An animal model and an approximative method for calculating repeatabilities of estimated breeding values are used in Finnish dairy cow evaluation. Changes in estimated breeding values over time as daughters accumulate were studied. Special emphasis was given to the accuracy and potential bias in the pedigree indices of young sires. The data set used was the same as in the national evaluation and the traits investigated were protein yield and somatic cell count. The average repeatability in evaluation of bulls without daughters was 0·37. The empirical repeatability defined as a squared correlation between the pedigree index and the final sire proof was only 0·15. The reduction in the repeatability was attributed to the selection on pedigree index. The upward bias observed in pedigree indices was 5 kg (approx. 0·3 of genetic standard deviation). The bias was caused by the overestimation of bull dams' breeding value. Also the proofs of bull sires increased after the second crop of daughters. The correlation between the evaluations of the same sire calculated from two separate equal size daughter groups was 0·91 when the bull had 10 to 50 daughters and 0·87 with over 100 daughters. This illustrates how the relative weight of the pedigree decreases while more progeny information is accumulated in the evaluation.

In each of two experiments, 36 3 to 5-day-old dairy calves (male and female), were allotted to one of three groups: warm housing, milk feeding in teat-buckets twice a day (group 1); warm housing and computer-controlled milk feeding (group 2); and cold housing and computer-controlled milk feeding (group 3). The experiments were conducted from September until February. The daily gain in the first 4 weeks was lower for the calves in group 3 in both experiments and for calves in group 2 in experiment 2 because of lower food intake in this period. This was compensated for by an increased gain later. In spite of the different method of milk feeding, the activity rhythm was nearly equal among groups, but at week 6 and 10 the calves in group 1 spent more time with the head over the feeding table than the calves in the two other groups. The number of unrewarded visits per calf to the milk feeding station decreased from over 30 at week 4 to around 20 shortly before weaning. The frequency of sucking/licking pen-mates was almost negligible in all groups. In order to reduce the heat loss, the frequency of calves lying with body contact clearly increased by decreasing ambient temperature in cold housing.

This experiment examined the effects of sustained levels of undernutrition applied to grazing Brahman heifers on subsequent lifetime reproductive performance. Weaned heifers were raised to a target weight of 270 kg at three different stocking rates to obtain contrasting weight gains (0·097 kglday, L = low; 0·215 kg/day, M = medium; 0·259 kg/day, H = high). They were then subjected to common grazing in a low-quality Brachiaria humidicola pasture, where mean weight changes ranged between -0.100 and +0·300 kg/day depending upon season and physiological condition. Differences in age at first calving between L and the other treatments (200 days) were maintained in subsequent calvings. Calf weaning weights were higher in L and M than in H. The mean weight of calf weaned per cow per year was higher in M than in either L of H. Cow weight at conception increased with parity, and was higher in L than in the other treatments. Similar trends were observed for the dam's weight preand post calving, and at weaning. This trend was associated with higher weight loss during lactation in I..

We conclude that in tropical grazing systems that allow only low growth rates, differences established early in reproductive life may become perpetuated for the lifetime of the animal. Management implications in the context of extensive tropical grazing systems are discussed.

A study urns conducted to examine herd structures and cattle disposal patterns of Bunaji herds kept under traditional management at four locations in the subhumid zone of Nigeria. Sale for meat was the single most important disposal reason, accounting for proportionately 0·55 of all disposals. Mean age of cattle sold for meat was 8 years but the age range was wide: animals as old as 17·4 years were involved in such sales. Male animals were sold at a younger age (6·2 years) than females (9·3 years). Sale of calves was an important exit avenue for rural herds with less access to milk market. Calves were sold at a mean age of 1·1 years and male calves accounted for a larger proportion (0·62) of such sales. Animal sales were highest in the early dry season and lowest in the early wet season. The predominantly arable farming location, Ganawuri, had the highest frequency of animal sales and lowest frequency of exits for ‘social functions’ (exchanges, transfers and gifts). Animal transfers, gifts and exchanges were important disposal routes in the traditionally pastoral communities, especially in locations with good grazing (e.g. Abet). Exits involving exchanges, transfers and gifts were more frequent during the dry season and least frequent in the wet season. An average herd had 77 head of cattle composed proportionately of 0·54 adult females (>3 years), 0·13 adult males (>3 years), 0·08 young bulls (1 to 3 years), 0·13 heifers (1 to 3 years) and 0·11 calves (0 to 1 year). There was a tendency toward smaller herds in later years (97 in 1980 to 51 in 1989) and a decrease in the ratio of adult females to males (from 6:1 in 1980 to 3:1 in 1989). Substantial between-location differences existed in herd size ami herd structure, ranging from the ‘beef orientation’ of the arable Ganawuri with a high proportion of immatures and calves, to the pastoral situation in Abet and Kurmin Biri with high proportion of adult animals. The proportions of adults were lowest in the early dry season, reflecting seasonal pattern in disposal and calving. The pattern in disposal reasons over time indicated a decrease in the proportion of animals exiting herds through exchanges, transfers and gifts and signified a possible shift from tradition, probably a response to population pressures and emergence of cash economies.

An on-farm study was conducted over a 12-year period (1979 through 1990) at four locations in the subhumid zone of Nigeria to estimate levels of performance of Bunaji cattle and to examine factors affecting productivity in these production systems. Average weight at birth, at 9 months and at 12 months were 19·6 kg, 76·2 kg and 93·1 kg, respectively. Average daily gain between birth and 9 months was 211 g/day. The corresponding figure between 9 months and 12 months was 176 g/day. Cumulative calf mortality at 9 months and at 12 months were proportionately 0·14 and 0·15, respectively. Mean age at first calving was 62·5 months while interval between consecutive calvings averaged 22·5 months. Mean daily milk offtake was 510 ml. Mean length of offtake period varied substantially between locations ranging from 339 days in Kurmin Biri to 425 days in Madauchi. Lactation milk offtake was estimated at between 200 and 260 I. Peri-urban Madauchi had the highest daily milk offtake, the longest milk extraction period but the poorest calf growth and survival rates. Locations with low milk offtake had superior calf performance both in terms of growth and survival. Calves born in late wet and early dry seasons had superior growth and survival rates. Most calvings occurred in the dry season mainly because of the effect of season on conception rates. There was a tendency towards improved productivity on a per-animal basis over the years. This ivas so for age at first calving, calving interval, calf survival and milk offtake. Improved reproductive performance provided opportunity for higher offtakes. However, growth between 9 months and 12 months and weight at 12 months declined during the study period.

Fasciolosis is a serious economic disease of cattle and sheep with a worldwide distribution. In the annual control of the disease, it is vital that the issue of specific veterinary advice on the strategic use of control measures should be based on precise estimates of the levels of risk of the occurrence of the disease. This paper describes the construction of a mathematical model to forecast the level of risk of the disease in cattle in any year. The model has been developed in Northern Ireland using a computerized information database retrieval system for abattoir condemnation data. The information recorded by the system details the specific cause and location of all condemnations in cattle, sheep and pigs for all abattoirs in Northern Ireland. Analysis of a subset of these data (1976 to 1991) for cattle resulted in a univariate time series model for the recorded prevalence of condemnations due to fasciolosis in cattle livers. The overall mathematical forecasting model was constructed by regressing the residual terms of the univariate time series model with the corresponding time series of all the key meteorological variables. The best model (R2 =0·8) was obtained using the mean air temperature for the period fune to August inclusive. The model could be adopted for use in any region of the world where relevant abattoir condemnation and meteorological data are available.

Two experiments, experiment 1 with six steers in a 3 × 3 Latin-square design and experiment 2 with four wether sheep in a cross-over design, were conducted to study the effect of species and ammonia treatment on intake and utilization of the energy of untreated wheat straw. Treatments were: (1) untreated wheat straw offered ad libitum on top of a basal diet (B) consisting of hay (0·25) and grass pellets (0·75) (UWS), (2) ammoniated wheat straw offered ad libitum plus B (AWS) and (3) ammoniated wheat straw offered at a restricted level plus B (AWS-). B was offered as a maintenance diet for both species and AWS- was only studied in steers. Voluntary intake of AWS zvas higher than that of UWS. No significant differences emerged between whole rations UWS and AWS with regard to energy digestion (ED), energy metabolizability (ρ = metabolizable energy (ME) I gross energy (GE)) and losses of digestible energy (DE) in urine and methane (average 187 J/KJ DE), but the efficiency of utilization of ME for growth (kg) was significantly higher for AWS than for UWS. ED and ρ of the straw part of the ration was significantly higher for AWS than for UWS. AWS- and AWS did not differ significantly with regard to ED, ρ and DE losses in methane and urine. Steers had a higher intake per kg0·75 per day than wether sheep. Across species, digestible energy intake (DEI) of the whole ad libitum fed diets was related to live weight (M)0·946 (s.e. of exponent 0·0152). ED and ρ of the straw part of the rations did not differ significantly between species, but steers had a significantly higher ED and ρ of β than wether sheep. Steers excreted a significantly lower proportion of DE in urine and a significantly higher proportion of DE in methane than did wethers. Total energy losses in urine and methane, however, did not differ between species.

Twelve Suffolk-Finn Dorset lambs were reared from 25 to 40 or 25 to 55 kg body weight on either pelleted dried grass or a ration of pelleted grass plus barley (ratio 1:1) in a comparative slaughter experiment designed to determine the amounts of total nitrogen and individual amino acids accreted in different body components during growth. Nitrogen (N) balance measurements were determined frequently during this growth phase and accumulated N retentions were compared with the total N accretion determined by comparative slaughter. Total N and individual amino acids accumulated in carcass, wool, skin, offal and blood, head and feet, gastro-intestinal tract and liver were linearly related to body weight in all cases other than for cysteine in carcass. At 25 kg live weight, proportionately 0·52 of total body N was in carcass components, 0·115 in wool, 0·08 in skin, 0·10 in offal and blood, 0·095 in head and feet, 0·06 in the gastro-intestinal tract and 0·02 in liver. However as the animals grew from 25 to 55 kg, 0·256 of the total N accretion was in wool, which was rich in cysteine (98 g/kg total amino acid). Carcass accretion represented only 0·449 of total body N accretion. The N balance technique overestimated net protein accretion by 0·24 (s.e. 0·036).

Twenty-five male goats weighing 16 (s.e. 1-5) kg and aged 15 months were used to measure the dry matter (DM) intake of five browse species namely Acacia albida, Tamarindus indica, Etanda africana, Anogeissus leiocarpus and Sterculia setigera in a growth trial lasting 16 weeks. This was followed by a digestion trial with five goats in a 5 × 5 Latin square with 10 days adaptation and a 5-day measurement period. The degradation characteristics of the browse were measured by incubating samples in nylon bags for 6, 24, 48 and 96 h in the rumens of three sheep fitted with rumen cannulae and given hay plus grass nuts. The exponential model P = a +b(l — ect) was fitted to the data. Rumen fluid from the sheep was also used as an inoculum to incubate the samples in vitro for 3, 6,12, 24, 48, 72 and 96 h. Nylon bag degradability results were compared with in vivo results and in vitro gas production. The mean DM intakes, apparent digestible DM intakes and growth rates were 0·60, 0·62, 0·55, 0·53 and 0·65 kg/day, 0·43, 0·43, 0·35, 0·34 and 0·49 kg/day and 55, 60, 49, 42 and 62 glday for A. albida, T. indica, E. africana, A. leiocarpus and S. setigera respectively. Using the degradation characteristics A, B and c in a multiple regression analysis, the correlation coefficients with DM intake, apparent DM digestibility, apparent digestible DM intake and growth rate were 0·99, 0·88, 0·92 and 0·99 respectively. The inclusion of a lag phase (L) instead of A in the regression analysis improved the prediction of apparent DM digestibility and apparent digestible DM intake. The correlation coefficients between DM loss in nylon bags and in vitro gas production at 6, 24 and 48 h incubation were 0·84, 0·83 and 0·90 respectively. The results indicate that it may be possible to predict DM and apparent digestible DM intakes of browse by goats from the rumen degradation characteristics.

The effect of grazing clover on ewes and lambs was studied using nitrogen-fertilized grass (G) and grass/white clover pastures (GC) containing proportionately 0·18 clover. Carcasses of lambs grazed on GC were significantly heavier than carcasses of lambs grazed on G pastures. An interaction with weaning occurred. Carcasses from lambs grazed on GC for 53 days post weaning were 2·3 kg heavier (F < 0·01) but lambs slaughtered at weaning had similar carcass weights. Diet had no effect on relative joint components of carcasses. The effect of clover in the diet on carcass weight was attributed to higher levels of protein retention.

Analysis of the fatty acid composition of intramuscular and subcutaneous and perirenal lipids indicated small but significant effects of diet. Lean tissue lipids of lambs grazing clover showed significant increases in C18:2 and reduced C20: 5 fatty acids. In tissue fats there were small increases in C14:0, C16:0 and C18:2 with reduced C18:1 content.

Twin suckled lambs grazing GC for 94 days from turn-out in early April showed increased live-weight gain over lambs on G of 336 v. 287 g/day (s.e.d. 84; P < 0.001). Post weaning live-weight gain of lambs was 173 and 221 g/day on G and GC respectively. Sward height was maintained at 5.18 and 5.24 (s.e.d. 0.075) cm on G and GC paddocks by adjusting ewe numbers. GC pastures carried proportionately 0.82 of the stock on G pastures but output of lamb was similar at 1289 and 1247 kg/ha for G and GC respectively.

Results showed that the production penalty of lower stocking rate associated with grass/clover v. grass fertilized with 190 kg nitrogen per ha was ameliorated by higher lamb live-weight gain and carcass weight without change in joint composition or nutritionally significant change in fatty acid composition of carcass tissues.

The performance of British Saanen, Boer × British Saanen and Anglo-Nubian kids from weaning to slaughter at 28, 33 or 38 kg live weight (LW) was examined in a 3 × 3 factorial experiment. Kids were reared on a concentrate and hay ration, after weaning at 8 weeks of age. Intakes were measured individually. At slaughter, carcasses and body fractions were weighed, left half-carcasses were dissected into muscle, fat and bone, and the carcass and non-carcass fractions were analysed chemically. There ivas no significant effect of breed type on mean daily intakes, but there was a significant breed-type effect on mean daily LW gains in the order British Saanen > Boer × British Saanen > Anglo-Nubian kids. Compared with the pure British Saanen kids, the Anglo-Nubian kids produced heavier carcasses yielding more muscle and less subcutaneous and intermuscular fat at each slaughter weight. By contrast, the Boer × British Saanen carcasses contained proportionately more fat, mainly intermuscular fat, than the British Saanen when slaughtered at 28 or 33 kg LW. When taken on to slaughter at 38 kg LW, the Boer × British Saanen kids showed little further increase in fat deposition at the internal and intermuscular sites compared with the British Saanens, resulting in carcasses with slightly more subcutaneous fat but lower overall carcass fat content.

The effects of melatonin implants, administered during anoestrus, on the time of onset of oestrus, conception rate and litter size in indigenous (Capra prisca) and crossbred dairy goats were studied on commercial farms in a hill region of northern Greece. In the 1st year, 192 indigenous and 86 crossbred does on one farm (farm 1) were each separated into treated (T) and control (C) groups. The T groups from each breed type were given implants of melatonin on 17 April and 6 May, respectively. Bucks were re-introduced to both T and C groups 5 weeks after implantation. Mean mating dates for indigenous goats were 6 July (s.e. 0·15) (T) v. 13 July (s.e. 0·24) (C). Corresponding dates for crossbreds were 31 July (s.e. 0·61) (T) v. 14 August (s.e. 0·87) (C). Treatment did not significantly affect conception rate. Mean kidding dates (from first service) were 6 December (s.e. 0·18) (T) v. 14 December (s.e. 0·28) (C) for indigenous and 31 December (s.e. 0·64) (T) v. 13 January (s.e. 0·82) (C) for crossbred goats. Litter size was higher in both T groups but the difference was not significant. In the 2nd year the indigenous flock on farm 1 was supplemented by two similar neighbouring farms. Farm 1 had both treated does and control does; farm 2 were all treated and farm 3 were untreated control does. In this year all bucks used on treated does were also implanted. All implants were given on 21 April. Mean mating dates were 21 June (s.e. 0·23) (1/T) v. 9 July (s.e. 0·36) (1/C), and 28 June (s.e. 0·09) (2/T) v. 19 July (s.e. 0·15) (3/C). Conception rate was high in all groups. Corresponding mean kidding dates were 22 November (1/T) v. 11 December (1/C) and 29 November (2/T) v. 22 December (3/C). Litter size was higher (F > 0·05) in T than in C groups.

An investigation was conducted to compare, the LH, prolactin and progesterone profiles of ewe lambs with ewes during oestrus and early pregnancy. Peak LH concentration was significantly lower (P < 0·05) and duration of release tended to be shorter during oestrus in ewe lambs. Furthermore, this smaller LH peak tended to be associated with a lower ovulation rate. LH pulse rate, amplitude and concentration were similar in both groups during day 13 of pregnancy. However, LH concentration was higher in ewe lambs compared with ewes on day 28 of pregnancy. Peak prolactin concentration was lower during oestrus in ewe lambs (P < 0·05) but there was no difference between the two groups during early pregnancy. Plasma progesterone concentrations were similar in both groups until day 13 of pregnancy. Thereafter, mean progesterone concentration was lower, from day 14 to 30, in the ewe lambs (P < 0·05). These results indicate that in ewe lambs and ewes maintained under identical conditions plasma hormone profiles differ during oestrus and early pregnancy. Moreover, these differences probably contribute towards the lower reproductive performance of ewe lambs.

Estimations of purine derivatives excretion and urinary-nitrogen loss were used to test the response of rumen fermentation to supplementation of straw with different sources of carbohydrate. Two groups of Rasa Aragonesa ewes (44 (s.e. 0·75) kg live weight were given ad libitum basal diets of either ammonia-treated (ATS) or urea-supplemented (USS) barley straw, with 12 animals per basal diet group. Three supplements, barley grain, sugar-beet pulp or grass hay, respectively, were given to each basal diet group, giving a total of six dietary treatments with four animals per treatment group. Four levels of supplementation were studied (150, 300, 450 and 600 g air dry matter per day), one in each of four experimental periods. Each 45-day experimental period comprised 38 days of adjustment followed by a 7-day measurement period. Digestible organic matter (DOM) intake was higher in animals receiving ATS than in animals receiving USS (504 v. 474 (s.e. 21·1) g/day, P < 0·005) and higher in animals receiving barley grain and sugar-beet pulp than in those receiving grass hay (512 and 496 v. 370 (s.e. 25·9) g/day, P < 0·005). DOM intake also increased with the level of supplementation and this increase was greater with barley grain (504 to 634 and 314 to 554 g/day for ATS and USS) and sugar-beet pulp (440 to 582 and 315 to 522 g/day) than with grass hay (430 to 407 and 267 to 370 for ATS and USS). Urinary excretions of hypoxanthine, xanthine and uric acid were not affected by the experimental treatment whereas allantoin excretion (y, mmol) increased in response to DOM intake (x, kg) (y = 13·72 × − 0·26; r = 0·79; P < 0·001; no. = 96). The response in allantoin excretion was mainly explained by the increase in DOM intake. However when data were expressed per unit of DOM intake significant differences were still evident. Allantoin/DOM intake (mmol·kg) ratio and calculated microbial nitrogen (g·kg DOM intake) supply were lower with USS diets and sugar-beet pulp supplemented diets (P< 0·05) and increased significantly with level of supplementation (P < 0·001).

Housing soivs in large groups is increasing in popularity but some group-housing systems may compromise subsequent reproductive performance. An experiment was designed to test this hypothesis using multiparous sows weaned at 21 ±2 days. Two treatments were studied: a stable group of 12 sows and a dynamic group of 18 sows. Both treatments had similar space allowances in the lying area (1·24 m2 per sow). Sows were allocated to treatment within 1 week of service and remained on treatment until after day 40 of pregnancy. Each stable treatment group remained unchanged, whereas sows were replaced weekly in the dynamic treatment. Sows were fed using a single electronic feeder for each pen. All sows were treated similarly for the rest of pregnancy. Eighty and 120 sows from the stable and dynamic treatments respectively completed pregnancy. Five second parity sows from the dynamic treatment were removed having suffered from aggression. The farrowing rate was 0·78 and 0·85 for stable and dynamic treatment sows respectively. The stable treatment sows had larger litters and a higher proportion of litters having 10 or more total piglets born (P < 0·01). The stable treatment showed a significantly heavier (P < 0·05) litter weight for total pigs born (16·9 v. 14.6 (s.e.d. 0·57) kg per litter). The parities were uneven so the data must be treated with caution. However, the results indicate that the present advice, that soivs should be housed in stable groups for the first 4 weeks of pregnancy, should remain unchanged.

Most livestock are transported at least once during their lifetime. Environmental conditions inside the transporter are critically dependent on many factors which can be controlled by well designed and carefully operated ventilation systems. Heat, moisture and carbon dioxide production of cattle, pigs and sheep are fitted to simple models as bases for ventilation design criteria. These assume that the animals are not well fed immediately before or during transport and that maintenance metabolic heat production applies. Interactions between temperature and humidity during transport are important at temperatures above 24°C.

Ventilation slots along the sides of transporters can be occluded by the bodies of the stock themselves. Relevant dimensions of pigs, cattle and sheep related to body weight are provided as additional design parameters. Stocking density interacts critically with other aspects of transport and normally recommended values are shown to be inconsistent. Space requirements should be based on species and body weight, provided that the ventilation capacity is satisfactory.

Proposed European regulations on the transport of livestock provide general guidelines for the provision of ventilation, but no means of achieving these requirements. This paper draws together detailed criteria for establishing acceptable space, thermal, psychrometric and gaseous conditions on transporters for pigs, cattle and sheep. Application of these quantitative criteria will assist shippers and regulating authorities in providing more suitable environmental conditions than are frequently achieved at present.

Free amino acid (AA) levels in plasma, muscle and liver were measured in growing chickens given either high or low protein diets varying in quality. In experiment 1, they were force-fed once a day (09.00 h), for 4 days, at about 1·5 × M level, a nitrogen-free (NF) diet and then, on day 5, they were given either diet NF or isoenergetic (13·1 kj metabolizable energy (ME) per g dry matter (DM)) and isonitrogenous high protein diets (200 g crude protein (CP) per kg) based on casein (C), lupin (L), soya bean (SB), faba bean (FB), field pea (FP), vetch (V) or bitter vetch (B) as the sole source of protein. In experiment 2, chickens were force-fed twice a day (09.00 h and 18.00 h), for 3 days, at about 1·9 × M level, with four isoenergetic (13·1 k) ME per kg DM) and isonitrogenous low protein diets (120 g CP per kg) based on SB, FP, V or B as the sole source of protein. On days 5 (experiment 1) and 4 (experiment 2) samples of plasma, muscle and liver were taken for AA analysis over 3 to 4h after morning meal.

In general, within experiments, no significant differences in AA concentrations in plasma, muscle or liver among diets were found. However, there was a qualitative but not a quantitative agreement between the AA abundance in tissues and the AA rank of dietary protein. Moreover, when pooling data from experiments 1 and 2, significant regressions were found between the levels of threonine, aspartic acid, glutamic acid, glycine and proline in plasma, of lysine, alanine, glutamic acid, glycine and proline in muscle or that of proline in liver and the corresponding amounts ingested with the different diets. Under the conditions of these experiments, however, it was not possible to establish conclusively a direct relationship between the level of free amino acids in tissues and dietary protein quality.

Commencing on day 100 ± 10 of lactation, 10 Italian Friesian cows averaging 32·6 kg milk per day were injected biweekly with recombinant bovine somatotropin (BST), while 10 other cows averaging 33-4 kg milk per day were injected with a placebo. Cows were offered ad libitum a total mixed diet throughout the lactation. The experiment lasted 16 weeks; milk samples were taken before and 16, 62 and 91 days after the commencement of BST injection. The objective was to determine the impact of biweekly injections of BST on the synthesis and proportion of milk fatty acids, particularly on cis and trans isomers and on fatty acids with an odd number of carbon atoms (C15 and C17). A decrease in the proportion of shortchain (C4 to C14) fatty acids (P < 0·001) and an increase in the proportion of long-chain (C16 to C20) fatty acids (P < 0·001) were observed in the first period of the treatment. With regard to cis and trans isomers, a considerable increase of the cis isomers (P < 0·001), particularly C18.1cis9 (oleic acid) was observed, while differences in trans isomers were not statistically significant. Concentrations of C15 (pentadecanoic acid) were not affected but heptadecanoic acid (C17) concentration showed a considerable increase (P < 0·01) but only in the sample taken after 16 days.

The possibility of using dietary variety to enhance food intake of ruminants was investigated with 36 Hereford steers. For 21 days, 18 animals were given a monotonous diet of either hay or silage, while 18 others were given a varied diet of hay and silage offered in succession, at either 12- or 24-h intervals. Dietary variety did not affect total food intake (P > 0·05). However, when offered both foods at the end of the trial, animals which had been restricted to hay showed a proportional increase of 0·15 in their acceptance of silage (P < 0·05), whereas animals restricted to silage showed an increase of 0·49 in their acceptance of hay (P < 0·05)

A total of 1855 records were analysed using restricted maximum likelihood (REML) techniques to estimate heritabilities separately for males and females lambs on birth weight (BW), weaning weight (WW), 90-day weight (W90) and average daily gains birth to weaning (Cl) and weaning to 90 days (C2). An animal model including fixed effects of year × season, parity, litter size and rearing type; and random effects of direct genetic effect (h2D) and residual was applied. Estimates ofh2Dfor BWwere 048 (males) and 0·50 (females); for WW 0·35 (males) and 0·22 (females); for W90 0·21 (males) and 0·31 (females); for Cl 0·20 (males) and 0·25 (females); and for C2 0·18 (males) and 0·29 (females).