A stepwise adaptation was carried out on eight sheep through diets containing 10, 24, 44, 60 to a final diet containing 71% maize meal and molasses. The numbers of protozoa in the rumen increased in proportion to amount of readily fermentable carbohydrate fed, up to and including the 60% grain and molasses diet, while the numbers of total culturable bacteria remained essentially constant. However, the proportions of amylolytic and lactate-utilizing bacteria increased, and there was an orderly shift from acid-sensitive to more acid-tolerant species, particularly amongst the lactate-utilizers in response to the gradual decrease in the ruminal pH. Up to this stage the protozoa probably controlled the rate of fermentation by engulfing starch grains and bacteria and were thus able to maintain the pH of the rumen above 5·5. Lactic acid appeared only transiently and the peak values tended to diminish as adptation progressed.

The first day the final diet was fed the ruminal pH decreased to 5·4 or below for several hours. Within 7 days the number of protozoa had decreased by 50–80% and the number of total culturable bacteria increased sharply. Conditions in the rumen became unstable: peak values of D- and L- laotic acid increased by ca. 0·5 HIM, the acetate/propionate ratio decreased to ca. 2 and peak glucose concentration increased t o 3·2–9·5 mM. One animal refused all food for 1 day. Acid-tolerant species of lactate-utilizing bacteria multiplied rapidly in response to the increased production of ruminal lactic acid and the ratio of amylolytics to lactate-utilizers decreased from a mean of 10·7 to 3·6. This controlled the increase in lactic acid and the decrease in ruminal pH, allowing the ciliate protozoa to proliferate and regain control of the fermentation.

The types of cellulolytic bacteria did not change during the experiment. Despite their acid sensitivity, the number of cellulolytic bacteria per gram of ingesta was of the same order after 54 days on the 71% grain and molasses diet (0·5–13·3 × 107) as on the initial high roughage diet (3·2–7·6 × 107).

Three sheep which bloated showed no marked chemical or microbiological differences from the non-bloating animals.

Sixty-four weaned Awassi ewe lambs were used in the present study to estimate age at puberty and to investigate whether early breeding from such ewe lambs is possible. After weaning at 4 months old ewe lambs were divided at random into two experimental groups. One group, designated as moderate, was fed to attain 40 kg live weight at 12 months of age, while the other (high) was planned to reach 50 kg at the same age. Fertile rams were run with the ewe lambs at 6 months of age. Twenty ewe lambs, 10 from each treatment, were slaughtered and their ovaries were examined for the presence of corpora lutea and largest follicles.

The overall age at first oestrus was found to be 293 days. Ewe lambs of the high nutritional treatment reached puberty earlier than those of the moderate one (274 v. 312 days). Likewise, single-born lambs reached puberty earlier than twin-born ones (273 v. 312 days). Treatment differences explained 16·5% while type of birth explained 16·3% of the total variance in age at first oestrus. Ewe lambs of the high nutritional treatment experienced more heats than those of the moderate one. Simple correlation coefficients between age at first oestrus and date of birth, daily gain and live weight at puberty were 0·21, 0·09 and 0·75, respectively. Results indicated that ovulation may not occur during the first and second oestrus. From 44 ewe lambs only 12, 10 from the moderate and 2 from the high treatment, lambed 13 viable lambs. Reasons for such a low conception rate (27·3%) are discussed.

The effects of lodging on the seed yield of S. 23 and S. 24 perennial ryegrass were investigated in a series of field experiments from 1973 to 1976. Natural lodging severely reduced seed yield in all years as a result of a decrease in the number of seeds per unit area. Controlled lodging at different stages of crop growth produced more variable results, indicating that lodging may affect both pollination and seed development. Disturbance of the crop during anthesis in order to aid pollination did not improve seed yields, possibly as a result of damage incurred.

In these experiments lodging not only decreased the number of seeds harvested, but also had an effect in determining which spikelets on the ear set most seed. These data have also shown that many more seeds are set than are harvested, even when the crop is not lodged. It is suggested that there is a lack of assimilate supply to fill the developing seeds, some of which abort, allowing the remainder to attain a viable seed weight. Mechanical support of the crop may increase the assimilate supply to the seed thus allowing seed further up the ear and spikelet to develop fully.

The paper reports on a study, conducted in four successive seasons, of sexual development and breeding activity in females of the Iceland breed, the only breed of sheep kept in the country. The ewe lambs normally attained puberty in their first year of life, on average at 7 months of age, with marked individual variation in both age and body weight at first oestrus. Ewe lambs always showed oestrus on average slightly later than mature ewes (2–9 years), the mean date of onset of the breeding season of the latter being 8 December, however, with considerable individual variation. Furthermore, ewe lambs had a shorter breeding season (1–4 months) than ewes (4–6 months) and they appeared to experience more silent heats resulting in less regular cyclic activity. There seemed to be a minor increase in the duration of the oestrous cycle with age and ewe lambs clearly exhibited shorter oestrus (heat) than ewes. With seasonal breeding activity ranging from November to May the mid-breeding season occurs some 4–7 weeks after the shortest day.

In experiments over 3 years (1974–6) cow slurry in the range 0–112·5 t/ha and ammonium nitrate in the range 0–120 kg N/ha were applied to field plots factorially to test the effects on the yield and quality of spring barley grain.

In 1974 slurry application markedly improved the grain yield (cv. Golden Promise) at each rate of inorganic N and increased grain size. Applying N fertilizer with more than 37·5 t slurry/ha reduced grain yield below the maximum. Grain with the highest crude protein content (15·1 %) was obtained from a combination of slurry and inorganic N. The residual effects of the slurry treatments gave satisfactory grain yields in 1975 without additional fertilizer.

Grain yields (cvs Julia and Abacus) in other experiments carried out on a different soil type in 1975 and 1976 were approximately half those obtained in 1974, due in part to drought conditions. The pattern of the results was similar. Heaviest grain yields were harvested from plots receiving 70 t slurry/ha with no additional N.

Exotic accessions of Phaseolus vulgaris selected for seedling cold tolerance by Austin & Maclean (1972) in a test in controlled environments were grown in a field experiment at Wellesbourne in 1974. Yields of up to 4·;7 t/ha at a plant density of 34 plants/m2 were obtained. In 1975, six selected accessions were grown at 21 plants/m2 at six different sites. Mean site yields ranged from 1·0 to 3·1 t/ha. The six accessions all had better emergence and higher yields than two commercial cultivars used as controls. The genotype × site interactions for yield (and for yield components) were small. The variation in yield between accessions (from 2·0 to 2·5 t/ha) was smaller than the variation in yield between sites. Variation in yield components tended to be additive between sites, and compensatory between accessions. There was a negative correlation between crude protein content and yield across accessions; the correlation between protein content and yield across sites was not significant. Accessions differed significantly in the amount of green leaf still attached to plants at harvest. This variation was not related to maturity as judged by moisture content of the seed. There was a negative correlation across accessions between the weight of leaf per plant at harvest and harvest index (the ratio of seed weight to stem weight).

Eight experiments, comprising four randomized-block feeding trials each with 20–45 animals and four changeover-design nitrogen (N) balance trials each with 6–10 animals, were used to study the effect of the addition of formaldehyde to fishmeal and to casein, of severe heating of fishmeal, and of tannin treatment of a mixture of vegetable protein-rich foods on the utilization of N for growth. Added in moderate amounts to rations demonstrated within the experiments to be deficient in N, quantities, but not the preparations, of N in the diet were critical to growth save at very low N intakes when the untreated foodstuffs were used more efficiently. Additional energy given in isonitrogenous rations increased growth, reducing N losses in the urine.

Plant and nodule development and nitrogen fixation were studied in two climbing cultivars of Phaseolus vulgaris, grown in monoculture, or associated with two maize populations differing in growth characteristics.

Bean cultivar P590 showed similar plant and pod fresh weight development in monoculture and when associated with a vigorous landrace maize, interspecific competition becoming significant only 92 days after planting. Nitrogen (C2H2) fixation in this cultivar was greatest 68 days after planting and declined rapidly thereafter, showing no significant differences between monoculture and associated plantings. When the bean cultivar P526 was associated with the landrace maize, plant development was depressed as early as 50 days after planting. While slight inhibition of nitrogen fixation, specific nodule activity (SNA) and nodule carbohydrate content was also observed at this time, it could not be concluded that such inhibition was definitely due to the associated planting.

Association with an improved maize, amarillo subtropical, did not affect plant development in P590 but did decrease growth of P526 at the 80 and 92 day harvests.

Each of the three uppermost leaves of wheat canopies studied in 1975 and 1976 showed a downward movement after its emergence. The variations with time of leaf angle were greatest in the flag leaf. Genotypes differed markedly in the rate of change with age in flag-leaf angle. Leaf curvature did not vary with age. There were differences between years in the rate of leaf movement, but cultivars ranked roughly the same in terms of leaf angle in each year. Grain yield per hectare was not related to leaf angle change. Most of the higher-yielding genotypes included in the study had straight leaves, the correlation between curvature and yield being —0·30 in 1975 and —0·60 in 1976.

Field investigations were undertaken during the winters of 1971–6 to study the grain yield responses of lentil cultivars to seed inoculation with single and mixtures of Rhizobium strains. An effective symbiosis and consequent increase in the grain yield was associated with the efficacy of the strain. Inoculation with a superior strain produced 23–32 % more grain than no inoculation on loamy-sand soil and 46–90% more on sandy-loam soil.

In separate studies comprising inoculation and nitrogen treatments, the seed treated with an effective Rhizobium strain gave on average 43% more yield than no inoculation and the application of 25 kg N/ha alone gave the same yield as inoculation. Rhizobium inoculation plus 20 kg N/ha was the best combination for maximum yield under both loamy-sand and sandy-loam soils.

Wool samples were collected from 39 rams representing five breed groups of sheep: Merino (M), Ossimi (0), and the crosses between them, viz. ¾ Ossimi–¾ Merino (¾ O), ½ Ossimi–½ Merino (½ O) and ½ Ossimi–¾ Merino (¼ O) maintained at Sakha Experiment Station, Kafrelsheikh, Egypt, with the objectives of detecting the effect of the seasonal changes in normal light rhythm and temperature on wool fibre length and diameter. Animals were divided into two light treatments groups, the first consisting of four animals from each breed kept under continuous dim light conditions throughout the year and the second of three animals from Ossimi and four from each breed group kept inside an open pen free to sunlight and shade zones under daylight rhythm throughout the year. It was found that fibre length as well as fibre diameter in normal light exceeded that in dim light except in winter time. Breed groups showed different responses to the absence of light especially the Ossimi and the ¾ O whose fibre lengths were most affected. The breed groups had larger fibre diameters in normal light than in dim light except Merino and ¼ O. Seasonal changes in temperature had a highly significant effect on fibre length but not on fibre diameter. Higher temperature coincided with lower increases in fibre length. Season to season variation in wool growth seemed to suggest that the number of light hours per day and atmospheric temperature counteracted each other resulting in a non-significant seasonal pattern.

Total sprout length and the length of the longest sprout were shown to be the most universally useful measurements to estimate sprout development in batches of potato tubers. A good estimate of sprout weight was also derived from measurements of total sprout length. There was a good linear relationship between total sprout length and initial tuber weight but the relationship varied considerably with the time of measurement and the temperature of storage.

It is suggested that if sprout measurements are to be used to predict the field performance of a batch of tubers the changing pattern of sprout vigour with time needs to be more closely understood.

An experiment to study the effect of sowing time (21 October, 5 November, 20 November, 5 December and 20 December), seed rate (5, 7·5 and 10 kg/ha) and application of nitrogen fertilizer (0, 20, 40 and 60 kg N/ha) was conducted at the Punjab Agricultural University, Ludhiana, on a loamy sand soil during the winter seasons of 1974–5 and 1975–6. The delay in sowing from 21 October to 20 December produced shorter plants with fewer spikes. The crop sown on 21 October using 7·5 or 10 kg seed/ha and supplied with 20 or 40 kg N/ha gave better yield than those of later sowings.

Hay was fed to an in vitro continuous culture of the rumen microbial population and to sheep kept in metabolism cages, and the effects of potassium chlorate addition on the rumen fermentation were studied. The compound was given for 8 days in vitro and for either 3 or 8 days in vivo.

Potassium chlorate addition in vitro (13·7 mg/g hay D.M.) depressed the production of CH4 and acetate, had little effect on propionate production and caused a small increase in the production of n-butyrate and n-valerate. The treatment also depressed cellulose digestion and the concentration of DNA in fermentor liquor, but increased the CO2:CH4 ratio in fermentor gas.

When given in vivo for 8 days at 6·7 mg/g hay D.M., potassium chlorate progressively depressed total VFA concentration in rumen fluid, had no effect on VFA molar proportions but caused a small increase in the CO2:CH4 ratio in rumen gas. When administered in vivo for 3 days at 14·4–15·3 mg/g hay D.M. the treatment increased the molar proportions of propionate and depressed those of acetate in rumen fluid without affecting total VFA concentration. There were considerable differences between animals in propionate response, and the maximum responses were generally obtained 2–5 days after dosing had ceased. Potassium chlorate addition also caused a temporary reduction in appetite with some sheep.

It was concluded that potassium chlorate was toxic to the rumen microbial population when given for 8 days, but that large doses given over 3 days could be used to increase the ratio of propionic acid relative to acetic and butyric acids produced from the rumen fermentation.

When cowpea plants were grown in large pots under simulated tropical conditions, and were dependent on either symbiotic fixation or inorganic N for their total nitrogen requirements, short periods of waterlogging had adverse effects on vegetative growth and seed production. The effects of waterlogging were more acute as plants experienced stress at progressively earlier stages of development. In plants depending either on biologically fixed N or inorganic N, waterlogging before flowering reduced vegetative growth by about 50%. Although some compensation in vegetative growth occurred during the reproductive development of nodulated plants, seed yields in both cases were still 48% less than in unstressed plants. Depending on the stage of plant development, treatment effects were mediated largely through changes in branch, peduncle and flower production and/or abortion, which contributed directly to variations in the number of pods retained to maturity. Inorganic nitrogen stimulated vegetative growth but did not significantly improve seed yield compared with effectively nodulated plants.

Four diets were fed to two Friesian bull calves fitted with re-entrant duodenal cannulae. The diets contained no poultry litter (diet 0); 30% poultry litter (diet 30 D); 50% poultry litter (diet 50 D) or 30% poultry litter which had been ensiled at 45% moisture content for 3 weeks (diet 30 W). The total flow of digesta from the abomasum was measured over four 24 h periods for each diet.

The flow of dry matter and organic matter to the duodenum was similar on all four diets but the percentage of apparent digestion occurring in the stomach was higher when the diets containing poultry litter were fed.

Less nitrogen was digested in the hind gut on diet 30 W than the other three diets. Greater amounts of the nitrogen ingested and also of the nitrogen flowing to the duodenum were apparently digested in the hind gut on the diet containing no poultry litter. Microbial protein synthesized/100 g organic matter apparently digested in the stomachs was lowest when the calves were fed the 30 W diet.

The results obtained in these experiments were then used to evaluate the results of growth trials previously reported.

Two sheep, with and without ciliate protozoa, were fed on a wood-pulp cellulose, corn starch, soya-bean protein diet and the microbiological and chemical characteristics of the rumen ingesta of both sheep were studied. The purified diet led to a simplified rumen flora enabling some deductions to be made about the interactions of the principal bacterial species and their interactions with the protozoa in relationship to the biochemical analysis of the rumen. Ammonia concentrations were similarly low in each animal. Total volatile fatty acid concentrations were higher in the faunated sheep though the proportion of propionic acid was highest in the unfaunated sheep. Cellulose digestion in the faunated rumen was about twice that in the unfaunated one. Total bacterial concentrations in the unfaunated rumen were over twice those in the faunated rumen, but the numbers of cellulolytic bacteria were higher in the latter while the numbers of amylolytic bacteria were higher in the unfaunated rumen. The principal species of bacteria differed in the two rumens.

Long-term undernutritional stress is often a feature of sheep and beef cattle production, but has only become a major feature of dairy cattle husbandry in the United Kingdom in recent winters when food was short and expensive. An experiment was carried out to study the effects of long-term underfeeding during pregnancy and early lactation on some blood constituents, milk yield and composition and body weight of dairy cattle. Two groups of cattle were fed at 60 and 40% of the estimated requirements for maintenance and pregnancy or lactation for 13 weeks before and 13 weeks after calving, and one group was fed at the maintenance level only for the same period. A control group was fed at 100% of estimated requirements for this period. All groups were subsequently fed at the control level for a further 24 weeks.

The experiment showed that cows undergoing long-term nutritional deprivation were able to maintain concentrations of blood constituents within narrow limits; the concentrations of such constituents as glucose or non-esterifled fatty acid did not reflect energy deficit or surplus. The animals remained clinically healthy during the underfeeding and recovery periods. The results suggest that debility occurring under field conditions in association with reduced food supply may be due to a multiplicity of factors or to severe imbalance of specific nutrients, rather than to energy or protein deficit alone.

There was a difference in efficiency of utilization of energy of 19% between cows in the most severely underfed groups which maintained lactation and those which were not able to maintain lactation. There was evidence that this difference in efficiency was detectable within a few weeks of the start of the period of reduced nutrition. Animals which were less affected in the early stages of food deprivation were also those which maintained the advantage through the deprivation and recovery periods.

In this paper we present a series of resolvable incomplete block designs suitable for variety trials with any number of varieties v in the range 20 ≤v ≤ 100. These designs usefully supplement existing square and rectangular lattices. They are not necessarily optimal in the sense of having smallest possible variances but their efficiencies are known to be high.