A total of 187 animals (mainly Friesian dairy heifers) on nine farms in Wharfedale, Nidderdale, Calderdale and the Vale of York were weighed, condition scored and blood sampled on three occasions during the grazing season 1977. On each site, half of the animals each received two injections of a Cu preparation (200 mg Cu total), one in May and one in July. Herbage samples were taken in May, July and September.

Despite the fact that many animals started the experiment with low blood total Cu concentrations, growth rates during the experimental period were all satisfactory (lowest mean value 0·70 kg/day) with a significant increase due to treatment being observed on only one site. The Cu treatment, however, had a significant effect on blood and plasma total Cu values with the treatment either increasing the level to normal in animals which had started with low values, or maintaining the value in animals starting with near normal concentrations. On certain sites, animals in the untreated group ended the experiment with very low blood and plasma total Cu values (0·02–0·03 mg/100 ml). To prevent the possibility of a Co deficiency on some sites interfering with the experiment, all animals received a Co bullet initially. Despite these, concentrations of vitamin B12 in serum samples taken during and at the end of the experiment were low by present interpretation. This suggests either that Co bullets were an ineffective treatment or that the present interpretation of serum vitamin B12 concentration in bovines is incorrect.

The calculated concentrations of available Cu estimated from herbage analysis indicated that on most sites the value was below the optimum for the growing cattle under study. The results of the experiment suggest that even when blood Cu values and herbage available Cu values are low a growth response to Cu injections may not occur over the course of a grazing season.

Horses fed various species of tropical grass hays containing more than 0·5% total oxalate were in negative calcium balance of up to 41 mg/kg live weight/day in mineral balance experiments. In most cases, a concurrent negative phosphorus balance of up to 22 mg/kg live weight/day was measured. These results were in contrast to those obtained when grass hays low in oxalate were fed. Magnesium balance was little affected by oxalate. The degree of negative calcium balance could not be reconciled with total calcium and total oxalate concentrations, but could be explained if a major fraction of calcium in the grasses was in the form of calcium oxalate crystals and if calcium in this form was unavailable for absorption. It is suggested that soluble oxalates exert a variable but smaller effect on absorption of the remaining calcium fraction of the grasses. In general, nutritional secondary hyperparathyroidism may occur in horses grazed solely on pastures in which calcium to oxalate ratios are less than 0·5, such ratios usually being found in grasses containing more than 0·5% total oxalate.

Body composition of 324 steers from Angus dams by ten different sire breeds was compared at constant age. Progeny of the large European breeds and the Friesian attained heavier fasted live weights and carcass weights than the local Angus and Hereford breeds. Friesian cross-breds had the lowest dressing percentage. The Blonde d'Aquitaine and Limousin crosses had the lightest bone weights and this was reflected in high meat yields. The European breeds had the leanest carcasses, the traditional beef breeds the heaviest subcutaneous fat weights and the dairy breeds the heaviest internal fat weights. The results are discussed in relation to overseas findings.

Selections for high (H) and low (L) number of ears were made from crosses between three pairs of winter wheat varieties. By the F5 generation there were consistent, heritable differences between H and L selections in each cross. In an irrigated trial the H lines outyielded the L lines even in one experiment where compensatory increases occurred in the weight of grain per ear of the L lines. Drought for the 5 weeks before an thesis reduced the final number of ears of the H lines by 14% but did not affect the final number of ears of the L lines. This reduction in the final number of ears of H lines resulted in them being outyielded by L lines by 8%. Drought from anthesis to maturity did not significantly reduce grain yields of either H or L lines below their values under full irrigation.

When fully irrigated, the evapotranspiration of H and L lines from 1 April until maturity was approximately 360 mm. The drought before anthesis reduced water use to about 320 mm, there being no difference between selections in total water use by the crops during this period. However, the L lines extracted significantly more water from the soil below a depth of 0.9 m during this drought than the H lines, and this appeared to make the L lines less susceptible to drought at this stage. Water use by the crop during the late drought could not be reliably estimated because by this time water was being extracted from below the level of the neutron probe access tubes.

It is concluded that in an environment where a pre-anthesis drought is unlikely to occur, varieties with high ear-bearing capacity may give the best yields. Selection for types showing a limited tillering capacity may prove to be an effective compromise in regions with erratic rainfall where pre-anthesis droughts can occur.

A sheep-feeding experiment was carried out to assess the nutritional value of algae meal as a protein supplement in ruminant diets. The algae, mainly Chlorella, were grown in sewage ponds, harvested by flocculation with alumina (Al2(SO4)3.18H2O), and then drum-dried. Eight young rams, divided into two equal groups, were offered a basal concentrated diet, to which algae meal or soya-bean meal (SBM) was added to contribute 50% of the dietary nitrogen (N).

The digestibility values of dry matter (D.M.) were 69·3 and 79·3%, and those of organic matter (OM) were 75·3 and 82·2% for the algae diet and the SBM diet, respectively.

Nitrogen digestibility of the algae diet was 16% lower than that of the SBM diet and the calculated value of N digestibility in algae meal was 61·7%. However, there was no difference between treatments in the daily amount of retained-N or in the proportion of digested N which was retained in the body.

The algae meal contained 5·7% aluminium. This was probably the reason for the much lower P absorption in the algae diet (6·67%) as compared with the SBM diet (29·5%).

Ammonia-N concentration was lower and total volatile fatty acids (VFA) concentration was higher in the rumen of the algae diet-fed sheep. However, the VFA profile was similar for both diets.

Sewage-grown algae could perhaps be used as a protein supplement for ruminants, provided that the harvesting technology is directed to produce a low-mineral, low-aluminium, young biomass, which would be highly digestible and would not interfere with P absorption.

The CO2 exchange of leaves, pods and peduncles was measured in cowpea crops grown at Ibadan, Nigeria, using a portable infra-red gas analysis system. Most leaves had maximum rates of photosynthesis (Pm) of about 1·4 mg CO2/m2/sec and maintained this value for 20 days from full expansion. Early leaves had slightly slower rates. Pm decreased when leaf temperature exceeded 35 °C. The maximum efficiency of photosynthesis, ɛm, was about 2 g CO2/E (0·045 mol CO2/E). ɛmdecreased with temperature for leaves, but increased for pods. The latter response probably results from the effect of the high CO2 concentrations within the pod on the ribulose disphosphate carboxylation reaction. Water shortage reduced Pm but not ɛm. Pods and peduncles had a slightly negative CO2 exchange rate at light saturation but this was considerably less than the rate of CO2 evolution in the dark.

Six species and subspecies of rats and mice, Arvicanthis niloticus, Rattus norvegicus, R. rattus frugivorus, R. rattus alexandrinus, R. rattus rattus, and Mus musculus, were found associated with cotton, wheat, maize, sugar-cane, vegetables, fruit and berseem in the vicinity of Alexandria, Egypt. A. niloticus comprised 42·2% of all species collected. Maize, wheat, cotton and berseem were infested most. The lowest infestation was recorded in the fruit fields. Infestation in sugar-cane and vegetables was intermediate. R. norvegicus, M. musculus, R. rattus frugivorus, R. rattus alexandrinus and it. rattus rattusformed 23·9, 16·7, 10·4, 4·2 and 2·7% of the species collected respectively. Of the seven crops investigated, only two (cotton, wheat) were not infested with R. rattus rattus, but all were plagued with some species of rodents. The abundance of these rodents in fields seemed to be positively correlated with temperature and relative humidity. Winter represents a definite off-season for all species recorded.

Six species of fleas (Xenopsylla cheopis, Nosopsyllus fasciatus, Ctenocephalides felis felis, Leptopsylla segnis, Pulex irritans and Echidnophaga gallinacea), three of sucking lice (Polyplax abyssinica, P. spinulosa and Hoplopleura capitosa), five of parasitic mites (Ornithonyssus bacoti, Laelaps echidnina, L. keegani, Androlaelaps zulu and Haemolaelaps sp.) and the tick Rhipicephalus sanguineus sanguineus were recovered from the rodents. Fleas (especially X. cheopis) and lice generally showed a certain degree of host specificity. A close relationship has been shown to exist between the abundance of fleas and lice and the abundance of some rodent hosts and climate. However, no definite host specificity or relation to climate was shown by infestation with mite species. Only B. sanguineus sanguinetie was recovered from S. rattus frugivorus during July, October and December; from R. rattus alexandrinus during November; and from R. rattus rattus during September. Its rate of infestation did not exceed one specimen per rodent host.

The response of winter wheat cv. Maris Huntsman to waterlogging was studied in two experiments in soil columns outdoors. Winter waterlogging treatments increased nodal root production and the proportion of aerenchyma within roots, but caused chlorosis and premature senescence of leaves, and decreased tillering. For all treatments, grain losses were much less than expected from the extent of tiller loss in winter; losses after single waterlogging events ranged from 2% (after 47 days with the water-table at 5 cm) to 16% (after 80 days with the water-table at the soil surface). Yield losses after three waterloggings at the seedling, tillering and stem elongation stages of growth were additive, and totalled 19%. In many treatments, grain loss was associated with lighter individual grain weights, suggesting that the size of the root system or efficiency of water and nutrient uptake by roots at the later stages of growth may have been less after earlier waterlogging. The importance of nitrogen fertilizer in maintaining a satisfactory plant nitrogen status was shown when nitrogen was with held before a 3-week waterlogging treatment during stem elongation; tiller and floret survival was subsequently greatly restricted and grain yields decreased 22% below those of plants waterlogged at the same stage of growth but supplied with nitrogen.

DNA, RNA and protein concentrations, cathepsin D activity and tritiated thymidine incorporation into DNA were measured in selected muscles from newborn to 7-day-old ‘splayleg’ piglets. The results indicated that the pattern of development differed considerably from that observed in muscle from normal piglets, and the range of results was greater both within and between affected animals. The most striking difference between muscle from normal and ‘splayleg’ piglets was in the incorporation of tritiated thymidine, which was lower in the latter from 3 to 6 days of age, indicating that the number of cells undergoing mitosis may have been reduced. It is suggested that this could have a severe effect on future muscle growth especially if satellite cells are affected.

A series of experiments investigated mineral supplements for the correction of negative calcium and phosphorus balances in horses fed tropical grass hays containing more than 0·5% total oxalate.

A daily supplement of a soluble calcium source was retained with an efficiency of 60% implying no interference with calcium absorption from supplements by oxalate or other factors in the hays.

The palatability of limestone, rock phosphate, dicalcium phosphate, a limestone and dicalcium phosphate mixture and mono-ammonium phosphate was tested with a view to providing a supplement once weekly. With the exception of the latter, all were consumed readily when mixed with 50–60 % molasses (w/w) and hourly intakes of 200 g calcium and 50 g phosphorus were recorded.

In balance trials using horses fed tropical grass hays, 1 kg of either rock phosphate, or a mixture of limestone and dicalcium phosphate (1:2, w/w), each mixed with 1·5 kg molasses, was fed on the 8th day of a 14-day balance trial. The retention of calcium from the supplements ranged from 19 to 41% and that of phosphorus from 22 to 42%. The passage time for unabsorbed minerals was about 4 days. This amount of supplementation can accommodate calcium and phosphorus losses of at least 20 and 10 mg/kg live weight/day respectively. A supplement of 1 kg limestone overcame a negative calcium balance of 20 mg/kg live weight/day but did not overcome a negative phosphorus balance.

A survey of 46 vineyards was conducted to determine whether some nutritional disorder was the cause of declining yields. The surface soils, in general, are alkaline, calcareous, medium to high in organic matter, light in texture and sufficient in available micronutrients except B. Petiole analysis indicated a deficiency of Zn, Fe, Mn, B and Cu in 70, 52, 37, 20 and 13% as well as an excess of P and K in 35 and 93% of the vineyards respectively.

Significant negative correlations of P with Fe and Mn and that of K with Zn showed that the lack of Fe, Mn and Zn might have been induced by excessive application of P and K fertilizers. Poor correlations between the DTPA-soluble concentrations of Cu, Fe, Mn and B in the soils and those in the petioles suggested the nutrient status of surface soils to be of little value in the nutrition of grape vines or that the petiole may not be the best tissue for this purpose.

Studies on the effect of body weight at calving on body-weight losses during early lactation and the post-partum reproductive performance of large, medium and small buffaloes revealed that the large buffaloes (weighing more than 550 kg at calving) lost most weight (45·9 kg) and the small buffaloes (weighing less than 475 kg at calving) least weight (4·9 kg) during the first 5 months of lactation. The body-weight loss was maximal in the 1st month of lactation. The reproductive performance (measured as conception rate, number of services per conception and service period) of small buffaloes was significantly (P < 0·05) better than the large buffaloes. These results indicate that body–weight losses during early lactation are affected by the body weight at calving and these losses play an important role in influencing the post-partum reproductive performance. It is therefore suggested that, to improve the reproductive performance, the feeding regimen of buffaloes during pregnancy and after calving should be such that body-weight losses after calving are small.

Five experiments, involving 37 varieties, were carried out over three seasons to estimate the increase in yield potential in spring barley achieved by plant breeding during the last 100 years. Most of the important spring barley varieties grown in Britain between 1880 and 1980 were represented. In three experiments disease was controlled by a fungicide while in the other two experiments fungicide application was a main treatment. To prevent yield loss due to lodging, plants were supported as a main treatment in two trials.

In all experiments most of the modern varieties yielded more than the older ones. The genetic gain in yield was 0·39% per year during the 100-year period and 0·84% per year between 1953 and 1980.

Modern varieties had higher grain yields, shorter straw, and higher harvest index denned as the proportion of grain dry weight to total above-ground dry weight; more of the tillers they produced survived to give ears. There was a weak association between biological yield (total above-ground dry weight) and grain yield.

It is suggested that although much of the improvement in yield described here could be attributed to increased harvest index, the scope for further improvement in this character may be limited. Further yield improvements might be achieved by combining high biological yield with high harvest index.

Field experiments were conducted for three seasons, 1971–2, 1972–3 and 1973–4 to study the effects of nitrogen fertilizer and seed rate and their interactions on grain yield and its components and attributes of growth of two wheat varieties, Giza 155 and Mexipak. The semi-dwarf Mexipak was found to be more responsive to nitrogen application than the taller Giza 155 in a number of aspects, namely, grain yield per unit area of land, the number and weight of grains per ear, the dry weight per ear and dry weight of ears/m2. The numbers of spikelets and grains per ear of both varieties decreased linearly with an increase in seed rate. The 1000-grain weight was not affected in both varieties by either seed rate or N fertilizer.

Variety × nitrogen, variety × seed rate and nitrogen × seed rate interactions were significant; the variety × nitrogen × seed rate interactions were not significant. Mexipak was found to have a definite optimum seed rate of 192 kg/ha at an optimum N level of 129kgN/ha for maximum grain yield. Giza 155 was less responsive to changes in seed rate and therefore its optimum seed rate was not as definite as that for Mexipak. Evidence presented here suggests that wheat varieties of different growth habits grown in the Sudan should receive differential treatments when the policies of setting optimum seed rates and nitrogen fertilizer rates are considered.

Grain yield of both varieties was positively correlated with total dry weight of shoot at heading.

The pattern, production and survival of tillers was studied in two spring wheat varieties in field and pot experiments for two seasons.

The time-trend of tillering was such that tiller production reached a peak well before ear emergence, then death reduced the number of vegetative shoots to a level determined by seed rate (in the field) and nitrogen level (in field and pot experiments), and thereafter the number of live shoots remained more or less constant. In field experiments plants grown at high seed rates and low rates of N application attained their maximum numbers of shoots at an earlier date. Number of shoots perm2 increased with an increase in seed rate and N level. However, the number of fertile shoots per plant at harvest decreased with an increase in seed rate and were composed mostly of main shoots. The high mortality rate of shoots was attributed to the high temperatures prevailing in this country during the growth period. Mortality of shoots started earlier at high seed rates and low rates of N application.

In pot experiments, giving the N fertilizer in doses throughout the growth period reduced the rate of mortality of tillers rather than increasing their rate of initiation. A lower dose of N, given in portions over a long period, resulted in a higher number of live tillers than a dose double this amount given once at sowing. Numbers of spikelets and grains increased to a greater extent as a result of split application of N than did grain weight per ear of main shoots and of primary + secondary tillers. Mexipak had fewer spikelets per ear than Giza 155 and yet its number of grains was greater, particularly in ears of primary and secondary tillers.

Three experiments were conducted to assess the effects of different protein and energy levels on turkeys during the periods 12–16 weeks, 16–20 weeks and 20–24 weeks. Compared with 20 and 22% protein, 18% significantly depressed weight gain and feed efficiency during the 12–16 weeks period, while 14 and 16% protein, compared with 18%, significantly depressed weight gain and feed efficiency during the 16–20 weeks period but gave similar weight gain and feed efficiency as the 18% protein during the 20–24 weeks period.

During all periods between 12 and 24 weeks, the two energy levels tested (11·72 and 12·56 MJ/kg) did not significantly affect weight gain and feed efficiency whereas feed consumption was significantly higher on the lower energy level.

The present studies suggest that 20, 18 and 16% protein, all with metabolizable energy of 11·72 MJ/kg, may be recommended for turkeys aged 12–16 weeks, 16–20 weeks and 20–24 weeks respectively.

Six horses were fed Setaria sphacelata var. sericea cv. Narok hay in a mineral balance experiment and were in negative calcium balance. This should have ensured maximum efficiency of calcium absorption. Only 6·3% of calcium from a single dose of 1·32 kg calcium oxalate was retained by the horses, which supports the suggestion that horses cannot utilize calcium in tropical grasses if it is present as calcium oxalate crystals.

A study is reported of the effect of initial potential for milk production of individual cows on the change in milk output consequent upon a change in amount of feed allowed per day. In this study equal initial rations and equal changes in ration were imposed on all cows. The main conclusion was that the greater the initial yield of milk, of milk fat, of solids-not-fat (SNF) or the SNF content of the milk of a cow the greater was the effect of a change in feed allowance on that attribute. It is argued that the effects are large enough to warrant consideration in practical feeding systems.

Plasma progesterone concentrations were monitored in 69 lactating Friesland dairy cows during the post-partum period. Cyclic ovarian activity resumed in most cows within 40 days of calving. Forty-eight per cent of cows remained pregnant to their first insemination, 41% returned to oestrus before day 30 after insemination, and a further 11% returned to oestrus between days 30 and 88 after insemination.

The mean of progesterone values on days 11 to 4 before insemination tended to be higher in cows that conceived than in cows that did not conceive. These differences were signficant on day –8 (P <0·05) and on days –8, –7, –6 and –5 combined (P <0·01). Cows in which the concentration of progesterone in plasma did not rise above 4·5 ng/ml during this period did not conceive. After insemination, mean progesterone concentrations between pregnant and non-pregnant cows diverged after day +8. Relatively low concentrations of plasma progesterone (< 1 ng/ml) up to day +8 after insemination did not preclude conception. There was no indication that embryo loss between days +30 and +88 after insemination was related to an insufficiency of ovarian progesterone during early pregnancy.

Field experiments on spatial arrangements in intercropping systems were conducted under rainfed conditions in north-western India during 1975 and 1976. In these experiments sorghum yield increased by 21·6, 20·3, 29·2, 36·5 and 14·;2% when grown in association with the legumes greengrarn, blackgram, grain and fodder cow peas and groundnut respectively when compared with sorghum alone. Spatial arrangements had only marginal effect on sorghum yield but the yields of all the intercrops were appreciably affected. Paired rows with two rows of intercrop in 90 cm spacing resulted in maximum yield of all the intercrops. The land equivalent ratio (LER) was also influenced considerably by different intercrops and spatial arrangements. Planting of sorghum in paired rows having two rows of grain cow pea within 90 cm spacing gave maximum LER in both the years; however, net returns were maximum with fodder cow pea in same spatial arrangement.