This paper describes the comparative semen characteristics (volume, motility, sperm density, number of sperms, percentage live and abnormal sperms) of Corriedale (exotic) and Marwari and Jaisalmeri (indigenous) rams during the summer and rainy seasons under the arid conditions of Jodhpur, in northwestern India. Except for sperm density, the semen of indigenous animals was superior to that of the Corriedale, although the differences recorded were not of a magnitude to cause the Corriedale sheep to be considered reproductively ineffective under hot arid conditions, if managed properly. The present findings do not conform to the earlier views of the prevalence of ‘summer sterility’ in Corriedale rams observed under hot humid conditions but there appears to be a negative relationship between semen quality and atmospheric humidity. The Corriedale sheep are recommended for improving the sheep sector in the desert areas of Rajasthan.

Adult sheep, unweaned and mature weaned calves have been examined by metabolic studies for sodium balance. The ratio of sodium input/output was near unity with only a very small amount of the ingested sodium salt being retained. A positive sodium balance was always present, with excess sodium salt being excreted. The main channel of sodium excretion was the kidney, although when sodium intake was increased the sodium content of the faeces showed a proportional increase. Unweaned calves, a few days old, were quite able to excrete excess sodium salts in concentrated urine.

There was a clear difference in preference for sodium salts over water, between weaned calves allowed access to sodium salts while being fed milk, and weaned calves denied sodium salts at the milk feeding stage. Sodium-naive calves showed a marked preference for sodium salt solutions while the sodium-experienced calves showed at best an indifference and sometimes even an aversion. With continued access to sodium salts the volume ingested declined steadily in both groups but food intake remained constant.

In both calves and sheep the preference for sodium salts showed considerable variation between animals. The evidence from parallel metabolic studies suggests that this variation indicates that salt intake is controlled by some mechanism, possibly in the central nervous system, which is activated by dynamic sodium metabolism. Our experimental results confirm that ruminants have a well developed salt taste but predilection for sodium salts could be a biochemical manifestation rather than a hedonic propensity.

A series of irrigation experiments was done at Rothamsted where the soil is a flinty silty clay loam over flinty clay. The results are compared with those obtained by Penman (1962, 1970, 1971) at Woburn where the soil is a loamy sand over sand. The limiting deficits, Di, above which irrigation increased yields, were about 2·5 times greater at Rothamsted than at Woburn; this ratio approximates to the ratio of the water-holding capacities of the soils (– 0·1 to – 15 bar) to a depth of 1 m. The limiting deficits at Rothamsted were 80 mm for spring-sown field beans, 84 mm for main-crop potatoes, 100 mm for spring barley and 140 mm for spring and winter wheat. The responses to irrigation were not determined accurately as there were few years with a large response for any crop. However, the evidence is that the maximum response that could be expected for potatoes was 0·19 t/ha/mm water, and for grain dry matter of beans 0·006 t/ha/mm. The figure for potatoes agrees with that obtained by Penman at Woburn; the response of beans was much smaller at Rothamsted, partly because of severe attacks of broad bean stain virus.

Proximal colons taken from foetal and newly born lambs have been shown to actively transport methionine from lumen to blood when incubated under in vitroconditions. The lumen to blood flux of methionine, measured across foetal and early post-natal colons was approximately 25 and 15 times greater than the blood to lumen flux, each flux being determined in the presence of 1 mM methionine.

The ability of the colon to transport methionine decreased with age, there being no net transport across the colon of a 26-day-old lamb. The post-natal disappearance of this transport function appeared to be roughly exponential with a half-time of approximately 2 days.

The short-circuit currents and open-circuit voltages, measured across proximal colons of lambs of different ages, remained stable throughout incubation. The transtissue electrical resistance of colons taken from 9- and 16-day-old lambs was approximately double that recorded across colons taken from younger animals.

These results are discussed both in relation to what is already known concerning amino acid transport in the neonatal pig colon and in relation to what their possible physiological significance might be to normal post-natal development in lambs.

Soil air was sampled daily at depths of 5, 10, 20 and 30 cm in fallow and cropped plots, which had either been rolled or cultivated. Carbon dioxide was measured by gas chromatography.

Carbon dioxide concentrations were greater in the cropped than in the fallow plots. The rolled plots were wetter than the cultivated plots and carbon dioxide concentrations were also greater.

In the fallow plots, carbon dioxide was correlated with soil temperature but variations in soil moisture content had little immediate effect.

In the cropped plots, temperature effects were overshadowed by the response to irrigation which immediately increased the carbon dioxide concentration. These increases were attributed to enhanced root respiration, rather than to restricted diffusion or increased microbial activity.

The relationship has been investigated between the yield of oil-seed rape (Brassica napus L.) plants and (a) the proportion of podless stalks, (b) the proportion of pods infested by seed weevil larvae and (c) the effect of removing a proportion of buds and pods. Plants compensated for damage and, although late removal of buds or pods sometimes caused greater yield loss than early removal, only plants with more than 60% podless stalks or buds removed had diminished yields. The numbers of podless stalks per plant increased with plant size. Removal of 60 % of a plant's pods caused no yield loss; in the field a maximum infestation of only 25% of the plant's pods with seed weevil larvae occurred. The results are discussed in relation to damage by pollen beetles (Meligethes aeneus Fab.) and seed weevils (Ceutorhynch.ua ossimilis Payk.)

Mn, Fe, Cu and Zn were determined in topsoil and herbage samples from sites in North West Pembrokeshire. Means and ranges for these elements are given and the distribution is shown throughout the sampled area.

There are no clear relationships between the total amounts of these elements in the soils and the amounts found in herbage but it is shown that soil drainage strongly influences both soil and plant concentrations, and pH has a strong influence on Mn concentrations in soils and plants.

Seasonal variation in plant uptake of these elements is discussed and the effect of soil contamination of herbage, especially on Fe content. It is hoped that data from this area can be used as a guide to the range of values found for Mn, Fe, Cu and Zn in soils and herbage of an area relatively unpolluted from industrial sources for comparison with more polluted regions.

In two experiments with female Scottish Blackface or Border Leicester x Scottish Blackface sheep nine or ten animals were slaughtered in mid lactation and the remainder either in November at the time of the subsequent mating (Expt 1) or at weaning (Expt 2).

The sheep were infused periodically, including just before slaughter, with 100 μCi tritiated water (TOH) in order to measure total body water by dilution and to estimate body fat using the inverse relationship between the proportions of fat and water in the body. The accuracy of the methods was assessed when the sheep were slaughtered. In the ton lactating Scottish Blackface sheep of Expt 1 fat made up 11.5% of the total body weight with an S.D. of 8·38% whereas the 11 sheep slaughtered at mating were twice as fat (23·2, S.D. 4·01 %). The 25 Border Leicester × Blackface sheep were all thin, whether they were slaughtered in mid lactation (4·4, S.D. 2·56%) or at weaning (3·4, S.D. 2·81%).

The standard error of estimate of body water from TOH space in Expt 2 was 1·2 kg c.v. 2·8%) and lower in Expt 1.

The precision with which an animal could be weighed was very important in determining the accuracy with which body fat could be predicted from live weight and TOH space. In both experiments the standard error of estimate for body fat in lactating sheep was between 600 and 700 g, compared with 1·3–2·7 kg when body fat was predicted from live weight alone. These estimates were sufficiently accurate to be of value in following changes in body composition in live animals as their nutritional and physiological state alters and for comparing animals in groups where the average fatness is greater and the range wider than in the sheep used in Expt 2.

The potential offered for plant breeding programmes by visual scoring techniques for plant water status was investigated in rice and spring wheat. It was found that differing plant morphology could seriously bias visual estimates of leaf water potential, particularly in spring wheat. In spite of this problem, it was found that at least for rice, this type of approach may have potential in future breeding programmes where an estimate of leaf water status is required, such as those for drought tolerance, so long as a high intensity of selection is not necessary.

The relation between the ratio of the natural 12C and 13C isotopes of carbon in the feed and resultant faeces of animals was studied to develop a technique for estimating the proportion of C3 species (tropical legumes) and C4 species (tropical grasses) selected by grazing animals.

In general, theδ13C values (see text for definition) of faeces from rabbits, sheep, goats and cattle were lower (more negative) than those of the corresponding feeds by from 0·4 to 2·0. This was possibly due to contamination in the gut by tissues or fluids with lower δ13C values. When C4 and C3 feeds were alternated, cattle took about a week to fully achieve the new level (δ13C of – 28·7 on the C3 feed and – 13·1 on the C4 feed) in the faeces. This time lag is associated with the time taken for the feed to move through the digestive tract.

When mixed C3 and C4 feeds were fed to rabbits, sheep, goats and cattle there was a negative linear relation between percentage legume (C3) in the feed and the δ13C of the faeces (P < 0·01). A decrease in one unit in the δ13C value was associated with an increase of 7·0–8·5% legume in the diet.

Estimation of the percentage legume in the feed from the δ13C value of the faeces and of the C3 and C4 components of the diet, resulted in a consistent over estimation of the legume component because the faeces had lower values than the corresponding feeds. This bias was removed if the prediction was based on the δ13C of the feeds minus 1 unit; the legume percentage in the diets of the sheep, goats and cattle could then be estimated with a precision of about ± 5%.

Differences in digestibility between the C3 and C4 components greatly bias the estimations. This bias in the diets fed to rabbits was effectively removed by using in vitro organic matter digestibility values of the two components to correct for the differences. Legume percentage in the diet could then be estimated with a RSD of ± 3%.

Advantages and disadvantages compared with alternative methods of estimating the diet of grazing animals are discussed.

Numerous dwarf bean accessions were screened for resistance to three strains of bean common mosaic virus (BCMV). Many lines were resistant to a strain of BCMV isolated at Wellesbourne (NVRS) and the Dutch NL4 strain, but only a few lines showed resistance or tolerance to the Dutch NL3 strain. The NVRS strain was found to belong to BCMV Group IVa.

Hybridization experiments showed that resistance to the NVRS strain of BCMV in the dry bean cvs Seafarer and Aurora was controlled by a dominant gene and that in Seafarer this was probably the dominant I gene originally found in Corbett Refugee.

In 16 experiments with field beans at Rothamsted, Woburn and Saxmundham between 1969 and 1976, seed-bed applications to the soil of dieldrin or γ-HCH were used to control subsequent infestations of the roots by larvae of Sitona lineatus. Rates of between 1·12 and 4·48 kg a.i./ha were used. Larval populations on untreated plots plots were variable, but 70–80% control was usually given by rates of 2·24–4·48 kg a.i./ha. Insecticides nearly always increased yields, the mean increase for all treatments being 0·15 t/ha, but a maximum yield response of over 0·5t/ha was achieved. It is suggested that the importance of S. lineatua larvae as pests of field beans in Britain has been under-rated.

Twelve 6–8 months old male Barbados Blackbelly lambs were used in a 4 × 4 latin square experiment with three replicates to study the utilization of diets made from local by-products and containing 64, 93, 125 or 143 g crude protein/kg D. M.

Both dry-matter (mean 750·1 g/day) and digestible-energy (mean 6·2 MJ DE/day) intakes, and their digestibility coefficients increased, though not significantly, with increasing dietary protein concentration. However, nitrogen digestibility, urinary-nitrogen output and nitrogen retention all increased significantly (P < 0·01) with increasing dietary protein concentration.

Metabolic faecal nitrogen and endogenous urinary nitrogen derived from the intercept of significant regressions of nitrogen intake against urine and faecal nitrogen outputs were 5·07 g/kg dry matter eaten and 3·46 g/day (0·35 kg W0·75) respectively. The diets had a mean biological value of 73·6%. The digestible crude protein requirements for maintenance were (g/day) 29·0, 38·4 and 26·6 when estimated from nitrogen retention, factorially and from live-weight performance respectively.

Three techniques, lamb-suckling and test-weighing, hand- or machine-milking following administration of oxytocin, and measurements of body-water turnover, used for the estimation of milk yield in suckled sheep are discussed in relation to sources of error and comparability of estimates.

Results are presented from an experiment in which the lamb-suckling and the oxytocin techniques were compared. The mean daily milk production of Scottish Blackface and East Friesland × Scottish Blackface ewes suckling single and twin lambs was measured by both methods at weekly intervals for 6 weeks. All ewes were well nourished to ensure full expression of milking capacity. Additional information from a similar experiment on Merino ewes is also presented.

The oxytocin method gave higher estimates of mean daily milk yield in the first week of lactation, especially in the groups of ewes rearing single lambs and in the Blackface breed. By the second week in most groups and the third week in all groups there were no significant differences between estimates made by the two methods and the relative values of the estimates were not affected by level of milk production, number of lambs suckled or genotype of ewe and lamb.

Milk yield of 2-year-old Scottish Blackface and of East Friesland × Scottish Blackface ewes rearing single or twin lambs was estimated by the oxytocin method on 1 day each week up to the 14th week of lactation. Both groups of ewes had been reared from birth under good nutritional conditions. They were housed in individual pens from mid-pregnancy and offered a liberal ration of a pelleted concentrate food until parturition. Similar food was offered ad libitum during lactation.

The cross-bred ewes rearing singles or twins produced significantly more milk in the first 12 weeks (181 and 258 kg respectively) than did pure Blackface ewes in the same period (144 and 208 kg respectively). The pattern of lactation differed between breeds. Cross-bred ewes attained higher maximum yields between the second and sixth weeks (2·37 and 3·32 kg/day, respectively, for single- and twin-suckled ewes) than did the Blackface ewes (1·97 and 2·88 kg/day). The yield from the cross-breds was sustained at a higher level throughout lactation. In the third 4-week period cross-bred ewes rearing single and twin lambs produced 116 and 92%, respectively, of their yield in the first 4 weeks whilst Blackface ewes produced 87 and 65%, respectively.

In the sixth week of lactation the milk produced by the two breed groups was similar in quality (mean value of solids-not-fat 11·04% and fat 5·48%) but by the 11th week the fat percentage of milk produced by Blackface ewes had increased significantly to 7·34% whereas that of the cross-breds had remained almost unchanged.

Single-suckled ewes gained weight throughout lactation but twin-suckled ewes remained relatively constant. Lambs reared as singles by cross-bred or Blackface ewes reached a mean live weight of 36·2 and 35·0 kg at 102 days of age, respectively, compared with 33·6 and 30·1 kg for twin lambs. Food intake of all ewes increased until the fifth or sixth week of lactation.

During 3 years the distribution of pests on ten crops of winter rape and two of spring rape, and the damage they caused, has been determined.

During immigration the adults of all pests infested crop edges more than crop centres, particularly on large crops, irrespective of the presence of wind breaks. The proportion of M. aeneus and G. assimilis at the crop edge gradually diminished as they moved further into the crop, and their larvae and pods with C. assimilis emergence holes were more evenly distributed over the crops than the adults. Damage by M. aeneus was not the only cause of podless stalks. The larvae of D. brassicae were largely confined to the edges of crops; split pods were largely but not solely confined to the edges.

In winter rape crops correlations were found between the percentage of podless stalks per plant and the number of M. aeneus present, and the percentage of pods infested with C. assimilis larvae and the adult C. assimilis population. In two fields infested with D. brassicae the diminution in the proportion of split pods from crop edge to crop centre was positively correlated with diminution in the number of adult D. brassicae.

Three experiments carried out in 3 years (1973–5) which examined the effects of length of sprouting period and temperature of sprouting on growth and yield of three early potato varieties are described. In Home Guard in 1973 at the earliest harvests, tuber yields increased with increase in length and temperature of sprouting period. At later harvests tuber yields decreased with increase in sprouting period especially at the higher temperature (13 rather than 8 °C) and increasing the temperature of sprouting reduced tuber yield. In 1974 length of sprouting period had few effects on yield at any harvest and increasing the temperature increased yields only at the first harvest. In Vanessa cold storage at 3 °C prior to entry to sprouting temperatures induced an earlier onset of sprout growth than continuous exposure to temperatures conducive to sprout growth. Long sprouting periods produced less sprout growth and at the earliest harvest lower tuber yields than all except the shortest period. Judged from the onset of sprout growth increases in length and temperature of sprouting generally increased tuber yields especially at early harvests. In Pentland Javelin sprout growth was very slow and tuber yields at early harvests decreased at both sprouting temperatures if sprouting began after mid-November. At later harvests effects of both factors were small.

The implications of differences in the effects of sprouting periods according to variety and, in Home Guard, season, are discussed in relation to the provision of the most desirable sprouting environment and to variety testing. The similarity in the effects of lengthening the sprouting period and of increasing the temperature of sprouting suggest that temperature is the major causal factor in sprout growth and its effect on field growth. Sprouting periods may therefore be measured most accurately by accumulated day degrees > 0 °C and a close relationship between such a scale and tuber yields is demonstrated. The relevance of such scales for advice to growers is discussed.

Tuber growth rates for Vanessa and to a lesser extent Home Guard in 1974 were extremely high, in excess of 10 t/ha/week for Vanessa. These high rates were associated with high levels of radiation received by coastal sites in May and June and are discussed in relation to the canopy structure of the varieties.

Eleven single-rearing and 14 twin-rearing Greyface (Border-Leicester × Scottish Blackface) ewes which had previously been individually fed indoors on three nutritional treatments (treatment 1, adequately nourished; treatment 2, moderately undernourished; treatment 3, severely undernourished) during the final 6 weeks of pregnancy, were subsequently grazed with eight non-lactating Greyface ewes on a ryegrass–white clover pasture for the first 14 weeks of lactation.

Herbage organic matter (OM) intakes and milk yields of ewes were measured weekly and the herbage OM intakes of lambs from week 7 of lactation.

Mean daily OM intakes were 36·6 (± 1·09), 38·9 (± 0·99) and 26·4 (± 0·93) g OM/kg body-weight for single- and twin-rearing, and non-lactating ewes respectively. Prepartum nutrition had no effect on intake. Maximum intakes were achieved in week 5 for twin-rearing ewes (53 g OM/kg) and week 4 for single and non-lactating ewes (54 and 38 g OM/kg respectively).

Mean daily weight gains over the period for single-, twin-rearing and non-lactating ewes were 89 (±22·2), 73 (±16·1) and 182 (±22·5)g respectively. There were no differences due to prepartum treatment.

There were significant differences (P < 0·05) in milk production between singleand twin-rearing ewes in the first 5 weeks of lactation. Twin-rearing ewes of prepartum treatment 1 produced consistently more milk in weeks 2, 3 and 4 of lactation, whereas ewes from treatment 3 tended to produce more milk than ewes from the other treatment groups thereafter.

Milk intakes of single lambs were always significantly greater than individual twin lambs, and single lambs ate significantly less grass during the herbage OM intake measurement period from week 7; their growth rates up to week 7 were also significantly greater.

No differences in the intake or growth rate of lambs could be attributed to the prepartum nutritional treatment of their dams.

Ewe maintenance requirements during lactation were estimated to be 242 (± 35·1) kJ ME/kg body weight/day; the efficiency with which ME was used for milk production to be 59%; and the efficiency with which ME was used for body-weight gain, 53%.

Lamb maintenance requirements were estimated to be 427 (± 143) kJ ME/kg W in weeks 1 and 2 of lactation and 287 (± 44·2) kJ/kg from week 7. Efficiency of utilization of energy for body-weight gain in each period was estimated to be 71 and 80% respectively.

The rate of leaf extension in swards of the perennial ryegrass cv. Perma was monitored continuously from March 1976 to September 1977 in Northern Ireland. In this period air temperature and soil water potential were shown to be closely correlated with leaf extension rate. Simple linear expressions are shown to adequately describe the relationship between temperature and leaf extension rate when the year is divided into a winter phase, in which sward growth is very slow, and the remainder of the year in which temperature is high enough to allow significant sward production. Leaf extension growth occurred at all temperatures above freezing point. Soil water potentials of 0·15 MPa are shown to be capable of significantly reducing leaf extension rate. However, the occurrence of such soil water potentials are sufficiently rare in Northern Ireland as to permit prediction of leaf extension rates in perennial ryegrass from simple daily temperature records.

Storage of high moisture grain treated with NaOH in various concentrations and with and without urea showed that while untreated moist grain (17–26% moisture) deteriorated during storage, grain treated with urea and with various concentrations of NaOH had few bacteria and fungal propagules, and was considered safe for feeding. When the grain was treated with NaOH at 35 g/kg air dry weight, there were less than 102·6 bacteria and fungal propagules/g. Similar results were obtained when grain was stored in large batches in an open shed, although at 20 g NaOH/kg grain there was some deterioration after 6 months.

Mouldy grain treated with NaOH showed an immediate decrease in both fungal propagules and bacteria from about 108 to 104/g.

The possibility of using urea to preserve grain was examined in a 5 months storage trial with urea concentrations varying from 0 to 20 g/kg. With 5 g urea/kg grain there was an immediate decrease in the numbers of bacteria and fungal propagules and the results suggest that 10 g/kg would be safe for storage.

The mechanisms of the preservation effects of NaOH and urea are discussed.