The quantity of in vitro digested cell wall was determined in the separated leaf and stem of Digitaria decumbens (pangola grass) fertilized at three different levels of nitrogen and cut after two different periods of regrowth. The treatment means ranged from 39·6 to 41·5 g digested cell wall per 100 g forage organic matter in leaf, and from 37·5 to 41·6 g in stem. For both leaf and stem the lowest mean amounts of digested cell wall were associated with the highest levels of fertilizer and the longer periods of regrowth. The results for nitrogen fertilizer were consistent with those from previous in vivo digestibility experiments, but when the effect of the total cell wall on digested cell wall was taken into account there were inconsistencies. The previous in vivo digestibility data were used in conjunction with the present results in support of a view that interpretation of digestibility data for grasses is best made by reference to a constant digested cell wall of 39·5 g/100 g forage organic matter.

Border Leicester ewes were kept in three contrasting photoperiodic environments, the rhythm at latitude 30° 32′ S (group 1) - 12 h light: 12 h dark interrupted by 6 weeks of continuous light (group 2a) and 12 h light: 12 h dark (group 2b) - from August 1972 to September 1973. In group 1 all ewes exhibited oestrus compared with 87·5% and 57·1% in groups 2(a) and 2(b) respectively. The mean number of oestrous periods per ewe ranged from 4·4 in group 1 to 3·0 in group 2(a) and 1·0 in group 2(b). It is concluded that the non-fluctuating light rhythm had an adverse effect on the reproductive potential of the treated groups and that Border Leicester ewes are dependent on a fluctuating light rhythm for normal reproductive function.

A method is suggested for estimating the mean bud size and standard deviation of a sample of sprout buds, separated into size grades by the use of riddles. From the standard deviation a potential size fraction is estimated, being the fraction of the buds occurring in a size grade of 10 mm width if the mean bud size were located at the mid-point of the grade. This estimate of bud size uniformity was independent of date of sampling for a period of at least 4 weeks.

The potential size fraction was increased by stopping (apical bud removal) and in some cultivars an optimum stopping date was indicated. Increased plant density also increased the potential size fraction, particularly in unstopped crops. Between-plant variation in bud size was significantly greater for the hybrid Thor than the outpollinating Seven Bills but within-plant variation was the more important component of overall bud size variation and was greatly reduced by stopping and by increased plant density in unstopped crops. Mean bud size at any harvest date was increased by early stopping and lower plant density.

It is concluded that the date of stopping should be chosen to minimize bud size variation and the plant density varied to spread maturity.

The relationship between the voluntary dry-matter intake of grasses and their in vitro digestibility (DOMD), chemical composition and susceptibility to enzymic hydrolysis was examined in two experiments. The grasses were artificially dried and represented a range of species and varieties cut at various growth stages.

In both experiments some 70% of the observed variation in intake could be attributed to differences in in vitro digestibility between the grasses and between the growth stages when harvested. Estimations of acid detergent fibre, pepsin solubility and cellulose generally accounted for less than 70% of the variation in intake.

The enzyme digestion techniques, on the other hand, accounted for up to 79% of the variation. The content of enzymically unhydrolysable cell wall gave the highest correlation with voluntary intake (r = −0·88 and −0·89, residual standard deviation 5·5 and 6·2, for the two experiments).

It is concluded that simplified techniques based on cellulase digestion of plant material may be advantageously applied to breeding programmes with the expectation of identifying material high in digestibility and with good intake characteristics.

A method of including urea into whole grains is described. The whole grains were found to absorb completely a saturated solution of urea.

The method gave the different cereals examined (barley, oats, wheat and maize) a homogeneouis distribution of urea and increased the voluntary intake of whole grains by lambs. The evolution of NH3 in the rumen liquor was slightly slower when urea was absorbed into the grains than when it was included as urea crystals. The N content in the urea-treated grain was not changed after 6 months of storage.

The wool weight/m2 of LK progeny arising out of LK × LK matings (approximately a quarter were HK and were excluded) and HK progeny arising out of HK × HK matings (all were HK) of two coarse-wool producing breeds of sheep, Marwari and Magra, were compared with the mid-parent values. LK progenies produced significantly more than the mid-parent value in both the breeds, but there was no increase in HK progeny. The difference in wool weight between the HK progeny and their mid-parent value tended to be less for Marwari whereas it was much less for Magra breed.

The results suggest that improvement in wool weight of sheep can be made by maintaining LK stock and mating LK × LK, culling the HK arising out of these matings in each generation.

An analysis of marketable yield of sprouts is suggested in which the components are: number of plants/m3, number of buds/plant, acceptable size fraction, acceptable quality fraction and mean weight per marketable bud.

The number of buds per plant was dependent on date of stopping but was not greatly affected by plant density. This component was not found to limit yield.

Acceptable size fraction was related to the standard deviation of bud size and increased to a maximum at the time of optimum bud size. The maximum acceptable size fraction obtained from field samples could be reliably predicted from measurements of the standard deviation of bud size.

The acceptable quality fraction was of particular importance in later harvested crops and at higher plant densities. It was highly dependent upon cultivar but was little affected by stopping treatment. Unacceptable buds occurred most frequently at the base of the stem and it is argued that the importance of the blemishing diseases responsible for these losses has been increased by the single-pick harvesting technique.

The optimum plant density was related to the expected date of harvest but the practice of delaying maturity by increasing density is limited by the decreased acceptable quality fraction. Crops for harvest in October and November should undoubtedly be stopped both to reduce bud size variation and to stimulate bud growth.

A field experiment was made on a sandy clay loam soil during the rainy seasons of 1967 and 1968 to study the relative efficiency of urea, N-serve treated urea, AM-fertilizer, IBDU fertilizer and nitrogen-enriched coal for the rice variety IR-8. Nitrogen-enriched coal supplied very little nitrogen to rice. All other materials were superior to urea. Largest yield of rough rice and nitrogen uptake was obtained with IBDU. The yield of rough rice given by AM-fertilizer was equal to that with IBDU in 1968; in that year both AM-fertilizer and N-serve treated urea supplied as much N to the crop as IBDU. Yield of straw showed no significant difference between these three materials in either year. Ammoniacal and nitrate nitrogen in soil at flowering and at harvest of the rice was most in plots receiving IBDU followed by those receiving AM-fertilizer, N-serve treated urea and urea. Mineral nitrogen in plots receiving N-enriched coal was only slightly more than in control plots.

The oestrogenic activity, coumestrol and formononetin content of white clover collected during the months May to December 1970 and 1971 was assayed in mice. The results showed considerable variations in oestrogenic activity which did not seem to be associated with a specific time of year or quantitatively related to the coumestrol content of the pasture.

In order to assess the potential value of milk conductivity sensors for the detection of subclinical mastitis, measurements have been made manually on quarter foremilk samples for 10–74 days from 44 cows in two herds. Some measurements were also made of quarter cell counts and yields but the true status of the cows was established by bacteriological examination near the end of each run.

For uninfected cows, conductivities of the four quarters tended to move in parallel from day to day whereas for infected cows there were usually substantial departures from parallelism. A statistic which is a measure of departure from parallelism is the quarter × day interaction mean square (I.M.S.), the magnitude of which was used to discriminate between infected and uninfected cows. Using conductivity data obtained at the time of the bacteriological examination, I.M.S. correctly identified all 19 un-infected cows and 24 out of 25 infected cows, the single misclassified cow being only mildly infected. The procedure was further tested on data obtained from one of the herds a year later. In this case, using the I.M.S. limits established the year before, 14 out of 18 infected cows were correctly identified, the four failures being only mildly infected. With nine uninfected cows, there were three false positives but these cows were all pregnant and had been lactating for 44 weeks. Although special limits may have to be set for cows in late lactation, two of these animals had been infected during the lactation, so that conductivity changes may reflect past damage to the udder.

The same data used to set I.M.S. limits were also examined in simpler ways that required little or no calculation. These were ‘differential conductivity’ (the quarter with the highest conductivity divided by the value for the lowest), ‘absolute conductivity’, ‘mixed conductivity’ (mixed foremilk from all four glands) and ‘out-of-balance conductivity’ (the product of the conductivities of the fore quarters divided by the product of the hind quarters or vice versa). These methods of analysis were all less sensitive than the I.M.S. test for parallelism. Differential conductivity, absolute conductivity and mixed conductivity all detected severe cases but missed more mild cases. Out-of-balance conductivity was much less satisfactory because it missed some severe cases.

The effect of sowing date and nitrogen on tillering patterns, survival and contribution of reproductive tillers to grain yield of standard and Mexican wheat cultivars were studied for two seasons.

Maximum number of tillers/plant, 3·2–4·5, was observed after 40 and 27 days from sowing for 1970–1 and 1971–2 respectively. The number of ears/plant was 1·4 at the end of the growing season. Varieties differed in tillering, and LRN10 and Giza 155 produced more reproductive tillers than Falchetto and Mexipak. Nitrogen application increased tillering efficiency, i.e. ratio of fertile to total tillers produced. Only 26% of tillers appearing in the axil of the first true leaf (T1) and 10% of tillers in the axil of the second true leaf (T2) survived to produce ears. The high mortality of tillers was attributed to high air temperature prevailing during the growth period (33 °C by day; 18 °C by night). Eared tillers did not die and were self supporting because of the photosynthesis by the ear.

Grain weight/tiller was positively correlated with tiller dry weight at heading, r= 0·76–0·96. Main shoots contributed about 81% of the total grain yield and 19% came from T1 and T2 tillers.

During 1970–3 three experiments with winter wheat, three with spring barley, two with permanent grass and one with perennial ryegrass measured the effects of a liquid N-fertilizer (26% N) sprayed over the leaves either alone or with a herbicide added to it. ‘Nitro-Chalk’ (21% N) was used as the standard for comparison. The liquid N-fertilizer was made from urea and ammonium nitrate; the herbicide was a mixture of dichlorprop and MCPA. Each experiment tested all combinations of the two N fertilizers applied to give 38, 75 or 113 kg N/ha without the herbicide and with either 2·8, 5·6 (recommended dose) or 8·4 1/ha of herbicide. The 24 treatments were applied to winter wheat at growth stages 4–5 of the Feekes scale, to barley at growth stage 5 and to grass in late spring and again to regrowth after cutting.

Herbicide alone sometimes scorched the leaves but seldom badly. Liquid N-fertilizer nearly always scorched the leaves and the amount of scorch was increased by adding herbicide; scorch also was increased by increasing the amount of either and so was most severe when most liquid fertilizer and most herbicide were sprayed together; this damage did not decrease yields appreciably except when only 38 kg N/ha was given.

Spraying the herbicide with the liquid fertilizer always gave slightly better weed control than herbicide alone in the wheat, but not always in the barley; in the grass, weed control was no better than from herbicide alone.

‘Nitro-Chalk’ gave larger yields of wheat grain than the liquid N-fertilizer did in seven of nine comparisons without herbicide and in 20 of 27 with it, of barley grain in five of nine comparisons without herbicide and in 15 of 27 with it, of permanent grass in 25 of 27 comparisons without herbicide and in 70 of 81 with it, and of perennial ryegrass in nine of nine comparisons without herbicide and in 25 of 27 with it. Thus herbicide did not alter the advantage that ‘Nitro-Chalk’ had.

Percentages of N in the crops were larger with ‘Nitro-Chalk’ than with the liquid N-fertilizer but were changed little by herbicide.

Nitrification of aqueous ammonia, and its uptake by grass, are slower when the amount of NH3-N injected per unit length of slit is increased and as a result crop yield is spread more evenly over the growing season. Measurements of the amounts of NH4-, NO3- and NO2-N in the soil, made at intervals from February until October, and computed diagrams showing their distribution in soil under grass, are presented. We conclude that, at average current rates of application, most of the aqueous ammonia used for grass in England and Wales is probably not applied along the injection slit in sufficient quantity to allow it to persist throughout the summer.

From monogerm sugar-beet seed as harvested non-viable fruits have to be eliminated, multigerm ones rejected and the size made sufficiently uniform for use in precision drills. Seed which had been gently rubbed to remove some of the cortex was graded for diameter, thickness and by aspiration, either singly or in combination. Effects of grading were determined by laboratory germination tests, radiography and field sowings in which seedling emergence and crop growth and yield were recorded.

Grading by thickness was effective in removing multigerm fruits. Grading by aspiration and diameter rejected non-viable seed and reduced the variation in size. By combining all three grading methods, samples of seed of 80% germination and 90% monogermity were produced, provided the seed lot as threshed gave at least 50% germination. True seed weight increased with fruit diameter but only the first aspiration was effective in removing light true seeds. Radiography showed that both aspiration and, to a less extent, grading by diameter were effective in removing most empty fruits but neither eliminated those with shrivelled seed. The field experiments confirmed that increase in fruit diameter or aspiration gave more seedlings. Even at uniform, high plant density, sugar yields were less from the smallest (less than 3 mm diameter) than from the other grades of seed. The initial aspiration also improved sugar yield but further aspiration decreased yield.

Fifty-nine Scottish Blackface female sheep were used to measure the effects of age and state of permanent incisor dentition on the loss of body reserves during pregnancy and lactation and on the ability to replenish them during the dry period, while grazing hill pastures. There were 27 6½-year-old sheep (11 with sound mouths and 16 with broken mouths), 16 5½-year-old sheep (with all permanent incisors clipped to gum level) and 16 2½-year-old sheep. Samples of sheep from each group were slaughtered at the beginning of pregnancy and in mid-lactation, and samples of those with broken mouths and of 5½-year-old and 2½-year-old sheep at the end of the subsequent dry period. Carcasses were dissected into soft tissue and skeleton fractions and the changes in chemical composition of the former are presented. The sheep were weighed at approximately monthly intervals; lamb birth weights and growth rates to 6 weeks of age were recorded.

There was no evidence that broken mouth or the clipping of the teeth impaired the ability of sheep to maintain body weight in early pregnancy, but there was evidence that sheep with broken mouths lost most weight in late pregnancy. There was also evidence that sheep with broken mouths may have poor milk yields as judged by the growth rates of their lambs but more data are needed to establish this conclusion.

The young sheep were most able and the sheep with the broken mouths least able to resist catabolism of their soft tissue protein during pregnancy and lactation. The losses amounted to 18, 20, 21 and 30% in the 2½-year-old, 5½-year-old and 6½-year-old sheep with sound mouths and with broken mouths, respectively. The young sheep replaced their protein reserves more rapidly than the sheep with broken mouths. It is suggested that the ability to restore body protein may be related to maturity.

There was evidence for a redistribution of protein in the body of undernourished sheep in mid-lactation. The soft tissues were overhydrated at this time but much of the fluid which accumulates during pregnancy had apparently cleared.

Two digestibility and balance experiments were carried out using 12 growing heifers to compare first and second cut silages fed alone or with supplementary barley or barley and urea, and to measure the effects of the addition of urea to silage and barley diets at three levels of dietary energy.

Digestibility of gross energy (GE), N and modified acid detergent fibre (MADF) was higher in first cut than second cut silage diets, and although D.M. intake was slightly lower, metabolizable energy (ME) intake was significantly higher. Inclusion of urea increased the apparent digestibility of N but had no effect on the intake of D.M. or ME. Nitrogen retention was significantly higher on first cut than second cut silage diets and was significantly increased by the addition of urea when N intake was low. The relationship between daily N retention (DRN), ME intake (DME) and digestible N intake (DAN) was represented by an equation of the form:

DRN = C–2·164DME+0·447DAN–0·00512DAN2+0·0487DMExDAN,

but when apparent biological value (ABV) of dietary protein was high DRN was linearly related to DAN. These equations were used to estimate requirements for digestible N. The results of rumen fermentation studies suggested that the response in DRN to urea inclusion could be partially explained by the low rumen ammonia values on silage and barley diets.

Several models have been proposed in the literature relating gain per animal (Ya) and stocking rate (x) from grazing experiments. Results from an experiment in which tropical pasture species were grazed continuously by beef cattle at a number of stocking rates (Jones, 1974) were used to examine this relation. A simple linear model of the form y = a − bxfitted the data well. Production per hectare (Yh) was related to stocking rate by yh = ax − bx2.

Stocking rate for maximum gain per hectare (the optimum stocking rate) on each pasture could be calculated from the linear regression by a/2b.

Data from a number of stocking rate experiments in tropical and temperate environments were examined to see if this relation held for a wider range of stocking rates and pasture types. Results were expressed on a common basis by calculating the optimum stocking rate and relating ratios of gain to ratios of stocking rate relative to that at the optimum.

For gain per animal, the overall relation obtained: Ya = l·999–0·999x (r = –0·992; P < 0·001; n = 114) did not differ significantly from the expected linear relation: y = 2−x. Linearity was established over the range 0·18–2·0 times the optimum stocking rate. At rates greater than twice the optimum, animal gain was negative. When expressed as gain per hectare (Yh) the quadratic equation Yh = 2x − x2 gave a good fit to the data over this range.

It is suggested that, since the relation between production per animal and stocking rate (animals/ha) remains linear over a wide range of stocking rates, two rates of stocking (with replication) may be adequate for grazing experiments and these would not have to span the optimum stocking rate in order to predict gain at the optimum stocking rate.

The chemical composition of the skeleton, mandible and 4th lumbar vertebra of 59 Scottish Blackface female sheep from a ‘broken mouth’ farm was determined. There were 27 6½-year-old sheep (11 with sound mouths, 16 with broken mouths), 16 5½-year old sheep (with loose incisor teeth which at the outset of the experiment were clipped to gum level) and 16 2½-year-old sheep. Sheep from each group were slaughtered at the beginning of pregnancy and in mid-lactation and from those with broken mouths and from the 5½-year-old and 2½-year-old groups at the end of the subsequent dry period. The sheep grazed hill pastures and received an energy supplement during late pregnancy and early lactation.

There were no differences between the 6½-year-old sheep with broken mouths and those with sound mouths in total skeletal mineral content or in the density of ash (ash: volume ratio) or organic matrix (organic matter: volume ratio) in the mandible and lumbar vertebra at the beginning of pregnancy or in mid-lactation. Nor were there differences in the density of ash or organic matrix between any groups, although the skeletons of the 6½-year-old sheep were larger. The lumbar vertebra, which is rich in cancellous bone, had a lower ash and organic matrix density in the 5½- and 2½-year-old sheep. It is suggested that bone mineralization may proceed slowly on such hill pastures.

The rates of repletion of the skeleton during the dry period, 0·35, 0·47 and 0·66 g Ca/day, respectively, in the 6½-year-old sheep with broken mouths, 5½-year-old and 2½-year-old sheep were much slower than rates given in the literature for sheep under controlled conditions. It is suggested that factors other than the major nutrients, protein, Ca and P, may be limiting repletion of the skeleton.

Recovery of the ash density of the vertebra was not complete at the end of the dry period. This was especially so in the sheep with broken mouths and resulted mainly from a failure to replace bone organic matrix.

The implications for the development of broken mouth of cyclical changes in the density of cancellous bone and of evidence that the ability to maintain and to remineralize the skeleton deteriorates with increasing age, are discussed.

Varieties of beans (Phaseolus vulgaris L.) were grown under both greenhouse and field conditions to determine the causes of inter-varietal differences in susceptibility to sodium toxicity injury. Varieties varied greatly in plant growth and survival on sodic soils under arid conditions. Environmental conditions were very important in determining differences in survival. Chemical analysis of plant parts indicated that varieties accumulated different amounts of sodium in the roots, stems and leaves. Sodium concentration in stems and leaves of sodium-tolerant varieties was controlled to a low level at lower degrees of injury.

Winter bean crops, mainly of the variety Throws MS, were surveyed for proportions of cross-bred seed, using hilum colour as a genetic marker. In 1971 a significantly greater proportion of cross-breds was detected in random samples taken from the centre than in similar samples from the border of three fields and from the total of all seven fields. An hypothesis is proposed that pod setting at the centre was limited more than at the border by a factor such as plant competition and chocolate spot at a time when selfing was enforced due to a general lack of bee visitation, or else inbred embryos aborted more under the stress of disease in the centre. No differences between centre and border were found in 1972 except for a greater proportion of cross-breds from the border of a Maris Beagle field and this only applied to parent plants of certain genotypes.

Significant differences were also found between fields and between seasons. There was a significant regression of percentage selfing on field size but there was no evidence that bees failed to penetrate to the centre of large fields.

Implications for variety development, testing and purity are discussed.