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.

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.

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.

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.

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.

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.

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.

Groups of Dorper lambs were castrated at three ages: shortly after birth, and at two and four months of age. All were slaughtered at an age of six months and the carcasses subsequently weighed, graded, measured and scored. The results indicate no marked differences in either weight or quality of carcass between the treatments. It is concluded that the operation can safely be carried out, depending upon circumstances, at any stage between birth and four months.

Using extensions to Robertson's (1957) method for finding the optimum test design, factors affecting the improvement from testing were studied. Other than the heritability, the ratio of the number tested (N) to the number required for breeding stock (T) has the largest effect on the improvement expected, the improvement being roughly proportional to the logarithm of this ratio. The type of family and the number in the test group which compose the optimum design, also depend largely on the ratio N/T. Accuracy in evaluation is required when only few animals are selected (N/T high), but small test groups from large families are necessary when large numbers of breeding stock are required (N/T low).

Testing schemes differ basically in their selection procedure and only secondarily in their designs. The advantage resulting from the tested animals being themselves selected is in proportion to what part they constitute of the total selected.

Another consideration is how the testing is integrated with the population breeding structure. Maximum improvement will be obtained if the testing facilities are restricted to a nucleus group of breeders, and full opportunity for selection is made in their stocks. The increased improvement this providesis accumulated in this nucleus group of herds and gradually passed down to the rest of the herds. Otherwise the improvement will be greatest when each breeder can use sires from families which have performed well in thetesting.

1. Eighteen pairs of one-egg and 6 pairs of two-egg twin calves were used in a balanced incomplete block design to examine four systems of rearing: (1) a continuous high plane of nutrition from birth to first calving (HH); (2) a high plane for the first 44 weeks followed by a low plane until 2 months before calving (HL); (3) a continuous low plane until 2 months before calving (LL); and (4) a low plane to 44 weeks followed by a high plane to first calving (LH). All animals were fed on a high plane during the two months before calving.

2. Mean daily consumptions of DM, TDN, S.E. and DCP are given and the net energy intakes compared with a recently recommended standard.

3. At 44, 80 and 104 weeks of age there were highly significant differences between the groups in all weights and measurements due to treatment. Low-plane feeding retarded the growth of the skeleton to only a limited extent as compared with live-weight. After the changeover, animals on the HL system lost much of the advantage in body measurements they had gained over those fed on a continuous low plane.

4. All groups reached sexual maturity at the same stage of physical development but at different ages. The HL animals were the slowest to attain maturity indicating that as with growth the changeover from a high plane to a low plane of nutrition had had an adverse effect.

5. Low-plane animals on poor hill pasture made better growth than their mates on good arable pasture. Evidence is presented, however, to show that part of this greater growth in live-weight was due to increased ‘fill’.

Carcass measurements made on 1,463 Large White pigs from 88 inbred lines, at various degrees of inbreeding, have been analysed.

Partial regression coefficients calculated within lines showed that each 10% increase in inbreeding coefficient significantly increased carcass weight by 0·46 lb., decreased mid-back fat thickness by 0·37 mm. and streak thickness by 0·36 mm.

Partial regression coefficients calculated on all the material, or on line means showed, however, that the most highly inbred pigs tended to be shorter and fatter than average. Possible explanations of this finding are discussed and it is suggested that under the selection procedure adopted for litter size and weaning, weight favours the survival of these less desirable lines.

A simple but approximate method of pedigree evaluation is presented with particular reference to dairy cattle. It involves the expression of information available on any animal in the pedigree in terms of the equivalent number of ‘standard progeny records’. Formulae are given for the transfer of evidence from generation to generation within the pedigree. The application to one rather complex pedigree is illustrated and it is shown that the loss of information through the approximation is small.

1. Data from 208 piglets in 24 litters were examined to evaluate the relationships of weights at 3 and 8 weeks with birth weight and milk consumption within litters, and with these and creep-feed consumption between litters.

2. Of the total variation in 3-week weight within litters, 39% was associated with variation in birth weight, 67% with variation in milk consumption to 3 weeks, and 80% with these two factors combined. Of the total variation in 8-week weight within litters, 30% was associated with variation in birth weight, 25% with variation in milk consumption to 8 weeks, 42% with these two factors combined and 45% with variation in 3-week weight.

3. Of the total variation in 3-week weight between litters, 6% was associated with variation in birth weight, 15% with variation in milk consumption to 3 weeks, and 18% with these two factors together. These values were all too low to be statistically significant, as were the equivalent relationships with 8-week weight. Of the total variation in 8-week weight between litters, 77 % was associated with variation in creep-feed consumption to 8 weeks, 70% with variation in 3-week weight, 85% with consumptions to 8 weeks of milk and creep-feed combined, and 89 % with creep-feed consumption to 8 weeks and 3-week weight combined.

4. The practical significance of these relationships is discussed.

1. The area of eye muscle cross-section of beef carcasses may be accurately measured by tracing the boundary and measuring the tracing with a planimeter. Taking a single area measurement from each of duplicate tracings increases the accuracy by some 30%. If a planimeter is not available, the area may be estimated by superimposing a grid on the tracing and counting squares; although this method is some 25% less accurate than the planimeter method it is sufficiently repeatable for experimental use.

2. Area estimated by combinations of linear measurements is highly repeatable, but predicts true area with insufficient accuracy for experimental use. The standard error of prediction is about 7% of the mean area. Regression equations relating planimeter area and combinations of measurements for various cuts and animals are given.

Blood samples from 262 Polish Red Cattle, 9 Danish Red Cattle and 123 cattle produced by crossing were examined for the presence of 45 erythrocyte antigenic factors.

The frequencies of most of the factors are given and estimates are made of the appropriate gene frequencies within the Polish Red breed as a whole.

Segregation of 42 B alleles was observed of which 9 have not previously been reported. The H′ factor hitherto recorded as marking an independent system is assigned to the SU system on genetical grounds and renamed S2.

It is concluded from the blood group data that the Polish Red breed has signs of a genetic relationship with Holstein-Friesian, Brown Swiss and Guernsey breeds but the relationship with the Danish Red breed is closer. The existence of the new alleles distinguish the Polish Red breed of cattle from all others investigated.

The relationship of six-month weight of sheep to their subsequent performance has been studied in a Scottish Blackface flock. The various aspects of performance considered were—live-weight of the ewe at tuppings, mortality and culling rates, fleece weight, lambing and weaning percentages and weight of lamb weaned. The regressions of these characteristics on sixmonth weight all declined with increasing age of the sheep and in any case only tupping weight, fleece weight and weight of lamb weaned had an association which was statistically significant. The results for each year of life of the sheep (up to drafting age at 6½ years) were subsequently combined to show how the total production of a flock of 1,000 ewes was related to the weight of the hoggs.