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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The development of the maxillary teeth in cattle was studied by recording eruption into the oral cavity and by radiographic examination following bisection of the skull. Observations of second molar intra-oral eruption showed that varying stages were seen at different ages. Radiography of the teeth allowed determination of the degree of crown and tooth development in the permanent premolar and molar teeth as well as stages of temporary premolar tooth resorption. Radiographic inspection showed that in the same animal all the permanent maxillary cheek teeth except the first premolar were less well developed than their mandibular counterparts. It was suggested that the intra-oral eruption of the second maxillary molar and radiography of the maxillary teeth provided a better method of age estimation in cattle than the traditional one of examining the intra-oral eruption of the incisor and canine teeth.

Five agricultural by-products, maize stover and cobs, wheat straw, grape marc and sunflower husks, were treated with alkaline reagents under various conditions.

Maize stover and wheat straw reacted quickly with both sodium hydroxide applied at a level of 4 g NaOH/100 g dry residue and a mixture of calcium and sodium hydroxides (1:1), which led to changes in chemical composition and increases in digestibility. However, ensilage of the treated product at about 37% dry matter (D.M.) was not successful.

When dried grape marc was treated with sodium hydroxide (4·3 g NaOH/100 g dry residue) apparent lignin content increased, although other changes in composition and digestibility were similar to the above. Nevertheless, digestibility remained low. Moreover, when previously ground marc was treated in the same way lignin and cellulose fractions increased markedly while digestibility decreased.

Treatment of maize cobs with increasing amounts of sodium hydroxide (2·1–4·2 g/100 g dry residue) at 80% D.M. gave progressively more favourable results, although no improvement in digestibility was noted when half the sodium hydroxide was replaced by calcium hydroxide. Similar positive results were obtained under industrial conditions at application rates of 3·2 and 4·5 g sodium hydroxide per 100 g dry residue. Pelleting the product led to a further increase in digestibility.

Sunflower husks also showed a decrease in hemicellulose content and increases in digestibility and volatile acid content after treatment with 4·4 g NaOH/100 g dry residvie under industrial conditions. Lignin content was unchanged. The pelleted products (about 80% D.M.) were stable for more than 6 months when stored in paper sacks.

Except with grape marc loss of hemicellulose provided a general indication of the success of alkali treatment, although correlation with increased digestibility did not reach statistical significance (r = 0·34). Volatile acid production and alterations in lignin content were not suitable as general indicators.

In general, alkali treatment of the examined materials improved digestibility, although the products with a high water content were subject to undesirable fermentative changes during storage and therefore should be used within a few days.

Three experiments examined the effects on seedling emergence and seedling weight of covering pelleted, natural and pre-germinated seeds of the variety Pennlake with soil and other media.

Covering seeds with a peat-vermiculite mix gave significantly greater, earlier and more uniform emergence and seedlings with a lower coefficient of variation (c.v.) of weight than covering with soil.

Seedlings from pre-germinated seeds emerged more rapidly than those from natural and pelleted seeds and tended to be heavier when harvested 24 or 41 days after emergence. However, natural seeds consistently gave more uniform emergence than the other seed treatments and the lowest c.v. of seedling weight.

The present study was carried out on adult fleeces, of Merino, coarse wool Barki and five of their crosses, of known birthcoats. The adult fleece traits studied were clean fleece weight, mean fibre diameter and its variability and mean staple length and its variability.

Birthcoat-adult fleece relationship was dependent on the breed studied. In Barki, plateau array in the birthcoat developed to adult fleeces with higher values of mean fibre diameter and its variability, mean staple length and clean fleece weight than those with saddle array. In ⅝ Merino there was a gradient in staple length, running from plateau, via saddle, to ravine, with higher values of the coarser arrays. Differences occurred in variability of fibre diameter between plateau and saddle arrays in ⅜ and ⅝ Merino and between saddle and ravine in ½, ⅝ and ¾ Merino.

Differences occurred where birthcoats, with plateau array with precipice, in the curly-tip group, grew into adult fleeces with longer mean staple than those with transition in Barki sheep. In the other breed groups differences observed in saddle array, with different features, precipice or transition, at the birthcoat level, did not contribute differences in their adult fleeces.

Selection of Barki lambs with plateau fibre type array in their birthcoats would result in higher clean adult fleece weights that have coarser fibre diameter, with higher variability, and longer staple than those with saddle array. Within saddle array, selection of those with reduced SK% would develop into adult fleeces with higher clean fleece weight and those with reduced CT% would grow into adult fleeces with finer diameter.

Selection of lambs that have birthcoat ravine array in f, ⅜, ½, ⅝ and ¾ Merino would reduce the within-staple variability in their adult fleece fibre diameter.

The design and analysis of an experiment to compare the yield of wheat grown continuously with that of wheat grown in two phases of a four-course rotation is described and the results discussed. A method of analysis which avoids making assumptions about the covariance structure of the errors derived from repeated observations on the same plots, which could be appropriate to other sorts of rotation experiments, is given.

There were no differences between yields of the first and second wheat crops which followed oats after beans in a four-course rotation, but the average of these two crops was 0·75 t/ha greater than the yield of wheat grown continuously. The response to N was the same in the two systems of cropping. The only yield component affected by the system of cropping was grain mass.

The performance of Welsh Mountain ewes and their single Clun-cross lambs on swards of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.) and timothy (Phleum pratense L.) was studied over 3 years (1975–1977) at a site 305 m O.D. in mid-Wales. Under a rotational grazing regime at a fixed stocking rate of 25 ewes and lambs/ha, mean daily lamb live-weight gain over the 84 days experimental period from early May to late July was 24 g higher on timothy than on perennial ryegrass and tall fescue and 35 g higher than on cocksfoot. Averaged for the 3 years the mean daily lamb live-weight gains were 194, 170, 170 and 159 g on timothy, perennial ryegrass, tall fescue and cocksfoot respectively. There were, however, marked interactions with years.

Ewe live-weight change varied considerably between grasses and years with cocksfoot poorer than timothy and perennial ryegrass. Mean ewe live-weight change ranged from an overall loss of 39 g/day in 1975 to a gain of 34 g/day in 1977.

Differences detected in animal performance between the four grass species altered during the 84 days of the experiment. Timothy and to a lesser extent tall fescue produced better animal performance early in the season whereas perennial ryegrass came into prominence during July.

The results are discussed in relation to the present and potential use of the grass species under upland conditions.

Herbage characteristics of perennial ryegrass (Lolium perenne L.), cocksfoot (Dactylis glomerata L.), tall fescue (Festuca arundinacea Schreb.) and timothy (Phleum pratense L.) pastures were obtained whilst rotationally grazed by ewes and their single lambs at a fixed stocking rate of 25/ha on an upland site (305 m O.D.) in mid-Wales. Drymatter production of cocksfoot averaged 32·1 kg/ha/day over the 3-year duration of the trial (1975·7) and was 13·3 kg/ha/day lower than that of the other three grass species. This resulted in a 8 kg/ha/day reduction in dry-matter intake on cocksfoot; this was significantly lower (P < 0·05) than that achieved on the other grasses, which were similar to one another around 36 kg/ha/day.

In vitro digestibility of the herbage ranked in the order perennial ryegrass > timothy = cocksfoot > tall fescue. Intake of digestible organic matter (DOMI) was lower on cocksfoot than on perennial ryegrass and timothy. Differences were also detected in crude protein, water-soluble carbohydrates and sodium composition between species.

Dry-matter intake was positively correlated with herbage growth rates (r = 0·95, P < 0·001) but not to digestibility of herbage on offer (r = 0·18). Both ewe and lamb live-weight gains were positively related to intake of dry matter and DOMI.

Reference is made to comparative yield data between the grasses obtained under cutting trials. In the 2nd and 3rd harvest years (1967–1967) growth rates in the grazing experiment were 76, 61, 81 and 80% of the 66·2, 66·7, 67·8 and 65·0 kg D.M./ha/day obtained under a cutting regime on perennial ryegrass, cocksfoot, tall fescue and timothy swards respectively. This illustrates the danger involved in assessing the potential of grasses based on such information.

The results are discussed in relation to the value of the species for use under grazing in the uplands.