The incidence of lamb mortality from weakness at birth, underdevelopment, exposure and starvation was examined over 6 years in an upland flock and analysed in relation to breed, breeding system and other factors. These causes accounted for more than a quarter of the deaths and contributed to many more.

The frequency of death due to these causes was greater in lambs light at birth. The incidence of these causes of death differed significantly between the breeds, Scottish Blackface, Cheviot and Welsh Mountain and their crosses, but for the separate categories breed variation was significant only for the incidence of death by starvation, which was also less frequent in cross-breds than purebreds. Mortality from several of these causes was increased by inbreeding (25–59%), but decreased by crossing inbred lines. Lambs born to line-cross or other non-inbred dams had a relatively low incidence of these various causes of death. For underdeveloped lambs variation due to maternal inbreeding was significant. When classes were adjusted for difference in birth weight, breed variation in mortality was greatly enhanced but variation due to inbreeding much reduced.

Slightly more twins than single-born lambs died from these causes and triplets fared worst, but such variation was significant only for death from exposure. Mortality from these causes varied significantly with parity of dam, being highest in the first, and mortality in males was slightly but not significantly higher than in females.

Azospirillum brasilense was treated with nitrosoguanidine and two mutants isolated which were resistant to 500 μg streptomycin/ml. Ultraviolet sensitivity, photoreactivation and effect of acriflavin on pre- and post-irradiation were studied. Chick pea showed an increase in grain yield, nodule dry weight, N2ase activity and active iron content of nodules when inoculated with A. brasilense or its mutants together with Rhizobium. The interaction between Rhizobium strains and genotypes of chick pea was significant.

Heat stored in the body of cattle subjected to a daily 10 CC range of environmental temperature was measured by calorimetry and thermometry. The daily range of bodycore temperature of the animals was of the order of 0·5 °C but mean skin temperature cycled with a range of approximately 6 °C. Calorimetric estimates of changes in mean body temperature showed good agreement with thermometric estimates when core and mean body temperature changes were weighted in the ratio a: (1 – α) where α was found to be 0·85. This result is consistent with the findings of another study where cattle were subjected to abrupt changes in environmental temperature, the combined best estimate of a from the two studies being 0·86 ± 0·014 (s.E.). The 10 °C range of daily environmental fluctuation resulted in a daily variation of approximately 1 °C in mean body temperature, which is equivalent to the amount of heat produced by the animals every 40 min. It is suggested that a weighting factor α = 0·86 could be employed, using thermometry only, to estimate fluctuations in body heat storage which are likely to occur in animals subjected to fluctuating environmental conditions in the field.

The incidence of various infectious and non-infectious diseases as causes of death in lambs up to 8 months of age was studied in relation to breed, inbreeding and other factors. The data from an upland grazing flock covered 6 years and involved the Scottish Blackface, Cheviot and Welsh Mountain breeds and the crosses among them.

Infectious and non-infectious diseases were directly responsible for almost a quarter of the mortality and their presence contributed to many more deaths. The organisms mainly responsible were Escherichia coli, Pasteurella spp. and Fusobacterium necrophorum.

The incidence of infectious diseases in general and enteritis in particular varied significantly between the breeds and was lower in the cross-breds than in the purebreds. Variation between the breeds in the incidence of non-infectious diseases was statistically significant only in respect of digestive upsets for which there was a similar ranking of breeds to that for infectious disease.

Inbreeding of the lamb (25–59%) significantly increased the incidence of infectious diseases, especially respiratory diseases, but not of non-infectious diseases. There was little difference between singles and twins in susceptibility to disease. The lower the birth weight of the lamb the greater the risk, particularly of non-infectious disease.

Diurnal and seasonal changes in the total, osmotic and turgor potentials of winter wheat leaves are compared in two seasons of mild and severe soil water stress. Gradients of total water potential in the soil-plant system are also presented. In both seasons the total water potential of the leaves decreased in parallel with the soil water potential, concurrently leaf osmotic potential also decreased sufficiently to maintain positive leaf turgor potential. Eventually, under severe water stress, soil water potential approached –1·5 MPa and leaf turgor potential tended to zero during the middle of the day.

The potential drop across the soil-root system was twice that along the stem. Estimates of the water potential at the root surface varied diurnally and were often lower than the bulk soil water potential. In dry soil plants were unable to equilibrate with the soil water potential overnight. These results are consistent with the existence of significant resistance to water flow across the rhizosphere.

Effects of supplementary irrigation at three periods of grain sorghum development (a) from emergence to a time after floral initiation was completed (b) during heading and flowering and (c) from ending of flowering to maturity, during two seasons, were tested. Grain yield and its components and straw yield were significantly affected by the irrigation treatments, which were themselves considerably affected by rainfall.

The results suggest that water deficits during the three periods, as were specified in this study, had affected grain yield primarily through effects on number of grains during the first period and size of grains in the second period. Effects in the third period were apparently complementary to those of the first and/or the second periods, being either very substantial or negligible, depending on the rain conditions in these periods. Straw yields were mostly affected by irrigation during the third period, mainly as a result of development of late tillers.

High yields of rain-grown sorghum can be obtained if water deficits are avoided by supplementary irrigation during one or more of its growth periods.

Three Rhizobium strains and four lentil genotypes were more salt tolerant under different salt stress conditions. Saline-resistant strains were more antibiotic resistant and showed higher relative rates of oxidation of carbohydrate and tricarboxylic acid intermediates. Under salt stress, significant interactions between strains and genotypes resulted in a differential response of N2·fixation and glutamine synthetase activity.

The effect of pretreating soya-bean and rapeseed meals with formaldehyde was studied. Soya-bean and rapeseed meals, both untreated and formaldehyde-treated, were fed to cattle receiving a basal diet of silage in a 4 × 4 latin square. Formaldehyde treatment of both meals significantly reduced apparent N digestibility. All four protein supplements increased the amounts of non-ammonia N and amino acid N entering the small intestine over those obtained when silage was fed alone. Formaldehyde treatment of the meals increased the amounts of non-ammonia N and amino acid N entering the small intestine; this effect was significant, however, for only the formaldehyde treatment of the soya-bean meal. The low efficiency of microbial N synthesis observed when silage was fed alone was increased by the inclusion of both of the soyabean meals in the diet but not by the inclusion of the rapeseed meals. Formaldehyde treatment reduced the apparent degradability of the soya-bean meal N, determined in vivo, from 0·90 for the untreated meal to 0·40 for the formaldehyde-treated meal; similarly the degradability of the untreated rapeseed meal was reduced from 0·77 to 0·41 by the formaldehyde treatment. The in sacco technique gave values for degradability for the protein supplements which ranked them in a similar manner as did the in vivo technique; however, for any one meal the in sacco value for degradability was lower than that determined in vivo.

In a 2-year field experiment with potatoes measurements were made at successive harvests of the dry-matter yield of leaves and tubers and of the length of the root system. Experimental treatments were 150 kg N/ha, control plots receiving no N, and each with or without irrigation.

In both years the crop gave increased yields with fertilizer N and irrigation. Fertilizer N increased the weight of leaves and embryonic tubers as early as 6 weeks after planting; it had little effect on water use. Irrigation, which was applied only in the mid-season after water deficits of about 100 mm had developed, increased yields and water use. Highest uptake rates of N, P and K (g/m2/day) occurred 4–6 weeks after crop emergence when they reached 0·62, 0·071 and 0·88 respectively. At harvest the tubers contained (g/m2) N: 8·7–21·1, P: 1·5–2·8 and K: 11·7–27·2. Uptake of all three nutrients was increased by application of N fertilizer and by irrigation.

The average root length for all treatments throughout the season in both years was 12 km/m2 of soil surface, with 84% in the top 30 cm of soil. From values of inflow of water and NO3–-N1 calculated from depletion of successive 15 cm deep soil horizons, roots below 30 cm depth were substantially more active than those nearer the soil surface. During most of the growing season about half the nitrate reached the roots by mass flow.

During crop growth NO3–-N concentration in the soil decreased to less than 10 μg/cm3 to 30 cm depth. Summation of crop N and soil NO3·N indicated net mineralization rates of soil N of between 0·07 and 0·17 g/W/day (average 012 g/m2/day). At final harvest the residue of N of about 9–10 g/m2 on plots that received N fertilizer, included crop residues, NO3–·N left in the soil and leaf fall.

A simple model is presented which can account for the hysteresis observed in the relationship between leaf water potential (χ1) and water flow per stem (Q) in winter wheat. Using this model the total hydraulic resistance (R) and capacitance (C) of the soil-plant system were estimated from measured diurnal changes in χ1 and Q. Daily mean values of R were constant when the soil water potential (χ1) was above – 0·6 MPa, but R increased by about 40% when the soil dried to – 1·5 MPa. R also appeared to vary during the day, increasing in the afternoon and evening.

The results of experiments on the recovery of χ1 in plants from which transpiration was prevented suggested that the major resistance to flow was in the soil-root system and that it was an increase in this resistance which gave rise to the overall increase in R as the soil dried.

There was substantial variation in the estimates of hydraulic capacitance (C) and no systematic diurnal or seasonal trend was evident. Despite the variation in C the mean value for the season, 8 x 10-7 m3/MPa, predicted realistic changes in plant water storage. Estimates of the components of C indicated that the major capacitance was located in the soil-root complex. More information is needed about the components of R and C, particularly those in the soil-root system.

A diallel crossing system involving two Pinto and two Kidney common bean (Phaseolus vulgaris L.) cultivars was evaluated in the field. Pin toes were significantly different from the Kidneys in seed yield and numbers of pods and seeds per plant and 100·seed weight. All the traits showed statistical significance among crosses and in comparisons involving parental v. cross means. Heterosis values were large and significant for yield, numbers of pods and seeds per plant, number of seeds per pod and number of days from planting to flowering. The ratio of general to specific combining ability mean squares was low for yield, numbers of pods and seeds per plant and high for 100·seed weight and number of days to flowering. Significant reciprocal effects were found for seed yield and number of seeds per plant, but this effect was completely absent for 100·seed weight.

Spring barley straw treated with NaOH, either chopped and ensiled or ground and pelleted, was compared with long untreated straw and hay, in mixed diets of compound and forage fed to yearling dairy heifers. Protein allowance and source were varied by the inclusion of either fishmeal, soya-bean meal or urea in the diet.

Growth rate was improved in two out of three trials by chopped ensiled straw treated with NaOH, compared with long untreated straw, and equalled that supported by hay. Dry-matter intake and digestibility were also improved, although rumen NH3-N concentrations were low. With ground pelleted straw treated with NaOH the effects were less decisive: growth rate was increased once and reduced once compared with long untreated straw, but dry-matter intake was substantially increased. Digestibility remained similar to that of long untreated straw, and was unchanged by rate of feeding. NaOH treatment resulted in small changes in molar proportions of VFA. Digestibility of hay fell when concentrates were added to the diet.

Fishmeal increased growth rate with all forms of straw and hay and was more efficient in this respect than either soya-bean meal or urea.

Experiments are described which study the effect of density and chop length on the rate of diffusion of oxygen into silage and equations are presented which enable the rate of diffusion to be calculated under laboratory conditions. The concept of zero porosity is also discussed and methods of calculating the density at which it occurs are given. The effect of carbon dioxide on the rate of diffusion is also discussed.

Nitrosoguanidine-induced acid-tolerant mutants S1 and M1 of Lens esculenta Rhizobium leguminosarum were used for nodulation and symbiotic N2-fixation in acid soils having different pH and associated factors of acidity. The range of soil pH and associated acidity factors in which nodulation and N2-fixation responded varied, depending on mutant strains. However, strain M1 was more responsive and effective than S1. Antagonistic effect of Mn to Fe was found when the active Fe2+ and total Mn were determined in fresh nodules.

Sequential dry-matter measurements for winter wheat crops grown at different sites during different seasons were plotted against accumulated potential evaporation. A relation consisting of two intersecting straight lines represented the observations. Early crop growth had a gentle slope due to an incomplete leaf canopy. Later growth occurred at a rate which depended upon the amount of applied nitrogen, the amount of radiation and the availability of water. The intersection occurred consistently at a leaf area index of 1·25.

Exact equations to predict the leached fraction of fertilizer applied at the soil surface with irrigation water have been derived from solutions of the equation of hydrodynamic dispersion. These exact equations are compared with an approximate equation derived by Pandey (1979) for the same problem; his equation sometimes gives rise to considerable errors.

An experiment is described which investigated the combined effects of fertilizer nitrogen and a medium-large-leaved variety of white clover on the production from a mixed sward. Over a period of 3 years six rates of nitrogen fertilizer ranging from 0 to 750 kg/ha were applied annually on three different sward types cut five times per year. The swards consisted of S. 23 perennial ryegrass alone, S. 23 ryegrass plus Blanca white clover, and Blanca white clover alone. Averaged over the 3 years the nitrogen rate required on the pure-grass sward to give the same yield of dry matter as the grass plus Blanca clover sward with no fertilizer nitrogen applied was 265 kg/ha; the corresponding application rate to achieve equal crude-protein yield was 322 kg/ha. Blanca had an additive effect on the yield from the mixed sward at nitrogen rates up to at least 300 kg/ha. The results from this experiment are compared with those from experiments in which medium-small-leaved varieties of white clover were used. The role of white clover in providing savings in nitrogen fertilizer input on grassland is discussed. Estimates from the results indicate that the nitrogen rates required to produce an annual herbage dry-matter yield of 12 t/ha were 340 kg/ha on the pure ryegrass swards, and 140 kg/ha on the ryegrass plus Blanca sward. The nitrogen fertilizer saving due to the inclusion of Blanca white clover in the sward was, therefore, 43%. A similar estimate from the results of an earlier experiment with the medium-smallleaved variety Aberystwyth S. 100 suggests a nitrogen fertilizer saving of 21%.

A site containing plots of sainfoin, red clover, lucerne and hybrid ryegrass, each sown as a pure stand, was grazed by sheep three times in the first and second harvest years and once in the third. Crop growth was studied during the 8 weeks preceding each grazing.

Sainfoin had a high proportion of green leaf and a high weight per unit area of leaf, and the stem as well as the leaf was readily eaten. The yield and persistence of sainfoin were poor, the number of plants and the number of shoots per plant were low, the development of leaf area was slow, and nitrogen content and digestibility were rather low.

Red clover had a high proportion of green leaf, large leaves, high nitrogen content and fairly high digestibility, and the stem as well as the leaf was readily eaten. Yield was low except at the first two grazings of the first harvest year, and persistence was poor, there being a large number of plant deaths near the time of the second grazing.

Lucerne was higher yielding and more persistent than the other legumes, with a satisfactory number of plants, a relatively large number of shoots per plant, a high rate of emergence of leaves and a relatively large amount of branching. The lucerne had a rather high proportion of stem, and the stem was of rather low digestibility and not very attractive to the sheep.

The hybrid ryegrass yielded more herbage than the legumes, had a satisfactory and increasing number of tillers, increased in yield relatively early in spring and recovered well after defoliation. The proportion of green leaf was low by the end of each of the first two growth periods of each year, the leaves emerged at a rather slow rate in the later stages of a growth period, the crop had a relatively high proportion of cell wall and the stem in particular was relatively unattractive to the sheep.

Five feeding and metabolism trials were conducted on buffaloes fed different amounts of groundnut oil as a source of supplemental fat. Ca and P retentions were determined. The first two trials were conducted on 12 and 16 milch buffaloes and the other three trials on 15, 15 and 4 buffalo bulls. The dietary fat ranged from 1·32 to 6·00% of the ration in milch buffaloes and 0·51 to 6·33% in buffalo bulls. The retentions of Ca and P did not differ significantly with the percentage of fat in the ration. This showed that the phenomenon of formation of Ca soaps with fatty acids in non-ruminants with consequent wastage of Ca does not seem to be applicable to ruminants which have a much lower pH in the duodenum and upper jejunum. It is concluded that under practical conditions of feeding, within the usual range of dietary fat in ruminants, there is no likelihood of an adverse effect on Ca and P nutrition such as is encountered in non-ruminants on high-fat diets.

Results relating to a 4-year study of early reproductive traits in traditionally managed flocks of indigenous goats and sheep under semi-arid conditions are reported. Mean weights (least-squares estimates) at first conception of 16·9 kg for goats and 23·4 kg for sheep were recorded, and animals raised under the better environmental conditions of the irrigated rice system had a 2·2 kg advantage at this stage over animals raised under the rainfed millet system. Animals from young and old dams were heavier at first conception than those born of middle-aged dams. Neither season of birth nor type of birth (single or multiple) had any effect on weight at first conception. Age at first parturition was 443 days and at second parturition was 709 days. Animals born of young and of old dams were later at both first and second parturitions than those born of middle-aged dams while age at first parturition was younger for those animals reared in the rice system. Age at first parturition was within the range normally found for these types of animals under these environmental and social conditions. An early first parturition, even with a high death rate of offspring, may contribute to a greater total lifetime production than a later parturition with a lower death rate.