Live weight and total body water (TBW; measured as tritiated water space) were measured in eight pregnant cross-bred beef cows from the 6th month of gestation to approximately 1 month after calving. Using the values from these measurements and by estimating foetal, foetal fluid and foetal membrane weights from previously established prediction equations, the maternal live weight, maternal body water and maternal body solids were calculated.

Live weight, TBW, maternal body water and maternal live weight increased during gestation, whereas maternal body solids decreased. The TBW percentage of live weight increased from 74·8 to 79·6% during gestation and remained at about 79·5% during the first month of lactation.

It was concluded that live-weight changes alone could be misleading in assessing the energy balance of pregnant ruminants not only because of development of the foetus and associated structures but also because of maternal hydration.

A technique was developed for the continuous retrograde perfusion of the muscle of the right crus. The hemidiaphragm was perfused for 3 h with a semi-synthetic medium, containing fresh sheep erythrocytes. The metabolic integrity of the perfused muscle was examined. Visual appearance was satisfactory. Perfusion pressure remained constant throughout the perfusion period. An adequate perfusate flow rate (approximately 8 ml/min) was maintained over the perfusion period. Perfusion pressure and flow rate were proportional. Perfusion was complete as indicated by staining with dye and by latex casts of perfused vessels, but there were indications of heterogeneity of perfusion (the dorsal and ventral ends of the organ). Histological changes following perfusion were minor, and the perfused muscle appeared normal under an electron microscope, with the exception of a loss of cytoplasmic granules. Increases in muscle water content (2·3%) and extracellular space were small. Muscle adenosine triphosphate (ATP) and adenosine diphosphate (ADP) concentrations declined significantly following perfusion but ATP/ADP ratio increased significantly. Muscle glycogen content was maintained only when exogenous insulin was added to the medium; significant losses occurred following perfusion in the absence of insulin. Only 2–3% of tissue glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase were released into the medium over the perfusion period, but approximately 20% of muscle potassium was lost. Lactate was produced by the perfused sheep hemidiaphragm at a rate higher than those that have been reported for the perfused rat hind-limb, but lower than those reported for perfused rat diaphragm. Ratio of lactate/pyruvate produced by the perfused muscle was also higher than values reported for the rat hind-limb. The perfused muscle actively incorporated labelled amino acids into protein, but estimated protein synthetic rate in the absence of exogenous insulin was only approximately 50% of rates reported for diaphragm muscle in vivo. While the isolated, perfused sheep hemidiaphragm shows several deficiencies, it does provide a useful method for the study of ruminant muscle metabolism under carefully controlled conditions in vitro, and overcomes many of the disadvantages of other techniques that are currently available.

A urine collection system suitable for male pigs is described. The system was tested by the recovery from urine of an intravenous infusion of51 chromium as the EDTA complex. Recovery from four pigs was 99·2 ± 1·6%.

An index of feather cover is described and applied to assess the coats of various birds. Feather area indices were calculated, by analogy with the leaf area index used by crop ecologists, as the projected area of feathers above unit area of skin. Measurements were made on samples from chickens, turkeys, pheasants, sparrows and herring gulls. The index was calculated for feather tracts on six areas of the body. An overall area index was also calculated, based on the feather cover of at least 60% of the bird's body surface. Intra- and interspecific differences were large. Between species there was a positive correlation between feather index and body weight, while within species, for poultry at least, the opposite was found. This characterization of the feather coat is discussed in terms of its possible use as an index of the insulation of feathers.

The technique of radiography has been used successfully to provide permanent records of mature and developing pods in oil-seed rape. X-ray films and photographs of the pods show clearly the shape and size of the pods as well as the numbers, positions and to some extent the size of the seeds within them.

Twenty-five winter wheat varieties and breeders' lines including hard and soft texture, good or poor bread and biscuit-making types were grown at two locations in the U.K. in 1977 to provide the test samples. Small-scale tests of bread-making quality including extensometer, sodium dodecyl sulphate (SDS) sedimentation volume, residue protein, urea dispersible protein and Pelshenke tests, were compared with loaf volumes and loaf scores.

Averaged over the two sites, a modified extensometer test and the SDS test gave the closest correlation with loaf volume and loaf score and were only poorly correlated with Hagberg Falling Number and percentage protein. The SDS test gave the closest correlation between sites followed by the extensometer readings; loaf volume and score had much lower values. The SDS values and extensometer readings give a better measure of the genetic differences in protein quality of varieties than loaf volume and score, being less affected by growing conditions. With its small sample size and high throughput, the SDS sedimentation volume is likely to be the most useful screening test for wheat breeding programmes.

Differences in the field emergence of seed lots of vining peas were shown to be largely due to differences in the sensitivity of seeds to imbibition damage caused by the rapid uptake of water. The reduced emergence seen for all lots in wet soil resulted from a faster rate of water uptake and a consequent increase in imbibition damage. This caused both physiological death of low vigour seed lots and enhanced predisposition to pre-emergence mortality in unsterilized soil in all lots. The potential for the chemical protection of seeds against rapid water uptake is discussed.

A survey of sheep production was undertaken in rangeland areas of western Afghanistan to provide basic information of ewe body-weight changes throughout the year and on production variables, including mortality and lambing performance. Ewes lost up to 31% of body weight between December and March and mortality over the same period was 7%. On the basis of the results of this survey, an experiment was made to test the effect on lambing performance of pre-lambing supplementation of range-based ewes.

Supplementation reduced weight losses in ewes, but the feeding treatments did not produce significant results in terms of lamb birth weights or survival to 10 days. However, there were indications that selective feeding of weak ewes can produce economic benefits, given that the costs of supervising such animals are minimal and the price of grain supplements is low relative to the price of meat.

Data from 266 pregnancies of 144 Finn x German Mutton Merino and Finn x Awassi ewes were used to determine the effects of season of mating, dam and sire breeds, litter size and sex of the offspring, and age of the ewe on the duration of gestation.

June, September–October and January matings resulted in significantly different durations of gestation of 143·3, 145·3 and 146·1 days, respectively.

Suffolk rams’ matings resulted in a significantly shorter gestation than matings with German Mutton Merino, Schwarzkopf or cross-bred rams.

A highly significant linear regression (b = –0·80) of the duration of gestation on the number of lambs was found.

Male lambs were carried longer than female lambs.

The intraclass correlation between the gestation periods for lambs which were maternal half-sibs was highly significant.

An intercropping experiment is described in which three plant population densities of an early sorghum (82 days) were factorially combined with three plant population densities of a later-maturing pigeonpea (173 days) in a standard 2 sorghum:1 pigeonpea row arrangement. Sorghum growth was not affected by the presence of pigeonpea, and the farmers' primary objective of maintaining a ‘full’ sorghum yield was achieved if the density of the intercropped sorghum was equivalent to the sole crop optimum.

The spatial distribution of roots after 30 and 60 days of growth did not appear to be altered by intercropping, and roots of the two crops were found to intermingle freely.

The use of growth resources is examined in an intercropping combination of early sorghum (82 days) and later-maturing pigeonpea (173 days) in a row arrangement of 2 sorghum: 1 pigeonpea.

Prior to sorghum harvest, light interception by the intercrop combination was almost as high as sole sorghum. After sorghum harvest, light interception by the remaining pigeonpea was very poor and it is suggested that pigeonpea yield could be increased with higher plant population density and better plant distribution. Soil water measurements indicated that this would increase the amount of water being transpired through the crop but would not increase the total evapotranspiration demand. Higher nutrient concentrations in the intercrop pigeonpea compared with sole pigeonpea during this post-sorghum period suggested that yield of intercrop pigeonpea was not limited by nutrient stress, though the total uptake of nutrients by both crops was much greater from intercropping than sole cropping.

Ninety triple test cross (TTC) families and 32 varieties of spring wheat (used as parents in TTC programme) were raised in three randomized blocks in 1977–8 and 1978–9 to detect additive, dominance and epistatic components of genetic variation and genotype x environment interaction at both micro- and macro-environmental levels for five quantitative traits: final plant height, spike length, number of spikelets per spike, 100-kernel weight and grain yield per plant. Epistasis was an important element for yield per plant in both years. But, absence of significant epistasis was observed for two component traits of yield, namely, spike length and number of spikelets per spike, in these 2 years. Dominance was directional in all cases. Additive gene effects were most sensitive to micro- as well as to macro-environmental differences.

Two breed comparisons were made: (a) between Galway and Galway x Finnish Landrace (Fingalway) lambs, and (6) between Galway x Fingalway and Galway x (Finn x Texel) lambs, for the melting point and fatty acid composition of subcutaneous tail, subcutaneous 13th rib and perinephric fat. The lambs were slaughtered at market weight from September to January, being finished off on grass except for a small number finished indoors on concentrates and hay.

Slaughter age and carcass weight, both of which had significant effects on some of the measurements, were included as covariates in the breed comparisons. Overall breed effects were small. The melting point of the fat from Fingalway lambs was lower than that of the Galway breed in each location, the difference being significant for subcutaneous rib fat. This was associated with a lower concentration of stearic acid and a higher concentration of oleic acid in each fat depot of the Fingalway breed, the difference being significant for oleic in subcutaneous tail and for stearic in subcutaneous rib fat. No significant breed differences or trends were observed for the other fatty acids measured. Results for a small number of pure Finn lambs supported the Finn ancestry influence indicated by comparison (a). In the second breed comparison, no significant breed differences were observed, the values being close to those obtained for the pure Galway lambs.

The variation in hardening responses under different temperature regimes for three cultivars of Lolium perenne L. is described. The relative cold hardiness of the cultivars was modified by different temperatures during hardening. A threshold temperature existed above which hardening did not occur, but this temperature varied between cultivars.

Although continuous low temperatures (2 °C) favoured hardening, hardening also occurred under warm day and cool night conditions (15:2 °C) where cultivars showed contrasting hardiness responses in daylengths of 16, 12 and 8 h. Under some of these conditions both leaf growth and hardiness were possible.

The significance of these results is discussed in terms of the development of screening techniques and breeding objectives.

The results are reported for an experiment in which nitrogen rates from 0 to 672 kg/ ha and potassium rates from 0 to 558 kg/ha were applied annually on an S. 24 perennial ryegrass sward. At each of the five crops cut annually the yields of herbage dry matter and crude protein, and the potassium content of the herbage dry matter were determined. The potassium content of the soil was also measured annually. Models relating each of these variates to the nitrogen and potassium rates were derived, and their validity is demonstrated with reference to the results from earlier experiments. The problems associated with determining the correct rate of potassium fertilizer to apply on swards receiving given rates of nitrogen fertilizer are discussed using the models to predict the effects of different nitrogen-potassium combinations. In order to relate the implications of this discussion more closely to practical grassland management, economic as well as biological criteria are taken into account by incorporating cost factors in the models.

An analysis of development of Golden Promise and Maris Mink spring barley grown in England and in Scotland was made in 1976 and 1977. In both seasons the differences between varieties at a site were small. Rates of leaf emergence and primordium production and the number of primordia formed and the number which died were almost the same at both sites in 1976. In 1977 both leaf emergence and ear initiation started later in Scotland and the rates of leaf emergence and spikelet initiation were slower. Fewer spikelet primordia were formed in Scotland than in England in 1977 but a higher proportion survived to produce potentially fertile florets. Tillers emerged at the same leaf stage of the main shoot and the frequency of tillering differed at some tiller positions between England and Scotland, but the number of tillers produced was similar at both sites.

These results show that in Scotland the effect of longer photoperiod which enhances the rate of leaf emergence and primordium production compensates for the lower temperature which slows down these processes. The lower temperature in Scotland particularly in 1977 during the period of spikelet primordium death increased the proportion of spikelets that survived.

Yields of two spring barley varieties, Golden Promise and Maris Mink, were greater at the Scottish Plant Breeding Station (SPBS) than at the Plant Breeding Institute (PBI) in both 1976 and 1977. In both seasons more ears per plant were produced and the number of grains per ear was greater at the SPBS. Weight per grain was greater at the Scottish Plant Breeding Station in both 1976 and 1977, but the distribution of grain size along the ears differed between seasons. Grain at the tip of the ears of plants grown at SPBS in 1976 was lighter than the corresponding grain on the Cambridge-grown plants. In 1977 the SPBS-grown plants had heavier grains at all the main shoot spikelet positions. At the SPBS the relative difference between main shoot and tillers 1 and 2 was smaller than at the PBI.

These results are taken to indicate that the combination of climatic factors in Scotland affects plant development in such a way that intraplant competition is reduced and more spikelet primordia survive to form grains and more tillers produce fertile ears.

Field trials were made in the rainy seasons of 1970–4 at the Indian Agricultural Research Institute, New Delhi, to evaluate several systems of intercropping maize and sorghum with soya beans. Maize yields were not affected by intercropping with soya beans but sorghum yields were reduced. Though the yield of soya beans when intercropped was less than that of a sole crop, the combined grain yield of the two crops in an intercrop was more than the individual components. Land equivalent ratio (LER) increased to a maximum of about 48 and 31% by intercropping maize and sorghum with soya beans compared with the cereal sole crops. Maize rows planted 120 cm apart and intercropped with two rows of soya beans or sorghum planted 90 cm apart intercropped with one row of soya beans proved to be the best intercropping pattern.

A closed-circuit respiration chamber was used to study (a) the effect of confinement in a chamber on the heat production of pigs already accustomed to restraint in a metabolism cage; (b) changes in daily heat production of pigs following a reduction in the energy intake; and (c) the effect of increasing or decreasing the environmental temperature.

An automatically recharged version of the oxygen burette used by Waring & Brown (1965) is described. During tests of the chamber and burette system the mean recoveries of carbon dioxide and oxygen were, respectively, 0·994 and 0·995.

It is concluded that measurements of heat production on the first day of confinement were within the normal range of variation and provided valid estimates of energy expenditure.

The minimum value for the respiratory quotient (RQ) occurred on the third day following a reduction in energy intake, and it is concluded that the direct effect of previously ingested nutrients was eliminated by the third day. However, there appeared to be a further decline in heat production until 6–7 days following the reduction in energy intake.

The heat production of singly caged pigs fed almost to appetite was similar at 22 and 29 °C. Heat production increased at 15 °C, indicating that this was below the lower critical temperature of fed 25 kg pigs. The response of heat production to the low temperature continued for at least 18 days. Variations in heat production between animals and litters were as high as 15% in three experiments.

Trials were conducted on 21 farms to examine the influence of supplementary zinc on growth rate of 978 beef cattle maintained on winter rations typical of N.E. Scotland.

The concentration of zinc in the normal farm rations ranged from 13·3 to 32·1 mg/kg D.M. and half of the animals on trial on each farm received supplements providing an additional 60 mg Zn/kg D.M. Before supplementation, the farm mean plasma zinc concentrations varied from 0·73 to l·10mg Zn/l; these levels were not elevated by zinc supplementation.

The differences in mean daily weight gain between zinc-supplemented and control cattle on individual farms during 100–140 days on trial ranged from –0·14 to +0·22 kg/day and were not related to plasma zinc concentration before supplementation or to the zinc content of the basal rations. The mean daily weight gain of heifers receiving supplementary zinc was significantly greater (P < 0·02) than that of the controls by 0·05 kg/day during the first 60–80 days only. Bulls and steers showed no response to supplementary zinc.