An experiment is desoribed which was conducted for 2 years under dryland conditions of north-west India to evaluate the optimum rate of application of N fertilizer and plant population density for a rapeseed crop. Stomata closing (phenyl mercuric acetate), film forming(Mobileaf) and reflective type (kaolinite) antitranspirants were used to examine their effectson conservation of stored moisture for a possible increased water use efficiency under drylandconditions.

The rapeseed crop responded to N fertilizer and it was profitable to use 53 kg N/ha xinder these conditions. In a drier year a wider row spacing of 60 cm (1·1 x 106 plants/ ha) was significantly better than narrower spacing of 30 cm (2·2 xlO5 plants/ha). Plants grown in wider row spacings utilized less water during the vegetative and flowering stages than those grown in closer spacings.

The relative water content of leaves sprayed with antitranspirants was greater than in the control plants. The leaf temperature of the kaolinite-treated canopy was 1·5 °C lower than the ambient air temperature. Averaged over 2 years, the film-forming antitranspirant Mobileaf increased the seed yield by 26% while spraying with phenyl mercuric acetate at 50 and 75 days and kaolin application at 50 days increased the rapeseed yield by 11, 18 and 17% over the no antitranspirant treatment.

Data are reported from three experiments from 1972 to 1974 in which the effects of two row widths (66 and 132 cm) and five planting densities on the growth of two maincrop potato varieties (Désirée and Maris Piper) were studied. The results were consistent over the 3 years and showed that the effects of widening the row width were to reduce the number of axillary branches and their leaves per plant, in Maris Piper L (leaf area index), and early in the season in both varieties dry weights of leaf, stem and underground parts per plant. Row width had no effect on tuber dry weight for most of the season but at the end of sampling, tuber dry weights were greater from 132cm than from 66 cm rows. Increasing planting density reduced number of axillary branches and their leaves per plant, dry weight of leaf, stem, underground parts and tubers per plant, but increased stem length and tuber dry weight per unit area.

Leaf growth of all treatments was rapid during May and high planting densities reached an Lof 3 before the end of this month. L was increased by increased planting density throughout growth, but the lower densities were able to maintain an L of 2–3 formuch of the season. The rapid early increase in L was not associated with any prematuredecline and high rates of tuber dry-matter accumulation were achieved and maintained throughout the season. It is suggested that as the pattern of leaf growth in this environment is coincident with changing light receipts, the environment is almost ideal for the growth of maincrop potatoes.

Data are reported from three experiments from 1972 to 1974 which examined the effects of two row widths (66 cm and 132 cm) and five planting densities on number of tubers, tuber yields and tuber saleability of two maincrop potato varieties (Désirée and Maris Piper). Fewer tubers were generally found in 132 cm rows than in 66 cm rows; in 1972 reductions were most marked at high densities in both varieties and in 1974 effects were most pronounced in Maris Piper. Row width had little effect on total tuber yield at any stage of growth in either variety. The use of 132 cm rows reduced tuber greening, so that yields of saleable ware tubers at final harvest were not reduced by 132 cm rows in any year and in 1973 were higher in Désirée from 132 cm rows than from 66 cm rows. These results suggest that wider rows than are currently used in practice should be considered for maincrop potatoes, especially where water is not limiting.

Increasing planting density increased total yields in both varieties although the responsesto the final increments in planting density were small. Yields > 38 and > 57 mm declinedat the higher planting densities in Maris Piper and the optimum above-ground stem densities for ware grades differed markedly in the two varieties. Good relationships between tuber yieldsand number of above-ground stems were found in all years and support the use of stems as thebasic unit of density in this crop.

Seventy-eight Finnish Landrace × Dorset Horn ewes in lamb to Suffolk rams were slaughtered serially between 50 and 145 days of gestation. The mean litter size was 2·7. The daily feeding regime aimed to provide each ewe with 15 MJ of metabolizable energy (ME) in the first month of gestation and 9·4 MJ in the second and third. Thereafter the ewes were provided with a basal intake of either 9·6 MJ (low plane, LP) or 13·4 MJ (high plane, HP) plus 1·3 MJ for each foetus.

For ewes with 2, 3 and 4 foetuses the mean percentage changes in maternal body weight over pregnancy were respectively — 5, — 10 and — 14 (LP) or + 3, — 2 and — 6 (HP). Changes in weights of blood, liver and the empty gastro-intestinal tract through gestation varied with the plane of nutrition but not with number of foetuses. In contrast, udder weight at parturition was dependent on number of foetuses but not on plane of nutrition.

Increased hydration of the maternal tissues in late pregnancy tended to mask concurrent losses of body fat. For example, over the last 2 months, HP ewes carrying quadruplets lost on average 1·0 kg in body weight but 5·5 kg of (chemically determined) fat. The latter was lost at a rate which increased up to an average of 170 g/day over the last 2 weeks of pregnancy. Net changes in body protein were estimated to be relatively small, but there was some redistribution, including loss from muscle and gain by the udder. There was no evidence of any demineralization of the maternal skeleton.

The practical significance of the changes in body composition is discussed, in particular that of the increasing rates of loss of body fat with increasing litter size. It is suggested that the dangers implicit in these rates of fat loss must be taken into consideration when deciding on dietary regimes and the timing of breeding cycles for highly prolific ewes, or indeed when embarking on a programme of increased prolificacy.

Comparative evaluation was made on the live weight and growth pattern of calves from Bunaji (White Fulani) cows sired by Charolais, three-quarters Friesian crossbreds (three quarters Friesian and one quarter Bunaji) and Bunaji bulls in 2 years. Twelve steers per breed were evaluated on carcass merit after 250 days postweaning feeding.

Results showed that the Charolais half-cross and the Friesian three-eighth calves were heavier by up to 7, 23, 57 and 51 kg respectively at birth, weaning, 112 and 250 days after weaning than the Bunaji calves. The carcass data indicated superior slaughter weight and loin eye area in favour of the cross - breds, but no differences were found for dressed weight, dressing percentage, carcass grade and hide weight percentage among the breed groups. Carcass retail cuts showed heavier sirloin steaks and round steaks in favour of the cross-breds also.

The results were indicative of the superior growth of the cross-breds and underlined their carcass potential which may be useful in upgrading the indigenous stock. In view of the small numbers of progeny per sire group, especially among the cross-breds, further work needs to be done to confirm the present trend.

The nutritive value of uromol, a heated product of urea and molasses, was compared with raw urea–molasses and groundnut meal in three metabolic trials on buffalo calves. The non-protein nitrogen (NPN) as urea or uromol contributed about 65, 48 and 30% of the nitrogen in the experimental concentrate mixtures, replacing partially or completely the groundnut meal of the control diets. The results showed that at 65% nitrogen replacement, the crude fibre and cellulose digestibilities and the nitrogen retention of the uromol diet was similar to that of the control but was significantly (P < 0·05) higher than the urea–molasses diet. At 48% nitrogen replacement the nitrogen retention in the uromol-fed animals was still significantly (P < 0·05) higher than the urea–molasses fed group. At 30% nitrogen replacement, the differences between the control, urea–molasses and uromol groups were not significant.

In vivo rumen studies with the diets containing 50% NPN replacement showed lower but sustained ammonia-N with uromol than the urea–molasses diet. The total volatile fatty acids (TVFA) in rumen fluid, though initially higher in the control and uromol groups, were not significantly different from the urea–molasses group. Abomasal studies with diets containing 65% N as urea or uromol indicated a higher total nitrogen content in the abomasal fluid of the control and uromol-fed animals than the urea-fed animals. The 24 h abomasal passage of total-N/100 g nitrogen consumed was 95·5, 93·5 and 77·9 g in control, uromol and urea groups, respectively. The TCA-precipitatable-N (TCA-N) was also higher in the first two groups. These studies suggest that uromol is safer and has a better feeding value than urea–molasses at high rates of nitrogen replacement.

Setts of water yam (Dioscorea alata) weighing 350, 100, or 20 g were grown in the field. Tuber formation occurred in 50% of the plants at 8, 9·2, and 11 weeks after planting respectively, thus showing delayed tuber formation as sett weight decreased. Leaf area per plant and tuber yield per plant decreased with decreasing sett weight, but the tuber multiplication ratio increased with decreasing sett weight. There was a high coefficient of variation for tuber yield per plant and for leaf area per plant. It is suggested that the delayed tuber formation for small setts may be partly responsible for the low tuber yield per plant observed.

Two rain shelters, each covering an area of 210 m2, have been built at Rothamsted for use in tillage experiments and drought experiments. Each shelter automatically moves over the experimental area when rain starts, and moves away when rain stops; thus all rain is kept off, but other aspects of the microclimate are little affected. Small experimental plots were used, and, except in the 0·5 m strips at the plot edges, the height and yield of a barley crop were uniform. Irrigation water to some plots was labelled with tritium; when applied to very dry plots, a measurable proportion of this water moved laterally by more than 1·0 m. However, the total quantity of water transferring between adjacent plots was not large enough to inconvenience the tillage or drought experiments.

A barley-based diet, containing 16% protein, was given at average daily rates of 1·2–2·5 kg (16–32 MJ, metabolizable energy (ME)) to 32 female and 32 castrated male pigs during their growth from 25 to 90 kg. At high intakes there was no difference in growth rate between the sexes, but with progressive feed restriction the growth of males was more severely retarded than that of the females. Both sexes achieved their minimum feed conversion ratios at approximately 25 MJ. The reductions of fat thickness with progressive feed restriction were greater by approximately 20% in the females than in the males. The two sexes had the same mean back fat thickness when the gilts had 4·7 MJ more ME per day than the castrates. It was inferred that the energy requirement for maintenance was 15% greater in the males than in the females.

The pollination requirements of eight cultivars of swede rape (Brassica napus) and two of turnip rape (Brassica campestris) grown in a glasshouse, were compared. Cultivars differed in the number of pods, and of seeds per pod set by auto-pollination. Cultivars of turnip rape yielded more when cross-pollinated than when self-pollinated by hand but those of swede rape did not, although additional pollination of swede rape increased the set of early flowers. Inadequate pollination probably limits yield in self-fertile cultivars of swede rape that auto-pollinate poorly and in turnip rape cultivars that are nearly self-sterile.

When etiolated seedlings of maize and cowpea were subjected to a heat stress of 45 °C for 8 h and subsequently illuminated, there was a retardation in the rates of leaf elongation and chloroplast formation, but the rate of increase in dry weight was not affected. However, a heat stress of 45 °C for 16 h decreased all the three rates measured, the effects being more pronounced with the longer duration of stress in the case of leaf elongation and chloroplast formation. The cowpea seedlings were more sensitive to heat than the maize seedlings. The decreased yield (dry weight) in the 16 h treatment was due, at least partly, to the heat-induced retardation of the growth of the photosynthetic apparatus.

An investigation was carried out to detect and evaluate the oestrogenic activity of three successive cuts of Egyptian clover berseem (Tifolium alexandrinum). Changes in oestrogenic activity due to wilting, drying and fermentation were also studied.

Oestrogenic activity was higher (P < 0·01) in first-cut berseem (49–6 ug diethylstilbestrol equivalency (DES)/kg D.M.) than in the second (38·2 ug) and the third cuts (36·1 ug), and was decreased in the three successive cuts by wilting and dehydrating to 88% D.M. It was greater (P < 0·01) in the wilted berseem than the dried material of the second cut. Oestrogenic activity was increased (P < 0·05) in all cuts by fermentation, but it was higher (P < 0·01) in the fermented second cut than the other cuts.

An intake of 10 kg D.M. of silage would be equivalent to 0·98 mg DES, which have no adverse effects on production and reproduction.

The regrowth of Aberystwyth S. 22 Italian ryegrass, S. 24 perennial ryegrass and S. 37 cocksfoot was studied in field swards with and without applied nitrogen during the 21 days following a cut or grazing, there being a total of five periods of study at different times of year and in different years.

The dry-matter content of the harvested herbage deoreased by 4–8 percentage units on average from day 6 to day 18 of regrowth, supporting the evidence of earlier experiments with ryegrass and suggesting that a decrease at about this stage is typical. In the present experiments the same trend was evident after removal of surface moisture. Dry-matter content before removal of surface moisture was sometimes as low as 10%, which could adversely affect animal production. The water potential of fully expanded leaf blades was typically more negative on days 2 and 5 of regrowth than subsequently, so that the moderately high dry-matter content during the first week of regrowth seems to indicate some degree of moisture stress. Emerging leaves were less stressed than fully expanded ones during the very early stages of regrowth. Leaf water potential tended to be rather less negative in the cooksfoot than in the ryegrasses. The application of N reduced dry-matter content, but did not affect leaf water potential.

The digestibility of the harvested herbage was little affected by the stage of regrowth. The cocksfoot was less digestible than the ryegrasses. The application of N generally increased digestibility, particularly in cocksfoot.

The regrowth of Aberystwyth S. 22 Italian ryegrass, S. 24 perennial ryegrass and S. 37 cocksfoot was studied in field swards with and without applied nitrogen during the 21 days following a cut or grazing, there being a total of five periods of study at different tunes of year and in different years.

The proportion of cell content in the harvested herbage, as measured by neutral detergent, increased by nearly 9 percentage units from day 3 to day 18 of regrowth. The proportion of cell content as measured by acid pepsin also increased during regrowth, but to a lesser extent. The proportion of cell content in leaf blades of two age categories, as measured by neutral detergent, also increased during regrowth. The above increases in proportion of cell content were found in all three grasses. The increases were associated with increases in the proportion of crude protein in dry matter, which were only partially offset by reductions in the proportion of water-soluble carbohydrate. The broad pattern of change in N and nitrate-N content of Italian ryegrass herbage during regrowth in spring with different amounts of N applied, noted in earlier experiments, was confirmed and found to apply to perennial ryegrass and cocksfoot also. During a September-October period of study there was little sign of decline in nitrate-N content within the 21 days where N had been applied. Younger leaf blades had a rather lower nitrate-N content and a slightly higher total N content, on average, than, older blades. The application of N increased the proportion of crude protein more than it reduced the proportion of water-soluble carbohydrate and it increased the proportion of cell content. The increase in proportion of cell content was sufficient to explain the positive effect of N application on digestibility. The average proportion of total herbage N which was found in the cell wall fraction was about 12%.

There appeared to be a relationship between chemical composition and dry-matter content. The chlorophyll content of leaf blades increased during regrowth and was increased by N application. The experimental results on balance, particularly those for proportion of cell content, suggest an improvement in nutritive value of grass during regrowth up to about 3 weeks in contrast to the well-recognized decline in nutritive value where regrowth proceeds beyond about 3 weeks.

The effect of 96 h water deprivation on plasma proteins, blood and urinary electrolyte concentrations were studied in Barmer goats of the Rajasthan desert. The total plasma proteins, particularly albumin, increased significantly by water deprivation. Plasma potassium concentrations remained unchanged. The urinary K/Nu ratio increased considerably. There was a decrease in urinary sodium concentration after the 4th day of water deprivation.

Five experiments were made to observe the effect on nitrogen (N) utilization by young cattle of supplements of sucrose, glucose monohydrate (dextrose), and maize starch when added to basal diets of concentrates and straw. The supplements provided about 12% of the total intake of air-dry food. Twenty-four yearling Friesian heifers were used in each of two randomized block experiments to measure live-weight gain, and 6, 10 and 10 yearling Friesian steers in three changeover design experiments to measure N retention.

Rates of live-weight gain and N retention were increased by all the supplements amongst which no order of superiority in benefit conferred could be established. The improvement in N retention was associated with a marked reduction in urinary N and a small increase in faecal N with supplemented rations.

The proportions of volatile fatty acids (VFA) in rumen fluid were not affected by starch supplementation. Both sugars, but glucose more than sucrose, decreased the ratio of acetic to propionic acid, measured 2 h after feeding.

Statistically significant multiple linear regression equations were observed between N retained and intakes of N and digestible organic matter (DOM), both as absolute amounts with live weight as a further independent variate, and as intakes/unit metabolic body size. N2 and DOM × N as additional variates did not benefit the fit of the equations over the range of intakes studied.

Four hay-fed cows were used to study the effects on chewing behaviour of daily supplements of 3 kg whole barley grains, 3 kg whole oat grains or 2·2 kg rolled oats. Both whole grains increased the total time spent chewing by a similar small extent, probably due to a direct physical effect of the grain. The quantity of whole oat grains voided in faeces was lower than that of barley and it is concluded that the quality of chewing is more important than duration in breaking grains and ensuring their subsequent digestion.

An analysis of variance is developed for data from an incomplete mixture diallel experiment, where one subset w of the p genotypes are not grown together in mixtures. Estimation procedures and tests of hypotheses concerning relative yield totals and aggressivities are discussed, and an example is presented.

The production of flowers in perennial ryegrass (Lolium perenne) has been associated with a reduction in root relative to shoot growth and the post-flowering period with the death of roots. Any effect that reproductive development has upon the root system does not appear to adversely affect subsequent shoot growth. In the present experiments, vernalized plants restricted to root axes present prior to flowering showed little difference in herbage production and length of life compared with unvernalized plants similarly restricted. Flower production did, however, limit the ability of plants to initiate main root axes. It would seem unlikely that the mid-summer depression of herbage growth is due to the effect of reproductive development upon the root system.

Evidence was sought for genetic differences in the absorption or systemic use of copper by comparing responses in plasma Cu concentration to oral and intravenous Cu repletion. Lambs of the North Ronaldsay (Orkney), Scottish Blackface and Welsh Mountain breeds and crosses of these with the North Ronaldsay were used.

In two oral repletion phases average Cu intakes/kg live weight were 0·87 and 0·63 mg/week and similar for all breed groups. Plasma Cu concentrations of Scottish Blackface lambs showed little or no increase while those of North Ronaldsay lambs increased rapidly, and those of Welsh Mountain lambs increased moderately. The plasma Cu concentrations of the cross-breds increased more rapidly in the first than in the second phase; their rate of change lay between the pure breeds but was closer to that of the North Ronaldsay in the first phase.

The rates of increase in plasma Cu concentration during intravenous repletion were relatively uniform for the different breeds and crosses except the Blackface which showed a lower rate. It was concluded that the large differences between groups in response to oral Cu repletion were largely attributable to differences in the efficiency of Cu absorption.