1. In the course of a 2-year field trial (1959–60) conducted in mid-Wales, 525 cattle were entered by 317 co-operating farmers for treatment with p.m.s. in the induction of multiple-pregnancy. Most animals were commercial, non-pedigree cattle maintained in accord with local custom. The cattle were of mixed ages and included some milking cows as well as animals used in calf rearing.

2. The method of hormone treatment tested consists of a single subcutaneous injection of a freeze-dried preparation of p.m.s. administered in the follicular phase of the oestrous cycle. Most cows were injected 16 or 17 days after a previous oestrus and bred by a.i. at the heat period following injection.

3. Of the 525 cattle injected 416 provide comprehensive data on factors affecting ovulatory response; seventy cattle, which had a ‘silent heat’ after injection, provide additional but partial information. In thirty-nine cattle, it was not possible to obtain reliable evidence of response. Data on ovulation and pregnancy were obtained by examinations per rectum conducted during the early weeks of pregnancy.

4. Ovulation data relate to 416 cows which were injected, came in oestrus shortly afterwards and inseminated, then examined for evidence of fresh corporea lutea at the following mid-cycle stage. Five dosage levels of p.m.s. were employed (800, 1000, 1200, 1600 and 2000 i.u.). The normal process of ovulation did not appear adversely affected by any of the doses employed. 173 of the 416 cows (41·6%) produced more than one egg.

5. There is clear evidence of a dose-response relationship over the dosage range employed. The mean number of ovulations varies from 1·43 at 800 i.u. to 3·97 at 2000 i.u. The percentage of cattle shedding additional eggs rises from 33 at 800 i.u. to 56–6 at 2,000 i.u., but increasing dosage level leads to considerable variability in ovulatory response: range of ovulations at 800 i.u. is 1–5, and at 2000 i.u. is 1–25.

6. Little affect was observed in ovulatory response according to the stage of p.m.s. administration. At low dosage levels, an interval of at least 2 days between injection and oestrus was necessary to allow response to occur. Among factors affecting response to a standard dose of p.m.s., lactation and state of normal ovarian activity appeared to have some importance. There was no evidence of an effect on cycle length. Treatment did not give rise to abnormal mating behaviour and the incidence of adverse side-effects following p.m.s. injection was negligible. The occurrence of large unovulated follicles occurred more frequently following treatment with 2000 i.u. than with lesser dosage levels. 59·1% of all ovulations occurred in the right ovary and 40·9% in the left. In examinations made prior to injection, the incidence of spontaneous double ovulations was 4·1%.

7. With the p.m.s. approach, it is found that one problem in cattle is that of silent heat, the condition where ovulation is not accompanied by the usual symptoms of oestrus. In 486 animals for which information was obtained, silent heat occurred in 70 (14·4%). There is some tendency for the condition to occur more frequently where low dosage levels are used or where p.m.s. is administered very late in the oestrous cycle. Lactation appears to affect the incidence of the defect. The lowest incidence (4·8%) occurs in ‘dry’ cows and the highest (22·7%) in cattle rearing three to four calves. Superovulation occurred less frequently at silent heat than at normal oestrus. There is no evidence that p.m.s. injection is the direct cause of the condition. It appears that time of ovulation in animals showing silent heat is comparable with that for cattle showing the normal symptoms.

8. Of the 416 cattle put to a.i. shortly after p.m.s. administration, 317 (76·2%) were pregnant when examined some 6 weeks after first insemination. This compares closely with the normal 30–60 day non-return figure for the mid-Wales area (78·5%). Cattle conceived as readily after injection with 2000 i.u. as after treatment with 800 i.u. Even where animals shed many eggs (e.g. more than six) the conception percentage (84·0) was high. It is clear that this form of therapy does not adversely affect the processes of ovulation, fertilization and implantation. There is some suggestion that p.m.s. aided conception in repeat-breeder cattle. Examinations in the mid-cycle stage following a.i. did not adversely affect conception.

9. Data on the number of eggs surviving (as foetuses) in the 6th week after mating, in relation to the initial number of ovulations, clearly show a heavy loss in eggs in early pregnancy. 41·6% of cattle shed additional eggs but only 23·1% possessed multiples in early pregnancy.

10. Reduction to a single foetus seemed particularly liable to occur in cattle producing two eggs-only. Of sixty-seven double-ovulating animals that conceived, thirty-two possessed twins at the 6th week (47·7%). The survival of both eggs in such cows was better when one egg was shed by each ovary (61·5%) than where both ovulations occurred in the one ovary (28·6%). Analysis of data on egg survival according to factors such as age, breed, time of treatment did not reveal differences.

11. Trans-uterine migration of eggs was rarely (1 case in 197 examinations) noted. The ability of a single uterine horn to sustain more than two foetuses was limited. In cattle where three to six eggs were shed by an ovary, the survival of twins in the associated uterine horn was observed in a majority (57%) of cases. Where many eggs (ten to fifteen) were shed by an ovary, twins were rarely sustained by the associated uterine horn.

12. A steady increase in the percentage of cows carrying multiples (at 6 weeks) was noted over the dosage range employed. 20·8% of cows injected with 800 i.u. carried multiples, the figures for doses of 1000, 1200 1600, and 2000 i.u. being 25·2, 31·3, 41·7 and 42·7, respectively. Multiples in the form of triplets and quadruplets occurred more frequently at the higher dosage levels than at 800–1000 i.u. of all cows with multiples considered, 36·5% possessed more than two foetuses at examination in the 6th week.

13. Pregnancy diagnosis examinations were conducted over a period ranging from 35 to 101 days after mating, with most falling in the period 41–44 days. It appeared that the most appropriate time for diagnosing multiples was at the end of the 6th week of pregnancy. The need to conduct diagnosis at a specific time after mating, and the fact that the examination may lead to total litter loss in many animals, makes the procedure unsuitable for any widespread practice. Partial litter loss (loss of one foetus) was observed in 12·5% of cows carrying twins at 6 weeks and in 20·0% of those with triplets.

14. In nineteen cows, each possessing either three or four foetuses, an attempt was made in the 6th week of pregnancy to control litter size to two. This was by rupture of excess amniotic vesicles by manipulation per rectum. Two of those so treated eventually produced calves, the others either aborting or returning in oestrus soon after the control procedure. The method is unsuitable for farm application for reason of the delay in returning to normal breeding after such cases of failure of pregnancy.

15. A substantial proportion (32·5%) of those cows which were subjected to pregnancy diagnosis lost the conceptus a short time afterwards. Foetal loss in cows with twins was greater (43–46%) where foetuses were both in the one horn than where distributed between both horns (31%). The various factors which were possibly involved in foetal loss are discussed. Evidence was obtained that total foetal loss occurred more frequently in animals shedding many eggs than in those shedding few.

16. Information is recorded for 147 injected cattle which produced single calves following conception at the oestrus immediately following hormone treatment. Additional data on single calvings are provided by 200 untreated cattle which were studied in the area of the trial. These data show birth weight of single calves to be 78·6 lb., and the incidence of calf mortality, retention of foetal membranes and difficult calvings to be 4·9, and 6·0%, respectively. The mean duration of the gestation period was 283·4 days.

17. The outcome of multiple calving was observed in forty-four cattle (thirty-five sets of twins, eight sets of triplets and one set of quintuplets). As a result of earlier examinations, farmers were usually alert to the fact that cows were carrying twins. Herd owners were encouraged to provide such cows with an additional 2 cwt. of a suitable concentrate feed during the final 2 months of pregnancy. Although a number of herd owners followed the recommended feeding programme, in a number of instances the most appropriate pre-calving preparation was not given. The outcome of calvings in relation to the level of additional feeding is considered under three headings, high, moderate and low plane.

18. Given good feeding (high plane) the outcome of twin calvings was satisfactory. Results suggest that the problems often associated with twins (low-weight calves, high rate of mortality, retained foetal membranes, loss of conditon and poor subsequent breeding of the dam) may largely be overcome by an adequate ‘steaming-up’ policy. In cows adequately prepared, birth weight ranging from 59 to 89 lb. were recorded (mean 73·9 lb.) Mean gestation was a little less (280·6 days) than for singles. The incidence of retained foetal membranes (18·2%) was greater than that for single-bearing cows, but did not constitute a serious problem in any animal.

19. Less satisfactory results were noted in cows not given adequate preparation for twins. Where triplets were carried, the outcome for cow and calves, regardless of the feeding attention given, was unsatisfactory. Triplet-bearing cows calved earlier, and the incidence of retained foetal membranes, difficult calvings and calf deaths was much above that noted for the twin-bearing animals. The single set of quintuplets was born prematurely, all calves being dead.

20. Problems in the field application of the p.m.s. technique are considered in the light of the results obtained in the trial and from discussion with farmers in the area of work.

21. Information was obtained on the incidence of natural twins in 3826 calvings in the mid-Wales area. The figure of 2·82% compares closely with that noted in other surveys in the United Kingdom. Literature on the incidence is reviewed.

22. It is clear, from the results obtained in this trial, that the technical problems facing commercial usage of p.m.s. are too numerous to allow any practical recommendation to be made. While none seems to be of such a nature as to make the eventual development of a twinning technique unlikely, there is little hope of immediate solution to many of them. The lines of work which may lead to more satisfactory results are discussed in the final section of the paper.

1. Data on the crude-protein content and crudeprotein production of five grass species (each sown with white clover) over the period 1954–56, at six levels of compound fertilizer application, are reported. Perennial rye-grass (S. 101), meadow fescue (S. 215), timothy (S. 48), cocksfoot (S. 26) and bent (N.Z. Browntop) were sown in 1953 at appropriate seed rates, each with 2 lb./acre S. 100 white clover. The fertilizer treatments were 0, 1, 3, 5, 7 and 9 cwt./ acre of a compound of composition 10% N, 4%P2O5, 9·5% K2O applied in the early spring of each of the years 1954–56. The swards were cut three times a year in 1954 and 1956, but only two cuts were possible in 1955.

2. Bent mixtures had a higher crude-protein content than any other mixture in all years and (with one exception) at every cut within years. Differences between other mixtures were smaller and often erratic, though timothy invariably had the lowest crude-protein content at the second cut and cocksfoot at the third. Application of the fertilizer raised the crude-protein level of the herbage at the first cut, but depressed it in subsequent cuts.

3. The bent mixture gave the highest yield of crude-protein per acre followed by the timothy mixture, while the lowest yield was produced by the perennial rye-grass mixture. The bent mixture differed from all others in its distribution of crudeprotein production over the season, producing less at the first cuts and more at the second and third cuts. This reflects its pattern of production of dry-matter. Response to spring application of fertilizer in terms of crude-protein yield declined rapidly from cut to cut. Over the whole period of the experiment 1 cwt./acre/ annum of fertilizer containing 10% N gave a response of about 0·5 cwt. crude-protein/annum.

The nitrate-nitrogen contents of herbage at the first cut of 1956, and at a first cut in 1957

Herbage samples from two replicates of the first cut of 1956, and from two replicates of a first cut taken in 1957 in the present experiment, were analysed for nitrate-N. The 1957 results are included here as illustrating the influence of season on nitrate-N accumulation, although data from that year have not been reported in the two papers of the present series. Attention has been limited to first cuts, as nitrate-N accumulation is normally greater the shorter the interval between, the application of nitrogen fertilizer and sampling, and in addition the spring flush of growth is usually conducive to high nitrate-N contents (ap Griffith, 1961).

1. The object of the experiment was to make a detailed investigation of the carcass composition of Large White hogs at 68, 91 and 118 kg. live weight (i.e. 50, 68 and 92 kg. carcass weight). Ten hogs were dissected at each stage.

2. A dissection technique suitable for this investigation is described, involving the dissection of one side into individual bones and muscles, subcutaneous and intermuscular fat deposits, skin, tendon, glands and blood vessels. Some possible modifications of the method for future investigations are also discussed.

3. The complete dissection of one side took approximately 110 man-hours and the average weight loss in dissection was 0·798%.

1. Results are presented concerning the gross composition of pig carcasses at 50, 68 and 92 kg. carcass weight in ten litters. They show that during the periods under consideration the proportion of muscle in the carcass exceeded that of the other tissues. However, while the rates of growth of muscle and bone were similar the growth rate of fat was markedly greater. The result was that at 92 kg. the proportions of muscle and fat in the carcass were 43·53 and 41·37%, respectively.

2. Results are also presented dealing with the relative development of the different parts of the skeleton. Of the five major anatomical regions of the skeleton the sacrum grew relatively fastest between 50 and 68 kg. carcass weight while the cervical vertebrae grew fastest in the second period. In both periods the bones of the thorax and loin grew at rates intermediate between the fastest and slowest growing regions.

1. The ‘availability’ of the magnesium of diets consisting solely of roughage or succulent feeds, including herbages cut at different seasons and at different stages of growth, and of diets of hay supplemented with various concentrate feeds, was assessed in metabolism trials conducted with two non-pregnant, non-lactating Shorthorn cows.

2. The highest daily intakes of magnesium (1720 g./day) were provided by a diet of red clover: grasses and hays generally gave a considerably lower intake of magnesium (8–10 g./day), and most of the other diets provided intermediate amounts. However, with timothy hay and barley straw, intakes of 5 and 2 g./day, respectively, were recorded. Supplements to a diet of hay of dairy cubes or of oilcakes rich in protein gave a massive increase in magnesium intake but a supplement of flaked maize provided little additional magnesium.

3. The ‘availability’ of the magnesium of the diets was generally low, within the range of 5–30%. With diets of single feeds no clear distinction between the various roughages and succulents in the ‘availability’ of their magnesium was established, though within the group of herbages the lowest values tended to occur with grasses cut at an early stage of growth and the highest values at the mature stage. A supplement of flaked maize increased the ‘availability’ of dietary magnesium and one of protein-rich oil cakes decreased the ‘availability’ of dietary magnesium.

4. The results are discussed in relation to the development of hypomagnesaemia in cattle grazing spring pasture.

The practice of supplementary feeding of concentrates has been the subject of much investigation and also the centre of considerable controversy during the last decade. The latter is perhaps not hard to explain as so many variables are present; first and foremost there is the cow which at all times must be considered an individual whether it be milk yield, time of calving or dry-matter intake. In addition, one must always take into account the quantity and quality of grass, both of which are dependent on sward management and the system of grazing.

Lactating Boran type zebu cows had high haemoglobin levels during the week after calving, after which these levels dropped sharply and then continued to decline more gradually until their calves were weaned. Some recovery was made during the subsequent dry period.

Cows fed 1 oz. dicalcium phosphate daily were constantly lower in blood haemoglobin level than their controls, and significantly so between the 14th and 20th weeks of the lactation. No differences were observed in weekly weight changes or in estimated milk yields.

Calf haemoglobins decreased gradually with age until relatively adult levels were reached at about a year of age. Initial content during the week of birth was lower than at a few weeks old. There was no difference in the blood haemoglobins of calves suckling on treated and untreated cows.

Individual variation was high in all groups. Some implications of seasonal effects and altitude are discussed.

1. Variations in the crude-protein and mineral content of pastures at Muguga are described.

2. At all times sodium appeared to be inadequate, and during dry periods phosphorus and crude protein were also apparently deficient.

3. Except for sodium and calcium, the amounts present of all substances determined largely depended upon the amount of recent rain.

4. The difficulties of interpreting such data have been considered.

1. Δmin-Nad is the most satisfactory measurement for assessing mineralizable-N in the tropical forest soils used; values are treble those for Δmin-Nf and then increase even further on storage. Comparisons of Δmin-Nad are pointless unless methods of sampling, drying, storing and incubating are standardized.

2. Δmin-Nad is correlated with total N and organic C but not pH.

3. Undisturbed tropical forest soils can produce very large quantities of mineral N, particularly in their surface layers. This probably accounts for the lack of N responses in these soils. More intensive cultivation of these soils is only possible when organic matter is preserved by protecting cleared soils.

4. Added nitrogen was leached more rapidly in these soils than in comparable temperate soils but was not fast enough to prevent absorption by plants.

1. Italian ryegrass was used in 1958 and in 1959 to compare ‘single’ spring dressings of urea-formaldehyde fertilizer (UF) with equivalent spring dressings of ‘Nitro-Chalk’ (NC), and with ‘repeated’ NC (divided equally between three cuttings). Barley measured residues in 1960.

2. At the first cut each year, yields from UF and repeated NC were similar, but later NC gave much larger yields. Aggregate increases from UF were less than half those from equivalent NC.

3. Both forma of nitrogen had residual value for grass and barley.

4. Maximum recovery of N, over 3 years, was 54% for UF and 90% for equivalent NC. Single NC dressings were recovered more completely than repeated dressings.

5. The maximum aggregate uptakes over 2 years by grass receiving 2·0 cwt. N/acre each year were 72 lb. P and 611 lb. K/acre.

Eleven years of field experiments on manuring sugar beet were used by the late E. M. Crowther to compare methods of analysing soils for soluble P and K; this paper reports his work.

The experiments were divided by soil analyses into groups of equal numbers of sites; average crop responses were used to value the analytical methods. Such tables of average data overvalue soil analyses because each method was misleading in a small proportion of the fields used. A quantitative way was developed of assessing the gains from using soil analysis in planning fertilizing and of comparing analytical methods. The total profit from uniformly manuring all the soils examined was compared with the profit made by using analyses to select a proportion only of the soils to be manured; the total amount of fertilizer used was the same with each way of planning manuring. The most efficient analytical method gave the most profit.

For phosphate, differential manuring of sites selected by soil analysis was more profitable than uniform manuring, with all the methods of measuring soluble P that were tested. The best method used a rapid extraction with dilute hydrochloric acid, but extracting with water (calcium bicarbonate solution was used for calcareous soils), or with citric acid solution, was nearly as effective. These three methods, using little solvent relative to soil, were more useful than methods using larger volumes of dilute sulphuric acid, dilute acetic acid, and a lactate solution.

The sugar beet responded more often to K than to P manuring, so there was less chance of making extra profit by using analyses to detect the richer soils where either no K fertilizer, or small dressings only, should have been given. Using the citric acid method of measuring soluble-K to separate the soils into groups for differental manuring was more profitable than giving uniform dessings to all fields; acetic acid was less effective than citric acid, and the hydrochloric acid method gave no advantage over uniform manuring with the heavier rate of potassium. Water-soluble K measurements were worse than acid-soluble values; using them to predict responses and manuring would have given less profit than uniform manuring at the heavier rate used.

Soil samples from 179 field experiments testing phosphate fertilizers on potatoes, swedes and grass were analysed for total phosphorus, and for phosphorus soluble in the following solutions: 0·3 N-HCl, 0·002 N-H2SO4, 1% citric acid (H3Ci), 0·5 N acetic acid (HAc), acetic acid-sodium acetate buffer (HAc-NaAc) at pH 4·8, 0·5 M-NaHCO3, and 0·01 M CaCl2.

Average values for soluble P were closely related to average crop responses to superphosphate in the experiments on swedes, but not in the grass and potato experiments. The extractants that differentiated best between responsive and unresponsive groups of experiments were HAc, HAc-NaAc, and NaHCO3 for potatoes, and HCl, H2S04, HAc–NaAc, NaHCO3 and CaCl2 for grass.

For the experiments as a whole 0·5 M-NaHCO3 was the ‘best’ extractant. The HCl, H2SO4, and HAc-NaAc buffer solution methods were roughly equally effective, though inferior to NaHCO3; the other three extractants (HAc, H3Ci, CaCl2) were of little general use. Total P in soil was also related to response to superphosphate, though less well than values for soluble P obtained by the better methods.

Estimates of soluble P by different solvents were often related. Estimates by HCl and H2SO4 methods were most closely related; values for P soluble in H2SO4 and in HAc-NaAc were also often significantly correlated, as were estimates by HAc–NaAc and CaCl2. The H3Ci and CaCl2 methods gave results that were least related to those with other methods.

The use of soil analyses in advising on P-manuring is discussed and a tentative method is proposed of establishing the analytical limits for soluble P that define ‘deficient’ soils. If the confidence attached to the limiting values that separate ‘deficient’ and ‘non-deficient’ soils is stated, farmers will be able to assess the risk entailed in accepting advice based on soil analysis.