Experiments made with winter fodder crops, lucerne (Medicago sativa), berseem (Trifolium alexandrinum) and oats (Avena sativa) and summer fodder crops, cow pea (Vigna unguiculata), guar (Cyamopsis tetragonoloba), sunhemp (Crotolaria juncea) and pearl millet (Pennisetum americanum) showed that a sequential crop of Sudan grass yielded more after the legumes than after the cereal fodders, oats or pearl millet. The legume advantage was noted in the crop not given fertilizers but also when Sudan grass was given N fertilizer. The yield increase in Sudan grass grown after legumes was equivalent to 32–60 kg fertilizer N/ha applied to Sudan grass following pearl millet.

After harvesting the legumes more available N and NO3-N was present in the soil and the apparent recovery of fertilizer N by a subsequent crop was increased by the legume.

In a study of the effect of animal species on the threshold particle size leaving the rumen, two grasses cut at two stages of growth and one mature legume were separated into leaf and stem fractions and fed to cattle and sheep. Samples of rumen digesta and faeces were used to determine the validity of using a 1·18 mm porosity screen to separate the rumen particles into large and small pools when studying escape of particles from the rumen. Samples of rumen digesta and faeces were collected for the determination of particle size by wet sieving and the calculation of resistance of particles to passage from the rumen relative to small particles retained on a 0·15 mm sieve.

Particles < 1·18 mm but > 0·5 mm had a mean relative resistance to passage of 2·0 and 2·6 for cattle and sheep respectively, compared with resistance values of between 10·9 and 31·2 for particles between 1·18 and 2·36 mm. It is suggested that there is no justification for using different threshold particle sizes for sheep and cattle and that a 1·18 mm sieve may be used to divide the rumen contents of both cattle and sheep into two pools of particles with high and low relative resistance to passage from the rumen.

Two experiments were designed to measure the effect of current barley storage systems on vitamin E stability.

Whereas propionic acid and sodium hydroxide treatment of moist barley results in destruction of vitamin E, neither moisture per se nor anaerobic storage has such a detrimental effect. The destruction is most severe and rapid with alkali treatment, the reaction having substantially reached completion by 5 days. All the vitamin E isomers were affected to varying degrees, the order of susceptibility to decay being α-tocopherol > γ-tocopherol > α-tocotrienol > γ-tocotrienol.

Possible explanations are given as to why the findings incriminating propionic acid in vitamin E destruction are at variance with currently held opinion.

Data are presented for the amino acid contents of 64 litters of Suffolk × (Finnish Landrace × Dorset Horn) foetuses varying in gestational age from 90 to 145 days and in litter size from one to five. The concentrations of glycine, cystine, arginine, proline and hydroxyproline in foetal dry matter increased with age, those for threonine, serine, glutamic acid, valine and methionine remained fairly constant while those for aspartic acid, phenylalanine, histidine and lysine tended to decrease. The most pronounced of these age effects were for cystine and hydroxyproline which increased in concentrations by 60 and 100% respectively over the final 2 months of foetal life. The rates of accretion of the individual amino acids are discussed in relation to estimates of the amounts that may be supplied by microbial protein.

The objective of this work was to investigate the effects of changing proportions of readily fermentable carbohydrate and fibre in the diet on the rates of lipolysis and fatty acid hydrogenation by sheep rumen digesta. Three experiments were carried out using rumen-fistulated Romney wethers. In the first experiment rumen digesta from one sheep on a high-fibre diet was incubated in vitro with [1–14C]linoleic acid and 0, 0·1, 0·2 and 0·5% sucrose. It was found that sucrose increased the rate of hydrogenation of linoleic acid by up to 40%.

In the second experiment five rumen-fistulated Romney wethers were fed five diets according to a latin-square experimental design. These diets had decreasing proportions of fibre (42·8–19·5%) and increasing proportions of starch (12·2–35·7%). Lipolysis and hydrogenation rates decreased significantly with decreasing fibre content which was reflected in the amounts of stearic and octadecenoic acids in the rumen digesta.

In the third experiment sheep were fed the high-fibre diet used in the first experiment and the rumen digesta incubated in the presence of 0, 0·15, 0·45, 0·75 and 1·50% starch. Lipolysis rates increased but no effect of added starch on hydrogenation was observed.

It was concluded that the short-term addition of energy to the rumen digesta increases lipolysis and hydrogenation rates. However, long-term replacement of fibre by starch results in a reduction of these rates.

Sorghum bicolor, Pennisetum americanum, Echinochloa utilis, Panicum miliaceum, Setaria italica and Eleusine coracana were grown with and without full irrigation on an alkaline clay soil at Trangie, Australia. Dry-matter yields and forage quality changes with time were measured in the 1st year. Grain yield was recorded over 2 years.

Dry-matter accumulation was initially most rapid in sorghum and Japanese barnyard millet. Sorghum, pearl millet and finger millet produced the most dry matter; these were the latest to reach head emergence. The early-maturing proso millet and foxtail millet produced only 7 and l i t dry matter/ha respectively. These two millets, like sorghum and pearl millet, had a high nitrogen: sulphur ratio and low sodium concentration in the forage. Finger millet had a lower nitrogen: sulphur ratio and a sodium concentration that was surpassed only by Japanese barnyard millet.

Irrigated sorghum consistently produced the highest grain yields: over 9 t/ha. Yields from the millets were: foxtail 6·0, finger 5·0, proso 3·5, pearl and Japanese barnyard millet 2·8–2·9 t/ha. Special features of the millets are discussed.

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.

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.

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.

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.

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.

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.

Eight canopy heights, maintained by weekly cutting, were compared during summer and early autumn on a perennial ryegrass (Lolium perenne L.)-white clover (Trifolium repens L.) sward.

Perennial ryegrass adapted to a taller canopy by increasing the length of its leaf blades much more than it increased the length of its leaf sheaths, and by increasing the length of its blades proportionately more than their width. White clover adapted by increasing the length of its petioles much more than it increased the length of its leaflets. Canopy height did not affect the number of ryegrass leaves emerging or dying per tiller or the number of live, emerged leaves maintained by a tiller. The amount of herbage harvested at the weekly cuts was largely unaffected by canopy height once the swards had adapted to the particular management. Leaf blades in the taller canopies, therefore, lost a much lower proportion of their length to defoliation than those in the shorter canopies. Consequently, the length of blade dying per tiller per week was more strikingly affected by canopy height than was the rate of leaf extension. The increasing amount of material lost by death with increasing canopy height was confirmed by the weights of senescent and dead tissue collected weekly from a fixed area in each plot. Herbage in the lower compared with the upper layers of the taller canopies was much less digestible and lower in N content.

More than 200 wild type isolates of chickpea (C. arietinum) rhizobia were screened for their drug resistance. Only 15 were found to be resistant to one or more antibiotics at a concentration of 5 μg/ml (units/ml). When tested for multiple drug resistance, some were found to be resistant to more than one antibiotic. In competition studies, rhizobia resistant to streptomycin were found to be more competitive than antibioticsensitive strains, while those resistant to penicillin could not compete even with antibiotic-sensitive strains.

A field trial was made for 3 years at the Indian Agricultural Research Institute, New Delhi under semi-arid rainfed conditions to study the effect of the preceding season cultural practices on mustard and to assess the possibility of double cropping, and the results are discussed. Preceding season cultural practices, i. e. ploughing in fallow or growing cow pea for fodder or mung for grain (both short-duration crops) increased the yield of the mustard crop compared with no tillage or growing pearl millet in preceding season. Yield of mustard following tillage, fodder cow pea or mung with mulch was similar; hence it is concluded that double cropping is possible under such conditions instead of conventional tillage-mustard, monoeropping practice. It is also concluded that frequent ploughings could be greatly reduced to give few but more effective cultivations, but more research into reducing cultivation during the preceding season should be carried out.

From 1980 to 1983 factorial experiments at Saxmundham were made on winter wheat following beans, so as to minimize losses from foot and root rots and increase potential yields. All tested seed-bed N, and amounts and times of application of N in spring, both with and without sprays intended to limit losses from aphids and from diseases. The tests were made on one semi-dwarf variety in 1980 and on two contrasting varieties from 1981 to 1983. In 1982 and 1983 a comparison was made between wheat following beans and wheat following wheat; all treatments were applied cumulatively to the two successive wheat crops.

In 1980 and in 1981 N given in March greatly increased the number of shoots in April but had little effect on the final number of ears. Yields of grain were greatly increased by N given during April and by sequential sprays with fungicides and aphicide; these two factors interacted so that responses to N were larger with the sprays than without. Yield responses to seed-bed N, although small, were greater than the benefits from applying divided instead of single N dressings in spring. The number of ears was greatly increased by increasing the amount of N given in April, but only slightly by any of the other treatments. The weight of 1000 grains was greatly increased by the sprays of aphicide and fungicides and was decreased by N in 1981, but not in 1980. Largest yields of grain were 10·14 t/ha in 1980 and 10·91 t/ha in 1981 when N was given in spring at 160 and 200 kg/ha respectively, and the crops were sprayed with pesticides.

In 1982 and 1983 N applied in March again greatly increased the number of shoots in April, but not the final number of ears. Yields of grain were larger after beans than after wheat, mainly because the number of ears and the weight of 1000 grains were greater. This may have been because take-all (Gaeumannomyces graminisvar. tritici) was more severe where wheat followed wheat. Previous cropping also interacted with variety; Avalon yielded slightly less than Norman where take-all was slight but much less where take-all was severe. Where N was given the mean loss in yield from growing Avalon rather than Norman in the 2 years was 2·47 t/ha after wheat and 0·37 t/ha after beans. The take-all disease ratings of Norman and Avalon after wheat were 132 and 197 respectively. Yields of grain were greatly increased by N given during April, especially of wheat following wheat and where it was protected with sprays; then the mean yield was only 2·79 t/ha without N but 8·78 with 235 kg N/ha. Where wheat followed beans, yields were 6·89 t/ha without N and 11·07 with 175 kg N/ha. Applying N to the seed bed increased yields slightly, and again by more than by dividing the dressing of N in spring. The number of ears was greatly increased by N in spring and a little by all the other factors that increased grain yield. The weight of 1000 grains was increased greatly by the sprays of aphicide and fungicides, was decreased by N, and was larger for Norman than for Avalon.

In 1980–1, after beans, the mean amounts of N removed by the grain (where aphicide and fungicides were given) ranged from 81 kg/ha without N fertilizer to 167 where most N was given. In 1982–3 comparable values ranged from 86 kg N/ha to 191 where wheat followed beans and from 35 kg N/ha to 168 where wheat followed wheat.

Forty-five triple test cross progenies produced by crossing 15 homozygous strains of wheat with three testers (varieties HD 2160 and NP 846 and their F1) and 17 parents, were raised in a randomized-block design in two environments (normal and stress). The data on five randomly chosen plants from parents and F8 and ten plants from F1 x lines were recorded for number of days from sowing to heading, plant height, the number of tillers per plant, total biomass, the number of grains per ear, 1000·grain weight and grain yield per plant. The additive and dominance components of genetic variation were each estimated by three methods to determine their relative usefulness in estimating these components. The variance of parents gave better estimates of the additive component than the two other methods (1i + 2i and 1i + 2i + 3i). The method 1i + 2i + 3i proved its superiority over the 1i + 2i method. The dominance component was better estimated by the method 1i - 2i than by the 4σ2d + 9σ2 (1i + 2i - i) and 25 (σ2 (21i - i) pooled with σ2 (22i - i)) methods. The two methods 4σ2d + 9σ2 (1i + 2i - i) and 25 (2σ2 (21i - i) pooled with σ2 (22i - i)) provided similar results for the estimation of dominance component.

To evaluate the accuracy of various techniques for determining the sexual state of sows, four multiparous Landrace sows were housed in stalls 2–5 weeks after weaning. Catheters were inserted under anaesthetic into a prominent ear vein on each sow. Four days later blood and urine sampling commenced, along with other measurements to assess the oestrous state of the animals.

Oestrus was detected in all four sows and so were corresponding oestradiol·17β peaks (22–49 pg/ml) in serum of the three sows from which blood was successfully sampled during the complete 25·day collection period. Serum progesterone concentrations were highest between days — 5 and — 12 (day 0 = 1st day of standing heat) (peak values of 33·1–58·2 ng/ml), with values of 3·55 ng/ml or less on day 0. Urinary oestrogen was less well correlated with oestrous state than were serum hormone concentrations, but progesterone derivatives in urine corresponded well to serum progesterone with peaks between days —5 and —9. Vulval redness, vulval size, social interest and the occurrence of flehmen were markedly greater during the oestrous period than at other times in the cycle. Body temperature, vaginal pH, the presence of vaginal mucus and behavioural manifestations of oestrus (with the exception of back pressure test) were less well correlated with sexual state. A combination of vulval colour and size, back pressure test, a more detailed study of behaviour and possibly with urinary progesterone derivatives, should give the best indication of the incidence of oestrus in sows.

Results of a 2-year studyin the rainforest and savannah zones of Nigeria todetermine the responses of yield, components of yield and nutrient content of maize to soilapplied zinc showed that Zn significantly increased yield in the new and old savannah soils, whereas significant yield response was recorded only in an old field of the forest zone. Ear weight was the only yield component significantly influenced by Zn treatments in the two zones. Application of 2·5 kg Zn/ha appears adequate for successful maize production in the savannah and old forest zones in the tropics.

Soil-applied Zn significantly increased ear-leaf N and Zn, but P concentration was significantly decreased. Grain yield was positively correlated with ear-leaf Zn.