particularly at risk. Overfeeding can decrease embryo quality in both sheep and cattle and it appears that this results from changes primarily at the level of the follicle or oocyte. Restricted nutrition for a short time will enhance pregnancy rates in cattle; most of this benefit appears to occur if food is restricted before insemination. Thus feeding levels before mating are particularly important to subsequent reproductive success. High dietary crude protein may decrease pregnancy rate in lactating cows. In ewes and heifers supplementation with urea failed to have any effect on pregnancy rates when good quality embryos were transferred to recipient animals exposed to high dietary crude protein. In donor ewes there were adverse effects on early embryo development following urea treatment, suggesting that the mechanism affecting the reproductive process was primarily operating at the level of the oocyte. Collectively, these data identify the overall deleterious effects of high dietary intake and excess crude protein on fertility and highlight the importance of dietary intake before ovulation on the likelihood of establishing a viable pregnancy.

The present study was performed to find out how dairy cow behaviour and the level of the adrenocortical hormone cortisol were influenced by feeding in relation to milking The experiment was designed as a Latin square and performed on 24 primiparous and multiparous Swedish Red and White dairy cows. Each treatment period lasted for 21 days, including 11 days when the cows became accustomed to the new routines. The cows were exposed to three treatments: feeding 1·5 h before milking (FBM), feeding exactly at the same time as milking (FDM) and feeding 1·5 h after milking (FAM). Recordings of individual behaviour were made with instantaneous direct observation of each cow. For the statistical analyses the recordings were divided into two groups: 0 to 1·5 h after feeding and 0 to 1·5 h after milking. Results with a P-value below 0·05 were regarded as statistically significant. The interesting findings in this study were: (a) 0 to 1·5 h after feeding, the percentage of lying was higher in FDM and the percentage of lying while ruminating was higher in FDM; (b) 0 to 1·5 h after milking, the cows in FAM had a significantly lower percentage of social interactions and a significantly higher percentage of oral activity; and (c) feeding-related level of cortisol stayed higher 30 to 60 min after feeding in FAM compared with FBM and FDM, whereas milking-related cortisol secretion tended to be lower in FDM than in FBM and FAM These results demonstrate that feeding during milking may be an important management routine, also for dairy cow behaviour.

The trade-off made by pigs between exposure to a concentration of ammonia gas recorded in commercial piggeries and thermal comfort was observed in two chronic choice tests. In the first experiment, eight pigs which were paired and eight pigs which were held as singles, were forced to choose between compartments of a preference chamber that were polluted with an ammonia gas concentration of 40 p.p.m. and heated with a 750 W radiant heater or compartments that were unpolluted and unheated, for 8 days. The location of the choice options was switched after 4 days to eliminate positional bias. Air temperature ranged from 0·5 °C to 15·0 °C. In the second experiment, eight pigs held as pairs, were free to choose between compartments that were polluted with an ammonia gas concentration of 40 p.p.m. and heated with a 750 W radiant heater, polluted and unheated, unpolluted and heated and unpolluted and unheated, for 14 days. The location of the choice options was switched after 7 days to eliminate positional bias. Air temperature ranged from 4·0 °C to 24·0 °C. All compartments contained food and water ad libitum; wood shavings were used as bedding material. In both experiments, the location of all pigs was scan sampled every 15 min and their behaviour at this time was recorded instantaneously. Location and behaviour were compared against air temperature. In the first, forced choice experiment, the pigs preferred the heated-polluted compartments when air temperature was less than the estimated lower critical temperature (LCT) (P < 0·001). As air temperature approached the estimated LCT, the pigs occupied the unheated-unpolluted compartments more often. Overall each visit made to the heated-polluted compartments lasted significantly longer at 265 min (paired), 208 min (single) than visits to the unheated-unpolluted compartments at 29 min (paired), 31 min (single) (P < 0·001). Although they could have huddled to conserve heat, the paired pigs spent less time, overall, in the unheated-unpolluted compartments (P < 0·001). When air temperatures were lower than the estimated LCT, the pigs huddled together but as air temperature increased, the pigs spent more time resting apart (P < 0·001) in the heated-polluted compartments. It is suggested that the paired pigs were motivated to remain in the heated-polluted compartments for companionship rather than thermal comfort. In the second, free choice experiment, the pigs preferred to remain in the unpolluted compartments, adjusting their occupancy of the heated and unheated compartments as ambient air temperature decreased or increased above the estimated LCT (P < 0·001). The pigs made fewer visits to the polluted compartments and each visit was shorter, at 44 min (P < 0·001). Visits to the unpolluted compartments lasted for 291 min. It is suggested that the delayed aversion shown to ammonia in both experiments was due to a progressive sense of malaise. However, both experiments indicated that this delayed ammonia aversion was weaker than preference for thermal comfort.

The emphasis in nutritional studies on foetal growth has now moved from the last trimester of pregnancy, when most of the increase in foetal size takes place, to earlier stages of pregnancy that coincide with foetal organogenesis and tissue hyperplasia. At these stages absolute nutrient requirements for foetal growth are small but foetal metabolic activity and specific growth rate are high. It is thus a time when nutrient supply interacts with maternal factors such as size, body condition and degree of maturity to influence placental growth and set the subsequent pattern of nutrient partitioning between the gravid uterus and maternal body.

Throughout pregnancy the maternal diet controls foetal growth both directly, by supplying essential nutrients and indirectly, by altering the expression of the maternal and foetal endocrine mechanisms that regulate the uptake and utilization of these nutrients by the conceptus. Nutritional effects on the endocrine environment of the embryo during the early stages of cell division can alter the subsequent foetal growth trajectory and size at birth; so too can current in vitro systems for oocyte maturation and embryo culture up to the blastocyst stage. There is increasing evidence that subtle alterations in nutrient supply during critical periods of embryonic and foetal life can impart a legacy of growth and developmental changes that affect neonatal survival and adult performance. Identifying the specific nutrients that programme these effects and understanding their mode of action should provide new management strategies for ensuring that nutritional regimens from oocyte to newborn are such that they maximize neonatal viability and enable animals to express their true genetic potential for production.

The main objective of the experiment was to investigate whether a continuum links the development of conditioned flavour preferences and conditioned flavour aversions (CFPs and CFAs) in sheep, towards food flavours associated with intraruminal administration of increasing doses of the same nutritive stimulus: casein. A secondary objective was to investigate the effects of dose of casein administration and the number of repeated exposures to casein on the rate of establishment, magnitude and degree of persistence of developed CFPs and CFAs.

The experiment consisted of three conditioning periods (each lasted 8 days). A food with low crude protein (CP) (39.3 g/kg dry matter (DM)) and metabolizable energy (ME) (5.3 MJ/kg DM) contents was used in combination with one of two flavours, orange and aniseed, on a total of 48 Texel × Greyface male, 3-month-old sheep. The sheep were conditioned to associate one flavour added to the test food with a particular dose of casein (C) suspended in water (8.75, 17.5, 35 and 52.5 g per animal), or a different flavoured test food with an equal amount of water. Each dose was administered by gavage through a stomach tube twice daily to each animal. At the end of each conditioning period the preference for the two flavours was measured by a two choice preference test between the two flavoured test foods for 40 min. After the completion of the last conditioning period, three more preference tests (persistence tests), without any intervening exposure to the flavoured test food, were conducted at 7, 21 and 35 days. Preference for the flavoured test food paired with casein was affected by the interaction (P < 0·001) between the dose of casein and casein association respectively. Association with casein (DPR: intake of a flavoured test food paired with casein per g total intake of flavoured test foods during the preference test) led to CFPs (DPR > 0·70) at the two lowest and to CFAs (DPR < 0·30) at the two highest doses. CFPs and CFAs were established by the second conditioning and there was no difference in the rate of establishment between preferences and aversions. The persistence tests showed a strong and similar degree of persistence of both formed CFPs and CFAs, since these were not affected by time of persistence test or by any of the interactions with time. In view of these results a model is proposed which could account for the conditioned responses of sheep towards administration of increasing doses of the same nutrient. The existence of a continuum between CFPs and CFAs created by the same nutrient given at different doses, could be the basis of how ruminants select a diet which meets their nutrient requirements at a particular point in time and thereby avoid excess of nutrient intake.

Performance of 80 (tests 1 and 2) or 60 (tests 3 and 4) weaned pigs were compared when using ‘Tubetype’ feeder (T), allowing the animals to mix meal and drinking water, or another type (V) where drinking and eating places are separated. The difference in growth rate was not significant but the mean daily water consumption (1 per pig per day) was higher with T than with V in each test but significantly only in tests 1 and 3 (1·84 v. 1·40, and 2·11 v. 1·26, P < 0·01).

Feeding behaviour was assessed during tests 2 and 4. Multifactor analysis of variance revealed effects (P < 0·01) of feeder, group size and period of the day on the occupation time and the average number of animals using the feeders simultaneously. These two variables were higher for V than for T (test 2: 23·4 per 24 h v. 21·5 per 24 h and 4·5 v. 3·7, P < 0·05; test 4: 20·0 per 24 h v. 18·2 per 24 h, P< 0·01). In each test, both feeders were used for a longer time and by more piglets during the ‘day’ than during the ‘night’ (P < 0·01). When grouping 40 pigs, animals used both feeders during almost all the day period (V: 15·9 per 16 h and T: 15·8 per 16 h). During the night period, this was only true with V (V: 7·4 per 8 h; T: 5·8 per 8 h). The use of feeder V in crowded conditions thus prevented preferential diurnal feeding activity, commonly described in pigs. In conclusion, even if productivity is not affected, feeding behaviour and thus eventually welfare are influenced by the type of feeder, especially with high numbers of animals.