1. Unlike many other mammals, the calf is capable of responding to pituitary injections almost from birth. Age has little effect on the ability of the follicles to develop during a series of a.p.h. injections, the follicular response generally being as good 3 weeks after birth as in calves 6–8 months old.

2. Ovulation can occur spontaneously in the a.p.h. treated calf before the end of the first month of post-natal life.

3. Ova obtained from such ovulations are capable of fertilization, although the percentage becoming fertilized is very low. This is thought to be due to the infantile state of the Fallopian tube and the difficulty in inseminating into the uterus, rather than faulty maturation of ova.

4. Although many follicles (10–60) can develop during a series of a.p.h. injections, superovulation was not consistently obtained either by intravenous injections of a.p.h., l.h. or p.u., or combinations of any of these three.

5. Superovulation can generally be obtained, with the formation of many corpora lutea, if the a.p.h. treatment is repeated a second time after a period of luteal activity.

6. The inhibitory effect of a corpus luteum on ovulation in cattle can be overridden in tho a.p.h. treated animal if suitable quantities of a.p.h., l.h. or p.u. are intravenously injected when the newly formed follicles are approaching maturity.

7. Ovulation in the calf at all ages up to 8 or 9 months of age, either in the presence or absence of luteal tissue, is unaccompanied by oestrus. Oestrus, when occurring during a series of a.p.h. injections, commenced after 90–100 hr. of treatment. In such cases slaughter has always revealed the presence of luteal tissue, indicating that ovulation during a ‘silent heat’ had occurred before the commencement of pituitary treatment.

8. Great individual variation exists in the ability of the ovary to respond to pituitary injections. This insensitivity to gonadotropins is not confined to young calves and has been observed in calves 4–6 months of age.

Records for milk, fat, solids-not-fat and fat percentage over forty-eight complete lactations were used as uniformity data to determine the relative efficiencies of a variety of experimental designs used in dairy husbandry experiments.

In general, it was found that:

1. Experiments conducted during the earlier part of the lactation are more efficient than those conducted during the later part.

2. Three-weekly periods are generally more efficient than 5-weekly periods.

3. If 3-weekly periods are used, then extending the time of the experiment over four such periods instead of three reduces the error. The converse is the case with 5-weekly periods since the experiment is carried over into the highly variable later part of the lactation.

4. Grouping the animals according to the yields recorded during the first 40 days of lactation does not appear to reduce the error.

An analysis of covariance using the pro-experimental records of the performance of the animals has been carried out on ordinary group trials and it is hoped to publish the results at a later date, but investigations on the data have shown that both reversal and Latin square designs are more efficient than ordinary group trials even when such an analysis is performed.

The normal course of mammary development has been briefly described, in sheep from 2 months of foetal age to 4 months after birth; and in dairy cattle from the 3-month foetus to calves 6 months old. Observations were also made on a series of udders from ewes during their first pregnancy. A small group of beef calves and a number of freemartins of various ages were also examined.

Development was found to be closely similar in the two species, and in both, sex differences were marked.

Experimentally it was found that in males of either species castration at birth had little effect on mammary growth, while prolonged treatment with oestrogen gave rise to enlarged teats, dilated cisterns and ducts, and to a certain amount of secretion. Little gland tissue was formed in oestrogen-treated males, and there was no increase in the spreading of mammary tissue from the neighbourhood of the teat.

Females of the two species showed a striking difference in their response to experimental treatment. In sheep, removal of the ovaries at birth had no apparent effect on mammary development up to 4 months, while treatment with oestrogen stimulated gland formation in both spayed and intact lambs and also restricted the normal spread of mammary tissue into the udder. In cattle, on the other hand, heifers spayed at birth showed almost complete cessation of mammary development, while implants of oestrogen, in addition to inducing gland formation, promoted the spreading of tissue into the udder pad of the spayed animal.

Udder development of freemartins appeared to be similar to that of normal heifers from 5 months foetal age to about a month after birth, but thereafter was more like that of a spayed animal. Removal of the abnormal gonads shortly after birth had no effect, while oestrogen treatment induced development of teats, ducts and glands exactly as in a normal heifer.

Comparing small numbers of calves of the two types, it was found that heifers of the beef breed in general showed slightly poorer mammary development than dairy heifers that had been treated in the same way, with more connective tissue and numerous leucocytes in the mammary zone.

The follicle population of the Blackface breed (‘double-coated’) was followed in skin samples taken from four lambs at eight intervals between 3 days and 43 weeks of age. The follicle population differs greatly from that of the Romney and Leicester breeds previously studied (Burns, 1949).

1. At 1 month old the secondary/primary follicle ratio (S/P) was slightly lower than the Leicester and much lower than the Romney, and the difference became accentuated with age.

2. Fewer secondary follicles are developed after birth than in the Leicester or Romney, although the period during which they can be developed is longer, extending at least to 12 and possibly to 17 weeks after birth.

3. The follicle density is less than half that of the Leicester, but the difference in S/P ratio is not sufficiently large to account for this, which is mainly due to the Blackface having a much lower density of primary follicles at birth.

4. The possibility is suggested that the secondary follicles arise as a result of ‘induction’ by ‘follicle organizer’ coming from primary follicles in a quantity which decreases with advancing age. It may be that when the primary density is high the areas affected by organizer from each primary overlap, providing sufficient organizer to permit of numerous secondary follicles developing at a late post-natal stage, as reported in the Merino.

5. The Blackface contrast with the other breeds in that its primary follicles are conspicuously larger than its largest secondary follicles. All primary fibres are medullated except when about to shed, but many secondary fibres are free of medulla. Kemps are produced only by primary follicles, some of which however produce long ‘hair’ fibres.

6. Many fibres which grow strongly medullated fibres during summer change to the production of non-medullated fibres in winter. The shedding of the kemps in spring should probably be looked upon as physiologically an autumn moult, since the fibres cease growth and produce ‘brushes’ during the autumn.

1. A survey of the trade in fat cattle, calves and sheep through the collecting centres of the Ministry of Food has been made for the counties of Anglesey and Caernarvon.

2. The results show that the Anglesey stock are invariably heavier and in better condition and marketed slightly earlier in the year, than those of Caernarvon.

3. The imported fat cattle were heavier and more uniform than the home-bred.

4. A check has been made of the variations in live-weight of fat cattle according to colour. Invariably the Black cattle (Welsh) have been lighter, and the Red/White (Hereford) heavier than the average live weight of all cattle of both sexes.

5. The bulk of the meat produced in the two counties is delivered during the autumn months, confirming the experience that the winter fattening of cattle is not now widely practised.

6. In sheep husbandry the two counties are complementary. The small draft mountain ewe, crossed with a heavier type ram, is capable of rearing a fat lamb practically equal to her own body weight in less than 6 months.

7. Losses in mature ewes and rams are suspected to be high because of the small proportions of them, in relation to the population figures, that are delivered to the collecting centres.

The survey shows that objective estimates of the yield of maincrop potatoes can be obtained from small samples carefully selected and dug by hand. Samples taken from about 1000 fields gave estimates of the mean yield of all counties sampled with a standard error due to sampling of less than ± 0·2 ton/acre. The precision of the estimate could have been improved by a better distribution of samples among counties.

The results point to underestimation on the part of the official estimates, in each of the 3 years, especially in the case of high yields in particular counties, and in particular years. The discrepancy between the official and the survey yields is of the order of 1¾ tons/acre, after all necessary corrections have been applied to the survey yields.

The experience gained in the survey indicates that the method of sampling adopted provides an accurate and reliable method of estimating the yields of potatoes which could supplement, and, possibly, ultimately replace the present official estimates if more accurate estimates are required. A national scheme, properly designed, which would include all the potato-growing areas in due proportion should not be unduly expensive to operate. Estimates so obtained would not only be generally more accurate than those obtained by the present official method, but, perhaps more important, would indicate far more closely the fluctuation in yield from year to year.

The weight, length and quality (fineness) of wool produced at different times of the year and under different nutritional conditions has been determined over a period of three years by clipping at monthly intervals the wool grown on delineated skin areas of sheep. The treatments consisted of

(a) wet ewes, grazing on pasture all the year, subjected to high and low levels of feeding during the ‘dry’, pregnancy and lactation periods;

(b) dry ewes and lambs fed differentially on grazing during the winter and spring;

(c) wet ewes fed in stalls on a diet of constant composition at rates sufficient to maintain constant effective body weight (i.e. making allowance for pregnancy increase and fleece weight increase). A small number of these ewes was also subjected to increased environmental temperature during the winter.

The experiments have shown the existence of a marked seasonal rhythm in wool growth having a maximum in January (midsummer) and a minimum in July (midwinter). Changes in weight of wool grown are caused by sympathetic changes in both length and diameter. At the same level of feeding the rate of wool growth in midwinter is about onethird of that in midsummer.

The nutritional demands of pregnancy reduce the rate of wool growth in winter and those of lactation delay the rise in production in spring. Nutrition also plays an important part in determining the time of the maximum and minimum. In dry sheep the maximum tends to occur before midsummer when pasture growth is at its best, but lactation in wet sheep prevents the expression of a maximum early in the summer, so that in these ewes it generally occurs after weaning, and therefore after midsummer. The level of nutrition also determines within limits the magnitude of the maximum and minimum.

The fundamental cause of the seasonal rhythm of wool growth remains obscure. Nutrition, pregnancy and lactation can modify the rhythm, but it exists strongly even when variations due to these are eliminated. The seasonal rhythm of solar radiation has recently been shown to influence rate of wool growth, particularly during winter, and though this is undoubtedly one factor it is not the only one. Temperature has been suggested elsewhere as a possible cause, but the experiments described do not support the theory that environmental temperature has any direct effect on wool growth. It is suggested, however, that the seasonal rhythm of temperature may be a second factor.

1. A rapid extraction procedure of dried and ground plant material has been used in conjunction with the Lundegårdh flame method of spectrographic analysis. The accuracy of the analysis has been estimated, and the method has been shown to be comparable with ashing and gravimetric analysis.

2. The effect of fertilizer treatment on yield and on the nutrient composition of the crop has been outlined. The changes which occurred in the period

1852 to 1921 have been summarized by linear regressions fitted to 10-year means.

3. The recovery of potassium was estimated, and the exhaustion or accumulation of potassium was shown to be related to exchangeable potassium in the surface soil.

4. Sodium and magnesium sulphates used as fertilizers were shown to increase crop yield by increasing the potassium supply to the crop. It has been shown that the extra potassium came from non-exchangeable forms.

1. In the summer of 1945 samples of the growing crop were taken from eight Broadbalk plots. On all the plots the concentrations of nutrients in all parts of the plants decreased during growth. The compositions of the roots and stems and leaves varied with fertilizer treatment at all times of the season. The nutrient composition of the ears was only slightly affected by fertilizer treatment.

2. The total uptake of nutrients by the crop increased to a maximum and then decreased. The losses of potassium and magnesium from the stems and leaves were particularly large, due to translocation into the ear but there were also net losses of potassium and calcium from the whole plant.

3. The changes which occurred were similar on all plots and the effect of fertilizer treatment on plant composition was always related to the effect at harvest. There was no evidence that the composition of the crop at harvest differed radically from the composition earlier in the season.