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 Agricultural Research Council's system of feed evaluation provides a method of predicting the most profitable ration composition, given information about available feedingstuffs and the values of the parameters in the beef-feed production functions. Because these functions are non-linear, parametric estimation based on average data for a group of animals will give biased results. A method of determining unbiased estimators of the parameters is derived and the magnitude of the bias is shown to be small. Some simplifications of the ARC formulae are proposed.

Ninety-four British liming materials were examined. The contents of Ca, Mg, K, P, S, Sr, B, Fe, Mn, Zn, Cu, Co, Mo, Ni, Cd and Na in the acid-soluble fraction, and Mn, Cu, Co, Mo, Ni, Sr, Ti, Cr, Ga, Pb, Sn, V, Y, Zr and Ba in the acid-insoluble fraction were determined by chemical and spectrographic analysis. Water soluble nitrate was also determined.

Only manganese, providing on average 3 kg Mn/ha for a 10 t/ha dressing, was found in agriculturally significant quantities in the acid-soluble fraction of the limestones or shell-sands analysed. Magnesium, present only in significant amounts in the dolomitic limestones, provided on average 27 kg Mg/ha from a 10 t/ha dressing.

The acid-insoluble fraction of the limestones contained, on average, a twentieth of the concentration of Mn in the acid-soluble fraction. The concentration of K was much larger and depended on the amounts and nature of the insoluble fraction. The acidinsoluble fraction contained no significant amounts of other plant nutrients. The relative concentrations of Mn and K in both fractions emphasize that results based on the total amounts of elements in limestones could overestimate their potential value as sources of plant nutrients.

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.

Heritability in the broad sense and correlations were determined for six agronomic traits in cowpea (Vigna sinensis L.) using four parental and six F2 lines. Heritability values were found to be 75, 64, 47, 44, 35 and 15% for 100-seed weight, number of seeds per pod, number of clusters per plant, number of pods per plant, yield per plant and number of branches per plant, respectively. All of the traits studied, except number of branches per plant, showed positive significant correlations with yield. It is concluded that, for yield improvement in cowpea, number of pods per plant and number of seeds per pod have selective value equal to seed yield per plant, whereas 100-seed weight and number of clusters per plant have less selective value and number of branches per plant has no selective value.

Little is known about the carcass characteristics of unimproved commercial (or ‘Criollo’) cattle although these still account for a large proportion of slaughter animals in Latin America.

Data were collected from 52 commercial cattle in a commercial slaughterhouse in Monterrey, N.L. Mexico. They included carcass weight, length, total edible meat (carcass fat was negligible), total bone and eleven typical Mexican cuts whose anatomical relations are described. The age of the animals was judged according to dentition and data were stratified using this criterion for analysis. Variations in total edible meat, which averaged 77·4%, were almost entirely accounted for by differences in body weight. Data are presented to indicate amounts of various cuts in the carcasses and some significant differences were demonstrated in values for these cuts among age groups; possible explanations for this were discussed. Prediction equations were calculated to relate total edible meat with the selected cuts and carcass weight and it was found that carcass weight gave the best prediction of total edible meat and could also be used to predict expected weights of individual joints with reasonable accuracy.

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.

Carcass measurements have been used by various authors to predict total edible meat content of carcasses.

Measurements were made on 180 commercial quality cattle of different phenotypes and sexes in a commercial slaughterhouse in Monterrey, N.L. Measurements were carcass weight, length, forequarter depth, side circumference, length of leg, length of forearm, leg shape, area of m.l.d. and total dissected meat. Multiple regressions were computed for both linear and allometric equations using a CDC 3300 computer.

It was found that in both forms of the equation carcass weight accounted for the majority of the total variance (97·0% and 96·8% for the linear and the allometric forms respectively). Various measurements of forequarter depth improved the goodness of fit only slightly as did circumference of side and length of forearm.

The birthcoats of Finnish Landrace lambs showed a wide range of halo-hair grades but all had strongly checked fibre type arrays, which were either Plain or Valley. Transfer to Welsh Mountain dams reduced the effect of prenatal check, giving fewer sickle fibres and increased halo-hair and/or super sickle A percentage. Transfer to Border Leicester tended to have the opposite effect. Fibre diameter measurements made on skin samples indicated an increase in primary fibre diameter in transfers into Welsh dams, but no difference in transfers into the Border Leicester.

All Soay samples had Grade VII halo-hair density and Plateau or Saddle arrays. Transfer of Soay eggs to Finnish Landrace ewes increased the percentage of sickle fibres mainly at the expense of hairy-tip curly-tips. Skin samples from the transferred Soays indicated reduced primary fibre medullation, and evidence of retarded secondary follicle development.

Thus in both breeds the birthcoat changed slightly in the direction of that of the foster-dam. There was, however, no indication that increased prenatal check was associated with increased foetal size. It is therefore concluded that changes in birthcoat as a result of egg transfer are more probably due to direct effects of the maternal environment than to the effect of foetal size as previously postulated.

Simulated swards of Dactylis glomerata (var. S.37) and Lolium perenne (var. S.23) were grown in large lysimeters or vertical pipes of 15 cm diameter, both sufficiently deep to allow largely unrestricted root development.

Rainfall was excluded, and the effect of a drying cycle on the plant water balance was compared with irrigated controls in a sequence of sampling harvests at increasing soil water deficits.

Leaf water potential (ΨL) fell during the day, both in treatments and controls, to levels which might be expected to reduce extension growth and, frequently, stomatal diffusion. Rapid recovery occurred in the evening to levels which might allow normal functioning of growth processes not dependent on sunlight. Defoliation reduced plant stress and stomatal restriction.

The amelioration of plant water stress appeared to require a reduction in atmospheric evaporative demand, and irrigation had relatively little effect. The possibility is discussed that the major benefits of irrigation are other than through the relief of water stress within the plant. The significance of this is considered in relation to conventional irrigation techniques.

The leaf water status was more sensitive to drought, transpiration was reduced more, and the root system extended more slowly in Dactylis than in Lolium. Consequently, the onset of permanent wilting due to exhaustion of water from the profile was delayed compared with Lolium. It is deduced that this characteristic might enhance the survival of Dactylis in prolonged drought, but prove disadvantageous in terms of growth during short droughts, when reduced stomatal opening might limit CO2 uptake. This would not be an impediment, however, if investigations suggesting that partial closure has a minor effect on CO2 uptake compared with that on transpiration were to be confirmed.

Fertilizer experiments on lettuce were carried out over 5 years on adjacent sites of the same soil. The shapes of the response curves to both N and P varied considerably from experiment to experiment even though the amounts of those nutrients that could be extracted from the soil did not show this variation. Responses to N were of an ‘overturning’ type and the level of N at which maximum yield occurred ranged from 50 to 400 kg/ha. Responses to P were of a ‘diminishing returns’ type and the maximum increases in yield brought about by applying P ranged from 75 to 700% of the yields obtained with no application.

A mathematical model was derived which fitted the results from all the experiments satisfactorily. The parameter denning the response to P, and that denning the ‘downward’ component of the response to N were linearly related to the integral of cumulative rainfall with respect to time. Insertion of these relations into the model led to an overall model that predicted lettuce yields for each treatment in each experiment from the values of two weather parameters, the levels of N, P and K and a fitted value for seed weight. This overall model accounted for about 75% of the total variance due to fertilizer applications in the nine experiments. It is argued that most of the year-to-year variation in fertilizer response could be explained in terms of rain influencing the adverse osmotic effects on growth, the leaching of nitrate down the soil profile and dispersion of P from phosphate fertilizer granules especially in the early stages of growth.

The model was slightly improved by replacing the parameter ‘time’ with cumulative evaporation from an open water surface, but not with cumulative day degrees, or cumulative evaporation divided by vapour pressure deficit.

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.

Pigs weighing 25–40 kg were fed either once or twice per day and glucose and insulin concentration in portal and right atrial plasma measured during a 24-h cycle. Feeding resulted in an immediate increase in both portal and atrial glucose concentration. Portal glucose concentration tended to show cyclical changes with the peaks ascending and descending progressively. Under both feeding treatments glucose was absorbed from the gut for 18–20 h/day. Feeding of pure starch resulted in a rise in portal plasma glucose concentration within 10 min, but feeding of pure casein had no effect.

Portal insulin concentration increased immediately on feeding as did atrial insulin concentration, and under both feeding treatments portal and atrial insulin concentration followed a pattern similar to the corresponding glucose concentration. Feeding of pure casein was without effect on the concentration of insulin in either portal or atrial plasma.

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.

Effects of set size, density of planting, harvest date and spatial arrangement on yield and size grading of potatoes were examined using the cultivar Maris Peer. The results indicate that highest economic returns would be obtained by growing crops at between 70 and 110 eyes/m2, using small sets for late season production and large ones only for very early production, with as near a square pattern of planting as possible.

Based on these findings four growing systems were tested on a field scale, a 1·5 m raised bed with four rows, a 0·6 m ridge, a 0·9 m ridge containing two rows 0·3 m apart, and a 0·75 m ridge. Highest yields and returns were obtained from the two-row, 0·9 m, ridge system, which also had certain cultural advantages.

Preharvest sprays with 6-hydroxy-3-(2H)-pyridazinone (MH), or immersion in solutions of MH, 2,4-dichlorophenoxyacetic acid (2,4-D), 2-chloroethylphosphonic acid (ethephon), coumarin or (2-chloroethyl) trimethylammonium chloride (CCC) inhibited both sprouting and rooting of treated carrots during storage at 0 °C whencompared with water-dipped or untreated carrots, while N-6-benzyl-adenine (BA) dips stimulated extensive rooting and sprouting. In contrast, immersion in gibberellic acid (GA3) solutions had very little effect.

Storage atmospheres containing 1, 2.5, 5 or 10% oxygen inhibited both sprouting and rooting but increased mould infection. Atmospheres containing 21% (air) or 40% oxygen reduced mould infection, but increased sprouting and rooting of stored carrots. Washing carrots in water before storage did not significantly affect mould infection, while washing in 0.5% clorox increased it. However, washing in water followed by immersion in MH inhibited both sprouting and rooting and also reduced mould infection. ‘Jumbo’ and large-size carrots stored better than medium and small carrots.

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.

Two experiments, which investigated the effect of three seed sizes and three withinrow spacings on the graded yield of the two early maincrop varieties Pentland Crown and Maris Piper, are described and the results discussed.

Relationships were established between yields in various grades and stem population, and are used to explain the response of yield to changes in seed size and spacing. Comparisons between any two levels of the same treatment were affected by the size grade in which they were made. In addition, the tendency towards interactions between variety and seed size and between variety and spacing suggests that comparisons between varieties are affected by the populations at which these comparisons are made.

Three experiments (1970–2) on calcareous sandy loan tested all combinations of four plant densities (18500–124000 plants/ha), two amounts of potassium (0, 156 kg/K/ha) and sodium (0, 247 kg/Na/ha) fertilizer and two watering treatments on yield and chemical composition of sugar beet. The main effects of the treatments in all three experiments confirmed that at least 75000 plants/ha were needed for maximum sugar yield, that sodium fertilizer increased sugar yield more than potassium (+0.76 and +0.29 t/ha respectively) and that the crop responded to irrigation in some years (+1.35 t sugar/ha in 1970 and +1.67 t/ha in 1972).

Analysis of the growth of the crop showed that increasing the plant density increased leaf growth per unit area from singling onwards and giving irrigation increased it from July; the effects persisted until harvest and were reflected in increased sugar yields. Fertilizer increased leaf growth early in the season but the effect disappeared later, although sugar yield was still increased. Interactions between plant density, fertilizer treatment and irrigation were small every year but there were some consistent effects on sugar yield. The results suggest that in commercial practice the optimum density is 75000 plants/ha; where irrigation is not practised, 247 kg/ha of sodium and 70 kg/ha of potassium fertilizer should be given. Where irrigation is applied, only 247 kg/ha of sodium needs to be given as the extra water increases the uptake of soil potassium.

Data are presented from two experiments which examined the effect of three seed sizes and three within-row spacings on the bulking rate of graded potatoes from the two early mainorop varieties Pentland Crown and Maris Piper.

There were significant linear and quadratic regressions of yield on time and there were significant effects of all main treatments on the bulking rate of the crop. Differences in yield between the levels of each treatment depended upon the time of harvest and the size of tubers considered.