The results of 80 calorimetric experiments with sheep and cattle, mostly conducted in Scotland, were analysed using a generalization of the Mitscherlich equation R = B(l–exp(–pG))–l, where R is daily energy retention and G daily gross energy intake, both scaled by dividing by the fasting metabolism. The relations between gross energy and metabolizable energy were also examined. Methods of fitting the Mitscherlich equation and the errors associated with it are presented.

It is shown that the gross energy of the organic matter of feed can be estimated from proximate principles with an error of ±2·3% (coefficient of variation) and that provided different classes of feed are distinguished, the metabolizable energy of organic matter can be estimated from gross energy and crude fibre content with an error of ±6·9%. Parameters of the primary equation made with cattle agreed with those made with sheep and there was no evidence of non-proportionality of responses on substitution of feeds in mixtures.

The efficiency of utilization of gross energy for maintenance and for body gain of energy was related to the metabolizability of gross energy and, in addition, to fibre or to protein content. Prediction equations are presented which describe these relationships.

It is shown that the primary equation can be manipulated to express a number of biological concepts and that its two parameters B and p can be simply derived from estimates of the two efficiency terms for maintenance and production.

The results are discussed in relation to the design of feeding systems for ruminant animals and to the derivation of optima in their feeding.

Eight experiments, comprising four randomized-block feeding trials each with 20–45 animals and four changeover-design nitrogen (N) balance trials each with 6–10 animals, were used to study the effect of the addition of formaldehyde to fishmeal and to casein, of severe heating of fishmeal, and of tannin treatment of a mixture of vegetable protein-rich foods on the utilization of N for growth. Added in moderate amounts to rations demonstrated within the experiments to be deficient in N, quantities, but not the preparations, of N in the diet were critical to growth save at very low N intakes when the untreated foodstuffs were used more efficiently. Additional energy given in isonitrogenous rations increased growth, reducing N losses in the urine.

Forty Large White × Wessex pigs were fed from 7 to 27 kg live weight, on diets containing either 28 or 14% crude protein. From 27 to 113 kg live weight the pigs were fed a common diet ad libitum. Pigs from each treatment were killed at 27, 54, 82 and 113 kg live weight and the chemical composition was determined. From 7 to 27 kg and from 27 to 113 kg live weight, daily gain, food intake and food conversion efficiency were similar for the two treatments.

At 27 kg, pigs on the lower protein diet were fatter and contained less lean tissue. Between 27 and 54 kg live weight the pigs previously on the higher protein diet deposited a much greater amount of fat than the pigs on the lower protein diet, so that by 54 kg the pigs initially on the lower protein contained less fat. At 82 and 113 kg live weight the pigs given the lower protein diet initially also tended to contain less fat. These findings are discussed with particular reference to the voluntary energy intake of growing pigs.

An experiment at Saxmundham, Suffolk, during 1974–6, tested late sprays of a liquid N-fertilizer (ammonium nitrate/urea) supplying 50 kg N/ha, and a broad spectrum fungicide (benomyl and maneb with mancozeb) on winter wheat given, 0, 50, 100 or 150 kg N/ha as ‘Nitro-Chalk’ (ammonium nitrate/calcium carbonate) in spring

Mildew (Erysiphe graminisf. sp. tritici) was most severe in 1974. It was increased by N and decreased by the fungicide in both 1974 and 1975, but was negligible in 1976. Septoria (S. nodorum) was very slight in 1974 and none was observed in 1976. It was much more severe in 1975, but was unaffected by the fungicide perhaps because this was applied too late.

Yield and N content, number of ears and leaf area index were determined during summer on samples taken from all plots given 100 or 150 kg N/ha in spring; each was larger with 150 than with 100 kg N/ha. The effects of the liquid N-fertilizer on yield and N content varied, but leaf area index was consistently increased. None was affected consistently by the fungicide.

Yields, percentages of N in, and amounts of N removed by grain and straw were greatly and consistently increased by each increment of ‘Nitro-Chalk’. Yields of grain were increased (average, 9%) by the liquid fertilizer in 1974 and 1975, and most where most ‘Nitro-Chalk’ had been given, but not in 1976 when the wheat ripened in July; however, both the percentage of N in and the amount of N removed by the grain were increased by the liquid fertilizer each year. The fungicide increased the response to the liquid N-fertilizer in 1974, but not in 1975 when Septoria was not controlled, nor in 1976 when leaf diseases were virtually absent.

The weight of 1000 grains was increased by each increment of ‘Nitro-Chalk’ in 1975 but only by the first one (50 kg N/ha) in 1974 and 1976; it was very slightly increased by the liquid fertilizer and by fungicide each year.

An experiment comparing the yield at various stages of continuous wheat growing on heavy land, using two varieties and two rates of application of nitrogenous fertilizer, is described and the results from 1963 to 1974 discussed.

The yield of the second wheat crop was substantially less than that of the first following oats which followed beans, but there were no consistent yield differences between the second and later crops.

The major disease present was eyespot, but the differences in yield between Cappelle-Desprez and Hybrid 46 were little affected as wheat growing continued.

Increasing nitrogen application from 63 to 126 kg N/ha did not reduce the differences between first and later wheat crops.

Plant and nodule development and nitrogen fixation were studied in two climbing cultivars of Phaseolus vulgaris, grown in monoculture, or associated with two maize populations differing in growth characteristics.

Bean cultivar P590 showed similar plant and pod fresh weight development in monoculture and when associated with a vigorous landrace maize, interspecific competition becoming significant only 92 days after planting. Nitrogen (C2H2) fixation in this cultivar was greatest 68 days after planting and declined rapidly thereafter, showing no significant differences between monoculture and associated plantings. When the bean cultivar P526 was associated with the landrace maize, plant development was depressed as early as 50 days after planting. While slight inhibition of nitrogen fixation, specific nodule activity (SNA) and nodule carbohydrate content was also observed at this time, it could not be concluded that such inhibition was definitely due to the associated planting.

Association with an improved maize, amarillo subtropical, did not affect plant development in P590 but did decrease growth of P526 at the 80 and 92 day harvests.

Two experiments were carried out to examine the effects of restricted food access on the voluntary food intake of pigs given diets of varying energy content or palatability. Where pigs were offered access to food for a restricted time period each day, the voluntary food intake was reduced in relation to the length of access allowed. Compensation was slow, particularly where a low-energy diet was fed. Younger pigs (35–45 kg) compensated faster than heavier pigs (100–110 kg). The responses of the heavier pigs appeared to be similar to those reported for genetically obese rats in their strong reaction to diets of different energy content or palatability.

Observations were made on mating behaviour and reproductive performance during the puberal period in 61 well-grown Perendale (Cheviot × Romney) ewe lambs. In four animals, the first oestrus (as indicated by raddle marks) was not accompanied by ovulation, and three other lambs, though marked by the rams, were not inseminated.

The behavioural responses to a ram, of ewe lambs experiencing oestrus for the first and second times, showed many signs of inadequacy by comparison with those of mature ewes. Individual ewe lambs and mature ewes in oestrus were exposed to a ram in a pen for 3 h, and their responses were ranked on a scale of 1 (full adult response) to 5 (weak response). Of mature ewes 95% scored 1, compared with only 27% of ewe lambs. Across the lambs 59% scored 3 or more, indicating failure of some aspects of the courtship sequences which are required to sustain and reinforce the ram's interest. In a paddock-mating system many lambs showed a strong tendency to disassociate themselves from the rams after each courtship and mating sequence. Consequently there was little evidence of harem formation. Fifty-six per cent of services came in the first 2 h of oestrus, only 14% after the 6th hour and none after the 11th hour.

Duration of the first oestrus in lambs was 18·4 h compared with 29·3 h in mature ewes. Mating the 61 ewe lambs over the first three cycles after puberty resulted in 38 of them being pregnant with 46 foetuses at autopsy in mid to late pregnancy. The success rate did not differ between cycles.

Experiments were made in a glasshouse and in the field to estimate the effect of weed competition on cowpea performance.

In the glasshouse experiment, plant height, number of nodes, green leaves, peduncles, weight of poda and seeds of cowpea were decreased by competition from Euphorbia heterophylla and the decrease was greater with increasing density of the weed associate. Generally cowpea did not respond to application of fertilizers. In the field experiment, competition from the natural weed flora affected the number of days to 50% flowering and yield components of the four cowpea varieties studied. The yield of the climbing variety, Dinner, was least affected by competition whilst the semi-erect variety, Ife brown, was the most affected.

Each of the three uppermost leaves of wheat canopies studied in 1975 and 1976 showed a downward movement after its emergence. The variations with time of leaf angle were greatest in the flag leaf. Genotypes differed markedly in the rate of change with age in flag-leaf angle. Leaf curvature did not vary with age. There were differences between years in the rate of leaf movement, but cultivars ranked roughly the same in terms of leaf angle in each year. Grain yield per hectare was not related to leaf angle change. Most of the higher-yielding genotypes included in the study had straight leaves, the correlation between curvature and yield being —0·30 in 1975 and —0·60 in 1976.

Field investigations were undertaken during the winters of 1971–6 to study the grain yield responses of lentil cultivars to seed inoculation with single and mixtures of Rhizobium strains. An effective symbiosis and consequent increase in the grain yield was associated with the efficacy of the strain. Inoculation with a superior strain produced 23–32 % more grain than no inoculation on loamy-sand soil and 46–90% more on sandy-loam soil.

In separate studies comprising inoculation and nitrogen treatments, the seed treated with an effective Rhizobium strain gave on average 43% more yield than no inoculation and the application of 25 kg N/ha alone gave the same yield as inoculation. Rhizobium inoculation plus 20 kg N/ha was the best combination for maximum yield under both loamy-sand and sandy-loam soils.

The effect on palatability of crossing Angus with other beef breeds has been studied. Purebred Angus and Jersey × Angus crosses were significantly more tender and of a higher general acceptability than the Simmental × Angus and Limousin × Angus crosses. The possible cause of tenderness differences amongst the cross-breeds is discussed.

Neem (Azadirachta indica A. Juss syn. Melia azadirachta Linn.) seed cake boiled with 8 g caustic soda/kg cake in 2·51 of water for 30 min yielded a product which was palatable to cattle unlike untreated neem seed cake which is bitter, foul smelling and wholly unpalatable to cattle.

Two experiments were made on calves to compare the performance of two groups of animals; one group (control) fed on a standard concentrate mixture consisting of 33% groundnut cake, 34% maize and 33% wheat bran and the second group (experimental) on 50% alkali-treated neem seed cake, 33% groundnut cake and 17% maize, the roughage being the same in both the groups.

The results showed that the dry-matter intake/100 kg body weight of the animals did not differ significantly (P > 0·05) between the two groups but digestibility of dry matter and total carbohydrates and the growth rate was significantly lower (P < 0·05) in the experimental group. The digestibility of crude protein and ether extract and the adjusted balances of nitrogen, calcium, phosphorus and sulphur remained similar (P > 0·05) in the two groups. The reduction of the growth rate in the experimental group could be accounted for by the lower total digestible nutrients (TDN) intake and there was no difference (P > 0·05) in the serum icteric index, blood inorganic phosphorus and serum alkaline phosphatase activity in the two groups.

It is concluded that alkali-treated neem seed cake has great potential as a cattle feed and alkali treatment removes either completely or very largely the toxic principles present in neem seed cake.

This research was conducted to determine the effects of applying N-fertilizer to standard and semidwarf spring wheat varieties on the components of grain yield, and especially on the ability of tillers to develop and produce ears under semiarid conditions. For two growing seasons at Mandan, North Dakota, tillers were identified and tagged according to the leaf axil from which they originated. The survival and development of these tillers, identified as M, T1, T2, and T3 for main stem and tillers from axils of first, second and third true leaves respectively, were observed and measured from emergence to maturity. N-fertilizer was applied at 0, 50 and 270 kg N/ha annually, representing deficient, adequate and excessive N supply.

N-fertilizer application increased grain yield of both varieties, with the increase between 50 and 270 kg N/ha being significant for the standard variety only. Most of this response to N resulted from an increase in the number of ears/ha, arising from reduced mortality of tillers, particularly T2 and T3 tillers during the latter part of the season when water was limited. For a given variety, grain production by M and by T1 tillers was seldom affected by N treatment. Although data were analysed by several means, all results indicate that improved N nutrition enables the later-developing tillers to survive and produce ears more competitively. Final grain yield was closely correlated with N content of a given tiller at the tillering stage, and to dry weight of individual tillers at both tillering and heading. Order of tiller had no appreciable effect on N content of grain. The proportion of final grain yield originating from M decreased from about 60% without N to about 36% for 270 kg N/ha, primarily because of increased survival and production from T2 and T3 tillers following the application of N-fertilizer.

Wool samples were collected from 39 rams representing five breed groups of sheep: Merino (M), Ossimi (0), and the crosses between them, viz. ¾ Ossimi–¾ Merino (¾ O), ½ Ossimi–½ Merino (½ O) and ½ Ossimi–¾ Merino (¼ O) maintained at Sakha Experiment Station, Kafrelsheikh, Egypt, with the objectives of detecting the effect of the seasonal changes in normal light rhythm and temperature on wool fibre length and diameter. Animals were divided into two light treatments groups, the first consisting of four animals from each breed kept under continuous dim light conditions throughout the year and the second of three animals from Ossimi and four from each breed group kept inside an open pen free to sunlight and shade zones under daylight rhythm throughout the year. It was found that fibre length as well as fibre diameter in normal light exceeded that in dim light except in winter time. Breed groups showed different responses to the absence of light especially the Ossimi and the ¾ O whose fibre lengths were most affected. The breed groups had larger fibre diameters in normal light than in dim light except Merino and ¼ O. Seasonal changes in temperature had a highly significant effect on fibre length but not on fibre diameter. Higher temperature coincided with lower increases in fibre length. Season to season variation in wool growth seemed to suggest that the number of light hours per day and atmospheric temperature counteracted each other resulting in a non-significant seasonal pattern.

Soils at Rothamsted receive approximately 4 kg NH3-N/ha/year through dry deposition of atmospheric ammonia. The value is low compared with other nitrogen input processes and reflects the low concentrations of ammonia in the atmosphere. Rainfall is a major factor limiting dry deposition as it removes large amounts of ammonia from the atmosphere. Dry deposition of ammonia is a relatively unimportant source of combined soil nitrogen compared with other natural and artificial sources.

Winter wheat varieties of contrasting height were grown in a series of yield trials to investigate their response to nitrogen fertilizer. The treatments also included application of fungicides and the use of nets to prevent lodging. The varieties were ‘semidwarfs’ based on the Norin 10 genetic factor Rht2 or taller ‘conventional’ varieties, all well adapted to the U.K. environment. The average response of the semi-dwarf varieties was similar to the conventional and there were varietal differences within each group. There was a marked tendency for the newer varieties to be more responsive but the varietal differences were not consistent between trials, the occurrence of powdery mildew (Erysiphe graminis) being a major factor. When this disease was prevalent, response to nitrogen was greatest in resistant varieties and increased by application of fungicides. In farm practice the optimum rate of nitrogen application for a variety will depend on its physiological response, resistance to lodging and resistance to diseases if these are not controlled by fungicides. No evidence was obtained that the gene Rht2 necessarily confers a greater response to nitrogen.

Total sprout length and the length of the longest sprout were shown to be the most universally useful measurements to estimate sprout development in batches of potato tubers. A good estimate of sprout weight was also derived from measurements of total sprout length. There was a good linear relationship between total sprout length and initial tuber weight but the relationship varied considerably with the time of measurement and the temperature of storage.

It is suggested that if sprout measurements are to be used to predict the field performance of a batch of tubers the changing pattern of sprout vigour with time needs to be more closely understood.

The Br content of soils and herbage from sites in north-west Pembrokeshire was determined. Topsoils had a range of Br contents from 10 to 515 μg/g, with a mean of 54 μg/g, subsoils ranged from < 1 to 455 μg/g, mean 47 μg/g, and herbage samples from 5 to 157 μg/g, mean 45 μg/g.

The topsoil Br content can be related to the loss on ignition and drainage status of the soil; the topsoil Br/loss on ignition ratio becomes smaller with increasingly poor drainage. It was found that the Br distribution in the soil profile is also related to drainage status, the topsoil/subsoil Br ratio increasing with increasingly poor drainage.

There is no clear relationship between soil Br and the amount of the element taken up by the herbage at the same sites.

An experiment to study the effect of sowing time (21 October, 5 November, 20 November, 5 December and 20 December), seed rate (5, 7·5 and 10 kg/ha) and application of nitrogen fertilizer (0, 20, 40 and 60 kg N/ha) was conducted at the Punjab Agricultural University, Ludhiana, on a loamy sand soil during the winter seasons of 1974–5 and 1975–6. The delay in sowing from 21 October to 20 December produced shorter plants with fewer spikes. The crop sown on 21 October using 7·5 or 10 kg seed/ha and supplied with 20 or 40 kg N/ha gave better yield than those of later sowings.