1. Twenty-four Merino ewes acclimatized to a hot environment were compared with twenty-four kept at normal temperatures, with respect to ovulation rate and embryonic loss by 25 days' pregnancy. Possible modifying effects of the three subsidiary factors, thyroxine level, vitamin A intake and progesterone level, were sought. The design of the experiment was a balanced factorial one.

2. While the differences between the hot-room and yard groups as a whole were not significant, in the former there were fewer ovulations, a smaller proportion of the potential embryos actually began to develop and, of these, a larger proportion had died by 25 days' pregnancy. Consequently only thirteen hot-room ewes contained live embryos compared to twenty in the yard; the total numbers of live embryos were fourteen and twenty-seven, respectively.

3. Of the subsidiary factors only thyroxine produced any marked effect. Both in the hot-room and in the yard the proportion of potential embryos developing and the proportion of actual embryos surviving at 25 days' pregnancy were greater where thyroxine injections were given. There appeared, however, to be no effect on ovulation rate. There was a significant increase in the proportion of hot-room ewes with live embryos due to thyroxine. Grouping hot-room and yard ewes together, thyroxine injections were associated with a significant increase in the proportion of potential embryos developing and in the proportion of actual embryos surviving; also, consequently, in the proportion of ewes with live embryos.

4. The results are discussed in relation to published work on the effects of high temperatures on reproduction.

1. From repeated fibre samplings and several skin biopsies on six Tasmanian Fine Merinos and eight Wiltshire Horn adult ewes variations in fibre diameter, fibre growth rate, and fibre regeneration or shedding frequency were measured over a period of 15 months. Slight differences were present in the treatment of the two breeds, but from the combined evidence of the live weights and fibre diameters maintained, it was concluded that these were negligible, that both breeds were under closely comparable conditions, and that their performance was at a moderately high and typical level for each breed.

2. In the Merinos fibre diameter (ca. 20 µ) fluctuated little during the period of observation, whereas in the Wiltshires it varied over a wide range from less than 40µ in winter to more than 80µ in summer. There were negligible differences between the three body regions, back, side, and belly, in the Merinos, but in the Wiltshires the belly grew markedly coarser fibres than the other two regions.

3. The fibre growth rate in the Merinos did not vary greatly from 7 to 8 mm. per 28 days throughout the period of observation or between the body regions. In the Wiltshires, fibre growth rate showed extreme variations from a minimum of about 3 mm. during the winter to a maximum of about 12 mm. per 28 days at the end of summer, with significant differences between the three body regions. However, in spite of these differences in the mode of growth, the total length of fibre grown per annum at the midside was approximately the same (10 cm.). Thus, were it not for fibre shedding, the Wiltshire Horn breed would grow a short-wool fleece.

The flock books of fourteen Lowland breeds of sheep were examined to study flock size, flock age, the number and source of rams used, the extent to which flocks differ in genetic importance within their breeds, the effect of geographical location on flock attributes, and changes in breed organization over a period of time.

All breeds taken together showed that 46% of the 2649 flocks involved had less than fifty breeding ewes and 15% had more than 200. 43% of flocks were less than 5 years old and 18% were over twenty. A third of all flocks used only one ram and 9% used five or more. All breeds were found to be arranged in a hierarchy such that only a small number of flocks in each breed supplied the majority of the rams and in particular the rams used by rambreeding flocks. The ‘top’ flocks were among the largest and oldest in each breed. Flocks in the ‘native’ region of each breed we e generally larger and older than those elsewhere, but for other flock attributes the differences between regions were more peculiar to breeds. The general pattern of breed organization appeared to apply at widely differing periods of time.

1. Four experiments in 1958 and five in 1959 compared responses to potassium (as combinedrilled muriate of potash) in the absence of nitrogen and in the presence of single and double doses of nitrogen (as broadcast sulphate of ammonia) on soils selected because they contained very little acid-soluble potassium.

2. Responses to 0·5 cwt. K2O/acre were obtained at six centres (two significant), but the effects of a further 0·5 cwt. K2O/acre were more variable and gains and losses (each at four centres) were almost equally balanced.

3. Gains from nitrogen were associated with previous cropping. N1 raised yields at seven centres (six significantly), but N2 raised yields further at only five centres (three significantly) and depressed yields significantly at three centres where barley followed a root crop or ley.

4. Potash did little to improve the strength of straw and therefore standing capacity in a wet season (1958) and had little effect upon the size of the grain, whereas nitrogen increased lodging and reduced the average size of the grain.

5. Increases in potassium uptake were associated with yield increases, whereas increases in nitrogen uptake were associated with both higher nitrogen percentage in grain and higher yields.

1. A procedure for fractionating the magnesium in fresh herbage into acetone-soluble, watersoluble and insoluble magnesium fractions is described.

2. Magnesium soluble in Analar acetone is shown to be virtually identical to chlorophyll magnesium, and generally represents less than 10% of the total magnesium.

3. Water-soluble material represents about 25% of the total dry matter, but contains more than 50% of the total magnesium when the herbage contains 0·2% or more Mg in the dry matter.

4. The fibrous material, which is soluble neither in acetone nor water, constitutes about two-thirds of the total dry matter, but has only about onethird of the total magnesium associated with it.

5. Highly significant correlations were found between total magnesium content and each of the three fractions, but regression coefficients showed that variations in total magnesium were largely reflected in the water-soluble fraction, the chlorophyll and fibre magnesium being affected to a much smaller degree.

6. Attention is drawn to the fact that at levels of pasture magnesium at which hypomagnesaemic tetany occurs in ruminants, water-soluble magnesium ceases to be the largest fraction and may be only about one-third of the total.

1. Three experiments are described in which dicalcium phosphate was fed as a phosphatic supplement to beef-type zebu cows and weaner calves grazing at Muguga in the Kenya Highlands.

2. The treatment caused an increase in the level of inorganic phosphate in the bloods only during times of drought, when it also caused an improvement in the condition of the cows. A slight beneficial effect on fertility was noted throughout the experiment.

3. Evidence was found that other nutritional factors were causing considerable variation and it is suggested that more attention should be given to improving the general level of nutrition of cattle during dry seasons.

Eggs were incubated at various frequencies of turning (tilting through 90°) and their hatchability compared with eggs incubated as controls at 24 turns per day evenly distributed throughout the 24 hr. The turning treatments were: 0, once in 2 days, 2, 6, 12, 48, 96, 144, 192 and 480 turns per day.

Differences in hatch of fertile eggs between the treated and control eggs at each level of turning were obtained and used to indicate the trend of hatchability in response to varying turning frequency and also the optimum rate of turning. This was observed to be 96 turns per day. Nil or few turns per day gave very poor results and at very high frequencies (up to 480x) hatchability decreased only slightly relative to the turning frequency.

Reasons were sought for the changes in hatchability associated with varying frequency rate observed in part I and by other workers. All deadin-shell from the hatches of part I were examined and classified into a number of categories. Their varying incidence in relation to the control hatches was taken to indicate the effect of the rates of turning investigated, viz. 0, once in 2 days, 2, 6, 12, 24 (control), 48, 96, 144, 192 and 480 turns per 24 hr. to the end of the 18th day of incubation.

At the observed optimum rate of turning (96x) mortality was reduced throughout the incubation period with the greatest reduction occurring towards the end; the incidence of malpositions and malformations was reduced as was the case of embryos with no obvious cause of death.

The observed decrease in mortality and hence increase in hatchability at the optimum rate of turning was attributed mainly to the probable improvement of the embryo's physiological environment.

1. The relative nutritive value to the unweaned calf of concentrates-with-hay and of grass cut from pasture in spring was measured.

2. No significant difference was found in liveweight gain or increase in body measurement between calves receiving these feedingstuffs.

3. There was some indication that rumen development, as measured by belly girth, may have been affected by the diet.

4. There was no interaction between the type of dry food consumed and the milk ration or housing conditions.

5. Results indicate that good quality grass, free from parasitic infestation, is capable of replacing hay and concentrates in the diet of the unweaned calf.

1. Calves which had been reared for 12 weeks on three milk feeds and either cut grass or concentrates-with-hay, were introduced to an all-grass diet when weaned.

2. Eight animals were kept indoors and fed herbage cut from paddocks grazed by nineteen similar calves.

3. After an initial period of about 2 weeks there was a tendency for grass-reared calves to make slightly better live-weight gains.

4. No difference could be shown in the intake of herbage dry matter by these groups of calves.

5. There was little indication that grass-reared animals digested their food more efficiently. It appeared that they converted grass to animal tissue better, but further study is required to substantiate this.

1. The effects of the addition of a non-ionic, anionic or cationic detergent to a diet containing 10% added fat on the digestibility of the protein, fat and carbohydrate have been studied.

2. The non-ionic detergent aided the digestion of fat, but protein and carbohydrate digestibility were unaffected.

3. An anionic detergent slightly, and a cationic detergent seriously, impaired the absorption of fat, and the cationic detergent also had an adverse effect on carbohydrate digestion. Neither affected protein digestion.

1. In the seasons of 1957 and 1958–59 a total of 130 ewe lambs were used to investigate the effects on growth and sexual development of high and moderate planes of nutrition during the rearing period.

2. The nutritional treatments imposed had significant effects on rate of growth; puberty occurred at an earlier age in high-plane than in moderateplane lambs. Also, in 1958–59, four moderateplane lambs failed to exhibit oestrus during their first winter of life.

3. Puberty occurred at a significantly lower live weight in moderate-plane than in high-plane lambs.

4. In lambs slaughtered after first oestrus, ovulation rate was not significantly affected by nutritional level, nor was the number of ovarian follicles greater than 2 mm. in diameter. However, high-plane lambs tended to have more follicles less than 2 mm. in diameter than moderate-plane lambs.

5. In 1958–59 the ovarian response to a subcutaneous injection of 800 i.u. of p.m.s. was investigated in half the lambs from each nutritional treatment. Injections of p.m.s. caused a marked increase in ovulation rate over the uninjected control level but there was no difference in response between nutritional treatments. Pregnant mare's serum did not alter the size distribution of ovarian follicles.

1. The distribution of calcium and magnesium in the contents of the reticulo-rumen sac, omasum, abomasum, small intestine, caecum and colon of the sheep was studied by means of ultrafiltration through collodion membranes.

2. In all organs except the abomasum considerable proportions of calcium and magnesium existed in a non-ultrafilterable form. In the abomasum where the pH is normally between 2 and 3 there was virtually no bound calcium or magnesium. The proportion of ultrafilterable calcium in the small intestine appeared to be dependent on the pH of the digesta, low pH values favouring higher proportions of ultrafilterable calcium. With magnesium this correlation was less obvious and appeared to be upset by unknown factors in the animals consuming a fresh grass diet.

3. From calculations it is postulated that the concentrations of ultrafilterable calcium and magnesium in rumen fluid are insufficient for these elements to be absorbed as freely diffusing ions, whereas in the abomasum and duodenum the concentrations of ultrafilterable calcium and magnesium are in favour of a net uptake from the gut.

1. Increasing the pH of abomasal contents of the sheep in vitro reduced the concentrations of ultrafilterable calcium and magnesium due to the binding of these ions to suspended material in the digesta. In the presence of this material such binding prevented the precipitation of calcium phosphate and magnesium ammonium phosphate which would otherwise have occurred about pH 6·0. Calcium and magnesium soap formation was eliminated as a possible factor contributing to the reduced concentrations of ultrafilterable calcium and magnesium.

2. At saturation the binding capacity of the material was greater for calcium than magnesium. Although some of the binding sites were common to both ions calcium was more strongly bound. The bound and ultrafilterable forms of both elements were in equilibrium.

3. The significance of these findings is discussed.

When synthetic amino acids are added to an allvegetable diet the amount of nitrogen eliminated in the urine is reduced and the nitrogen retained as tissue protein is correspondingly increased.

The requirements of the weanling pig for essential amino acids have been critically examined, the work involving both growth trials and nitrogenbalance determinations in the metabolism crates.

The addition of synthetic lysine and methionine to a low-protein vegetable diet had a striking effect on the thriftiness of the pigs. It is possible to secure almost as good growth and economy of food conversion on a cereal diet supplemented with as little as 6 % ex. soya-bean meal, when the amino acids are added in appropriate amounts, as is obtained on a similar diet containing sufficient white-fish meal to support maximum growth

The reproductive performance of 253 female Romney sheep of different ages has been studied from 1958 to 1960. Comparisons of the reproductive performance were made between ewes grazed on red clover pastures and ewes grazed on perennial rye-grass and white clover swards. The red clovers were oestrogenic during all periods of utilization.

The ingestion of oestrogenic red clovers caused the ewe lambs to accept the male before the start of the normal breeding season. No corpus luteum was found in the ovary of these lambs thus induced into oestrus. The subsequent reproductive performance of these ewe lambs at 2 years of age was not affected. The oestrus per se or the regularity of oestrus of the young (1½-year-old) or the aged (5½-year-old) ewes was not affected by the diet of oestrogenic red clover.

The ingestion of oestrogenic red clover did not affect the reproductive performance of the young ewes at 2 years of age, but did cause a protracted lambing season and a reduced level of lambing performance in the aged ewes at 6 years of age. No endometrial cyst was found in the aged ewes. It was suggested that the reduced level of reproductive performance of the aged ewes could have resulted from an unfavourable environment within the ewe, for the process of fertilization or implantation of the fertilized ova during the breeding season.

A factorial experiment designed to determine the time of ovulation relative to oestrus and to the cessation of progesterone treatment in cyclic maiden ewes, and subsequent fertilization of ova, is described. Seventy-two ewes were used. Factors were: (a) type of service (natural v. A.I with fresh undiluted semen v. A.I. with semen diluted 1:1 with heated cows' milk); (b) frequency of progesterone (daily v. every 2 days); (c) post progesterone withdrawal treatment (500 i.u. PMS v. no PMS); (d) week of treatment (3 successive weeks); and (e) days within weeks (2 successive days). Insemination was carried out on the third day after cessation of progesterone without reference to the results of teasing with vasectomized rams.

Progesterone (20 mg.) administered every 2 days was as effective as 10 mg. administered daily for suppression of ovulation. PMS resulted in a highly significant increase (P < 0·001) in the numbers of ewes which ovulated and which exhibited oestrus after progesterone, and in the number of fertile ewes (P < 0·05).

There was a considerable spread of time of onset of oestrus and of ovulation. This was unaffected by any treatment. Most ewes were served 24–96 hr. (peak 48–84 hr.) and ovulated 48–108 hr. (peak 72–108) after cessation of progesterone. The time relationships of oestrus, ovulation and ovum transport appeared normal.

A factorial experiment is described in which seventy-two spayed crossbred ewes were used in four successive tests at intervals of 15 days in a study of factors affecting the detection of oestrus. Variates introduced in each test were: (a) number of rams to eighteen ewes (one or three); (b) size of mating paddock (17 acres or ⅕ acre); (c) dose of oestrogen (oestradiol benzoate, ODB: 10·0, 15·6, 24·4 μg.).

All ewes were primed with progesterone for 12 days prior to ODB injection and joining. The number of ewes detected in oestrus and the mean number of ewes served per ram were recorded.

In the four successive tests, thirty-two, fortyseven, forty-six and forty-one ewes were served (P < 0·05). Three rams working together detected ninety-eight ewes in oestrus while rams working individually detected sixty-eight (P < 0·001). Size of mating paddock had no significant effect (17 acres, 89; Jacre, 77).

The mean number of ewes marked per ram when used singly was indistinguishable from the mean number when rams were in groups of three (8·5 and 9·3). This resulted in multiple coverage of oestrous ewes when group joined (average 2·3 rams per ewe).

A factorial experiment is described in which thirty-six aged and thirty-six maiden spayed crossbred ewes were used in four successive tests at intervals of 15 days in a study of factors affecting the detection of oestrus. Variates introduced into each test were: (a) freedom of rams (free or tethered); (b) size of mating paddock (17 acres or ⅕ acre); (c) age of ewe (maiden or aged); and (d) dose of oestrogen (oestradiol benzoate, ODB: 10·0, 15·6, 24·4 μg.).

All ewes were primed with progesterone for 12 days prior to ODB injection and joining. The number of ewes detected in oestrus and the number and identity of rams which served each ewe were recorded.

In the four successive tests 29, 33, 36 and 30 ewes were served.

Significant main effects were: (a) freedom of rams—free 77, tethered, 51 (P < 0·001); (b) size of mating paddock—17 acres 49, ⅕ acre 79 (P < 0·001); (c) age of ewes—aged 57, maiden 71 (P < 0·05); and (d) dose of ODB—10·0 μg., 20; 15·6 μg., 41; 24·4 μg., 67 (P < 0·001).

Significant interactions were: (a) test number × age (P = 0·01), and (b) test number × dose of ODB (P < 0·05). The number of maiden ewes served increased and that of aged ewes decreased withsuccessive tests. There was a barely significant ohange in the slope of the ODB D/R line.

Ewes showed no obvious preference for tethered rams of any particular breed. There was a positive correlation between the performance of rams when free and tethered.