1. The effects of 0·9 to 1·0 kg molassed sugar beet pulp cubes, supplemented with minerals and vitamins and with either 0, 3·0 and 7·8% urea, on the voluntary intake of oat straw (either 2·0 or 3·0% crude protein) were measured in two experiments with 250 to 300 kg British Friesian steers.

2. Straw intake was increased by a maximum of about 20% when a total of about 165 g crude protein was supplied by the urea-containing sugar beet products.

3. In one digestibility trial conducted with 385 kg steers, the inclusion in sugar beet pulp of urea equivalent to 89 g and 169 g crude protein/day comparably and significantly increased the digestibility of dry matter and crude fibre.

Reproductive success is a key component of lifetime performance in dairy cows but is difficult to predict due to interactions with productive function. Accordingly, this study introduces a dynamic model to simulate the productive and reproductive performance of a cow during her lifetime. The cow model consists of an existing productive function model (GARUNS) which is coupled to a new reproductive function model (RFM). The GARUNS model simulates the individual productive performance of a dairy cow throughout her lifespan. It provides, with a daily time step, changes in BW and composition, fetal growth, milk yield and composition and food intake. Genetic-scaling parameters are incorporated to scale individual performance and simulate differences within and between breeds. GARUNS responds to the discrete event signals ‘conception’ and ‘death’ (of embryo or fetus) generated by RFM. In turn, RFM responds to the GARUNS outputs concerning the cow’s energetic status: the daily total processed metabolizable energy per kg BW (TPEW) and the net energy balance (EB). Reproductive function model models the reproductive system as a compartmental system transitioning between nine competence stages: prepubertal (PRPB), anestrous (ANST), anovulatory (ANOV), pre-ovulating (PREO), ovulating (OVUL), post-ovulating (PSTO), luteinizing (LUTZ), luteal (LUTL) and gestating (GEST). The transition from PRPB to ANST represents the start of reproductive activity at puberty. The cyclic path through ANST, PREO, OVUL, PSTO, LUTZ and LUTL forms the regime of ovulatory cycles, whereas ANOV and GEST are transient stages that interrupt this regime. Anovulatory refers explicitly to a stage in which ovulation cannot occur (i.e. interrupted cyclicity), whereas ANST is a pivotal stage within ovulatory cycles. Reproductive function model generates estradiol and progesterone hormonal profiles consistent with reference profiles derived from literature. Cyclicity is impacted by the GARUNS output EB and clearance of estradiol is impacted by TPEW. A farming system model was designed to describe different farm protocols of heat detection, insemination, feeding (amount and energy density), drying-off and culling. Results of model simulation (10 000 simulations of individual cows over 5000 days lifetime period, with randomly drawn genetic-scaling parameters and standard diet) are consistent with literature for reproductive performance. This model allows simulation of deviations in reproductive trajectories along physiological stages of the cow reproductive cycle. It thus provides the basis for evaluation of the relative importance of different factors affecting fertility at individual cow and herd levels across different breeds and management environments.

A bull beef finishing experiment was conducted with the objective of comparing physical performance of constrasting genotypes of suckler-bred bull beef animals finished intensively on a cereal-based diet at approximately 12 to 13 months of age. Nine bulls per genotype were drawn from weaned, bull calves born to one of two dam types (Belgian Blue×Holstein/Friesian (BB) or Simmental×Holstein/Friesian (SIM)) and which had been sired by one of two contrasting sire types (Aberdeen Angus (AA) or Charolais (CH)). Bull calves were weaned at approximately 8 months of age and the finishing experiment ran from approximately 9 months of age until slaughter at 12 to 13 months of age. Cereal-based concentrate diets were offered to all bulls on an ad libitum basis throughout the experimental finishing period. Dry matter intake (DMI), live-weight gain (LWG), food conversion ratio (FCR), and carcass slaughter characteristics were quantified.

Average daily LWG was 2·07, 2·11, 2·34 and 2·65 kg/day, average FCR was 5·14, 5·06, 4·70 and 4·12 kg DMI per kg LWG and average age at slaughter was 387, 381, 374 and 366 days for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. These figures showed that CH sired bulls grew faster ( P<0·001), finished at an earlier age ( P<0·01) and had better food conversion ratios ( P<0·01) than AA sired bulls. CH sired bulls also produced heavier carcasses (P<0·001) with better conformation ( P<0·001) than AA sired bulls. Average cold carcass weights (CCW) at slaughter were 309, 318, 348 and 365 kg and average conformation scores (15-point scale) at slaughter were 9·28, 10·28, 12·39 and 12·75 for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. Finished bulls from SIM dams had higher LWGs (P<0·01) and produced heavier carcasses (P<0·05) than bulls from BB dams. No statistically significant differences in fat score (15-point scale) were seen between any of the breed combinations with fat scores of 7·50, 7·25, 6·75 and 6·75 for the AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively. No significant differences in average daily food intake were observed between breed combinations in the experiment with average daily DMI being 10·6, 10·6, 11·0 and 10·9 kg/day for AA/BB, AA/SIM, CH/BB and CH/SIM bulls respectively.

Overall, there was little evidence to suggest that the rate of bull LWG declined to bring about any meaningful reduction in productivity as average bull live weight increased from approximately 9 months of age until slaughter at 12 to 13 months of age. When finished on a nutrient-rich, cereal-based concentrate diet, excellent animal performance and commercially acceptable carcasses can be produced from the UK suckler herd using genetically superior sires of either traditional UK or continental beef cattle breeds. Results from this study indicate that CH sired bulls out-performed AA sired bulls, especially when produced from SIM cows.

Winter growth of young male red deer can be increased by exposure to 16 h of light (L) and 8 h of dark (D) per day (16L: 8D). This study tested the duration of photoperiod required for this growth response, determined if the time to reach slaughter weight can be reduced and monitored plasma IGF-1, prolactin and reproductive development. Fifty male calves were allocated to five equal groups. Four groups were housed indoors and for 33 weeks from the winter solstice (22 June, southern hemisphere) until 11 February were placed under either 16L: 8D (16L), 13·25L: 10·75D (13L), 10·751:13·25D (111) or 8L: 16D (8L) photoperiods. The fifth group of deer (OC) remained outside in a gravelled enclosure. All groups were given a pelleted diet ad libitum. Group food intake was recorded daily, individual live weight was measured weekly and testes diameter and blood samples taken at weekly or 2-week intervals.

Plasma prolactin concentrations in 16L increased within 4 weeks of treatment and were different (P < 0·001) between groups from 14 August to 4 September. IGF-1 increased in both 16L and 13L 4 weeks after treatments and then increased further in 16L above that of 13L (P < 0·01). All groups grew at the same rate for the first 7 weeks. 16L then gained more weight (P < 0·001) than the other groups over the next 19 weeks (50·7 kg v. 38·5 for 13L, 35·7 for 11L, 37·0 for 8L and 37·4 for OC; s.e.d. 3·76). Food intake was positively related to growth rate in a similar way among the inside groups (P < 0·001), however there was a higher energy requirement outdoors (P < 0·05). A target live weight for slaughter of 95 kg was reached 7 weeks earlier for 16L than the other groups (P < 0·01). Testes diameter of 16L was larger than in the other groups from 13 November until 24 December (P < 0·001). The growth oflSL slowed from 1 January while that of OC increased and the live weight ofOC was equal to 16L by the end of the experiment. OC also had the largest testes diameter from 5 February onwards (P < 0·01). The live-weight increase in OC was associated with increases in both prolactin and IGF-1 levels.

This study confirmed that 16L: 8D stimulates rapid growth of young male red deer during winter for sufficient time to achieve an earlier slaughter date. The live-weight advantage was lost by late summer however. The increased growth rate was mediated by food intake and associated with increases in IGF-1 and prolactin and earlier reproductive development. Photoperiods of 13 h of light per day or less did not stimulate growth and increases in IGF-1 and prolactin were of a lower amplitude than under 16L: 8D.

The effect of reduced balanced protein (RP) diet in the F0 and F1 generation of broiler breeders on the learning ability and memory retention of the F2 generation was investigated by means of a reward v. no reward discrimination T-maze test. There were two treatments for the F0 generation: control (C) group, reared on standard commercial diets, and reduced balanced protein (RP) group, fed with RP diets (25% reduction in CP and amino acids). The female F0-progeny of each treatment was again separated into the two dietary treatments, resulting in four treatments for the F1 generation: C/C, C/RP, RP/C and RP/RP (breeder feed in F0/F1 generation). The RP diets fed breeders received on average 10% more feed than C diets fed breeders to achieve a similar target BW. The F2 generation was composed of four treatments coming from the female F1-progeny of the four treatments and were all fed with C diet (namely C/C/C, C/RP/C, RP/C/C and RP/RP/C). All four F2 generation groups were able to complete the T-maze learning test with a slight difference in success rate but a significant difference within groups was observed regarding the time needed to complete the test. In general, the RP/RP/C group needed more time for completing the test compared with the other three groups and the shortest time was recorded for the RP/C/C group. At similar ages, breeders with early learning experience spent significantly less time in completing the test compared with unexperienced breeders. Long-term memory retention was observed in all four groups whereas the learning ability in solving the test decreased with age. It took longer for the breeders to complete the test at older ages. In conclusion, under our experimental conditions, the RP dietary treatment in previous generations had no influence on the T-maze learning ability and memory retention of broiler breeders of the third generation, although it might have effects on the working performance in the T-maze learning test of F2 generation breeders.

Advancing maturity of forage maize is associated with increases in the proportion of dry matter (DM) and starch and decreases in the proportions of structural carbohydrates in the ensiled crop. Three maize silages (286 (low, L), 329 (medium, M) and 379 (high, H) g DM per kg fresh weight) plus a concentrate formulated to give isonitrogenous intakes were offered to Holstein-Friesian steers fitted with a cannula in the dorsal sac of the rumen and a ‘T’ piece cannula in the proximal duodenum in an experiment with a cross-over design that allowed four collection periods. Nutrient flow to the duodenum was estimated using chromium-EDTA. Steers consumed approximately 0·6 kg DM per day less of diet L compared with the other two diets (P=0·026), resulting in less DM being digested (P=0·005) but digestibility did not differ between diets. Similar results were obtained for organic matter. There were no differences between diets in the intake or digestibility of neutral-detergent fibre. Intake, duodenal flow and faecal output of starch were greater for steers offered diets M and H compared with those given diet L (P<0·05). In all diets rumen digestion contributed to over 90% of total digestion of starch, although rumen digestibility declined significantly with advancing maize maturity (P=0·002). Molar proportions of acetic acid were higher in diet H (P<0·05) whilst proportions of propionic acid and n-butyric acid were higher in diets M and L. There were no significant differences between diets in mean rumen pH or ammonia concentrations. Mean circulating concentrations of insulin were higher (P=0·009) in cattle given diets L and M compared with diet H. There were no differences between diets in the mean circulating concentration of growth hormone, or the frequency, amplitude and duration of growth hormone pulses, or the mean circulating concentrations of IGF-1. Changes in forage composition that accompany advancing maize maturity affect overall silage digestion and circulating concentrations of insulin.

Beef producers no longer emphasize excessive fat deposition in market cattle. Recent research findings in human health suggest that our diets should contain less fat because of the cardiovascular diseases that seem associated with greater intakes of fat. Large-frame cattle slaughtered at the same chronological age as small-frame cattle have leaner carcasses and a correspondingly greater proportion of carcass protein (Arnold, Hentges and Trenkle, 1985). Determining early in life whether a type of cattle will become obese, therefore, would be of great benefit to cattle producers. Arnold et al. (1985) reported that, at 6 months of age, large-frame steers were significantly leaner than small-frame steers.

To those engaged in the improvement of livestock the problem of the generation interval needs virtually no introduction. In mammals, the generation interval consists of two well-defined phases :

• (a) the interval between birth and sexual maturity and

• (b) the gestation period.

Whereas the length of gestation within a species is a relatively fixed period subject only to minor variations, the ages at which puberty and sexual maturity are attained are very variable, being influenced both by genetic and environmental factors. Thus, breed, strain, season of birth, plane of nutrition and system of management all contribute to determining the onset of puberty and eventual attainment of sexual maturity.

The effects of undernutrition and of the duration of undernutrition on changes in whole animal energy metabolism and on spontaneous physical activity were studied in adult, non-lactating, non-pregnant ewes. Animals were first given food at 338 kj metabolizable energy (ME) per day per kg live weight 0·75 (LW0·75), (M). Intake was then reduced by half (0·5M) during 7 weeks. Diet apparent digestibility decreased slightly with undernutrition. Rate of LW loss remained constant throughout the whole 0·5M period. Heat production (HP) declined by proportionately 0·18 within the 1st week at 0·5M and by another 0·05 in the following weeks. These latter changes were directly related to LW loss, since HP scaled to metabolic LW remained unchanged over the whole 0·5M period. Time spent standing decreased with undernutrition from proportionately 0·42 at M to 0·33 at 0·5M as a result of a reduction in the average duration of individual standing periods at all hours of the day except in a few hours preceeding feeding times. Energy cost of standing could not be dissociated from the energy cost of eating; these overall costs were not clearly modified by undernutrition but varied with time post prandially. Standing cost alone was estimated at 10 J/min per kg LW. Efficiency of ME utilization for maintenance (km) was calculated at 0·71, and ME requirements for maintenance (MEm) at 338 kj/day per kg LW0'75. No adaptation was noted with the duration of undernutrition. Accounting for the behavioural adaptation tended to increase km to 0·74 but MEm remained unchanged, suggesting that the behavioural changes observed with undernutrition were not sufficient to significantly modify whole animal energy metabolism.

Many parameters have been proposed for evaluating livestock reproduction performances in tropical farming systems. In tropical free-ranged and small-holder systems, where reproduction cycles cannot be individually observed without expensive field surveys, one of these parameters is the average number of parturitions (h) expected by reproductive female, if the female spends the whole year in the herd. A frequent approach for estimating h is to use the ratio hc = m/T, so-called ‘crude annual parturition rate’, where m is the observed number of parturitions and T is the total time of presence of the reproductive females in the herd during the year. The bias encountered when h is estimated by hc was evaluated in this paper. Six methods of estimation were used, where T was the exact observed time of presence (hc1) or approximated by monthly, quarterly, half-yearly and yearly averages or final size of the reproductive herd size (hc2 to hc6). Data came from long-term follow-up of cattle and small-ruminant herds (with data recorded at animal level) in extensive agro-pastoral systems in Senegal. In general, h was correctly estimated by hc1. Nevertheless hc1 was sensitive to competing risks (e.g. deaths, sales and slaughtering of reproductive females) and was seriously biased when intensive withdrawals of females occurred before or during the parturition peak. Reliability of crude rates progressively decreased from hc2 to hc6, corresponding to the degradation of information used for approximating T. This decrease was much lower for cattle (for which all methods had acceptable reliability) than for small ruminants. Among the compared methods, the lower reliability was observed for hc6 that we do not recommend for small ruminants. Methods hc5 and hc6 are currently used in rapid cross-sectional retrospective surveys based on the recall of the farmers on the demographic events which occurred in the herd over the last past 12 months. The study has showed that such surveys and estimates hc5 and hc6 can generate seriously biased results. More globally, annual parturition rates can be highly variable depending on the 12-month periods considered. Annual parturition rates estimated on short-term data, even with precise herd follow-up surveys, must be considered cautiously.

Studies have shown that nutrient requirement of suckling kits is not satisfied, but they can be fed a double quantity of milk (double nursing) resulting in improved BW and weight gain. The aim of our trials was to give additional solid feed during the early suckling period (3 to 15 days of age) when rabbit kits drink exclusively milk. Two experiments were conducted with animals from Pannon Rabbit Breeding Program. In experiment 1 (n=77 does, 734 kits) the does received commercial feed (C) or C pellet supplemented with 0.2 g powdered thyme/kg (CT). Within both dietary groups of the does three groups of litters were formed: no additional solid creep feeding (N); soya bean-based pellet (S); S pellet with 1% added powdered thyme (ST). In group S and ST, cylinder-shaped solid pellets were made. At the beginning (3 days of age) two pieces of pellets were placed daily into the nestbox after nursing. Later on it was increased to six pellets till 15 days of age. The kits consumed the additional solid feed (S and ST), however, it did not affect the BW, weight gain or survival. In experiment 2 (n=30 does, 240 kits) all does consumed commercial feed. The additional feed for kits was based on commercial piglet feed. Three groups were formed: the litters in control group were fed no additional solid feed (K), kits were fed additionally with pellets (8 mm of diameter) based on piglet feed powder, pellet adhesive and water (PI), and extra glycerin powder was added to the mixture of piglet feed powder and water (PG). The experiment lasted from the age of 3 days till 21 days. At the beginning six pellets were placed on the nest material. Later on the amount was gradually increased to 24 pellets till age of 15 days. The kits consumed the pellets. The BW of PI group differed from group PG at age of 5, 9, 12 and 21 days by +7.3%, +6.5%, +5.9%, +4.8%, respectively (P<0.05) and from group K at age of 12 days by +5.9% (P< 0.05). The differences were more expressed at age of 16 and 19 days in favour of group PI (from K by +7.1%, +6.9% and from PG by +5.9%, +5 8%, respectively, P<0.01) and at 21 days of age (from K by +6.2%, P<0.01). To find appropriate composition of creep feed for kits further studies are needed.

Genomic selection is becoming a common practise in dairy cattle, but only few works have studied its introduction in pig selection programs. Results described for this species are highly dependent on the considered traits and the specific population structure. This paper aims to simulate the impact of genomic selection in a pig population with a training cohort of performance-tested and slaughtered full sibs. This population is selected for performance, carcass and meat quality traits by full-sib testing of boars. Data were simulated using a forward-in-time simulation process that modeled around 60K single nucleotide polymorphisms and several quantitative trait loci distributed across the 18 porcine autosomes. Data were edited to obtain, for each cycle, 200 sires mated with 800 dams to produce 800 litters of 4 piglets each, two males and two females (needed for the sib test), for a total of 3200 newborns. At each cycle, a subset of 200 litters were sib tested, and 60 boars and 160 sows were selected to replace the same number of culled male and female parents. Simulated selection of boars based on performance test data of their full sibs (one castrated brother and two sisters per boar in 200 litters) lasted for 15 cycles. Genotyping and phenotyping of the three tested sibs (training population) and genotyping of the candidate boars (prediction population) were assumed. Breeding values were calculated for traits with two heritability levels (h2=0.40, carcass traits, and h2=0.10, meat quality parameters) on simulated pedigrees, phenotypes and genotypes. Genomic breeding values, estimated by various models (GBLUP from raw phenotype or using breeding values and single-step models), were compared with the classical BLUP Animal Model predictions in terms of predictive ability. Results obtained for traits with moderate heritability (h2=0.40), similar to the heritability of traits commonly measured within a sib-testing program, did not show any benefit from the introduction of genomic selection. None of the considered genomic models provided improvements in prediction ability of pigs with no recorded phenotype. However, a few advantages were found for traits with low heritability (h2=0.10). These heritability levels are characteristic for meat quality traits recorded after slaughtering or for reproduction or health traits, typically recorded on field and not in performance stations. Other scenarios of data recording and genotyping should be evaluated before considering the implementation of genomic selection in a pig-selection scheme based on sib testing of boars.

Body length and ultrasonic fat thickness measurements were taken on 86 live pigs in order to find an optimal probing site for estimation of lean meat proportion. The next day pigs were slaughtered and measurements with the Hennessy Grading Probe (HGP) were made in order to estimate the lean meat proportion.

Fat thickness, 6 cm off the dorsal mid line, increased from a value of 9·5 mm at a site 4 cm cranial to the last rib, progressively through intermediate sites to a value of 12·4 mm, 22 cm cranial to the last rib. Fat thickness measurements at different sites (live pigs) were highly correlated with HGP fat thickness at the site between 3rd and 4th from last rib (3/4 LR) and estimated lean meat proportion (carcasses); correlations ranged from 0.80 to 0.89 and -071 to -0.85 respectively. The most accurate predictor of estimated lean meat proportion from the live pig measurements was the measurement at 18 cm cranial to the last rib. Measurement at the site half the distance between the occipital bone and the base of the tail (midpoint) was the second-best for estimated lean meat proportion.

Generally, this midpoint on live pigs was situated around the 3/4 LR on carcasses. However, the range was considerable. Half of the number of animals had a midpoint in the range of -2.5 to 2.5 cm from 3/4 LR. The site midpoint is easily located on the animal and the results of this study suggest that it can be used as an accurate predictor of estimated lean meat proportion. Therefore it can serve as the probing site for classification of live pigs.

The objectives of this study were to investigate the effects of vitamin A (retinol) on growth hormone (GH) secretion and circulating insulin-like growth factor-1 (IGF-1) concentration in Japanese Black steers. Thirteen 10-month-old Japanese Black steers were divided into two groups: high vitamin A (H) group and low vitamin A (L) group. The animals in the H group were injected with 20 ml retinol palmitate (303 mg as retinol) intramuscularly every month throughout the experimental period. The steers in the L group were injected with vitamin A similarly at the age of 10 to 14 months. All steers were given vitamin A with the food (approx. 100 μg as retinol per kg diet) at the age of 21 to 30 months to prevent clinical vitamin A deficiency. Blood samples for analyses of vitamin A and IGF-1 were collected every 2 months. Series of blood samples for analyses of GH were collected at 15-min intervals over a 6-h period from each animal at the age of 10, 20, and 30 months. Although there was no difference in food intake between the two groups (P > 0·05), the average daily gain of the H group was greater (P < 0·001) than that of the L group. The carcass weight and subcutaneous fat thickness of the H group were significantly greater (P < 0·05) than those of the L group. The longissimus muscle area (P < 0·01) and marbling score (P < 0·001) of the L group were significantly greater than those of the H group. The serum retinol concentrations of the L group were significantly lower (P < 0·01) than those of the H group from the age of 16 months. The serum IGF-1 concentrations of the L group gradually decreased and were significantly lower (P < 0·01) than those of the H group from the age of 18 months. The overall mean concentration, peak height, area under the curve, and nadir of GH in both groups decreased with age. However, there were no significant differences (P > 0·05) in overall mean GH concentration, peak number, peak height, area under the curve, or nadir between the two groups. These results indicate that vitamin A affects the IGF-1 levels, with little or no intermediary effect on GH.

The use of a proteomic approach to investigate changes in the milk proteome is growing and has parralleled the increasing technological developments in proteomics moving from early investigation using a gel-based two-dimensional separation approach to more quantitative method of current focus applying chromatography and mass spectrometry. Proteomic approaches to investigate lactational performance have made substantial findings especially in the alterations in lactation during mastitis. An experimental model of Streptococcus uberis infection of the mammary gland has been used as a means to determine change not only in the milk proteome, but also in the peptidome and in the metabolome caused by the infection. Examination of the peptidome, that is the peptides of less than 25 kDa in molecular weight, demonstrated an increase in small peptides most of which were casein degradation products but also included small bioactive peptides such as mammary-associated serum amyloid A3 (MSAA3). The peptidome has also been shown to differ depending on the causative bacteria of naturally occuring mastitis. The use of a non-gel-based relative quantitative proteomic methodology has revealed major changes in the protein component of milk in mastitis. The S. uberis infection lead to increases in the concentrations of proteins such as cathelicidins, haptoglobin, MSAA3 and decreases milk content of proteins such as xanthine oxidase, butyrophilin and β-1,4-galactosyltransferase. Analysis of all protein change data identified the acute phase, coagulation and complement pathways as well as proteins related to bile acid metabolism as being most modified. Examination of the small molecular weight organic molecules of milk using a metabolomic approach identified an increase in the content in milk during mastitis of bile acids such as taurochenodeoxycholic acid. Notable changes were also found in metabolites responding to infection of the mammary gland. Carbohydrate and nucleic acid metabolites were reduced, whereas lipid and nitrogen containing metabolites were increased. The latter included increases in amino acids along with di and tri peptides, likely to be the result of casein degradation. The use of proteomics and other omic technology is in its infancy in investigation of lactational parameters, but can already provide additional insight into the changes involved in disease and will have further value in physiological and nutritional investigation of lactation.

The use of barley for intensive beef production, as described by Preston, Aitken, Whitelaw, Macdearmid, MacLeod and Philip (1963) is now a well established practice, but one of the hazards of this feeding system is bloat. There is evidence that the risk of this condition is accentuated if the barley husk is broken down too finely as happens if the grain is ground (Preston, Macdearmid and MacLeod, 1963; Preston, 1964). It was therefore recommended that barley should be processed in a roller mill and that the moisture content should be at least 16% (Preston, 1963), for if the grain is drier than this it is difficult to prevent excessive shattering and destruction of the husk. Suitable containers, which can be sealed in order to ensure anaerobic conditions and so overcome the problem of storing damp grain (greater than 16% moisture) have additional advantages at harvest since they can be filled quickly and easily. The purpose of this experiment was to evaluate the nutritive value of barley stored under these conditions.

The response to long-term continuous infusion of gonadotrophin releasing hormone(GnRH)was monitored in progesterone-treated seasonally anoestrous ewes. Using osmotic pumps, groups of five ewes eachreceived 0(controls),125, 250, 500 or 1000 ng GnRH per h subcutaneously for a period of 21 days. Bloodsamples were collecte dat 30-minintervals from 6 h before until 24 h after the start of treatment and then for 8-h periods on days 2, 8, 15 and 21. After 21 days of treatment all the ewes were slaughtered to determine pituitary GnRH receptor numbers. Continuous infusion of GnRH resulted in a short-lived (2day)increase in plasma LH and oestradiol concentrations after which they were not different from the pre-treatment values. Over the later period of treatment when the pituitary gland was not responding to the exogenous GnRH(days 8, 15 and 21), LH episodes(presumably due to endogenous GnRH secretion fromthe hypothalamus) were observed. Continuous infusion of GnRH was also associated with a suppression in plasma FSH concentrations, the duration of which was dose-dependent. Only at the highest GnRH dose level(1000 ng/h)was there a significant reductionin pituitary GnRH receptor content.

The effects of various genetic and environmental factors on body-weight traits were studied in 3051 records of Bauscat (B) and Giza White (G) rabbits in the period from October 1976 to September 1983. Sixty-five sires and 289 dams were used for analysis of data of body weight at 6 weeks and bi-weekly up to 12 weeks of age. Year and month of birth exerted a pronounced effect on body weights of rabbits. Sex differences on the other hand were small at all ages studied and no pattern of parity effects was observed. Effects of litter size at birth were significant for 6-week weight but not for weights taken at later post-weaning ages. Body weights at the four ages studied decreased as litter size at weaning increased. Litter-weight effects on body weights decreased significantly as the age of the rabbit advanced. Sire and dam affected significantly most of the body-weight traits studied. The proportion of variance attributable to both sire and dam components for all body weights studied in G rabbits were generally larger than those in B rabbits. Heritabilities from sire and dam components of variance for body weights n i B rabbits were substantially lower than the corresponding estimates in G rabbits. Genetic and phenotypic correlations among body weights at all ages studied were positive and of moderate or high magnitude, and tended to decrease in value as the differences between the two ages increased.

Four experiments were conducted to study the performance of pigs weaned at 10 days on to diets containing different amounts of flaked maize.

Digestibilities of dry matter and energy of flaked maize were found to be 0·87 for pigs between 11 and 16 days of age.

Starter diets containing 0, 250 or 375 g flaked maize/kg, given from 10 to 35 days, resulted in growth rates of 254, 254 and 213 g/day respectively and the reduction with the high level of maize was significant (P< 0·001). Feed conversion ratio was unaffected by treatment and averaged 1·08.

When the starter diets were replaced at about 24 or 27 days by a cereal-based diet containing 200 g dried skim milk/kg there were no significant differences in performance between 10 days and 10 kg live weight due to starter diet, and growth rates were similar t o those obtained when the starter diets were given to 35 days. However, there was a consistent trend of lower food intakes, poorer feed conversion ratio and, consequently, poorer growth during the immediate post-weaning period on the starter diet containing 375 g flaked maize/kg.

Yeast culture (YC) based on Saccharomyces cerevisiae has been reported to stimulate bacterial activity within the rumen, leading to increases in ruminal fibre digestion and microbial protein flow from the rumen (Wallace and Newbold, 1992). Dawson (1987) suggested that S. cerevisiae might grow in the rumen. Newbold et al (1990) found no evidence for the growth of S. cerevisiae in the rumen of sheep when the numbers of live yeast in the rumen were measured at various times after a diet contain YC had been consumed. The current experiment was designed to investigate further the possibility that S. cerevisiae grows in the rumen and to establish the importance of viable yeast cells in the action of YC in the rumen.