1. An experiment to test the effects on growth rate of lambs to 15 kg live weight of 5, 7 or 9 kg of milk replacer powder given according to four systems of daily restriction is described and the results are discussed.

2. Although the average age at weaning varied from 18 to 50 days according to treatment, the quantity of milk replacer did not affect the lambs' overall growth rate. Lambs deprived of milk consumed extra concentrates at a rate of 1·75 ± 0·219 kg per kg of milk powder.

3. Although severe restriction of the daily allowance markedly reduced the growth of lambs during the milk-feeding period, they subsequently grew at a faster rate and there was no resultant major depression of overall growth rate. The lambs first consumed a measurable quantity of solid food when they were on average 21 days old and this varied little according to treatment.

4. It is concluded that under the conditions of this experiment it was not economic to give more than 5 kg of milk powder and that it was not advantageous to adopt distribution systems that delayed weaning much beyond 20 days.

5. The applicability of these findings to practice is discussed in relation to the possibility of treatment effects from the rearing period being carried over to the period beyond 15 kg live weight, and also to the possible effects of single penning versus grouping on lamb behaviour.

1. In the first experiment, the digestibility of diets containing ratios of 1:1 and 1:4 hay to concentrates was determined at five levels of feeding in castrated male sheep. With diet 1.1, increasing the daily dry matter intake from 600 to 1400 g resulted in a linear decline in organic matter digestibility from 74·4 to 68·6%. The same increase in level of feeding led to a curvilinear decline in the organic matter digestibility of diet 1.4 from 83·0 to 75·9%.

2. In a similar way the crude fibre digestibility of the diets declined as food intake increased. Also the increase in level of feeding caused a decrease in the mean retention time of stained hay in the alimentary tract.

3. In a second experiment the digestibility of long dried grass offered ad libitum to eight dry and eight lactating cows was measured and compared with the digestibility of similar dried grass offered at maintenance level and ad libitum to eight castrated male sheep.

4. On a metabolic live-weight basis (kg W0·73), the lactating cows ate 34% more organic matter than the dry cows and the mean voluntary intake of sheep was only 54% of the intake of dry cows.

5. The organic matter digestibility for the dry cows was 1·9 units higher than that of the lactating cows and at ad libitum intake the organic matter digestibility for the sheep was 5·6 and 3·7 units lower than that of the dry and lactating cows respectively. The results are discussed in relation to the validity of extrapolating results obtained with sheep to cattle, and with non·lactating to lactating animals.

A series of animal feeding trials was designed to determine differences between grasses in dry-matter intake and animal live-weight gain, with a view to indicating better selection criteria for improving the feeding value of herbage.

Wide differences were demonstrated in feed intake and live-weight gain between single-variety grass feeds at similar levels of digestibility.

S.37 cocksfoot gave consistently good and S.51 timothy, consistently poor responses.

Supplementation of grass feeds with red clover frequently resulted in marked improvement in feed intake and animal performance.

1. The rates of eating silages and hay throughout a meal were recorded in eight cows consecutively using a special manger and an automatic recording apparatus. At each meal the rate of eating was highest in the first five or ten minutes and then fell gradually. These characteristics were observed both on silages and on hay and for all the experimental cows. The mean rates of eating hay, but not of silages, agreed with previous reports.

2. The highest rate of eating was slightly faster at the evening meal than at the morning meal, when cows received equal amounts of feeds twice each day. The rate of eating declined at much the same rate throughout each meal when the cows received from 2 to 5 meals daily.

3. When the cows were fed twice daily, the rate of eating throughout a meal was not affected by changing the interval between meals from 12 hr to 6 hr.

4. When cows were given large amounts of feed at any one time, three stages of rate of eating, fast, decreasing and slow, were recognized.

5. The quality of feed, individuality of cow and pregnancy evidently affected the rate of eating throughout a meal.

Genetic parameters of veal calves were estimated from data on 510 Danish Red male calves by 39 sires.

Heritability estimates for the growth and carcass traits were low, those for body dimensions and dressing percentage high.

Correlations between the growth and carcass traits indicated no genetic incompatibility in selection.

The problem of achieving simultaneous improvement in the dairy, carcass and growth qualities is discussed. It is suggested that the adoption of performance testing for growth and carcass quality prior to the entry of bulls into AI service, followed by progeny testing for milk and fat yields, would provide the best method of genetic improvement.

Repeatability estimates for various maternal characteristics were calculated for 301 inbred, 150 outbred and 135 linecross Large White sows each with two litters. The estimated repeatabilities did not differ significantly between the three kinds of sow and the arithmetic average of the values obtained were as follows: number of pigs born alive 0·24; number of pigs born dead 0·05; total birth weight of litter 0·25; average individual birth weight 0·41; number of pigs alive at 50 days 0·07; total litter weight at 50 days 0·14; average individual weight at 50 days 0·15.

The linecross sows produced and weaned more pigs than the outbred sows, which in turn performed better than the inbred sows. Changes in performance from the first to the second litter were similar for all three groups of sows.

Samples of sheep's milk were used to study the occurrence of β-lactoglobulin variants of fast or slow electrophoretic mobility. The distribution of variant types between a sample of daughters and their dams was in general accord with simple Mendelian expectations for two autosomal co-dominant alleles.

A survey of albumin polymorphism in the major breeds of cattle in the British Isles is described. Four and probably five alleles have been found. AlbA is the common type in all breeds. AlbB occurs with less than 1 % frequency in all breeds except Sussex and Charolais, where it has a frequency of 12% and 16% respectively. The possible implications of this finding are discussed. The other alleles AlbC(Ed) and AlbD are extremely rare, and are confined to a few animals each within one breed. AlbG has been tentatively proposed as the name for a new albumin type.

1. Twenty-four Southdown and 24 Welsh Mountain year-old female sheep, half on high plane and half on low plane nutrition, were closely shorn and given two short acute cold exposures (−20°C, 4 mph wind) in climate chambers. For two weeks before the first acute exposure half the sheep were kept at a moderately cold temperature (+8°C) and the remainder at a thermoneutral temperature (+30°C). During the next two weeks between acute exposures these temperatures were reversed for each group of sheep.

2. Resistance to body cooling during acute cold exposure was significantly greater after exposure to + 8°C. This was attributed to acclimatization. No further acclimatization resulted from acute cold exposure in addition to chronic moderate cold exposure.

3. Sheep which had been kept at +8°C cooled 33% more slowly than those which had been at + 30°C. High plane sheep cooled 34 % more slowly than low plane sheep. Southdowns cooled 32 % more slowly than Welsh sheep, but the Welsh sheep showed relatively greater acclimatization on low plane nutrition.

4. Compared with Scottish Blackface sheep given similar temperature treatment in an earlier experiment, the Southdowns and Welsh showed less initial cold resistance and less capacity for acclimatization.

Shorn Southdown and Welsh Mountain sheep on high or maintenance levels of nutrition were subjected to two acute (−20°C; 4 mph wind) cold exposures in climate chambers. Before and between exposures the sheep were kept in either a cold (+8°C) or a thermoneutral (+30°C) environment.

1. At +8°C, all the sheep shivered and showed sustained vasoconstriction and elevated heart rates.

2. At + 30°C, heart rates, skin temperatures on the extremities and muscular tone were all consistently higher in sheep which had previously been kept at +8°C.

3. During cooling, the onset of vasoconstriction and increase in heart rate were both delayed in sheep previously kept at + 8°C.

4. These effects (2, 3) were retained for at least 2 days but less than 12 days after the sheep returned to thermoneutrality. They decayed faster than the increased resistance to body cooling produced simultaneously in the same sheep (Sykes and Slee, 1969), since this was still detectable after 2 weeks.

5. Breed differences were mainly small.

6. It was concluded that acclimatization induced by chronic cold exposure was associated with a temporary increase in basal metabolic rate.

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.

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.

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.

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 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.