A method has been described of assessing the average degree of medullation in fleece samples. This method combines information about the various fibre types and the proportion of each present in the sample, by assigning 100 fibres to classes with scores 1–5 according to the degree of medullation. A weighted mean score was determined, ten times this mean being defined as the ‘medullation index’. The index has been used for 2 years on samples taken from 2-month-old lambs and 14-month-old hoggs of the Blackface breed. Drawings of fibre types showed that the internal and external diameters and their ratio all increase with the score.

The mean medullation index for the 2-month-old lambs in the 2 years was 25·6 and 24·8. The effects of sex and type of birth of lamb and age of dam were assessed by fitting constants, but their contribution to the total variance was very small. The regression of medullation on age of lamb when sampled was −0·11 units per day in both years, and was highly significant. Possible explanations for this decline of medullation are discussed.

The mean medullation index for 14-month-old hoggs was 16·1 in both years. Estimate of correlation between lamb and hogg for the 2 years were + 0·45 and + 0·33. It is probable that variation in medullation within the fleece and in fibre shedding account for these low values.

1. An experiment involving fifty Romney ewes of known history is described. These ewes were randomized to ten treatment groups of five ewes so that group mean live weights were approximately equal. The average live weight of the ewes was 147 lb. at selection and 135.5 lb. at the beginning of the 28-day experimental period. Three levels of L-thyroxine implants, viz. 150, 210 and 270 mg. were used on six groups of ewes, three of which (LT: NP, MT: NP, HT: NP) were on a normal plane of nutrition and three (LT: LP, MT: LP, HT: LP) on a low plane of nutrition. One group of ewes (DT: LP) was daily injected with 5 mg. L-thyroxine; one group of ewes (CB) was slaughtered at the commencement of the 2 8-day experimental period; one group of ewes (C:NP) was maintained for 28 days on a normal plane of nutrition and did not receive thyroxine therapy, and another group of ewes (C:LP) was on a low plane of nutrition for 28 days and was not treated with thyroxine.

2. Live-weight losses of up to 24.4 lb. for the low thyroxine (150 mg.) low-plane group of ewes (LT:LP) and 30.0 lb. for the three surviving ewes of the DT: LP group were recorded at the end of the 28-day experimental period. The daily injection of 5 mg. L-thyroxine treatment had to be modified because of two deaths.

1. The effects of l-thyroxine therapy and a low plane of nutrition on some of the non-carcass components of live weight in New Zealand Romney ewes were investigated.

2. Thyroxine treatment significantly lowered the weight of the gastrointestinal tract contents. A low plane of nutrition and a longer total starvation immediately pre-slaughter had little effect in lowering the weight of the gastrointestinal contents. Alimentary tract ‘fill’ accounted for a group mean loss of live weight of up to 5 lb.

3. Thyroxine treatment lowered the weight of the empty gastric tract, while a low plane of nutrition reduced the weight of both the empty gastric and intestinal tracts. The combined treatment effects accounted for a loss of up to 3 lb. in the weight of the empty gastrointestinal tract.

4. Neither treatment significantly reduced the weight of the omental and mesenteric fat depots.

5. The weight of the thyroid gland was unaffected by either treatment.

6. A low plane of nutrition significantly reduced the weight of the liver, kidneys and the heart but had no effect on the weight of the spleen. Thyroxine therapy significantly reduced the weight of the liver and tended to increase the weight of the kidneys and the heart.

The apparent digestibility of crude protein by the non-ruminants, pigs, horses, rats, man and the rabbit, is shown to be related to the crude protein content of the feed, and the form of the relationship is similar to that for ruminants. With non-ruminants the apparent digestibility of crude protein is markedly depressed by the crude fibre content of the feed, whereas with ruminants the depression is only slight. The relevant equations show that pigs are much more sensitive to crude fibre than horses and rabbits, and both the latter react more markedly to crude fibre than do the ruminants.

Despite the apparently significant differences between the equations for the ruminant and nonruminant herbivores, it is shown that over the normal range of crude protein and crude fibre content in feedingstuffs suitable for herbivores, the apparent digestibility coefficient of crude protein is similar for all. In other words, despite different abilities to cope with crude fibre, the herbivores as a class digest crude protein in normal feeds to much the same extent. On the other hand, the pig, an omnivore, is shown to be very markedly affected by the crude fibre content of such feeds.

1. Most of the bees which drift do so during their orientation flights and before they become regular foragers.

2. Bees emerging in August and September drift less than those emerging earlier in the year.

3. Drifting varies considerably in different circumstances, and may be extensive.

4. Drones drift two to three times as frequently as workers.

5. An individual bee is more likely to drift from a small to a large colony than vice versa, but the greater number of bees flying from the large colonies may result in a net gain in bees by the smaller ones.

6. When hives are arranged in repetitive patterns, bees drift to hives occupying similar positions in the pattern to their own. When hives are arranged in rows, bees from the centre colonies drift more than those at the end, resulting in the latter colonies gaining numerically. In some circumstances, more bees drift to hives in one direction than in the opposite direction.

7. Facing hives in different directions and painting them different colours considerably reduces drifting, the facing of hives in different directions being of the greater significance.

1. An experiment was carried out in which twelve Romney Marsh ewes were separated into two groups, one kept on a high plane of food intake and one on a low plane during pregnancy and lactation. Skin and wool samples were taken from the progeny at birth and weaning; the ratio Sf/Pf was determined for these ages as well as the proportion of follicles of various kinds and in different phases of activity. The results are compared with those of Ryder from an earlier experiment with Cheviots.

2. Differences in food intake of ewes of the order described affected live weight at weaning, but did not significantly affect the differentiation and development of secondary follicles in the foetus nor their number at weaning.

3. Lambs in the low-plane group shed secondary fibres at 12 months old much more than those which had been in the high-plane group.

4. A partial association of variation in birth Sf/Pf with variation in birth weight was demonstrated, but more than half the variation in this ratio is not accounted for in this way, and the same applies to the variation in birth S/P of the Cheviots in Ryder's earlier experiment. It is suggested that variations in foetal environment and in the early post-natal period affect the rate at which the secondary follicle population in a lamb develops towards its mature genetic maximum.

In pig progeny testing and in bacon carcass competitions some of the marks are awarded on the basis of measurements taken on the intact sides. These measurements help in assessing the value of the side, but to obtain a more complete picture of the amount of fat and to assess the size and shape of the longissimus dorsi muscle, another important point, it is usual to cut through the side at the level of the head of the last rib at right angles to the line of the back to examine a cross-section of this muscle. Whilst the fat to lean ratio is important, much attention has also been paid to the size and shape of the transverse section of the longissimus dorsi muscle, especially as regards the depth (B measurement) see Fig. 1.

1. In experiments on three calves it was shown that, under severe heat stress, the respiratory rate at first rapidly rose from 88 to a maximum of 218 respirations/min. and then fell to 167 respirations/min., while breathing at first became shallower and then deeper.

2. During the phase in which breathing became faster and shallower (panting), the heart rate rose at a mean rate of 13 beats/min. for each degree centigrade increase in rectal temperature. During the phase in which breathing became slower and deeper (‘second-phase breathing’) the mean rate of rise in heart rate was 50 beats/min. for each degree increase in rectal temperature.

3. The changes in respiratory rate and in heart rate occurred at mean rectal temperatures of 40·6 and 41·0° C., respectively, and, on average, the change in respiratory rate preceded that in heart rate by 8 min.

4. It is concluded that second-phase breathing was the cause of the steep increase in heart rate.

5. The steep increase in heart rate is discussed in relation to heat production of the respiratory muscles.

An investigation was carried out to determine the extent of the maternal influence on size of calves at birth and during subsequent stages of growth, by making reciprocal matings between large South Devon and small Dexter cattle. As a preliminary to the experimental results, data concerning the respective parent breeds were analysed. From the first part of the study the following information was obtained:

1. The mean weight at birth of purebred South Devon calves was 100·3 ± 1·47 lb. with a tendency, though not statistically significant, for male calves to be heavier. Calves born during the months April to July appeared to be heavier than those born at other times, but the age of the dam had no definite effect on the birth weight of offspring. It was found, however, that the sire may influence birth weight to a significant degree.

2. The mean period of pregnancy for South Devon females, carrying purebred foetuses, was 287·0 ± 0·42 days, the tendency being for males to be carried longer, but the difference of 0·97 days was not statistically significant. A statistically significant difference indicated that winter calvers carry their foetuses longer as a rule, but though heifers have shorter gestation periods than cows, the difference of 1·6 days was not significant.

1. Records of sheep with differing haemoglobin and potassium blood types were examined in a large flock of Scottish Blackface sheep.

2. Differences in reproductive performance, which would be subject to natural selection, and in growth rate, fleece characteristics, etc., which would be subject to artificial selection, were sought as an explanation for the gene frequencies observed in different breeds.

3. No significant differences were found in any weights or measurements.

4. The number of lambs produced by different types of ewe did not differ significantly, although there was some suggestion that haemoglobin heterozygotes produce a larger number of lambs at weaning.

5. Study of the equilibrium of the population, however, showed that any heterozygote advantage, if it exists at all, can only be small.

1. Swards of S. 48 timothy and S. 215 meadow fescue growing alone or together were sampled at intervals of 3 weeks throughout the season. The number and weight of leaves, stems and ears were determined, and leaf area was estimated.

2. Despite high rainfall, the total number of tillers in both species declined from the beginning of the experiment until early July, but increased again from then onwards until the original complement had been approximately restored. The number of leaves failed to show a corresponding increase in the autumn because each tiller carried fewer leaves than earlier in the year.

3. In the spring total dry weight increased more rapidly in meadow fescue than in timothy which in turn out-yielded meadow fescue later in the season. Both species attained their greatest dry weight soon after ear emergence, a period which was marked by considerable crop growth and relative growth rates.

4. Leaf area index reached a maximum before total dry weight had increased to its highest level, but then declined in both species. Meadow fescue differed from timothy by producing a second crop of foliage after the summer with a leaf area index of about 7. This second rise appeared to be due mainly to increased leaf size in contrast to timothy whose leaves became progressively smaller towards the end of the season.

5. The differences in growth between the species discussed with reference to their dates of ear emergence which in this experiment differed by about 6 weeks.

1. Three experiments are described on the feeding of supplements of calcined magnesite, linseed cake and vitamin D to dairy cows for the control of hypomagnesaemia and the prevention of hypomagnesaemic tetany on spring pastures.

2. A daily supplement of 2 oz. calcined magnesite either contained in 2 lb. of dredge corn cubes or 4 lb. dredge corn mix, or as a drench, gave adequate protection against the development of hypomagnesaemia in the fifty-six cows to which it was given.

3. The supplements of 3½–4 lb. linseed cake and 12,500 i.u. vitamin D gave only partial protection.

4. The economics of providing dairy herds with magnesite during the early grazing period is discussed.

1. Carcasses of nineteen fat lambs (from six ewes and thirteen wethers weighing from 29 to 841b., aged from 78 to 365 days, all from the Suffolk breed and all fed in pens with no grazing) have been dissected into six joints, namely neck, thorax, loin, pelvis, shoulder (including shank), and leg (including shin). The subcutaneous and intermuscular fatty tissues and the muscular tissues have been dissected from each joint and analysed for fat. The iodine number of each sample of fat has been determined.

2. The average percentage of fat in the fatty tissues of the carcass ranged from 71·9 to 87·8 and the average iodine numbers from 43·6 to 56·1. With the muscular tissues these figures were from 4·8 to 11·1 and iodine numbers from 51·5 to 61·7.

3. The extreme ranges found in the subcutaneous fatty tissue of the joints were from 63·0 to 91·6 for percentage of fat and from 43·7 to 59·3 for iodine number. For the intermuscular fatty tissue these ranges were from 52·0 to 88·4 for fat and from 41·7 to 58·5 for iodine number. The kidney fat extended this range up to 95·7 for fat and down to 36·4 for iodine number. With the muscular tissue of the joints the ranges were from 2·7 to 17·3 for fat and from 48·3 to 65·0 for iodine number. The rectus femoris muscle extended this range down to 1·8 for fat and up to 66·2 for iodine number.

An experiment is described in which 64 individually-fed pigs were used to investigate the effects of dietary protein status, administration of aureomycin and hexoestrol implantation on growth, efficiency of feed utilization and carcass conformation. The results of hexoestrol implantation and interactions with the other two variables only are reported here. The pigs were implanted at 120 lb. and again at 150 lb. and killed at 200 lb. live-weight.

The main features of hexoestrol treatment were:

1. Body length taken from the anterior edge of the aitch bone to the junction of first rib and sternum was significantly increased by 9·75 mm.

2. The percentage lean in the carcass was increased by 0·82%, representing approximately 1¼ lb. more lean meat in a 155 lb. carcass. The water content of the lean was increased but not significantly.

3. Body fat was reduced but this was not reflected in a significant change in back fat measurements.

4. No changes could be detected in the thyroid or adrenals, but whereas male castrates showed little effect of treatment on other organs apart from a certain amount of urethritis, the intact female manifested major changes in the genital tract. The uterus in particular was greatly enlarged and ovarian activity obviously reduced. The implications of these effects are being examined.

5. There was no response to treatment in terms of growth rate or efficiency of feed utilization.

A close relationship has been found between the decomposition of feeds in the macro-respirometer and their digestibility. The degree of nitrogen mineralization appears also to conform with certain aspects of protein digestibility. The various relationships are sufficiently close to suggest that the macro-respirometer can be used in a preliminary assessment of the digestibility of feeds.