Censoring of records is a problem in the prediction of breeding values for longevity, because breeding values are required before actual lifespan is known. In this study we investigated the use of random regression models to analyse survival data, because this method combines some of the advantages of a multitrait approach and the more sophisticated proportional hazards models. A model was derived for the binary representation of survival data and links with proportional hazards models and generalized linear models are shown. Variance components and breeding values were predicted using a linear approximation, including time-dependent fixed effects and random regression coefficients. Production records in lactations 1 to 5 were available on 24741 cows in the UK, all having had the opportunity to survive five lactations. The random regression model contained a linear regression on milk yield within herd (no. = 1417) by lactation number (no. = 4), Holstein percentage and year-month of calving effect (no. = 72). The additive animal genetic effects were modelled using orthogonal polynomials of order 1 to 4 with random coefficients and the error terms were fitted for each lactation separately, either correlated or not. Variance components from the full (i.e. uncensored) data set, were used to predict breeding values for survival in each lactation from both uncensored and randomly censored data. In the uncensored data, estimates of heritabilities for culling probability in each lactation ranged from 0·02 to 0·04. Breeding values for lifespan (calculated from the survival breeding values) had a range of 2·4 to 3·6 lactations and a standard deviation of 0·25. Correlations between predicted breeding values for 129 bulls, each with more than 30 daughters, from the various data sets ranged from 0·81 to 0·99 and were insensitive to the model used. It is concluded that random regression analysis models used for test-day records analysis of milk yield, might also be of use in the analysis of censored survival data.

Previous studies examining the effect of age on gilt reproduction have generally failed to discriminate between chronological (i.e. days) and physiological age (i.e. number of oestrous cycles experienced) and the importance of each factor remains unclear in the pig. The present investigation tested the hypothesis that the physiological age at which gilts are bred in a dynamic service system (DSS) affects their reproductive behaviour and performance. A hundred and ninety gilts were randomly allocated between two treatments. They were introduced into the service pens of a DSS to be bred at the same age (215 days) but either at second (2H; no. = 96) or third (3H;no. = 94) post-pubertal heat period. The sexual behaviour of half of them was continuously recorded over a 13-week period and reproductive data from all the gilts were collected. Gilts of 2H treatment were significantly heavier at entry into the service pens (123 v. 119 kg; P < 0·05) than 3H gilts, but there was no significant difference in their backfat thickness. Treatment failed to affect the quality and frequency of mating attempts (MAs) gilts received or oestrus duration. Conception rate to first oestrus in the DSS (82%) was not affected by treatment. Litter size and number of piglets born alive was similar for 3H and 2H gilts (12·0 v. 11·7, s.e.d. 0·40 and 11·5 v. 11·0, s.e.d. 0·4 respectively; all P > 0·05). It is concluded that the reproductive behaviour and performance of gilts that had experienced either two or three oestrous cycles prior to mating at a constant age does not differ significantly in a DSS. More studies are needed in order to clarify the possible interactive influence of repeated and frequent services, which are common in a DSS, on gilt reproduction.

The objectives of this study were to establish what changes in posture by sows carried a high risk of piglet crushing in a group farrowing system during early lactation and also to determine what factors influenced the risk of crushing during lying down. A total of 24 Large White ✕ Landrace sows were studied during the first 7 days of lactation in a group farrowing system. Cross-fostering was not carried out so as not to influence behaviour. Dead piglets were removed and cause of death ascertained from external observation and post-mortem examination. Sow and piglet behaviour was video-recorded continuously. A total of 268 piglets were born alive, with 67 liveborn piglets subsequently dying during the 7-day experimental period, 50 as a result of crushing. A total of 7425 posture changes were analysed and 11 types of posture change were identified, the most dangerous being lying down from standing and those involving swapping sides, or rolling over, whilst lying.

Dangerous events during lying down were more likely to occur (1) in the first 24 h after farrowing, (2) when the sow lay down in the middle of the pen, (3) when the sow lay down without carrying out much piglet-directed pre-lying behaviour and (4) when the piglets were spread out but near to the sow. The amount of pre-lying behaviour decreased over time and crushing mortality also decreased. The results confirm that the piglets are most vulnerable to crushing during the first 24 h of life, when they are spending much of their time near the udder and have relatively poor mobility. Co-ordination of behaviour between the sow and her litter is important to reduce the risk of crushing. It is also important that the design of open farrowing systems incorporates knowledge about how crushing deaths occur in order to improve piglet welfare.

In order to avoid the decrease in the numbers of wild red-legged partridge, Alectoris rufa, observed in several areas, the most appropiate solution is to repopulate using animals from game farms. The nesting place chosen by 30 pairs of red-legged partridge in captivity was studied. There were five different nest types combined in groups of three in 30 cages. Type A nest: made with natural bush plants tied together at one end and placed invertedly forming a cone. Type B: made with the same natural bush plants as the previous type but placed over an internal wire structure and having preformed entrances. Type C: a wooden structure in the form of a roof with two slopes. Type D: similar to the type C but on one of the laterals the opaque material only covers the upper half, and a plastic mesh covers the lower half. Type E: a wooden square box covered with an inclined plank of opaque and waterproof material. Our study shows that the type A nest received significantly (P < 0·05) more eggs than the others, possibly because this type of nest allowed for better vigilance and a better sense of protection for the animals. Type E nest was the second most preferred. In this type, the partridge was able to monitor the surroundings through the space between the walls and the roof and this space could be used as an escape route. From a production and industrial perspective, type E has some advantages over type A, being easy to build, clean and disinfect, and allowing the birds to see through the nest.

In a comparative study which examined the effect of having access to mushroom compost in an otherwise barren environment there were three treatments and six replicates. The three treatments were (T1) control barren pen providing 0·7 m2 per pig with fully slatted floor, (T2) empty horizontal rack suspended above the pigs’ heads and (T3) mushroom compost on rack as in treatment 2. Pigs released particles of compost from the rack by nosing the metal grid from below. Almost twice as many pigs with access to mushroom compost (T3) nosed the rack (P < 0·001) and the ground below the rack (P < 0·001) as pigs which had a rack with no mushroom compost (T2). Fewer pigs with mushroom compost were involved in behaviours directed at penmates such as nosing, biting and chewing penmates than pigs in treatments 1 and 2 (P < 0·001). In addition fewer pigs in T3 were involved in feeding behaviour than in T1 and T2 (P < 0·05). Percentages of tail-bitten animals which had to be removed were 11 and 24 for T1 and T2 respectively while T3 had < 1% removed because of tail biting (P < 0·05). Apparent food intake was higher (P < 0·05) and food conversion ratio tended to be poorer in T1 (P = 0·1). It is suggested that pigs will redirect rooting behaviour towards penmates and the feeder in the absence of any rooting substrate. Adding substrate to commercial finishing pens reduces this redirection of behaviour and improves welfare by minimizing injury through tail biting.

Two experiments were conducted to investigate the effect of expander processing of food for growing and finishing pigs. Experiment 1 examined the effects of expander processing on the nutritive value of a cereal-based diet and a pea-based diet for pigs while experiment 2 determined the effects of extrusion and expansion of the peas component of the diet on the nutritive value. In experiment 1, growth performance, carcass characteristics (no. = 12) and nutrient digestibility (no. = 4) were determined in pigs offered individually food containing a cereal diet (T1), a complete cereal diet that had been expander processed (T2), a 400 g/kg peas diet (T3) or a complete 400 g/kg peas diet that had been expander processed (T4). The expanded diets were processed at 105°C for 5 s at 35 bar pressure. In experiment 2, productive performance and nutrient digestibility were determined in pigs (no. = 12) offered individually diets including a control cereal diet (no peas) (TT1), a 400 g/kg raw peas diet (TT2), a 400 g/kg expander processed peas diet (TT3) or a 400 g/kg extruded peas diet (TT4). The pea portions of the diets were extruded at 130°C for 30 s and expanded at 130°C for 10 s at 42 bar pressure. In experiment 1, the inclusion of peas in the diet reduced (P < 0·001) the digestibility of the organic matter (OM) (0·871 v. 0·893, s.e. 0·003), protein (0·867 v. 0·907, s.e. 0·004) and energy (0·857 v. 0·880, s.e. 0·003). Expansion had no effect on the nutrient digestibility of the diets, however, it did increase (P < 0·05) the digestible energy content of the cereal diet. The inclusion of peas in the diet reduced (P < 0·05) daily gain (0·929 v. 0·999, s.e. 0·024 kg/day) and increased (P < 0·001) food conversion ratio (FCR) (2·31 v. 2·16, s.e. 0·029) from 34 kg to slaughter. Expansion had no effect on daily gain or FCR. In experiment 2, OM digestibilities of 0·891, 0·872, 0·882 and 0·885 (s.e. 0·0042) (P < 0·01), protein digestibilities of 0·905, 0·879, 0·874 and 0·877 (s.e. 0·0069) (P < 0·001) and gross energy digestibilities of 0·875, 0·861, 0·870 and 0·875 (s.e. 0·005) (P < 0·05) were recorded for TT1 to TT4 respectively. Gains (kg/day) of 0·981, 0·927, 0·940, and 1·016 (s.e. 0·036) (P < 0·05) and FCR of 2·17, 2·32, 2·28 and 2·18 (s.e. 0·037) (P < 0·05) were recorded for TT1 to TT4 respectively. In conclusion, expansion had no effect on the nutritive value of food for pigs.

Pony colts (~12 m) are generally infertile during the breeding season of mature stallions. The mechanism which ‘delays’ puberty beyond the first potential breeding opportunity has not been described. Four pre- and four post-pubertal colts were monitored from November for 13 (group 1, 6 to 19 months of age) and 9 months (group 2, 18 to 27 months of age). Fortnightly, 15 blood samples were collected at hourly intervals from each colt to determine concentrations of prolactin (PRL), LH, FSH and testosterone (T). Testicular biopsies were collected monthly to evaluate spermatogenic activity. Puberty occurred between 17 and 19 months, and at the onset of the 2-year-old breeding season, all colts were fertile. Seasonal changes in the concentrations of all four hormones were observed in both groups. Prolactin concentrations were correlated with changes in day length (r = 0·88) in both groups, but a biphasic profile was noted in group 1. Moulting of the winter coat was coincident with seasonally increased PRL concentrations (P < 0·001). Seasonal changes in FSH, LH and T concentrations were similarly timed between groups and levels were maximal in mid April, mid March and mid May, respectively. However, overall mean concentrations of LH and T in group 1 animals were only 0·33 and 0·22 of group 2 values (P < 0·001). Suppression of gonadal activity during the colts’ first ‘quiescent’ breeding season was associated with low concentrations of circulating LH. Appropriately timed changes in plasma PRL, FSH and T concentrations and pelage indicated that the photoperiodic mechanism was functional in the pre-pubertal colt but pituitary LH release may be blocked by immaturity or active suppression.

Relationships among photoperiod and changes in voluntary food intake, feeding behaviour, growth and pelage were determined in seven, 2-year-old pony colts (182·4 (s.e. 5·4) kg). Individually housed colts were provided with ad libitum access to a complete pelleted diet (gross energy = 16·7 MJ/kg dry matter). Voluntary food intake (VFI, kg/ day) was calculated daily and body weights were recorded weekly throughout the 36-week study. Feeding behaviour was evaluated at approximately 4-week intervals by continuous observation (24 h), and the hair weight density (HWD, mg/cm2) of shoulder pelage was determined fortnightly. Day length was artificially manipulated to mimic the prevailing mid-summer photoperiod (16 h light: 8 h dark, 16L: 8D). After 1 week of the study (and the preceding fortnight), day length was abruptly decreased and thereafter animals were exposed to alternating 14-week periods of short (SD, 8L: 16D) and long days (LD, 16L: 8D). The mean daily VFI of individual ponies was calculated weekly and normalized for digestible energy (DE) content and metabolic body weight (DEI, MJ/kg M0·75). The average daily gain (ADG, kg/day) in body weight of each individual was calculated weekly. The apparent digestibility of dietary energy (digestibility) was determined over 72 h (no. = 6) on two occasions (days 92 to 95 and 190 to 193) during the study. Digestibility was similar in both periods (0·48, s.e. 0·01). DEI, ADG and HWD changed in a cyclic manner throughout the study. The period of the appetite cycle (24·4 (s.e. 1·3) weeks) did not differ from that of the 28-week photoperiodic regime. DEI decreased from a maximum of 1·4 (s.e. 0·03) MJ/kg M0.75 per day (day 21), to a nadir of 0·75 (s.e. 0·02) MJ/kg M0.75 per day (day 154, P < 0·001) and had increased (P < 0·001) to attain a second zenith (0·93 (s.e. 0·01) MJ/kg M0.75 per day) before the end of the study. Ponies ate discrete meals of similar duration, but meal frequency was associated with changes in VFI (r = 0·77) as was proportion of time spent feeding (r = 0·79). Changes in ADG reflected those of DEI. Body weight was stable for 4 weeks at the nadir of the appetite cycle. Maximal HWD was coincident with the nadir of the appetite and growth cycles. Regression of individual values for DEI on ADG described a linear relationship (R2 = 0·80) which could be used to predict the energy requirements of growing ponies maintained under similar conditions:

DEI total (MJ/kg M0·75 per day) = 0·654ADG (kg/day) + 0·789 (1).

The duration of the photoperiod, appetite, growth and pelage cycles were similar, suggesting a causal relationship. Physiological responses to photoperiodic change were not immediate and exhibited a delay of 5 to 8 weeks.

A number of behavioural problems are associated with weaning piglets including belly nosing, ear and tail biting, and low intake of solid food. These appear to be less pronounced in piglets reared on outdoor systems, which initially consume more solid food and show less belly nosing and aggression than comparable indoor-reared piglets. The objective of this study was to investigate how these differences in post-weaning behaviour relate to the piglets’ pre-weaning behaviour in the two rearing environments. The study was carried out at a commercial pig unit, where piglets of the same genotype are born into conventional indoor or outdoor farrowing systems. In the intensive system, sows were singly housed prior to farrowing in crates and their piglets received a solid ‘creep’ food prior to weaning. On the outdoor system, sows were allowed to build straw nests in arks for farrowing and both sow and piglets had access to pasture. Indoor and outdoor piglets were weaned at 24 (±3) days of age and mixed in straw-yard housing with access to a solid food. Prior to weaning, teat-directed activity was more common in indoor piglets than outdoor piglets. Outdoor piglets performed more rooting, standing and locomotion and were seen chewing the sows’ roll-nuts. Following weaning, outdoor-reared piglets performed more feeding and rooting, and less fighting than indoor-reared piglets. This study supports previous findings that undesirable activities such as fighting are less common in piglets weaned from outdoor systems, even when mixed with indoor piglets. In addition, outdoor-reared piglets were more likely to exploit solid food even though they did not have access to creep food prior to weaning.

The aim of this study was to investigate the effects of a 30-day increase in age of pigs slaughtered at 110 kg body weight (BW) on carcass and m. longissimus dorsi (LD) and m. biceps femoris (BF) traits, and meat sensory quality. A total of 60 pigs from two genotypes: synthetic line ✕ (Large White ✕ Landrace) (SL) and Duroc ✕ (Large White ✕ Landrace) (D) were used, each genotype containing five groups of six littermates (three castrated males and three females). At the average BW of 30 kg, littermates of the same sex were allocated to three groups. Pigs of group AL were offered ad libitum a standard growing-finishing diet (13·6 MJ/kg digestible energy, 9·5 g/kg of lysine) from 30 up to 110 kg BW. The R1 pigs received the same diet at 0·75 of the ad libitum intake of their AL littermates. The R2 pigs were submitted to both energy and protein restrictions in order to get the same growth rate as the R1 pigs and the same body composition as the AL pigs. Results were similar in both genotypes. In agreement with the protocol, age at slaughter was increased by 30 days in R1 and R2, and AL and R2 pigs had comparable carcass composition. Compared with AL, average daily gain was decreased in R1 and R2 pigs, and food efficiency was decreased in R2, but remained unaffected in R1 pigs. Intramuscular fat (IMF) concentration was decreased in the R1 pigs, especially in BF (15·5 v. 19·7 mg/g), while it was increased in the LD of the R2 pigs, particularly in the D animals (24·2 v. 17·4 mg/g), compared with AL pigs. Meat quality parameters (rate and extent of pH fall, reflectance and drip loss) were similar in the three feeding regimens. The taste panel did not find any significant difference between feeding regimens for tenderness, juiciness, flavour, flour sensation after mastication and mouth coating of the meat, despite the differences reported in IMF concentration. This suggests that, for the genotypes used in this experiment, an increase of 30 days in the age at slaughter greatly influences the carcass and/or the muscle chemical composition, depending on the feeding strategy applied to reduce the growth rate but does not strongly modify the meat eating quality.

The effects of xylanase and antibiotic addition to the diet, and the use of HCl-insoluble ash as a marker, on ileal and faecal apparent digestibilities of nutrients were studied with 12 growing pigs fitted with post-valvular T-caecum cannulae (PVTC). The results showed that the apparent ileal digestibility of non-starch polysaccharide (NSP) was high, (over 0·30). Xylanase, or antibiotics (Avoparcin) or xylanase plus antibiotics supplementation of the wheat middling-based diets did not significantly (P > 0·05) increase the ileal and faecal apparent digestibilities of NSP, neutral-detergent fibre (NDF), dry matter, crude protein, energy or amino acids. There were no significant (P > 0·05) differences between the HCl-insoluble ash and Cr2O3 recoveries at the ileal or at the faecal levels: proportionately, 0·864 and 0·911 for the ileal and faecal recoveries of HCl-insoluble ash, and 0·857 and 0. 915 for the ileal and faecal recoveries of Cr2O3, respectively.

Although veal production is a highly standardized system, there still remains considerable variability in productivity between units. This variability might be due to the farmers working on these units, through differences in stockmanship, work attitudes or behaviour, which in turn may affect animals’ fear responses, productivity and health. A survey was conducted on 50 commercial farms affiliated to the same veal company. All units had calves housed in individual crates, a similar number of crates, and the same diets and management advice. Data were collected on: building and general farm characteristics, farmers’ backgrounds and their attitudes towards their work and calves, farmers’ behaviour with the calves, calves’ reactivity to people, and disease level of the calves. Productivity results (growth rates, food efficiency and mortality) were used to classify veal units as ‘high producing’ (no. = 24) v. ‘moderate producing’ (no. = 26). Calves were less reactive to people in units where the farmer behaved sympathetically and where there were several stockpersons working. The disease level was lower in units where the farmer had a positive attitude towards the sensitivity of the calves to contact and towards the importance of cleaning. Productivity of the veal unit was associated with the health of the calves but not with their reactivity to people.

It is suggested that the farmer can have an influence on the success of the veal unit mainly through his/her ability to control the health of the calves and that a positive attitude towards animals and towards work (specifically cleaning actions) can improve the accuracy of surveillance and care of the animals. Moreover, through his/her behaviour with the calves and his/her ability to control their health, the farmer can play an important rôle in assuring calves’ welfare.

Sixty-four Azawak male weaned calves were allotted to eight treatments (T) in two trials to study the effect of timing (day or day-and-night) and duration of grazing on diet selection, faecal output, eating time, forage intake and weight changes. Grazing time during the day was 6 h for T 1, 2 and 3; 9 h for T 4, 5 and 6; and 12 h for T 7 and 8. Night grazing time was 0 h for T 1, 4 and 7; 3 h for T 2, 5 and 8; and 6 h for T 3 and 6. The trials were conducted from July 1995 to May 1996 covering the wet (WS), early dry (EDS) and late dry (LDS) seasons. Eight oesophageally fistulated steers were used in a cross-over design to sample the diet selected by day-grazers (D1) and by day-and-night-grazers during the day (D2) and at night (N2). Forage intake was determined from individual data on faecal output from all the calves and means of in vitro organic matter digestibility of extrusa of the fistulated steers. Water intake and eating time were measured in LDS. In WS there were no differences (P > 0·05) in the quality of the diet (extrusa) selected for D1, D2 and N2. In LDS, crude protein content for D1 was lower than for D2 (73 v . 79 (s.e. 2) g/kg dry matter, P < 0·05). In all seasons, faecal output and forage intake increased with total duration of grazing. Total time spent eating increased linearly with increasing total time allowed for grazing. These results suggest that allowing additional grazing time during the night leads to increased forage intake and consequently provides an opportunity for better animal production, especially in the dry season.

The aim of this experiment was to quantify the relationship between autumn grass supply and concentrate supplementation level on grass intake and animal performance. One hundred and ten continental steers (567 kg) were assigned to 10 treatments. The experimental design was a three grass allowances (6, 12 and 18 kg dry matter (DM) per head daily) by three concentrate levels: (0, 2·5 and 5 kg per head daily) factorial with a positive control group offered concentrates ad libitum and no grass. Grass allowance was offered daily and concentrates were given individually. The experiment began on 22 August and all animals were slaughtered after a mean experimental period of 95 days. Grass intake was calculated using the n-alkane technique and diet digestibility using ytterbium acetate as an indigestible marker. There was an interaction (P < 0·05) between grass allowance and concentrate level for grass intake. At the low grass allowance there was no effect of offering animals supplementary concentrates on grass intake, at the medium and high grass allowances, supplementary concentrates reduced grass intake by 0·43 and 0·81 kg DM respectively per kg DM concentrate offered. Increasing grass allowance increased (P < 0·001) complete diet organic matter (OM) digestibility at all concentrate levels and supplementary concentrates increased (P < 0·001) complete diet OM digestibility only at the low grass allowance. Both offering animals supplementary concentrates (P < 0·001) and increasing daily grass allowance (P < 0·001) increased their carcass growth rate. Relative to the animals offered the low grass allowance and no concentrate, supplementing with concentrate increased carcass growth by 116 g/kg concentrate DM eaten whereas increasing the grass allowance, increased carcass growth by 38 g/kg DM grass eaten. As a strategy for increasing the performance of cattle grazing autumn grass, offering supplementary concentrates offers more scope than altering grass allowance.

The objective of this study was to determine the effects on animal performance and rumen digestion characteristics of supplementing cattle grazing autumn grass offered at two levels of allowance, with concentrates formulated from different carbohydrate sources. Seventy-two steers (494 (s.e. 38·4) kg) were assigned to one of six treatments which were arranged in a two grass allowances (5·5 or 11 kg grass dry matter (DM) per head per day) by three concentrate types (starch, starch + fibre or fibre-based diets) factorial design. The experiment commenced on 22 August and had a mean duration of 84 days. Concentrates were formulated to have similar metabolizable energy and crude protein and animals were offered 5 kg per head daily. Grass allowances were offered daily and concentrates were offered individually. Six rumen fistulated steers were used concurrently in a Latin square design to determine the effect of the diets on rumen digestion characteristics. Grass and concentrates degradabilities were measured using the nylon bag technique. The concentrate DM was degraded at 0·189, 0·102 and 0·094 per h for the starch, starch + fibre and fibre-based diets, respectively. Concentrate carbohydrate source and grass allowance did not affect (P > 0·05) degradation rate of grass DM or nitrogen in the rumen, rumen fluid pH, rumen fluid concentration of volatile fatty acids, total lactic acid or ammonia concentration or plasma concentration of glucose, urea or beta-hydroxybutyrate. Animals offered the low grass allowance had larger (P < 0·05) diurnal variation in the rumen fluid acetate: propionate ratio than those offered the high grass allowance. Increasing grass allowance increased (P < 0·01) carcass gain whereas concentrate type had no effect. There was no interaction between concentrate carbohydrate source and grass allowance on any of the production variables measured. It is concluded that the rumen environment in cattle grazing autumn grass buffered the effects of concentrate carbohydrate degradability such that similar productivity was achieved with each concentrate.

Pregnant ewes were offered 0·80, 1·0 or 1·25 of estimated protein requirement, groups P80, P100 and P125, respectively and trickle infected with Teladorsagia circumcincta (average of 10000 larvae per day) and Trichostrongylus colubriformis (average of 7000 larvae per day) for 42 days prior to parturition. Eleven days after lambing half (group TC) received a single challenge infection of 25000 T. circumcincta and 17500 T. colubriformis larvae and the remainder (TO) no further larval challenge. Worm burdens were determined 21 days post partum.

Worm burdens were inversely related to dietary protein concentration. Mature worms (L5) of T. circumcincta recovered were (log10 (count + 1)) 4·002, 3·806 and 3·444 in TO sheep and 3·812, 3·633 and 3·113 in TC sheep from P80, P100 and P125 groups, respectively. The corresponding burdens of T. colubriformis were 2·665, 2·893 and 2·029 for TO and 3·985, 2·363 and 1·188 for TC sheep. The numbers of L4 larvae recovered from TC sheep were (log10 (count + 1)) 3·532, 3·288 and 3·127 for T. circumcincta and 3·080, 2·180 and 0·949 for T. colubriformis on P80, P100 and P125 diets, respectively. There was no evidence of inhibition of larval development or egg laying with either worm species suggesting that the major effect of protein supply in enhancing resistance was operating at the larval establishment stage. There was evidence that the post-partum challenge infection affected the fecundity and survival of the established adult worm population of T. circumcincta but not of T. colubriformis.

During each of four periods commencing either 4 weeks before, at, and at 6 and at 12 weeks after parturition four groups of reproductive sheep and one group of non-reproductive sheep (no. = 6 in all cases) were brought indoors with their lambs from pasture. One group of reproductive sheep (PA) was slaughtered to determine worm burdens carried at pasture. At the same time non-reproductive sheep (B) and a group of reproductive sheep (PB) were treated with anthelmintic (day –7) and on day 0 given 20 000 larvae of T. circumcincta and slaughtered on day 21 for the measurement of worm burdens. The remaining two groups of reproductive sheep were maintained indoors: one group (PC) was given 4000 larvae of T. circumcincta per day for 30 days and the final group (PD) uninfected. Both groups were treated with anthelmintic after 50 days and on day 57 given 20 000 larvae of T. circumcincta and slaughtered on day 78 for worm counts. Production data were obtained for sheep in groups PC and PD.

Chronic infection of ewes (PC) was associated with a 0·15 reduction in growth rates of their lambs and an increase in wool tenderness (0·3, P < 0·01). Worm burdens and eggs per g in reproductive sheep outdoors were highest during mid to late lactation which was confirmed by the pattern of change in resistance to challenge infection on removal from pasture. This contrasted with the situation indoors where resistance was least around parturition but was restored within 3 weeks of parturition and was especially evident in the group exposed to larvae during lactation (group PC).

It is argued that the prolonged period of susceptibility of the sheep at pasture could have a nutritional basis, reflecting their much greater body-weight loss during early lactation than in the sheep indoors. The implications of the findings for the management of sheep flocks with reduced chemical inputs are discussed.

The aim of the present investigation was, to examine whether outdoor wintering of lambing ewes is a successful and animal friendly production system. The welfare and growth performance of winterborn lambs in outdoor husbandry were assessed in two winter periods (1995/96, 1996/97) when a total of 353 lambs were born into three different husbandry systems. System 1 consisted of 75 lambs from 26 (winter 1) and 29 (winter 2) ewes and was wintered outdoors with access to a lambing shelter with a straw bedded floor. System 2 included 120 lambs from 52 (winter 1) and 54 (winter 2) ewes which were born in an uninsulated barn with access to an outdoor yard. System 3 was kept in an uninsulated barn with no access to the outside and consisted of 158 lambs from 52 (winter 1) and 54 (winter 2) ewes. The lambs were of five different genetic origins which were equally distributed over the three husbandry systems. The genetic groups included purebreds from the hardy ‘Rhönschaf’ (RHO) and from the ‘German Blackface’ (GBF) mutton breed and the reciprocal crosses of these breeds (GBF ✕ RHO, RHO ✕ GBF). The fifth group were crossbreds between rams of the small-framed French mutton breed ‘Charmoise’ (CHA) and Rhönschaf-ewes (CHA ✕ RHO). The time period between parturition and first standing (‘time to stand’) and the time period from birth to first sucking (‘time to suck’) were considered as vigour traits. Vigour was visually assessed and scored. The rectal temperature was measured 3 h post partum. Live-weight gains were estimated from birth to 25 and 42 days of life. No differences between the different husbandry systems were observed in the measured traits. Outdoor-born lambs showed the same vigour and were able to maintain homeothermy as well as those born indoors. Ewes sought the shelter prior to lambing which might have favoured the early vigour of lambs and thus, their ability to maintain homeothermy. The visually assessed vigour score was in good accordance with the vigour traits time to stand and time to suck. The breed of the ewe had a significant effect on lamb vigour, lambs from hardy RHO ewes showing a better vigour than lambs from GBF ewes. Hybrid vigour estimates of time to stand and time to suck were 0·17 and 0·20, respectively, but were not statistically significant.

Crossbred lambs between GBF and CHA mutton rams and hardy RHO ewes had a good vitality and growth performance. Outdoor wintering with a lambing shelter did not adversely influence survival of newborn lambs or their subsequent growth performance.

Ingestion of sewage sludge with soil, together with herbage containing elevated concentrations of potentially toxic elements (PTEs) might pose a risk to the human food chain through the accumulation of PTEs in edible tissues of livestock grazed on pastures which have received repeated doses of sludge. The accumulation of PTEs in tissues of animals grazed on a permanent pasture which had received repeated applications of sewage sludge between 1981 and 1994 was studied over two consecutive grazing seasons by monthly serial slaughter. Blocks of six weaned lambs were allocated at random at the start of the grazing seasons to slaughter date. Blocks of lambs were also allocated at random to an adjacent untreated pasture and to initial slaughter groups. Animals grazed continuously for two periods of 181 days and 152 days in 1994 (experiment 1) and 1995 (experiment 2), respectively. An application of sewage sludge was made to the treated site between the two experiments. The concentration of cadmium (Cd) in soil samples taken to 25 cm depth from the treated site was close to the United Kingdom statutory limit of 3 mg Cd per kg dry matter (DM) and 1·67 times the limit at the soil surface. Concentrations of other PTEs in soil were below statutory limis. The concentrations of PTEs in herbage at the treated site increased as each grazing period advanced (P < 0·05). Mean concentrations of Cd, lead (Pb), copper (Cu) and zinc (Zn) were higher (P < 0·05) in both experiments for herbage at the treated site than at the untreated site. No differences were observed in the concentrations of PTEs in muscle tissue between lambs grazed on treated or untreated pastures. The concentration of Cd in kidneys of lambs grazed on the treated pasture increased as the grazing seasons progressed from 0·19 to 0·36 mg/kg DM (P < 0·01) in experiment 1 and from 0·03 to 2·57 mg/kg DM in experiment 2 (P < 0·001). There was no measurable accumulation of Pb into kidney in either experiment. Concentrations of Cu in kidney remained similar during experiment 1 but increased during experiment 2 in lambs grazed on the treated pasture only (P < 0·05). Similar trends to those for kidney were observed for Cd in liver in both experiments. The concentrations of Pb increased in liver for lambs grazed on the treated site in experiment 1 (P < 0·01) but not in experiment 2. The concentrations of Cu in lambs grazed on the treated pasture in liver decreased (P < 0·01) in experiment 1 from 139 to 28 mg Cu per kg DM. Liver concentrations of Cu in experiment 2 increased (P < 0·01) from 63·5 to 197 mg Cu per kg DM, possibly reflecting the application of sludge to the experimental site between the two experiments. The results indicated that soil and herbage concentrations of PTEs were elevated following repeated applications of sewage sludge to grassland. The accumulation of PTEs in edible body tissues was generally low, with the greatest being of Cd and Cu in the second experiment, possibly reflecting recent application of sludge.