1. Four groups of four calves were given rations containing adequate and inadequate amounts of magnesium, both with or without an excess of potassium, added as potassium chloride.

2. The excess of potassium resulted in the death of three of the eight calves, the clinical signs observed before death being cardiac insufficiency, oedema, severe muscular weakness and muscular atony. The excitability of motor nerves, measured by the method of Kugelberg (1944), was reduced by excess dietary potassium and the serum concentration of potassium was increased. The potassium content of the erythrocytes declined with age, irrespective of dietary treatment.

3. Although this evidence of potassium intoxication was obtained, no concomitant abnormalities were induced in magnesium metabolism by the excess of potassium whether or not the calves received rations containing adequate or inadequate amounts of magnesium.

4. Excess potassium had no effect on the concentration of potassium or magnesium in the muscle or on the Ca : Mg ratio in bone.

5. Magnesium deficiency resulting in tetany was shown to have no statistically significant effect on the intracellular concentration of magnesium i n the muscle. A very small drop in erythrocyte magnesium was noted. No effect on the excitability of motor nerves was observed.

6. The results suggest that the effect of excessive manuring of pastures with potassic fertiliser in increasing the incidence of hypomagnesaemic tetany is not due to a direct effect of potassium on the magnesium metabolism of the animal.

1. Two experiments were made. In Experiment 1, 124 ram, wether and ewe lambs were allocated to four equal groups as they reached a live-weight of 30 lb. Group A received no hexoestrol; group B were implanted with a 15 mg. pellet of hexoestrol and lambs of group C were given a second pellet of 15 mg. 35 days after the first. Group D were implanted with three 5 mg. pellets simultaneously in three different sites. The lambs were creep-fed while running with their dams on pasture and were killed as they reached a live-weight of 95 lb.

In Experiment 2, 20 weaned ram lambs were allocated to a hexoestrol-implant group or a control group as they reached a live-weight of 40 lb. They were fed a pelleted ration indoors and were slaughtered at a live-weight of 110 1b.

2. Length of teats and weight of the pituitary were significantly increased for all lambs treated with hexoestrol as compared with their controls. Excessive mammary development and one case of rectal prolapse were observed i n treated ewe lambs, while 3 of the treated rams in Experiment 2 had scrotal oedema.

3. The rate of live-weight gain was greater for all hexoestrol-implanted lambs in Experiment 1 but less for the implanted lambs on Experiment 2 as compared with their respective controls. The differences just failed to attain significance at the 5% level.

4. Dressing percentage was significantly reduced by hexoestrol treatment i n Experiment 1. On the other hand treated ram lambs in Experiment 2 had significantly higher dressing percentages and appeared to be fatter than the controls.

5. Weights of testes and seminal vesicles in the ram and of the ovary in the ewe were decreased by hexoestrol treatment. Weights of seminal vesicles in the wether and of oviducts and uterus in the ewe were increased.

In an initial experiment, cattle receiving 5 mg. hydroxyzine dihydro-chloride daily gained 12·7% faster and manifested 12·0% better feed conversion ratio than the control, but these effects were not statistically significant under the conditions of the experiment. Carcass quality and endocrines were not affected by hydroxyzine feeding.

1. 2-week-old calves previously fed whole milk were changed abruptly o t skim milk which had been treated with formalin to give a final concentration of 0·1% of the preservative.

2. Difficulty was experienced in accustoming the calves to drink such formalin-treated milk and scouring invariably occurred within two days of the changeover.

3. Post-mortem and histological examination of calves fed formalin-treated skim milk showed severe damage to the alimentary tract compatible with clinical symptoms.

4. None of the above findings was apparent in control calves fed untreated skim milk.

1. A survey of management practices associated with the self-feeding of silage was carried out on a group of 130 farms during the winter of 1958-9.

2. The majority of farmers housed their cows in covered yards and allowed them free access to silage stored in a roofed surface clamp.

3. An average of 56 square feet per cow of covered yard and, under free access, 9·7 inches of face width per cow were allowed.

4. The average estimated consumption of silage over the whole feeding period was 2·12 cubic feet per cow per day. Where the feeding face was lit at night, the estimated silage consumption was 0·27±0·10 cubic feet per cow per day more than on other farms. There was also a suggestion that on farms where hay and/or straw was fed, the consumption of silage was less than on the remainder.

5. Levels of milk production were similar and concentrate feeding were slightly lower than those found in National Milk Recorded and Private Milk Recorded herds.

1. The four systems of rearing dairy heifer calves, described in Part 1 of this series are now studied for their effect on absolute and relative growth rates to maturity.

2. Data on live-weights and measurements and the percentages of mature size attained by these at 44, 80, 104, 132, 182, 260 and 312 weeks of age are tabulated.

3. In all groups the measurement to reach maturity earliest was circumference of metacarpus followed in order by length of back, height at withers and width of hooks.

4. By 6 years of age all groups had attained approximately the same body size. Maturity in the LL group in terms of four skeletal measurements was delayed by only 9 months, and in the case of HL and LH animals by 5 and 4 months respectively.

5. All groups showed the same general pattern of relative growth but the effect of restricted feeding was to increase at the younger ages the difference i n percentage of mature size between early and late maturing measurements. After 44 weeks of age the rate of growth was most rapid in those measurements which were furthest from maturity then.

6. The rate of tissue deposition was markedly increased in high plane animals during early pregnancy compared with low plane. Evidence is presented to show that much of this was lost during lactation.

7. At first oestrus, animals in all four treatment groups had reached the same percentage of mature size for each body dimension (except for length of back in the LL group).

8. From data on 5 animals it is shown that although growth in height at withers and length of back ceased by 6 years of age there was slow but continuous growth in live-weight, middle and heart girths and width of hooks to 9 years of age.

Vertebrae counts made on 504 Large White and 550 (Wessex × Large White) pigs showed an association with carcass length but not with other carcass traits. For each additional vertebra there was an increase in length of approximately 15 mm.

Another group of 313 piglets from 36 litters were X-rayed at around 9 days of age in order to predict their ultimate carcass length. After correction for sex and variations in weight at slaughter it was found that the number of thoracic and lumbar vertebrae together accounted for 14% of the remaining variation in carcass length. Improved accuracy of prediction, accounting for 29% of the variation was obtained with a multiple regression equation using as independent variables: the skeletal length of the young pig as measured on its radiograph, its weight at birth and X-raying and the number of lumbar vertebrae. From measurements made on the carcass it i s suggested that X-raying of the bacon pig to measure the length of the first four lumbar vertebrae, would, in conjunction with an earlier determination of vertebrae number, enable a much improved prediction of carcass length to be made.

The incidence of various vertebral variations is noted and in particular the occurrence of one pig with only six cervical vertebrae.

1. A comparison has been made of 305-day lactation milk yields and butterfat percentages of twin and single-born cattle under experimental and field conditions. Experimental two-egg twins, as judged from within-pair variances, were four times as variable as one-egg twins. Two-egg twins in the experimental herd were more alike than twins in dairy herds in fat percentage due to more frequent butterfat testing. Variance of milk yield within pairs was the same in both experimental and farm twins.

2. Twins and half sisters in dairy herds had similar within-pair variances for milk yield and fat percentage. Full sisters, of necessity non-contemporary, differed more in yield than twins and half sisters; significantly so in the latter comparison.

3. The between-pair variance components for experimental twins were high, relative to twins in herds. In experimental twins, breed differences, lack of culling and uniform treatment were probably contributing causes, and also more frequent observation of fat percentage during lactation. Twins n i dairy herds had greater between-pair variances than full sisters.

4. Experimental MZ twins had an intra-class correlation for milk yield of 0·88 and DZ twins of 0·67 which was much higher than for twins on farms. Farm twins and half sisters had correlations for milk yield of 0·37 and 0·31, to be compared with 0·20 in full sisters. Corresponding values for fat percentage were 0·40, 0·35 and 0·25 on farms as against 0·88 and 0·65 for MZ and DZ twins at the experiment station. These differences between experimental and commercial pairs were largely attributable to differences in between-pair variance.

5. There is no evidence from experimental or commercial data that twins produce less milk than single-born cows.

6. Differences between farms increased the within-pair variance in yield and decreased the intra-class correlation of twins and half sisters but had less effect on full sisters.

An analysis was made of the effect of inbreeding in Sardinian sheep from the records of 658 single female lambs born in the Monastir flock in the years 1935–42 and 1947–55.

The calculations of differences between inbreds (both 12·5% and 25%) were done within recording years. The results showed that inbreeding had no significant effect on birth weight or 30-day weight.

The effects on average daily gain of a 12 mg. implant of diethylstilboestrol has been tested in male suckling lambs and in male hoggets. In both types stilboestrol produced some mammary stimulation. One case of rectal prolapse was encountered in the hoggets. In suckling lambs, treatment did not significantly increase rate of gain nor significantly affect any of several carcass characteristics studied. In hoggets, treatment produced a highly significant increase in rate of gain (33%), a highly significant increase in pelt weight and a highly significant decrease in the percentage of fat in the last rib section. It produced a non-significant increase in muscle and bone in the last rib section. Carcass score and dressing percentage were not significantly affected by treatment.

The oral administration of L-thyroxine to suckling female lambs from 30–70 lb. live-weight did not significantly affect the rate of gain or the carcass characteristics studied.

The use of the hormones, diethylstilboestrol, hexoestrol and testosterone propionate, as growth stimulants in beef cattle has been studied.

The subcutaneous implantation of 60 mg. stilboestrol into steers fattening in yards produced a highly significant increase in rate of gain (65%) and little difference in the yield and quality of the carcass. The implantation of 24 nig. or 36 mg. of diethylstilboestrol or 30 mg. hexoestrol into Friesian bullocks fattening on pasture produced highly significant increases in rates of gain (29%, 48% and 33% respectively). No significant difference was found in the rates of gain produced by these three treatments.

The oral administration of 10 mg. diethylstilboestrol per head per day for 168 days or the oral administration of 20 mg. rising to 40 mg. testosterone propionate per head per day for 154 days to dizygotic twin steers on equal feed intake significantly increased rate of gain by 15% and 21% respectively Feed efficiency as measured by the pounds of feed required to produce a pound of gain was significantly improved by both treatments. Carcass yield and carcass quality were not significantly affected by either treatment. No significant differences were found between the two treatments.

Examination of the thyroid and adrenal glands of treated and untreated steers revealed no consistent changes in size due to treatment. The gonadotrophin and thyrotrophin content of the anterior pituitary glands of treated and untreated cattle were compared using the male chick bioassay. The results showed that a lower gonadotrophin content was not a factor associated with the extra growth due to treatment, but in two out of three experiments there was some evidence that sex-hormone treatment leads to a mild hyper-thyroidism which, in turn, resulted in a decrease in the thyrotrophin content of the anterior pituitary gland. It was concluded that hyperactivity of the thyroid gland was probably more important in accounting for the extra growth than hyperactivity of the adrenal cortex.