Active immunization against gonadotropin-releasing hormone (GnRH), commonly known as immunocastration, has been proposed as an alternative to traditional methods of castrating bulls. This study evaluated the effects of immunocastration on growth, behaviour and meat quality of post-pubertal bulls. Bulls were either vaccinated against GnRH (no. = 30, I) or left intact (no. = 30, B). A third treatment consisted of steers (no. = 20, S) that had been castrated pre-pubertally. The animals were run in eight single treatment groups (no. = 10 per group), three of each of В and I and two groups of S. Anti-GnRH antibodies developed and plasma testosterone concentrations declined in I following immunization. Aggressive behaviour of I declined to be lower (P < 0·5) than B and no different from S, 5 weeks after primary immunization. Seven weeks after immunocastration all animals were slaughtered. The hot carcass weight of I was between that of B and S but not significantly different from either. There were no effects of treatment on pHu or meat colour measurements. Taste panel assessment rated I higher than B, but lower than S for tenderness, juiciness and overall palatability. These results demonstrate that immunocastration of post-pubertal bulls 7 weeks before slaughter is a potential means of reducing problematic bull behaviour and improving meat quality although this is likely to be at the cost of reduced weight gain.

In two feeding experiments, an untreated silage which had received no additive was compared with silages which had received either formic acid (‘Add-F’) or a formalin and sulphuric acid mixture (‘Sylade’). The ‘Add-F’ was applied at the rate of 3·81/t and ‘Sylade’ at the rate of 3·1 1/t of fresh herbage harvested from a perennial ryegrass and white clover sward.

The silages were offered ad libitum to 30 British Friesian male calves (mean fasted live weight 97 kg) in Experiment 1 and to 27 steers (mean fasted live weight 320 kg) of mixed breed in Experiment 2. Concentrate was offered to the animals in Experiment 1 at the rate of 0·86 kg dry matter/head per day.

In each experiment the intakes of dry matter and digestible organic matter were higher from the additive-treated silages than from untreated silage.

In Experiment 1 the application of ‘Sylade’ increased significantly (P < 0·05) the mean daily unfasted live-weight gain (0·87 kg/day) over that for animals offered untreated silage (0·74 kg/day). In Experiment 2 the mean daily unfasted live-weight gains from ‘Sylade’-treated (0·70 kg/day) and ‘Add-F’-treated silage (0·78 kg/day) were significantly higher (P<0·01) than that from untreated silage (0·38 kg/day).

Data on Djallonke sheep collected from 1983 through 1992 on 29 participating farms of an open nucleus improvement programme and from the nucleus were analysed. Initial on-farm records on 14342 lambs and on-station records on 2551 ram lambs were edited down to 6605 for birth weight (BWT), 5857 for preselection (birth to 80 days) average daily gain (PSADG), 10417 for 80-day weight (WT80), 13054 for lamb survival at pre-selection, 1978 for 180 (WT180) and 849 for 365 (WT365) day weights. Year of birth, sire line, flock, month and season of birth had significant (at leastP < 0·05) effects on both on-farm and on-station weights and on lamb survival. Trait means were 2·2 (s.e. 0·02) kg for BWT, 69·6 (s.e. 1·26) g/day for PSADG, 9·1 (s.e. 0·05) kg for WT80, 19·7 (s.e. 0·24) kg for WT180 and 31·8 (s.e. 0·45) kg for WT365. Mean survival was 90 (s.e. 0·9) %. Single lambs were heavier at birth and at 80 days of age, grew faster to 80 days and were about 200 and 500 g heavier at 180 and 365 days respectively than multiple lambs. There was a large variation between flocks: flock means for WT80 varied from 6·4 to 12·0 kg (CV 0·21), with smaller flocks having generally the lowest means. Lambs born in the hot-rainy season had the heaviest birth and 80-day weights, whereas ram lambs born in the cool rainy and early hot-dry seasons had the heaviest 180- and 365-day weights. Lambs born during the cool months of July to October had the lowest survival rate. Multiplicative factors were found to be more appropriate for adjusting on-farm records for type of birth, management level, birth date, season of birth and ewe parity than additive adjustment factors.

Thirty-eight barley-fed entire and castrated male Friesian calves were used to examine the effects of different implanted anabolic agents on growth and carcass and tissue composition. Entire males were implanted with trenbolone acetate plus hexoestrol alone or following an earlier implantation of zeranol, or with zeranol alone. Control bulls (no implant) and steers treated with trenbolone, acetate plus hexoestrol were also studied. The anabolic agents tended to increase growth rate in bulls, and caused an increase in fat deposition. Treated steers had more abdominal fat than all bulls, but did not have more carcass fat. However, the carcasses contained less saleable meat and had a lower retail value because of lower lean-to-bone ratio. There were no significant differences between any of the groups in the proportions of lipid and water in the lean tissue. Transporting the bulls resulted in a high pH and a dark colour in m. tongissimus. The results suggest that anabolic agents have small biological effects which directly modify the quantitative and qualitative meat production characteristics of bulls.

The expected increase in the global demand for livestock products calls for insight in the scope to increase actual production levels across the world. This insight can be obtained by using theoretical concepts of production ecology. These concepts distinguish three production levels for livestock: potential (i.e. theoretical maximum) production, which is defined by genotype and climate only; feed-limited production, which is limited by feed quantity and quality; and actual production. The difference between the potential or limited production and the actual production is the yield gap. The objective of this paper, the first in a series of three, is to present a mechanistic, dynamic model simulating potential and feed-limited production for beef cattle, which can be used to assess yield gaps. A novelty of this model, named LiGAPS-Beef (Livestock simulator for Generic analysis of Animal Production Systems – Beef cattle), is the identification of the defining factors (genotype and climate) and limiting factors (feed quality and available feed quantity) for cattle growth by integrating sub-models on thermoregulation, feed intake and digestion, and energy and protein utilisation. Growth of beef cattle is simulated at the animal and herd level. The model is designed to be applicable to different beef production systems across the world. Main model inputs are breed-specific parameters, daily weather data, information about housing, and data on feed quality and quantity. Main model outputs are live weight gain, feed intake and feed efficiency (FE) at the animal and herd level. Here, the model is presented, and its use is illustrated for Charolais and Brahman × Shorthorn cattle in France and Australia. Potential and feed-limited production were assessed successfully, and we show that FE of herds is highest for breeds most adapted to the local climate conditions. LiGAPS-Beef also identified the factors that define and limit growth and production of cattle. Hence, we argue the model has scope to be used as a tool for the assessment and analysis of yield gaps in beef production systems.

The amylase (Am I) genotypes have been determined in sera from 834 cows comprising 562 Friesians, 77 Ayrshires, 106 Guernseys, 62 Jerseys and 27 crossbred cows. All of these cows had completed their third lactation and many were much older. There was a highly significant excess of heterozygotes at the Am I locus. This excess of heterozygotes was highest in high-yielding Friesian herds and there was a significant correlation between percentage heterozygotes and herd yield in the Friesians.

n-3 polyunsaturated fatty acids (n-3 PUFA) contribute to the normal growth and development of numerous organs in the piglet. The fatty acid composition of piglet tissues is linked to the fatty acid composition of sow milk and, consequently, to the composition of sow diet during the gestation and lactation period. In this study, we investigated the impact of different contents of extruded linseed in the sow diet on the fatty acid composition and desaturase gene expression of piglets. Sows received a diet containing either sunflower oil (low 18:3n-3 with 18:3n-3 representing 3% of total fatty acids) or a mixture of extruded linseed and sunflower oil (medium 18:3n-3 with 9% of 18:3n-3) or extruded linseed (high 18:3n-3 with 27% of 18:3n-3) during gestation and lactation. Fatty acid composition was evaluated on sow milk and on different piglet tissues at days 0, 7, 14, 21 and 28. The postnatal evolution of delta5 (D5D) and delta6 (D6D) desaturase mRNA expression was also measured in the liver of low 18:3n-3 and high 18:3n-3 piglets. The milk of high 18:3n-3 sows had higher proportions of n-3PUFA than that of low 18:3n-3 and medium 18:3n-3 sows. Piglets suckling the high 18:3n-3 sows had greater proportions of 18:3n-3, 20:5n-3, 22:5n-3 and 22:6n-3 in the liver, and of 22:5n-3 and 22:6n-3 in the brain than low 18:3n-3 and medium 18:3n-3 piglets. D5D and D6D mRNA expressions in piglet liver were not affected by the maternal diet at any age. In conclusion, extruded linseed in the sow diet modifies the n-3PUFA status of piglets during the postnatal period. However, a minimal content of 18:3n-3 in the sow diet is necessary to increase the n-3PUFA level in piglet liver and brain. Moreover, modifications in the n-3PUFA fatty acid composition of piglet tissue seem linked to the availability of 18:3n-3 in maternal milk and not to desaturase enzyme expression.

Immunocastration (ImC) has been proposed as an animal welfare-friendly alternative to reduce sexual and aggressive behavior and to increase carcass fat deposition with positive effects on meat quality. The β-adrenergic agonists (β-AA) are known as repartitioning agents that acts increasing lean tissue deposition. The combined use of these technologies can positively affect meat quality and increase retail cuts yield. Thus, this research was conducted to evaluate the combined effects of ImC and β-AA (zilpaterol hydrochloride (ZH) and ractopamine hydrochloride (RH)) on retail cuts, bones, and fat trim of feedlot finished Bos indicus (Nellore) cattle. No interaction was observed between sexual condition and diet for any trait. The ImC decreased cold carcass, hindquarter (HQ), forequarter (FQ) and combined brisket, short ribs and flank (BSF) weights. The ImC also showed smaller weights of retail cuts and bones on the HQ and on the FQ than non-castrated (NoC). Fat trim weights did not differ from ImC and NoC. The most of subprimal cuts were heavier in NoC than in ImC. Feeding β-AA did not affect cold carcass weight; however, animals fed ZH had higher weights of HQ and retail cuts in HQ when compared with RH and control (CO) group, with no differences between RH and CO for both traits. The weights of FQ, BSF, retail cuts in FQ, as well as bones and fat trimmings were not affected by β-AA. In summary, ImC decreases carcass and retail cut weights, whereas ZH supplementation leads to an improvement in carcass lean tissue and retail cuts.

Biomechanical investigation into locomotor pathology in commercial pigs is lacking despite this being a major concern for the industry. Different floor types are used in modern, intensive pig production systems at different stages of the pigs’ production cycle. The general perception holds that slatted and/or hard solid concrete surfaces are inferior to soft straw-covered floors regarding healthy musculoskeletal development. Previous studies have compared pigs housed on different floor types using clinical, subjective assessment of leg weakness and lameness. However, reliability studies generally report a low repeatability of clinical lameness scoring. The objective of this study was to quantitatively assess the long-term effect of pen floors, reflected in the biomechanical gait characteristics and associated welfare of the pigs. A cohort of 24 pigs housed on one of three different floor types was followed from 37 to 90 kg average liveweight, with gait analysis (motion capture) starting at 63 kg. The three floor types were fully slatted concrete, partly slatted concrete and deep straw-bedded surfaces, all located within the same building. Pigs underwent five repeated camera-based motion captures, 7 to 10 days apart, during which 3D coordinate data of reflective skin markers attached to leg anatomical landmarks were collected. Pigs walked on the same solid concrete walkway during captures. One-way ANOVA and repeated measures ANOVA were used to analyse the gait data. Results revealed changes over time in the spatiotemporal gait pattern which were similar in magnitude and direction for the pigs from different floor types. Significant increases in elbow joint flexion with age were observed in all pigs (P⩽0.050; +6°). There were few differences between floor groups, except for the step-to-stride ratio in the hind legs being more irregular in pigs housed on partly slatted floors (P=0.012; 3.6 times higher s.d.) compared with those on 5 to 10 cm straw-bedding in all pen areas. As the level of clinical problems was generally low in this cohort, it may be that floors elicit problems only when there is a primary predisposing factor increasing weakness in susceptible tissues.

Free-range birds such as organic broilers may ingest soil and plants during exploration. The estimation of such intakes is of great interest to quantify possible nutritional supplies and also to evaluate the risk of exposure to parasites or to environmental contaminants. Marker-based techniques are now available and would allow to quantify plant and, especially, soil intake in free-range birds, and this quantification was the aim of this study. Methodologically, the proportion of plants in diet intake was determined first using a method based on n-alkanes. Subsequently, the fraction of soil in the total intake was estimated with a second marker, acid-insoluble ash. This approach was carried out to estimate ingested amounts of plants and soil for five successive flocks of organic broilers, exploring grass-covered yards or those under trees, at two time points for each yard: 51 and 64 days of age. Each factor combination (yard type×period=flock number×age) was repeated on two different yards of 750 broilers each.

The birds’ plant intake varied widely, especially on grass-covered yards. The proportion of plant intake was significantly higher on grass-covered plots than under trees and was also affected, but to a lesser extent, by age or flock number. The ingestion of plants would generally not exceed 11 g of DM daily, except two extreme outliers of nearly 30 g. The daily plant intake under trees tended to be lower and never exceeded 7 g of DM. The amount of ingested plants increased significantly for spring flocks. It increased slightly but significantly with age. The proportion of ingested soil was significantly higher under trees than on grass-covered yards. Dry soil intake was generally low with not more than 3 g per day. Only in adverse conditions – that is, older birds exploring yards under trees in winter – soil intake reached the extreme value of nearly 5 g. Broilers on yards under trees ingested significantly more soil than on grass-covered yards with least square means of, respectively, 2.1 and 1.1 g dry soil per day. These quantifications would allow us to evaluate the impact of plant and soil intake in the management of free-range broilers, especially for the management in organic farming systems. Nevertheless, under the two rearing conditions tested in the current study, the quite low proportions of soil intakes would represent a low risk for the safety of the produced food, unless the birds explore yards on heavily contaminated soil.

The objectives of this study were to investigate the individual variation, repeatability and correlation of methane (CH4) production from dairy cows measured during 2 different years. A total of 21 dairy cows with an average BW of 619±14.2 kg and average milk production of 29.1±6.5 kg/day (mean±s.d.) were used in the 1st year. During the 2nd year, the same cows were used with an average BW of 640±8.0 kg and average milk production of 33.4±6.0 kg/day (mean±s.d.). The cows were housed in a loose housing system fitted with an automatic milking system (AMS). A total mixed ration was fed to the cows ad libitum in both years. In addition, they were offered concentrate in the AMS based on their daily milk yield. The CH4 and CO2 production levels of the cows were analysed using a Gasmet DX-4030. The estimated dry matter intake (EDMI) was 19.8±0.96 and 23.1±0.78 (mean±s.d.), and the energy-corrected milk (ECM) production was 30.8±8.03 and 33.7±5.25 kg/day (mean±s.d.) during the 1st and 2nd year, respectively. The EDMI and ECM had a significant influence (P<0.001) on the CH4 (l/day) yield during both years. The daily CH4 (l/day) production was significantly higher (P<0.05) during the 2nd year compared with the 1st year. The EDMI (described by the ECM) appeared to be the key factor in the variation of CH4 release. A correlation (r=0.54) of CH4 production was observed between the years. The CH4 (l/day) production was strongly correlated (r=0.70) between the 2 years with an adjusted ECM production (30 kg/day). The diurnal variation of CH4 (l/h) production showed significantly lower (P<0.05) emission during the night (0000 to 0800 h). The between-cows variation of CH4 (l/day, l/kg EDMI and l/kg ECM) was lower compared with the within-cow variation for the 1st and 2nd years. The repeatability of CH4 production (l/day) was 0.51 between 2 years. In conclusion, a higher EDMI (kg/day) followed by a higher ECM (kg/day) showed a higher CH4 production (l/day) in the 2nd year. The variations of CH4 (l/day) among the cows were lower than the within-cow variations. The CH4 (l/day) production was highly repeatable and, with an adjusted ECM production, was correlated between the years.

Methane (CH4) emissions associated with beef production systems in northern Australia are yet to be quantified. Methodologies are available to measure emissions, but application in extensive grazing environments is challenging. A micrometeorological methodology for estimating herd-scale emissions using an indirect open-path spectroscopic technique and an atmospheric dispersion model is described. The methodology was deployed on five cattle properties across Queensland and Northern Territory, with measurements conducted during two occasions at one site. On each deployment, data were collected every 10 min for up to 7 h a day over 4 to 16 days. To increase the atmospheric concentration of CH4 to measurable levels, cattle were confined to a known area around water points from ~0800 to 1600 h, during which time measurements of wind statistics and line-averaged CH4 concentration were taken. Filtering to remove erroneous data accounted for 35% of total observations. For five of the six deployments CH4 emissions were within the expected range of 0.4 to 0.6 g/kg BW. At one site, emissions were ~2 times expected values. There was small but consistent variation with time of day, although for some deployments measurements taken early in the day tended to be higher than at the other times. There was a weak linear relationship (R2=0.47) between animal BW and CH4 emission per kg BW. Where it was possible to compare emissions in the early and late dry season at one site, it was speculated that higher emissions at the late dry season may have been attributed to poorer diet quality. It is concluded that the micrometeorological methodology using open-path lasers can be successfully deployed in extensive grazing conditions to directly measure CH4 emissions from cattle at a herd scale.

The factors influencing the priority of access to food and the effects of the priority of access to food on their carcass traits were analyzed for Japanese Black (Wagyu) cattle in a semi-intensive fattening production system. The records of 96 clinically healthy steers and heifers were analyzed. The calves at ∼3 to 4 months of age were allocated to pens with four animals per pen; all four animals in the same pen were of the same sex and of similar body size. The ranking of the animals’ priority of access to food (1st, 2nd, 3rd and 4th), which was determined by the farm manager, was used as an indicator of social dominance in the present study. Four models including sire line, maternal grandsire line and the difference in the animals’ birth dates as fixed effects were used to analyze factors influencing the priority of access to food. Ranking was represented by ordinal scores (highest=4, lowest=1) in Model 1, and the binary scores were assigned in Model 2 (highest=1; 2nd, 3rd and 4th=0), Model 3 (1st and 2nd=1; 3rd and 4th=0) and Model 4 (1st, 2nd and 3rd=1; lowest=0). The results showed that the difference in the animals’ birth dates had a significant effect on the establishment of the priority of access to food in Model 3 (P<0.05), suggesting that animals born earlier may become more dominant in the pen. The maternal grandsire line tended to affect the social rank score in Models 2 and 3 (P<0.10). Our results indicated that the maternal grandsire line may affect the temperament of calves through their mothers’ genetic performance and thereby more aggressive calves may be more dominant and have higher priority of access to food. On the other hand, there was a significant effect of the priority of access to food on beef marbling score (BMS; P<0.05), and the priority of access to food also tended to influence the carcass weight (P=0.09). The highest BMS was observed for animals with the first rank of the priority of access to food (P<0.05), and the higher-ranking animals had the tendency to be heavier carcass than the lower-ranking animals. Our findings emphasized the importance of information about the priority of access to food determined by farmers’ own observation on implementing best management practices in small-scaled semi-intensive beef cattle production systems.

The effect of the physiological state and dietary protein level on urinary excretion of creatinine (C) and purine derivatives (PD) was studied in two experiments carried out with pregnant and lactating ewes to evaluate whether the PD/C ratio in urine can he confidently used as an index of PD excretion. In both experiments ewes were given ammonia-treated straw and concentrates including different levels of fish meal and the excretion in urine and milk and the plasma concentration of C, allantoin (AL), xanthine, hypoxanthine and uric acid was measured.

Creatinine excretion (in urine and milk) was higher in pregnant ewes than in those lactating (492 and 420 (s.e. 10.0) μmol/kg maternal live weight0.75) and no significant differences were found due to number of foetuses and dietary protein level. The coefficient of variation was 0·10 in both pregnancy and lactation and individual variation accounted for proportionately 0·78 and 0·93 of total variation. The AL/C ratio in urine was highly correlated with daily AL excretion (r = 0·90 and 0·78 in pregnant and lactating ewes, respectively). Changes in PD excretion with experimental treatments were mainly reflected in AL, as the main component (0-83) of total PD. Most of the variation in AL excretion was explained by differences in rumen fermentable organic matter intake (RFOMI) (R2 = 0·79) and AL excretion did not differ between treatments when expressed per kg of RFOMI. In contrast to this the ratio AL/digestible organic matter intake decreased with increasing levels of fish meal in the diet. Urinary PD excretion was better related to estimated PD kidney tubular load (r = 0·76) than to PD plasma concentration (r = 0·64).

The results suggest that creatinine excretion is scarcely affected by the number of foetuses in pregnancy and dietary protein level but if the AL/С in urine is used instead of total collection as an index of purines absorbed in the duodenum, differences in urinary creatinine excretion due to physiological state must be accounted for.

In three similar experiments, 2 or 3 kg of a commercial concentrate mixture, forming part of a high concentrate ration, were replaced by an equal weight of dry matter of one of four roughages: hay, straw, silage and green soilage.

The metabolizable energy content of the concentrate was 2-4 Mcal/kg. Expected daily gain was calculated according to the following energy systems: Scandinavian feed units (SFU), starch equivalent (SE), total digestible nutrients (TDN), the U.K. Agricultural Research Council system (ARC), and the U.S. National Research Council net energy system (NRC).

The replacement of 2 kg of concentrate significantly reduced daily gain only in the straw treatment. Reduction of the fat content of the carcasses was significant for all roughage treatments. The differences between the observed daily gain and the expected, as calculated by the SFU, SE and NRC systems, were highly significant, while those between the observed and those cal culated by the TDN and ARC systems were not significant. The TDN system overestimated the nutritional value of the roughages, while the SFU and SE systems underestimated it.

Lysozyme, an anti-bacterial enzyme, is mostly found in the body fluids, various tissues and secretions of animals and humans, and confers immunity against a wide range of bacterial species. The present study was carried out to elucidate the gene sequence of this enzyme in Indian Sahiwal × Holstein Friesian crossbred cattle and to explore the polymorphism of the gene as well as their association with milk production and somatic cell traits. The total length of lysozyme cDNA was found to be of 447 bp. The similarity with Bos taurus, human, pig, monkey, gorilla, mice, rat, chicken, dog and sheep was estimated as 99.1%, 85%, 81.0%, 85.2%, 84.3%, 77.9%, 77.9%, 41.4%, 40.5% and 24.6%, respectively. Polymorphism study of two fragments, extended exon1 including promoter, exon1 and partial intron1 (268 bp), and extended exon2 including partial intron1 and 2, and exon2 region (287 bp) of milk lysozyme gene was carried out by employing single-stranded conformation polymorphism (SSCP). In the extended exon1 fragment, three alleles namely A, B and C with frequencies of 0.59, 0.28 and 0.12 were observed while in the exon extended fragment, three different alleles – P, Q and R with respective frequencies of 0.61, 0.38 and 0.01 – were determined in Indian Sahiwal × Holstein Friesian cross. A total of eight haplotypes were found in this population where the most predominant one was h1 (0.52). Genotypes of exon1 extended fragment showed significant association with total milk yield, daily milk yield, peak yield and somatic cell score at P < 0.05 while that of exon2 extended fragment had significant correlation with only total lactational milk yield. Haplotype combinations also revealed significant association with total milk production where h1h1 homozygous showed highest yield during first lactation.

Five Chilean crossbred draught horses were used to study variation in work performance and biochemical and physiological parameters whilst working with a mould board plough (36 kg) for 6 h/day. The draught force, distance travelled, work done and the estimated extra energy for work were determined for each horse. The results showed that the horses used only 68·0 (s.e. 1·9)% of the total available working time ploughing a mean area of 3283 (s.e. 168) m2 with a mean depth and width of furrow of 12·6 and 22·3 cm, respectively. Estimated daily energy expenditure by the horses during work was 2·24 (s.e. 0·02) times maintenance requirements. The small changes observed in the physiological variables: heart rate, respiratory rate, packed cell volume, haemoglobin concentration and enzyme activity of creatine kinase, lactate dehydrogenase and aspartate amino transferase, showed that the horses were exercised under submaximal conditions. However, the significant increase in blood cortisol concentrations showed that horses experienced some degree of stress during ploughing work. The significant increase in blood triglycerides concentration observed after each period of work seems to demonstrate that fat mobilization is an important metabolic pathway as an energy supply for the working muscles during prolonged and low speed draught work.

Three experiments, designed as three simultaneous 4 × 4 Latin squares (21-day feeding periods), were conducted using pregnant beef cows. Diets were based on barley straw given ad libitum together with 1·7 kg dry matter (DM) of either molassed sugar-beet pulp (MSBP) (experiment 1), unmolassed sugarbeet pulp (USBP) (experiment 2), or rolled barley (BARLEY) (experiment 3). In the respective experiments, MSBP, USBP and BARLEY were given either alone, to provide about 200 g crude protein (CP) per day (CONTROL) or were supplemented with urea (U), untreated soya-bean meal (SBM) or formaldehyde-treated soya-bean meal (FT-SBM) to provide a further 200 g CP per day. The contrasting dietary treatments in the three experiments provided intakes of rumen-degradable protein (RDP) ranging from 16 to 388 g/day.

All protein supplements improved overall straw DM intakes, the improvement being significant for U only (P < 0·01). A linear relationship between the daily intake of RDP (g) and straw DM (kg) was obtained. The regression equation was:

DM intake = 5·03 + 0·0035 × RDP (R2 = 0·703; residual s.d. 0·561; d.f. 35; P < 0·001).

All protein supplements also improved the apparent digestibility of straw organic matter (OM) (P < 0·05) and the metabolizable energy (ME) obtained from straw (P < 0·01). Blood urea was increased due to supplementation with urea (P < 0·001), SBM (P < 0·01) and FT-SBM (P < 0·05). Supplementation with BARLEY appeared to improve straw DM intake over MSBP and USBP but this was not reflected in improved ME intake from straw.

During a 3-year period, from April 1991 to December 1993, in a flock with four lambing periods annually, faecal samples from lambs at weaning at the age of 3 months (no. = 1756), were examined for gastro-intestinal nematode eggs by the McMaster method. Faecal samples were also examined at the age of 9 (no. = 170), 12 (no. = 157), 15 (no. = 253) and 18 (no. = 85) months from the females only. From June to December 1993 packed cell volume (PCV) was also examined from lambs at weaning. Seven genotypes were used in this study.

The faecal egg counts were affected by genotype, birth season, type of birth and rearing, sex and age. First generation cross of Sumatra × Barbados Blackbelly had lowest eggs per g of faeces (EPG) followed by Sumatra, St Croix, Sumatra × St Croix Fl and F2 and Sumatra × Java Fat tail. Lambs born in February-March when rainfall was low had lower EPG (V < 0·05) than those born in May-June or August-September. The EPG of lambs born and reared singly were significantly lower (P < 0·001) than those born twin, triplet or quadruplet. Female lambs had lower EPG than male lambs (P < 0·001). The EPG of lambs at 3 months were higher than at 9, 12, 15 or 18 months (P < 0·001).

PCV was affected by genotype, sex, type of birth and rearing and season of birth. There was a positive correlation between PCV and weaning weight of lambs and a negative correlation between EPG and weaning weight. These results show that the crosses of St Croix and Barbados Blackbelly with local Sumatra sheep are at least as resistant or more resistant to gastro-intestinal nematodes than pure Sumatra breed and therefore these breeds can be used in cross breeding programmes to improve the body size of local Sumatra sheep.

Some studies have shown that the excessive metabolic heat production is the primary cause for dead chicken embryos during late embryonic development. Increasing heat shock protein (HSP) expression and adjusting metabolism are important ways to maintain body homeostasis under heat stress. This study was conducted to investigate the effects of in ovo injection (IOI) of vitamin C (VC) at embryonic age 11th day (E11) on HSP and metabolic genes expression. A total of 320 breeder eggs were randomly divided into normal saline and VC injection groups. We detected plasma VC content and rectal temperature at chick’s age 1st day, and the mRNA levels of HSP and metabolic genes in embryonic livers at E14, 16 and 18, analysed the promoter methylation levels of differentially expressed genes and predicted transcription factors at the promoter regions. The results showed that IOI of VC significantly increased plasma VC content and decreased rectal temperature (P < 0.05). In ovo injection of VC significantly increased heat shock protein 60 (HSP60) and pyruvate dehydrogenase kinase 4 (PDK4) genes expression at E16 and PDK4 and secreted frizzled related protein 1 (SFRP1) at E18 (P < 0.05). At E16, IOI of VC significantly decreased the methylation levels of total CpG sites and −336 CpG site in HSP60 promoter and −1137 CpG site in PDK4 promoter (P < 0.05). Potential binding sites for nuclear factor-1 were found around −389 and −336 CpG sites in HSP60 promoter and potential binding site for specificity protein 1 was found around −1137 CpG site in PDK4 promoter. Our results suggested that IOI of VC increased HSP60, PDK4 and SFRP1 genes expression at E16 and 18, which may be associated with the demethylation in gene promoters. Whether IOI of VC could improve hatchability needs to be further verified by setting uninjection group.