The protozoa in washed suspensions of rumen ciliates were killed by freezing or heating at 49 °C for 5 min before incubation at 39 °C, aeration during incubation or incubation in hypotonic salt solution (30% of ncrmal) and released their intracellular cellulose and amylase during 4–6 h. With the last two treatments it was only necessary to expose the protozoa to the conditions for 2 min to obtain over 50% of maximal enzyme release 4–6 h later. It is suggested that death of the protozoa during exposure to air and/or hypotonic salt solution for short times during drinking and rumination by the host animal could be the explanation for the high postulated protozoal death rate in the rumen. The amylase and cellulase released from the protozoa tested were stable in the presence of mixed rumen bacteria for 1·5 h and could be of importance in the degradation of plant constituents in the rumen.

The fungicides benomyl and captafol separately were tank mixed with each of the insecticides decis (decamethrin), permethrin, and cypermethrin (synthetic pyrethroids) and nuvacron (monocrotophos). The mixtures were tested as foliar sprays at three spraying regimes to protect cow-pea plants against pod and foliar diseases and insect pod borers.

Two sprays, 1·5 kg a. i. /ha of benomyl mixed with 0·75 kg a. i. /tia of monocrotophos at 35 and 49 days after planting, gave the best control of brown blotch, web blight, Cercospora leaf spot and the pod borer, Maruca testulalis. This regime also gave the highest grain yield for two consecutive years. The mixtures were not phytotoxic. Interactions between the test fungicides, insecticides and spraying regimes in relation to disease and pest control and yields are discussed.

Mature sheep fitted with rumen and duodenal cannulae, and fed a pelleted hay diet, were given supplementary phosphorus by continuous infusion into the rumen and the effects on salivary phosphorus secretion, net intestinal phosphorus absorption and faecal endogenous phosphorus excretion were studied. In control periods little phosphorus was excreted in the urine and little increase was seen in response to supplementation, the faeces being the major pathway for excretion. Increasing phosphorus intake led to an increase in net intestinal phosphorus absorption, a rise in plasma phosphate concentration, an increase in salivary phosphorus secretion and an increase in faecal endogenous phosphorus excretion. Overall net intestinal absorptive efficiency for phosphorus did, however, decrease as intake rose so that changes in faecal endogenous phosphorus excretion were in part due to increased salivary phosphorus secretion and in part to a reduction in overall absorptive efficiency. The significance of these changes in relation to the control of phosphorus balance in ruminants is discussed.

This study examines the effects of increased atmospheric carbon dioxide concentrations on vegetative and reproductive growth and partitioning of biomass during pod and seed development of cow pea in controlled environment chambers at 350, 675, and 1000μl CO2/l.

The length of main stem and branches, the number of leaves and branches, and leaf area were all greater at high CO2 than at low CO2 concentration. The appearance of flowers was 10–12 days earlier in high CO2 than in ambient CO2 atmosphere. The senescence of leaves started about 7 days earlier in plants grown at 675 and 1000 μl CO2/l than in those grown at 350 μl CO2/l. The rate of leaf senescence was more rapid in 1000 μl/l than in 675 μl CO2/l. The dry weight of roots, stems and leaves increased with CO2 enrichment, being greater in 675 μl/l than in 1000 μl CO2/l. Plants grown in 675 and 1000 μ1/1 produced more pods and seeds than in 350 μl CO2/l. Total seed weight and number of pods, as well as number of seeds per pod, were significantly greater in CO2 enriched atmosphere than ambient CO2 level. Although CO2 enrichment caused a significant increase in the total number and weight of seeds as well as pods, it did not affect the ratio of seed dry weight to the total dry weight of above-ground plant parts (harvest index). It is concluded from the present investigation that CO2 enrichment significantly enhanced vegetative as well as reproductive growth resulting in the increase in yield and early plant maturation in this leguminous crop.

Tests were to be made to estimate the ED 10 for surface splitting of potatoes; that is the dropping height for which on average 10% of potatoes sustain a surface split. To got good estimates for the ED 10 it is necessary to drop potatoes from heights close to this level. It was decided that a sequential procedure should be used to alter drop heights so that most drops would be made from heights close to the ED 10. Several procedures were investigated by calculation of large-sample properties of estimators and computer simulation of experiments. A procedure was then chosen for the drop tests. Results show that this procedure is easy to use, and also yields satisfactory estimates of ED 10s.

Cell wall preparations from stems of four mature grass species, pangola grass, setaria, sugar cane and barley straw were incubated in nylon bags in sheep fitted with rumen cannulae and fed chopped pangola grass at hourly intervals. After varying incubation times D.M. loss, and incorporation of 35S into microbial cystine on the fibres, were measured. Pangola and barley straw were digested to a much greater extent (ca. 48 and 44%) than sugar cane and setaria (ca. 29 and 23% respectively) and digestion was still continuing after 60 h. With the exception of setaria, microbial colonization of the cell wall preparations peaked after 24 h incubation and then declined. In setaria only a small amount of [35S]cystine was measured, the level of which did not change appreciably after 18 h.

After 24 h incubation, microbial colonization on pangola fibre was about three times that on barley straw and sugar cane. Only on pangola fibre did cystine accumulation, and its subsequent rapid decline, coincide with the development and detachment of fungal sporangia. There was no relationship between the extent of microbial colonization and D.M. loss from the fibres. Sulphur concentrations, both in the plant fibres and rumen fluid, could not explain the greater fungal growth on the pangola cell walls in preference to the other species.

Pelleted seed of the crisp lettuce variety Pennlake was sown on five occasions with units from either the experimental dibber drill designed by the National Institute of Agricultural Engineering or a Stanhay S870 drill. There were three dibber-drill treatments: seeds left in open holes or covered with peat–vermiculite or perlite. Seedling emergence and growth from each sowing of the four drill treatments were compared under different moisture regimes.

There were large differences between drill treatments in emergence percentage, time to emergence of 50% of the seedlings which emerged (t50) and seedling weight at all sowings but there was a significant effect of drill treatment on the standard deviation of seedling emergence times at only one sowing. Of the dibber-drill treatments, only very occasionally did open holes or perlite cover give significantly better emergence than peat-vermiculite cover, which gave the most consistent results. In general, the dibber drill with peat-vermiculite cover gave significantly faster and higher emergence and heavier seedlings than the Stanhay drill. Differences in percentage seedling emergence tended to be greater under dry conditions.

Random inbred lines produced by doubled haploidy and single seed descent have been used to estimate the number of genes or more correctly effective factors (k) controlling quantitative characters in barley. Estimates of k obtained by various biometrical methods are generally an underestimate since the effective factor may be considered a unit only in a temporary sense. In the past, estimates of k have been used to predict the range of inbreds extractable from a cross. Alternative and efficient methods are now available to predict the number of inbreds expected to exceed any given standard. Under these circumstances the need to estimate the number of genes is questionable.

Coating and modified atmosphere treatments reduced light-induced greening of King Edward potatoes. Although ‘Pro-long’ coating and 5% O2 treatments gave more complete inhibition of greening in some tubers, the variability of response was greater and the mean response less than for treatment with 15% CO2, 21% O2. The pattern of greening in the different treatments suggested the presence of O2 gradients within the tuber flesh. Coating caused small internal atmosphere changes, with CO2 content being negatively correlated with chlorophyll content. Larger changes achieved by modifying the external atmosphere of such tubers increased greening suppression. However, the magnitude of response to coating and to the low O2 treatment varied with maturity and growing conditions. The success of coating for inhibition of greening in potatoes will depend upon the physiological variability of the tubers to which it is applied.

Early and late, and short and tall lines were selected from a cross between the winter wheat varieties Norman and Talent. All short selections carried the Rht2 dwarfing gene while the tall ones did not. The selections were compared in field experiments at the Plant Breeding Institute in Trumpington and at The Murrays Experimental Farm of the Scottish Crop Research Institute near Pathhead. In one of the experiments at Trumpington the plots were automatically sheltered from rain and the effects of withholding water before anthesis and withholding water during grain filling were studied.

In all trials the early selections gave grain yields equal to or greater than the late selections. There were no differences in number of ears/m2 or in number of grains per ear between the early and the late selections. Mean weight per grain of the early selections was greater than that of the late selections.

The short selections gave grain yields equal to or greater than the tall selections, except when water was withheld during grain filling in the sheltered experiment. There were no differences in number of ears/m2 between the short and the tall selections. The number of grains per ear was greater and mean weight per grain was less for the short selections than for the tall selections.

It is concluded that for general fitness to U.K. conditions, new varieties should be semi-dwarf, but earlier than current varieties.

Field experiments were carried out to study the effect of a highly purified paraffinic oil on the efficiency of some insecticidal sprays used for the control of thrips and cotton leafworm. The results show that the oil used separately at the rate of 7·51/ha significantly reduced the population of thrips, but oil-insecticide combinations were superior to oil or insecticides applied alone. The mineral oil increased the efficiency of candidate insecticides against both thrips and cotton leafworm two-fold or more.

All 53 lettuce cultivars inoculated with cucumber mosaic virus became infected. Leaf mosaic symptoms were generally mild and unreliable for distinguishing degrees of resistance between cultivars. Yield reduction was the most satisfactory criterion for evaluating resistance, with reductions in individual cultivars ranging from 8 to 50%.

The growth of 26 castrated ram lambs was severely restricted for the first 5 weeks of post-natal life. Subsequently, these lambs (group R) were fed ad libitum on the same high quality diets as fed to a control group of 26 similar lambs (group C) from birth.

At regular intervals lambs were weighed, X-rayed and surface measurements were aken. At the age of 12–14 months, covering the body-weight range of 63–83 kg, ten animals from each group were slaughtered for dissection and measurement. These data were used to compare the skeletal growth of the two groups of animals. Measurements of skeletal dimensions by dissection were compared with measurements obtained by surface and radiographic techniques. After slaughter, the brain, kidneys, liver, the left semitendinosus and gastrocnemius muscles from each lamb were used for the following analyses: dry matter, ash, fat, protein, DNA and RNA contents.

At the end of the period of feed restriction, there was a mean body-weight difference between groups of 9·2 kg (63%).This represented a weight for age difference of 36 days, which was reduced to 29 days at the conclusion of the experiment, restricted animals not having fully recovered from the period of underfeeding.

Clean wool production per day was significantly (P < 0·05) depressed by the restricted feeding, lambs in group C producing 11·07 g/day during the first shearing interval compared with 10·07 g/day from group R lambs. There was no difference between groups in clean wool produced during the second shearing interval.

Restricted feeding caused a reduction in the rate of bone growth but, during subsequent regrowth (apart from minor exceptions), it did not disrupt the relationship of skeletal dimensions to fleece-free body weight (FFBW). Surface measurements showed that during recovery, group R animals were significantly narrower (P < 0·05) at the hips and wider (P < 0·05) at the shoulders than group C animals. The results obtained from the radiographs for length of foreleg were similar to those obtained from surface measurements. Metacarpal width (measured at two sites) and weight were significantly greater in group R than in group C animals. With the exception of width at hips and although not statistically significant (P > 0·05), the skeletal measurements of group R were slightly greater than those of group C animals. This may have been due to the slightly greater age of group R at slaughter and to an effect of restricted feeding.

There was no significant difference between groups R and C in the DNA content of the tissues investigated. Neither was there any difference between the groups in cell size as indicated by the protein: DNA and tissue weight: DNA ratios. Even though hyperplasia and hypertrophy were slowed by the period of restricted feeding, this effect was transient, full recovery apparently occurring as indicated by tissue weights and composition at the time of slaughter. The RNA and the protein contents of the tissues were similar in both groups. In addition, the similarity of the RNA:DNA ratios suggests that tissues in each group possessed the same capacity to synthesize protein.

In practical terms, the recovery of group R was associated with a time lag in reaching any particular body weight and a loss of wool production. Both of these consequences are of economic importance. At the time the experiment ended, no skeletal stunting was evident in these sheep and, apparently, they had recovered in terms of cellular growth.

The endogenous faecal loss of P has been investigated in growing lambs given diets either grossly deficient, moderately deficient or just adequate in P. This loss was found to increase in direct relation to the increased P intake, in spite of the high P requirements of the deficient animals, which suggests that some increased loss with increased P intake is inevitable. Results throw doubt on the validity of the assumption made by the Agricultural Research Council (1980) in their calculations of P requirements, that the endogenous faecal loss of P is maintained at a constant level equal to that which occurs at zero P intake, until requirements are met.

Even on the diet which was, according to Agricultural Research Council (1980) recommendations, just adequate in P, lambs were unable to retain the expected amount of P commensurate with their growth. This inability to retain P was not due to a failure of P absorption, since the efficiency of absorption from this diet was higher than the value used by the Agricultural Research Council (1980) in their calculations. Rather, it must have been due to an inevitable endogenous faecal loss of P that was considerably higher than the value assumed by the Agricultural Research Council (1980).

It is suggested that in future the value of endogenous faecal loss used in calculations of P requirements is the minimum one that allows a particular requirement to be achieved.

In each of three experiments, five seed lots, representing multigerm, monogerm, open pollinated and hybrid types, were grown at three plant densities and the time of seedling emergence, uniformity of within-row spacing, the weight of individual shoots and roots at four occasions were recorded.

Seedling emergence was more rapid in a May-sown experiment than in a March-sown experiment. The monogerm seed lot had a lower standard deviation of emergence time in the May-sown experiment and in all experiments had a more uniform within-row spacing than the other seed lots, but there was no consistent relationship between these two attributes and uniformity of root weight.

The mean weight of shoots and roots increased rapidly until 600 day °C above 6 had accumulated. The yield of shoots then remained constant at about 30 t/ha at 47 plants/ m2 and at about 40 t/ha at 188 plants/m2. The weight of roots increased throughout the experiments and yields of over 100 t/ha were achieved. The monogerm seed lot gave a ceiling shoot yield about 20% less than that of the other seed lots, whereas there were no large or consistent differences in root yield between the different seed lots. Shoot yield increased with plant density, especially at very early harvests, whereas root yield showed a variable response to density. At early harvests in all experiments, root yield increased with increasing density; at late harvests in one experiment, yield de-creased with density, but in another there was no marked response to density.

Coefficient of variation (c.v.) of root weight was only about 30% in young unthickened roots, but in older thickened roots was between 70 and 117% at 47 plants/m2, and in-creased to over 180% at 188 plants/m2. The c.v. of root weight of the monogerm seed lot was approximately 20% less than that of the other seed lots.

In a fourth experiment, plots were thinned to leave within each row either a uniform or a clumped distribution of seedlings of either uniform or variable size. Uniformity of spacing had no effect on variation in root weight 126 days after sowing, but selecting for seedlings of uniform size reduced the c.v. of root weight by approximately 20%.

An account is given of vegetational and yield changes occurring in sown swards of Lolium perenne L. to which four alternative management treatments were applied for 8 years.

With infrequent cutting (four cuts per year), and a fertilizer nitrogen rate of 188 kg/ha per year, there was a substantial invasion by Agrostis spp. At 376 kg N/ha under cutting the main invader was Agropyron repens (L.) Beauv. with a lower proportion of Agrostis. After cutting at 752 kg N/ha, the swards became dominated by A. repens. With rotational sheep grazing, at 376 kg N/ha, the main invader was Poa annua L., although the proportion was low and L. perenne remained the dominant species. The plant successions which occurred with each type of management as the swards became older had little influence on the yield or quality of herbage under grazing or cutting.

Because sward age is confounded with the influence of year-to-year environmental variation, the experiment was designed to enable independent assessments of these factors to be made. Sequential sowings were made to produce an array of swards between 1 and 7 years old. Year-to-year fluctuations in the pattern of herbage production were quantified after allowing for the progressive increase in sward age. Similarly, the influence of age was investigated by adjusting yields for year effects, and comparing swards of different ages in the same year.

Year-to-year variation in the total yield of dry matter was much greater than variation attributable to sward age. There was similarly more variation due to year than to age in the yield of D.M. at any one season. In the most extreme comparison, the D.M. yield at an individual defoliation in one year was 2·8 times the lowest yield at the same season in a different year, whereas the yield at the same season varied by a factor of up to 1·5 between swards of different ages.

The influence of age on quality was quantified for cut swards only. There was an age effect only at the first cut, when the percentage of digestible organic matter (DOM) declined with age, and herbage nitrogen concentration increased, at the lowest level of fertilizer N, but these changes did not occur at higher N levels. Annual yields of DOM declined significantly with age, but only at the highest N level, and there were no significant changes in the annual yield of herbage N.

Comparisons were made of the cumulative D.M. yields for several years of young swards, resown every 3 years, and undisturbed swards, up to 7 years old. Young swards gave a higher yield during the first two years after sowing, but the advantage was lost in the period of ploughing and establishment, during which time the undisturbed swards achieved a small advantage in cumulative yield. Cumulative yields of DOM and N from young swards were not sufficiently different from those of older swards to suggest that there would be an advantage from regular resowing. A theoretical analysis was made to predict the long-term yields of D.M. and DOM from different renovation strategies at yearly steps from 2 to 7 years. This suggested that ploughing and resowing gave little or no advantage in productivity over swards which were not renovated before age 7, and resowing too frequently gave a loss of yield.

The paper contains an appendix by A. Smith and R. E. Deriaz describing a method used for the correction of analytical results obtained for variable contamination of herbage samples by extraneous materials.

A series of 24 standardized, replicated field trials comparing 47 fungicidal treatments for the control of spring barley mildew have been analysed. The joint analysis has enabled stronger conclusions to be drawn about the relative efficacy of treatments than examination of individual trials. To increase sensitivity the trials were divided into those with high or low mildew pressure. Under high mildew pressure, the treatments which gave the greatest control of mildew also gave the highest yields. However, within any given treatment the yield response appeared not to be closely related to the degree of mildew control achieved. It is concluded that effective fungicides may have a phytotonic effect as well as a mildew control effect.

The improvement of milk production by the establishment of four specialized lines and subsequent within-line selection over a 7-year period under grazing conditions at Kraim station in mid-Syria is described. The specialized line showed a substantially higher total milk production amounting to a mean 25% superiority over the control line in 1979–81.

The heritability of total milk yield as estimated from paternal half sib analyses was 0·53 ± 0·169 for 2-year-old ewes and the genetic correlation of a single maximum daily yield record (+ 0·93) with total yield indicates the possibility of simplified selection procedures for this trait.

The effect of several other factors (for example, ewe age and season of lambing) on various aspects of lactation in Awassi ewes is reported.

Three experiments were carried out to measure grain and biomass yields of spring barley breeding lines and varieties. Leaf diseases were controlled by applying proprietary fungicides and in some treatments plants were supported by nets to prevent lodging. The trials, grown in 1982 and 1983, compared the grain and biomass yields of 14 breeding lines and two varieties with and without support. In a third experiment, comparing three lines and the varieties Triumph and Egmont, all the plots were supported and in addition each experimental plot was flanked by guard plots of the same genotype to minimize inter-plot competition.

In the supported plots of all three experiments, three breeding lines, SB 543–3, SB 71–2 and HSB 258–93 produced significantly greater biomass yields than the mean of the varieties Triumph and Egmont. All three breeding lines were taller and had lower ratios of grain to grain + straw than the controls. Measurements were made of the accumulation of dry matter, chlorophyll content at anthesis and date of ear emergence but no single factor could be identified which was associated with increased biomass in these lines.

The grain yield of the semi-dwarf, lodging-resistant variety Triumph was reduced by an average of 0·24 t/ha by the support treatment compared with the non-supported control. The results from the third experiment suggested that the yield of Triumph was reduced by inter-plot competition by about 10% in relation to the other entries in the trial.

It is suggested that the high biomass lines identified here could be used as parents in a breeding programme to produce varieties with high yield if this high biomass could be combined with a high ratio of grain to above-ground dry-matter yield.

Differential growth from 1 to 20 weeks of age was studied on 320 rabbits from two lines (New Zealand White and California) and both sexes by means of the allometric equation log y = log a + b log x. Regression lines were fitted to the evolution of organs (blood, skin, thymus, heart–lungs, liver, kidneys and alimentary tract), carcass, tissues (bone, lean and fat) and anatomic components (head, breast and ribs, loin, abdominal wall, fore and hind legs) relative to empty body weight; stomach, caecum and intestines relative to alimentary tract; bone and lean groups relative to total bone and lean and fat depots relative to total fat.

The convenience for a correct description of relative growth of determining both the quantitative growth, in order to apply the allometric equation only to the real growth period of each component, and the possible existence of allometric changes, is discussed.

The results for each component are presented and discussed. There were no significant differences due to line, and sex had a significant influence (P < 0·001) only on the relative growths of total fat, lean content in the loin and hypodermic fat. All the components, with the exception only of thymus, presented a change in their allometric coefficients. These changes for most components, except fat depots, were concentrated in a small interval of time (4–8 weeks of age) between weaning and the inflexion point of the body weight growth curve.