1. Of various objective measurements carried out on six carcasses from each of the three Australian grades 1, 2 and Canner, the minimum depth of fat above the eye muscle at the quartering point distinguished the grades to the most significant extent, as would have been anticipated from the importance of finish in visual grading.

2. The iodine numbers of fat from the tissues of the steers examined were lower than those which would have been expected in English steers at a similar level of fatness.

The average of 160 intercalving periods of 47 imported and 33 home–reared purebred Holsteins in western Nigeria during 1967–75 was 628( ± 45) days. The probable effects of seven variables including origin of cow, sex of calf, season of calving, age of cow at calving, parity, year of calving and calf birth weight were investigated through an intra-class linear regression model in which the first three factors were treated as qualitative and the last four as quantitative factors. Origin of cow, sex of calf and season of calving did not significantly affect calving interval. Effects of age at calving, parity, year of calving and calf birth weight were highly significant (P < 0·01) but individual effects adjusted for others were not quite significant. These four quantitative factors were, however, highly interrelated; simple correlations which varied between 0·33 and 0·86 were highly significant. Interactions between the two sets of factors were negligible.

Pastures of Digitaria decumbens (pangola grass) previously oversown with Lotononis bainesii at Mount Cotton, south-east Queensland, Australia, were grazed by sheep for 3 years (1985–87), using a factorial combination of seasonal variations in stocking rate.

Lotononis behaved as a short-lived plant with a mean half-life of 4·2 months (range 1·6–10·3); rate of mortality was positively related to initial seedling density. The proportion of lotononis remained very low for the first 2 years of the experiment, when conditions were unsuitable for large-scale seedling regeneration, which was also limited by the hardness of the seed reserves. Subsequently, lotononis regenerated well in treatments which combined the following features: (i) light grazing (5 sheep/ha) during the main flowering period of spring-early summer, (ii) heavy short-duration grazing in mid-summer to create a ‘gap’ and (iii) medium or heavy (18 or 27 sheep/ha) grazing during late summer-autumn to reduce competition from pangola grass.

The ecological niche of lotononis and the possible use of complementary pastures are discussed.

It has long been held that the treatment of grassland with nitrogenous fertilizers, and especially with ammonium salts, reduces the clover content. This method has been applied also to the treatment of lawns and sports fields with a view to reducing the clover content of the turf. It has been suggested that the effect of the ammonium salts is to encourage the growth of the grass in competition with the clover, and also that the ammonium ions are specifically toxic to the clover plant. Since there is a growing volume of evidence that ammonium ions are, in fact, available to many plants and may be used by them directly, without nitrate-formation, it was thought desirable to examine the effect of the application of ammonium sulphate to clover plants grown in pots, where competition from grasses was not a factor in the consideration of the effect of manurial treatment.

(1) Animals on a calcium-deficient diet suffer periodically from loss of appetite though the ration is in every other respect satisfactory.

(2) The results of twenty-two digestion trials show no enhanced effect on the digestibility of the organic constituents of the food on adding calcium carbonate to a lime-deficient ration.

In conclusion, I wish to express my thanks to Prof. T. B. Wood, F.R.S., for giving me the necessary facilities to carry out the work; to Mr H. R. Davidson, M.A., for placing the experimental animals at my disposal and also to Dr H. E. Woodman for his active interest and supervision at all stages of the work.

The first lactation records of 684 Sahiwal, 157 Brown Swiss × Sahiwal (BS × S) and 255 Friesian × Sahiwal (F × S) constituted the data for this study. The 300-day yield was estimated from part lactation yields of 13, 17, 21, 26 and 30 weeks post partum by four methods, namely, regression, ratio, gamma and inverse polynomial functions. The duration of the part record and the method of estimation were evaluated for their reliability in estimating the 300-day yield and sire evaluation.

The correlations between part records and 300-day yield ranged from 0·76 to 0·95, thecorrelations being higher in F × S. The error, absolute error and standard deviation of error weresmaller for ratio and regression methods than for the gamma and inverse polynomial functions. The part records of 30 weeks or more were found to be necessary to estimate 300-day yield within 15% of the actual yield with regression or ratio methods.

The rank correlations and product moment correlations between sire indices calculated with part records and 300-day yield were found to be highly significant. The part records of 17 weeks or more extended by ratio or regression could be used to evaluate sires as accurately as with 300-day yield by increasing the progeny group size by 7–10% in Sahiwal and by about 20% in F × S. Theloss of efficiency in sire evaluation amounted to about 10–15% with part records of 17 weeks or more compared with 300-day yield.

The effects of heat treatment, as measured by undenatured non-casein nitrogen (NCN gN/100 g total N), and of protein: energy ratio on the digestibility coefficients and utilization of milk substitutes by lambs were investigated.

Twenty-four Finnish Landrace × Dorset Horn lambs (12 males and 12 females) were given milk substitute diets in which approximately 20 or 30% of the gross energy was supplied by protein (PE20 and PE30). NCN levels were approximately 7, 12, 18 and 5, 11, 16 for diets PE20 and PE30 respectively.

All lambs were offered a daily allowance of milk substitutes containing 7·95 MJ of gross energy from 3 to 25 days of age, when they were slaughtered and the chemical composition of the empty body was measured. Gains in the chemical components were measured using the comparative slaughter technique.

For each unit increase in NCN value there was an increase in the apparent digestibility coefficients of dry matter (D.M.), crude protein (CP) and ash of 0·13, 0·13 and 0·93 percentage units, respectively. The apparent digestibility coefficients of all the dietary components, except lactose increased by 0·24 (d.m.), 0·24 (CP), 0·63 (fat), 0·75 (ash) and 0·32 (energy) percentage units and the metabolizability by 0·24 units for each 1% increase in PE.

Live-weight and empty body-weight gains increased with increasing PE and NCN. Lambs receiving diets PE20 had a daily live-weight gain 42 g less than those on diets PE30; increasing NCN from 5 to 18 gN/100 g total nitrogen, increased live-weight gain by 33 g/day.

Increasing PE and NCN increased water gain and nitrogen retention; increasing PE also increased ash retention and decreased fat gain.

Lambs on diets PE20 contained more fat and less protein, at the same empty body weight, than those receiving diets PE30.

Efficiencies of conversion of dry matter and energy to live-weight gain, and energy and N utilization all increased with increasing NCN, but increasing PE did not affect energy utilization and decreased N utilization.

Female lambs had lower growth rates than males (—14·5 g/day) and had a higher total fat gain (128 g).

The management of non-leguminous annual forage crops can affect dry matter (D.M.) yields, chemical composition, and nutritive (feeding) values largely because of the stage of maturity at which the crop is harvested. After studies for selecting high-yield forage oat varieties for a highaltitude tropical climate (Haile, 1976), it was considered necessary to look into the management of forage oats so that the time of harvesting for maximum forage and crude protein yield could be established.

From a mixed group of cross-bred steers slaughtered at the same age, up to 12 carcasses of similar weight from each of the five conformation classes were chosen using the European Economic Community (EEC) scale for the classification of carcasses of adult bovine animals. In the hindquarter of carcasses with better conformation the ratio of muscle to bone was higher with less internal fat and more subcutaneous fat, muscles were heavier and blockier, both the carcass and leg length were shorter. Short-thick muscles were associated with short-thick bones. The results indicate that the EEC scale is a useful method to discriminate between carcasses differing in composition. It is suggested that differences in muscle: bone ratio in cattle could reflect differences in the structure and shape of bones. The conclusions remain tentative until they are confirmed on a larger number of carcasses.

An experiment, involving 68 female pigs, was undertaken to measure the effects of two diets differing in protein content, and of two patterns of feeding. The animals were housed in an enclosed building. The experiment extended through several parities; culled sows were replaced by gilts during the experiment, the whole course of which lasted 5 years.

The diets were given at the rate of 1–8 or 2–3 kg per day throughout gestation, but the rate was reversed during the 5-week lactation so that, for litters of eight to nine pigs sows in each treatment group received the same quantity of food per parity. As a result of unsatisfactory performance, dietary composition was changed after 2 years so that for the last 3 years the digestible energy contents were higher.

Treatments significantly influenced gestation live-weight gain, lactation weight loss and gestation backfat gain. The lower rate of gestation feeding was associated with low or negative gestation weight increases after the third to fourth litters, and a greater apparent rate of decline with increasing age in birth and 3-week weight per piglet. The high gestation, low lactation, rates of feeding led to slightly greater litter size and lower weaning weights per pig. A daily intake of 208 g crude protein and 8'3 g lysine appeared to meet the sow's requirements throughout gestation.

In the pregnant sow feeding area, winter air temperatures were on average 16 °C below those in the summer, but were rarely below freezing point. Winter backfat gain was lower than, and gestation gain only half that in the summer. Litter size was also greater following summer pregnancies and 3-week weight per pig was greater following winter pregnancies. Independent of litter size, birth and 3-week weight per pig were positively correlated with gestation gain within treatment and season. The apparent positive correlation of litter size at 3 weeks with gestation backfat and weight gain was not found at birth. Litter size at birth was negatively correlated with gestation gain within season. The percentage of fertile matingswas less for matings between 1 September and 31 January. This coincided approximately with the reduced litter size (alive) which occurred following winter gestations.

Lactation weight loss and 3-week weight per pig declined with increasing age of sow and the degree of weight loss was unrelated to subsequent litter size.

The apparent effect of seasons and treatments on litter size at birth appeared not to be an obvious function of changes in live weight, which were also marked between seasons and treatments, but level of food intake in early gestation may have affected litter size independently. It was concluded that birth weight especially in the older sows, was associated with the rate of food intake in gestation, and possibly also in lactation, and with gestation empty weight gain.

Among the four varieties of rice tested, the leaves of short varieties had much chlorophyll per unit leaf area and slow chlorophyll degradation, while those of tall ones showed less chlorophyll content and its rapid degradation.

The determination of in vitro dry-matter digestibility (DMD) of grass and pasture legumes under both temperate and tropical conditions is well established (Tilley & Terry, 1963; Minson & McLeod, 1972). One application of the in vitro DMD estimation of pasture samples is, together with an estimate of faecal output, the measurement of the herbage dry-matter intake of grazing cattle. Pasture samples are usually collected with oesophageal fistulated cattle. This technique is well documented and has been reviewed by a number of authors (Langlands, 1975; Minson et al. 1976).

The mechanism by which viscogen (calcium saccharate) brings about an increase in the viscosities of milk and cream has been investigated.

The primary reaction appears to be the formation of a precipitate of insoluble (tri-calcium) phosphate. Considerable quantities of casein are carried down by the precipitate, and this co-precipitation of casein is probably the single factor which most influences the viscosity.

Casein is not directly precipitated by viscogen, but the viscosity of its solutions is slightly increased as a result of their higher alkalinity due to this reagent. This action of viscogen is relatively unimportant in influencing the viscosity of milk or cream.

There are three by-products obtained from the preparation of legume seeds for human consumption which are marketed as supplemental animal foods, namely, the seed-coats (testa) which are removed from beans, peas and lentils. They are known commercially by various names, “skins,” “shells,” “husks,” “hulls” and as “offals.” They are used extensively in the East for the nutrition of cattle, where dehusked legumes enter so largely into the dietary of humans. Bean, pea and lentil husks are all used for stock feeding in Britain, and it was the frequency with which pea husks were found in commercial sheep-feeding mixtures sent for examination, and the knowledge that considerable consignments of bean shells are from time to time imported, that led to this enquiry into their nutritive value. Previous to the adoption of the Foodstuffs and Fertilisers Act, 1926, bean husks were imported into Britain in larger quantities than is at present the case, some of them being ground and added to bean meal, a practice which one has reason to believe has now ceased. Bean husks are seldom fed as such to cattle in Britain, but in France they are given to dairy cows and horses. For cows they are mixed with beet pulp, oil cakes and bran with, it is stated, good results. For horses they are mixed with oats, and an informant, a farmer from Cambrai, mixes them in equal proportions with oats for his working horses, giving to each 30 litres per day. It is claimed that the addition of the husks causes a more complete mastication of the oats and that horses do well on the mixture.

Zinc deficiency is a common nutritional problem in calcareous agricultural soils, resulting in reduced crop yield and performance. The effects of zinc sulphate (0 and 40 kg/ha) on seed yield, its components and seed element contents of 21 wheat cultivars were investigated. Zinc sulphate application increased plant height, leaf area index (LAI), flag leaf area, biomass, spike length, number of seeds per spike, seed weight and harvest index (HI). The increase in HI indicates the greater effect of zinc on seed production compared to plant biomass. In most of the cultivars, zinc sulphate application decreased the content of phosphorus and nitrogen in seeds and increased the content of iron and potassium. The cultivars showed significant differences in all the traits measured, indicating the existence of genetic diversity in the cultivars studied. In the second year, which was hotter and drier than the first year, zinc sulphate application reduced the damage caused by drought and heat stress and improved seed yield and quality. The regression fit showed that newer cultivars had lower yields in unfertilized conditions compared to old cultivars and showed their superiority in zinc fertilized conditions. It seems that the newer varieties require more fertilizer because they have been bred on fertile soils.

Quantifying reasonable crop yield gaps and determining potential regions for yield improvement can facilitate regional plant structure adjustment and promote crop production. The current study attempted to evaluate the yield gap in a region at multi-scales through model simulation and farmer investigation. Taking the winter wheat yield gap in the Huang-Huai-Hai farming region (HFR) for the case study, 241 farmers’ fields in four typical high-yield demonstration areas were surveyed to determine the yield limitation index and attainable yield. In addition, the theoretical and realizable yield gap of winter wheat in 386 counties of the HFR was assessed. Results showed that the average field yield of the demonstration plots was 8282 kg/ha, accounting for 0.72 of the potential yield, which represented the highest production in the region. The HFR consists of seven sub-regions designated 2.1–2.7: the largest attainable yield gap existed in the 2.6 sub-region, in the southwest of the HFR, while the smallest was in the 2.2 sub-region, in the northwest of the HFR. With a high irrigated area rate, the yield gap in the 2.2 sub-region could hardly be reduced by increasing irrigation, while a lack of irrigation remained an important limiting factor for narrowing the yield gap in 2.3 sub-region, in the middle of the HFR. Therefore, a multi-scale yield gap evaluation framework integrated with typical field survey and crop model analysis could provide valuable information for narrowing the yield gap.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The thirtieth meeting of the group, chaired by G. J. S. Ross of the Institute of Arable Crops Research, Rothamsted, was held in the Wellcome Meeting Room at the Royal Society, 6 Carlton House Terrace, London on Friday, 3 April 1998, when the following papers were read.