Field experiments consisting of three mulch treatments (no mulch, straw mulch and dust mulch) and six transpiration suppressants (no suppressant, kaolin, phenyl mercuric acetate, atrazine, mobileaf or alachlor and 2-chloro ethyl trimethyl ammonium chloride) were conducted under dryland conditions during the summer rainy seasons (July–November) of 1976, 1977 and 1978. Compared with no mulch, straw mulch increased yield in all 3 years, water use efficiency in 1977 and 1978, and uptake of N and of P in 1977 and 1978. Dust mulch had only a marginal advantage. Amongst transpiration suppressants, only kaolin and atrazine had a marked effect. Both these chemicals increased grain yield, water use efficiency and uptake of N and P, compared with no suppressant.

In a 3 × 3 latin-square design experiment, 12 British Friesian steer calves with rumen cannulae were offered three red clover silages to appetite, either alone or with a urea supplement of 18.9 g/kg total dietary dry matter (D.M.). The silages were prepared from a second cut of red clover using additives of 2·11 formic acid/t fresh crop together with formaldehyde at 0, 31 or 123 g/kg crude protein (CP) in the crop.

The control silage was well preserved, as indicated by a low content of volatile fatty acids and ammonia N. Formaldehyde treatment generally restricted silage fermentation, although there was an increase in the content of butyric acid at the intermediate level of application, and an increase in 2, 3-butanediol content at the high level of application. A decline in ammonia-N content and an increase in insoluble-N content, with increasing level of formaldehyde application, indicated that formaldehyde had been effective in reducing protein degradation in the silages.

Formaldehyde treatment depressed intake, the apparent digestibility of D.M., organic matter (OM), N, cellulose and energy, and N retention, the effect being particularly evident at the high level of application. Behavioural observations showed an increase in eating time on the formaldehyde-treated silages. Urea supplementation increased intake of the formaldehyde-treated silages, but did not influence intake of the control silage, and increased N retention on all silage diets. Apart from an improvement in apparent N digestibility, urea supplementation did not influence the digestibility of other dietary components.

Within the rumen, formaldehyde treatment reduced ammonia-N concentration and the molar proportions of propionate and butyrate, and increased the molar proportion of acetate. The rate of D.M. and cellulose disappearance from treatment silages suspended in the rumen in nylon bags was reduced by formaldehyde treatment, the effect being most evident at the high level of formaldehyde application. A similar effect on rate of D.M. disappearance was observed when the control silage was placed in nylon bags, indicating that the adverse effect of formaldehyde was probably due to an effect on the rumen environment. Urea supplementation increased rumen ammonia-N concentrations, although this effect was not as great on the high formaldehyde silage, and increased the rate of D.M. and cellulose disappearance from silage in nylon bags.

It appears that the lower intake and the poorer utilization of dietary N on the high formaldehyde silage may have been due to a reduction in the rate of digestion within the rumen. While there was some response to urea supplementation, it could not restore the apparent rate of digestion in the rumen to levels observed on the control diet. Hence, factors other than the supply of rumen-degradable N in the diet must have been responsible for the depression of digestion within the rumen.

Results of visual and radiographic development of the mandibular caudal teeth were obtained from 135 cattle between 1 and 2 years old. Age ranges for each stage of tooth development were obtained. Using visual assessment of second molar intra-oral eruption the maximum age range before animals could be differentiated was 8 months (1 year 3 months from 1 year 11 months). Animals showed different stages of development in all six teeth using criteria based on resorption of the temporary premolar teeth and crown and root formation in the permanent premolar and molar teeth. The maximum age range before animals could be distinguished was 5 months (1 year 6 months from 1 year 11 months) and at all other ages the age difference before differentiation was less.

Dissection data from an experiment involving 12 buffalo, nine ♂Friesian × ♀Egyptian native Baladi (½ Friesian) and nine ♂ Friesian × ♀ ½ Friesian (¾ Friesian) bulls were used to examine the growth and partition of fat between depots and its distribution in different regions of the carcass.

Growth of total dissectible carcass fat (TCF) and its component depots (subcutaneous (SCF); intermuscular (IMF); kidney knob and channel (KKCF)) and total offal fat (TOF) and its component depots (caul (CF); mesenteric (MF); heart (HF)) relative to total body fat (TBF = TCF + TOF) was examined.

Relative to TBF, no significant differences in growth coefficients or adjusted means of TCF, TOF, carcass SCF and carcass KKCF were found between genotypes. Compared with ¾ Friesians, buffaloes had lower rates of deposition of CF and IMF, lower proportion of TBF deposited as MF and a greater proportion of HF.

As dissected side fat (DSF) increased, the proportion of fat decreased in the distal hind limb and neck, increased in the abdominal wall and adjacent ventral part of the thoracic cavity and remained unchanged in the other carcass regions. Fat growth coefficients differed between genotype groups in all carcass regions except the distal hind limb, fore limb and thorax. A posterior-anterior decrease in growth impetus of fat from the loin (b < 1) towards the neck (b > 1) was traced in buffaloes while the growth coefficients within all dorsal cuts in cattle did not differ significantly from 1. Compared with cattle, buffaloes had more of the DSF occurring in the combined expensive cuts with higher SCF: IMF ratio only at the upper limits of fatness considered in the present work.

It is argued that buffaloes relative to Friesian cross-breds have a beef-type fat partition and that characteristic changes in rates of increase in fat depots relative to empty-body weight and in fat in various regions relative to total fat could be related to the increase in Friesian blood.

Soya-bean plants were grown for 40 days in a range of root temperatures from 10 to 25°C either in a root medium containing N but uninoculated or in a N-free medium but inoculated with Rhizobium japonicum. Low root temperature restricted growth in both cases but the plants depending solely on symbiotic N-fixation were much more affected. At 10 CC root temperature plants failed to nodulate but both nodulation and nitrogen fixation increased greatly in the range 15–25°C. It is concluded that soya beans sown in cool soils would benefit from applied nitrogen at sowing time.

Simple series of trigonometric terms (Fourier series) give good representations of response curves including sigmoid curves and intersecting straight lines.

Two-thirds of the sugar-beet crop in the U.K. receives sodium chloride as part of the fertilizer programme. It is well known that the crop responds profitably on sandy soils which contain relatively little sodium and potassium, and most of these fields now receive sodium chloride. Few crops on clays, silts and organic soils are treated because the value of sodium chloride has never been clearly defined. Thus 36 field experiments were made over the 5 years 1975–9 on contrasting soil types testing five amounts of sodium chloride, 0, 100, 200, 400 and 800 kg/ha, and at two times, either autumn or spring. All the fields chosen were in continuous arable rotations where potassium chloride was applied regularly and nearly all the soils contained more than 120 mg exchangeable K/l.

Sodium chloride (400 kg/ha costing £12) increased sugar yield on average by about 0·2 t/ha (worth £40) on the mineral soils but no crop responded on organic soil. Exchangeable soil sodium concentration was not a good predictive test of which fields would respond but all the large increases in yield were on fields with less than 20 mg Na/1. A few crops responded on soils with 20–40 mg Na/1 but no crop responded on soil with more than 40 mg Na/1. A survey of sodium concentrations in 800 soils showed that most mineral soils contained less than 40 mg Na/1 so it is suggested that all mineral soils regardless of texture should receive 400 kg sodium chloride/ha. Crops on organic soils did not respond to sodium chloride because the soils already contained sufficient.

Autumn and spring applications of sodium chloride on mineral soils gave similar increases in yield provided the fertilizer was not applied just before sowing, when in 2 years it decreased plant establishment. This effect was particularly damaging on clays and silts where it is frequently difficult for other reasons to obtain good seed beds and full establishment. It is concluded that sodium-containing fertilizers should always be applied well ahead of sowing to allow rainfall and cultivations to incorporate them into the soil. On clays and silts it is suggested that they should be applied before ploughing to avoid soil compaction but on sands there may be advantages in post-ploughing application.

Four experiments were carried out to study the possibility of replacing milk proteins for lambs with Toprina yeast (G) grown on hydrocarbons. In Expt 1 the effect of replacing all the milk protein with Toprina was studied in the presence of milk fat or a mixture of lard and coconut fat. In Expt 2 the maximum level of Toprina yeast that could be used was studied. In Expt 3 the effect of treatment of the yeast with acid on the digestion of Toprina proteins in the small intestine of pre-ruminant lambs (fitted with re-entrant cannulae in the terminal ileum) was examined. In Expt 4 the effect of the supplementation of acid-treated yeasts with tryptophane and methionine was studied using growing rats.

The results of Expt 1 showed that lambs given milk diets grew faster (145 v. 80g/day) and converted feed more efficiently than those given Toprina yeast. Apparent digestibility of nitrogen of skim milk was higher (93%) than that of Toprina yeast (84%). The poorest results were obtained from lambs given lard and coconut as the source of fat and Toprina yeast as the source of protein. In Expt 2 it was found that progressively replacing the casein protein by yeast protein (0, 33, 67 and 100%) resulted in a linear reduction in daily live-weight gain, feed conversion and nutrient digestibility, but at 33% replacement of milk protein any effect on lamb performance appeared to be small. In Expt 3 the flow rates of dry matter, nitrogen and its fractions (soluble and insoluble in water) and fats were highest with the raw yeast, intermediate with acid-treated yeasts and lowest with skim milk. Apparent digestibility of nitrogen up to the ileal cannula was 67, 77 and 88% for raw yeast, acid-treated yeast and skim milk respectively.

In Expt 4, raw yeast supplemented with methionine was found to be as good a protein source as casein for growing rats. The supplementation of acid-treated yeasts with tryptophane did not improve rat performance, but supplementation with methionine increased growth rate and improved efficiency of feed and protein utilization. Acid hydrolysis of yeast also improved its nutritive value, but the full improvement was only obtained when the diet was supplemented with methionine.

It is concluded that yeast protein can provide only about one third of the protein in milk replacers for lambs; prehydrolysis of the yeast may help to increase this proportion without reduction in animal performance.

In field trials made for two years in the dry period of a semi-arid tract under natural precipitation at the Indian Agricultural Research Institute, New Delhi, overnight seed-soaking of wheat in 0·5% solution of 2-chloro-ethyl-trimethyl ammonium chloride (CCC) prior to sowing increased the grain yield. When treated with foliar application of the chemical in concentrations ranging between 40 and 1000 mg/1, wheat plots yielded better than did the untreated control, but no consistency was noted between the concentrations or stages of their application. The benefit from CCC was due to more root growth, increased stomatal resistance and higher leaf water potential. Treated plants extracted more water from deeper soil layers, increasing their water-use efficiency.

In the first of two experiments 45 ewes were treated on day 141 of gestation with either prostaglandin F2a or saline. Doses of 10, 15, 20 or 25 mg PGF2a failed to induce lambing earlier than in control animals. A further 50 ewes were similarly treated on day 144; neither dose level of PGF2a nor day of administration had any effect on the interval from injection to lambing compared with controls. In a second experiment 159 ewes were randomly assigned to one of four treatment groups as follows: (1) 20 mg oestradiol benzoate (ODB); (2) 16 mg dexamethasone; (3) 15 mg PGF2a; (4) 2 ml saline. Ewes were injected on either day 143 or 144 of gestation and on each of those days animals were injected either in the morning or evening. The mean times to induction of lambing were 38·6 ± 20·8; 44·2 ± 18·1; 83·5 ± 39·8 and 82·9 ± 43·1 h for the four treatments respectively. Neither day nor time of treatment had any significant effect on the interval to lambing. Both ODB and dexamethasone induced parturition earlier than PGF2a or saline (P < 005).

Three experiments were carried out to investigate factors which might affect the voluntary intake of effluents.

Effluent was introduced into the diet of pigs at rates of 25, 50 and 100 g D.M./day, replacing dry meal to maintain a constant amount of dry matter offered. The mean maximum daily intakes of effluent on the three treatments were similar indicating that, within this range, the rate of introduction of effluent had no effect on its potential maximum intake.

When solutions with differing concentrations of effluent dry matter were offered it was found that the intakes at the 20 and 10 g/kg concentrations were progressively lower than when tho concentration was 30 g/kg or higher. This suggested a physical limitation to the intake of effluent at low concentrations. A physiological limit may operate at concentrations of 30 g D.M./kg or higher.

In the third experiment daily air-dry meal allowances of 80, 90, 100 and 110 g/kg W0.75 were offered in addition to an ad libitum supply of effluent. The voluntary intake of effluent dry matter was not significantly affected by tho amount of meal offered and the total amount of dry matter consumed remained virtually constant.

A method is proposed for correcting for competition effects in yield trials by joint regression of plot yields on to the yields of neighbours. Estimation of the variety effects and competition coefficient along with tests of significance are described for a sugar-beet trial with single-row plots where competition effects are assumed to extend only to plants in immediately adjacent rows. For designs which are balanced for neighbouring varieties it is feasible to estimate separate varietal competition coefficients which may be partitioned into components for sensitivity and aggressiveness. An example is given of this extended model fitted to a competition diallel of seven species. While species differed in their sensitivity to competition there was no essential difference between inter- and intra-species behaviour. The model is used to assess comparative varietal performance in monocultures from performance in small plot trials.

(Note that the general term ‘variety’ is used throughout this paper to refer to progenies at any stage in a selection programme.)

A mathematical plant competition model developed by Currah (1975), and subsequently modified by the author, is briefly described. The model has two useful properties: (a) it can cope with complex irregular row spacing systems such as occur in commercial practice and (b) it can be ‘calibrated’ to the yield values at any site by using data from previous crops.

Parameter values of the modified model are calculated for both carrot and red beet crops. At least 70% of the variation in these data could be accounted for by fitting the model, a performance which was similar to, but never as good as, fitting analysis of ariance models. There were no systematic deviations between the fitted and observed values.

Previously estimated parameter values were used to predict mean root weights of carrot and red beet storage roots. Overall agreement between predicted and observed data was good, although some systematic deviations occurred.

The practical value of the modified version of the model and its strengths and weaknesses are discussed.

The net energy values for growth and fattening of two artificially dried tropical grasses-, pangola (Digitaria decumbens) and setaria (S. sphacelata var. sericea cv. Nandi), of similar estimated metabolizable energy content (8·07 and 7·96 MJ/kg D.M.) were determined with cattle using a slaughter technique. Growing cattle with a mean initial weight of 175 kg were given equal quantities of dry matter of the two grasses at each of three planes of nutrition above maintenance for a period of 152 days.

The initial energy, fat and protein content of the total body of the 24 test animals was estimated from regressions relating fasted live weight to theśe components, derived from 12 similar cattle slaughtered at the beginning of the feeding period. The final energy, fat and protein content of the test animals was determined directly by chemical analysis. The metabolizable energy (ME) content of the grasses was estimated from the level of digestible energy (DE) determined with eight cattle, assuming that ME = 0·815 DE.

The cattle fed pangola gained more live weight, empty-body weight, fat, protein and energy than animals fed similar quantities of setaria. The net energy value for growth and fattening (NEf) was determined using regressions relating energy retention to the quantity of dry matter eaten. NEf in MJ/kg dry matter was 2·27 for pangola and 1·31 for setaria.

Efficiency of utilization of ME for growth and fattening (kf) was.27·7% for pangola and 16·9% for setaria. These values for tropical grasses are lower than any values reported for temperate pasture species. Thus the lower efficiency of utilization of ME may cause the lower production of cattle which graze tropical grasses.

It was concluded that as the kf values of different tropical grasses are not constant, kf values should be measured on a wider range of tropical grasses so that this factor can be taken into account when evaluating grasses in animal production systems.

Two groups of weaned sheep weighing about 30 kg, one born in March and the other in September, were each divided into two and given ad libitum one of two pelleted diets, ruminant diet A or ruminant diet AA6. The March-born sheep commenced experiment in July and those born in September in January. The experiment continued for 4½ years. At intervals sheep were killed and the fat protein and ash contents of their digesta-free bodies determined.

The voluntary intake of feed showed a seasonal periodicity with minima in the winter and maxima in summer. The amplitude was 30% in the 1st year and in subsequent years averaged 13%. Those given the higher quality diet (AA6) consumed slightly less than those given the poorer one.

Mean daily feed intake averaged over 6-month periods from January to July and July to January was invariant with age during 4 years of observation. In this time the sheep increased in weight from about 30 kg to about 130 kg. There were, however, considerable differences between individual sheep in the amount of feed they habitually consumed.

The body weight of the sheep increased and eventually plateaued. The asymptotic weight defined as A in the equation W = A–Be–kt, where W is weight at time t and B and k are constants, was related to the mean daily feed intake averaged over 6 months; mean daily feed intake measured over 6 months was proportional to a fractional power of body weight indistinguishable from 0·75, the interspecies power to which metabolism is proportional. Growth of wool during successive 6-month periods did not vary with age of animal but differed significantly between animals.

Fasting metabolism of the sheep was 316 kJ/kg W0·75 for wethers and 336 kJ for rams.

Analysis of the bodily composition data showed that over a range of digesta-free body weight from 46 to 130 kg it was not possible, on statistical grounds, to distinguish between linear relationships between body weight and its fat, protein, ash and water content, and allometric ones. The linear relationships had marginally smaller residual standard deviations and the regression coefficients show that the gain of the empty body in these sheep consisted of 68% lipid, 8% protein, 1% ash and 24% water. The lipid in the carcass accounted for 88% of the total lipid gain and half the accretion of protein and ash was in the carcass. These results confirm those of Searle, Graham & O'Callaghan (1972) based on tritium dilution which showed that post-puberal growth in sheep is of constant composition.

The results of the metabolic studies are shown to be consistent with the growth studies.

Growth to maturity, as affected by different hypotheses related to the determinants of maintenance energy expenditure and the regulation of appetite, was examined algebraically. It is shown that mature weight is the rate of feed intake divided by the rate of maintenance metabolism per unit weight, and for defined feeding systems the rate constant for the approach to mature weight is the rate of maintenance metabolism divided by the feed equivalent of unit gain.

The implications of the results in terms of the measurement and prediction of feed intake and the use of metabolic body size as a scaling factor in comparative and genetic studies of growth are briefly discussed.

In an experiment on permanent grass at Rothamsted during 1975–9 fertilizer-N was applied each year either by injecting an aqueous solution of urea (supplying 250, 375 or 500 kg N/ha) in spring, or by broadcasting ‘Nitro-Chalk’ granules (supplying 100, 200, 300, 400 or 500 kg N/ha) in six equal dressings for each of six cuts.

Dry-matter production was largest on plots injected with urea through knives 30 cm apart, and more N was recovered from the injected than from the broadcast applications. Aqueous urea injected at the 60 cm knife spacing nitrified more slowly and persisted in the soil longer than urea injected at 30 cm spacing; this persistence caused grass to grow more uniformly throughout the season, but yields were less. Injecting the nitrification inhibitor sodium trithiocarbonate (STC) with the aqueous urea postponed N uptake much less than doubling knife spacing, but the inhibitor substantially diminished percentage N03-N in harvested grass.

In spring 1977 individual plots were split to measure N residues. Half-plots thus received N at the specified rates, either in 4 successive years (1975–8) or in two pairs of successive years (1975 and 1976; 1978 and 1979). In 1977 urea injected in the 2 previous years gave large residual effects, which were increased by STC and also by injecting in bands 60 instead of 30 cm apart. Broadcast ‘Nitro-Chalk’ had much smaller residual effects. In 1979 residual effects of N applied in the 4 previous years were apparently small, regardless of the method of application, because clover became abundant on plots not given N.

In 1978 dry-matter production was smaller where N had been given each year during 1975–8 than where N was withheld in 1977. Analysis showed this was caused by a shortage of potassium. This effect was most pronounced where 375 or 500 kg N/ha had been injected in bands 60 cm apart.

The results showed that a single, injected application of aqueous urea increased yields of dry grass as effectively as equivalent repeated dressings of ‘Nitro-Chalk’.

The comparative rate of development of Orosius albicinctus Distant was studied on different host plants, sesame, sannhemp, radish, purslane, lucerne, chicory, Indian rape, sugar beet and black gram. The duration of the egg stage was the shortest (7·1 days) on sesame and was prolonged to 12·0 days on chicory. The nymphal duration was again minimal (11·9 days) on sesame and was prolonged to 15·4 days on chicory. The nymphal survival was also more on sesame than on the other hosts. Thus, among all the host plants tested sesame was found to be the best suited host for this leaf-hopper.

Nine normal lactating Murrah buffaloes from the Punjab Agricultural University Dairy herd were used to assess the effect of showers and evaporative cooling on plasma oxytocin concentration, let-down time, milking time and milk yield in buffaloes. The animals were showered four times daily between 10.30 and 16.30 h or provided with evaporative cooling from 07.00 to 21.00 h. In the hot and dry period the oxytocin concentration in buffaloes given a shower was significantly greater than that of the buffaloes of the control group. In the hot and humid period there was a similar trend.

It is concluded from these studies, that cooling may increase the effective milk ejection reflex because the milk-ejection response to a given blood oxytocin concentration is different when the animal is heat stressed from when it is cooled.

Proximal colons taken from lambs up to 3 weeks after birth were shown to transport both sodium and chloride from lumen to blood when incubated in vitro.

Sodium transport fell into three phases during postnatal development. The first covered the period from birth to 3 days of age when sodium transport was high and equal to that calculated from measurement of short-circuit current. The second was seen in 5- and 7-day-old lambs where the short-circuit current was low and the net transport of sodium was negligible. The third was seen in 2-3-week-old lambs where sodium transport was high, but the short-circuit current was low.

Chloride absorption by colons taken from 1-day-old lambs appeared to be in exchange for an anion, possibly bicarbonate. Chloride absorption by colons taken from 3-week-old lambs appeared to be electrogenie or coupled directly to the transport of sodium.

A possible explanation for the failure of electrolyte absorption by colons taken from 5- and 7-day-old lambs is discussed.

S1 maize varieties and varietal hybrids were tested in six locations ranging in altitude from 236 to 1600 m in Cameroon. The grain yields of highland varieties were observed to increase with each increase in altitude while the yields of the lowland varieties decreased with increasing altitude.

The highland × lowland S1 varietal crosses yielded the same as the lowland parental varieties in highland areas and better than highland parental varieties in lowland areas.

Average yields of all varieties per location increased by about 1·1 t/km increase in altitude. Eberhart & Russell's (1966) stability method found no stable variety while Francis & Kannenberg's (1978) genotype-grouping technique found five highland × lowland crosses to be relatively stable.

Number of days from planting to tasselling increased with increasing altitude by about 20 days/km increase in altitude. Highland and lowland varieties performed poorly outside their zones of adaptation because of high incidence of foliar diseases like leaf blights and rusts.