Stylosanthes humilis was grown at Brisbane at densities of 10, 50, 250, 850 and 3800 plants/m2 in boxes of sand which received basal nutrients, applications of 0, 10 and 50 kg P/ha as calcium dihydrogen phosphate, and frequent irrigation.

Maximum seed yield was 69 g/m2 at a density of 850 plants/m2. Seed yield was linearly related to the logarithm of density up to 250 plants/m2, and was comparatively stable over the upper density range, declining slightly at supra-optimal density. Inflorescence density exerted the primary control over seed yield, but seed set per floret and floret number per inflorescence were also influential.

The application of 50 kg P/ha increased yield of plant tops by 54% and seed yield by 20%.

The nitrogenous composition of the water soluble, non-protein nitrogen fractions of three samples of high-pH-spoilt silage and one sample of overheated silage were examined in detail. The amino acid nitrogen content of the high-pH-spoilt silages declined with increasing extent of spoilage, due to a selective degradation of the amino acids. Losses of amino acids were associated with proportionate increases in the amount of volatile basic nitrogen. Lower aliphatic amines were not present and it was therefore concluded that the ultimate end product of nitrogen metabolism in high-pH-spoilt silages was ammonia. Only low concentrations of putrefaction products, such as putroscine, cadaverine and histamine were present.

The composition of the non-protein nitrogen fraction of the overheated silage was unusual in that the ammonia nitrogen content was high and associated with the complete destruction of certain amino acids. The free amino acid nitrogen content was low but this was partially compensated for by a very high ‘peptide’ nitrogen content. There was no evidence of putrefaction products in this silage.

The oestrous response and subsequent lambing performance of 264 sheep was studied after treatment with intravaginal sponges and PMS during July (period of late anoestrus). Four progestagen treatments were employed, each in combination with one or other of four dose levels of PMS (0, 250, 500 and 750 i.u.) given at pessary withdrawal; the sixteen resultant treatments were applied in each of seventeen flocks. Modification of standard ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterono; G. D. Searle) pessaries to ensure thorough dispersion of the compound resulted in a significantly higher mating response and lambing outcome. The highest lambing outcome followed the use of 500 i.u. PMS. The onset of heat, relative to progestagen withdrawal, was affected both by progestagen treatment and PMS dose level. The conception percentage was highest in sheep which were bred on the second day after treatment. The implications of the data, in explaining some previous results with standard ‘Cronolone’ sponges, are briefly discussed.

The mating response and lambing outcome was studied in 584 sheep in twentyeight farm flocks after treatment with progestagen impregnated intravaginal sponges and PMS during June/July (period of late anoestrus). Each pessary carried a dose of 30 mg ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterone; SC-9880, G. D. Searle) in finely dispersed form; half the number of pessaries carried an additional dose of 400 mg progesterone. Intravaginal treatment was for 12 days; a single intramuscular injection of 500 i.u. PMS (Burrough's Wellcome) was made at pessary withdrawal. Breeding was by natural service, using 10% rams. The response was 98·8% bred in the 4 days after treatment, 61·2% conceptions in those served and an average of 1·65 lambs/conception. This resulted in the birth, within the period of about 1 week, of 100 ‘early’ lambs for every 100 ewes exposed to rams. The addition of 400 mg progesterone to pessaries or the injection of a dose of 5 mg progesterone at sponge withdrawal did not improve response beyond that found with ‘Cronolone’ alone.

Seventy-nine pregnant Merino ewes grazing pasture at two intensities were slaughtered in groups at intervals from 60 days after conception to post-partum. Sixty-one nonpregnant ewes were also slaughtered. The weights of various organs including uteri and their contents were recorded and the energy content of each ewe was determined.

The weight of uterine contents (conceptus) increased rectilinearly with increasing foetal age to 100 days: differences between singles and twins were not significant. From 100 days to term, the relationship was also rectilinear but the slope was greater: a more rapid increase occurred with twins than with singles (P < 0·05). The nutritional difference imposed did not affect the relationship.

A regression of total energy reserve on live weight (less fleece and conceptus) was established. Differences between this relationship and those established separately for non-pregnant, pregnant and post-partum ewes were not significant.

The contribution of changes in conceptus weight to live-weight changes in gravid ewes is discussed.

Six hundred and sixty-two sheep in twenty-two farm flocks were treated in June/July (period of late anoestrus) with intravaginal sponges impregnated with 30 mg ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxy-progesterone; G. D. Searle) or ‘Cronolone’ plus 400 mg progesterone and incorporating doses of 0-800 μg oestradiol-17β. Treatment was for 12 days; a single dose of 500 i.u. PMS (Burrough's Wellcome) was injected at pessary withdrawal. Seventy rams were joined to breed the ewes at first and second heats.

Oestradiol treatment resulted in a significantly higher incidence of sponge loss, a lower mating response, a lower conception rate and a lower number of lambs/conception. There was also a tendency for onset of oestrus to be delayed. Such effects were confined to first services and were much less evident in sheep receiving doses of 50 μg oestradiol or below. Data indicate that an intravaginal treatment for the induction of early breeding should consist of progestagen alone rather than progestagen in combination with oestradiol. The addition of 400 mg progesterone to the ‘Cronolone’ sponges appeared to reduce the adverse oestrogenic effects. Sheep treated with ‘Cronolone’/progesterone pessaries in the absence of oestradiol showed a mating response of 97%, a conception rate of 64% and 1·7 lambs/conception at the controlled oestrus.

The mating response and lambing outcome in fifty-three sheep was studied after treatment with intravaginal sponges during October (normal breeding season). Bach pessary carried a dose of 30 mg ‘Cronolone’ (9α-fluoro-11β-hydroxy-17α-acetoxyprogesterone; SC-9880, G. D. Searle) in finely dispersed form and was inserted for 14 days. Half the number of pessaries carried an additional dose of 400 mg progesterone. Breeding was by natural service, using 10% rams. Ninety per cent of the fifty ewes bred immediately after treatment conceived; the average number of lambs/conception was 1·9. Sheep treated with ‘Cronolone’/progesterone pessaries showed a marginal and non-significant advantage over those treated with ‘Cronolone’. The application was effective in ensuring the birth of most lambs (87% of total) within a period of 1 week.

Ninety-eight sheep in three farm flocks were treated in July (period of late anoestrus) with intravaginal sponges impregnated with 30 mg ‘Cronolone’ (9α-fluoro-11βhydroxy 17α-acetoxy-progesterone; G. D. Searle) or ‘Cronolone’ plus 400 mg progesterone and incorporating doses of 0–800 μg diethyl stilboestrol. Treatment was for 12 days; a single dose of 500 i.u. PMS (Burroughs Wellcome) was injected at pessary withdrawal. Ten rams bred the ewes at the induced and subsequent heats.

Of the ninety-five ewes retaining pessaries, ninety-three (98%) were bred in the 3 days following treatment. Sixty-three sheep (68·5%) conceived at the controlled oestrus, producing an average of 1·54 lambs/conception. In the thirty-four ewes failing to conceive at that time, twenty-seven (80%) showed oestrus after one cycle interval; twenty of these (74%) conceived and produced 1·3 lambs/conception. Lambing outcome toservices at the controlled oestrus was lowest in sheep treated with 800 μg stilboestrol, but the reduction was not significant.

Oocyte recovery was conducted in 329 slaughtered sheep; from 3072 vesicular follicles ruptured, 1210 oocytes were obtained (av. 3·7 per sheep). After recovery or culture in various media, 801 oocytes were examined for developmental stages. In cattle follicular fluid, little evidence of resumption of meiosis was found. In sheep follicular fluid, meiosis was resumed in many oocytes, but was arrested at the pro-metaphase to metaphase-I stage. A high proportion of oocytes matured to metaphase-II when cultured in growth medium.

In 450 oocytes, recovered from the vesicular follicles of prepuberal lambs and cultured in growth medium for 2–48 h, 76·4% resumed meiosis. The first evidence of polar body extrusion was at 18 h; maturation was completed in most oocytes by 25–27 h.

Four hundred and fifteen oocytes cultured in growth medium for 24·5–28·5 h were transferred to the oviducts of 23 oestrous ewes. Twenty ewes were bred prior to transfer; three remained unbred as a control. After intervals of 24–73 h oocytes were recovered. In 179 oocytes from 19 bred recipients, 19 pronucleateand 26 cleaved eggs were recovered; one apparent 4-cell egg was found in 37 oocytes recovered from unbred ewes.

Transfer was made of 2958 sheep ovarian oocytes, cultured in growth medium for 24–30 h, to the oviducts of 142 oestrous sheep; 132 were bred and ten remained unbred. Forty-two per cent of oocytes were recovered, mainly 4–24 h after transfer; tubal flushings were examined for sperm. Evidence of a sperm within the vitellus of follicular oocytes was found in nine recipients, the earliest at 6 h 50 min after transfer. Pronucleate eggs were most frequent 9–14 h after transfer; a limited number of eggs showing normal cleavage wasrecovered.

Histological sections of skin samples from two Merino flocks were studied to determine if coarse fibres were from primary (P) or secondary (S) follicles.

The mean fibre diameters of P and S fibres were 23.7 and 19.7 µ respectively in flock 1 (significantly different P < 0.5) and 23.1 and 20.5 µ respectively in flock 2 (not significantly different).

The percentages of fibres exceeding 30 µ in flock 1 were 10.1% P and 1.0% S. In flock 2, the percentages of fibres exceeding 30 µ were 10.3% P and 0.6% S fibres. If 30 µ is taken as an arbitrary level of fibre fineness, then the majority of coarse fibres wore from P follicles.

The observed S/P ratios were 22.8/1 at 16 months on flock 1 and 21.7/1 at 15 months in flock 2.

P and K fertilizers were applied over a 5-year period to plots that were either cut, individually grazed or communally grazed. Residual effects were assessed in the sixth year when the sward was ploughed and sown with Italian ryegrass. The residual study supported the earlier published inference that (a) P returned to the sward in sheep dung is not an effective P source under field conditions, (b) communal grazing can lead to appreciable transfer of K from one plot to another.

The effects of defoliation regime on seasonal and total yields of spring- and autumnsown material of three populations Festuca arundinacea(syn. 1 and syn. 2 from North Africa and the British cultivar S. 170) were examined at Cambridge from the period June 1963 to April 1965.

A micro-plot technique was used in which defoliation treatments were defined by vertical height above soil level. The vertical growth intervals between successive defoliations were, for the summer cutting regimes 7.5–25 cm and 2.5–12.5 cm, and for the winter regimes 7.5–20 cm, 2.5–20 cm, 7.5–12.5 cm, and 2.5–7.5 cm.

In summer 1963 mean yields of all populations were very similar, being equivalent to approximately 12000 kg/ha. Mean population yields for the following three 6-month periods were equivalent to (in kg/ha): syn. 11519, 14740, 3385; syn. 2 2194,17669, 5523; S. 170 1656, 19832,3696.

Variety x treatment interactions were found in every season. In particular, S. 170 winter production was reduced by severe defoliations in the preceding summer, and syn. 1 and syn. 2 summer production by severe defoliations in the preceding winter. It is suggested that such interactions may have been responsible for conflicting assessments of the relative potential production of these populations.

Syn. 1 appeared to offer no advantage over S. 170, and syn. 2 only to outyield S. 170 where spring sowing was followed by infrequent or lax defoliations in all seasons. Agronomic implications are discussed.

The performance of a series of intervarietal F1 hybrid populations was determined in simulated swards in a range of environmental conditions. On average the hybrids were more stable in performance than their parental varieties, but they showed no general yield advantage. Several hybrids were markedly heterotic at the higher-parental level, however. More heterosis was exhibited in high productivity conditions than in less favourable environments. A generally poor correlation between parental and F1 hybrid performance under competitive simulated-sward conditions and performance in noncompetitive spaced-plant conditions was found.

The mechanisms responsible for moving K from soil to root were studied by growing perennial ryegrass in pots containing a flinty silt loam from Rothamsted and a sandy Woburn soil, with and without added K, at 0.75 water-holding capacity. More water was taken up from the Rothamsted soil than from the Woburn soil, and less was taken up when K was added without affecting dry-matter production. After 25, 52, 83, 122, 194 and 276 days, K uptake, water uptake and the K concentration in the soil solution were measured and the mass-flow contributionto K uptake calculated.

Without added K, mass-flow accounted for only about one-sixth of the K taken up from the Rothamsted soil and about one-third from the Woburn soil. Except at first, diffusion probably accounted for the remainder of uptake but was the rate-controlling step for uptake from the Woburn soil only. With added K, mass-flow became much more important relative to diffusion in both soils, and transported more than enough K to account for the measured K uptake. Root interception probably did not contribute to K uptake after the early part of the experiment, because the pots used were small.

A number of 237 Barki ewes of 2, 3, 4 and 6 years of age and weighing 25–45 kg were put under close observation so as to study the subjective and objective aspects of their behaviour during parturition.

During the choice and preparation of the parturition site ingestive behaviour ceased and an investigatory behaviour took place using the visual and olfactory senses. Ewes showed preference for the less illuminated and less disturbed places. They pawed the chosen spots with their hooves so as to prepare them for parturition. The parturient behaviour was characterized by signs of uneasiness and of pain, which increased gradually until the lamb's expulsion.

The overall average pre-partum time of labour was 46·1 plusmn; 1·6 min. The 2-year-old ewes took longer to give birth than older ones. The pre-partum labour was not significantly affected by body weights of ewes. The overall average duration of the post-partum labour was 143·27 min. Age and weight of ewes had no significant effect on the duration of the post-partum labour. Births were not evenly distributed over the period of observation.

Micro-organisms from the rumen of a hay-fed sheep rapidly synthesized an intracellular polysaccharide (starch) when growing or resting suspensions of cells were incubated in vitro with easily metabolized sugars.

In 30 min incubation periods the optimum pH for the synthesis of starch by resting cultures was about 6·0 when glucose or fructose were substrates. Relative to glucose (as 100%) in ability to form the polysaccharide were, fructose, 75%; sucrose, 80%; soluble starch, 18·6%; maltose, 6·9%; cellobiose, 4%; and xylose, 2·1%. No starch was formed from galacturonic, acetic, propionic, butyric, lactic or succinic acids. A bacterial fraction of the microbes was reponsible for about 80% of the starch formed from glucose, fructose or sucrose.

In incubations of 24 h, resting cultures formed more starch per unit of microbial protein than growing cultures. The utilization of microbial starch and lactic acid, formation of which often accompanied starch synthesis, gave rise to volatile fatty acids. Acid production was maintained from these substrates at rates similar to those obtained from the fermentation of glucose. The acids were in molar proportions of 65–70% acetic, 20–27% propionic and 8–15% butyric. The maximum starch calculated to be synthesized by the microbes from 100 ml of rumen liquor, in media containing excess sugar, amounted to over 250 mg from glucose, 200 mg from fructose, 200 mg from cellobiose and 50 mg from xylose. It is calculated that under optimum conditions for synthesis about 25 g of starch would pass daily from the rumen of a sheep.

Observations were made on the development of the testes and epididymides of thirty-two Clun Forest ram lambs. There were no significant differences between the weights and volumes of the left and right testes and epididymides.

The rate of increase in testicular and epididymal weights was linear up to a body weight of 46 lb (20·9 kg) followed subsequently by a significantly greater rate of increase at higher body weights. Similar patterns of growth occurred in relation to age, although at a given age there was a wide range of testicular and epididymal weights. There was a close relationship between the development of the testis and the epididymis at body weights greater than 46 lb (20·9 kg).

There were two distinct phases in the dimensional growth of the testis. Increases in testicular length and breadth proceeded at much the same rate at testis weights of below 20 g. During the subsequent phase testicular length increased at a significantly greater rate than testis breadth.