The interacting effects of genotype and density on the yield of dry matter by mature shoots were examined at Oxford, England. There were six hybrids, either pure dent or flint × dent crosses, together with two open-pollinated flint varieties of very early maturity. Over a range of 15 densities (5·0–30·8 plants/m2) for all the genotypes the relationship between the yield of the shoot and density can be adequately described by the reciprocal equation 1/w = A + Bp, where w = weight per plant, p = number of plants per unit area and A and B are constants for any particular set of conditions. Values of both 1/B (asymptotic yields) and 1/A (weight per plant at very low densities) were dependent upon the genotype. In a regression analysis between 1/w and p, the variance of 1/w was over 40 times as great at high as at low densities and a weighted analysis was necessary. Some hybrids approached maximal yields at 5 plants/m2, whereas others required a density of 10–15 plants/m2. The possible reasons for these interactions are discussed and improvements in experimental design suggested.

Fusarium solani f. sp. fabae Yu & Fang was isolated from root-rotted field bean (Vicia faba)plants at the Research Farm, Hudeiba Agricultural Research Station, Northern Province, Sudan. This is the first record of this fungus on field beans in the Sudan. Cultural and morphological characteristics of the fungus on potato-dextrose agar (PDA) and the symptoms caused are described.

Digestibility, performance and carcass analysis trials were used to compare the nutritive value of two diets, containing 78% of either cooked potato flake (diet CPF) or maize meal (diet M). Diet CPF had slightly lower values for gross energy (GE) and nitrogen (N), markedly lower values for ether extractives and crude fibre, a slightly higher lysine concentration and a markedly higher potassium concentration.

Apparent digestibility coefficients were determined with ten piglets weighing 22 kg; digestibility values for GE and N were respectively 0·95 and 0·91 for diet CPF, and 0·84 and 0·88 for diet M. Digestible energy (DE) and digestible N (DN) values were 10·2 MJ and 26·9 g/kg dry matter for diet CPF, and 15·3 MJ and 27·9 g/kg dry matter for diet M. The performance of 30 piglets grown from 21 to 53 days of age and from 6·0 to 13·1 kg was similar for each diet, as were the empty body, water, N, lipid, ash and GE gains of 18 of these piglets. The efficiencies of conversion of nutrients ingested from diet CPF into the components of body gain were for GE, DE, N and DN; 0·21, 0·22, 0·48 and 0·52 respectively. Corresponding values for diet M were 0·17, 0·21, 0·38 and 0·44.

The greater efficiency with which the nutrients in the potato flake were used thus resulted in a growth response which was at least equal to that of the maize meal.

Two breeds of zebu viz. Hariana and Sahiwal were examined for the possible existence of red cell K+ polymorphism. All the animals examined appeared to be LK type. However, red cell K+ concentration varied rather widely between 7 and 50 m-equiv/1. Within the major LK type three distinct subtypes, tentatively designated as low low (LLK), medium low (MLK) and high low (HLK) were observed. The mean red cell K+ concentration in the various subtypes in the same order were 12·5, 19·5 and 38·0 m-equiv/1 respectively. LLK animals were significantly more frequent in the Sahiwal than in the Hariana breed. The possible genetic basis of the occurrence of these subtypes within the major LK type is discussed.

LLK animals had significantly higher pcv, Hb and RBC, than MLK animals. The WBC and plasma protein values were also higher, though not significantly, in the former group. In addition, animals of the LLK subtype showed consistently lower rectal temperature at comparable levels of respiratory effort under conditions of thermal stress than MLK animals.

Eighteen varieties of safflower were studied in a randomized block design with five replications. Data on fourteen quantitative characters were recorded. Appreciable variability was displayed by all characters, especially yield and number of heads/plant. The heritability estimates ranged between 65 and 98%.

Seed (achene) yield gave a significant positive genotypic correlation with number of seeds/head, head width, bract width and oil content. The 100-seed weight was significantly negatively correlated with the number of seeds/head and plant height at maturity. The genotypic correlations between yield/plant and four other traits were partitioned into direct and indirect effects. The highest direct positive contribution to yield was given by plant height, which had also a positive indirect effect via number of heads. The direct effect of the number of heads/plant was negative and the indirect effect via head width was positive.

Results of a co-ordinated trial carried out at 20 centres indicated that increasing the dietary crude-protein percentage by 2·5 and the lysine by about 0·2 over the ARC recommended levels failed to improve performance or carcass quality, whereas decreasing these nutrients to a similar degree below the recommended levels adversely affected performance and carcass quality.

At four centres there were six to eight replicates. Substantial differences in estimates of both the level of response to a given treatment and the magnitude of treatment effects were observed between individual centres.

Factors affecting the size of these co-ordinated trials are discussed.

A technique is described for the in vivo estimation of the rate of production of bacteria in the rumen of buffalo calves. The animals were given their daily ration in 12 equal amounts at 2-h intervals. The bacterial cells from the rumen were labelled either with 14C or 36S by in vitro incubation in the presence of [U-14C]DL-leucine or 35S-sodium sulphate. Labelled bacterial cells were injected in a single dose into the rumen. Samples of the ruminal fluid were drawn at various time intervals for 9 h and the specific radio-activity of the bacteria determined. The dilution in the specific radioactivity was used to calculate the turn-over time and rates of production of bacteria in the rumen. The average turnover time was 308 min. The production rate of bacteria averaged 211 mg/min (20·3 g/mole VFA produced).

Selected herbage samples from a 6-year experiment in which nitrogen rates between 0 and 897 kg/ha were applied annually on perennial ryegrass swards were analysed for nitrate-nitrogen, true-protein and non-protein nitrogen, water-soluble carbohydrate, potassium and sodium content and for amino acid composition. The nitrate-nitrogen content of the herbage increased with increasing nitrogen rate from 224 kg/ha upwards, but the potentially toxic level of 220 mg/100 g dry matter was not reached until the annual nitrogen rate was about 560 kg/ha. On average, at the 897 kg nitrogen/ha rate the non-protein nitrogen content had increased to 27·5% of the total nitrogen yield, and 40·3% of the non-protein nitrogen yield consisted of nitrate nitrogen. Nitrate content was shown to be a sensitive indicator of the level of nitrogen nutrition of the herbage, the optimum nitrogen rate for dry-matter production coinciding with a nitrate-nitrogen content of approximately 100 mg/100g dry matter. The amino acid composition of the herbage varied little with either the rate of nitrogen or the date of cutting. It was demonstrated that, on average, a 1% unit increase in the crude-protein content of the herbage was accompanied by a 1% unit decrease in the carbohydrate content. The sodium content of the herbage increased with increasing nitrogen rate up to between 448 and 560 kg/ha, but the potassium content showed little variation.

The technique of visual appraisal of intact sides of beef was used on most of the carcasses previously described in Parts I and II of this series. Tests of discrimination and consistency were carried out for each of the judges taking part, and their assessments were compared with the results of subsequent dissection of the carcasses.

It was found that visual appraisal of the subcutaneous fat content of a carcass was very good, especially with the aid of photographic standards, though a curious tendency to match the standards consistently to carcasses of a higher proportion of fat than those used for the photographs themselves was apparent. This did not materially affect the use that can be made of visual judgements in predicting fat content and it was found that expert judgement alone is capable of predictive accuracy roughly equal to that obtained from simple measurements, though not as good as that obtained by partial dissection, as described in Part II. Equations are given for the prediction of carcass composition, using visual appraisal in combination with other variables.

The appraisal of conformation was not so successful; reasons for this are advanced, and suggestions made for future improvement.

Plasma copper levels were determined at intervals of 9 weeks over a period of 1 year on 131 female sheep of a grassland flock starting at the age of 5 months in September. The 107 survivors were re-bled 3 years later. There was a steady decline in copper levels from about 100 µg/100 ml plasma in November to about a third of that level at the beginning of the following June. Thereafter there was a partial recovery in level.

Three breeds, Scottish Blackface, Cheviot and Welsh Mountain and their crosses were represented. There were marked differences in plasma copper level among the breeds with cross-breds having levels as high or higher than the corresponding pure breeds. Breed differences in copper levels were already present at 5 months old. Part of the breed differences in copper levels were attributable to differences among the breeds in the frequency of the HbA and HbB alleles.

Correlations were calculated among the plasma copper levels from successive bleedings for individuals within breeds and subclasses. From the time the sheep reached about 9 months old these correlations ranged from 0·4 to 0·9 including bleedings more than 3 years apart in time.

Comparison of summer, winter and spring-grown cabbage showed that carotene synthesis differed considerably. Spring-grown cabbage was found to produce a peak of carotenoids during the first week of growth, and this decreased after one month. In comparison, winter-grown cabbage was still producing more carotenoids after 1 month and came to a peak of carotenoid production between 1 and 2 months. The winter-grown cabbage plants were maintained for 12 months and it was found that oxidative processes occurred at a later date than in spring- and summer-grown plants. It is shown that total carotenoids and interconversions of carotenoids are a useful indication of the metabolic processes, including oxidation and degradation of carotenoids, occurring in maturing and senescing plants.

The effect of variation of the vitamin A potent carotenoids in the cabbage, and the increased spring production of carotenoids in cabbage, are discussed in relation to the life style of P. brassicae.

The growth and yield of five highland varieties of tropical maize were studied. Grain yields were between 4·7 and 8·8 t/ha. Crop growth rates (C) increased to a maximum of between 25 and 35 g/m2/day at silking and then declined. Grain growth rates (maximum 21 g/m2/day) exceeded current C during most of the grain-filling period.

After silking, when C exceeded grain growth rate, dry matter accumulated in the stem and husk, resulting in an increase of from 200 to 600 g/m2. Later, as grain growth rate increased and exceeded current C, some of this accumulated material was incorporated into the grain, and stem weight decreased. A comparison of the dry weight changes after flowering in these varieties with those reported for a hybrid that yielded 12 t grain/ha indicates that the smaller yield of the Mexican varieties was associated with smaller grain growth rates and the incorporation into the grain of a smaller fraction of the dry weight produced after flowering. These results suggest that the capacity of the grain ‘sink’ to utilize assimilates limited yields in the tropical varieties.

The growth and yield of three tropical varieties of maize were studied at two elevations in Mexico: Poza Rica (60m) and Tlaltizapan (940m). Grain yields were between 3·5 and 8·5 t/ha. The growing period was longer and the crop produced more dry weight and yield at Tlaltizapan than at Poza Rica. Crop growth rates (C) increased to a maximum of about 35 g/m2/day at both sites and then declined. Grain growth rates (maximum 35 g/m2/day) exceeded current C during most of the grain filling period. After silking when C exceeded grain growth, dry matter accumulated in the stem. Later as grain growth increased and exceeded C, some of the accumulated material was incorporated into the grain and stem weight decreased. The dry weight increase after flowering was similar at the two sites, but the grain yield at Tlaltiapan was larger because a larger proportion of the dry weight increase was incorporated into the grain than at Poza Rica. The results indicate that at both sites grain ‘sink’ capacity was limiting yield.

Seeds of cowpea, melon, and tomato were planted in moist soil and subjected to a heat stress of 45 °C for 10 h on the day of sowing (day 0), 1 day after sowing or 2 days after sowing. The heat stress subsequently resulted in retarded hypocotyl elongation for all the crops, but the greatest retardation was due to heat stress applied on day 1 for cowpea, day 2 for melon, and day 0 for tomato. The growth-retarding effect of heat stress was associated with a delay, by 1 day, of the maximum rate of elongation of the seedlings.

Blood samples were taken from groups of lactating and non-lactating cows on three occasions from each of 24 commercial dairy herds sampled eight herds at a time at 6-weekly intervals throughout 1972. The blood samples were analysed for packed cell volume, blood glucose and haemoglobin, and for the serum concentrations of albumin, total protein, urea nitrogen, Ca, inorganic phosphate, Mg, K, Na, Cu, and Fe.

Clear seasonal patterns were evident for packed cell volume and the mean concentrations of urea nitrogen and haemoglobin each of which were highest during the summer months. The effect of season on the concentrations of the other constituents was smaller. Mean values of packed cell volume, haemoglobin and Fe were consistently higher in the non-lactating cows than in the lactating cows. Mean concentrations of Mg were lower in the blood of non-lactating cows throughout the year; Cu concentrations followed a similar trend in the autumn and winter.

There was evidence of overall herd differences regardless of season, in particular for Cu, globulin, Fe and urea nitrogen concentrations.

Fifteen hundred Thornber 808 and 909 female chicks were reared for 126 days from day-old on conventional diets or on diets with 200 g field beans/kg. From 127 to 490 days they were offered a control diet or diets with 100 or 200 g field beans/kg. When the diets fed from 127 to 490 days contained 0 or 200 g field beans/kg their food intakes were 45·4 and 44·6 kg/bird and they laid 235 and 233 eggs, respectively. The differences were not significant. Efficiency of food conversion to egg mass was significantly reduced from 0·310 to 0·303 when beans were increased from 100 to 200 g/kg of diet and mean egg weight was significantly reduced from 58·9 to 57·6 g when beans were included at 200 g/kg of diet in the 127- to 490-day period.

Five sugar beet experiments were made from 1964 to 1968 to measure yields of roots, of sugar and of tops from dressings of 0, 63, 126 or 188 kg N/ha. In 1964 and 1965 the sugar-beet tops were ploughed-in on all plots, but afterwards on only half of the total number of plots. Barley followed the sugar beet and was given 0, 41, 83 or 126 kg N/ha, in all combinations with the dressings of N to the sugar beet; grain was weighed and analysed for % N.

The maximum yield of sugar (8·24 t/ha) was with 126 kg N/ha. The yield of barley was increased greatly by giving it 83 kg N/ha, but not with more. When the barley was not given N, the residues of 126 kg N/ha for sugar beet increased grain yields by 0·17 t/ha, where the tops were carted away, and by 0·77 t/ha, where the tops were ploughed-in, but when the barley was given 83 kg N/ha, the residues increased yield negligibly (by 0·07 t/ha). Together the two sources of residue were equivalent to giving about 30 kg N/ha to the barley. Percentage N to the grain was consistently increased by both kinds of residue, but the grain never recovered more than 10 kg N/ha from them. So, sugar-beet tops had little residual value for barley, but offer a largely unused source of animal feed, rich in N.

Four groups of six 18-month-old wethers were fed a diet of hay ad libitum with a pelleted ground barley supplement for 70 days. The control group received no further dietary supplements and the sodium content (0·46%) was above that recommended by published standards. Groups 2, 3 and 4 received supplements of sodium chloride, mixed and pelleted with the barley, to provide a final dietary concentration of 1·7, 2·5 and 3·1% sodium respectively.

Dry-matter intake, dry organic-matter intake and digestible organic matter in dry matter (DOMD) were significantly reduced (P < 0·01) at the highest sodium intake. There was a reduction in live-weight gain and efficiency of utilization of digestible organic matter with increasing sodium chloride supplementation, with significant differences (P < 0·05) between the highest and lowest sodium intake groups.

There were no consistent or significant changes in the serum concentrations of sodium or potassium following sodium chloride supplementation, but serum calcium and magnesium levels were significantly lowered as a result of sodium chloride supplementation.

Sodium chloride supplementation improved the apparent availability of sodium, potassium, magnesium and calcium but reduced that of phosphorus and nitrogen. The retention of Na, K, Mg, P and N was lower at the highest sodium intake but Ca retention was higher. Urine volume and excretion of Na, K, Mg, Ca, P and N increased with sodium chloride intake.

The effects of various stimuli on the secretion of urea and ammonia in gastric juice were examined in sheep with innervated pouches in the fundic and pyloric regions of the abomasum.

Histamine, pentagastrin and feeding increased the rate of secretion and acidity of fundic juice, but had little or no effect on the concentration of urea and ammonia. The increased output of gastric juice meant that more urea and ammonia entered the abomasum in the secretions. The rate of secretion of pyloric juice was also increased by histamine and feeding, and there was an indication that histamine increased the concentration of urea + ammonia in the secretions after a period of starvation.

Intravenous injections of urea increased the concentration of ammonia in abomasal liquor. This was due in part to higher levels of ammonia in ruminal liquor passing to the abomasum, and to higher concentrations of urea + ammonia in gastric juice. The concentration of urea + ammonia in fundic juice was 45·0±1·1% of the plasma urea level, and 60·4±1·5% in the pyloric secretions.

Photosynthetic rates of flag blades were measured in eight wheat varieties. The differing rates observed were not correlated with winter or spring habit, plant height or gibberellin sensitivity. The rates were correlated inversely with the flag blade area in these varieties.

Applied gibberellin increased photosynthetic rate and the maximum increase was 17% in the variety with the lowest control rate. However, the varieties did not differ significantly in their response to the hormone.