Food intake in pigs is highly variable across different production circumstances. This report concludes from a critical review of published observations that it was unrealistic to expect from the scientific literature purporting to express nutrient requirement any reasonable prediction of the particular food intake of groups of pigs. None the less, such knowledge is essential for the practical purposes of their day-to-day nutrition. The literature does however yield general principles from which may be derived: (a) the likely forms (but not the parameter values) of intake functions relating food intake to pig live weight; and (b) the likely factors involved in the modulation of food intake at any given live weight. Using these principles two methods for determining on-farm food intake from the use of simple and available records were proposed. The first requires knowledge only of start and final weight, the time elapsed, and total food intake: it involves two steps, the determination of a suitable growth curve followed by the fitting of a suitable food intake curve. The second method is appropriate in the absence of information on total food intake, and requires a minimum number of spot measurements through the growth period. Different functions were tested for the curve of best fit. As a further benefit it appeared that models could be constructed from the information presented that would speculate for diagnostic purposes upon the likely modulators of food intake. Such models could explore the constraints of gut capacity, the energetic requirements of maintenance and potential growth, the influence of excessive or inadequate environmental temperature, the quality of housing and stocking density.

Clinical mastitis (CM) and monthly test-day somatic cell count (SCC) records on Holstein cows were used to investigate the genetic and economic relationship of lactation average (of natural logarithms of) monthly test-day SCC (LSCC) with CM. After editing, there were 23663 lactation records on 17937 cows from 257 herds. Three groups of herds were first identified as having low (L), medium (M) and high (H) incidences of CM from the original or pooled (P) data set. Genetic parameters were estimated for the original and three data sub-sets (derived from the three herd groups). Expected genetic responses to selection against CM were calculated using genetic parameters of each data set separately, with an adapted version of the UK national index (£PLI-profitable lifetime index). Indirect economic values of SCC (EVSCC) were calculated as the direct cost of CM per cow per lactation weighted by the genetic regression coefficient of CM lactation records on their sires’ predicted transmitting ability for SCC (PTASCC). All genetic regression analyses were based on linear and threshold-liability models. Heritabilities and repeatabilities, respectively, were 0034 and 0·111 for CM and 0120 and 0·347 for LSCC in the original data set. Genetic, permanent environmental, residual and phenotypic correlations between CM and LSCC for the original (pooled) data set were 0·70, 0·44, 013 and 0·20, respectively. Parameter estimates for the three herd groups differed, with magnitude of the estimates increasing with increase in incidence from L to H herd groups. The EVSCC per unit of PTASCC for L, M, H and P herd groups, respectively, were £004, £0·15, £0·33 and £018 on the observed and £0·86, £0·96, £1·22 and £110 on the underlying-liability scales. Selection for mastitis resistance, using SCC as an indicator trait in an extended version of £PLI, resulted in a selection response of 0·9, 21, 1·7 and 1·9 more cases per 100 cows after 10 years of selection in L, M, H and P herd groups, respectively. These results suggest that genetic responses to selection for CM resistance as well as the EVSCC are specific to herd incidence and hence would be appropriate for customized selection indexes. The increase in CM cases was greater when CM was excluded from the £PLI (2·8 v 1·9), hence it is recommended that CM should be included in the breeding goal in order to arrest further decline or to make improvement in genetic resistance to clinical mastitis.

Current selection objectives for dairy cattle breeding may be favouring cows that are genetically predisposed to mobilize body tissue. This may have consequences for fertility since cows may resume reproductive activity only once the nadir of negative energy balance (NEB) has passed. In this study, we repeatedly measured food intake, live weight, milk yield and condition score of Holstein cattle in their first lactation. They were given either a high concentrate or low concentrate diet and were either selected or control animals for genetic merit for kg milk fat plus milk protein. Orthogonal polynomials were used to model each trait over time and random regression techniques allowed curves to vary between animals at both the genetic and the permanent environmental levels. Breeding values for bulls were calculated for each trait for each day of lactation. Estimates of genetic merit for energy balance were calculated from combined breeding values for either (1) food intake and milk yield output, or (2) live weight and condition-score changes.

When estimated from daily fluxes of energy calculated from food intake and milk output, the average genetic merit of bulls for energy balance was approximately -15 MJ/day in early lactation. It became positive at about day 40 and rose to +18 MJ/day at approximately day 150. When estimated from body energy state changes the NEB in early lactation was also -15 MJ/day. It became positive at about day 80 and then rose to a peak of +10 MJ/day. The difference between the two methods may arise either because of the contribution of food wastage to intake measures or through inadequate predictions of body lipid from equations using live weight and condition score or a combination of both. Body energy mobilized in early lactation was not fully recovered until day 200 of lactation. The results suggest that energy balance may be estimated from changes in body energy state that can be calculated from body weight and condition score. Since body weight can be predicted from linear type measures, it may be possible to calculate breeding values for energy balance from national evaluations for production and type. Energy balance may be more suitable as a breeding objective than persistency.

Data were analysed from a long-term selection experiment with Merino sheep, based on immunological responsiveness to the intestinal nematode Trichostrongylus colubriformis. For the first 14 years of selection, the criterion was the mean of five fortnightly faecal worm-egg counts (FECs) of pen-housed lambs that were vaccinated with irradiated larvae then challenged with normal T. colubriformis larvae. For most of the lambs born in the subsequent 6 years, the selection criterion was the mean of three weekly FECs of grazing lambs following a secondary challenge with T. colubriformis larvae. Data from 2233 lambs were included in the analyses.

At the end of the experiment, the lines selected for high and low response to challenge differed by 2·3 to 2·9 phenotypic standard deviations. The heritability of average pen-tested FEC was 0·38 (s.e. 0·04), similar to that for average FEC after secondary field challenge (0·37, s.e. 007). Average FECs from the primary field challenge were less heritable (0·21, s.e. 006). Counts recorded on pen-tested animals at 3, 5, 7, 9 and 11 weeks after infection were all highly correlated genetically (estimates 0·93 to 0·99) and of similar heritability (0·33 to 0·39) with a non-significant tendency for later FECs to be more heritable. Phenotypic correlations were lower, ranging from 0·60 for counts 8 weeks apart, to 0·78 to 0·81 for adjacent samples 2 weeks apart. Single-record heritability estimates at 3, 4 and 5 weeks after secondary infection in grazing lambs did not differ statistically from each other but were highest at the 5th week after infection at 0·33 (s.e. 007).

FECs determined in pens were imperfectly correlated with FECs determined at pasture (genetic correlation 0·72, s.e. 013). Phenotypic correlations of single-record FECs across primary and secondary field challenges were low (around 0·2), although the genetic correlation between mean primary FEC and mean secondary FEC was not significantly different from unity. Testing under standardized conditions in pens did not result in consistently higher heritabilities than testing immunologically primed lambs at pasture. Repeated measurement in a breeding programme offers little additional benefit, except when lambs have had ample prior experience of parasite infection, with the two measures separated by an anthelmintic treatment. If an objective of a Merino breeding programme is to reduce FEC under field conditions, then using one measure in the field, approximately 3 to 5 weeks after a secondary artificial infection, is likely to lead to long-term progress.

In this paper a methodology is developed to improve the design and implementation of a linear morphological system in beef cattle using artificial intelligence. The proposed process involves an iterative mechanism where type traits are successively defined and computationally represented using knowledge engineering methodologies, scored by a set of trained human experts and finally, analysed by means of four reputed machine learning algorithms. The results thus achieved serve as feed back to the next iteration in order to improve the accuracy and efficacy of the proposed assessment system. A sample of 260 conformation records of the Asturiana de los Valles beef cattle breed is shown to illustrate the methodology. Three sources of inconsistency were detected: (a) the existence of different interpretations of the trait’s definition, increasing the subjectivity of the assessment; (b) the narrow range of variation of some of the anatomical traits assessed; (c) the inclusion of some complex traits in the assessment system. In this sense, the reopening of the evaluated Asturiana de los Valles assessment system is recommended. In spite of the difficulty of collecting data from live animals, further implications of the artificial intelligence systems on morphological assessment are pointed out.

A study was carried out from 1992 to 1996 to compare the resistance to naturally acquired gastro-intestinal (GI) nematode parasite infections (predominantly Haemonchus contortus) of Galla and Small East African goats in the sub-humid coastal region of Kenya. A total of 204 Galla and 349 Small East African (SEA) kids were born from five kiddings. These were the progeny of 18 Galla and 17 SEA bucks. Live weights (LWT), blood packed-cell volume (PCV) and faecal egg count (FEC) were recorded at 1- to 2-month intervals from birth to about 14 months of age. The SEA kids were more resistant to GI nematode parasites than Galla kids as shown by their significantly lower FEC (P < 0·001) in the post-weaning period (8- to 14-month-old kids) and lower mortality from birth to 14 months of age (P < 0·05). There was no significant (P > 0·05) breed effect on PCV, but Galla kids were significantly heavier (P < 0·001) at all measurement times between birth and 14 months of age. Heritability estimates for LWT, PCV and FEC at the different sampling times were characterized by high standard errors. Heritability estimates for records taken at 4·5 and 8 months of age from a repeated measures analysis were 0·18 (s.e.0·08) for PCV and 0·13 (s.e.0·07) for logarithm-transformed FEC. The phenotypic and genetic correlation estimates between PCV and LFEC were moderately to highly negative and averaged –0·36 and –0·53, respectively. The results are discussed in relation to the limited evidence for resistance to GI nematode infections in goats and compared with the much stronger evidence for resistance in sheep.

The present study was designed to examine the pattern of changes in plasma leptin concentration during the early stage of young ruminants. Five crossbred lambs weaned at 45 days were housed individually in pens. The lambs were offered timothy hay, rolled barley and soya-bean meal to meet a 200 g daily gain, and were given free access to water and mineral block. Blood samples were collected just before the morning feeding and at 30-min intervals for 6 h after the morning feeding beginning at 0·5 months after weaning and thereafter monthly for the next 6 months. Plasma leptin level increased dramatically from 0·5 to 3 months after weaning. Thereafter, it dropped to a similar level to that at 2 months after weaning and remained at that level. Moreover, plasma leptin level was not affected by feeding, and no variation throughout the day of sampling was observed. Plasma insulin levels showed similarity to changes in plasma leptin levels. Plasma insulin levels were positively correlated (r = 0·63) with plasma leptin levels. This study shows that plasma leptin level dramatically increases after weaning. Additionally, it suggests that insulin contributes to the increase of leptin with growth in lambs.

Differences in receptor binding affinity for insulin, and insulin receptor concentration, were found in skeletal muscle and adipose tissue of lambs differing in genotype and gender. The Rouge de l’Ouest lamb genotype had a lower receptor affinity for insulin in m. rectus capitis skeletal muscle compared with both Dutch Texel and Greyface lamb genotypes (P < 0·01). Insulin receptor concentration in m. longissimus dorsi skeletal muscle was greater in the Texel lamb genotype compared with both the Greyface (P < 0·001) and Rouge de l’Ouest (P < 0·05) lamb genotypes. Insulin receptor concentration in perirenal fat tissue was greater in the Rouge de l’Ouest lamb genotype compared with the Texel lamb genotype (P < 0·05).

There were no differences in receptor affinity for insulin between individual tissues in male and female lambs. The concentration of insulin receptors in male lambs was greater in m. longissimus dorsi (P < 0·05), subcutaneous adipose tissue (P < 0·05) and perirenal fat (P < 0·001) compared with female lambs. Receptor affinity for insulin in individual tissue depots also demonstrated significant genotype ✕ gender interactions. M. longissimus dorsi had a lower receptor affinity for insulin in Texel male lambs compared with Greyface male lambs (P < 0·05). M. rectus capitis had a lower receptor affinity in Rouge de l’Ouest male lambs compared with Texel male lambs (P < 0·01). M. rectus capitis also had a lower receptor affinity for insulin in Rouge de l’Ouest female lambs compared with both Texel and Greyface female lambs (P < 0·01). Within individual genotypes, m. longissimus dorsi had a lower receptor affinity for insulin in Greyface female lambs compared with Greyface male lambs (P < 0·05) whereas m. rectus capitis had a lower receptor affinity for insulin in Texel female lambs compared with Texel male lambs (P < 0·05).

Such differences in tissue receptor affinity for insulin and receptor concentration in lambs differing in genotype and gender could, through effects on tissue sensitivity and/or responsiveness to insulin, manipulate nutrient partitioning between skeletal muscle and fat tissue and hence control, at least in part, the efficiency of lean meat production.

Three weaning treatments (weaning at 45 days of age, at 65 days of age, unweaned) and two slaughter weights (24 and 28 kg) were compared in lambs raised at pasture, and their effect on carcass and meat traits were studied. Unweaned lambs displayed a greater growth rate, lower concentrate consumption, greater dorsal fat thickness, more kidney knob and channel fat and greater total fat levels, measured through dissection of the hind limb. Total collagen concentration was lower in unweaned lambs and the intramuscular fat of these same animals exhibited a greater proportion of saturated fatty acids and a lower n-6/n-3 fatty acid ratio. Slaughter weight influenced scored carcass fatness, which was greater in heavier lambs, meat colour, which displayed greater lightness in lower-weight lambs, and water-holding capacity, which was lower in lambs with the lower slaughter weight. The heavier lambs displayed lower soluble collagen values, and the intramuscular fat of the longissimus dorsi muscle of these same lambs contained higher levels of monounsaturated and lower levels of polyunsaturated fatty acids.

The aim of this study was to evaluate the performance and digestive response of the growing rabbit according to a change in the nature of the lignocellulose (ADF), without a change in the ADF level. Three diets with a linearly decreasing lignin/cellulose ratio (ADL/cellulose = 0·8; 0·4; 0·2; respectively LC8, LC4, LC2) were given to a total of 162 rabbits per diet, from weaning till slaughter weight. A reduction of the ADL/cellulose ratio led to a lower food intake (LC8 v LC2: -11%), associated with a lower daily weight gain (-6% for LC2). Mortality and morbidity rate was significantly greater (+50%) for LC2 and LC4 diets compared with the LC8. Thus, the health risk index (morbidity + mortality) increased by 20 units for LC4 and LC2 compared with LC8 diet. In parallel, rate of passage was slower (mean retention time 4·5 h greater, P = 0045) with LC4 and LC2 diets. Dry-matter digestibility was slightly affected, whereas protein digestion was favoured with low ADL/cellulose ratio. It is recommended that a minimum lignin supply (about 6 g/day) is adopted as well as a minimum dietary lignocellulose to ensure growth performance and health of the growing rabbit.

Many studies with fin fish have demonstrated the potential to use alternative dietary protein sources to fish meal based on growth responses, although these trials mostly neglect to determine if such protein sources affect immune function. This study investigated the effect of fish meal replacement with dehulled lupin meal (LPN) or hydrolysed poultry feather meal (FTH). Atlantic salmon (Salmo salar L.) parr were supplied isonitrogenous and isoenergetic diets with 40% of the dietary protein provided by LPN or FTH, or 400 g/kg of the dietary protein provided equally by LPN and FTH (MIX). A diet mainly containing fish-meal protein acted as a control (CON). Growth, immune function, blood chemistry and disease resistance were assessed after 56 days. Significant differences (P < 0·05) in weight gain were detected between Atlantic salmon given the CON and FTH diets, whilst those salmon given LPN and MIX did not differ from any other. Productive protein values were significantly lower (P < 0·01) for salmon on FTH compared with those on CON and MIX. Immune function (as assessed by lysozyme, antiprotease, neutrophil oxygen radical production and plasma total immunoglobulin) and blood chemistry (as assessed by plasma total protein and glucose) were not significantly (P > 0·05) affected by any diet. Mortality rates of Atlantic salmon challenged with Vibrio anguillarum were not influenced by diet. These data suggest Atlantic salmon could be supplied diets with the fish meal component reduced to supply approximately 600 g/kg of the total protein, with the remaining 400 g/kg supplied by dehulled lupin meal or a combined dehulled lupin and hydrolysed poultry feather meal without any adverse effects on growth, immune function or blood chemistry.

The effect of recombinant bovine FSH (rbFSH) administration on serum FSH and follicular growth was determined in 16 GnRH-immunized heifers (primary day 0 and booster day 28 using 0·4 mg human serum albumin (HSA) – Cys-Gly-GnRH in DEAE-dextran). All heifers produced GnRH antibody titres (mean 58·8 (s.e. 2·8)% binding at 1: 640 serum dilution on day 42), follicular growth ceased (follicles ≤ 4 mm) between days 33 and 49, progesterone concentrations were ≤ 0·5 ng/ml in all heifers by day 53, and pulsatile LH secretion was markedly reduced (v. luteal phase control heifers) on day 63. Heifers were blocked by antibody titre and LH concentrations on day 63 and assigned (no. = five or six per treatment) on day 78 to: (1) control (saline given i.m. four times per day for 4 days), (2) 0·5 mg equivalent (USDA bFSH BP 1) of rbFSH (Granada Biosciences, TX) given i.m. four times per day for 6 days (12 mg in total) or 3) 1·5 mg rbFSH given i.m. four times per day for 4 days (24 mg in total). Ovaries of heifers were examined by ultrasound and blood samples were collected at 3- to 6-h intervals from days –1 to 10 and then twice a day until follicles ≥ 5 mm were no longer detectable. The increase in serum FSH concentrations was different (P < 0·05) between treatments (mean peak FSH above pre-treatment baseline concentrations at 102 h after first rbFSH were 1·4 (s.e. 0·8), 14·5 (s.e. 3·3) and 33·6 (s.e. 5·3) ng/ml for treatments 1 to 3, respectively). The rate of decline in FSH from 102 to 302 h was not different between treatments 2 and 3. There was no detectable follicular growth in heifers given saline injections. Following either rbFSH treatment, medium (MF; 5 to 9 mm) and large (LF; ≥ 10 mm) follicles grew. For heifers in treatments 2 and 3, there was no difference in the interval from start of rbFSH until the first appearance of MF (4·2 (s.e. 0·7) v. 3·3 (s.e. 0·3) days) or LF (5·3 (s.e. 0·3) v. 4·8 (s.e. 0·8) days) or in the duration of the presence of MF and/or LF (13·2 (s.e. 4·5) v. 16·6 (s.e. 2·6) days). Increasing dose of rbFSH increased (P < 0·05) the mean maximum number of MF (4·3 (s.e. 1·1) and 9·2 (s.e.0·9) for treatments 2 and 3) and LF (2·0 (s.e. 1·1) and 8·4 (s.e. 1·2)). In summary, low doses of rbFSH induced a small cohort of follicles to grow and develop without selection or development of a single dominant follicle, whereas high doses of rbFSH resulted in large numbers of both MF and LF.

Two experiments with lambs given food indoors and individually penned were designed to study the effects of different levels of ground maize and citrus pulp as supplements of a diet based on urea-treated straw (5 kg urea per 100 kg straw) offered ad libitum over a period of 16 weeks (experiment 1) or 10 weeks (experiment 2). The voluntary intake, live-weight gain (LWG), organic matter digestibility (OMD), urinary allantoin-nitrogen (UAN) excretion and acetate clearance rate were measured. The lambs were blocked on weight and randomly assigned to the treatments described below. Ruminal outflow rate of the solid and liquid phases from the rumen were also measured in experiment 2.

In experiment 1, 20 female lambs from the Ile-de-France breed, with an initial live weight (LW) of 43 (s.e. 3·3) kg were used. Wheat straw (WS) was supplemented with 50 g/kg of fish meal (FM) and with 0, 100, 200 or 300 g/kg of ground maize on a dry-matter (DM) basis (M0, M1, M2 and M3, respectively). In experiment 2, 25 female lambs from the Portuguese breed Churra-da-Terra-Quente, with an initial LW of 24·2 (s.e. 4·3) kg were used. The straw was offered ad libitum during 10 weeks and supplemented with 50 g/kg of FM and 0, 100, 200, 300, or 400 g/kg of dried citrus pulp on a DM basis (CP0, CP1, CP2, CP3 and CP4, respectively).

During the experiments, all animals were moved to metabolism cages to measure OMD and UAN excretion. Two additional incubation studies were carried out with rumen fistulated rams (experiment 1) or cows (experiment 2) given the diets described above close to the maintenance feeding level.

In experiment 1 daily straw DM intake linearly decreased (P < 0·05) from 21·6 to 17·7 g/kg LW and LWG linearly increased (P < 0·05) from 51 to 154 g/day for treatments M0, M1, M2 and M3, respectively. The rate of straw DM degradation was significantly decreased (P < 0·01) by maize supplementation. Straw OMD (kg/kg) was 0·562, 0·583, 0·547 and 0·520 and UAN (mg/day) was 620, 790, 854 and 859 for treatments M0, M1, M2 and M3, respectively. Acetate clearance rate, increased (P < 0·05) as the level of maize inclusion increased.

In experiment 2 daily straw DM intake was 23·3, 25·8, 24·7, 23·5 and 18·6 g/kg LW per day and LWG was –9, 28, 44, 64 and 67 g/day for treatments CP0, CP1, CP2, CP3 and CP4, respectively. Supplementation significantly increased LWG (P < 0·001) but at the 400 g/kg level depressed straw DM intake. Straw OMD linearly decreased (P < 0·05) from 0·484 (CP0) to 0·428 (CP4) g/kg and UAN (mg/day) was 181, 303, 363, 384 and 392 for treatments CP0, CP1, CP2, CP3 and CP4, respectively. Rumen outflow rate of fibre particles was unaffected by supplementation while the outflow of liquid phase tended to be increased (P < 0·10). The rate of DM degradation was significantly reduced (P < 0·01) by citrus-pulp inclusion. Acetate clearance rate was unaffected (P > 0·05) by citrus-pulp supplementation.

The results of these experiments demonstrate that supplementation of urea-treated straw with ground maize up to 200 g/kg or with citrus pulp up to 300 g/kg of the diet DM increased or did not depress straw intake, increased the supply of microbial protein and have no significant effect on straw digestibility. The efficiency of utilization of absorbed energy was apparently improved by maize but not by citrus-pulp supplementation.

This paper reports the results of three experiments designed to attempt to improve the efficiency of milk production from diets based on a 1: 2 dry matter (DM) mixture of grass silage and whole-crop wheat (WCW) harvested at 550 to 600 g DM per kg and treated with 40 g urea per kg DM. In the first experiment a control diet of the forage mixture offered ad libitum with 9 kg fresh weight (FW) per day of a concentrate mix was compared with seven treatments in which the forage or the concentrates were varied. Eight multiparous cows were used in a four-period incomplete change-over design with 4-week periods. Caustic treatment of the WCW increased DM intake (P < 0·001) but tendencies for higher yields of milk and milk protein were not significant. Replacement of 2 kg FW concentrates per day by the same weight of molasses as a 24-h pre-soak of the forage (molasses pre-treatment) or added to the forage at feeding increased DM intake (P < 0·001) but did not increase milk yield or yield of milk solids. Molasses pre-treatment and molasses added to the concentrates reduced milk protein concentration (P < 0·05). Replacement of 2 kg FW concentrates per day by the same weight of ground wheat increased DM intake when added to the concentrates (P < 0·001) but not when added to the forage and milk yield was unaffected by either method of addition. The ground wheat tended to reult in higher milk protein concentrations than the molasses. Increasing the digestible undegradable protein content of the concentrates had no significant effect on food intake or milk production. In the second experiment diet digestibility and energy and nitrogen (N) balance were measured for the control diet and three of the treatments from experiment 1 in four multiparous cows in a 4 ✕ 4 Latin-square experiment with 5-week periods. There were no significant effects on food intake or milk yield. Caustic treatment reduced starch digestibility (P < 0·001) and increased neutral-detergent fibre (NDF) digestibility (P < 0·05) but had no effects on energy utilization. It also reduced N intake (P < 0·01) and urine N losses (P < 0·001) by reducing the ammonia concentration of the WCW. Molasses added to the forage or concentrates reduced milk protein concentration (P < 0·05) and digestibility of both starch and NDF (P < 0·05) but energy utilization was unaffected. In a further Latin-square experiment with the same treatments and four fistulated lactating cows, caustic treatment reduced daily mean ammonia concentration (P < 0·01) and increased daily mean pH (P < 0·01) in the rumen. It is concluded that these treatments did not generally improve the value of WCW although caustic treatment increased milk yield and milk protein yield consistently but not significantly. However practical problems may limit its use on the farm. Urea-treated WCW must be accepted as being a relatively low-energy food although with high intake characteristics, and future work should concentrate on evaluating WCW harvested at an earlier stage of maturity.

In each of 2 years (years A and B), the effects of three nutritional regimes were examined using 12 cows kept at pasture for 77 days at 2000 m above sea level. Two supplement formulations (1 and 2) were designed, both equally high in readily fermentable energy (14·6 MJ metabolizable energy (ME) per kg dry matter (DM)) but differing in crude protein content (53 and 193 g/kg DM). The treatments imposed were either pasture grass alone (control groups; both seasons) or grass and supplements provided at three levels relative to energy (E) and protein (P) maintenance requirements estimated for lowland conditions. These levels were (i) 1·0 E: 0·8 P provided by 4·6 kg of supplement 1 per day in both years; (ii) 0·5 E: 0·4 P provided by 2·2 kg of supplement 1 per day in year A; (iii) 1·0 E: 2·5 P provided by 4·4 kg of supplement 2 per day in year B. Intensive measurement periods, including food intake estimation by the double alkane technique, were carried out in weeks 3, 7 and 11 on Alpine pasture. Performance data, plasma levels of indicative blood traits and body condition were additionally monitored in the cows at a lowland site for 2 weeks prior to transport. Supplementing with a high energy/low protein concentrate gave no clear benefit in milk yield, which declined proportionately by 0·33 in the 11 weeks under Alpine conditions. Provision of additional supplementary protein (supplement 2) resulted in a proportionate decline in milk yield of only 0·20 over the 11-week period. Cows exhibited high substitution ratios of 1·4 to 2·6 kg herbage DM per kg concentrate DM and cows on all treatments were estimated to consume similar amounts of ME. A combination of reduced fibre intake and lower fibre digestibility with supplementation significantly reduced milk fat contents to low levels. Energy supplementation significantly reduced plasma β-hydroxybutyrate levels. However, live-weight and body tissue loss rates (based on ultrasonic scans of subcutaneous fat layer and longissimus dorsi muscle) were equally great with and without energy supplementation but less severe with extra protein (supplement 2). Adaptation to the high Alpine conditions was achieved in all treatments as indicated by increased blood haemoglobin, accompanied by a lower plasma level of insulin-like growth factor-I. Plasma thyroid hormone levels suggested that adaptation to energy deficiency and possibly to cold was more effective with supplementary energy. Other energy-dependent blood metabolites and insulin responded similarly in all treatments to high altitude grazing. Estimated maintenance energy requirement for Alpine conditions was 0·72 times greater than lowland maintenance requirement.

The effects of trace element deficiencies in lambs, particularly zinc, copper, cobalt and selenium, include decreased growth rates and increased mortality. However, trace element supplementation of sheep reared under extensive conditions has several logistical problems.

Two trials were designed to investigate the effect of a zinc, cobalt and selenium soluble glass bolus on the trace element status of out-wintered ewe lambs. In trial 1 600 8-month-old ewe lambs (500 Scottish Blackface and 100 North Country Cheviots) were allocated to two treatment groups; 300 were treated with a zinc, cobalt and selenium soluble glass bolus (zinc) and 300 were untreated (control). In trial 2, 315 8-month-old Scottish Blackface ewe lambs were allocated to three treatments: 105 were treated with the zinc, cobalt and selenium soluble glass bolus (zinc), 105 were treated with a copper, cobalt and selenium soluble glass bolus (copper) and the remaining 105 were untreated (control). Blood samples were collected immediately prior to giving boluses and again after approximately 4 months. These were assessed for zinc (plasma zinc concentration), cobalt (serum vitamin B12 concentration), selenium (erythrocyte glutathione peroxidase activity) and copper status (plasma copper concentration, caeruloplasmin, amine oxidase and superoxide dismutase activity and calculation of the ratio between the caeruloplasmin and plasma copper).

The zinc bolus in both trials significantly increased the plasma zinc concentrations (P < 0·001 and P < 0·01 respectively), erythrocyte glutathione peroxidase activities (P < 0·001) and serum vitamin B12 concentrations (P < 0·001). The copper bolus also significantly increased the erythrocyte glutathione peroxidase activities (P < 0·001) and serum vitamin B12 concentrations (P < 0·001) when compared with the controls but were not significantly different from the zinc group. The copper bolus significantly increased all of the copper status indicators (P < 0·01) when compared with the control and zinc groups. However, in trial 1 when only the zinc and control groups were compared, the zinc bolus significantly increased the ratio (P < 0·001) and serum caeruloplasmin (P < 0·001) and erythrocyte superoxide dismutase (P < 0·01) activities. These responses were not observed in trial 2 with the erythrocyte superoxide dismutase being significantly reduced in the zinc group when compared with the control group (P < 0·001).

The zinc, cobalt and selenium soluble glass bolus increased the status of all three trace elements consistently for a period of at least 100 days. The increases of cobalt and selenium status were similar to those achieved using the copper, cobalt and selenium bolus, which also increased the copper status of the sheep.

In order to establish the response of dairy cow performance to concentrate supplementation in contrasting grazing conditions and for cows differing in milk yield at turn-out, three experiments were conducted. Each year, two levels of herbage allowance were studied in interaction with four (experiment 1) or three (experiments 2 and 3) levels of concentrate on two groups of 30 to 40 mid-lactation Holstein cows producing between 20 and 46 kg milk at turnout. Amount of concentrate and herbage allowance ranged from 0 to 6 kg fresh weight and from 12 to 22 kg dry matter (DM) per cow per day respectively. The supplementation led to average responses, per kg DM concentrate, of 104 kg milk, +66 g/day body-weight gain, +0·19 g/kg milk protein and -0·57 g/kg milk fat. These responses remained linear up to 4 or 6 kg according to the years and treatments. The response to the concentrate did not vary with the milk yield or composition at turn-out. The increase in the herbage allowance from 12 to 16 kg DM per cow per day (experiment 1) improved milk yield (+1·2 kg/day) and milk protein (+0·7 g/kg) while the increase from 16 to 22 kg DM (experiments 2 and 3) had less effect (+0·5 kg/day milk yield and +0·4 g/kg milk protein). There was no clear interaction between concentrate supplementation and herbage allowance. Under the usual conditions of spring pasture, with cows in mid lactation, the use of a constant level of concentrate at grazing proves to be a technique of some interest.

Two experiments were conducted in which growing sheep were given choices between foods differing in their contents of urea. The crude protein (CP) contents of both of the foods of the pair were also varied. The hypothesis tested was that the diets selected would be those that met the effective rumen degradable protein (eRDP) requirements of the animals and would avoid excess consumption of eRDP. Three basal foods, differing in CP were formulated. D was designed to be deficient in CP with 80 g CP and 58 g eRDP per kg DM; H was calculated to be adequate with 159 g CP and 114 g eRDP per kg DM; P had excess with 210 g CP and 148 g eRDP per kg DM. Other foods were made by adding 12·5 or 25 g urea per kg fresh matter to each of the three basal foods to make a further six foods. In both experiments Texel ✕ Greyface female sheep were used. In experiment 1, 34 sheep weighing 37·2 (s.d. 1·85) kg were randomly allocated to one of six groups and each group was offered a choice between a pair of foods. Groups 1 to 3 were offered pairs in the D series (D v. D + 12·5 g urea per kg (no. = 6), D v. D + 25 g urea per kg (no. = 6) and D + 12·5 g urea per kg v. D + 25 g urea per kg (no. = 5)). Groups 4 to 6 were offered the same pairs of foods but with H instead of D. In experiment 2, 96 sheep weighing 29·8 (s.d. 3·37) kg were randomly allocated to one of 12 groups. Groups 1 to 6 (no. = 6) were allocated a single food (D, D + 25 g, H, H + 25 g, P or P + 25 g urea per kg) throughout the experiment. Groups 7 to 12 were given a choice (no. = 10) between two foods. One food of the pair was the basal D, H or P. The other food was the same basal food supplemented with either 12·5 or 25 g urea per kg. On the single foods adding urea to D resulted in an increase in food intake and live-weight gain suggesting that D was deficient in eRDP. Adding urea to either H or P had no beneficial effects on intake or live-weight gain. This suggests that both contained sufficient eRDP in relation to energy. Across all choice treatments in both experiments there was a highly significant preference (P < 0·01) for the food with the higher urea content. In experiment 1 0·62 (s.e. 0·04) of the diet selected was the food with the higher urea content. In experiment 2 the figure was 0·64 (s.e.0·03). The general preference for the food with the higher urea content was unaffected by the CP contents of the foods used. The results do not support the hypothesis that sheep will avoid excess eRDP when given a choice and suggest that eRDP may not be a relevant dimension in diet selection in the conditions of these experiments.