Site of protein digestion in steers: predictability

The nature and predictability of protein digestion in steers were examined in a series of experiments. Bypass and intestinal digestion of supplemental proteins were measured with Angus steers (203 to 254 kg) fitted with dual reentrant intestinal cannulas. Daily feed intakes were 1.8 to 1.9% of body weight. Two trials were conducted with soybean meal, cottonseed meal, a hardened casein, meat meal and two different sources of dehydrated alfalfa meal fed with an 80% concentrate diet. In the third trial, digestion of soybean meal and cottonseed meal were measured with a 60% prairie hay diet. Estimates of ruminal escape or bypass were 43, 50, 36, 76, 57, 62, 24 and 43%, respectively. Results suggest that roughage level alters bypass. A standard reference system for predicting bypass based on measurements of N solubility and in situ disappearance rates was compared with measured bypass. The correlation between observed bypass to the small intestine and bypass predicted by this system was high (r = .91, P less than .01). Combining pepsin solubility, an indicator of true intestinal digestibility, with bypass estimated by the standard reference system, allowed us to predict N disappearance from the small intestine. Predicted and measured N disappearance of fed N from the small intestine were very close.     

The economics of systems research

There are three broad aspects of Systems Research worthy of particular consideration by professional personnel earning their keep within or about the agricultural research system. I will discuss these three aspects seriatim. The first is the conjecture that the systems approach constitutes a technological change in our mode of thinking about the world of such magnitude as to imply that we are now moving from one sociotechnical age to another. The second aspect, a corollary of the first, is the use of the systems approach as a framework for the selection of research programmes. The third, which also follows from the first, is the efficiency of conducting research on a systems basis. Many would think of this last aspect of efficiency as constituting ‘the economics of systems research’, but I believe the systems approach, via the first two aspects I have mentioned, has far wider implications of economic import for agricultural research.     

The uptake of metabolites of permethrin by plants grown in soil treated with [14C]permethrin

Sugar beet, wheat, lettuce and cotton were grown in soil treated with [¹⁴C]permethrin, the crops being sown at intervals of 30, 60 and 120 days after treatment of the soil. The uptake of radioactive residues into these crops was measured. Low radioactive residues (up to 0.86 μg g^?1) were detected in the mature plants sown 30 days after soil treatment, and this uptake declined significantly as the interval between soil treatment and sowing increased. Metabolites derived from the acid moiety of the permethrin molecule were shown to constitute the greater part of the residue transferring from the soil to the crops. (1RS)-cis- and (1RS)-trans-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropanecarboxylic acid and 3-(2,2-dichlorovinyl)-1-methylcyclopropane-1,2-dicarboxylic acid were identified as the major acidic metabolites. The latter compound is a metabolite of permethrin which has not previously been identified in soil or plants.     

Daminozide residues in sweet cherries,and their determination by colorimetric and gas-liquid chromatographic methods

Daminozide residues in fruit from sweet cherry trees were determined over a period of 4 years as part of an investigation into the effects of growth regulators. Analysis was by the usual colorimetric method. Additionally, for the 2 final years, a gas-liquid chromatographic method was developed to determine the 1,1- dimethylhydrazine produced by hydrolysis of daminozide residues and to confirm the results from the first method.     

Uptake of the systemic fungicide triadimefon by clover and its effect on symbiotic nitrogen fixation

Clover is frequently grown in rotation with cereals in order to increase soil nitrogen. The systemic fungicide triadimefon, widely used against cereal pathogens, is readily taken up from soil by clover and degraded to a single major metabolite. Plant weight and symbiotic nitrogen fixation by Rhizobium trijolii are affected only by concentrations of triadimefon in soil that are much in excess of those likely to be encountered in practice. Triadimefon residues are thus unlikely to affect nitrogen fixation by clover under field conditions.     

The effect of seven substituted urea herbicides on the soil microflora

Chloroxuron, diuron, fluometuron, metobromuron and monuron added to soil at 500 parts/million a.i. on a dry weight basis caused an initial stimulation of CO₂ production, followed by indications of inhibition. Nitrification was clearly inhibited, particularly by monuron and metobromuron. Metoxuron at 5 and 50 parts/million a.i. had no effect on CO₂ output and nitrification, but at 500 parts/million a.i. both were greatly reduced. Numbers of fungal propagules were temporarily lower at 50 parts/million a.i., and severely curtailed at 500 parts/million a.i. but total counts of bacterial propagules were greatly increased. Linuron had an inhibitory effect on CO₂ evolution at 500 parts/million a.i. but this varied in extent and duration; some reduction was also found at 50 parts/ million a.i. At 500 parts/million a.i. there was no effect on mineralisation of N but in soil supplemented with ammonium sulphate nitrification was reduced. Changes in microbial equilibrium occurred, but were less marked than with metoxuron. Cellulose decomposition was also reduced. Small amounts of 3,4dichloroaniline were found in linuron-treated soils, but microbial activities were not affected when 5 parts/million 3,4-dichloroaniline was added to the soil. However, at 140 parts/million microbial activities were affected adversely, but in a different pattern to that for linuron; nitrification was severely reduced, but numbers of fungal propagules were hardly affected, suggesting that the effects observed in linuron-treated soil were not due to this metabolite.