The yields of four tropical grass/legume pasture mixtures were studied over a 4-year period. These mixtures had the following composition: H, Cynodon nlemfuensis var. robustus, together with the legumes Centrosema pubescens (Benth.), and Stylosanthes gracilis (H.B.K.); J, Pennisetum purpureum (Schum.) plus the two legumes in H; K, treatment J mixture plus Panicum maximum (Jacq.); and L, a mixture of treatments H, J and K. Each treatment paddock was grazed in rotation between 19 April 1966 and 21 November 1969.

The mean annual dry-matter yields over the 4 years of grazing were approximately 37 ± 5·7, 41 ± 2·6, 44 ± 10·2 and 47 ± 8·7 t/ha for treatments H, J, K and L respectively. The overall mean for the four treatments was 42 ± 5·1 t/ha/annum.

It was observed that the dry-matter yield of the three mixtures in J, K and L, containing the tall grass species, was significantly superior to that of treatment H; however, they were not statistically different among themselves.

After the second year of grazing Stylosanthes gracilis diminished gradually and it was almost absent from the swards by the final year of grazing, while Centrosema pubescens maintained its stand throughout the experimental period.

With the exception of phosphorus and sodium, levels of mineral elements in the pastures were above the recommended allowances for various classes of livestock.

The average level of zinc was only slightly below the recommended value.

Dried grass originating from a farm on which herbage had been repeatedly dressed with faecal slurry from pigs given diets containing 250 mg copper/kg had a very variable, but frequently high content of copper. A maximum content of 70 mg Cu/kg dry matter was found. The mean copper content of growing herbage sampled subsequent to this finding was 10·5 mg/kg, while residues of slurry on the soil surface contained 805 mg Cu/kg.

In an experiment involving three groups of eight sheep the utilization and hepatic retention of copper from the solid residues of an aerobic digest of high-copper faecal slurry from pigs was investigated. When these residues constituted 1 or 2% of the dietary dry-matter intake of copper-deficient sheep, rapid increases in plasma copper content, in plasma ferroxidase I activity and in hepatic copper content occurred. Thus copper from this source was readily utilized and retained.

The utilization of copper added to the diet as cupric sulphate was compared with that of copper from dried slurry solids in an experiment with two groups of four sheep. Although the rate of recovery of plasma copper and ferroxidase I activity tended to be slower in sheep given slurry solids this difference was not statistically significant. A significantly slower rate of increase in hepatic copper content resulted from the ingestion of slurry solids.

The significance of these findings is discussed with particular respect to the inadvertent ingestion of residues from the soil surface of pastures dressed with slurry and from the variable inclusion of such residues in herbage uplifted during forage harvesting.

Nine field experiments with sugar beet in 1968–70 tested eight amounts of nitrogen fertilizer (0–290 kg N/ha) on a shallow calcareous loam (Icknield Series), on a deep sandy loam (Newport Series) and on a heavy clay loam (Evesham Series). Top soils and subsoils, sampled during autumn, winter and spring before the experiments, were analysed by several methods for available and potentially-available nitrogen. The largest increases in potentially-available mineral-nitrogen shown by incubation occurred in the calcareous loams every year in both top soil and sub-soil, and the sandy loam, particularly the sub-soil, generally produced least. Attempts to forecast the optimum nitrogen fertilizer dressing from the soil analyses were moderately successful, the best technique being anaerobic incubation of air-dry soil; the date of sampling had little effect. The optimum dressings were always between 0 and 125 kgN/ha, the calcareous loams generally needing least nitrogen fertilizer and the loamy sands most.

Nine field experiments with sugar beet in 1968–70 tested eight amounts of nitrogen fertilizer (0–290 kg N/ha) on a shallow calcareous loam (Icknield Series), on a deep sandy loam (Newport Series) and on a heavy clay loam (Evesham Series). The amount of mineral nitrogen in the top and sub-soils was determined before applying fertilizer and at monthly intervals from May to October in plots given 0, 125 and 250 kg N/ha. The crop on these plots was also sampled at monthly intervals throughout the growing season and the yield and nitrogen uptake determined. The soil analyses indicated that in springs with average rainfall, the leaching losses of nitrogen fertilizer are negligibly small, although there was some evidence that losses may be greatest on sandy loams. In very wet springs such as 1969, with almost double the normal rainfall, losses through leaching are considerable – on average, 40 kg N/ha. Dry-matter yields and response to nitrogen fertilizer differed between the three soils consistently from year to year. On the calcareous loam, neither amount of fertilizer changed the dry-matter yield of roots in any year. The crop on the clay loam needed a small dressing and on the sandy loam a larger dressing of fertilizer for maximum root dry-matter yield. Uptake of nitrogen by the crops usually paralleled the decreases in soil mineral nitrogen although on the clay loam nearly a third of the nitrogen applied could not be accounted for in the soil or plants, suggesting that some denitrification may have taken place. When the amount of nitrogen taken up by unfertilized crops is allowed for, the percentage recovery of applied fertilizer nitrogen at final harvest ranged from 42% on the calcareous loams to 62% on the sandy loams.

In 18 digestibility experiments with sheep, 9 diets consisting of single-grass hays and 9 diets each consisting of equal quantities of a good and poor quality hay were fed. Correlations between the voluntary intake of organic matter, digested organic matter, total cell wall and digested cell wall in all possible combinations were investigated. There were no significant differences among the simple correlation coefficients for hays fed singly or as mixtures, even though they were eaten in very different amounts. The simple pooled correlationswere significant (P < 0·01) among voluntary intake, digested organic matter and cell wall. The cell wall was significantly correlated with digested cell wall, but there was no simple correlation between voluntary intake and digested cell wall. However, when considered together in a multiple linear model they explained 58% of the variation in voluntary intake compared with 43% explained by the total cell wall alone. The additional variation accounted for by the digested cell wall was significant (P < 0·05).

The relative importance of the total cell wall and digested cell wall is discussed in relation to selection in grass breeding.

Relationships among quality number, crimp frequency and. fibre diameter of sale lots are reported for a wide range of Australian wools, the quality number appraisals being those of the selling broker and the successful bidder at auction.

Results show that sale lots classified as having the same quality number exhibit a 95% confidence interval of ± 2·5 μm about the mean value. This variation is attributed first to the dependence of quality number on staple crimp frequency and secondly to the strength of the relationship between crimp frequency and fibre diameter.

A comparison of objective and subjective appraisals of the yield of Australian greasy wool sale lots is reported.

Results suggest that although the overall agreement between the two systems of appraisal is good, the subjective estimate of an individual sale lot will only lie within ± 6% of the objective estimate in 95% of cases.

Aqueous and anhydrous ammonia were injected into a sandy loam soil, using equipment fitted with commercial injector knives. Ammonium and nitrate concentrations around the injection slits were sampled at intervals in three experiments, from March to November, December to September, and June to December.

The depth of placement and pattern of distribution of ammonium nitrogen resulting from the two designs of injector knife employed were measured.

The rate of disappearance of ammonium nitrogen was followed, and the process described by a computer program which took account of soil temperature. The rate of decay of both aqueous and anhydrous ammonia could be described approximately by assuming a decay rate of 1% per day at 0 °C and Q10 of 2·1. When 1·5% ‘N-serve’ was added to anhydrous ammonia the rate of decay was approximately halved.

The distribution pattern of nitrate ions in the soil was less well defined than that of ammonium ions. When ‘N-serve’ had been added to anhydrous ammonia nitrate concentrations were much depressed for the whole duration of the experiment. The conversion of ammonium to nitrate nitrogen in this soil appeared to be inefficient. The nitrate concentrations found in the soil were consistent with a conversion rate of one-third and with the predictions made by a leaching model using the local meteorological data.

The implications of the findings are discussed.

In order to characterize the rumen digestive physiology of South African wild ruminants investigations were made on a total of 35 individuals of six species killed in various regions during the dry season.

In buffalo, blue wildebeest and gemsbok grasses constituted 85–100% and in impala, springbok and kuduless than 10% of the diet. In the case of the latter three species effects of the habitat and of predilection for certain plant materials were apparent.

Compared with the grazers, the species feeding mainly on plant material other than grass were characterized by a smaller physiological capacity of the rumen reticulum, higher counts of ciliate protozoa and ‘large bacteria’, higher levels of rumen ammonia and higher molar proportions of rumen propionate and valerate. Within these feeding types differences between species were indicated.

Details are given of the fleece and other characteristics of three rams and three ewes of a strain that has lived feral on the island of Boreray in the St Kilda group since 1930.

The animals are horned and short-tailed, the rams are about 60 cm high at the withers and weigh about 45 kg at maturity, while the ewes weigh between 25 and 30 kg and are 55 cm high. The ewes reached their maximum weight after 1 year, but the rams increased in weight during the 3 years under observation.

The fleeces were shorter and finer than those of the modern Blackface, tending to have kemps rather than hairy heterotype fibres. The fleece weight was 1·25 kg, staple length ranged from 75 to 150 mm and mean fibre diameters ranged from 23 to 32 μm.

Variable fleece casting occurred although no more than about 80% of both the primary and secondary follicles became inactive during the winter. Unlike other primitive breeds studied there was a relatively narrow peak of follicle inactivity in midwinter, although in the ewes this tended to occur later in the winter, as observed in improved breeds.

There was a subsidiary small peak of follicle inactivity in August corresponding to the primitive shedding of the summer coat. Maximum fibre medullation occurred in June, and there was a second smaller peak in September.

As in other primitive breeds a relatively high proportion of follicles lacked fibres at birth, but this retardation of development was no longer evident by 14 days when the usual peak in medullation occurred. More fibre shedding was observed at 56 days than in the modern Blackface. The fibre type arrays were of Plateau P1 type.

The effects of an altered rumen dilution rate (D) upon the molar proportions of volatile fatty acids (VFA) in rumen liquor, VFA production rate, microbial protein synthesis and carbohydrate digestion within the rumen were studied using adult wether sheep.

Dilution rate and VFA proportions were unaltered by the infusion of up to 121 water/day into the rumen of sheep fed dried grass and concentrate (9:1). There was a small but significant (P < 0·05) increase in the rumen volume when the infusion rate was increased from 8 to 12 1/day.

The intraruminal infusion of artificial saliva (41/day), or artificial saliva containing 4% or 8% w/v polyethylene glycol (PEG) caused a significant increase in D with an associated decline in the molar proportion of propionate (Pr) in the rumen liquor. A similar effect was obtained with the intraruminal infusion of 2·5% w/v sodium bicarbonate. The overall regression of Pr on D was highly significant: Pr = 32·5–82·1D; r = –0·99, P < 0·001.

A diet of flaked maize: dried grass (6:4) was offered to three sheep each fitted with a rumen cannula and with a re-entrant cannula at the proximal duodenum. The intraruminal infusion (4 1/day) of artificial saliva containing 4% w/v PEG caused a significant (P < 0·01) increase in D and a significant (P < 0·01) depression in Pr in two animals. The dilution rate and Pr in the third animal were virtually unaltered by infusion. The regression of Pr on D for the three animals was highly significant: Pr = 34·8–136·8D; r = –0·98, P < 0·001. Each increase in D was associated with an increased flow of α-linked glucose polymer, total amino acids and total microbial amino acids into the small intestine and with an increased efficiency of microbial protein synthesis within the rumen.

The growth and development of single plants of oil seed rape, variety Zollerngold, are described quantitatively and particular attention paid to the sequence and pattern of flower and pod production on the different inflorescences. The period of flower opening over the whole plant spanned an average of 26 days and more than 75% of the pods which were retained to maturity were formed from flowers which opened within 14 days of anthesis. Most of these flowers were found on the terminal raceme and on the basal and middle regions of the axillary inflorescences arising from the uppermost three nodes.

The S. 23 cultivar of Lolium perenne L. has the ability to perform well in a wide range of environments and an experiment was designed to examine the phenotypic plasticity of S. 23 genotypes with particular reference to the level of nitrogen application.

Genotypes of S. 23 grown in a controlled growth room at close spacing (5 cm) showed a wide range of dry-matter yields with the highest yielding 144 times that of the lowest at the last of six cuts taken at 4-week intervals. Genotypes maintained much the same order of yield from one nitrogen level to another, but there were exceptions. Regression techniques were used to further quantify genotype-environment behaviour and to measure response to the environment in which the plants were grown. Considerable variation in this character occurred and the correlation of mean yield and response was incomplete. Some of the genotypes combined the desirable characters of high mean yield and good response to improved environments, while others had high mean yields, but were not as well adapted to the highest N level.

In the experiment no significant effects could be traced to differences in age of seed, but plants which had been maintained vegetatively for 7 years showed reduced vigour.

Jones & Sandland (1974) examined the validity of the linear model for gain per animal on stocking rate. This paper examines the alternative models of Conniffe, Browne & Walsh (1970, 1972) and a proposed extension of the model of Owen & Ridgman (1968). Discrepancies between these models and the linear model are studied in detail.

Under specified conditions these models are shown to be very close to the linear model. It is concluded, from the earlier work of Jones & Sandland (1974) and these results, that the empirically justified simple linear model has the advantage of being much easier to fit as well as embodying (approximately) the theoretical advantages of these conceptually superior models under a range of assumptions.

Eight laboratory and three field experiments were made on seed of Rottboellia exaltata, a grass weed of maize.

Seed stored dry, indoors or outside, either on the soil surface or buried, was unable to germinate for 5–6 months after being shed. Its ability to germinate then increased rapidly, reaching 50–70% by 8–9 months, and, indoors, continued to increase slowly to reach 80% by about ayear after being shed. Periodic wetting hastened the increase in ability to germinate of seed kept indoors or on the soil surface, but slowed down that of buried seed. When germination was tested with husks removed the ability of the caryopses to germinate began increasing soon after seed was shed, reaching 60% after 3 months and, later, up to 85–95% in different experiments. Dehusking was only effective if the inner bracts as well as the outer husks were removed, but pricking a hole through the husk and inner bracts had an effect similar to removing them. Germination decreased when in-husk seed was immersed in water before being incubated, whether this was done in air or oxygen, or in light or light/darkness, and increased again when seed was dried or its husks pierced before incubation. Wetting and drying in light, but not in darkness, increased germination of in-husk seed, and constant high temperature enhanced the increase.

When seed was buried in soil at a range of depths between 2·5 and 30 cm, the more deeply situated seed remained viable for longer than that near the surface, but there was little viable seed at any depth after 4 years. Many seedlings emerged in the first two rainy seasons after shedding of seed was prevented in an infested field which was ploughed each dry season, but by the third season the number of seedlings had greatly decreased and in the fifth season no seedlings emerged. Most of the seedlings emerging in maize fields came from seeds situated near the surface of the soil.

Washed suspensions of mixed rumen protozoa readily hydrogenated fatty acids in cottonseed, soya bean and corn oils in addition to free oleic and linoleic acids. Protozoa belonging to the family Ophryoscolecidae appeared to account for almost all the activity of mixed protozoa, protozoa of the family Isotrichidae possessing little or no ability to hydrogenate the added substrates. The hydrogenation of oleic acid was markedly increased by Fe and Mn. The addition of starch cellulose, urea and sodium formate greatly stimulated hydrogenation of oleic acid by rumen protozoa. Glucose, casein, ammonium sulphate, L-cysteine and n-valeric acid had no or little effect on extent of hydrogenation.

When suspensions of mixed protozoa were incubated in a buffer solution, an increase in iodine value was observed. The desaturation in the protozoal cells was appreciably increased by DL-methionine and was not influenced by L-cysteine. No desaturation activity by the pure suspensions of Ophryoscolecidae or Isotrichidae was observed.

The presence of protozoa in the rumen of sheep greatly increased the levels of saturated fatty acids over those in the ciliate-free animals. The concentrations of saturated fatty acids in the plasma of faunated sheep were significantly higher than those in the same animals after the removal of rumen ciliate protozoa.

The relation between composition of food and numbers of rumen ciliates was examined in three buffaloes fed once a day. Depending on the diet and time after feeding, the total protozoa varied from 0·97 x 105 to 9·11 x 105/ml rumen fluid. Entodinia formed from 87·0 to 97·1%, Diplodinia from 1·9 to 11·4%, and Holotricha from 1·0 to 1·7%. The numbers of Entodinium, Polyplastron multivesiculatum and Holotricha were least in animals fed on hay only, while the smallest number of Anoplodinium denticulatum and Eudiplodinium maggii was found in buffaloes given a mixed diet containing 13·3% of concentrates. The highest number of protozoa was found in animals fed a mixed diet containing 26·9% of concentrates. No correlation was found between level of protein, crude fibre or nitrogen extracts in food and numbers of Entodinium, Polyplasstron and Holotricha in the rumen, but numbers of Anoplodinium denticulatum and Eudiplodinium maggii increased as protein content increased.

Meadow hay and mixed food containing 13·3 or 26·9% of concentrates were used for culturing ciliates taken from the rumen of water buffalo. The culture medium was the sterilized rumen fluid or a solution of mineral salts. The cultures were mixed every 24h and one-half of the contents of each culture flask was transferred to an equal volume of fresh medium containing the appropriate food.

Anoplodinium denticulatum and seven species of Entodinium were the only protozoa which survived until the end of the experiment, but to maintain them on food containing 26·9% of concentrates an alkaline or neutral medium was required. Using rumen fluid and mineral medium the total number of protozoa was on average, respectively: 2·7 x 103 and 2·2 x 103/ml in cultures on hay only; 9·4 x 103 and 17·5 x 103/ml in cultures on food containing 26·9% of concentrates; and 14·0 x 103 and 17·;8 x 103/ml in cultures on food containing 13·3% of concentrates. Entodinium formed 66·6 and 72·5%; 95·5 and 91·8%; and 96·1 and 97·7% of the total counts. In cultures on hay alone there were 33·4 and 27·5% of Anoplodinium denticulatum, while they formed only 4·5 and 8·2% and 3·9 and 2·3% in cultures on food containing 26·9 and 13·3% of concentrates respectively.

The relation between number of ciliates and composition of food only partly agreed with the relation found previously under natural conditions. Changes in pH of the medium would appear to be the chief cause.

A field experiment to compare the growth, development and yields of four varieties of oilseed rape, Cresus, Guile, Rigo and Nilla, is described and the results discussed. Cressus was the highest-yielding variety largely because it produced more pods and more seeds per pod. The numbers of pods and seeds per pod were positively correlated with the leaf area index at the onset of flowering. This suggests that the rate of supply of carbon assimilates to the inflorescences around the time of anthesis is an important yield-determining character. The mean weight of the individual seeds was greater in Cresus than Guile and this difference, which developed late on in pod growth, also contributed to the higher yields in Cresus.

From 62 days of gestation to parturition, 20 Finnish Landrace x Dorset Horn ewes were each offered one of four diets with roughage to concentrate ratios of 20:80; 40:60; 60:40 and 80:20, at daily metabolizable energy and digestible crude protein intakes of 490 kJ and 3·55 g/kg W0·75 respectively. Plasma concentration of free fatty acids, glucose and urea were determined weekly, and nitrogen balance and digestibility trials were carried out at 70–80 and 130–140 days of gestation.

On all treatments the concentration of plasma free fatty acids increased during pregnancy from approximately 200–600 μ-equiv./l and the concentration of glucose and urea decreased by approximately 25%.

Digestibility coefficients for dry matter and organic matter increased from 58 to 68% and from 60 to 70% respectively as the proportion of concentrates in the diet increased and were not affected by stage of gestation. The apparent digestibility of nitrogen was not affected by the energy concentration of the diet.

Between mid and late gestation there was a mean increase in daily nitrogen retention of 2·5 g and an improvement in the efficiency of nitrogen utilization of 19 percentage units.

Nitrogen retention and the efficiency with which the apparently digested nitrogen intake was retained increased as the dietary energy concentration was increased. The mean daily increases in nitrogen retention were 0·0135 and 0·0039 g for each percentage unit increase in the concentrate portion of the diet at mid and late gestation respectively. The corresponding values for the improvement in the efficiency of nitrogen utilization were 0·13 and 0·10%.