A model has been developed to predict the true metabolizable energy (ME,) concentration in forages given to ruminants.

The chemical description of forages is based on the concentrations of ash, crude protein, ether extract, sugars and α-glycans, β-glycans and lignin, volatile fatty acids and lactic acid. The model assumes complete fermentation of sugars, α-glycans and lactic acid. The extent of fermentation of β-glycans and crude protein is determined in part by rumen solid-phase outflow rate, which can itself be predicted from dry-matter intake.

The model was tested using 121 graminaceous forages whose chemical composition and concentration of metabolizable energy had been measured in the Feedingstuffs Evaluation Unit at the Rowett Research Institute. The agreement between observed and predicted ME, for all classes of forage was nearly always as good as, or better than, the best prediction from single attributes of food chemistry which could only be determined retrospectively and were not consistent even within classes of forage. The model predicts a decline in ME, with increasing rumen solid-phase outflow rate which is determined mainly by the extent of fermentation of β-glycans.

An experiment was carried out with 20 male veal calves to study differences in energy metabolism between pure Dutch Friesian and Holstein Friesian crossbred calves, containing a high proportion of Holstein Friesian genes (0·79). Two metabolizable energy (ME) intakes were given. The effects of genotype and ME intake on live-weight gain and its fat and protein composition were measured by indirect calorimetry and by the total collection of faeces and urine. Energy and nitrogen balances were measured for each calf during the last 5 weeks of the fattening period of 22 weeks.

The difference in live-weight gain between the Holstein Friesian crossbreds and the Dutch Friesian calves was not significant but small differences in protein and fat composition of live-weight gain were found. Fat gain was closely related to ME intake (r = 0·95), but the correlation coefficient between ME intake and protein gain was only 0-36. Live-weight gain had a high correlation with protein gain (r = 0·70) but a lower correlation with fat gain (r = 0·29).

Veal calves at the end of the fattening period had a declining protein gain as age increased. Calves given a high ME intake (> 2 × maintenance) may require diets containing less than 216 g crude protein per kg diet at the end of the fattening period.

The study indicates that Holstein Friesian crossbred veal calves and Dutch Friesian veal calves have similar ME requirements.

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.

Two experiments were conducted with weaned, suckled calves to investigate the effect of feeding level during the post-weaning winter on their subsequent performance when continuously grazed on pasture maintained at two sward heights. Low, medium and high levels of winter feeding resulted in winter live-weight gains of 0·31, 0·58 and 0·79 (s.e. 0·027) kg/day (P < 0·001) during the 152-day winter in experiment 1 and 0·44, 0·69 and 0·84 (s.e. 0·029) kg/day (P < 0·001) for 189 days in experiment 2. During summer (93 days in experiment 1 and 87 days in experiment 2) there was a significant effect of winter food level on performance when live-weight gains were 1·10, 1·02, 0·87 and 1·35, 1·23 and 1·19 (s.e. 0·060) kg/day for the low, medium and high winter food levels on the short and tall swards respectively in experiment 1 (P < 0·01) and 0·86, 0·66, 0·51 and 1·26, 1·18 and 0·91 (s.e. 0090) kg/day in experiment 2 (P < 0·001). The cattle showing compensatory growth had higher herbage intakes and it is postulated that this occurred because of a negative association between body fat and herbage intake. Sward height had a large positive effect on herbage intake and live-weight gain and it is concluded that for maximum intake on ryegrass swards, herbage height should be at least 8 cm. Lower levels of winter live-weight gain delayed the time to slaughter, but allowed cattle to achieve heavier carcass weights at a fixed level of fatness.

It is concluded that there is no single optimum winter food level for weaned, suckled calves but that the choice will depend upon several factors, including availability of winter and summer food resources, the length of the winter feeding period, the desired date of slaughter and type of carcass to be produced.

Between six and 11 twin pairs each of the breeds Braunvieh (BV), Fleckvieh (FV), Grauvieh (GV), Pinzgauer (Pi) and Friesians (Fr) were either treated uniformly or separated and fattened to veal or to yearling bull stage. The aim of the experiment was the comparison of Central European breeds and to investigate genotype × rearing system interaction both within and between breeds. Veal calves were slaughtered at about 120 to 150 kg live weight (proportionately about 0·13 of estimated mature weight of bulls) and yearling bulls at 410 to 460 kg live weight, corresponding to proportionately 0·38 of estimated mature weight. In general, the dual-purpose breeds had higher growth rates both absolute (AGR) and relative (RGR) and better food conversion ratios (FCR) than the dairy breed, Friesian, and this was true irrespective of whether correlations were made to constant age, weight, maturity (equal proportion of adult weight) or carcass fatness. However, the early-weaned Friesian calves grew fastest in the early phase of the growing period and this probably reflected their superior appetite.

Interactions between breeds and rearing system (bull v. veal) were significant for RGR and for maturity-corrected FCR which was mainly caused by shifting of the positions of BV and Pi.

The pooled genetic correlations between performance in the different fattening categories were considerably below unity. The twin-pair correlations indicated high heritabilities which are biased by contributions from dominance and maternal environment. While in data corrected to comparable maturity, AGR and RGR were highly positively correlated, their correlation became negative in agecorrected data. The correlations with FCR displayed an equivalent change with sign reversed. The correlations between wither height and heart girth with AGR were positive for age-corrected data but negative or barely positive, respectively, for data corrected to equal maturity. Again, FCR behaved similarly but with sign reversed.

Sibs of five to 11 twin pairs each of five breeds were either slaughtered as veal or as yearling bulls. Highly significant breed differences were evident in the carcass tissue proportions which could be explained on the basis of differences in the physiology of dairy and dual-purpose animals, the former depositing more fat and more bone than dual-purpose breeds. Among the dual-purpose breeds the carcasses of the Pinzgauer (Pi) tended to rank between the carcasses of the Fleckvieh (FV), Braunvieh (BV), Grauvieh (GV) and those of the Friesian (Fr).

The dual-purpose breeds FV, BV, GV had more meat in the hindquarter and in the shoulder than the FR while these in turn had more meat in the brisket and in the flank and shank muscles. Again the Pi group tended to rank between the aforementioned groups.

Within breeds, large differences between twin pairs indicated high heritabilities for carcass tissue proportions and ratios. The heritability of commercial cut proportions was fairly high but the genetic variance was small, the genetic coefficient of variation being less than 0-02. The different degrees of sexual maturity and of carcass maturity also caused differences in the distribution of meat in the carcasses of young male animals.

Significant mean squares for interactions between treatments and breeds, and genetic correlations of less than unity between performance of twin genotypes in veal and in bulls, indicated age and/or rearing system by genotype interactions between and within breeds for various slaughter traits.

Phenotypic correlations between various slaughter traits were low except where part-whole relationships were involved. It is suggested that slaughter at comparable maturity in the respective treatments was the cause of the weak connection between the traits.

Attributes of lactation and weight of components of the empty body were analysed to evaluate relationships between performance potential of various breeds or breed crosses and the proportion of empty-body components relative to slaughter weight. Differences in major internal organs attributable to breed, breed cross, level of food intake, mature body size and milk production potential were observed. Milk yield was positively related to proportion of lung tissue, tended to be positively related to head and liver tissues but was negatively related to the proportion of warm carcass. As estimated from a three breed diallel, significant additive breed direct effects were observed for several empty-body components. In general, heterosis tended to be non-significant for all proportions of body components with the exception of proportion of head, fore and hind feet and lung tissue. Breed crosses characterized as having greater potential for mature weight were heavier at slaughter and had a greater proportion of structural components such as head, hide and fore and hind feet. Differences among visceral organs associated with production potential for size and milk production are discussed relative to the possible effect on basal energy expenditure and the effect these differences may have on the energy requirements for a cow/calf livestock enterprise.

The reproductive performance of female Magra and Marwari sheep of the desert areas of north-western India was studied in relation to intermittent water deprivation, for a period of 39 months during which four breedings were completed. The control group received an ad libitum supply of water every day, while the water-restricted group was provided with water on the same 2 days each week only throughout the experimental period, except during the monsoon season. All the ewes were maintained on cultivated Cenchrus ciliaris pasture. No ill effect was noticed on the general health of the animals. Reproductive measures such as incidence and duration of oestrus, length of the oestrous cycle, conception rate, lambing rate, length of gestation, post-partum interval, inter-lambing period, post-lambing weight of ewes and birth weight of lambs were not significantly affected by the imposed water deprivation. The dailywatered ewes had a slightly, but not significantly higher gain in body weight than the water-restricted ewes. It wa^ concluded that ewes of these two breeds could be maintained on a twice weekly watering schedule for prolonged periods of time without having any adverse effect on their reproductive performance.

The dry-matter degradation of 19 varieties of barley, 14 varieties of wheat, 11 varieties of oats and one variety of triticale straws, both untreated and ammonia treated were studied using the nylon-bag technique. There were significant differences between the untreated varieties of all the types of cereal straw studied with respect to dry-matter loss (DML) values. When the barley and wheat straws were treated with ammonia, the differences between the varieties were also significant although ammonia treatment tended to improve those with lower values to a greater extent than those with higher values. There were also significant differences between the DML values of the oat straws when they were treated with ammonia but only after 48-h incubation. There was a significant negative relationship between the 48-h DML values of the untreated oat straws and the improvement in the DML values with ammonia treatment (r = −0·65; P < 0·05). Grain yield, straw length and nitrogen concentration had no significant relationship with the DML values of the untreated straws. Barley and oat straws had generally higher DML than the wheat and triticale straws.

Two varieties of barley straw, Corgi and Gerbel, which varied in degradability when incubated in the rumen in nylon bags, were chosen for further examination of botanical fractions and to see how each fraction responded to treatment with ammonia. The straws were separated into leaves, internodes, nodes and chaff. The average proportions of these fractions were respectively 0·499, 0·380, 0·055 and 0·065 in Corgi straw and 0·404, 0·512, 0·059 and 0·025 in Gerbel straw. For both varieties the degradability of the botanical fractions were leaves > chaff > nodes > internodes.

Despite a similar chemical composition, the dry-matter loss (DML) values of leaves, internodes and nodes of Corgi were higher than those of Gerbel straw.

The differences between varieties were larger for internodes and nodes than for leaves. The difference in DML of the two varieties at 48-h incubation was 132 g/kg DM. Of this difference, 25 g were due to differences in distribution of the botanical fractions and 107 g to differences in DML of the fractions.

Ammonia treatment significantly increased the DML of all fractions except the nodes. The overall improvement due to ammonia treatment of the different fraction was internode > chaff > leaves > nodes.

On a hill farm, the reproductive performance of Scottish Blackface ewes increases annually with increasing age up to 6 years and is positively related to pre-mating live weight. A group of Scottish Blackface ewe lambs was, from 5 months of age, preferentially managed over a 2-year period to accelerate the achievement of mature size, in order to study the relative importance of age and size to reproductive performance. Ovulation rate and early embryo mortality of these ewes at 31 months of age were compared with those of adult ewes of similar body size and condition at 79 months of age which had been reared conventionally in the same hill flock. Two comparisons were made, one between different age groups in the same year and the other retrospectively between different ages of the same age group. In the first comparison, the adult ewes had a slightly greater reproductive response which suggested a small effect of age per se but there was also the possibility of a genetic difference. In the second comparison, there was no difference in ovulation rate or potential lambing rate per pregnant ewe, but a trend towards greater wastage of twin-shed ova in the heavier and fatter younger ewes again suggested a small effect of age. At both ages, however, these ewes performed close to their adult genetic potential which suggested that the treatment of the young ewes was sufficient to overcome most of the limitations associated with age or size. Reproductive performance normally associated with young animals is therefore mainly an expression of their size relative to their maturity and the removal of the size limitation by higher levels of nutrition and more rapid growth can largely eliminate their poorer performance.

Border Leicester × Scottish Blackface (Greyface) ewes of three groups, each comprising 118 animals in a wide range of body condition scores, were mated at a synchronized oestrus in mid October. The ewes were passively immunized against testosterone (group P), actively immunized against androstenedione (group F), or not treated (group C). All ewes were slaughtered at return to service or at 35 to 45 days of pregnancy and ovulation rates and numbers of embryos present were determined. Mean ovulation rates of ewes in group P were higher than in those in group C (P < 0·05) and this difference was evident at most levels of body condition. The absolute increase in ovulation rate, compared with the control group, was similar at all condition scores. Mean ovulation rates of ewes in group F were higher than those in group C (P < 0·001) and the magnitude of the increase was greater in ewes in higher condition scores. The incidence of ova wastage was variable but differences between treatments in mean ovulation rate were generally reflected in mean litter size. The conception rates of immunized ewes were depressed compared with those of control animals, particularly in ewes with a body condition score less than 3·0 at mating. Consequently, there was no improvement in the potential lambing rate of immunized ewes following only one cycle of mating. Circulating antibody titres were not related to conception rate or body condition at mating and were related to ovulation rate only in group F ewes. It is concluded that immunization against steroids, using either passive or active techniques, can improve the reproductive performance of individual ewes but improvement in the performance of the flock as a whole may only be achieved under optimal conditions of nutrition and season.

Mortality and its causes were studied during two consecutive years in a total of 934 lambs. The lambs were from two lines of sheep genetically selected for low (L) and high (H) concentrations of copper (Cu) in plasma within an interbred Scottish Blackface × Welsh Mountain population and from unselected Scottish Blackface (B) and Welsh Mountain (W) breeds. The lambs grazed improved hill pastures. Half of the lambs in each line or breed were given an oral Cu supplement by 7·5 weeks of age.

Mortality from birth to 24 weeks in H was less than half that in L; mean proportional mortalities were L 0·28, H 0·12, B 0·37 and W 0·07, with a similar distribution in each year. Swayback accounted proportionately for 0·26 deaths in year 1, but proportionately for only 0·02 in year 2. The majority of other losses involved a variety of microbial infections.

Genetic type (W < H < L < B) was a major determinant of, and Cu supplementation a protection against, swayback and non-swayback losses. For non-swayback losses L lambs were about twice (P < 0·01) and B lambs about four times (P < 0·001) more vulnerable than H and W lambs respectively. Unsupplemented lambs were more than twice as vulnerable to non-swayback causes of death in the 1st year (P < 0·05) and four times as vulnerable in the 2nd year (P < 0·01) as were Cu-supplemented lambs. There were no cases of swayback in supplemented lambs even though Cu treatment was in some lambs as late as 7·5 weeks after birth.

Such marked differences in mortality rate, particularly between the selected lines, had not been apparent in the 5 years preceding pasture improvement, suggesting a genotype × environment interaction affecting survival.

The results provide the first definitive evidence that decreased resistance to infection is a clinical consequence of ovine Cu deficiency in the field, amenable to control by Cu treatment and genetic selection.

Growth rate and the concentrations of various biochemical constituents were measured in 2 years in lambs from two lines, selected on low (L) and high (H) copper (Cu) concentrations in plasma, and from two unselected pure breeds, Scottish Blackface (B) and Welsh Mountain (W). The lambs grazed improved hill pastures and half were given Cu supplements.

H lambs were always heavier and were fattened for slaughter earlier than were L lambs, differences that were not completely eliminated when supplementary Cu was given. In both years, the improvements in growth rate due to supplementary Cu varied with genetic type (average L 20·5 (s.e. 2·5); H 5·7 (s.e. 2·6); B 25·1 (s.e. 3·7); W 8·1 (s.e. 3·3) g/day). Growth rates of supplemented lambs were L 100 (s.e. 2), H 104 (s.e. 2), B 134 (s.e. 5), W 103 (s.e. 3) g/day.

At 6 weeks of age, unsupplemented lambs trom all genetic types were hypocupraemic and, at all ages, unsupplemented L and B lambs had lower concentrations of Cu in plasma and superoxide dismutase (SOD) activity than had unsupplemented H and W lambs. Supplemented lambs always had greater concentrations of Cu in plasma and SOD activities than had their unsupplemented counterparts. Supplementation increased the haemoglobin concentration for B (in year 2) and L lambs but not for H and W lambs. Cholesterol concentrations in plasma were unaffected by selection but were slightly higher in unsupplemented lambs. The concentration of total protein and the activity of aspartate transaminase were unaffected by genotype or Cu supplementation. In the liver of lambs at slaughter, the concentration of Cu was lower for unsupplemented lambs and inversely related to the concentration of iron.

It was concluded that (i) genotype was an important determinant of hypocuprosis; (ii) the degree of hypocuprosis could not be predicted from herbage analyses alone, but instead may be predicted from biochemical assessment of the lamb; and (iii) the dose of Cu supplement used was inadequate for L and B lambs and recommended levels could be increased, within limits, without risk of toxicity.

Eighty-eight first-litter sows were used in a factorial experiment to examine the effects of energy and protein intakes during lactation on subsequent performance. Some received either 45 MJ (E,) or 60 to 63 MJ (E2) digestible energy per day and either 508 to 511 (P,) or 703 to 815 (P2) g crude protein per day during a 28-day lactation.

Sows on the E2P2 treatment lost less body weight during lactation than sows on the other three treatments (P < 0·05). Average live-weight losses during lactation were 21·8, 20·8, 17·8 and 9·6 kg for the E1P1, E1P2, E2P1, and E2P2 sows, respectively. The corresponding reductions in backfat measurements during lactation were 5·5, 7·9, 3·2 and 4·0 mm. Backfat losses were greater for sows given either moderate energy intakes or high protein intakes (P < 0·01).

Neither protein intake nor energy intake during lactation affected subsequent ovulation rate, but piglets sucking sows given high protein intakes grew faster, particularly during the last week of lactation, than piglets sucking sows receiving low protein intakes (P < 0·05).

Within 8 days of weaning, more sows given high intakes of protein during lactation exhibited oestrus than did sows which received lower intakes of protein (27/44 v. 14/44, x2 = 7·7, P < 0·01). Protein intake during lactation affected the nitrogen balance of sows in a similar way. The nitrogen balances were estimated during the 3rd week of lactation, and for sows given rations E1P1, E1P2, E2P1, and E2P2were -20·2, -11·5, -17·5 and -7·2 g/day respectively.

Ninety entire male pigs were used in two experiments to investigate the effects of energy concentration on the performance of growing pigs given diets containing relatively high or low levels of fibre. A blended fat product was also compared with tallow as a source of dietary energy for pigs in the first experiment.

In experiment 1, 60 pigs growing between 20 and 45 kg live weight were given 10 diets containing approximately 120 g acid-detergent fibre per kg (80 g crude fibre per kg), and 10, 30, 50, 75 or 100 g/kg of either tallow or the blended fat product.

Although the source of fat had no significant effect on food intake or growth performance, voluntary energy intake and growth rate increased with increase in the level of fat added to the diet and with concomitant increase in dietary digestible energy (DE) concentration up to 50 g/kg and 13·2 MJ/kg respectively. Further increase in the level of fat added to the diet and in DE concentration resulted in a decline in voluntary food intake, whilst energy intake and growth rate remained relatively constant at 27 MJ/day and 720 g/day respectively.

In experiment 2, 30 pigs were used to investigate the animals' response to five levels of dietary DE concentration (11·8 to 15·1 MJ DE per kg) between 20 and 50 kg live weight. The highest level of acid-detergent fibre in the diets was 62 g/kg (50 g crude fibre per kg) and this declined with increase in energy concentration to 30 g/kg (25 g crude fibre per kg) in the diet of highest energy concentration.

Voluntary food intake was not significantly affected by dietary energy concentration, and voluntary energy intake and growth rate increased linearly with increase in dietary energy concentration up to 14·5 MJ DE per kg. Maximum energy intake (31 MJ DE per day) and growth rate (905 g/day) in experiment 2 was proportionately 0·15 and 0·26 higher than that achieved by pigs given the higher fibre diets in experiment 1.

The results for voluntary food intake and growth rate suggested that the pig's demand for energy and consequently its response to dietary energy concentration was affected by dietary fibre concentration.

The number of beta-adrenergic receptors which influence the effectiveness of catecholamines was determined by 3H-dihydro-alprenolol in muscle, heart and fat tissue of stress-susceptible pigs (Pietrains) and non-susceptible pigs (Large Whites). In all investigated tissues proportionately 0·31 to 0·38 more receptors were found in the Pietrains than in the Large Whites, the differences being significant (P < 0·05). That the higher numbers of beta-adrenergic receptors in Pietrain pigs may be involved in accelerated muscle glycogenolysis (poor meat quality) and increased lipolysis (low carcass fat) in these animals and in other breds showing poor meat quality and low carcass fat is discussed.

Forty-eight Landrace × (Landrace × Large White) gilts were randomly allocated at 70 days of age to each of three rearing treatments: (1) fence-line contact with a mature boar, (2) olfactory/aural contact with a mature boar, (3) no boar contact. At 160 days of age, all gilts were relocated adjacent to a novel mature boar and exposed to full contact with a mature boar for 30 min each day. At the first, second and third oestrus, 16 gilts from each treatment group were mated twice and the reproductive tracts were examined at slaughter 21 days later, to determine ovulation rate and embryo survival. The rearing treatments had no significant effects on the attainment of puberty. Neither rearing treatment nor oestrus of mating had any significant effect on behaviour, sexual receptivity at first service, conception rate, ovulation rate, the number of embryos and embryo survival at 21 days of pregnancy.

Sugar-beet pulp as normally produced in Great Britain contains about 400 g molasses per kg dry matter (DM). It has been demonstrated that either a reduction in the amount or even the full removal of the molasses did not affect the yield or composition of the milk of cows (e.g. Ronning and Bath, 1962; Hemingway, Parkins and Fraser, 1986). The dried, shredded pulp without molasses was, however, generally less palatable.