The possibility of utilization of leaf wax by N2-fixing micro-organisms on the leaf surface of plants was examined. Chloroform and n-hexane extractable wax could be isolated in significant amounts, ranging between 0·13 and 6·83 g/kg fresh weight from leaves of rice cv. IR·26, wheat cv. Sonalika, jute cv. JRO 632, pigeon pea, Ficus benghalensis, F. religiosa, Eichornia crassipes, Calotropis procera and Cocos nucifera. Pigeon pea and coconut leaves were very rich in wax. The utilization of leaf wax was studied by observing the growth of micro-organisms in Burk's N-less DN2 medium containing 0·025% yeast extract and jute or coconut leaf wax as the sole C source. A 2·fold increase in growth was observed as compared with the control containing no wax. The most growth was exhibited by Pseudomonas azotogensis, P8. azotocolligans, Xanthobacter flavus, Azotobacter paspali 23A and Klebsiella pneumoniae Kupbr2. Utilization of wax components was studied by comparing the amounts of acetylated alcohols and methyl esters of fatty acids in leaves inoculated with those untreated with bacteria after separation of the components by gas chromatography. A strain of K. pneumoniae KUP4, the association of which very remarkably improved the growth of jute plants, was found to utilize particularly C10–, C13– and C16– saturatedfatty acids and C15–, C18–, C25–, C26– and C27– fatty alcohols. It is suggested that leaf wax may act partly as an energy substrate for growth of N2-fixing micro-organisms on the leaf surface.

The results are presented for a 4-year experiment in which three cutting frequency treatments and four nitrogen fertilizer rates were applied on plots sown with perennial ryegrass and one of three varieties of white clover. The cutting frequencies were three, five and tencuts each year, and the nitrogen rates were 0, 150, 300 and 450 kg/ha annually. Two medium-large leaf clover varieties Blanca and Sabeda were compared with the medium-small leaf Aberystwyth S. 100. Comparison of the present results with those from an earlier experiment (Reid, 1978) suggests that, on average over the clover varieties, the inclusion of white clover in the ryegrass sward results in smaller effects of nitrogen application rate and cutting frequency. Decreasing the number of cuts from ten to five gave a marked increase in the dry-matter yield of mixed herbage and of clover at all nitrogen rates, but the decrease from five to three cuts had little additional effect. These results suggest that white clover may be more suited to conservation systems than previously thought, but for optimum production the interval between cuts should not exceed about 5 weeks. The medium-large leaf varieties of white clover did not appear to be in any way superior to the medium-small leaf varieties for conservation systems.

A study was made in rabbits on the effects of energy intake during pregnanoy on pup birth weight and survival, and on doe body composition and milk output in the ensuing lactation. In addition the experiment examined the effects of varying crudeprotein intakes during lactation on the rate of fat loss of does and the resultant energetic efficiency of milk production.

Forty-seven multiparous cross-bred does were used. They were offered one of two diets in pregnancy, either diet HE (14·8 MJ digestible energy (DE)/kg D.M.) to appetite or diet LE (12·9 MJ DE/kg D.M.) at maintenance levels. After parturition seven does on each treatment were slaughtered and their body composition analysed (control groups). In lactation the remaining does were evenly allocated to receive either diet LE (195 g crude protein (CP)/kg D.M.) or diet HP (240 g CP/kg D.M.) to appetite. Litter sizes were standardized to six pups and litter growth rates were used as an indirect estimate of milk production. Does were then killed, at random, on day 9 or day 18 of lactation to give an estimate of changes in body composition as lactation progressed.

Does offered diet HE during pregnancy had higher carcass fat levels at parturition than their counterparts offered diet LE (496 cf. 370 g/kg carcass D.M. respectively). Litter size was unaffected by dietary treatment during pregnancy but litter weights at birth were significantly greater in HE does (442 cf. 398 g respectively). Pup mortality at birth, however, was also much higher in these animals (28 cf. 9% respectively). Voluntary food intake in early lactation (day 1—9) was depressed by feeding diet HE during pregnanoy. Milk composition was affected by pregnancy diet, with does offered diet HE producing milk containing significantly higher fat levels (HE 123 g fat/kg milk cf. LE 105 g fat/kg milk).

Doe carcass composition changes revealed that fat was usually mobilized in early lactation and gained as lactation progressed independent of dietary treatment. The protein content of the fat-free dry matter appeared to be relatively unaffected by the dietary treatments imposed. The data were used to derive an estimate of the partial efficiency of dietary energy utilization (fc) for milk output and maternal tissue gain. The line of best fit was described by the equation ER = 0·65 (±0·17) MEI-1–25, where ER = milk energy output + carcass energy change and MEI = metabolizable energy intake in MJ.

The amylolytic activity of the cytoplasmic fraction prepared from 14 single species of rumen ciliate protozoa and two natural mixed populations has been determined using five different assays. All the protozoa contained an a-amylase and the major product of amylose digestion was maltose. The highest activities were found in Eremoplastron bovis, Diploplastron affine, Ophryoscolex caudatus and Polyplastron multivesiculatum grown in vitro on grass and wholemeal flour and the lowest in Ostracodinium obtusum bilobum and Diplodinium pentacanthum under all growth conditions and in cultured Entodinium bursa and E. caudatum. The maximum activities depended on the substrate and with Eremoplastron bovis varied from 2·3 (with starch grains) to 48·8 (with amylose) μtmol maltose produced/mg protein per h.

The distribution of amylase between various rumen fractions has been determined at three times after feeding in sheep containing no ciliate protozoa or seven different protozoal populations. A method to give maximal release of the enzyme from mixed rumen bacteria was devised and three different assay methods were compared. The total rumen amylase varied by up to 2·6 times and was highest in animals that contained only Entodinium caudatum or natural A- or B-type populations. The distribution of amylase activity between rumen fractions varied considerably with the various protozoal populations, that in the protozoal cytoplasm being highest in animals containing Epidinium ecaudatum caudatum (46–53%) and the natural A- and B-type populations (35–57 %) and lowest in the animals containing no protozoa (3–11 %) or only Ostra-codinium obtusum bilobum (6–21%). The reverse was true for the activity in the bacterial fraction which contained little activity in animals with natural A- and B-type populations and over 58% of the total activity in an animal containing only Entodinium caudatum. The lowest activities in all fractions were obtained 1·5 h after feeding. Comparatively little activity was found in the plant debris or clarified rumen fluid fractions from any animal. Using results obtained previously the ratios of carboxymethylcellulase to amylase activities have been calculated and shown to be highest in the protozoal cyto-plasmic fraction of Diplodinium pentacanthum and Ostracodinium obtusum bilobum and lowest in Entodinium spp., Diploplastron affine and Eremoplastron bovis.

Two experiments are reported which investigated the effects of time and method of crop defoliation and of extending the interval between defoliation and harvest on the relationship between dry-matter percentage and tuber size in Pentland Crown potatoes.

Differences in average tuber dry-matter content between seasons and treatments were large, but the relationship between tuber dry-matter percentage and tuber size was always negatively quadratic. The dry-matter content of tubers of all sizes invariably decreased after defoliation, by about 0·6 % on average for each week that harvest was delayed in 1983 and 0·3 % in 1984. The largest decrease was from 22·7 to 16·7 % over the 10-week period following mechanical defoliation in mid-August 1983. In 1984, chemical defoliation in mid-August gave a smaller decrease than the mechanical method (0·25 and 0·38%/week) but their effects were similar when carried out in mid-September. Water uptake was the main factor responsible for the decrease because evidence showed that fresh weights of tubers increased proportionally following defoliation whilst dry weights remained virtually constant.

Natural senescence was late in both seasons experiments so that the crops foliage was still mostly alive when defoliation occurred, even in September and early October. Thus, the relatively large effects of late defoliation may have been greater than might be expected where haulm senescence is already well advanced by this time and water uptake has almost ceased. Nevertheless, the decline in dry-matter percentage which may occur between defoliation and harvest can be extremely important where potatoes for processing are concerned. It could make them unacceptable for particular outlets and should be considered when defoliation and harvesting programmes are planned.

Many pigs are given their diets in cubed or pelleted form and the process of pelleting has been shown to increase nutritive value. The reasons for increases in nutritive value following pelleting of a diet are uncertain but reductions in crude fibre and improved apparent digestibility of gross energy and dry matter (D.M.) may be involved (Lawrence, 1971, 1976, 1979). As rapeseed meal (RSM) is higher in crude fibre and, in general, of lower digestible energy value than soya-bean meal (SBM), it was thought possible that the beneficial effect of pelleting could be greater in RSM than in SBM diets.