Calves were reared on milk replacer up to 5 weeks of age and given ad libitum access to pellets and chopped straw from 1 to 10 weeks of age. Major ingredients of the pellets were ground barley (B) or ground barley and grass meal in a 6:4 ratio (G). Included in these two basal diets were NaCl or NaHCO3, each at 2, 11, 20 or 29 g Na/kg D.M.

Calves on G diets ate more than those on B diets but grew at a similar rate. The replacement value of grass meal for ground barley was 1·36:1. Most responses to Na inclusions were unaffected by the basal diets.

Before weaning there were linear increases in food intake and growth rate related to Na level in the diet. At 29 g Na/kg D.M., total D.M. intake/kg0.75 and growth rate were respectively 31 and 23% greater than at 2 g Na/kg D.M. After weaning there were differential responses to the two salts. With NaHC03 there were linear increases in food intake and growth rate up to 20 g Na/kg D.M., at which level total D.M. intake/kg0.75 and growth rate were respectively 36 and 44% greater than at 2 g Na/kg D.M. With NaCl the only significant response was that total D.M. intake at 11 g Na/kg D.M. was 16% higher than at 2 g Na/kg D.M.

Observations on acid-base balance and water intake indicated that inclusions of NaCl or NaHCO3 up to 20 g Na/kg D.M. were well tolerated by calves. Above this level there was a sharp increase in water intake, and with NaHCO3 there was a large base excess and high pH in the blood.

Groups of Bos indicus (Boran) and Bos taurus (Hereford) × Bos indicus steers were kept at constant live weights of 185, 275 and 450 kg for periods of up to 24 weeks. Maintenance of these live weights was achieved by control of the daily ration of a diet having an energy concentration of 10·477 MJ metabolizable energy (ME)/kg d.m. AS time progressed it was noted that less of the diet had to be fed daily to maintain constant live weight. Body composition of steers slaughtered at 0, 12 and 24 weeks showed that the live weights had been maintained by the compensating effect of empty body weight gains and digestive tract content-weight losses.

No significant differences were found between slaughter groups for the energy values of the boneless carcass meat nor the internal deposits of empty digestive tract, omental and mesenteric fat. It was therefore concluded that there had been a progressive increase in the efficiency of energy utilization for the production of edible meat.

The percentage reduction of daily food intake from 3 to 24 weeks necessary to maintain the prescribed live weights ranged from 51·8% for the 185 kg Borans to 17·9% for the 450 kg ¾ Boran × Hereford cross-breds.

Comparison with published estimates for maintenance of live weight showed that after 24 weeks at constant live weight the 185 and 275 kg Borans and the 450 kg ¾ Borans needed 50·5, 37·9 and 34·2% less and the 275 kg Hereford × Boran cross-breds and 450 kg ¾ Herefords 40·8 and 37·9% respectively less food than estimated.

Correction for age effects on the fasting metabolic rates of the 185 and 275 kg weight groups reduced the difference between theoretical and actual maintenance requirements from 50·5, 37·9 and 40·8% to 37·3, 29·3 and 33·8% respectively.

Attention is drawn to the need to differentiate between the live-weight maintenance needs of fast and slow growing animals which may be of similar live weights but differing ages.

An investigation was carried out to determine the daily energy intakes necessary to maintain, the live weights of ‘maintenance-stabilized’ steers (i.e. those held at constant live weight in pens for not less than 15 weeks) when walked at 5 km/h for distances of 5, 10 and 15 km/day.

The experiment utilized groups of Boran Zebu and Hereford × Boran Zebu steers at live weights of 275 and 450 kg.

Fed a standard diet of energy concentration 10·477 MJ metabolizable energy (ME)/kg D.M. it was found that the Hereford × Boran steers required significantly less food per day, at both live weights, than did the Borans to maintain live weight when walking distances of 15 km/day.

Based on the data relating to the total distance walked of 1120 km in 133 days it was calculated that the additional energy cost of maintaining live weight when walking was close to 4·184 kJ ME/kg/km walked. The efficiency of conversion of ME for walking was 50%.

For ‘maintenance-stabilized’ steers it was calculated that the 275 kg steers required 24, 49 and 73% more daily D.M. intake and the 450 kg steers 34, 69 and 97% more daily D.M. intake when walked 5, 10 and 15 km/day respectively than would have been the case if they had been kept inactive in pens.

Six experiments from 1969–71 compared yields of, percentages of N in, and removals of N by barley given 63 or 126 kg N/ha either as urea or as ‘Nitro-Chalk’ which were either broadcast or injected into the seed bed. Both fertilizers were equally effective and each gave a slightly larger yield when injected.

Eleven more experiments compared yields of, percentages of N in, and removals of N by barley given either NPK solution fertilizers or NPK granules supplying 63 or 126 kg N/ha. One liquid (14–6–8) supplied the whole of the N and was either sprayed, combine-drilled or injected mid-way between the seed rows (15 cm apart). The other liquid (4–10–10) supplied one-fifth of the N and was either combine-drilled or injected; ‘Nitro-Chalk’ supplied the remainder of the N. The granular fertilizer (20–10–10) was broadcast.

The 14–6–8 solution always gave a smaller yield than comparable granules. Yields with injected dressings were no larger than with sprays, but each was safe. Combine-drilled dressings were harmful and often killed the barley and decreased yields especially when 126 kg N/ha was given.

The 4—10–10 solution was harmless when combine-drilled and gave a larger yield than the granules when 63 kg N/ha was given and the same yield when 126 kg N/ha was given. It gave a smaller yield than the granules when it was injected.

Grain percentage N tended to be larger with the injected liquids and smaller with the sprays than with the broadcast granules though the amount of N recovered by the barley from the injected liquids was no larger than from the granules.

In five experiments with binary mixtures of a wide range of Upland cotton varieties grown at three sites in Uganda in 1969–70 and 1970–1 there was no evidence to indicate that components interacted to give better yields than would be expected from their yield in pure stand. Moreover, in district variety trials over three seasons there was no evidence that mixtures of several lines of closely related material were more stable than the individual component lines. Problems related to a breeding programme based on the development of multiline varieties are discussed. Although the variable ecological conditions in Uganda should provide an excellent opportunity of developing multilines with a high degree of population buffering, it is concluded that pure lines tested in a wide range of environments are as good as, and are less costly to produce, than mixed populations that have been specially bred and tested. Multilines with components that differ little in yielding ability or stability do, however, provide an opportunity of more rapid seed multiplication, and there is also the possibility that multiline seed issues may show progressive increases in yield with each year of growing. Present practice in Uganda of releasing as seed issues multilines with closely related components that have been adequately tested as individual lines should therefore be continued.

Chemical analyses were carried out on the three main commercial varieties in the Sudan and some wild species of Gossypium. A genome-specific pattern was not found for either the oil content, fatty acids, amino acids or seed index. G. sturtianum differed significantly from the other species in oil content with a substantial amount of unsaturated fatty acids and of the essential amino acids. A breeding programme has been started to incorporate such desirable characters into the commercial varieties.

S.24 perennial ryegrass was conserved by ensiling directly (control) and after treatment with a solution of formaldehyde at the rate of 6 g HCHO/100 g crude protein. After storage for 90 days, part of the formaldehyde-treated silage was dried in a high-temperature drier.

The quantitative digestion of the energy, carbohydrate and nitrogen moieties of the three diets and the production of volatile fatty acids and microbial protein within the rumen were measured using five sheep fitted with re-entrant cannulae at the proximal duodenum and terminal ileum.

Treatment with formaldehyde depressed organic matter and energy digestion within the rumen compared with untreated silage (P < 0·001) and a further depression was observed on the dehydrated material. Both formaldehyde-treated silages showed enhanced flows of total amino acids into the small intestine compared with the control silage and net absorption from the small intestine was elevated by 13 and 21% respectively on these two diets. On the untreated silage over 71% of the protein entering the small intestine was microbial in origin whereas, due to depressed microbial growth and increased protection of feed protein from rumen fermentation, microbial protein comprised only 17% of duodenal protein on the two formaldehyde-treated silage diets. Fifteen and 81 % of the dietary protein passed undegraded through the stomachs to the duodenum on the control and the two formaldehyde-treated silage diets respectively.

Total VFA production within the rumen was not significantly influenced by the treatments imposed, but on the untreated silage only 56% of the energy apparently digested in the rumen was converted to VTA energy whilst a mean value of 74% was recorded on the other two diets.

Estimates of the total energy absorbed gave values of 10·6, 11·9 and 10·7 MJ/kg D.M. for the control, formaldehyde and dried, formaldehyde silage diets with absorbed protein energy representing 21, 22 and 26% of the total absorbed energy respectively.

A total of 76 cows in seven, trials over a 3-year period were given a supplement of 53 g magnesiiun phosphate (supplying 11 g Mg and 10 g P/day) in 1 kg of concentrate for 21 days after starting to graze spring pasture. In contrast with 79 comparable cows given no supplement, there were significant improvements in the concentrations of magnesium and phosphorus in the blood of the cows, and significant reductions in the incidence of individual cows with low values.

Four young females of four ruminant species, namely cattle, buffalo, sheep and goat, were fed, in chopped form, a mixture of species of dry grass (Apluda aristata and Themada quadvivalvis; 3·85% crude protein) during a 28-day experimental period. Voluntary intake of grass was determined during the last 10 days and digestibility of feed nutrients during the last 6 days.

The digestibility coefficients of dry matter (D.M.) and crude fibre were higher for goats than other species, of organic matter, crude protein (CP) and ether extract were higher for goats and sheep than cows and buffaloes and of nitrogen-free extract higher for goats than cows and buffaloes and for sheep and buffaloes than cows. The daily intake of D.M., digestible CP and total digestible nutrients (TDN) is discussed in relation to body weight (BW) and kg W0·75.

Dry grass fed with mineral and vitamin supplement was adequate to sustain the body weights of buffaloes and goats but not of cows and sheep. Buffaloes utilized the dry grass better than other species as is evident from the highest feed and TDN intakes and marginal gain in weight.

Ninety-six Friesian cows were used to determine the effects of pattern of allocation of a fixed amount of concentrates on milk yield during the treatment and residual periods (weeks 1–20 and 21–44 respectively) and on the whole lactation. Thirty-two were in their second and the remainder in their third or later lactation. Second-lactation cows were used to form separate blocks.

Four treatments were imposed for the first 20 weeks of lactation; these were Graded (G), Woodman (W), High Fixed (HF), and Low Fixed (LF). The first three treatments involved the same total amount of concentrate but fed in different daily amounts. Treatment W received Woodman's standard (Evans, 1960) amounts of feed according to a predetermined lactation curve derived from earlier experience in the herd; treatment G reallocated the same allowance by feeding more than W in weeks 1–12 and less during weeks 13–20; the HF treatment was a fixed daily amount of 6·4 kg, in total also equal to W total. LF was a fixed daily amount of 4·0 kg/day. The maintenance allowance was the same for all cows within a block and based on hay, dried sugar-beet pulp and barley meal. During weeks 21–44 all cows within a block received the same treatment; either grazing or self-fed silage and supplementary concentrates according to the time of year.

There were significant differences in milk yield during the treatment period resulting from plane of feeding (W, G and HF greater than LF; P < 0·001) but no significant differences arising from the pattern of feeding. In the residual period (weeks 21–44) there was no significant difference between the yields of second-lactation treatment groups. Thus for the whole lactation the yields of treatments G, W and HF were significantly greater than LF. However, for the older cows there were differences in the residual period and treatment groups G and LF gave significantly more milk than group W (P < 0·001 and P < 0·05 respectively). Over the whole lactation treatment group G gave significantly more milk than LF (P < 0·001), W (P < 0·01) and HF (P < 0·05). Furthermore, the increase in total lactation yield of G compared with W was 4·5 times the increase observed in weeks 1–20.

Cows of both age groups on treatment HF, unlike those on treatments W and G, never achieved a distinct peak yield but their mean weekly rate of decline was significantly less.

Live-weight changes varied between treatments and between age groups and were significantly correlated with milk yield in weeks 1–20.

There were no significant effects of treatments on milk composition in either age group at any stage of the lactation. The minimum value for solids-not-fat content for the cows on the LF treatment was unacceptably low.

It is suggested that for cows of moderate yield potential fed to Woodman's standards (Evans, 1960) the actual pattern of feeding a predetermined amount of concentrates has little effect on the yield or quality of milk. For cows of high potential a redistribution of concentrates to allow earlier more generous feeding will increase milk yield.

The rate of decline of milk yield is a characteristic of both cow potential and pattern of feeding and an adoption of a standard 2½% a week should be viewed with caution.

Comparisons were made between cultivated safflower varieties (Carthamus tinctorius L.) and six wild ecotypes (C. oxyacantha Bieb.) for their tolerance to simulated drought conditions. Plant characteristics of the wild strains were noted and soil samples from their collection sites were analysed for the electrical conductivity of the saturation extract. Polyethylene glycol 6000, mannitol and sodium chloride were used as osmotic substrates to prepare aqueous solutions having 0, 1, 2, 5, 8, 12, 15 and 18 atm. of osmotic potentials (OP). The influences of treatments were studied on seed germination, shoot length and fresh and dry weights of shoots and roots of seedlings.

Increased OPs progressively delayed and reduced seed germination, shoot length and fresh and dry weights of seedlings. Shoots were, however, more adversely affected than roots. Wild ecotypes were apparently more sensitive to high OPs than the cultivated varieties.

The rate of isotopic distribution of labelled phosphorus, added as H332PO4, between inorganic and organic phosphates and phosphates contained in micro-organisms was measured in pig slurry. Incorporation of 32P in all these phosphates occurred quickly in both aerated and non-aerated pig slurry. On the basis of a simplified model, turnover times for phosphorus were calculated to be of the order of 10–20 weeks for both non-aerated and aerated pig slurry.

Pig slurry contains 1–2% P (of dry matter) of which 10–30% is in organic molecules and 2–3% is in micro-organisms. About 10–20% of the organic phosphates is in solution, amounting to 10–20 mg P/l. The concentration of inorganic P in solution is of the order of 10–100 mg/1 though, at low Ca/P ratios in the feed, can be as high as 1000 mg/1.

Organic phosphates in solution in pig slurry are of high molecular weight and probably consist of DNA complexes with polyphosphates, Ca and (if used in the feed) Cu.

It is concluded that all organic phosphates in pig slurry are of microbial origin and that the feed composition has little influence on the organic phosphate content of the slurry.

Arguments for application of the results to pig slurry in general and to wastes from other animals are given.

The birth weight of Friesian and Holstein calves in Western Nigeria was generally lower than that recorded in other tropical countries. This was attributed to a low plane of nutrition during pregnancy and a consequent reduction in length of gestation of the dams. On average, pure-bred Friesian, pure-bred Holstein and Holstein x Friesian calves weighed 29·1, 30·8 and 30·7 kg respectively at birth. Male and female Friesian, Holstein and cross-bred calves averagely weighed 29·9 and 28·2 kg, 29·9 and 31·7 kg, and 32·6 and 28·8 kg respectively. Both the sex differences and breed x sex interaction were not significant.

Positive correlation coefficients of 0·45, 0·38 and 0·26 found between calf birth weight and gestation length for the Friesians (P < 0·05), Holsteins (P < 0·01) and their crosses (P > 0·05) respectively suggest that gestation length had a significant effect on Friesian and Holstein calf birth weight. In many cases, parturition occurred 8–16 days earlier than expected.

Calves born during the rainy season (April–September) were approximately 10% heavier at birth than those born during the dry season (October–March). The heaviest calves were born during the second half (July–September) of the rainy season. The breed x sex x season of calving interaction was significant for the Holstein breed (P < 0·05). Holstein male calves born during the rainy season were significantly (P <; 0·05) heavier than those born during the dry season. Friesian dams with three or more parities and Holstein dams that were 3 years old and above produced calves that were significantly (P < 0·01) heavier at birth than calves of younger dams.

The effect of seed protein content on grain yield has been studied in varieties of spring barley, oats and wheat grown under differing cultural conditions. Grain yield was affected by seed protein content in one experiment where very low yields were attained, but the effects were inconsistent. No effect was observed in two other experiments made in a glasshouse and the field. In a growth-room experiment, seed with high protein content produced more vigorous seedlings than low-protein seed; these differences were accentuated by increasing seedling age at very low nutrient levels, but decreased with seedling age at normal nutrient levels. It is concluded from the results that variations in seed protein content are unlikely to have a significant effect on yield under practical conditions.

The theory of expected response to selection between families is extended to allow for the effects of field replication and its interactions with number of plants per plot.

This paper describes the effect of two paths of weight change on the total feed consumed and on body composition at slaughter of Angus steers. The treatments were: a 15% weight loss from 330 kg live weight, at 0·5 kg/day for 100 days, followed by recovery to 330 kg on ad libitum feed intake (WL/WG group), and constant weight at 330 kg for the same length of time as corresponding paired animals in the WL/WG group took to complete their treatment (constant-weight group). There were six animals in each group and they were slaughtered when the WL/WG steers reached 330 kg. At the beginning of the experiment four animals (preliminary group) were slaughtered at 330 kg.

Intakes of feed were recorded and measurements of apparent dry-matter digestibility were made at intervals. Chemical analyses were carried out on the right side of each carcass and on the other components of the body.

The mean total intake of the WL/WG group was 12% less than that of the constant-weight group. The daily dry-matter intake in the constant weight group decreased from 5·9 kg to 4·4 kg during the experiment.

The time taken for the WL/WG steers to regain the 50 kg weight loss varied from 30 to 68 days. Their intakes at this time and their growth rates were similar to those that they experienced when they grew to 330 kg for the first time.

Apparent digestibility varied between animals but was not influenced by treatment. The constant-weight group were fatter than the WL/WG group at slaughter and had heavier carcasses, both differences being significant (P < 0·05). The difference between groups in empty body weight was not significant. Animals from the final slaughter groups had significantly heavier heads and feet and a higher ash content than the younger steers of the preliminary group. Liver weights were reduced by nutritional restriction and did not fully recover in WL/WG steers.

Two groups of nine in-calf beef cows were given daily for the last 16 weeks of pregnancy and the first 6 weeks of lactation 1·35 increasing to 3·15 kg molassed sugarbeet pulp dry matter containing added urea together with oat straw ad libitum. Additionally, one group of cows received supplementary dicalcium phosphate which increased their total phosphorus intake from about 12 to 28 g P/day.

In the absence of phosphorus supplementation, there was a marked and significant reduction in the concentration of phosphorus in the blood, and by the 4th week of lactation this was reflected in a decrease in radiographic density of the tail bones but not in a depletion of rib bone ash.

During pregnancy a severely reduced phosphorus intake did not reduce either calf birth weight or the digestibility and voluntary intake of straw. An inadequate phosphorus intake during lactation resulted in a significant decline in voluntary straw consumption and digestibility. There was an accompanying decrease in metabolizable energy intake from about 78 to 55 MJ/day, an increased weight loss in the cows and a depression in their milk yield such as to significantly reduce calf live-weight gain.

The long period of phosphorus inadequacy did not affect the subsequent satisfactory reproductive performance of the cows when both groups were transferred to grass and mated with a bull.

The growth, development and yield of three soya-bean varieties, Hampton, Kent and CNS, were compared in two field experiments during 1974 and 1975 in Nigeria. The results, which were similar for both years, showed that the varieties differed significantly in the order Hampton > Kent > CNS for the development per plant of leaf area, number of branches, number of nodes, number of mature pods, number of seeds, pod and seed yields, husk dry weight and seed to husk ratio as well as seed yield per hectare. The differences between the varieties in seed yield could be genetic but leaf area development seems important as well. Hampton therefore appears to have the potential for high seed yield under the prevailing local conditions.

In a field experiment with 47 wheat genotypes, plant samples were taken at anthesis and maturity and analysed for nitrogen. Taking means over all genotypes, the plants contained at anthesis 83 % of the total present at maturity, while at maturity 68 % of the plant nitrogen was present in the grain.

There was significant genetic variation in most of the component attributes determining nitrogen uptake. At anthesis, the heaviest plants contained most nitrogen. Because the nitrogen concentration in the leaves (average 2·8%) was much greater than in the stems and ears (average O8 %) and the leaves comprised, on average, 37 % of the plant weight at anthesis, variation in leanness was the main cause of variation in the nitrogen content of plants of a given weight. During grain filling, plants which lost the most dry weight from their stems and leaves took up the least nitrogen.

It is suggested that the strong positive correlation between the accumulation of dry matter and of nitrogen, both until anthesis and during grain filling, occurred because both carbon assimilation and nitrate reduction depend on energy made available from chloroplasts. In addition, assimilate is required to sustain the growth of roots which is necessary for continued nitrate uptake.

The results show that it should be easier for breeders to select for high nitrogen uptake from among heavy than from among light genotypes. However, although dwarf genotypes tended to be light, none of the correlations found was strong enough to render it impossible to produce dwarf genotypes capable of giving high yields of high-protein grain.

Twenty-one stocks of spring and •winter types of field bean were sown in April 1975 and 59 stocks of spring bean cv. Maris Bead were sown in March 1976, to investigate the relationship between seed germination and seedling emergence in the field. Laboratory germination percentage proved to be a very poor indicator of emergence in the field whereas the seed leachate conductivity test was a more useful guide. Even at recommended sowing rates low plant stands are shown to be a likely cause of yield loss and it is suggested that the conductivity test should be used to identify seed stocks of low vigour so that sowing rates of such stocks can be increased. It is recommended that the conductivity test be carried out as a useful adjunct to the standard laboratory germination test.