Two experiments were carried out to study the energy requirements of young fattening lambs for maintenance and production. Forty weaned lambs were used in each experiment, 20 being allocated to a high level of feeding (900 g air-dry feed per day) and 20 to a low level (540 g). The animals used in Experiment 1 were approximately 12 months of age and their mean live weight was 35·3±4·03 kg. Those in Experiment 2 were approximately seven months of age and their mean live weight was 36·7 ± 4·57 kg. Experiment 1 continued for 100 days and Experiment 2 for 47 days. Three digestibility trials, involving three animals from each feeding level, were carried out during the course of each experiment to obtain precise estimates of digestible organic matter intake (DOMI). The estimated mean DOMI required for maintenance for a 45-kg lamb was 400 g (0·88 lb) or 1500 kcal metabolizable energy per day. The estimated maintenance requirement was not affected by the age of the animal. The DOMI required for production ranged from 1·55 kg per kg live-weight gain for the younger animals to 1·71 kg for the older animals. Both these requirements were lower than those obtained by other workers and those suggested by the Agricultural Research Council (1965).

A portable EEL reflectometer was modified to measure the variations in the brightness of pig meat. The instrument was calibrated spectrophotometrically with reference to the luminous reflectance of standardized materials and selected meat samples. A very satisfactory level of agreement between the instrument and the visual assessment of muscle paleness was found in an investigation involving 251 pigs.

A feeding trial was conducted on 24 individually-fed pigs given either a diet containing plant protein with insufficient Iysine and methionine or the same diet with optimal Iysine and methionine levels. Supplementation of the diet with synthetic amino acids significantly improved daily live-weight gain, feed conversion, nitrogen balance, loin eye muscle area and total yield of lean muscle.

Pigs receiving insufficient Iysine and methionine were characterized by lower haemoglobin and creatinine values accompanied by a decreased level of glutamic oxaloacetic transaminase.

There were highly significant differences in the blood and liver Iysine levels of the two treatments, and significant differences in the fresh muscle and in the pressed muscle juice Iysine levels.

The ratios between liver and blood Iysine levels and between dietary or muscle Iysine levels and % of nitrogen retention were calculated and found to be the same on both treatments.

The accumulation of Iysine in liver and muscle was linearly related to the blood Iysine level and to N retention and Iysine intake.

Southdown and Welsh Mountain female sheep, equal numbers on high and low plane nutrition, were shorn and subjected to two acute cold exposures (−20°C, 4 mph wind) in climate chambers. Before the first exposure the sheep were kept in either a cool (+8°C) or a thermoneutral (+30°C) environment for two weeks. Between exposures these environmental temperatures were reversed within groups. Blood samples were withdrawn at the beginning and end of the two week exposures and on three occasions during acute cold exposure. Plasma analyses of Ca, P, Mg, Na and K were carried out. Exposure to +8°C caused a 12% reduction in plasma Mg levels of all sheep, but had no effect on Ca, Na or K levels. There were breed × temperature interactions with respect to plasma P levels. Acute cold exposure caused reductions in plasma Mg and Ca levels and an increase in plasma P levels of all groups of sheep. Changes in plasma Na and K levels could have been caused by plasma concentration.

Electrolyte levels initially displaced by exposure to +8°C showed no evidence of a return to normality two weeks later. Only for Ca was there evidence that prior exposure to +8°C modified the response to acute cold exposure.

Haemoglobin types in three breeds of sheep were investigated. All three haemoglobin types—A, B and AB—were found to be present in the animals in two of the breeds examined, namely Bikaneri and Corriedale × Bikaneri (F1 generation). Mandia sheep had only Hb B and Hb AB types. Haemoglobin JB animals predominated in all the three breeds, the Mandia breed having the highest percentage of these animals. The possible significance of these findings is discussed.

Thyroid activity was assessed in two groups of crossbred lambs and in Dorset Horn lambs fed ad libitum, by measuring the rate constant (K4) for the release of 131iodine from the gland. The results demonstrated a highly significant curvilinear correlation (P<0·001) between growth rate and the rate constant (K4) in experiments based on individual measurements in animals from three populations.

Separate work carried out on the measurements of both thyroid size and RNA/DNA ratio suggests a need for caution when these are interpreted as parameters of thyroid activity. In the growing animal these may be more reflective of the growth of the thyroid gland itself, differences which may be governed by factors not directly related to variations in hormone secretion rate.

The findings are discussed in terms of an explanation of the contradictory results obtained where attempts have been made to alter the thyroid status of growing animals by the use of thyroid hormone analogues and thyroid depressant drugs.

Milk and butterfat production data from eight herds of dairy cows in Australia for the years 1963 and 1964 were analyzed for relationship with serum transferrin type. In the 932 lactations considered D2/D2 cows produced 521 ± 152 lb of milk more than A/A cows and lactated 15·3 ± 7·8 days longer after correction for season. There was no difference in fat percentage of the milk. The production of A/D2 cows was also significantly higher than A/A cows, but less than D2/D2 cows. Allowing for differences in lactation length still left a significant difference between D2/D2 and A/A cows in milk yield.

The best estimate of the effect of replacing a TfA by a TfD2 gene, allowing for season, was 170 lb more milk (P<0·01) and 6·5 days longer lactation (P<0·05), while TfD1 did not differ from TfA in either yield or lactation length.

From observations made over 3 years on a flock of Welsh Mountain sheep kept at 210 to 330m above sea level there was no indication that ewes especially sought shelter for lambing when wind speed was under 8 km/hr or the Kata cooling power was below 20 millical/cm2 per sec. When wind speed or cooling power rose, lambing sites chosen by the ewes were progressively more sheltered. Average wind speed and Kata cooling power at sheep height at lambing sites were about 14 km/hr and 35 millical/cm2 per sec.

Variability in wind speed and cooling power at an unsheltered site accounted for only 24% and 18% of the variability in these measures at the lambing sites, thus the lambing sites chosen depended to a considerable extent upon other factors, which are discussed.

The environment at lambing sites chosen by ewes cannot be taken as the optimum. No attempt was made to correlate lambing site environment with ewe or lamb performance.

The effect of the time of mating on ewe fertility and subsequent lamb growth was examined in Clun sheep in Scotland. The flock of 249 females was divided into six mating groups, the first was put to a fertile ram on 12 October 1962, the remainder being added at two weekly intervals.

There was a marked decline in the average number of lambs born per female lambing as the time of mating moved from October to December (b = −0·007 per female per day). Other components of fertility were not affected.

The mean birth weight was slightly greater in the later mating groups; however, by the time the lambs were 9 weeks of age, the trend was reversed, the regression of 9-week weight on day of mating being −0·063 lb per day.

Twenty-four Friesian calves were fed from twelve weeks of age on six diets containing 15 or 30% ground barley straw, the straw being ground through screens of and in.

From twelve weeks to seven months of age (120–250 kg) the calves had mean growth rates of 1·15 kg/day with a feed conversion ratio of 4·15: 1. From seven to eleven months of age (250–380 kg) the corresponding figures were 1·16 kg/day and 5·53: 1, and in the final fattening period of 11–14 months (380–500 kg), 0·92 kg/day and 8·19: 1.

These differences between stages of fattening were highly significant. There were no differences in performance due to the particle size of the straw or to the proportion of straw in the diet.

Eighty-two Scottish Blackface castrated male sheep were used to test whether, from weaning to near maturity, the gigot grew exactly proportionally to the half carcass and whether the tissue in the gigot grew at the same rate as the respective tissue of the half carcass.

While slight deviations from exact proportionality of growth occurred, none could be adjudged significant or important. If the gigot does not grow directly proportionally to the half carcass the data suggested that the gigot tended to grow slightly more slowly than the total half carcass over this period. If gigot muscle does not grow proportional to the total muscle the data suggested that gigot muscle might grow slightly more slowly. If growth of bone tissue is not directly proportional between the gigot and the half carcass the tendency was for the gigot bone to grow slightly faster than total bone while the fatty tissue of the gigot showed a slight tendency to grow more slowly than the half carcass fatty tissue.

Dobruja Finewool ewes were mated to two rams of each of the Clun Forest, Hampshire, Suffolk and Oxford Down breeds as well as to rams of their own breed. The crossbred and purebred lambs were compared in terms of growth, food consumption and carcass attributes. The crossbred lambs of Hampshire, Suffolk and Oxford Down breeding were superior to the purebred control lambs on all counts while Clun Forest crossbred lambs were superior to controls only in carcass attributes and the time taken to reach slaughter weight but not in efficiency of conversion.

In the first of two experiments, steers which received a single implant of 60 mg hexoestrol grew 24% faster than non-implanted controls and 7% faster than steers given 30 mg. The growth rate of the steers given a single implant of 60 mg did not differ significantly from that of animals implanted twice with 30 mg or 5 times with 15 mg. In the second experiment, steers given 60 mg grew 23% faster than controls and their feed conversion efficiency was 13% better; the hexoestrol treatment resulted in a saving of 131 kg feed per animal. The tenth-rib joints of steers given 60 mg had a higher crude-protein content and lower fat content than those from non-implanted animals.

A by-product of the distilling industry designated ‘distillers’ grains plus solubles' was evaluated using forty-eight growing pigs. The product was included at 0, 14·7 and 25% in three diets in which the proportion of other constituents was adjusted to give similar concentrations of TDN, dry matter and crude protein.

The performance and carcass quality of pigs receiving 0% and 14·7% of the by-product in the diet was similar, but inclusion at 25% significantly reduced growth rate (g/day) from 632 for the 0% diet to 578.

Body composition of a pair of related double-muscled and normal Aberdeen Angus females was analysed. The following ratios of weights of body components of the double-muscled individual to the normal were found: empty body, 1·0; carcass, 1·1; total muscle, 1·4; carcass fat, 0·7; offal fat, 0·9; viscera, 0·9; hide, 0·8; ash (in carcass), 1·0. The data supported an hypothesis of generalized muscular hypertrophy. The empty body weight of the normal female was 474 kg.

The growth of pigs kept continuously or intermittently in metabolism cages was compared with that of animals penned in groups. The ten continuously caged grew more slowly and contained more fat at slaughter than their penned littermates.

The Society was founded 25 years ago, in January 1944, and this is perhaps a fitting occasion to look back on its origins and to give a short account of its growth and achievements.

Voluntary hay intake and milk yield were measured in 11 singlesuckling and 4 twin-suckling ewes for the first seven weeks of lactation. There was no significant difference between the intakes of the two classes of ewe and milk yield differed only in the seventh week. Variations in milk yield and live-weight change were significantly associated with variations in voluntary intake. Lamb weight gain was correlated with milk yield and voluntary intake of the dam.

In trials 1 and 2, supplements of urea and cottonseed meal increased the protein content of the basal diets from 12·2 to 14·0–14·6%, but had no significant effects on growth rate or carcass characteristics. In trial 3 the effect of cottonseed meal on growth rate was almost significant but urea had less effect. In trial 4, the basal diet contained 11·0% protein; soya bean meal increased this to 13·1% and had an almost significant effect on growth rate. Lysine and lysine + urea had no effect.

The LDH values in blood plasma of Pietrains and Large Whites are significantly different during moderate stress (sampling of blood), being higher in the Pietrains. The difference is largest in the LDH-5, the muscle iso-enzyme. Not only are the values higher, but the isoenzyme is also demonstrable in more individual animals.

More stressful situations (forced muscular exercise) result in a rise in plasma LDH-5 in both breeds; the rise is larger in the Pietrains. Two possible causes for the higher LDH-5 values in Pietrain blood plasma are suggested.