Phosphates and nitrate were added to the gel used for fluid drilling without affecting its properties as a seed carrier. The addition of monosodium phosphate promoted early seedling growth but at concentrations higher than 30 g/1 it became phytotoxic. Nitrate added to the gel reduced plant growth and decreased the number of seedlings emerging. Ammonium phosphate was found to be an effective addition to the gel and could be used in the form of a proprietary liquid ammonium polyphosphate fertilizer. The earlier emergence of fluid-drilled germinating seeds and the enhanced growth brought about by phosphate addition to the gel increased plant size compared with that of the dryseeded controls. The results are discussed in relation to the early production of marketable-size carrots.

Two maize hybrids, NHYB-1 and NHYB-2 with upright leaf orientation, and two composites, FARZ 27 and 34 with lax leaf orientation, were compared. The crops were grown at three levels of nitrogen (0, 75 and 150 kg N/ha) at Ibadan in the rain forest zone of Nigeria in 1979 and 1980.

N application increased leaf area index (LAI) and hastened flowering. The composites had greater LAI than the hybrids. Lodging was greater at harvest than at mid-silk and severer in the hybrids than in the composites. Grain, stover and total dry-matter yields were greater for the composites.

The hybrids were more responsive to N application in 1979 but the pattern was not consistent in 1980. More dry matter was partitioned to the grain in the hybrids as shown by their higher harvest index, especially in 1979. The concentration of N in ear leaf and stover increased with increase in N application, but P and K concentrations in the stover were highest in the control treatment.

Relative adaptability of Chokla and Rambouillet × Chokla half-breds was compared by observing their responses on exposure to summer stress for 6 days and also under accentuated stress by deprivation of drinking water till the animals lost 30% of their body weight. Responses of both the breed groups were similar on 6 days exposure. Accentuated summer stress resulted in decreased feed intake followed by 15, 26 and 31% loss in body weight on 1st, 2nd and 3rd day of exposure, respectively. Progressive decline in faecal moisture, increase in rectal temperature and decrease in morning respiration rate were also noted in both the breeds while an increase in pulse rate was recorded only in the cross-breds. Increase in respiratory or pulse rate for unit rise in rectal temperature was found to be higher in the cross-breds. On accentuated thermal stress, haematocrit values were higher in the cross-breds and blood potassium concentration was higher in the Chokla while blood glucose decreased in both the groups. Under the conditions of short-term exposure to summer stress the cross-breds maintained homoeothermy as well as the Chokla.

A study was carried out for 2 years in the arid zone of the northern region of the Sudan to investigate the effects of watering intervals on flowering, growth, yield and yield components of three groundnut cultivars. The variation in air temperature prevailing above the canopy through frequent and extended watering intervals affected the periodicity of flowering. MH 383 gave the highest pod yield and it was drought tolerant compared with Ashford and Turkish cultivars. Pod losses were smaller with longer watering intervals. Number of pods per plant was the yield component most affected by watering. Leaf area index increased with frequent watering and reached a value of 5·8. Net assimilation rate decreased at first, but later increased with the pegging of gynophores.

A bulk seedling test is described which can be applied shortly after completion of a crossing programme. The test assesses resistance to G. pallida in progeny derived from crossing programmes involving S. luberosum, S. vernei and S. tuberosum spp. andigena. It provides good estimates of both the mean level of resistance within progenies and the breeding value of the parents. The test was applied to a crossing schedule involving a half-diallel and a North Carolina 2 design utilizing a range of material. The results and their implications are discussed.

Phosphorus requirements for maintenance and growth were assessed by giving to growing lambs and non-pregnant ewes diets low in P and to growing lambs a diet containing the quantity of P recommended by the Agricultural Research Council (1980).

Seven 14-week-old lambs were given ad libitum a pelleted diet containing 1·88 (LP) or 2·75 (NP) g P/kg D. M. for 13 weeks. There was no effect of P intake on feed intake or growth during the first 8 weeks when the P intake of the LP groups was 1·07 of Agricultural Research Council (1980) requirements. During the last 5 weeks the P intake of the LP group was only 0·87 of Agricultural Research Council (1980) requirements and growth and feed intake were higher in the male but not female lambs in the NP group. From the 3rd week the plasma concentration of P was significantly lower (P <0·001) in the LP group. Mineralization of selected bones was less in the LP group.

After 14 weeks on the diet, balance trials with 32 P were carried out on the lambs from each dietary group. P intakes ranged from 1 to 3 g/day. An additional balance trial was undertaken with eight 2-year-old female sheep consuming a hay diet (1·5 g P/day).

The endogenous faecal excretion of P by the growing lambs on the LP diet and ewes was 12·2 ± 0·8 and 12·7 ± 1·00 mg/kg live weight/day respectively, very close to the value (12 mg/kg live weight/day) adopted by the Agricultural Research Council (1980). The absorbability of the P in the concentrate and hay diets was 0.71 ±0·267 and 0·74 ± 0·0218 respectively, the former agreeing with and the latter higher than the corresponding value for Agricultural Research Council (1980).

Ultrasonically measured backfat depths and subjective fat and conformation scores taken on 123 Romney ewes were related to the chemical composition of the carcass in trial 1. Fat depths at one position over the eye muscle, determined using ultrasonic machines with a single probe, were similar to the best judge's fat scores at predicting carcass composition after adjustment for pre-slaughter live weight. Fat depths measured from a two-dimensional scan (Danscan) did not predict carcass composition as well as most of the judges' fat scores. Judges' conformation scores failed to improve the prediction of composition after adjustment for live weight and fat score.

In trial 2, two ultrasonic machines of the single probe type provided accurate measure of carcass fat depths on both full fleeced and shorn sheep. Ultrasonically measured fat depths would appear to be a useful method for selecting lean breeding stock and for training inexperienced stock judgesto assess fatness of sheep.

Two-year-old Romney wethers were fed diets with (a) varying proportions of N (0·5, 1·1, 1·4 and 3·4%) while on similar digestible organic matter (DOM) intake, and (b) the same proportions of N with different DOM intake.

The composition of rumen volatile and unesterified fatty acids, as well as of lipids and fatty acids of plasma, liver, muscle and perirenal fat, was determined.

When the proportions of dietary N were varied the findings were as follows: in the rumenahigh level of propionate (37%) was found on the 1·4% N diet, unsaturated fatty acids constituted between 20 and 30% of rumen unesterified fatty acids with diets containing 0·5 and 3·4% N, while sheep on 1·1 and 1·4% N diets had 70·80% unsaturated fatty acids. In plasma and tissues other than the liver there was a greater proportion of unsaturated fatty acids in sheep fed the 1·4% N diet. Total liver lipids were highest on the 0·5 and 3·4% N diets. Perirenal fat was highest on the 0·5% N diet.

With the exception of unesterified cholesterol, tissue and plasma cholesterol concentrations decreased with increasing dietary N content.

Increased DOM intake while the proportion of dietary N was kept constant caused few changes in lipid and fatty acid composition of rumen, plasma and tissues.

Protein synthesis was measured in non-breeding sheep and in sheep at two stages of lactation by constant intravenous infusion of [3H] tyrosine. In early lactation plasma tyrosine flux was 50% higher than in non-breeding ewes and it remained somewhat higher in late lactation. Estimates of protein synthesis per day in the whole body showed similar changes.

In early lactation the weights of the longissimus dorsi and semitendinosus muscles were respectively 37 and 28% lower than those for non-breeding ewes, but both muscles regained weight in late lactation. There were corresponding changes in the total protein, total RNA and total lipid contents of both muscles.

The fractional rates of protein synthesis in the longissimus dorsi and the semitendinosus were between 2 and 3% per day, but it was higher in heart muscle. At both stages of lactation the synthesis rate in the longissimus dorsi was similar to that in nonbreeding ewes, but in the semitendinosus and in the heart synthesis rates were lower in lactating animals. In both skeletal muscles the total protein synthesized per day was lower in early lactation because their total protein contents were lower at this time. It is concluded that the maternal skeletal muscles may undergo a controlled depletion during lactation.

Cattle were fed four hays in mineral balance experiments. Two of the hays (Cenchrus ciliaris and Setaria sphacelala var. sericea) contained 1·8 and 1·3% total oxalates and provided above- and below-maintenance intakes of calcium respectively. These grasses contain calcium oxalate crystals. The other two hays (Aristida spp –Bothriochloa spp. mixture and Triticum aestivum) contained 0·1% oxalates, and also provided above- and below-maintenance intakes of calcium. The absorptions of calcium from the hays providing above-maintenance intakes were 51% for the high and 57% for the low oxalate hay. At below-maintenance intakes, the cattle were in negative calcium balance and calcium absorptions were 52% for the high and 64% for the low oxalate hay. While in negative calcium balance the cattle were given single doses of calcium oxalate, followed by single doses of either limestone or rock phosphate. The cattle fed S. sphacelata hay absorbed sufficient calcium from calcium oxalate to achieve positive calcium balance, although the amount absorbed was only 52% of that absorbed from limestone. The cattle fed T. aestivum hay also absorbed calcium from calcium oxalate, but in insufficient amount to result in a positive calcium balance. The amount absorbed was 47% of that absorbed from rock phosphate. The results demonstrate that in tropical grasses containing calcium oxalate crystals, the availability of calcium is about 20% lower than it is in grasses containing little oxalate. Adaptation to oxalate may improve the ability of the rumen to utilize calcium oxalate. It is suggested that the availability of calcium to cattle grazing tropical grasses should be considered to be a maximum of 50%. Neither magnesium nor phosphorus absorptions from tropical grasses were affected by oxalate.

In a breeding programme to combine quantitative resistance to two important potato pathogens, Phytophthora infestans causing late blight in foliage and Qlobodera pallida (the cream potato cyst-nematode), tetraploid (4 ×) off spring were obtained by crossing dihaploids, mainly as females, with tetraploids. Glasshouse and field tests in the first and second tuber-years showed that most of the off spring of highly blight-resistant dihaploids had high resistance to P. infestans. Two such dihaploids, PDH 182 and PDH 247, crossed with a tetraploid selected for high general combining ability for potato cyst-nematode (PCN) resistance, gave off spring all of which were highly blight resistant. About one third also had high PCN resistance.

Detached leaflet tests were used for rapid blight resistance screening of other progenies from dihaploid × 4 × crosses in their seedling year. Differences were found in the effects of 4 × parents on the mean resistances of progenies from blight-resistant dihaploids.

The results also showed differences between dihaploids in their effectiveness in transmitting blight resistance to 4 × offspring. This could be due to differences in the mode of unreduced female gamete formation, i.e. first division restitution or second division restitution (SDR). If all the unreduced gametes were produced by SDR, the differences could be due to differences in homozygosity between dihaploids with respect to blight resistance genes.

The dihaploid × 4 × crosses gave few offspring per pollination. The few seedlings obtained may be offset by a higher frequency with the required characters. Since fewer seedlings would have to be grown in order to find the required combination of characters, savings could be made in planting and resistance-testing facilities over those required in conventional breeding.

The tetraploid hybrids obtained can be used in a second cycle of breeding in three ways simultaneously: by crossing with other tetraploids, by crossing with dihaploids selected for complementary characters and to produce dihaploids with combined resistances.

The inheritance of resistance to Globodera pallida was studied in seedling progenies derived from Solanum tuberosum ssp. andigena CPC 2802 (H3) and S. vernei and compared with resistance to G. rostochiensis derived from S. tuberosum ssp. andigena CPC 1673(H1). The resistance of CPC 2802 was originally thought to be due to a major gene (H3), but results presented here demonstrate that it and that derived from S. vernei are inherited in a similar manner quite distinct from the major gene inheritance from CPC 1673 (HI). It is concluded that the resistances derived from CPC 2802 and S. vernei are both polygenic in nature. These findings are discussed in relation to breeding policy and screening methods.

Sixteen cultivars of beans (Vicia faba L.) were evaluated in a triple lattice experiment over 2 years. Differences among and within minor and equina groups were significant for most of the measured traits. In general, among equina and minor groups, the variability of means for yield components was higher than the variability for seed yield per plant. Most European cultivars were lower in yield potential and in number of branches per plant, taller and later in maturity than North African cultivars.

Significant positive correlations were found for seed yield per plant with weight of pods per plant and with number of pods per plant. These results indicate their value for improvement by indirect selection for seed yield. On the other hand, significant positive correlations were also obtained between number of seeds per pod and pod length and between number of seeds per pod and 100-seed weight. The correlation coefficients for height and number of days to maturity with seed yield per plant were negative but insignificant. Other correlation coefficients were also insignificant and low in magnitude.

Twenty-four sows and their 4- to 7-day-old litters were observed in batches of four for approximately 2h to ascertain piglet teat preferences and timings of suckling periods. In each batch, two litters were then selected to have two piglets exchanged between them while the other two remained intact as controls. In the subsequent 3 h, sows with fostered piglets initiated significantly more suckling periods than controls; but many were disturbed at an early stage and only 35% of such periods resulted in milk letdown (compared with 93% in controls). Many sows displayed aggression specifically towards fostered piglets. Many fostered piglets showed signs of distress and attempted to escape. Fostered piglets were significantly more likely to take 10 sec or more from the start of suckling to approach the udder, and less likely to be sucking at milk letdown. Many of these effects were greater when piglets had to compete with a resident piglet with the same teat preference and all were still evident in the third of the three observation hours.

The effect of drought on the growth and subsequent recovery growth of containergrown perennial ryegrass plants was assessed in a glasshouse. Dry-matter production and percentage of water-soluble carbohydrates were measured, and non-destructive measurements of growth components (leaf extension, leaf appearance and tillering) were made.

Drought had an effect upon all the variables recorded. Selecting for improved recovery growth was considered to be of more economic importance than selecting for improved growth during drought and the implications of defoliation are discussed in relation to drought recovery.

It was concluded that subjecting pot-grown plants to drought was a useful technique when screening selections for response to drought.

Nineteen ecotypes from northern Britain and selected genotypes of a cultivar of L. perenne were assessed in controlled environments for shoot growth at low temperature and irradiance and also short daylengths. The ecotypes were collected from a range of altitudes at sites experiencing estimated mean monthly temperatures in the coldest month between -0·1 and + 4·2 °C.

A clinal relationship between low temperature growth and the winter temperature at the place of origin of the ecotypes could not be found in these experiments. Low temperature growth was not generally associated with altitude of origin of the plants, but in this study some of the plants collected from mid-altitude were exceptional in leaf growth produced at 5 °C. Types of L. perenne which extended leaves quickly also produced heavier shoot weights than other types less able to show rapid leaf extension at low temperature. The exceptional ecotypes may provide useful basic plant material for breeding cultivars of L. perenne to grow at low temperatures, and irradiances and short daylengths. Several possible explanations are discussed for the differences in shoot growth found between L. perenne ecotypes at low temperature.

Halo blight resistance was transferred in a backcrossing programme from PI 150414 to a Michigan-type bean. The resistant selections obtained gave yields that were up to 10% higher than that of cv. Seafarer and had seed of good quality that was suitable for baking in tomato sauce. These selections were also resistant to the common strains of bean common mosaic virus (BCMV) and to the lambda race of anthracnose.

In addition, selections with white seed of similar size to Seafarer were obtained from crosses between Seafarer and cold-tolerant lines with large, coloured seeds. In trials over 4 years these selections gave 20% higher yields than Seafarer and were less sensitive to environmental changes. Like Seafarer, they were homozygous for the I gene for resistance to BCMV but were susceptible to halo blight and anthracnose. Although not as suitable for canning in tomato sauce as other material in the National Vegetable Research Station programme, they offer useful parental material for further cycles of breeding.

Very experienced livestock judges and three ultrasonic machines were compared for accuracy in predicting carcass composition.

Sixty-four steers of mixed breed were visually scored for fatness and meat yield by seven judges. Subcutaneous fat depths over the eye muscle at the 13th rib were measured with three different ultrasonic devices prior to slaughter. There was little difference between the ultrasonic machines and the best visual estimates of fatness for predicting weight of commercial trimmed or total dissected fat. Visual estimates of meat yield were not as accurate as the judges' fat scores for predicting carcass composition.

Subcutaneous fat depths measured by ultrasonics were shown to be as well related to carcass composition as the best judge's fat scores.

Free amino·N estimations were used to monitor the movement of free amino acids in blood passing through the hindquarters of sheep and growing pigs. The net uptakeor release of free amino·N was calculated from arterio-venous differences in the concentration of free amino·N measured in whole blood and plasma at short intervals of time.

In both species the net change was an apparent release of free amino·N into venous blood. The release increased on fasting. Net uptake of free amino·N from blood was occasionally found at single sampling times due to loss from the cell compartment in sheep and from the plasma compartment in pigs. The uptake measured in whole blood was always less than in a single compartment of blood. The greatest fluctuation in free amino·N concentration occurred in the cells of aorta blood.

It is concluded that both blood cells and plasma have independent roles in the net flux of free amino·N requiring determinations of amino acids in both whole blood and plasma to describe the exchange of blood free amino acids with tissue. A negative arteriovenous difference of free amino·N in blood across skeletal muscle is normal for healthy well-fed animals. Fasting increases the negativity.

A dynamic model of rumen processes is constructed. The nine state variables considered are: rumen metabolic volume, non-rumen-degradable β-hexose, rumen-degradable β-hexose, α-hexose, water-soluble carbohydrates, non-protein nitrogen, rumendegradable protein and non-rumen-degradable protein. The dietary and salivary inputs to the rumen may be continuous, or pulsed. Rumen outflow given by the model is compared with data on sheep fed with different diets. Reasonable agreement is obtained when the model is run in the continuous mode, but there are considerable discrepancies between the experimental data and the pulsed model.