Crops of perennial ryegrass and lucerne were each ensiled without additives and after the addition of paraformaldehyde to provide about 0·1, 0·2 or 0·4% HCHO/t crop fresh weight. The ryegrass and lucerne silages were offered ad libitum to sheep in separate experiments of identical design.

All theryegrass silages were well preserved with low pH values, the level of butyric acid was very low and ammonia-N comprised less than 8% of total N. The lucerne silage made without additive had a pH of 5 and acetic acid comprised the major part of the total fermentation acids. Ammonia-N comprised over 12% of total N. All levels of paraformaldehyde addition restricted fermentation in both crops and led to an increase in the proportion of total N which was insoluble in hot water.

Voluntary intake of organic matter (OM) was higher for the lucerne than for the ryegrass silages but digestible organic matter (DOM) intake was higher for the ryegrass. Intakes of OM and DOM were not significantly affected by paraformaldehyde treatment. The addition of paraformaldehyde significantly depressed apparent digestibility of OM and cellulose with the ryegrass but had less effect with the lucerne. Nitrogen digestibility was significantly depressed in both crops at all paraformaldehyde levels. Paraformaldehyde addition resulted in increased faecal N output and decreased urinary N, but retention of N was not significantly affected.

The lack of response in feeding value to paraformaldehyde treatment may have been due to the relatively high intake and N retention of the untreated silages which were fairly well preserved.

Effects of treating wheat straw with caustic soda solution and of providing a cottonseed meal supplement were studied with 40 Friesian heifers (280 kg live weight) in individual pens. Responses were measured in terms of food intake, growth rate and food conversion ratio.

Wheat straw was coarsely-milled and fed ad libitum, untreated (U) or alkali-treated (T); both types of straw were supplemented with urea and minerals. Half the animals on each type of straw were fed 500 g cotton-seed meal (C/day.

Straw intake was higher with T than with U (P < 0·01) and unaffected by the cotton-seed meal supplement, being 4·53, 4·71, 6·58 and 6·56 kg/day on treatments U, UC, T and TC respectively. Alkali treatment and the cotton-seed meal supplement improved live-weight change (P < 0·001), being –6, 189, 334 and 495 g/day respectively. In vivo digestible organic matter in the dry matter, calculated from lignin ratios, was 59, 60, 64 and 64 respectively.

Rumen VFA concentrations were significantly higher, molar proportions of acetic acid lower, propionic and n-butyrie acids higher in animals on T than on U. Plasma urea and rumen ammonia concentrations were lower on treatment T than on U.

It was concluded that wheat straw which is coarsely-milled, NaOH-treated and sprayed with urea and minerals provides sufficient nutrients to allow cattle to grow and that additional gain obtained by feeding cotton-seed meal was predictable in terms of its energy contribution to the diet.

Synthetic SMCO was added to basal diets of either fresh kale or lucerne at the concentrations 0, 0·2, 0·4, 0·8 and 1·6% D.M. and each diet offered ad libitum to groups of four lambs that were individually fed indoors. Within each group, two lambs were of haemoglobin genotype AA and two were AB. Initial live weight (W) was 21 kg and the experiment lasted for 6 weeks.

SMCO supplementation depressed voluntary intake, body growth and wool growth, caused the development of haemolytic anaemia and produced kidney hypertrophy. Effects were much more severe when SMCO was added to a kale than to a lucerne diet, with the lowest SMCO intake of kale-fed lambs (0·3 g/kg W) producing marked detrimental effects whereas the highest SMCO intake of lucerne-fed lambs (0·7 g/kg W) produced only small and transient effects. The intake depressions were evident during the first week of SMCO supplementation and persisted throughout the full 6-week feeding period. Approximately 80 and 65% of the changes in body growth and wool growth could be accounted for by changes in intake, and it was concluded that the most important effect of SMCO in ruminant diets is as an intake depressant.

It is suggested that the greater ratio of soluble to structural carbohydrate in kale (2·3) compared with lucerne (0·9) probably resulted in a microbial population developing in the rumen of kale-fed sheep that could metabolize SMCO to dimethyl disulphide at a faster rate than occurred in the rumen of lucerne-fed sheep. Dimethyl disulphide production is postulated as the cause of both the haemolytic anaemia and appetite depression. Plasma SMCO concentrations did not increase with increasing SMCO intake in sheep fed either diet, indicating that there must have been negligible absorption of this amino acid from tho digestive system.

No haemoglobin C was produced by any of the lambs fed lucerne, and kale-fed lambs produced significant amounts only during weeks 5 and 6, with type AA lambs producing more than type AB lambs. However, there was no difference between AA and AB lambs in rate of decline in total haemoglobin concentration or upon voluntary intake, body growth and wool growth.

Forty pregnant sheep were allocated to four groups and maintained indoors in individual pens on a pelleted diet. During the last 6 weeks of pregnancy and the first 6 weeks of lactation groups were infected daily with 4000 larvae of Ostertagia circumcincta or remained as controls in a cross-over design. Thus groups were either not infected (CC), infected only during pregnancy (IC), during lactation (CI) or during both pregnancy and lactation (II). Food was offered on the basis of body weight at the beginning of pregnancy and lactation. Food intake, body-weight change, faecal egg counts, plasma pepsinogen and milk production were measured weekly, wool growth and fibre diameter during 21-day periods and tensile strength of wool over the whole experimental period.

Eggs were seen in faeces of only three sheep infected during pregnancy, but in all sheep infected during lactation; maximum mean values were 467 ± 144 and 222 ± 58 eggs/g fresh faeces in CI and II sheep, respectively. Pepsinogen concentrations rose after 1 week of infection during pregnancy and lactation; peak values were 868 + 57 and 1104 ± 146 m-u/l, respectively.

Infection reduced food intake by 16% during lactation but had no effect during pregnancy. There were significant interactions between pregnancy and lactational treatments on intake during lactation. Infection during lactation increased bodyweight loss; mean values were 57, 40, 114 and 78 g/day for groups CC, IC, CI and II respectively. Milk production was decreased during weeks 4–6 of lactation, mean values being 1·59 and 1·32 kg/day in control and infected groups, respectively.

Infection reduced wool growth and wool fibre diameter by 20 and 7%, respectively, during the final 3 weeks of infection during lactation. The staple strength of wool grown during the experiment was reduced by 14, 45 and 23% in IC, CI and II groups, respectively. Infection moved the point of greatest wool tenderness from parturition in control sheep to a time during the period of infection, particularly when infection occurred during lactation.

The relationship between rate, spray interval and number of applications of Decis for pest control in cow pea was investigated. In 1978 and 1979, neither the rates nor the interaction effects were significant in grain yield when 12·5 and 25·0g a.i./ha of Decis were applied three times weekly or twice at intervals of 10 or 14 days.

Further trials in 1980 showed that for the contro l of thrips (M. sjostedti), rate, interval and number of applications were significant for samples at 49 days after planting and beyond, suggesting that the residual life of Decis is about 10 days. Three applications were significantly better than two for lowering the population of C. tomentosicollis and the number × interval interaction was also significant. The number, rate and interval were significant without interaction effects for shrivelled pods caused by all hemipteran pests. In all the trials in 1980 and 1981, damage by the pod borer M. testulalis was low. Rate and number × interval interaction were generally significant but no differences were observed in grain yield. However, in 1980 the higher rate and three applications gave better quality crop, resulting from less hemipteran damage.

An analysis of cost–benefit of the trial showed that 12·5 g a.i./ha gave higher returns than 25 g, as did two applications than three, but the trend in the spray interval was less consistent.

Field experiments were conducted at the International Institute for Tropical Agriculture, Ibadan, Nigeria, during two cropping seasons, with two cultivars of climbing cow peas (Vigna unguiculata (L.) Walp. subspecies sesquipedalis) cv. FARV-13 and TVU-1209. The work investigated their yields when intercropped with maize, which served as live support.

The results showed that there were varietal differences in the cow-pea response to method of planting. Under the intercropped systems, highest dry-matter yield was obtained when TVU-1209 was planted on the same hill with maize while similar yields were obtained with FARV-13 planted in alternate hills with maize. TVU-1209 did not increase maize lodging except when planted in alternate hills with maize, but FARV-13 significantly increased maize lodging under all planting methods. Consequently, FARV-13 reduced maize yields more than TVU-1209.

Neither pod length nor pod weight was affected by the planting. Highest yields from both cow pea and maize combined were realized from TVU-1209 planted between rows of maize. The yield of FARV-13 cow pea intercropped with maize did not show any advantage due to intercropping over sole crop of each.

Sweating rates were analysed in relation to rectal temperatures of cattle to yield a measure of sweating response within and between animals. The measurements, performed over 36 days, were done in a natural radiant environment on six steers in each of three breeds, Brahman (B), Brahman × Hereford–Shorthorn cross-breds (BX), and Shorthorn (S). Each steer was recorded for 30 min on six occasions randomly distributed among 6 h between 08.00 and 13.00 h, and on six occasions between 11.00 and 16.00 h, all on different days. Sweating response, e.g. the linear slope of the relationship between sweat rate and rectal temperature, was greater for B (294 g/m2. h/°C) than for BX (146 g/m2.h/°C) or S (194 g/m2.h/°C) which did not differ; this helped to explain why the range and mean rectal temperature in B were lower and little affected by environmental heat. Curvilinear models of the sweating response indicated that in the environmental conditions of this study, the limit of sweating for B and BX was not reached, while for S, the sweating response approached a plateau. Between animals, the relationship of sweating response to mean rectal temperature was negative (P < 0·01) and its relationship to the time spent in the sun at pasture positive (P < 0·025). Thus this measure of sweating response was a good indicator of thermoregulatory ability of the cattle. However, the sweating response of the steers did not relate to their grazing time or growth. The reasons for this are discussed. Finally, the sweating response was found to be negatively correlated with metabolic rate between animals within breeds (P < 0·01) and this suggested that it may be difficult to combine the desirable traits of good heat adaptation and high metabolic potential in cattle.

In field experiments at the International Institute of Tropical Agriculture in Nigeria, two cow-pea cultivars, TVU-1209 and FARV-13 and a composite maize cultivar were intercropped at plant densities of 10000, 20000, 30000 and 40000 plants/ha in a split-plot design. There were four replications of each density. Results showed that increasing cow-pea plant density increased the number of days to flowering but decreased the numbers of branches and of leaves per plant in both monoculture and mixture. Different varietal responses to plant density were observed for other growth measurements. While TVU-1209 yielded the highest dry matter at 20000 plants/ha in monoculture and mixture, FARV-13 did so at 40000 plants/ha in monoculture and at 20000 in mixture. Some yield components decreased while others were unaffected by increasing plant density. Similar response pattern was observed for maize. Both leaf area index and light interception were greater in FARV-13 than in TVU-1209.

Data collected from 1968 to 1981 were used to study the effects of annual precipitation and its distribution on grain yield of three barley and six wheat varieties from 19–47 environments.

The percentage of the variation in grain yield explained by annual precipitation varied with variety and species (5–31% in barley and 31–79% in wheat). The distribution of precipitation was the major factor affecting grain yield, although it varied with variety, and explained 72–92% of the variation in barley and from 75 to 98% in wheat.

Only 33 of the 144 simple correlation coefficients between grain yield and precipitation during each of the 16 fortnightly periods were significant. The expected average effect on yield due to additional precipitation above the mean showed positive effects in barley during the presowing and heading to flowering periods; no consistent trend was found in the wheat.

Improved agronomic practices could alleviate the adverse effects of the low and unevenly distributed precipitation by reducing losses and increasing storage of water in the soil. Breeding could contribute greatly towards high and stable yields in drylands.

Data from between 742 and 894 carcasses of hogs and of gilts of a British Landrace line of pigs selected for lean percentage were subjected to a heritability and genetic correlation analysis and to a multivariate regression analysis of phenotypic correlations.

Although overall fatness was the most important component of carcass profitability, other components relating to carcass conformation and muscle to bone ratio remained important, particularly in gilts.

Genetic correlation of backfat thickness with carcass value was low in hogs (–0·39) and exceedingly so in gilts (–0·13). Although genetic correlations of lean percentage with carcass value were high (0·80 in hogs, 0·77 in gilts) they were no larger than those relating yield of trimmed and boned joints to carcass value, which varied between 0·70 and 0·79.

It is concluded that, with skilled butchers, joint yields as a selection criterion for carcass value are preferable to backfat thickness and as efficient as, and cheaper than, dissection.

The phosphorus status of 58 soil samples representing 15 soil series and four soil Orders (Ultisol, Entisol, Alfisol and Oxisol) in the major coconut-growing regions of Sri Lanka was evaluated by determining the available P extracted by the methods of Olsen, Bray & Kurtz No. 1, Bray & Kurtz No. 2 and NH4OAc (pH 4·8) and the various P forms. Total P in the soils ranged from 37 to 338 mg/kg with organic P and active P constituting only about 20 and 50% of the total P respectively. In general the sandy soils of the Entisols and Oxisols had lower total and organic P but higher active and available P than the rest. The relative abundance of the various inorganic P forms was generally in the decreasing order of inactive P, Fe-P, Al-P and Ca-P. Al-P and Ca-P were positively correlated with percentage sand and negatively correlated with percentage silt and percentage clay whereas total P and organic P had the opposite trend. Available P extracted by the four methods was very low in almost all soils except some of the sandy soils (Entisols) which had marginal to moderate P contents. They were positively correlated with Al-P, Ca-P, percentage sand and negatively correlated with percentages of silt, clay and organic carbon.

Phosphorus concentrations (0·074–0·116%) in the 14th leaf of coconut at the soil sites were all lower than the critical leaf-P concentration (0·120%). Leaf-P correlations with Bray & Kurtz No. 2-P and NH40Ac-P were significant (P < 0·05) and with Al-P and Ca-P were close to significant.

The study revealed that the coconut-growing soils of Sri Lanka were deficient in total as well as the active and available forms of P except perhaps some of the sandy soils of the Entisol. This was confirmed by coconut leaf P analysis.

Thiaminases from different sources exhibit varied responses to change in pH and to differing activators, cosubstrates and inhibitors. These properties are used in an attempt to characterize the extracellular thiaminases of 17 strains of Bacillus spp. isolated from the rumen contents of animals affected with cerebrocortical necrosis and to compare these with the endogenous thiaminase present in the rumen content of such animals and with other known thiaminase-producing bacteria. Statistical analysis of the results obtained using different activators classified the isolates into two main groups corresponding to the presence of thiaminase I or thiaminase II. The pH characteristics of the rumen content enzyme differed significantly from any of the bacterial isolates examined.

The Sudan Desert sheep are well adapted to the hot tropical climate, are thirst tolerant and can travel for long distances under nomadic conditions in search of water and pasturage. The ejaculate volume, sperm cell concentration, total number of sperms per ejaculate, motility, percentage live and percentage abnormal spermatozoa and the fructolytic index of semen were estimated throughout the hot dry summer (March-June), hot rainy season (July-October) and the winter (November-February). The semen characteristics were normal for about 7 months (May-November) covering the last 2 months in summer, the whole rainy season and the 1st month in winter and deteriorated slightly during the rest of the winter and early summer. Thus the Sudan Desert rams appear to be able to breed throughout the year and their spermatogenesis is not seriously affected by high environmental temperatures.

A study using 1150 lambs to estimate genetic and phenotypic parameters of some weight and fleece traits was carried out on coarse-wool Barki sheep. The weight traits were birth, weaning, yearling weights and daily gains whereas fleece traits included kemp score, staple length and greasy-fleece weight.

Heritability estimates of weight traits were within the range 0·25–0·30. Those of fleece traits were 0·16, 0·21 and 0·43. The repeatability estimates of fleece traits were 0·18, 0·38 and 0·53 for staple length, greasy-fleece weight and kemp score respectively.

Phenotypic correlations between body weight and fleece traits were mostly positive. Genetic correlations between greasy-fleece weight and body weights were mostly positive and of medium values. Those between kemp score and body weights were mostly negative, ranging from medium-high to high.

Pigs from different companies (source populations) in years 3–5 of the Meat and Livestock Commission's Commercial Pig Evaluation were characterized in terms of eight production characteristics and grading measurements using canonical variates analysis in a multivariate general linear model. For pigs fed to a restricted scale, the first canonical variate was strongly associated with fat thickness measurements and the efficiency with which feed was converted into live-weight gain (FCR); the second canonical variate was associated with killing-out percentage. For pigs fed ad libitum, a discriminant variate formed from the sum of the first two canonical variates was strongly associated with P2 and loin fat thickness measurements and FCR, and a discriminant variate formed from the difference of the first two canonical variates was strongly associated with killing out, length and shoulder fat thickness. The first three canonical variates accounted for 88 and 90% of the variation between source populations for restricted and ad-libitum fed pigs respectively. A graphical display of the source populations indicated that there were six to eight groupings depending on feeding regimen.

In principal component analyses of residual variation, the first principal component on both feeding regimens was strongly associated with fat thickness measurements. The first three principal components accounted for 91 and 90% respectively of the variation for restricted and ad-libitum fed pigs.

Observations were made in three successive years on the dentition of Scottish Blackface ewes of 1½–4½ years old in a large hill flock in southern Scotland.

The number of permanent incisor teeth was not a reliable guide to age, since at each age there was variation about the modal number. The length of the central permanent incisors increased slightly with age, and associated with this there was a slight forward movement in the position at which these teeth occluded with the dental pad. The modal position was 1 mm behind the anterior point of the dental pad of gum. About 1·5 % of the observations had bite positions deviating by 5 mm or more from the mode.

Keeping the females during their first winter on low-ground pasture instead of the hill led to earlier eruption and slightly longer central incisors, but had little effect on bite position.

The heritability of the number of incisors present at any one age was estimated to be 0·39 ± 0·11 by paternal half-sib correlation and 0·80 ± 0·27 by daughter-dam regression. Estimates of h2 for incisor length were less than half these values and those for the measure of bite position were very small and not significantly different from zero.

For the ages up to 3½ years old, there were low but statistically significant correlations of number of incisors with ewe live weight (0·1–0·2) and fleece weight (around 0·1), incisor length with fleece weight (around 0·1) and at 1½ years old only between the bite measure and both weights (0·1). Weight of lamb weaned by the ewe was uncorrelated with these dental traits.

It is concluded that in this flock, culling on the dental characters studied would not have improved performance, and selection would not change the position of the bite.

An analysis of pig carcass composition was carried out, using data for 11 genetic source populations in the Meat and Livestock Commission's Commercial Pig Evaluation (CPE). The data were from years 3–5 of CPE and a total of 720 carcasses were involved. Weights of dissected tissues and parts were considered simultaneously, and the effects of growth, source population, sex, feeding regimen and time period were incorporated into an integrated model, the multivariate allometric development model.

Canonical variates were constructed for each of the classifying factors except time period, and the residual variation in carcass composition was analysed by principal component analysis. The first canonical variate for source populations was interpreted as a tissue distribution characteristic associated with the distribution of lean between joints in the dorso-cranial and ventro-caudal regions of the carcass. It accounted for 39% of the variation between source populations. The second canonical variate was associated with the ratio of subcutaneous fat to lean in the carcass, and accounted for 20% of the variation between source populations. The results explain the bias found in predicting the proportion of lean tissue in a carcass from subcutaneous fat thickness (P2).

In a graphical display of differences between source populations, nine were shown to be distinct, with only two intermediate and not clearly differentiated from some others. The interpretation of canonical variates and the relative positions of the populations were closely related to those obtained from the analysis of production and grading characteristics in the first paper of the series.

Some androgen-dependent constituents of seminal plasma of Sudan Desert rams were measured during the hot dry summer, the hot rainy season and the winter under tropical conditions in the Sudan. Higher concentrations of both fructose and citric acid were obtained between July and October during the rainy season and low values between January and April during winter, with marked monthly and seasonal variation in both characters. Considerable monthly variation in the hydrogen-ion concentration of semen was obtained with lower values between August and January and higher values between February and July. The androgenic status of the animals appears not to be decreased during the hot weather, but no explanation can be offered for the decrease during the winter.

Six varieties of winter barley were grown during the years 1979, 1980 and 1981 in Granada (southern Spain). Grain yield variation in the 3 years studied was a function of the pre-anthesis period (especially as a determinant of number of ears/m2). In comparison leaf area duration and grain: leaf ratio from anthesis to ripening had far less influence on grain yield variation. Though these findings contrast with the generally accepted view, they can be explained by environmental conditions prevailing in southern Spain during grain filling.

The effects of virea and urea plus sodium sulphate on the production of microbial protein were studied in sheep fitted with rumen fistulae and re-entrant cannulae in the proximal duodenum and terminal ileum. Diets containing a high proportion (0·68–0·72) of sodium hydroxide-treated barley straw supplemented with starch, glucose and solka floe were fed at hourly intervals to the sheep at 830–870 g dry matter/24 h.

The addition of the urea and urea plus sulphate supplements, although inducing a stepwise reduction in overall digestibility of OM, resulted in increased microbial protein synthesis in the rumen, which was reflected in increased quantities of amino acid nitrogen entering the small intestine (8–38, 12–03 and 17–84 g of total amino acid nitrogen (TAA-N)/24h respectively). The efficiency of microbial protein production (g bacterial TAA-N/kg OM actually digested in the rumen) was significantly increased by the addition of urea and still further by additions of urea plus SO4-S (11·1, 20·2 and 29·6 grespectively).

Digestibilities of the individual amino acids in the small intestine were very similar on each dietary treatment. Apparent digestibilities of total amino acid-N within the small intestine (based on amounts entering the small intestine) were 0·623, 0·672 and 0·688 on the basal diet, basal diet plus urea and basal diet plus urea and S respectively.

The proportions of cyst(e)ine-S in rumen bacteria synthesized from the rumen sulphide pool were 0088, 0·075 and 0·669 on the basal diet, basal diet plus urea and basal diet plus urea and S respectively. The data confirm appreciable recycling of S into the rumen.