1. The leaf tensile strength of individual plants of a population of Lolium (multiflorum x perenne) perenne was measured on four occasions, October and December 1963 (160 plants) and January and March 1964 (73 of the 160 plants). All plants had been chosen for the good uniform vegetative growth they had exhibited over several seasons. The cellulose content of the 14 weakest and 14 strongest plants in October and of all 73 plants in March was determined.

2. There was a wide range in leaf strength, maintained from October to March, within the population. In October all 14 weakest plants had lower cellulose content than the 14 strongest and from these two groups six plants of low leaf strength and low cellulose content and six of high leaf strength and high cellulose content were selected as parent plants for divergent selections. In March there was a positive highly significant (P < 0.001) phenotypic correlation between leaf strength and cellulose content (r = +0.58).

3. Two diallel crosses were performed, one within the six parents of low leaf strength and low cellulose content and the other within the six high parents. Leaf strength and cellulose data was obtained from progeny and from parental ramets in October 1964 and high overall heritabilities for both characters (approx. 0.8) calculated from achieved advances and parent/progeny regressions. Selection for high leaf strength and high cellulose content was more effective than for low.

1. Lucerne was grown in a glasshouse under different moisture regimes in order to determine the effect of soil moisture content at the time of defoliating on subsequent yield.

2. Drought conditions were found to reduce yield in the short-term, particularly in conditions in which demand for water was high, but the crop subsequently recovered when supplied with ample moisture. Defoliation during a drought period showed no long-term effect on yield.

This work was carried out as part of the programme of crop-husbandry experimentation at the University of Cambridge School of Agriculture, and the author welcomes this opportunity of thanking Mr F. Hanley, Reader in Crop Husbandry, for advice and suggestions.

A comparison has been made over 2 years of spring shedding in cattle maintained in two environments experiencing a similar photoperiod but vastly different seasonal temperatures. At each location (Walcha and Narrabi, N.S.W.) experimental animals were divided into two nutritional groups, namely a Feed group and a Pasture group.

2. In 1961-62 both the Feed and Pasture groups in the warmer climate of Narrabri shed their winter coats in October, while animals maintained under the cooler conditions of Walcha did not acquire their summer coats until January of the following year. The Narrabri groups, however, also displayed superior live-weight gains than the corresponding groups exposed to the more severe winter conditions prevailing at Walcha.

3. The following year (1962-63) a differential feeding programme was adopted for the two Feed groups which resulted in their live-weight gains for the experiment being similar. Although the low ration of hay fed to the Narrabri Feed group to achieve this parity of weight gains introduced a nutritional stress factor in the group, these animals displayed a slightly superior shedding ability than did those in the Walcha Feed group.

The follicle ratio S/P and the fibre ratio Sf/Pf have been determined for various post-natal ages of English Romney lambs in six lamb crops.

A maximum site-sampling error has been determined for use in assessing the degree of significance of differences in values of the ratio S/P determined from successive skin samples from individual lambs. Variations encountered in these Romney lambs in the level of their follicle and fibre ratios, in their rates of change and in the degree of their association with live-weight changes show that rigid conclusions based on data from one lamb crop only are not justified. An intensive study of birth and 8-day old samples has shown that follicles may regress in the early post-natal life of the lamb.

Not all follicle anlagen are initiated before birth and the ‘ceiling value’ of the adult ratio Sf/Pf is not necessarily determined or set pre-natally except in the sense of there being a genetic maximum which may or may not be attained. Low restricted follicle and fibre ratios at birth may increase rapidly postnatally and high ratios at birth may increase little, if at all, post-natally. The follicle and fibre ratio may increase even between the ages of 6 and 12 months.

1. Station progeny tests of twenty-four Ayrshire and twenty-two Friesian bulls were carried out by the British Oil and Cake Mills Ltd. at two centres in Britain between 1953 and 1961. The tests followed the Danish pattern: groups of ten to seventeen daughters were brought to the station approximately 6 weeks before first calving and milked under standardized conditions for an average of 270 days.

2. The place of the station system in modern dairy practice in Britain and abroad was discussed.

3. Earlier results had suggested that milk yield, butterfat percentage, S.N.F. percentage, milking rate and conception interval should be taken into account in a progeny test.

4. Correlations were calculated between the bulls 305-day field ratings for milk yield and fat percentage and their 90- and 270-day station assessments. Possible reasons for the discrepancies were investigated.

5. The selection system employed did not appear to lead normally to the choice of heifers whose dams' milk yield or fat percentage differed from the recorded averages for the breed. In two groups of special cases, deviations were apparent but the effect on the accuracy of the station test was shown to be small. It was concluded that bias due to maternal genetic variation was unlikely to be serious in the general case.

1. In an experiment conducted for the 3 years 1961-63 on a perennial rye-grass and white clover sward a split-plot design was used to investigate the effects of liquid manure (cow urine + water) and its interactions with various levels of nitrogen, phosphate and potash fertilizers on the yield of herbage and on the botanical composition of the sward.

2. On the average the liquid manure contained 0.26% N, 0.44% K and had a pH of 8.6.

3. The liquid manure treatments supplied 0, 50, 100, 200 and 400 lb. N/acre/year and 0, 87, 174, 349 and 697lb. K/acre/year. The fertilizer nitrogen treatments were 0, 100 and 200lb. N/acre; the potash treatments 0 and 166 lb. P/acre and the phosphate treatments 0 and 66lb. P/acre.

The growth and development of a crop of Bulrush millet (Pennisetum typhoides S. & H.) was evaluated by a series of ‘first’ harvests at weekly intervals during the growing season. A final harvest was taken at the end of the season to measure the regrowth.

Tillers emerged from the second, until the 5th week after emergence where full light interception was recorded. Then a marked increase in dry-matter production, internode elongation and leaf area index occurred and a peak growth rate of 44 ± 4 g. of dry matter per square metre per day was recorded during the 9th week. General flowering occurred during the 13th week and at 16 weeks the crop yielded 21,735 kg. of dry matter per hectare.

Regrowth yields were high following defoliations made at an early vegetative stage when the apical meristem was below the cutting height and then declined as internode elongation raised increasing numbers of apices above the cutting height. Extensive areas of the stand died when defoliated as it approached its period of maximum growth rate.

A variety of irrigation régimes were applied to a rye-grass/white clover sward, at several nitrogen levels, in small-plot field experiments.

Herbage yields increased with decreasing soil moisture deficit.

No outstandingly good irrigation régime was found, but some distinctly poor practices were identified, by reference to the yield per unit of irrigation water and to the shape of the annual growth curve. The significance of the results for irrigation practice is discussed.

Tho authors wish to thank Dr William Davies for the provision of facilities, Mr R. J. Canaway and his staff who made the irrigation apparatus, many past and present colleagues who helped with the field work, and members of the Biometrics Department who analysed the data.

1. The point at which continued development of a seed no longer depends upon attachment of the culm to the root system can be termed rootindependence.

2. Serially harvested inflorescences of Lolium temidentum L. were maintained in a glasshouse under the same environmental conditions as standing material. Samples for analysis were taken from harvests and standing material at 2 days intervals to compare chemical changes occurring in seed on standing and severed culms. Analyses for total soluble carbohydrate (T.S.C.) were performed on a single seed basis.

3. Harvests made before the seed T.S.C. maximum resulted in oscillating changes in endosperm free sugar content and these caryopses tended to stabilize at an excessively high value. All later harvests resulted in seed with a final T.S.C. level within 1% of that present in normally matured seed

4. 14C-Sucrose uptake studies showed that tho endosperm T.S.C. requirement was high prior to the seed T.S.C. maximum but that it was very low during the second half of the maturation sequence. It is considered that during this period sugar is only translocated to make good respiratory losses.

Acetic acid, propionic acid, and butyric acid were fed to lambs at a level of 4% of ration over the period of 3-8 weeks of age. The effects of this on weight gains and rumen development were measured.

Separate pathways are involved in the metabolism of C3 and C4 V.F.A. in the rumen wall, and the enzyme systems involved can adapt to high levels of each acid in the diet. The adaptation is longstanding.

The groups of lambs supplemented with propionic acid showed greater weight gains than the other groups.

Propionic acid in some way increases the efficiency of V.F.A. utilization by the animal, possibly by reducing the heat increment, and/or reducing loss of energy as ketone bodies in the urine.

At 9-12 weeks a higher efficiency of food utilization in the acetic acid group was observed.

The stimulatory effect of acetic and propionic acids on papilla numbers was observed at 8 weeks.

Some observations were made on histological sections of rumen papilla at 8, 12 and 16 weeks and their relationship to the diet.

1. The problem of when to apply nitrogenous top-dressings to winter wheat has nover been satisfactorily solved. Detailed field and glasshouse experiments on the effects of nitrogenous manuring on the development of wheat plants, and a number of other experiments involving the nitrogenous manuring of wheat are described and the results discussed.

2. Partial regression coefficients of grain yield on individual components of yield are used to show how variable is the relationship between grain yield and the components of yield.

3. It is concluded that field experiments are never likely to determine an optimum time for nitrogen top-dressing because of the unpredictable relationships between individual yield components and grain yield, and because of the variation in response to nitrogen introduced by seasonal and environmental factors.

1. Three hays of Coastal Bermuda (Oynodon dactylon) grass and three hays of Pangola grass (Digitaria decumbens) from grasses cut at different stages of maturity were used for the determination of digestibility coefficients, voluntary intake, rate of passage through the gut, production of total and individual volatile fatty acids, total counts of bacteria determined microscopically and examination of bacterial types present using Gram-stained smears. The animals used were individually housed sheep.

2. The hays of Coastal Bermuda were significantly superior to those of Pangola from the point of view of digestibility. Significant differences did not exist within grasses.

3. The hays of Coastal Bermuda were superior to those of Pangola from the point of view of intake although this was not significant.

4. No relation was evident between digestibility of the various hays and rate of passage through the digestive tract; it was concluded that intake was not limited by rate of passage through the gut.

1. This paper reports on two experiments, one conducted in the field, the other in a cold cabinet. These had three objectives: (i) to examine the effects, on yield and some components of yield in certain grass varieties, of various combinations of frequency and intensity of defoliation, (ii) to compare these effects in the two environments, and (iii) to assess the value of very small plots.

2. Records were taken of the major environmental variables in the field; the chosen environment in the cabinet was quantified.

3. In the field trial, the cutting treatments comprised all combinations of two frequencies (herbage cut when 8 in. and 4 in. in length) and two intensities (cut back to tiller lengths of 2 in. and 1 in.) plus a fifth treatment of cutting at a silage stage back to a tiller length of 1 in. The first four treatments were also used in the cold cabinet trial. S170 and North African tall fescue were common to both experiments; in addition, S22 Italian rye-graes was included in the field trial. In both trials, plots consisted of four rows of seven plants, square planted at 2 in. x 2 in.

1. A feeding trial was carried out using fortyeight Large White pigs, individually fed in a Danish type piggery. Six different diets prepared at two levels of digestible energy and three levels of crude protein were fed to eight replicates consisting of four hogs and four gilts per replicate. A record was maintained of the weekly live-weight gain and food was given at a defined restricted level in relation to the live weight. Carcass quality was assessed by complete dissection into visible lean, fat and bone etc.

2. Of the main effects, energy, supply was without significant effect upon growth, food conversion efficiency (FCE) or any carcass characteristics except body length which was increased with a high energy level. The protein level in the diet had a significant effect upon the percentage of carcass lean and the killing-out percentage, the higher levels of protein increasing both these measurements significantly. Gilts were significantly superior to hogs in every carcass measurement although hogs grew significantly faster.

1. Twenty feeding and digestibility trials were carried out on seven tropical grasses to determine their nutritional value at different stages of growth, and to study their suitability as possible pasture grasses.

2. Content of crude protein was relatively high at immature growth stages of the forages, and declined rapidly with the onset of flowering.

3. Digestibility of dry matter and gross energy increased in most of the forages tested to the 5-week stage of regrowth but declined rapidly in mature stages of forages tested at 6 or 8 weeks of regrowth. Digestibility of crude protein declined with increasing maturity of the forages.

4. The Nutritive Value Index of each forage was highest at four or five weeks of regrowth. The optimum time to graze the forages tested would occur between 4 and 5 weeks of regrowth, at the stage when flowering commences. This would combine high yield of forage with high nutritional value.