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A procedure is presented which is suitable for determining statistically based load factors for use in loading codes, without consideration of the statistics of the material of construction. This procedure involves investigating the probability of exceeding the factored design loads during the service life of the structure. The probability of exceeding the design load is defined in terms of a load index. In the development of limit states material codes the material factors can subsequently be determined using a full reliability analysis. The load index implied in the American loading code ANSI A58.1–1982 and i the American concrete code ACI 318–1983 are investigated.

In this paper, the exact partial differential equations governing the system modes of a general two-link flexible manipulator are derived by matching the boundary equations at the elbow. The resulting partial differential equation formulation is solved numerically to yield the exact eigenfrequencies corresponding to arbitrary elbow angles. The eigenfrequencies are shown to be a strong function of manipulator configuration, varying by up to 30% as the manipulator sweeps across its range of motion; this is subsequently shown to accurately predict the eigenfrequencies of an experimental two-link manipulator.

Examination of the data from 138 indoor pen-feeding trials with sheep showed that, for 22 grasses and 6 legumes grown in south-east Queensland, crude protein digestibility was related to percentage crude protein content (R = 0.885 ; P<0.001) and to the nitrogen balance of the sheep (R = 0.776 ; P<0.001). The equations derived from these relations can be used to estimate the nutritive value of protein from the crude protein content. Under ad lib. feeding; zero nitrogen balance was estimated to occur at a crude digestibility of 49 per cent (95 per cent fiducial limits = 47, 52) and this digestibility was attained at a crude protein content of 8 per cent (95 per cent limits = 7.0, 9.0). The implications of these estimates are illustrated with the aid of some data on changes with age in the crude protein content of sub-tropical grasses and legumes.

The nutritional values of 17 subtropical grasses have been compared with the use of crude protein content, crude protein digestibility, nitrogen balance, dry matter intake, and dry matter digestibility as criteria. Under the experimental conditions at the Cooper Laboratory, differences in nutritional values were obtained between individual subtropical grasses, the main differences being in digestible C.P. contents and in dry matter intakes. When mature and frost-affected grasses were fed to sheep, Paspalum plicatulum (C.P.I. 11826) and Cenchrus ciliaris (West Australian strain) had the highest nutritional values, and were superior to Panicum maximum var. trichoglume, Cenchrus ciliaris (C.P.I. 6934), Paspalum plicatulum (C.P.I. 2741), and Urochloa pullulans. These four were, in turn, better than Chloris gayana (commercial strain) and Paspalum commersonii. All grasses tested had higher nutritional values than mature natural pasture. All grasses which were fed to sheep at a young leafy stage of growth had high nutritional values. Those with the best performances at this stage were Paspalum plicatulum (C.P.I. 11826 and C.P.I. 2741), Panicum maximum var. trichoglume, and Paspahm commersonii. Limited data are presented on the nutritional values of Paspalum notatum (four strains), Paspalum malacophyllum, Panicum minus, Panicum coloratum, and Pennisetum purpureum.

The results from digestibility experiments made with 17 different subtropical grasses are discussed. The most suitable criteria for expressing nutritional values are crude protein content, crude protein digestibility, nitrogen balance, dry matter intake, and dry matter digestibility. Feeding standards based on starch equivalents and total digestible nutrients which are used in temperate environments are highly inaccurate when applied to these subtropical species. Large seasonal fluctuations occur in the nutritional value of subtropical grasses. At the height of the summer growing season values are very high and adequate for all forms of animal production. In the winter and early spring the grasses are generally of poor quality and are unable to meet the requirements for producing livestock. At this time the crude protein content and crude protein digestibility are low. Animals are also unable to obtain sufficient energy because the dry matter intakes and dry matter digestibilities of the grasses are low. The very low nutritive values obtained during winter and early spring usually occur after grasses have been killed by frost. Frost resistance is therefore an important criterion in selecting subtropical grasses which will maintain high nutritional values throughout the entire yew.

For each four subtropical grasses there is a significant correlation between daily dry matter intake and total nitrogen in faeces per day. The data have been tested for homogeneity under two hypotheses. In the first a test of the difference in slope between the four regression lines showed that they were not statistically different. It was shown that for a common mean value for total faecal nitrogen, the calculated mean daily dry matter intakes of Paspalum commersonii Lam., Urochloa pullulans Stapf, and Chloris gayana Kunth were similar and the relationship for these three could be expressed by one regression line. However, the calculated mean daily dry matter intake for Panicum maximum var. trichoglume (K. Schum.) Eyles was significantly different from those for the other three grasses and P. maximum var. trichoglume cannot be included in a general regression. In the second hypothesis it was shown that all regression lines could pass through the origin. However, as in the first hypothesis, P. commersonii, U. pullulans, and C. gayana could be represented by a common regression line whllst the regression line for P. maximum differed significantly in slope from those of the other three grasses. The results indicate that species can be grouped for this relationship, and that it could be used to measure intake of the free grazing animal on monospecific swards or on mixed swards of species with similar relationships. Lancaster's technique for determining digestibility is discussed in the light of these relationships. Neither percentage faecal nitrogen nor faecal crude fibre was found to be satisfactorily correlated with dry matter digestibility.

Two subtropical grasses, Digitaria decumbens and Sorghum almum, and one legume, Phaseolus atropurpureus (var. Siratro), cut at different ages were fed to sheep indoors to measure voluntary intake and apparent energy digestibility. Energy values of dry matter ranged from 4.11 to 4.48 kcal/g and those of organic matter from 4.47 to 4.94 kcal/g. There was a positive correlation between the energy value of organic matter and the crude protein content (r = 0.84, P < 0.01). The apparent digestibility of feed energy was correlated with species, age, and dry matter digestibility but there were significant differences between the regression equations for each species. Age was the most important factor determining the digestible energy content of the three species, and the energy value of digestible organic matter varied from 3.860 to 4.801 kcal/g. This value was positively correlated with protein content. The intake of digestible energy (kcal/kg0.75) was approximately four times as great for young cuts as for mature cuts of both grasses. Nutritive value index (N.V.I.) was closely correlated with the intake of digested energy for the three species (r > 0.998, P < 0.001), but the regression coefficient for S. almum was significantly different from those for D. decumbens and P. atropurpureus. The relative merits of the digestible energy and N.V.I. methods of expressing the energy value of pasture are discussed, and it is concluded that digestible energy is the more suitable method.

The dry matter digestibility and voluntary intake of six varieties of Rhodes grass cut on eight occasions were measured with sheep in metabolism cages. The maximum difference between varieties in digestibility percentage was 2.6 (P<0.01) for monthly regrowths and 1.1 (P<0.05) for older regrowths. The corresponding maximum differences for voluntary dry matter intake (g/W0.75/day) were 2.2 (P<0.05) and 3.5 (P<0.01). The differences in feeding value were therefore small and it was concluded that the chances are not good of selecting Rhodes grass varieties that have a superior feeding value.

Cowpea sown in January and harvested in April had a higher dry matter digestibility and voluntary intake in comparison with Dolichos. When field cured for 20 days, differences in digestibility and voluntary intake were not significant between species, and levels of both were markedly reduced. Intermediate levels for digestibility and voluntary intake were obtained after field curing for 8 days. Dry matter digestibility of Dolichos declined at subsequent first growth harvests in May, July, and August but voluntary intake for the April, May, and August cuts was similar.

Pangola (Digitaria decumbens), kikuyu (Pennisetum clandestinum), setaria (Setaria sphacelata), and buffel grasses (Cenchrus ciliaris) were cut at different stages of growth and artificially dried to provide ten feeds with a range of leaf percentages (13-56), nitrogen contents (0.42-3.70 per cent), and acid detergent fibre percentage (26.3-43.3). Half of each cut was chaffed and the remainder pelleted. Both pellets and chaff were fed to Merino wethers in metabolism cages. Pelleting decreased the mean digestibility of dry matter by 6.8 percentage units, nitrogen by 2.2 percentage units, and ADF by 11.5 percentage units. Pelleting increased the mean voluntary intake by sheep 47 per cent for dry matter and 27 per cent for digestible dry matter with only minor differences in response to pelleting mature and young grass. The smallest increase from pelleting was 4.1 per cent for buffel grass containing 0.42 per cent N. In grass of the same age in which the nitrogen content had been increased to 0.75 by fertilizer nitrogen, pelleting increased intake by 26.6 per cent. It was concluded that with mature tropical grasses the response to pelleting may be limited by a low nitrogen content. Pelleting may be a useful technique for eliminating the effect of physical structure when studying factors affecting the voluntary intake of pasture plants.

Three experiments were conducted with sheep fed ad lib. Digitaria decumbens Stent. (Pangola grass) containing 4.4 per cent crude protein (C.P.) (experiment I), and 3.7 per cent C.P. (experiments 2, 3) and supplemented with 0, 100, 200, 400 g/day lucerne (experiments 1 and 2) and white clover (experiment 3). Both legumes were also fed ad lib. with no grass. 546 The voluntary intake of the grass in experiment 1 decreased at all levels of legume feeding. In experiment 2 the voluntary intake of the grass was increased from 607 to 844 when 200 g of legume was fed, and in experiment 3 from 653 to 843 when 100 g of legume was fed, When the voluntary intake of the grass was not limited by a crude protein deficiency, the legume had a direct replacement effect causing a depression in the voluntary intake of the Pangola grass. The dry matter digestibility increased in direct proportion to the legume percentage of the ration.

The chemical composition and feeding value of seven tropical legumes and lucerne were determined by pen feeding experiments with sheep. Most of the legumes were harvested during autumn and winter. Lucerne had the highest feeding value and the highest values for the tropical legumes were obtained for Vigna vexillata, Lotononis bainesii, and Desmodium uncinatum. After frosting, the feeding values of Phaseolus lathyroides and Vigna vexillata were reduced but that of Desmodium uncinatum was not changed. This may have been due to a greater loss of leaf by both P. lathyoides and V. vexillata than by D. uncinatum. Frost did not affect Lotononis bainesii and Medicago sativa, and both had a higher feeding value than the legumes affected by frost. The usefulness of crude protein and crude fibre for estimating dry matter digestibility and dry matter intake and the relation between dry matter digestibility and dry matter intake is discussed. The use of dry matter digestibility to express the nutritive value of feed energy in preference to organic matter digestibility, starch equivalents, and total digestible nutrients is also discussed.