Mean progesterone concentrations were measured in the peripheral plasmas of Merino and Border Leicester × Merino ewes which were fed from day 2 to day 16 after mating on rations designed to provide twice maintenance (2 M), maintenance (M) and one quarter maintenance (¼ M) of food requirements. Mean plasma progesterone concentrations were consistently higher in the ¼ ewes than in the M or 2 M ewes whether they had two corpora lutea (CL) and two embryos surviving or one CL with either one embryo surviving or no embryo surviving, and tended to be lower in the 2 M than M ewes. It is concluded that there is an inverse relationship between levels of nutrition and progesterone within an oestrous cycle in ewes.

The growth, development and yield of pigeon pea (cv. Cita-1) grown at three population densities of 27 000, 55000 and 83000 plants/ha were evaluated in two field trials during the growing season of 1980.

The results obtained showed that there was a progressive reduction in the developmentv per plant of vegetative characters, dry-matter accumulation and yield characters as population density increased. The calculated growth rates (net assimilation rate, crop growth rate, relative growth rate and leaf area ratio) were more or less the same at all population densities. The yields of seeds were 0·39 and 0·51 t/ha for the lowest population density, 0·43 and 0·65 t/ha for the medium population density and 0·58 and 0·75 t/ha for the highest population density for the two trials respectively.

It would seem, therefore, that under the prevailing lowland humid tropical conditions, a population density of at least 80000 plants/ha would be needed to ensure maximum productivity in the sole cropping of pigeon pea.

Right sides of carcasses of 12 buffalo, nine ½ Friesian ( Friesian x Egyptian Baladi) and nine ¾ Friesian ( Friesian x ½ Friesian) bulls slaughtered over the body-weight ranges 161–560 kg for buffaloes and 176–448 kg for cattle were cut according to the Chicago style of cutting. Allometric growth pattern and distribution of muscle and bone in the various cuts were examined.

Buffaloes were similar to cattle in that muscle and bone in the limbs showed an increasing distoproximal growth gradient. On the ventral line of the trunk, muscles showed an increase in growth impetus from plate to brisket while bone followed a reverse pattern. In buffaloes, growth coefficients of muscle and bone of all dorsal cuts were similar except in the sirloin and chuck where bone was later maturing. In cattle, there appeared a posterior-anterior increase in growth impetus of muscle from the shortloin towards sticking. Within and between genotype-group results indicated that growth of a fatless cut is governed by the growth of its muscle rather than that of its bone.

Compared with Friesian crosses, buffaloes had significantly greater percentages of their total muscle and muscle-plus-bone in the expensive cuts. As total muscle weight increased, the proportion of muscle in BLRC (see p. 318) decreased in cattle but remained almost constant in buffaloes. It was concluded that the previously reported inferior carcass composition of buffaloes relative to cattle is compensated by better carcass conformation and tissue distribution of buffaloes.

The concentrations of adenosine 5′-mono-, -di-, and -triphosphate (AMP, ADP and ATP) in sheep digesta were measured by a new bioluminescence method. ATP in rumen digesta varied with time after feeding and diet, and most markedly according to the size of the population of ciliate protozoa: the ATP content of rumen digesta from ciliate-free sheep was less than a quarter of that of faunated animals receiving the same diet. The adenylate energy charge (EC) (ATP + ADP/[ATP + ADP + AMP]), an indicator of metabolic activity, was high (0·77–0·94) in all rumen samples, but did not appear to be as useful a measurement of activity as ATP alone. As digesta passed along the alimentary tract, the ATP content decreased progressively, from 0·9–2·2 μmol/g dry matter in the rumen to 0·5–1·0μmol/g in the abomasum and duodenum, 07middot;03–0·08 μmol/g in ileal digesta and 0·01–0·02 μmol/g in faeces. EC also tended to decrease, further emphasizing the large decrease in microbial activity which occurs in the hindgut.

In two field trials in 1980, 33, 67 or 100% of the leaves on pigeon pea (cv. Cita-1) plants were removed either at the vegetative stage, the onset of flowering, or at the rapid pod-filling stage, in order to evaluate the effect of reduced assimilatory capacity on the growth and yield characteristics of the crop.

Reduction in the assimilatory capacity of the plant led to significant reduction in the vegetative growth, dry-matter accumulation and seed yield of the defoliated plants compared with the undefoliated control such that 33, 67 or 100% defoliation led to 15–55, 40–60 and 75–80% reduction in seed yield respectively, at both trials. Also, defoliation was more damaging to crop performance if carried out from the onset of flowering than at the vegetative stage. Thus, the seed yields of plants defoliated at the onset of flowering and the rapid pod-filling stage were 30–80 and 40–45 % lower than the yield from plants defoliated at the vegetative stage in both trials.

As a result of the treatment of made whole-crop barley silage with antimicrobial agents which are specifically inhibitory to fungi or bacteria, it was shown that the subsequent aerobic deterioration was essentially caused by yeasts. These microorganisms were instrumental in the rise in pH, the increase in temperature and the loss of dry matter observed. The filamentous fungi, like one group of bacteria (the streptomycetes), apparently had no part in the process. Bacteria, such as the lactobacilli and particularly proteolytic bacteria, may have had a role in the terminal stages of deterioration, although it was considered more likely that the yeasts again were involved.

The whole-crop wheat silage employed in this work was stable in air, a factor attributed to the combined antimicrobial effects of butyric acid present and the relatively high dry-matter content.

Literature dealing with disposal of farm wastes is mainly concerned with smell, heavy metal toxicity, nutrient accumulation and soil physical conditions. Soil is required to filter and absorb the solid material and release a filtrate free from pollutants while remaining relatively unaltered. The importance of soil type in reducing pollution potential is recognized but little study has been made of the effect of pollutants on soil morphology. This paper reports changes observed in a fine silty and fine loamy typical brown earth of the Rheidol series on terrace gravels after treatment with pig slurry. It is concluded that pig slurry spread at the rate of 50 m3/ha per week will cause this permeable soil to deteriorate under an average rainfall of 1117 mm/year unless rest periods are given.

In three experiments the effects of population density, spread in time of seedling emergence and variation in seed size on carrot plant-to-plant root-size variation were investigated.

In the first experiment, coefficient of variation, c.v., of root dry weight was only 27–33% when using uniform growing conditions, graded seed, low population density and synchronous seedling emergence (i.e. over 3–11 days). Allowing asynchronous emergence (i.e. over 8–21 days) increased the c.v. to 32–37%, whereas increasing population density from 25 to 400 plants/m2, but maintaining synchronous seedling emergence, produced a c.v. of 57–73%. Asynchronous emergence combined with high population density increased the c.v. even further to 79–97%. Spread in time of emergence was associated with 5–48% of the plant-to-plant root-size variation. Thus asynchrony of seedling emergence was a source of plant-to-plant root-size variation and this effect was magnified by high population density, but other sources of variation were also important. Statistical analysis showed that the effects of these other sources of root-size variation were no greater in populations where emergence had occurred over only 3 or 4 days than in those where emergence had occurred over 3 weeks.

There was no effect on root-size frequency distribution in a second experiment in which the spread of seedling emergence was truncated from 19 to 14 days by spraying paraquat onto the first seedlings to emerge from field plots.

In a third experiment seeds 1·6–2·0 or 1·0–1·25 mm in diameter were grown in pure or mixed populations under conditions similar to those of the synchronous emergence high-density treatment of Expt 1. Storage roots derived from the large seeds weighed 38% more than those derived from the small seeds. Thus differences in seed size caused some of the root-size variation not already linked with different seedling emergence times. However, the c.v. of root dry weight from all the plants in mixed seed population was not greater than the c.v.s of root dry weight of either of the pure seed populations.

In a pot experiment and two field trials, the apical portionof the main stem of a dwarf variety of pigeon pea (ev. Cita-1) was removed at 3 or 7 weeks after sowing in order to evaluate the effect of apical bud removal, during the vegetative stage of growth, on the subsequent growth, development and yield of the crop.

The early loss of apical dominance led, in all cases, to increased vegetative development, reduced plant height (except in one of the field trials), higher dry-matter accumulation and more pods per plant, with the treatment effect on number of pods being related to the number of branches developed. The yield of seeds was significantly increased by the early loss of apical dominance in the pot experiment and second field trial.

The results therefore show that an early loss of apical dominance, as could happen with insect and pest attack, may not be damaging to the vegetative growth and seed yield of pigeon pea under the prevailing lowland humid tropical conditions.

Four synthetic pyrethroids: fenvalerate, deltamethrin, cypermethrin and permethrin were evaluated as spray deposits on cotton leaves for their contact toxicity to adults of the parasite Chelonus blackburni Cameron (Braconidae). Fenvalerate was found to be the least toxic of the four pyrethroids. In another study five organophosphorus insecticides (profenofos, bromophos ethyl, chlorpyrifos, quinalphos, monocrotophos), three carbamates (U.C.51762, carbosulfan, bendiocarb) and diflubenzuron were evaluated for their contact toxicity to the same parasite. U.C.51762 (carbamate group experimental insecticide) and diflubenzuron were less toxic while the five organophosphorus insecticides, carbosulfan and bendiocarb were highly toxic to the parasite.

Contact toxicity of spray deposits of four synthetic pyrethroids were studied against parasitization and subsequent development of the parasite C. blackburni on thin strips of egg cards Corcyra cephlonica Stainton. It was observed that fenvalerate was not reducing oviposition or affecting subsequent development of the parasite and emergence from the parasitized eggs while the other pyrethroids, permethrin, cypermethrin and deltamethrin, were toxic.

Chick pea Rhizobium strain RG3 was treated with 30 μg/ml of N-nitrosoguanidine and two mutants isolated were resistant to 2000 μg phorate/ml yet retained the capacity to form nodules. On the basis of number of nodules, their dry weight, N2ase activity, total pyridine nucleotides and active iron contents, mutant strains G11 and G26 were found to be equally effective with and without phorate and resulted in significantly greater grain yield.

Soils from grass-arable cropping sequences and from an experiment where grassland had been treated with slurry were dispersed by shaking as a soil-water mixture, followed by ultrasonic treatment. Organo-mineral particle size fractions were separated by sieving and by sedimentation.

Generally, concentration of C and N in the fractions decreased with increasing particle size. However, when expressed as weight of C per fraction maximum contents were in the 2–10 μm range. With N, maximum contents occurred about 2 μm. Largest differences in C and N contents between soils were found in the 0·2–20 μm size range.

Identification of the source of the materials in the various fractions was attempted by interpretation of the C/N ratios, but was generally inconclusive.

Eight Morino lambs equipped with simple cannulac in the duodenum and terminal ileum were divided into two equal groups and used to study the net absorption of calcium, phosphorus and magnesium from concentrate diets supplemented by soyabean meal or by ensiled poultry litter. Mean net absorption of Ca, P and Mg for the soya-bean meal and poultry-litter treatments, respectively, was 31·6, 10·1; 34·7, 35·4; and 51·5, 41·6.

Irrespective of the diet, the small intestino was the major site for Ca and P absorption and the stomachs for the absorption of Mg. A large secretion of P in the stomachs was found with both diets; 8·50 and 9·32 g/day for the soya-bean meal and poultry-litter treatments, respectively.

The results of the present study support the view that poultry litter is a good source of P and Mg for sheep and can be used with deficient diets. Owing to the low rate of Ca absorption from the poultry-litter diet, it appears that at limited levels of inclusion, the extra added Ca would not be a detrimental factor.

Sheep were used to study the utilization of low quality native hay supplemented with urea by different methods. Urea supplement was fed either once daily or twice daily or the same quantity of urea used to spray the hay before feeding. These treatments were compared with basal and groundnut cake based supplemented controls. An attempt was made to balance both the mineral and energy intakes. The provision of extra nitrogen in the form of either urea or groundnut cake resulted in improved weight gain, feed intake and feed conversion. Feeding of urea-sprayed hay marginally improved live-weight gain, feed intake and feed conversion over the other methods of urea supplementation. Dry-matter digestibility and nitrogen retention were increased and urinary nitrogen excretion reduced by feeding the urea-sprayed hay.

The digestible energy (DE) and metabolizable energy (ME) content of eight samples of barley, eight of wheat, four of maize and two each of oats and rye were determined using growing gilts. The DE content of barley ranged from 15·35 to 15·89 MJ/kg D.M., from 15·15 to 16·42 MJ/kg D.M. for wheat and from 16·05 to 16·47 MJ/kg D.M. for maize. DE values for the two oat samples were 12·48 and 12·74 MJ/kg D.M. and 15–04 and 15–47 MJ/kg D.M. for the two rye samples. There was a significant correlation between DE and ME:

ME (MJ/kg D.M.) = 0·050 + 0·965 DE: r = 0·99; P < 0·001.

The ratio ME/DE was significantly influenced by crude-protein content:

ME/DE = 100–0·254 CP%: r = –0·77; P < 0·001.

ME values were also corrected to zero nitrogen retention (MEno) and to 30% nitrogen retention (MEN30). The effect of such corrections was expressed as MEN0/ME and MEN30/ME. Values thus obtained were 0·98 and 1·00 respectively for the pooled values for all cereals.

The data indicated that there was unlikely to be significant variation in the DE content of samples of the same cereal species, selected from commercial sources within the U.K. when evaluated under standardized experimental conditions.

Ten Scottish Blackface ewes from each of three lines, a line selected for hairiness, a line selected for a fine fleece, and an unselected control, were fleece and skin sampled in April, June, September and December, during their 6J year life-span on the hill.

Fleece weight differed between individuals and between lines, and declined by 4% per year from 1·5 kg at 1 year, to 1·3 kg at 6 years. Fleece grade was inadequate as a method of denning fleece differences between the lines.

The height of the spring ‘rise’ in growth in April differed between years, and between lines, declining 2 mm a year from 26 mm at 1 year. Staple length was greatest in the Hairy group and least in the Fine group (P < 0·05). Growth in length was faster between September and December (autumn) than between April and June (spring). Staple length decreased by 14 mm a year.

The lines differed significantly (P < 0·05) in mean fibre diameter but not in modal fibre diameter. There was a highly significant decrease in diameter from summer to winter, ranging from 20% in the Fine line to 31% in the Hairy line, the greater decrease in the Hairy line being attributed to loss of medulla.

The selection had between 1954 and 1972 changed the S/P follicle ratio of 3·0 in the control to 2·8 in the Hairy line and 3·2 in the Fine line. Most seasonal follicle inactivity occurred in April, December came second, and June invariably had more follicle inactivity than September. The control line had the greatest values of primary follicle inactivity and the Fine least. Among the secondary follicles the Hairy line had most inactivity, and the control line least. Maximum primary fibre medullation occurred in either June or September, and medullation was at a minimum in December or April.

Pre-anthesis stem reserve contribution to grain yield was assessed in two spring barley cultivars of contrasting height. It was greatest in the taller, but final grain yields were similar. Partitioning of total reserve capacity to various plant parts showed that the leaf and sheath below the peduncle were most important, followed by stem internodes which had increasing reserve capacity up to internode 4.

It is suggested that stem reserves are valuable for yields commonly achieved in U.K. commercial practice.

High grain yields were associated with large positive increases in stem dry weight after anthesis. This would indicate that the source capacity to boost yield is more than proportional to that required to fill the grain alone.

The activities of some enzymes that regulate the gluconeogenic-glycolytic pathway were measured in sheep liver during late pregnancy, at three stages of lactation and after the lambs were weaned. Of the gluconeogenic enzymes, glucose-6-phosphatase and phosphoenolpyruvate carboxylase activities were unchanged throughout pregnancy and lactation and were similar to the values for non-breeding ewes. The activity of fructose diphosphatase increased 2 times and that of pyruvate carboxylase increased 5–7 times during late pregnancy and in early lactation.

In the glycolytic sequence phosphofructokinase activity declined by about 50% during lactation. Pyruvate kinase activity declined by about 40% at the end of pregnancy but throughout lactation it was similar to the value for non-breeding ewes. Hexokinase activity was very low in all animals.

Cell walls of three bloat-causing legumes, lucerne, red clover and white clover tended to be thinner and disintegrated significantly (P < 0·05) faster during cellulase digestion than those of two non-bloat-causing legumes, sainfoin (reported to contain tannins) and cicer milkvetch (reported not to contain tannins). Response to one generation of selection for speed of mesophyll cell-wall disintegration was marked in a diploid red clover (h2 = 0·66, 1·13) but slight in a tetraploid (h2 = 0·10, 0·13).

Reproductive performance was assessed in a semi-wild Boran cattle herd living on a grassland ranch in Kenya. Male calves copulated with cows a long time after they were weaned naturally. Up to the age of 16 months they were prevented from mating by adult bulls. Female calves conceived at the average age of 25 months and they had their first calves at about 34 months. Calving interval ranged from 304 to 801 days and averaged 430 days. Calving interval of managed Boran cattle living on the same ranch as the semi-wild herd averaged 494 days with a range of 306–798 days. It is concluded that in herds which are permanently accompanied by adult males artificial weaning and the continuous shift of animals between different cattle groups is not a prerequisite for good reproductive performance.