Before the feeding of antibiotics to pigs can be confidently recommended, more evidence is required as to their effect on growth and efficiency of food conversion. The present series of trials were designed with this object in view. The investigations were carried out by statistically designed growth trials as well as by nitrogen-balance determinations in the metabolism crates.

The main point under investigation in the first growth trial was whether the addition of penicillin to a well-balanced diet supplemented with whitefish meal would result in an increased rate of growth and efficiency of food conversion. It was concluded that, although the trend both as regards live-weight gain and efficiency of food conversion was in favour of the penicillin-fed pigs, the differences were too small to reach statistical significance. Nitrogenbalance determinations were also carried out over a period of 63 days on the white-fish meal diet with and without penicillin. The mean daily retention of nitrogen by the two hogs on the control treatment was 11·59 g., and by their two litter-mates on the penicillin treatment 11·42 g.

In the second growth trial penicillin was added to a diet composed of barley meal and fine bran together with a little lucerne meal and minerals and supplemented with extracted-decorticated groundnut meal. In both the group-feeding and in the individual-feeding trial there were ten pigs receiving this basal diet and twenty pigs on the same diet supplemented with 18 mg. of procaine penicillin per lb. of meal fed. This amount of penicillin is more generous than normally used by food manufacturers. There was a striking contrast in the eagerness with which the pigs fed. The penicillin-fed pigs licked their troughs quickly and cleanly in contrast to the other pigs, and it was quite apparent that the antibiotic had a tonic effect in this respect. Although this difference diminished as the trial proceeded, it was still evident when the pigs averaged 100 lb. live weight. It was also quite obvious that the pigs receiving penicillin drank more water than the control pigs. After 10 weeks on experiment the forty pigs receiving penicillin averaged 87·5 lb. in live weight as compared with a mean of 81·7 lb. for the twenty pigs on the control diet. This compares with mean live weights of 186·6 lb. (penicillin) and 177·9 lb. (control) over the whole 20 weeks that the trial lasted. The differences for the group-fed pigs were too small to reach statistical significance, owing to the wider variations within the groups. Highly significant differences, in the period from 36 to 90 lb. live weight, were obtained with the individually fed pigs. The mean live-weight increase per day was 0·95 lb. on the penicillin treatment as compared with 0·88 lb. on the control diet. Correspondingly significant differences characterized the figures for efficiency of food conversion over this period, the mean requirements being 2·97 lb. on the penicillin treatment and 3·21 lb. on the control diet. In the period from 90 to 200 lb. live weight the differences observed were very small and not statistically significant. Over the whole period from 36 to 190 lb. live weight the control pigs required on an average 5·3 more days and consumed approximately 19 lb. more meal per pig, an increase of 3·4%.

The same diet, supplemented with ex. dec. groundnut meal, was used in the second nitrogen-balance trial. The addition of penicillin failed to bring about any significant improvement in the retention of nitrogen or in the utilization of the dietary protein.

The effect of adding penicillin alone and also in conjunction with a vitamin B12 supplement (Distafeed), to the diet supplemented with ex. dec. groundnut meal, was investigated in the third growth trial. The penicillin-fed pigs were better feeders from the start than the control pigs, but in this trial the Distafeed seemed to have an adverse effect on palatability. From a common initial live weight of 40 lb. for each pig up to 90 lb. live weight, the pigs on the control treatment required on an average 3·6 days longer and consumed 10·54 lb. more meal than the pigs receiving procaine penicillin. The liveweight increase per day averaged 0·92 lb. on the control diet in comparison with 0·98 lb. on the penicillin treatment. The figures for efficiency of food conversion were also in favour of the penicillinfed pigs, being 3·05 and 3·25 lb., respectively. To increase 155 lb. in live weight the penicillin-fed pigs required on an average 4 days less with a saving of about 13 lb. of meal per pig, in comparison with the control pigs. The improvement was entirely confined to the period immediately after weaning. No improvement resulted from the simultaneous addition of vitamin B12 with the antibiotic.

The nitrogen retention of pigs was also investigated with and without penicillin and vitamin B12, using diets supplemented with ex. dec. ground-nut meal and extracted soya-bean meal. A summary is given of the results of nitrogen-balance studies with twenty pigs to investigate the effect of antibiotics on protein metabolism.

It was concluded from the above trials that the main effect of procaine penicillin was to stimulate the appetite of the pigs on all-vegetable diets. It seemed therefore that unless the pigs were allowed to benefit fully from their improved appetites, by being allowed full-feed, the maximum effect from the feeding of penicillin would not be attained. In the fourth growth trial this point was tested, using the group-feeding lay-out and adjusting the ration daily so that food was available almost continuously. With the individually fed pigs in this trial the opportunity was taken to test the statement that the magnitude of the response to the feeding of antibiotics is greater with diets supplemented with soya-bean meal than with other vegetable-protein concentrates.

The group-fed pigs under conditions approaching ad lib. feeding were able to consume without wastage distinctly higher amounts of meal than we usually feed in these growth trials, when the meal is restricted according to the feeding chart. The pigs receiving penicillin displayed at first better appetites than the control pigs, and made correspondingly better live-weight gains, but as the trial proceeded the appetite of the control pigs gradually improved and eventually surpassed that of the penicillin-fed pigs. It seemed as if the latter had been overeating in the initial period and were suffering from surfeit. After 11 weeks on experiment the mean live weight of the control pigs was slightly higher than that of the group that received penicillin. It is also interesting to note that with ad lib. feeding, no outstanding difference in water consumption was observed between the treatments, the water consumption being mainly influenced by food consumption.

The results for the individually fed pigs in the fourth growth trial showed that the effect of adding penicillin to a cereal diet supplemented with ex. soya-bean meal was even less pronounced than with ex. dec. ground-nut meal. No significant effect was shown, even in the period immediately after weaning, on the rate of gain or on the efficiency of food conversion as a result of adding 18 mg. of procaine penicillin per lb. of meal. In this trial the pigs were exceptionally good feeders and the soyabean meal diet proved to be highly palatable.

It may be concluded from the results of these trials that with healthy pigs and using normally balanced palatable rations, the improvement in the rate of growth, efficiency of food conversion and rate of nitrogen retention to be expected from the inclusion of penicillin in the diet is generally too small to make it economically worth while.

Experiments were made on twelve rams to determine the effects of hormonal treatment on rams with poor libido. Testosterone and PMS were used and sexual behaviour, and semen characteristics such as volume, motility, impedance-change frequency and dead percentage were studied. The libido was higher in testosterone-treated rams than in the PMS-treated, or in the control rams. Volume of ejaculate was also higher in the former group. There was not much difference in the motility ratings. Impedance change frequency was slightly lower and dead percentage higher in the semen produced by testosterone-treated rams than in other groups.

1. Three groups of mature ewes were fed during pregnancy and lactation on rations differing in their calcium content. The mean daily intakes of calcium were 1·4 g. (group A), 4·5 g. (group B), and 7·4 g. (group C). Blood samples were analysed monthly for calcium and inorganic phosphorus. The ewes were killed at approximately 100 days after parturition and the skeletons isolated. Individual bones, either whole or divided into definite fractions, were analysed.

2. The level of calcium intake was without effect on the number of lambs born, birth weight, or growth while milk fed.

3. Blood calcium was significantly lower in group A than in groups B and C, but blood inorganic phosphorus was unaltered.

4. The resorption of bone substance was greater in group A than in groups B and C.

5. The severity of resorption varied between bones, and in regions within certain bones. Resorption was most severe in the vertebrae and pelvis, and only slight in the metacarpal, the metatarsal and the shafts of other long bones. Resorption of intermediate magnitude was found for the remainder of the skeleton.

6. Resorption was accompanied by reductions in the percentages of ash in bones, but this effect was proportionately less than the ash weight reduction.

7. Radiological observations made on flesh-free bones at the end of the experiment gave a picture of resorption similar to that presented by the data for ash weights and percentages of ash, namely that resorption was much greater in group A than in groups B and C.

1. A 24 factorial experiment involving 68,713 first inseminations was carried out at four artificial insemination centres, to compare semen diluents containing citrate or phosphate buffers and all combinations of sulphanilamide, streptomycin and penicillin.

2. The analysis of the results was carried out on punched card machines and on an automatic calculator (EDSAC), as well as on bench machines.

3. The main results obtained were:

(i) Unsupplemented phosphate buffer gave a conception rate 5·5% above that obtained with unsupplemented citrate buffer.

(ii) Citrate buffer with sulphanilamide, streptomycin and penicillin gave a conception rate 6·8% above that obtained with unsupplemented citrate buffer; and

(iii) Phosphate buffer with penicillin gave a conception rate 9·3% above that obtained with unsupplemented citrate buffer. This effect was not, however, significantly greater than that referred to in (ii).

4. Phosphate buffer depressed conception rate when used with sulphanilamide or streptomycin.

1. Certain carcass measurements (length, shoulder and mid-back fats, belly thickness and dressing percentage) made on a total of 402 bacon pigs from four antibiotic feeding trials have been analysed.

2. The length of the carcasses showed more variation between pens treated with various doses of penicillin than between control pens or pens treated with aureomycin. This greater variation in length was related to the greater variation in growth rate between the penicillin treatments. No differences in the mean lengths of control, penicillin and aureomycin treatments were found.

3. Back fat measurements and belly thickness showed no differences between aureomycin, penicillin and control treatments in overall tests.

4. Aureomycin consistently gave higher dressing percentages than penicillin. Animal protein also gave higher dressing percentages than vegetable protein, but no effect of vitamin B12 on this quantity was found.

An experiment, carried out to determine the effect of dressings of sulphate of ammonia on an established lucerne-cocksfoot ley grown in narrow rows on heavy gault clay soil, is described and the results discussed. The experiment was carried out over 3 full years (1948–50) and the first crop of the following year. The results suggest that it is possible to increase the yields of grass and total produce without decreasing the yield of lucerne but that no marked increase in the yield of nitrogen per acre is to be expected. Of the times of application tested February proved the most effective.

1. Some earlier work concerning the management of lucerne is discussed.

2. Two experiments, designed to compare cutting and grazing the second (July) crop, and cutting and grazing the third crop at two different dates (September and October) each year on the yield and botanical composition of a lucerne-grass (mainly cocksfoot) ley, are described and the results discussed.

3. The method of defoliating both the second and the third crops had very little lasting effect on yield or composition of the ley, though some temporary effects, depending on season, were found.

4. It is shown that date of defoliating the third (autumn) crop of a lucerne-grass mixture may influence the yield of oven-dried produce from an individual crop. Late autumn defoliation led to a greater yield of lucerne and a greater proportion of lucerne in the produce, but since the opposite effect was found in the yield of grass there was no overall effect on the total yield of oven-dried produce over a 3-year period.

5. In these experiments it appeared that lack of winter cover had no adverse effect on the productivity or persistence of lucerne in the lucerne-grass mixture studied.

1. The rates of growth and efficiencies of food conversion between 45 and 100 lb. live weight of pigs kept to a low plane of feeding were most adversely affected during the winter months by bad housing conditions, wherein the average air temperature was 43° F. On the other hand, this bad housing had no adverse effect upon pigs of a similar size kept to a high plane of feeding.

2. The summer season, with consequently higher environmental temperatures in both good and bad piggeries, only had a significantly beneficial effect upon the rates and efficiencies of growth of pigs of 45–100 lb. live weight kept to a low plane of feeding in a bad piggery. Any effects upon the growth of pigs of similar size kept to a high plane of feeding in either a good or bad piggery or to a low plane of feeding in a good piggery did not approach statistical significance.

3. There was probably some environmental factor other than air temperature or relative humidity which had a beneficial effect on the growth of the pigs kept to a low plane of feeding in the good piggery.

4. It was observed, but not proved, that pigs of 100–200 lb. live weight kept to a high plane of feeding grew rather more efficiently in the bad house than in the good house, despite the higher environmental temperatures in the good house.

5. During the growth period between 45 and 100 lb. live weight the efficiency of food conversion, expressed in pounds t.d.n. required per pound liveweight increase, was better in the well-housed pigs kept to the low plane of feeding than in the highplane pigs housed in either piggery.

6. During the growth period between 100 and 200 lb. live weight the efficiency of food conversion of the well-housed low-plane pigs was significantly better than that for the well-housed high-plane pigs, but was not significantly better than the efficiency of food conversion of the high-plane pigs from the bad piggery.

An inquiry has been made to determine whether shearling rams sire more good-quality offspring than would be expected from the proportion of them used in Swaledale flocks in northern England, 1951–3.

Quality was assessed at two levels, both concerning shearling rams: those passed for registration in the Flock Book, and those making £50 or more at Kirkby Stephen ram sale.

The expected percentage of lambs, and hence good-quality offspring, by shearling rams was estimated from the practice on a sample group of farms, using the formula

where E is the estimated percentage of lambs by shearlings, x the proportion of shearlings to all rams in use, and y the fractional value in numbers of ewes served where aged rams are regarded as having unit value.

The estimated percentage of lambs by shearlings is 28·7, with s.e. = 2·444.

The actual percentage of registered shearlings sired by shearlings in 1951–3 was 35·7 with s.e. = 0·764, and the actual percentage of shearlings sold for £50 or more in the same years was 32·8 with s.e. = 3·313.

That shearlings sire a slightly, but significantly, higher number of registered shearlings than would be expected is probably due to the transmission of earlymaturing qualities, since shearlings of high quality are consistently used in early-maturing, and therefore shearling-producing, flocks. Those likely to sire ‘£50’ shearlings often remain in early-maturing flocks throughout life and, by continuing to sire this high-quality progeny, depress the percentage of such shearlings sired by shearlings to a figure not significantly higher than the ‘expected’ figure.

1. Methods, buildings and equipment used for milk production in Caernarvonshire, Hertfordshire, Pembrokeshire and Wiltshire have been ascertained by a random sample survey carried out in 1948–9.

2. The results showed marked differences between counties in practically every respect which are summarized in thirty-two tables.

3. The value of this survey and some points in its planning and execution are critically discussed.

1. The seed of crosses of Secale cereale with S. montanum and S. dalmaticum germinated only when S. cereale was the seed parent.

2. S. cereale was found to differ from S. montanum and S. dalmaticum by two large translocations involving three pairs of chromosomes, and a small translocation involving a fourth pair. The fertility of the F1 plants was low, and in ear morphology and perennial habit they were similar to the S. montanum and S. dalmaticum parents.

3. S. montanum and S. dalmaticum were found to be similar in gross chromosome structure and their hybrids were phenotypically intermediate and fertile.

4. The F2 of the cross S. cereale x S. dalmaticum consisted of three types, in terms of chromosome structural condition and plant morphology, those like one or other parent and those like the F1.

5. The genetic and evolutionary significance of this situation is discussed, together with the problem of the fixation of translocations in populations.

Nitrogen, at the rate of 0.5 cwt./acre, was applied to winter wheat as an April dressing of nitrochalk, or as eight sprayings of 2% NH4NO3 solution applied either to the soil or to the leaves at about the period of maximum leaf area, before and during ear emergence. All three methods of nitrogen application caused similar increases in yield and nitrogen content of grain. April nitrogen gave a greater yield of straw than the later dressings.

Late nitrogen application caused a small increase in leaf area index, first noticeable one week after ear emergence and persisting for another four weeks. L.A.I. of plots that received nitrogen in April was much larger than that of the other plots at the period of maximum leaf area, but by four weeks after ear emergence it was less than that of plots receiving the late nitrogen. Shoot number per metre and leaf area per shoot were increased by early nitrogen, but only the latter was increased by nitrogen applied at ear emergence.

Leaf area duration after ear emergence was the same on all nitrogen-treated plots and the yield of grain divided by L.A.D. was nearly constant for all plots.

Applying nitrogen late, after an April dressing, did not prevent the rapid fall in L.A.I. from the high value reached at the period of maximum leaf area and caused no greater increase in yield than when applied in the absence of an April top-dressing. A single urea spray applied in early June increased yield to the same extent as the ammonium nitrate sprays.

1. Pollen mother cells with irregularities of meiosis were rare in the parent species and varieties, being usually less than 0·5% and the highest found being only 1·57% in the variety Grey Winter.

2. F1A. fatua C.S. 473 (from Afghanistan) × Grey Winter had 33·5% of pollen mother cells with irregularities. On the other hand, the F1 hybrids of A. fatua (C.S. 46 (from Asia Minor) × both spring and winter varieties of A. sativa showed between 2·45 and 12·81% of irregular cells and were thus more regular than F1 spring variety of A. sativa × Grey Winter.

3. F1A. sterilis × spring and winter varieties of A. sativa showed between 5·56 and 6·67% of cells with irregularities of meiosis.

4. F1A. fatua C.S.46 × A. sterilis and F1A. nuda × A. sterilis had 5·65 and 7·60% of irregular cells respectively, but F1A. nuda × A.fatua C.S. 46 had 46·05%.

5. All F1 hybrids with A. byzantina as one parent had high frequencies of pollen mother cells (from 59·12 to 88·45%).

6. The commonest irregularity of meiosis was the occurrence of univalents. Multivalents were found at a high frequency only in the A. byzantina hybrids. Bridges and fragments were uncommon, occurring in not more than 2% of cells.

7. The limitations of the cytological results in assessing the relationships between the different hexaploid species of oats are discussed. It would, however, appear that there is a close relationship between A. sativa (both spring and winter varieties), A.fatua (C.S. 46) and A. sterilis, but that A. byzantina is not closely related to that group.

8. The importance of the results to the plant breeder is briefly indicated.

1. A condition that appears to be identical with ‘green yolks’ as observed in natural cases has been reproduced by the oral administration in gelatin capsule of from 250 to 1000 mg. sodium copper chlorophyllin 100% daily for 4 days upwards to Light Sussex hens in second lay.

2. Following suitable extraction procedures the presence of a chlorophyll derivative has been determined spectrophotometrically in the affected yolks.

3. Quantities of sodium copper chlorophyllin of the order of 1 mg. have been recovered from affected yolks.

4. It is considered that the passage of chlorophyll to the yolk indicates that intestinal absorption has occurred.

Data concerning a random sample of about 4% of the flocks in Yorkshire were collected in the form of answers to a questionnaire. The information required was given by 98% of the farmers in the sample.

The survey has shown the extent of losses associated with pregnancy and parturition in 1952–3 and the areas in which they were most severe; it has also given some indication of the factors that might be affecting losses of different kinds.

In addition to this information, the survey has provided statistics concerning feeding and husbandry and the relative importance of different breed types in Yorkshire.

1. A review of the literature relating to the frequency at which pigs suckle under natural conditions was made. The evidence indicated that the average interval between successive sucklings is approximately 1–1¼ hr.

2. A number of sows and their litters were continuously observed for varying periods of time under natural conditions and a similar average interval between sucklings was observed.

3. A review of the literature relating to the determination of milk production of sows was made. This showed that the majority of previous workers imposed, during the periods when the litters were being weighed before and after every suckling, a suckling frequency that did not simulate the natural behaviour of the animals. Evidence suggesting that the imposition of such unnatural conditions invalidated the findings, in so far as they might indicate the true milking capacity of the animals, was discussed.

4. An experiment to obtain direct evidence on the importance of the suckling interval in relation to the milk obtained by the pigs was carried out. Conclusive evidence was obtained that when suckling was allowed every hour, both the quantity of milk obtained by the litters and their live-weight gain in 24 hr. periods were much greater than was the case when suckling was allowed only every 2½ or 3 hr. In addition, the pigs on the hourly suckling frequency utilized their milk intake more efficiently.

5. An experiment was carried out in which an attempt was made to obtain, under natural conditions, a valid estimate of the 56 days' lactation yield of three Large White gilts. The method of weighing the individual pigs before and after suckling was used, and the animals were allowed to suckle every hour.

6. The estimated average lactation yield was 768 lb., with a range of from 882 to 655 lb., although it was suggested that the true yield might be some 5–10% higher. The figures obtained in this work were shown to be very much higher than the yields reported by most of the previous workers.

7. The nursing and suckling behaviour of the dams and their litters was studied. Observations of significance in relation to the variation in growth of pigs within a litter were made.

8. Data were obtained concerning the average amount of milk obtained by individual pigs at a suckling, the total amount ejected at a suckling, the effect of daylight and of darkness on the amount of milk obtained, the relative productivity of the individual mammary glands and the efficiency with which the milk intake was utilized by the individual pigs in the litter.

9. A close positive relation between milk intake and live-weight gain during the first 3 weeks of life was found. During the last 5 weeks of lactation, when supplementary food was available, this close relationship was not seen.

10. The growth rate of the suckling pig, as related to the supply of food, was discussed. The evidence available suggested that the supply of sow's milk was frequently insufficient to meet the requirements of the pigs for optimum growth.

11. The chemical composition of sow's milk in relation to the stage of lactation was studied.

A brief account is given of the accepted view that riboflavin supplements in the diet of breeding stock lead to improved hatchability and that clubbed down is specific for a deficiency of this vitamin. Attention, however, is drawn to the apparent failure of various workers to achieve a hatching rate with a riboflavin supplemented diet substantially in excess of 80% of fertile eggs which appears to be the national average figure. An experiment is described in which range managed breeding stock received diets supplemented with riboflavin at varying levels, the lowest of which, in the light of available evidence, would be sufficient for good hatchability having regard to the riboflavin obtained by the stock from grass and their own droppings. The hatching rate of fertile eggs was maintained at about 80% with all rations and little change took place consequent on changing over from high to low or vice versa. Only a very small improvement was observed with a very high level of riboflavin. It is therefore concluded that either a figure around 80% hatchability represents the maximum influence of riboflavin on hatching rates or that there are generally other factor(s) present (or absent) in the embryo that prevent a higher rate being achieved. The evidence submitted suggests that this factor may be B12 or more probably, one of the unidentified factors in the A.P.F. complex, and that for hatching rates materially above 80% the A.P.F. complex must be increased above the levels presently supplied to range managed breeding stock, or the high hatching rates induced by high levels of riboflavin may greatly increase the birds' requirements for this factor(s) to a level well above that normally necessary.

Attention is also drawn to the incidence of clubbed down among dead-in-shell with varying levels of dietary riboflavin. It is concluded that the presence of this embryonic abnormality is rapidly and almost completely influenced by changes in the level of dietary riboflavin and that these changes take place much more rapidly than changes in hatchability, once a moderately high hatching rate has already been reached. It is also contended that high riboflavin levels will almost eliminate the incidence of clubbed down, although an already moderately high hatching rate will remain unaffected. For this reason it is argued that the presence of clubbed down in some dead-in-shell is no conclusive evidence that an improvement in hatchability will follow supplementation of the diet with riboflavin unless the hatching rate is below average.