The effects of ambient temperature on the daily behaviour patterns and water consumption of Border Leicester and Merino wethers were examined in an experiment where food was supplied ad libitum at points ranging from 2·4 to 5·6 km from water. The data were collected during a 12-week period when daily maximum temperatures ranged from 24 °C to 45 °C.

At distances where twice-daily drinking appeared normal and maximum air temperatures exceeded 38 °C, Merinos abandoned the afternoon walk to water, and the Border Leicesters either abandoned the walk or reduced consumption. However, until the temperature reached 38 °C water intakes of both breeds were positively related to temperature. Border Leicesters increased consumption at a mean rate of 0·42 ± 0·072 l/head/°C until maximum ambient temperatures approached 38 °C, compared with the Merino rate of 0–17 ± 0·054 l/head/°C.

Border Leicesters responded to temperature by drinking earlier in the mornings as minimum overnight temperatures rose, and by increased night activity when mean night temperatures exceeded 25 °C. Merinos showed no such response.

The effectiveness of certain pesticides a ainst adults and eggs of Tetranychus cinnabarinus Boisduval infesting cotton was sti died. Kelthane S and Rogor gave the best performance in the field evaluation, whilu Kelthane, Dursban and Cyolane were best in the laboratory evaluation. Specific acaricides were generally more toxic than the other insecticides on both adults and eggs of the mite. The slide-dip method was more sensitive for testing Kelthane, Dursban and Cyolane.

The genetic control of the level of reduced glutathione (GSH) in the erythrocytes of pure bred Australian Merino sheep has been investigated. The data suggest that the erythrocyte GSH levels are in part controlled by a single pair of autosomal alleles, the gene for GSH-high (GSHH) being dominant.

The data also suggest that the levels of erythrocyte GSH within the GSH-high and GSH-low types are the result of polygenic influences. Heritability estimates of 0·7 and 0·5 within the GSH-high type and 1·2 in the GSH-low type support this suggestion.

The effect of single, intravenous injections of urea on the concentration of ammonia in the rumen has been examined in conscious and anaesthetized sheep.

In conscious sheep maintained on a diet providing 11·4 g nitrogen/day, the net increase in concentration of rumen ammonia after the injection of urea showed negative correlations with the pre-injection concentrations of rumen ammonia and of plasma urea. The maximum concentration of ammonia attained in the rumen after the injection wasx 16·6 ± 0·28 mg NH3-N/100 ml. No such correlations were found in conscious sheep given a diet providing 20·7 g N/day. In addition, the maximum concentration of ammonia attained in the rumen after the injection of urea was significantly lower at 10·7 ± 0·91 mg NH3-N/100 ml, and the net increases in concentration were smaller.

Starvation for one day reduced the net increment in rumen ammonia concentration after urea injection in animals given the lower-N diet, to the same low level observed in fed or starved sheep maintained on the higher-N diet.

Differences were observed in the transfer of blood urea to the rumen in experiments with anaesthetized sheep which had been maintained on the lower-N diet for long or short periods beforehand. Animals which had been left to graze, and then housed indoors and given the lower-N diet for a short period before the experiment, showed much smaller increases in rumen urea plus ammonia concentration after the injection of urea than sheep which had been given the same diet for a long period. There was no difference in the response of the salivary secretions to the urea injections.

Factors which could be expected to influence levels of ammonia in the rumen were compared in sheep maintained on diets providing 11·4 or 20·7 g N/day.

The ruminal fluid volume in sheep given the lower-N ration was 78% of that in sheep maintained on the higher-N diet. The effect of this in diluting rumen ammonia from recycled urea is discussed.

Ruminal urease activity was higher in sheep given the lower-N diet, and was confined to the particulate fraction of rumen liquor in animals given either diet. At least 95% of the maximum activity occurred in the range of pH 5·4–7·05, and pH 6·0–7·25 in sheep maintained on the lower- and higher-N diets respectively. Small variations in activity were observed between the morning and evening meals.

In vitro rates of net ammonia production in samples of rumen liquor were similar in sheep given either diet; a positive correlation with the initial ammonia concentration was evident. Net utilization of ammonia was detected in some experiments in samples from sheep maintained on the lower-N diet. Starvation for 1 day was associated with increased rates of production and initial concentrations of ammonia.

Cellulose, as cotton thread, was digested at similar rates in vivo in sheep given the different diets. This is discussed in relation to the demand for ammonia by cellulolytic bacteria.

Pangola grass grown with and without sulphur fertilizer was cut as a 7-week regrowth to measure voluntary intake and digestibility by sheep. To determine the extent of a simple sulphur deficiency half the sheep on each feed were supplemented with 0·6 gsulphur daily. Retention time of feed in the reticulo-rumen and proportion of feed digested anterior to the duodenum was also determined.

Sulphur fertilizer increased the sulphur content of the pasture from 0·09 to 0·15%, voluntary intake of dry matter from 44·4 to 64·1 g/kg W0·75/day and dry-matter digestibility from 55·2 to 60·2%. Sulphur fertilizer reduced the retention time in the reticulo-rumen by 16% and increased the extent of dry-matter digestion before the duodenum from 13 to 34%.

Feeding a sulphur supplement increased dry-matter digestibility of the low sulphur feed to that found with sulphur fertilized pangola grass but only accounted for 63% of the difference in voluntary intake.

It was concluded that fertilizer sulphur leads to large increases in both voluntary intake and digestibility of sulphur deficient grass and that the improvement in nutritive value may be more than can be achieved by feeding a sulphur supplement.

Published data are used in support of a hypothesis that equal amounts of digestible cell walls and digestible non-cell walls do not contribute equally to the energy value of forages. The relationship between the concentration in the organic matter of metabolizable energy (kcal/g organic matter) determined at the maintenance level of feeding, and the percentages of cell wall and digestible cell wall in the forage organic matter is defined by:

This equation derived from published data on 12 grasses appears to be applicable to both grasses and legumes.

Pregnant beef heifers allowed ad libitum access to oat straw were given 2·7 kg molassed sugar-beet pulp alone or with additional dicalcium phosphate or urea or a combination of both materials in a Latin square design involving four feeding periods each of 21 days. Supplementation with urea to increase the total daily intake of digestible crude protein from about 130 to 290 g/day increased straw consumption by 20%. This increased the total intake of metabolizable energy from about 13 to 15 Meal/day. Increasing the total intake of phosphorus from about 6 to about 17 g P/day did not increase straw intake or digestibility or the total intake of metabolizable energy in either the presence or absence of additional urea.

Supplementation with urea increased the concentration of urea and glucose in the blood plasma and the concentration of ammonia in the rumen liquor, but did not increase the concentrations or alter the proportions of rumen volatile fatty acids. Addition of urea tended to increase the digestibility of the dry matter and crude fibre of the straw. Phosphorus supplementation increased the concentration of phosphorus in the blood plasma.

A new mutant in maize with an unusual ear location is described. The condition was found to be controlled by a simple recessive gene located near the breakpoint on chromosome 3. The gene symbol, te, is proposed.

Data from experiments with spring wheat, variety Kolibri, were used to examine size gradients within the mature ear in relation to ear development. The greatest number of grains and florets per spikelet, and the heaviest grains, occurred in the lower-mid part of the ear. Within the spikelets in this region grain 2 > grain 1 > grain 3.

It is proposed that the timing and period of ear development and the number of spikelets can be described quantitatively in terms of (1) the rate of leaf initiation, (2) the number of leaves, (3) the rate of spikelet initiation and (4) the total number of primordia. Both leaf and spikelet initiation proceeded at more or less constant rates, but spikelet initiation was about three times as fast as leaf initiation. Differentiation of the spikelet primordia started at about the time the terminal spikelet was initiated, occurring first in the spikelets in lower-mid part of the ear. The rate of floret initiation was lower than that of spikelet initiation, but did not differ between spikelets. A maximum of nine florets per spikelet was formed and then, in all spikelets, some of the last-formed primordia died, leaving two to four potentially fertile florets.

Morphologically, primordia in the lower-mid part of the ear were always the most advanced. The more rapid development of the terminal primordia tended to synchronize events such as meiosis and anthesis, thus shortening the development period of the later formed florets. Changes in meristem size were such that both length and diameter were the greatest when the primordia of the lower-mid part of the ear were initiated.

The statistical model to describe primordium initiation and ear size is compared with other models describing primordium initiation rates. The analysis of ear development in quantitative terms is discussed in relation to analyses of ear development by morphological stages. A correlation between grain size and time of floret initiation is demonstrated and the significance of the size changes in the meristem is discussed.

Four samples each of Lolium perenne, Chloris gayana and Setaria splendida grown under similar conditions and having similar in vivo dry-matter digestibilities with sheep were used in a comparison of the chemical composition of tropical and temperate grass. L. perenne had less lignin, crude fibre, neutral-detergent fibre, acid-detergent fibre and cellulose than the two tropical grasses but more neutral-detergent solubles. In vivo digestibilities of the cell-wall polysaccharides of the tropical grasses were not reduced by their higher lignin contents. The digestibilities of the cell wall were generally higher than the digestibilities for the dry matter and neutral-detergent solubles. It is suggested that the effect of lignin on the digestibility of cell-wall polysaccharides is dependent on the area of protection, and better predictions may be achieved if the cell wall is divided into two fractions, an unlignified fraction that is completely digested and a completely indigestible fraction containing all the lignin.

It is concluded that differences may be found in the carbohydrate composition of temperate and tropical grasses but that these differences may not cause differences in the overall in vivo digestibility of the dry matter.

A dynamic model was derived to predict crop response to nitrogen fertilizer under different soil and weather conditions. It combined formulae representing existing principles about important processes such as leaching of nitrate through soil and nitrate uptake by plant roots. Starting values were given for the initial plant weight and its nitrogen content and parameters were included for the crop's growth and rooting characteristics under optimum growing conditions. For each day the model re-calculated the distribution of water, nitrate and roots down the soil profile and the increment of growth.

The validity of the model was tested by using it to forecast the effects of different weather conditions and cultural practices on the nitrogen responses of a test crop, lettuce, when grown in experiments that were entirely independent of those used to obtain parameter values for the model. It successfully predicted the effects on the general shape of the response curve of the distribution of rainfall during the growing season, the age of the plant, the depth of fertilizer incorporation and the application of the nitrogen partly as a top dressing instead of entirely as a base dressing.

The model was used to develop a strategy for nitrogen fertilizer practice for lettuce in the U.K. which was found to be broadly in agreement with the results of fertilizer experiments on grower's holdings.

A food preference trial was carried out in which 21 artificially reared lambs were offered ad libitum a choice of eight foods for a period of 4 weeks commencing at 28 days of age.

Growth rate and total food intake were highly variable but the lambs agreed substantially on what they liked and disliked. Soya-bean meal was the most preferred food throughout the experimental period. Flaked maize was very unacceptable for the first 12 days (up to 40 days of age) but after that its popularity rose steadily and considerably. Fish meal was quite popular at first but after 12 days had become the least preferred food and remained so for the remainder of the time.

In the latter part of the experiment the foods could be classified into a more popular group comprising soya-bean meal, rolled barley and two proprietary pelleted diets, and a less popular group comprising fish meal, flaked maize, whole oats and sugar-beet pulp.

It is argued that in order to be acceptable diets should not be coarse and either should not contain fish meal or have the flavour disguised.

Blood samples, taken from each of 231 calves on three occasions at 9,10 and 11 weeks of age, were analysed for packed cell volume, blood glucose and Hb; and serum albumin, urea nitrogen, total protein, Ca, inorganic phosphate, Mg, K, Na and Cu. Differences in the blood composition for individual calves were demonstrated for all blood constituents (P < 0·01) with variations among calves proportionally largest for albumin and smallest for sodium. Concentrations of glucose, Hb and K were inherited (heritability estimates > 0·4).

There were significant correlations (P < 0·001) between the calves' growth rates from 1 to 12 weeks and the concentrations of each of the blood constituents, glucose Hb, K, Na, albumin and inorganic phosphate; in the cases of Na and albumin, comparison of the blood analysis at 9–11 weeks with body weights at 6 and 9 months showed that these correlations persisted, and that by 9 months differences in concentrations of Na and albumin among individuals were associated with an average difference of as much as 55 kg in body weight.

The evidence that concentrations of certain blood constituents are both inherited and related to growth rate suggests that not only might calves be screened early in life for indications of rapid growth rate, but also that animals might be bred to have the blood characteristics indicative of this quality.

The growth and development of two semi-dwarf winter wheat varieties, of two taller varieties, and of random selections from two crosses between semi-dwarf and taller varieties were compared over 2 years. Changes with time of crop dry weight/m2, leaf area index and ear size were expressed as orthogonal polynomial regression coefficients. Significant correlations were obtained between yield, the polynomial coefficients and growth measurements relating to number of tillers and flag leaf area duration, but many of these variables were significantly correlated with each other. Multiple regression equations were therefore calculated expressing yield in terms of the variables. These showed flag leaf area duration and rate of ear growth to be the most important characters determining crop yield. The greatest reduction in total yield variance was obtained by the simultaneous consideration of characters relating to photosynthetic capacity and ear development. The significance of this finding in relation to the relative importance of ‘apos;source’ and ‘sink’ in determining grain yield are discussed.

A series of stocking rate trials running for differing periods between 1961 and 1972 are summarized. Weight gains of steers grazed at 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal on Cymbopogon/Hyparrhenia/Themeda pasture are detailed. Subtreatments included continuous and rotational grazing and the removal of the unpalatable Cymbopogon afronardus.

Weight gains at 0·6 ha/animal were higher than a linear relationship between stocking rate expressed as animals/ha and weight gain would predict. This was ascribed to the dominance of the high quality grass Brachiaria decumbens at this grazing pressure.

Rotational grazing was less productive than continuous grazing, because C. afronardus increased more rapidly under this management, but there was less soil erosion. Removal of C. afronardus increased cattle growth rates and gains/ha by over 40% at 0·6 ha/animal. The cost of clearing this weed should be recovered in 2 years from a commercial cattle ranch. A grazing pressure of ca. 0·8 ha/animal is expected to maximize long-term profits on C. afronardus-free Ankole rangeland and in 3 years in this trial average gains of 0·29 kg/day/animal were achieved. This was an annual production level of 131 kg/ha/annum, which compared with 53 kg/ha at 2·4 ha/animal and 143 kg/ha at 0·6 ha/animal.

Botanical analyses of trials grazed at 3·6, 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal for 4 years are detailed. The two heaviest grazing pressures encouraged Brachiaria decumbens, a high quality grass, at the expense of Themeda triandra and Hyparrhenia filipendula. Rotational grazing allowed the weed grass Cymbopogon afronardus to regenerate after clearing more rapidly than did continuous grazing.

Bullocks with oesophageal fistulas sampled pastures grazed at 2·4, 1·2 and 0·6 ha/animal at 4-weekly intervals for 12 months. The 0·6 ha/animal treatment was repeated on pasture cleared of the weed grass Cymbopogon afronardus. Cattle growth rates, both long term and at the time of sampling, were recorded.

Cattle growth rates were greatest at 2·4 ha/animal but fistula sampling demonstrated that the diet was significantly lower in CP and higher in CF than the more heavily stocked treatments, which is contrary to the normal pattern. It is concluded that the differences in cattle growth rates at the different stocking rates were due to differences in dry-matter intake rather than the recorded differences in diet quality. The higher CP in the diet at the heavier stocking rates is ascribed to the increase of B. decumbens in the diet.

An unexplained ceiling to cattle growth rates of ca. 0·5 kg/day, and a calculated drymatter intake of < 2·1% body weight/day, in the presence of unlimited forage of 10% CP and 55% apparent digestibility, makes it more economic to stock for maximum production per ha than per animal.

Samples of monogerm sugar-beet seed which had been cleaned but not processed, contained fruits weighing 2–27 mg and true seeds weighing 0·2–5·0 mg with seed weight averaging about 20% of fruit weight. Increasing fruit size by round hole sieving resulted in progressively greater percentage emergence. Radiography revealed that one reason for this improvement was that more locules were completely filled, and fewer contained shrivelled seeds or were empty. Commercial processing of one seed lot eliminated some but not all of the empty fruits or those containing poorly developed seeds.

In the field, seedling size and root:shoot ratio increased with increasing seed size. Thus at equivalent plant densities, sugar yields were less from the smallest seed than from other grades because of the combined effects of less total growth and a less efficient partitioning of assimilates. Although improvements in establishment with increasing size grading were progressive, sugar yield at comparable plant densities was greater only from medium grades relative to the smallest grades, whilst yields from large and medium grades were similar. This difference was maintained irrespective of length of growing season or plant density.

Fourth and fifth generation inbred lines of horse and tick spring beans were used for pollination studies.

Treatments included tripping; emasculation followed by self- or cross-pollination at both the bud and mature flower stage; self-pollen rubbed on to the stigma; and the flower truss left undisturbed. Treatment means showed that there was no significant difference between leaving the flower truss undisturbed and tripping, but all other treatments differed significantly (P = 0·01) from these two. There was no difference in number of seeds set per flower between self- or cross-pollination following emasculation.

Tick inbred lines set more seeds per flower over all treatments than horse inbreds. Differences were seen between tick and horse inbreds when the flower truss was left undisturbed; some tick inbreds set seed, but no seed was set on the horse inbreds. An association between seed size and autofertility is suggested.

Results from the horse inbreds were in agreement with previous pollination studies on inbred lines of winter beans. The implications of these studies to plant breeding are discussed.

A study was made of the effect on body composition of growing Angus steers from 300 to 440 kg at three different rates. The rates were: High (H) 0·8 kg/day, Low (L) 0·4 kg/day and High-Maintenance (HM) 0·8 kg/day followed by a period during which body weight was maintained constant.

The animals were individually penned and the different growth rates were achieved by controlling intakes of a pelleted feed. Two animals (part of H treatment) were killed at 300 kg and the remaining 27 animals (nine in each treatment), were killed at common body weights of 330, 363, 400 and 440 kg.

Analyses of covariance were used to compare linear regression equations representing results from each treatment. In order to do this, the logarithmic transformation of the allometric equation, y = axb, was used. As a proportion of empty body weight (EBW), hot carcass weight (HCW) was greater in both the HM and L groups than in the H group, indicating a greater offal component of EBW in the H animals. The loss in weight of the dressed carcass during storage at 2 °C for 24 h was similar in all three groups and was 0·98% of HCW. The proportions of HCW in the fore- and hind-quarters were similar in each group.

At the same dissected side weight (DSW), the weight of bone was significantly greater in both the HM and L groups than in the H group indicating that bone development was related to both age and carcass weight. There were no significant differences between the groups in the proportions of either muscle or total fat. However, the proportion of kidney and channel fat in the H group was greater than in the HM and L groups and the proportion of subcutaneous fat was also greater in the H than in the L group. The amount of connective tissue in the three groups followed, in general, group differences in bone. Analyses of the dissected components of the separate fore- and hind-quarters showed that the difference between the H and L groups in the proportion of subcutaneous fat in the DSW was due to a relatively greater development of this fat in the fore-quarter of the H animals.

No differences were found between treatments in the proportion of ‘expensive muscles’ relative to total side muscle (TSM). However, there were treatment effects on the proportions of TSM formed by certain groups of muscles; two examples are: the proportion of group 4 muscles (abdominal muscles) was higher and the proportion of group 6 muscles (distal muscles of the fore-leg) was lower in the H than in the L treatments. Bone weight distribution was similar in all treatments.

There were differences between the H and HM groups in the relative growth ratios for all fat tissues (subcutaneous, intermuscular and kidney and channel fat) compared with total side fat. However, in the H and L groups, the relative growth ratios for corresponding fat categories were similar. The weight of kidney and channel fat in the left side of the carcass was significantly greater than in the right side of the carcass in all treatments.