Two experiments were conducted in successive years with, respectively, 112 and 194 mature Scottish Blackface ewes to study the effects of shearing during pregnancy on lamb birth weight and subsequent growth. In each year half the ewes were shorn approx. 10 weeks before lambing. Shorn and unshorn ewes were offered and consumed equal quantities of food.

In both years the shorn ewes lost approx. 2 kg of live weight shortly after shearing (making allowance for the weight of wool removed); thereafter live-weight differences remained relatively constant. Plasma 3-hydroxybutyrate concentrations indicated that the initial live-weight loss was probably attributable to short-term increases in heat production and energy expenditure.

Respiration rates and rectal temperatures of unshorn ewes were always higher than in shorn ewes, but were not elevated to an extent indicative of heat stress.

Shearing had no effect on the birth weights of single or twin lambs, nor was there any effect on lamb growth rate to 14 weeks of age.

It is postulated that the effects of shearing on lamb birth weight reported by others working with sheep fed ad libitum are most likely to be due to the increased voluntary food intakes of shorn ewes.

In an experiment designed to investigate the effects on the growth and voluntary food intake of grass silage by calves, the silage was supplemented with varying levels of fish meal and sucrose. The grass silage had a pH of 3·6, a lactic acid content of 90·0 g/kg dry matter (DM) and total nitrogen content of 15·5 g/kg DM. Supplements of 50, 75 and 100 g fish meal per kg silage DM and 50, 75, 100 and 150 g sucrose per kg silage DM were mixed with the silage just prior to feeding. The eight diets were offered to 32, 4-month-old British Friesian steers for 12, 7-day periods. Intake was recorded daily and live weight weekly.

Digestibility of organic matter (P < 0·05) and N (P < 0·001) were increased by fish-meal supplementation but the effect of level of fish meal was not significant. Sucrose supplementation significantly decreased both N (P < 0·01) and cellulose (P < 0·05) digestibility. The effect on cellulose digestibility increased with level of sucrose (P < 0·01).

The intake of silage DM increased in response to increasing level of fish-meal inclusion when intake was expressed in terms of kg/day (P < 0·01) but not when expressed in g/kg live weight. Total DM intake showed a significant (P < 0·001) linear response when expressed both in terms of kg/day and g/kg live weight. The intake of silage DM declined in response to increased level of sucrose supplementation both in absolute (P < 0·05) and live-weight terms (P < 0·001) but sucrose supplementation had no significant effect on total intake.

Live-weight gain was significantly increased with increasing level of fish-meal supplementation (P < 0·001), but sucrose supplementation had a significant effect on live-weight gain relative to the control treatment at only the 75 g/kg level, where live-weight gain was increased.

Forty male commercial hybrid pigs, half castrated at 10 days of age, were used in a study to determine whether boars at bacon weight (90 kg live weight) have different fat quality from barrows. Fat quality was defined as the firmness and cohesiveness of subcutaneous fat, both properties being measured using an Instron materials testing instrument. Within each group of boars and barrows, half the pigs were fed a normal commercial diet and half a lower energy diet at a lower level of food intake. The latter diet provided relatively more energy as C18:2 (linoleic acid).

Firmness of subcutaneous fat was related to fat thickness and to concentrations of the chemical components in the fat which are affected by fat thickness. The single best predictor of firmness was C18:0 (stearic acid). Cohesiveness was less closely related to fat thickness and was most associated with the concentration of C18:2.

On the low energy/high C18:2 diet, all the pigs were judged to have soft fat, the difference between boars and barrows being small and explained by the difference in fat thickness. On the normal commercial diet, some barrows had particularly firm fat but they had thicker fat than any of the boars. Most (0·84) of the pigs in the experiment had P2 values (fat thickness over the m. longissimus at the last rib) between 8 and 15 mm. In this range there was no difference in firmness between boars and barrows. Cohesiveness was also similar between boars and barrows.

Changes in the pattern of food intake, food conversion efficiency and growth from weaning to maturity, were examined in 35 rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. The sheep were individually fed a pelleted ration ad libitum for at least 72 weeks and up to 90 weeks post weaning. Weekly food intake was described as an increasing exponential function of age with a linearly declining asymptote, about which a regular oscillation occurred, and weekly body-weight gain was described as an increasing exponential function of weekly food intake, about which a regular oscillation also occurred.

The oscillations in weekly food intake had a period of about 52 weeks and appeared to be largely associated with seasonal variations in temperature, with an increased food intake during winter and a decreased food intake during summer. The oscillations in both the food-intake and body-weight functions were of similar phase and period and it was suggested that the body-weight oscillations were due to variation in gut-fill, a result of the seasonal oscillations in food intake.

Selection for weaning weight changed the shape and magnitude of the food-intake curve, with the weight-plus having a greater rate of food intake (i.e. appetite) in the early stages of growth and a greater asymptote than the weight-minus animals. Selection for high and low weaning weight also resulted in an increase and a decrease in mature weight. Both strains had a similar growth efficiency, although when calculated as gross food conversion efficiency the weight-plus were higher than the weight-minus animals at the same body weight, whereas there was no difference between strains at the same age.

The rams had both a higher asymptote and a slower rate of decline in food intake than the ewes. Rams had a higher mature weight than the ewes, although ewes had a slightly greater growth efficiency. However, when calculated as gross food conversion efficiency, ewes tended to be lower than rams, when compared either at the same age, or at the same body weight.

When the food-intake curves were standardized for differences in mature size, strain differences in the magnitude of the food-intake curves were reduced, although differences in the shape were still apparent. Shape differences in the food-intake curves were reflected in the shape of the standardized growth curves, with the weight-plus maturing at a faster rate than the weight-minus animals. There was little difference between the sexes in the initial shape of the food-intake curve, although at later ages ewes had a lower food intake than rams. There was little difference between the sexes in the shape of the standardized growth curves.

The changes in chemical and dissectible body composition from birth to maturity were examined in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock. Body composition was examined in 34 mature animals and the maturing patterns for body components calculated using mean values from the mature animals and individual data from 106 immature animals.

In the 34 mature animals, strain had no effect on the proportions of chemical and dissected fat, protein and muscle in the body. The weight-plus had greater proportions of ash and carcass bone in the body than the weight-minus animals. Mature rams had lower proportions of chemical and dissected fat and greater proportions of protein, muscle, ash and carcass bone in the body than mature ewes.

The weight-minus animals had later maturing patterns for both chemical and dissected fat than the weight-plus animals. Strain had no effect on the maturing patterns for protein and muscle, although both ash and carcass bone were later maturing in the weight-plus, than in the weight-minus animals. Chemical and dissected fat were later maturing in the ewes than in the rams, whereas protein, muscle, ash and carcass bone were earlier maturing in the ewes than in the rams.

The weight-minus animals were fatter at the heavier body weights, although there was a trend for the weight-plus animals to be slightly fatter at the lighter body weights. When compared at the same stage of maturity of body weight, strain differences in the proportion of fat in the body declined as the animals matured. Compositional differences between the rams and ewes varied according to the body weight or stage of maturity of body weight at which they were compared.

One hundred entire male pigs growing between 20 and 45 kg live weight were used to investigate the effects on growth performance and carcass composition of eight concentrations of dietary crude protein (CP), ranging from 93 to 238 g/kg and three levels of food intake (giving mean daily digestible energy 15·6, 18·7 and 22·4 MJ).

Growth rate improved with each increase in food intake and with increase in dietary CP up to 175 g/kg (10·5 g lysine per kg) at all food intakes. Food:gain ratio (g food per g growth) improved with increase in dietary CP up to 175 g/kg and with the first increase in food intake.

The rate of protein deposition in the carcass (excluding viscera) increased with each increase in level of feeding, and with increases in dietary CP up to 175 g/kg. The results showed that for pigs given diets deficient in protein, the rate of protein deposition was linearly related to protein intake and independent of energy intake. For pigs given diets adequate in protein, the rate of protein deposition was related to energy intake, and independent of protein intake.

The carcass fat of pigs killed at 45 kg live weight decreased on all feeding treatments with increase in dietary CP up to 175 g/kg, and was higher in pigs given the two higher levels of feeding than in those fed at the lowest level. The effect of feeding level on carcass fat content declined as the protein adequacy of the diet was reduced.

Silage cut twice annually (June and August) from a tetraploid red clover/grass sward and three times annually (May, July and September) from a low nitrogen (N) and high N perennial ryegrass/white clover sward was fed in proportion to dry-matter yield from each cut, over a 10-week period, each winter for 3 years to castrated male cattle of initial live weight 401 kg in year 1 and 425 kg in years 2 and 3. The silages were supplemented with 0, 1, 2 and 3 kg concentrate per head daily.

Total dry-matter yield from the red clover/grass sward was similar to that from the perennial ryegrass/white clover sward (high N grass) receiving 360 kg N per ha but the digestibility, particularly of first cut material was much lower. Dry-matter production of the low N grass/white clover sward was 0·73 of high N grass sward and produced silages of similar digestibility and fermentation.

Dry-matter intakes by the cattle were higher on the legume-based silages in years when clover made a worthwhile contribution to total yield, but this did not significantly improve utilization or animal performance compared with high N grass silage. Mean daily carcass gain per head on red clover/grass silage was 0·41 kg which was significantly less than the 0·61 kg on white clover/grass silage and 0·59 on high N grass (P < 0·001). Carcass output from red clover/grass silage was 618 kg/ha and 629 kg/ha from white clover/grass, both of which were significantly less than the 863 kg/ha from the high N grass silage (P < 0·001). Dressing proportion was also significantly poorer in animals fed red clover/grass silage compared with the other silage types.

A study was made of the growth of Holstein Friesian females in an intensive production system in the Venezuelan tropics, using monthly weights from birth (no. = 922) up to 72 months of age (no. = 63). Birth weights were adjusted for age of dam, month and year of birth of heifer, whereas subsequent weights were adjusted for birth weight and month and year of birth. Despite lower weights at birth (mean = 35·9 kg), live weights were comparable to the Beltsville standard for the breed up to 12 months of age. However, at 24, 36, 48 and 72 months of age the weights observed only reached 0·84, 0·77, 0·75, 0·79 and 0·78, respectively, of the Beltsville standard. No effect was observed on birth weight of age of dam, month or year of birth, but birth weight affected subsequent weights (P < 0·001) and the effects of month and year of birth on live weight were significant at most ages. The poor quality of the forage consumed and stress due to high environmental temperatures and humidity appear to be the main reasons for the reduced growth rates. Von Bertalanffy's model gave a higher residual error than a polynomial model when fitted to the data, but resulted in a curve which agreed more closely with the conventional biological growth pattern.

Twenty four entire male and 24 female pigs growing from 48 to 90 kg live weight were used to investigate the effects of five rates of food intake supplying daily between 23 MJ digestible energy (DE) and 41·8 or 39·2 MJ DE for entire males and females respectively, on rate of protein deposition, and on growth and body composition.

Entire males deposited protein faster than females, and for both sexes the rate of protein deposition increased linearly with increase in energy intake up to 33 MJ DE per day (P < 0·001) but was not significantly affected by further increase in energy intake.

Average daily gain increased quadratically (P < 0·001) with increase in energy intake and at all levels was higher for entire males than for females. Food:gain ratio (g food per g growth) which was lower for entire males improved with increase in energy intake up to 33 MJ DE per day and deteriorated with further increase in energy intake.

At 90 kg live weight entire males contained less fat and more protein and water in the empty body than females. For both sexes, body fat content increased at a decreasing rate with increase in energy intake up to 33 MJ DE per day, and at an increasing rate with further increase in energy intake.

Total energy retained was linearly (P < 0·001) related to energy intake and at all rates of energy intake was higher for females than for entire males. The estimates of DE required for maintenance were 15·9 MJ/day (0·664 MJ/kg M0·75 per day) and 12·4 MJ/day (0·51 MJ/kg M0·75 per day) for entire males and females, respectively.

Using a simplified energy balance equation, changes in energetic efficiency and energy expenditure were examined as a function of stage of maturity in rams and ewes from flocks of Merino sheep selected for high (weight-plus) and low (weight-minus) weaning weight and from a randomly bred control flock.

Specific combustion energy of the body (i.e. MJ/kg of body weight) was an increasing linear function of stage of maturity, which increased at a slightly faster rate in the weight-minus than in the weight-plus animals (15·1 v. 13·1 MJ/kg per unit of maturity), and at a faster rate in ewes than in rams (17·2 v. 11·3 MJ/kg per unit of maturity). At maturity, all strains had a similar mean specific combustion energy (18·3 MJ/kg), whereas the ewes were greater than the rams (20·1 v. 16·6 MJ/kg).

Thermochemical efficiency (TCE, defined as the gain in body energy per unit of metabolizable energy intake) was a quadratic function of stage of maturity. In the early post-weaning period, the weight-plus had a greater TCE than the weight-minus animals and the maximum TCE occurred at an earlier stage of maturity in the weight-plus than in the weight-minus animals (0·40 v. 0·45 maturity). The ewes had a higher TCE than the rams at all stages of maturity, although the differences decreased as the animals matured. The maximum TCE occurred at a later stage of maturity in the ewes than in the rams (0·46 v. 0·38 maturity).

After scaling for differences in mature size there was little difference between the strains in the rate of energy expenditure, with the exception that at the later stages of maturity the weight-minus animals had a slightly greater rate of energy expenditure. After scaling for differences in mature size, the rams had a greater rate of energy expenditure than the ewes from weaning to maturity.

Over a period of 3 years, silages subjected to various mechanical treatments by the use of conventional silage harvesters were offered ad libitum to pregnant ewes and to castrated male lambs and the effects on intake and productivity were measured. The intake of silage made from grass harvested with a precision-chop harvester was substantially greater than the intake of silage made with other types of harvester (especially, a flail harvester), causing a lower degree of comminution.

Mean daily silage dry-matter intake of ewes was 0·99 kg and 1·28 kg in mid-pregnancy, and 0·85 kg and 1·10 kg in late pregnancy with flail-harvested and precision-chop silages respectively. Silage was supplemented with various levels of concentrate in late pregnancy and an increasing level of concentrates did not reduce silage intake. In early lactation, when 800 g concentrate was given daily, ewes consumed 1·00 kg flail-harvested silage and 1·39 kg precision-chop silage. Compared with flail-harvested silage, precision-chop silage increased ewe body weight immediately post lambing by 5·1 kg, lamb birth weight by 0·27 kg and lamb growth rate by 58 g/day. Increases in intake of precision-chop silages by hoggets were on average greater, though more variable, than by ewes and were reflected in increased carcass weight.

The reason for the increased intake of the finely-chopped silage was examined. It would appear that the major factor is the physical size of particle involved though there was some evidence that improved fermentation resulting from finer chopping may have been partly responsible for increased intake.

A model is described, which maximizes hay intake in the formulation of rations for pregnant ewes in the last 6 weeks of pregnancy. A regression of hay intake upon hay digestibility, concentrate level, ewe live weight, number of foetuses carried and week of pregnancy, derived from an experiment on individually-recorded ewes, is used as the intake constraint in a linear programme. This is solved in an interactive program which can be implemented on several makes of microcomputer. The intakes of hay predicted by the model are lower than those reported elsewhere, reflecting the more accurately recorded intakes of the original experiment compared with most other published data. The rations formulated by the model show that in weeks 16 to 18 of pregnancy hay could provide most of the ewes' requirements and especially when hays of high metabolizable energy concentration are used. The ease of changing the values of the inputs and the speed of the ration formation enable any number of rations to be formulated quickly for a range of hays and individual conditions.

The effects of diet acidification on the growth performance of piglets were assessed in two experiments. In the first, 167 piglets were weaned at 10 days of age and penned in litter-mate groups (seven groups per treatment) which were allocated to one of three diets, with either citric acid (30 g/kg; C), fumaric acid (15 g/kg; F) or no additional organic acid (N); pigs were fed ad libitum for 25 days. The rate of live-weight gain was significantly higher for treatment C than for treatments F or N (216 (s.e. 10), 170 (s.e. 7) and 189 (s.e. 6) g/day respectively; P < 0·05). The voluntary food intake on treatment C also tended to be higher than on the other two diets (220 (s.e. 24), 182 (s.e. 18) and 189 (s.e. 7) g/day for treatments C, F and N respectively).

In experiment 2, 30 crossbred piglets were penned in single-sex groups of three and weaned at 10 days of age. The same diets were used as in experiment 1 but all three diets were available ad libitum to each group of piglets for 25 days. When dietary choice was allowed, piglets consumed significantly greater quantities of the control diet than of the acidified diets (1381, 1422, 2972 (s.e. 132) g/day for diets C, F and N respectively; P < 0·01). When the relative intake of each diet was correlated with live-weight gain, only diet C showed a significant positive correlation (r = +0·74; P < 0·05). Correlations of F and N intakes with live-weight gain were negative. It is concluded that citric acid (30 g/kg) in the diet of early-weaned piglets promotes live-weight gain, although acidification of the diet may decrease palatability.

In muscle and livers of steers given a diet with sodium monensinate a significant decrease in cadmium content was observed. The concentration of manganese, copper, zinc, lead and iron in the analysed organs varied inconsistently. It seems from the results that, in tissues, monensinate influences the metabolism not only of monovalent cations but of polyvalent cations as well.

Two trials were undertaken to investigate the effect of rolling on the digestibility of barley and oat supplements offered to pregnant ewes at 0·43 kg dry matter per day. In the first trial, with ewes given a basal diet of grass silage ad libitum, rolling barley improved the apparent dry matter digestibility of the diet by 0·036 (s.e. 0·0115) and reduced the excretion of whole grains from 0·127 (s.e. 0·0190) of grain fed to almost nil. Method of storage (dried or treated with propionic acid) had no effect on utilization of whole or rolled barley. Grain excretion was lower with whole oats 0·049 (s.e. 0·0147) than with whole barley. In the second experiment, basal diets containing hay or roots ad libitum were supplemented with whole or rolled barley and oats. Excretion of whole grains was very low on the root-based diets and amounted to only 0·047 (s.e. 0·0177) for the whole barley and hay diet. Excretion of whole grains varied between animals and was shown to be a characteristic of the animal. It was concluded that in most situations grain should be given whole to ewes but that it may be advantageous to roll barley when it is given with silage.

Finnish Landrace × Dorset Horn ewes were offered 300, 600 or 900 g fresh weight per day of concentrates and forage ad libitum from day 105 of pregnancy until lambing. Spring barley straw (S) or hay (H) was offered either untreated (U) or following treatment with anhydrous ammonia in an oven (T). Organic matter digestibilities (in vitro) were 0·42, 0·58, 0·42 and 0·60 and nitrogen contents were 7·2, 18·6, 12·0 and 25·0 g/kg dry matter for US, TS, UH and TH respectively. Forage intake did not differ between ewes carrying two or more foetuses but the small number of ewes carrying one foetus ate more straw (6·8 v. 4·5 g organic matter (OM) per kg live weight) than ewes carrying two or more foetuses. Ammonia treatment increased intake; the increase was larger on straw (4·6 v. 100 g OM per kg live weight) than on hay (9·0 v. 10·7 g OM per kg live weight). Replacement rates of forage by concentrates were -0·21, +0·06, -0·48 and +0·08 kg forage per kg concentrates for treatments US, TS, UH and TH respectively; only the value for treatment UH differed significantly from zero. On most treatments forage intake decreased as pregnancy progressed and the declines were greater when treated forages were offered. Concentrate level had a large effect on most aspects of ewe performance. Ewes offered treated forage gained slightly more weight in pregnancy (138 v. 104 g/day), had a slightly smaller decrease in body condition score (-0·54 v. -0·68) between day 105 and lambing but did not have greater lamb birth weights than ewes on untreated forage.

The accuracy of six methods to estimate carcass leanness in young rams was studied in 36 Texel-Oxford rams, measured at 5 months of age. The rams were slaughtered and dissected. Plasma non-esterified fatty acid and very low density lipoprotein concentrations, sampled before, during and after fasting, showed no relationship with carcass leanness. The same was true for food conversion efficiency measured from 6 to 16 weeks of age, and for measurements taken with the Scanogram ultrasonic machine. The Vetscan and Danscanner ultrasonic machines gave repeatable measurements of fat depth (0·41 and 0·46 respectively). The Vetscan was the best predictor of carcass leanness by proportionally reducing the residual mean square by about 0·20, corresponding to a correlation of −0·45 between ultrasonic fat depth and carcass leanness. Inclusion of average daily gain and ultrasonic fat depth in a selection index would allow appreciable improvements in both traits.

Melatonin was fed daily at 14.00 h to eight non-lactating and six lactating hinds. Feeding was begun on 27 July 1983 (day 1) and continued until 21 September (day 57). Six non-lactating hinds were used as controls. Blood samples were taken about every 10 days from day 42 until day 73. Plasma progesterone and prolactin were determined by radioimmunoassay. Progesterone values of greater than 0·63 μg/1 were taken to indicate the presence of a corpus luteum and that the animal had ovulated. In the melatonintreated, non-lactating group seven of the eight hinds showed ovarian activity compared with two of the six controls (P < 0·01). None of the lactating hinds treated with melatonin showed evidence of ovarian activity. In both the lactating and non-lactating hinds treated with melatonin, prolactin levels were never greater than the detection limit of the assay (7·4 μg/l), while, in the control hinds mean prolactin levels were elevated on all but the last sampling day. It is, therefore, possible to induce early ovarian activity in non-lactating red deer hinds by feeding melatonin. However, although melatonin treatment similarly depressed plasma prolactin levels in both lactating and non-lactating hinds, it was unable to overcome the inhibitory effect of lactation on reproduction.

Two experiments are described in which individually-penned Suffolk × (Blue-faced Leicester × Swaledale) lambs were given complete diets based on grass silage, and voluntary intake, live-weight gain and nitrogen (N) retention were measured.

Experiment 1 investigated the effects of supplements of fish meal (0, 60 and 120 g/kg diet dry matter (DM)) and barley (0, 150 and 300 g/kg diet DM) in a 3 × 3 design using 72 lambs. The lambs averaged 35 kg live weight at the start of the 47-day experiment. Fish-meal supplements increased daily intakes of diet DM, silage DM and metabolizable energy (ME), and improved daily gains, carcass weights and N retention. Barley supplements increased daily intakes of diet DM and ME, but reduced silage DM intake; live-weight gain, carcass weight and N retention were all improved.

Experiment 2 investigated the effects of supplements of rapeseed meal (0 and 120 g/kg diet DM) in two forms (untreated and formaldehyde-treated) and barley (0 and 150 g/kg diet DM) in a 2 × 2 × 2 design with two missing treatments and using 48 lambs. The lambs averaged 39 kg live weight at the start of the 42-day experiment. Rapeseed meal supplements increased daily intakes of diet DM, silage DM and ME, and improved daily gains, carcass weights and N retention. Form of rapeseed meal had no effect. Barley increased diet DM and ME intakes and improved daily gains and carcass weights.

Ewe's colostrum, dried milk, ewe's blood, cow's blood and cow's serum, given to a total of 56 newborn lambs, had various effects on serum immunoglobulin concentrations, the gut closure process and early growth rate.

Cow's colostrum and serum proved to be good alternative sources of immunoglobulin for rearing lambs. Cow's and ewe's blood had adverse effects on immunoglobulin absorption, speeding up the closure process. This process was only slightly affected when lambs were fed immunoglobulin-free powdered milk.

Lambs survived with concentrations of serum immunoglobulin as low as 5 zinc sulphate turbidity units. Similar and satisfactory mean early growth rates were observed for lambs given ovine and bovine colostrum and bovine serum, whilst those given ovine and bovine whole blood had relatively low early weight gains. Those receiving powdered milk substitute followed by ewe colostrum at 8 h post partumshowed intermediate rates of growth.