1. Six experiments each with 2 groups of 9 pigs (9 castrated males and 9 females), 26 to 31 kg initial weight, were kept in a large indirect calorimeter equipped with two identical pig pens. In each pen nine animals were housed for periods of 6 to 8 weeks. The floors tested were: asphalt, straw bedding on asphalt (25 mm straw on asphalt), and concrete slats. Two experiments, each of four periods, were performed on each of the floors. The temperature in the calorimeter was changed in stepwise fashion by 2 to 3°C at intervals of 2 to 3 days. In periods 1 and 3 the temperature was decreased stepwise from 20·23°C to 5·8°C, and in periods 2 and 4 in the reverse order. Gaseous exchange was measured at each of the temperatures for 48 hr. Feeding level was kept constant at about 1160 kJ meta-bolizable energy/kg0·75.day.

2. Heat production and energy balance per unit of feed intake were similar on all floors in the zone of thermoneutrality and the derived maintenance requirements were also similar with a mean value 438 kJ/kg0·75.

3. The effective critical temperature of animals weighing 40 kg was 11*5 to 13°C on straw bedding, 14 to 15°C on asphalt and 19 to 20°C on concrete slats.

4. At temperatures below the critical temperature heat production was increased. The increase in extra thermoregulatory heat production was on average 8·9 kJ/kg0·75 per °C below the effective critical temperature. Between the various floor types differences in this increase were noticed, but were not significant.

5. Body-weight gains on asphalt and straw bedding were similar; on concrete slats the body-weight gain was significantly reduced.

1. Twenty-six shorn Scottish Blackface sheep received nine daily cold shocks (down to −10°C) each lasting 1 hr. This treatment reduced the metabolic response to cold (lower heart rates) and caused passive body cooling—defined as habituation. Eight selected sheep showing maximum habituation and 16 untreated controls then received blocking treatment (re-shorn and cooled for 2 hr at 18°C or 8°C) before being heat-stressed (at 42°C) to elicit panting.

2. Thermal panting, delayed as expected by blocking treatment, was further delayed by previous cold habituation. Habituated sheep blocked at 18°C panted 30 min later than blocked controls. In habituated sheep blocked at 8°C, panting was completely inhibited even after 90 min heat stress; their final mean respiration rate was 19/min v. 220/min in blocked controls and 250/min in unblocked controls. Rectal temperatures of habituated sheep were lower than controls during blocking treatment.

3. Habituation, by restraining the normal metabolic response to cold, increased the heat debt during blocking treatment and lessened the heat load during subsequent heat stress. This apparently reduced the drive for panting. Habituation may also have favoured a direct inhibitory effect of cold on the respiratory centres.

Observations have been carried out on the effect of social environment on the behaviour and growth rates of British Friesian male calves artificially reared on an automatic Nursette milk dispenser. The observations were made during two watches of 3 hr duration per week for the first 9 weeks of the calves' stay in the rearing unit. The calves appeared to be in a high state of anxiety on arrival and showed a vigorous following response to each other and the stockman. Although the lighter subordinate calves spent less time in sucking the Nursette than the heavier dominant calves, and had a lower pre-weaning growth rate, they spent more time ingesting dry feed. Consequently they suffered a less severe check in growth rate at abrupt weaning after 6 weeks than the dominant calves. Non-nutritive cross-sucking of the ear, scrotum or prepuce of others in the group occurred in some calves. The aetiology of cross-sucking is discussed and interpreted in terms of an oral deprivation hypothesis.

In a 15-year period (1956-1970) data were available from 192 Brahman cows exposed to bulls on 1409 occasions (1199 calvings) and from 155 Santa Gertrudis cows exposed 907 times (847 calvings). All were mated by natural service in the same herd in Cuba. Calving percentage and net calf crop significantly favoured the Santa Gertrudis with overall means of 92·7 and 85·3% for the two traits respectively. Parity, lactation status and year of calving significantly affected calving percentage with significant year × breed and status × parity interactions. Lactation status, year of calving, breed × year and status × parity interactions also affected net calf crop. Calf mortality was 6·41% in Brahmans and 5·64% in Santa Gertrudis but more of the latter breed were stillborn (41·7 v. 16·9% of all deaths). There were no breed effects on age at first or last calving, age at culling or calves per cow which were 38·5 months, 117·1 months, 130·1 months and 6·62 calves in Brahmans and 39·3, 111·5, 123·2 and 6·58 respectively in Santa Gertrudis. Twinning percentage was low (under 0·4%) and male births high (53·54%) in both breeds. Some 30% of cows lost at least one calf prior to weaning during their lifetime.

Over a 15-year period 1011 calving intervals from 187 Brahman (B) cows and 687 calving intervals from 146 Santa Gertrudis (SG) were examined. Year of calving significantly affected intervals in both breeds. Season of calving and parity of dam were both important in SG. Longer intervals were seen in B than SG (437 v. 406 days). Repeatability of calving interval was low (< 0·02). The average life-time calving interval was significantly related to total calf production in that cows with shorter mean intervals had more calves in their lifetime.

Complete diets each containing (1) 0%, (2) 20%, (3) 40%, (4) 60% high-quality, (5) 20% and (6) 40% low-quality dried grass were given ad libitum to 48 British Friesian calves.

The performance of the animals was studied over the stages of growth from 50 to 100 kg and 150 to 200 kg live weight. At each stage of growth the live-weight gain was similar on all treatments while the daily intake of dry matter was significantly affected by the treatments. Over the stage of growth from 50 to 100 kg live weight the intake of metabolizable energy was greatest on treatment 2 and lowest on treatment 4. The conversion ratio of metabolizable energy decreased with increasing levels and with both qualities of dried grass over the weight range 50 to 100 kg.

When the calves reached 100 kg live weight, digestibility and N balance studies were carried out. The metabolizable energy (ME) expressed as a percentage of the gross energy decreased with increasing levels and with the lower quality of dried grass. Nitrogen retention was not significantly affected by treatment differences.

The relationships of the voluntary intake of dry matter, ME intake and the conversion ratio of ME with the ME expressed as a percentage of gross energy over the lower live-weight range are also presented.

The Israeli procedure for measuring sire breeding values and genetic progress due to selection is described. The estimate of sire breeding value has two components, the current contemporary comparison (CC) and an adjustment for the average genetic deviation of the contemporaries from the original base population. The combined value is called the cumulative difference (CD). For practical purposes the CD was found to be free of the time trends observed for CC, and the residual variances of the two measures were approximately equal. The relative genetic level in any given time interval was measured by the average CD of all sires used during the period October 1964 o t January 1971 in Israel. The analysis indicates that essentially all of the progress in 122-day FCM yields was due to sire selection, whereas 60% of the progress in 305-day FCM yields was due to selection and 40% to improved management.

In an experiment with group-fed cattle from 6 months of age to slaughter at 480 kg live weight two levels of feed intake: 1, ad libitum, 2, 85% of ad libitum amount, were combined with two ratios of concentrate to hay: a, 70: 30; b, 30: 70. In two further treatments, 3a and 3b, the cattle were fed diets a or b at 70% of ad libitum from 6 to 10 months and ad libitum thereafter.

Daily gain during the first 124 days of the experiment was (in grams) 1293, 983, 1097, 846, 992 and 756, and from the 125th day to slaughter 735, 600, 796, 579, 830 and 714, for treatments la, lb, 2a, 2b, 3a and 3b, respectively. The decline in rate of gain from the first period to the second was inversely related to the level of feed intake and to the percentage of concentrates in the ration in the first period.

Daily carcass gain was 582, 393, 532, 350, 531 and 368 g for treatments la, lb, 2a, 2b, 3a and 3b, respectively.

The treatments that were switched over from 70% of ad libitum feed intake in the first period to 100% in the second (3a and 3b), exhibited considerable compensatory growth in the second period, but this was not sufficient to be of economic advantage.

The overall ME requirement per kg of live-weight gain was inversely related to rate of gain. Of the six treatments, 2a (85% of ad libitum, 70% concentrate) was the most efficient (19·8 Mcal/kg live-weight gain).

Animals on the 100% level of feed intake throughout the experiment (treatments la, lb) were significantly fatter than those on the other treatments.

In Experiment 1, 24 early-weaned, male lambs were given ad libitum a diet based on either rolled or whole barley, both pelleted through a 7·4 mm die. Growth rates were 360 and 409 g/day, food conversion ratios 2·80 and 2·56 kg dry matter/kg gain, and organic-matter digestibilities 77·8 and 80·4% for the two diets respectively. In Experiment 2, 12 early-weaned, female lambs were given a diet based on either whole barley pelleted through a 7·4 mm die or unprocessed barley. When the diets were given in restricted quantities those containing unprocessed barley were slightly but significantly higher in digestibility. The feeding of unprocessed barley increased the firmness of subcutaneous fat and the contents of the rumen at slaughter, but decreased liver weight.

In Experiment 3,36 early-weaned, female lambs were given ad libitum diets based on either pelleted rolled barley, pelleted whole barley or unprocessed barley. Growth rates were 260, 270 and 264 g/day; food conversion ratios were 3·20, 3·20 and 3·00 kg dry matter/kg gain organic-matter digestibilities were 80·8, 79·3 and 81·0%, rumen pH values were 5·2, 5·2 and 6·1, and liver weights 728, 788 and 673 g, for the three diets respectively. As in Experiment 2, the subcutaneous fat on the cold carcass was firmer and more acceptable to the butcher when whole barley was given.

An experiment was carried out with 64 lambs to determine the digestibility and efficiency of food utilization of barley, maize, oats and wheat when they were offered whole and loose, or roughly ground and pelleted.

Apparent digestibilities of the organic matter (%) for the four cereals in the order given above were 81·1, 84·3, 69·9 and 82·7 for the whole and 77·2, 82·1, 67·5 and 86·6 for the ground and pelleted grains. The corresponding live-weight gains (g/day) were 340, 345, 241 and 303, and 347, 346, 238 and 323. The corresponding conversions of dry matter (kg) to live-weight gain (kg), over the growth period from 15 to 35 kg weight, were 2·75, 2·52, 3·07 and 2·97 and 2·79, 2·62, 3·33 and 2·56.

Dexamethasone (16 mg) induced parturition in sheep when injected i n the dam on day 141 of gestation. The mean time of parturition was 49·0 ±2·18 hr after the injection, with 90% of the injected ewes lambed by the 143rd day of gestation compared with the 147th day in the control group. There was no ill effect on the ewe or the lamb born.

The velocity of sound through the limbs of living animals and through tissue excised from carcasses has been measured. The measurements are compared with calibration velocities recommended by the manufacturers of two sonar instruments used to measure the position of tissue boundaries in animals.

Sarcomere length and fibre diameter were measured in the biceps brachii and sternomastoideus muscles from 35 male mice (5·3-38·0 g body weight). The fore-limbs of each animal were either folded or stretched maximally immediately post mortem and allowed to go into rigor mortis in that position. Unfixed isolated fibres were separated and the sarcomere length and fibre diameter measured. Sarcomere length remained unchanged with increasing body weight irrespective of whether the muscles were in the folded or stretched position. Sarcomere length was shorter in the folded biceps brachii (P < 0·01) and sternomastoideus (P < 0·05) than in the corresponding stretched muscles at all body weights. The results indicate that sarcomere length cannot be used as an indicator of the longitudinal growth of muscle, and that limb position during rigor development is a significant factor in altering sarcomere length.

Two experiments were conducted with three types of polyethylene particles to establish their retention time in castrated male cattle (steers) offered diets which contained predominantly cereals ad libitum. The particles were (1) ‘Ruff Tabs’, a corrugated particle of dimension 1·27 × 0·63 × 0·95 cm3 and subsequently referred to as RT and (2) and (3) plain plastic rods of 1·27 cm length and 0·32 cm (BP) or 0·63 cm (RBP) diameter.

In the first experiment with steers weighing 170 or 260 kg, 1 kg of RT particles were excreted in the faeces at a similar rate by the steers of different weights whereas BP particles passed out in the faeces more slowly in the lighter steer.

In the second experiment 30 steers weighing 440 kg were slaughtered at 7, 14, 28 and 42 days after dosing with 1 kg of BP, RT or RBP. The recovery of RT was significantly lower (P < 0·05) than that of BP 7 days after dosing and this difference was also found at 14 and 28 days. RBP behaved like BP up to 14 days but thereafter the rate of passage of RBP was faster than tha t of BP and recovery from the rumen approached that of RT.

Experiments were carried out to determine the effects of giving 1·36 kg of ‘RuffTabs’, polythene particles of dimension 1·27 × 0·63 × 0·95 cm3 (RT) to castrated male cattle (steers) given an all-concentrate diet, on the outflow of fluid from the rumen, on rumination and on the molar proportions of volatile fatty acids produced in the rumen.

RT reduced the flow of fluid from the rumen of steers, given a restricted amount of an all-concentrate diet, from 4·65 to 2·75% rumen volume/hr. RT had no effect on the total time spent daily in ruminating and eating. The molar proportions of volatile fatty acids were unaffected by RT in steers which were given the diet ad libitum but when RT was given to steers offered a restricted allowance of feed there was a highly significant (P < 0·001) reduction in acetic and an increase in butyric, valeric and caproic acids.

The feed intake of the steers was unaffected by RT.