bluuebunny/crossref_metadata_2025 huggingface dataset:
On the capillary forces in an idealized soil
Authors: Allberry E. C.
Published: March 2009

1. The attraction between spheres, due to surface tension forces, in a lenticular drop between them is calculated for spheres in contact and at increasing separations up to the point of rupture of the drop. Hence the work of separation of the spheres is calculated.

2. Experimental measurements confirm the validity of these calculations, down to very small drop sizes, where it is likely that the failure is in the experimental method. As predicted by Fisher, the force decreases with increasing drop size, while the work of separation increases. Since, however, it is shown that the smaller lenticels are more easily ruptured, no discrimination is provided between the differing explanations of Haines and Fisher of measurements made with the Atterberg apparatus for measurement of soil cohesion.

An experimental verification of the validity of Fisher's calculation of the pressure deficiency inside the drop is also given.

3. It is pointed out that these results depend on the geometry of the system; types of contact other than that of spheres will show different behaviour. Hence generalizations about the behaviour of a real soil, based on an idealized soil of packed spheres, may lead to erroneous conclusions.
The hydrolytic examination of plant cellulose isolated by the method of Druce and Willcox
Authors: Druce Edward , Willcox James Stuart
Published: March 2009

The cellulose isolated by the method of Druce & Willcox (1949a) has been examined by a hydrolytic procedure. The results confirm the high ‘hexosan’ content of the residues.

The recovery of ‘hexosan’ from ‘bran cellulose’ has been shown to be very low (58%), and it has been demonstrated that the presence of large amounts of phytic acid is not responsible for this. It is suggested that ‘bran cellulose’ contains components which do not yield reducing sugars on hydrolysis.
Evaporative cooling in fowls
Authors: Hutchinson J. C. D.
Published: March 2009

Part I

1. Reasons are given for expressing the evaporative loss of the resting fowl in the following way:

where C is a constant, f(tr) is a function of rectal temperature, ps is the vapour pressure of a saturated atmosphere at the temperature of the evaporative surfaces, and pa is the vapour pressure of the ambient air.

2. It was found that for practical physiological purposes the rectal temperature may be taken as that of evaporation, from which ps, is deduced. The real temperature of evaporation is probably a few degrees below this, as would be expected.

3. It is concluded from this, that atmospheric humidity hinders the evaporative cooling of fowls less than that of men. Therefore, a farmer cannot estimate the comfort of his fowls in hot weather from his own subjective impressions. The experiments also explain theoretically, why evaporative coolers for poultry houses are successful in practice.

PART II

1. The evaporative loss over a wide range of rectal temperature is plotted in Fig. 1. By applying formula (ii) it was possible to prepare curves for 28 and 5 mm. Hg atmospheric vapour pressure. These vapour pressures are near the extremes of absolute humidity, which fowls naturally encounter in hot climates. Brown Leghorns were used, and it is pointed out that the results with other breeds might not be quite the same.

2. It was calculated that part of the increase in evaporative cooling in hyperthermia is due to the rise in temperature of evaporation. At high rectal temperatures its importance is comparable with that of increased pulmonary ventilation.

3. There was no significant sex difference in the relation between evaporative loss and rectal temperature (Fig. 2).

4. The maximum possible evaporative cooling of fowls in equilibrium with their environment was 41 Kg.cal./sq.m./hr. at a humidity of 28 mm. Hg atmospheric vapour pressure and 64 Kg.cal./sq.m./hr. at 5 mm. This is much less than the maximum attained by man and somewhat less than that of the dog. Although evaporation per unit surface area was less than in the cow, it was much the same in relation to metabolic requirements.

5. Next, certain discrepancies are considered in the relation between rectal temperature and evaporative loss (Tables 3–5). At rectal temperatures near the panting threshold evaporation was found to be greater at high air temperatures and during the night. For the night tests fragmentary data only were available. These findings are tentatively attributed to a lower normal body temperature, which lowered the panting threshold.
Growth analysis of the domestic fowl: III. Effect of plane of nutrition on carcass composition of cockerels and egg yields of pullets
Authors: Wilson P. N.
Published: March 2009

1. 101 Rhode Island Red × Light Sussex chickens have been made to conform to four major changes in the shape of their growth curves from hatching to twenty-four weeks, by control of their plane of nutrition. The four treatments (HH), (LH), (HL) and (LL), allowed comparisons to be made between birds of the same age, but different weights. As the main concern has been to find the essential nature rather than the precise extent of the effects produced by different planes of nutrition, the treatment differences were made as extreme as possible without allowing the rations to become unbalanced.

2. Certain individual organs and tissues, the gonads, thyroid and thymus, and the combs and wattles have reacted differentially to the contrasted treatments when compared on a basis of equal body weight. All the organs, with the exception of the very early maturing eyes and heart, have reached significantly different weights on the basis of equal age. Those organs which have yielded treatment differences judged on both the basis of equal weight or equal age have all been late maturing. The results therefore indicate that the effect of treatment has been to restrict the development of the later maturing parts in the case of the low-plane birds, and to accelerate the development of these organs when the birds are reared on the high plane. The results are insensitive to any differential effects which may have been brought about in the early maturing organs, since the design of the experiment did not allow of the slaughtering of birds at equal weight but only at equal age. The means of Comparison of differences at equal weights was the less precise method of ascertaining whether the high- and low-plane regression lines of weight of part to total weight of bird differed significantly the one from the other.
The presence of root-inhibiting substances in cow urine and the cause of urine burn
Authors: Doak B. W.
Published: March 2009

1. A study has been made of the cause of urine burn in pasture.

2. It has been shown that urine burn could occur under dry soil conditions due to the osmotic pressure effects of the urine.

3. All seeds present in the urine-affected soil are killed.

4. An inhibitor of root growth, to which clover roots are especially sensitive, is present in the urine of cows and sheep.

5. This inhibitor, which is not heteroauxin, is acid in character and is destroyed in soil in a few days.

6. It is suggested that the inhibitor is an inhibitor-auxin complex, of which the auxin portion might be heteroauxin. The possibility that the inhibitor is an auxin precursor is discussed.

7. It is contended that the reduction of clover growth relative to grass growth in a urine patch is not simply the result of shading due to increased grass growth.

8. The root inhibitor, the temporarily high pH, the presence of free ammonia, and the high concentration of ammonium ions may be important factors in the reduction of clover growth.
Chewing behaviour of hay-fed cows given supplements of whole barley and oat grains
Authors: Morgan C. A. , Campling R. C.
Published: March 2009

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.
The effect of NaCl or NaHCO3 on digestion in the stomach of weaned calves
Authors: Kellaway R. C. , Beever D. E. , Thomson D. J. , Austin A. R. , Cammell S. B. , Elderfield Marian L.
Published: March 2009

The response to dietary inclusion of NaCl or NaHC03 at 42 and 60 g/kg (18 g Na/kg) respectively was examined in relation to rumen fermentation and the flow of nutrients to the duodenum of calves.

Measurements were made with four calves on each diet at 8 and 11 weeks of age: weaning having taken place at 5 weeks of age.

Osmotic pressure, pH, total VFA concentration and molar proportions of VFA were not significantly affected by the treatments imposed. Rumen dilution rate was increased by 28% on the NaHCO3 diet compared with the other two diets but this difference failed to achieve statistical significance. Mean duodenal flows of organic matter, modified acid detergent fibre and total amino acids were 0·52, 0·72 and 1·25 of the respective dietary intakes and were not significantly affected by the treatments imposed. NaHCO3, however, significantly increased the supply of α-linked glucose polymer to the small intestine (15% of dietary intake) compared with the control (4%) and NaCl (6%) diets. The results demonstrated that NaCl and NaHCO3 had small effects upon the digestion within the rumen of young calves with specific reference to flow of nutrients to the proximal duodenum. It is suggested that the stimulatory effect of NaHC03 on food intake and performance of calves may be attributable to an increase in rumen buffering capacity, and some indication of an increase in the fractional outflow rate of water and possibly particulate matter from the rumen.
Effects of the amounts of phosphate fertilizer, and of the proportions of water-soluble phosphate in the fertilizers tested on the phosphorus nutrition of sorghum
Authors: Govil B. P. , Prasad R.
Published: March 2009

A field experiment was made with sorghum hybrid CSH-1 during the rainy seasons of 1968 and 1969 on a sandy loam soil to study the influence of amounts and sources of phosphate fertilizer on phosphorus nutrition. Concentration of P in the crop and uptake increased with increasing amounts of phosphate and with increasing proportions of water-soluble P in triple superphosphate-dicalcium phosphate and triple superphosphate-rock phosphate mixtures. Relative effectiveness values were calculated from P uptake at harvest by a multiple regression method. For triple superphosphate, nitrophosphate (30% water soluble P), dicalcium phosphate and rock phosphate (from Jordan) the values were respectively, 100, 74, 61 and 22.
Deposition of sulphur from the atmosphere and the sulphur balance in four soils under grass
Authors: Bristow A. W. , Garwood E. A.
Published: March 2009

The sulphur balance in eight lysimeters containing four different soils under grass was examined over a 4-year period during which the annual mean concentration of sulphur dioxide (SO2) in the air at the site decreased from 30 to 14 μg/m3. The amounts of sulphur harvested in the grass and lost in drainage were set against additions in fertilizer, rainfall and from dry deposition. A decline in annual dry-matter yield was accompanied by a decrease in the concentration of sulphur in the herbage and an increase in the ratio of nitrogen to sulphur. It was concluded that atmospheric sources and soil reserves may become insufficient to meet the sulphur requirement of grassland.
Studies on the effect of humidity on the hatchability of hen's eggs I. The determination of optimum humidity for incubation
Authors: Robertson I. S.
Published: March 2009

An attempt to find the effect of humidity on hatchability and at the same time indicate the optimum humidity for incubation was carried out by subjecting eggs in one incubator to various levels of humidity and comparing the results with eggs hatched as a Control in a second incubator of identical design.

Hatchability was depressed by excessively high levels of humidity but in general satisfactory hatches can be obtained between 40 and 70% R.H.

The pattern of mortality, the incidence of Malposition I but not Malpositions II, III and VI were affected by humidity level.

The optimum level found, c. 50% R.H., was lower than the previously accepted optimum and may be accounted for by a number of factors including egg size.
A comparison of wheat and fine wheat offal in the rations of fattening pigs
Authors: Braude R. , Townsend M. Jill , Harrington G. , Rowell J. G.
Published: March 2009

1. A co-ordinated trial has been carried out at twenty-two centres to compare the value of wheat, crushed or ground, with that of fine wheat offal (weatings) when fed in equal amounts in the rations of growing pigs.

2. Pigs fed the wheat rations grew faster (8·7% improvement for crushed wheat, 6·3% for ground), had. more efficient food conversion (9·0 and 6·5%) and yielded heavier carcasses for a given final live weight (1·4 and 1·3%) than pigs fed weatings but were fatter at the shoulder (5·6 and 7·5%) and the loin (11·2 and 13·1%); all these effects were highly significant. Differences in length of carcass were not significant.

3. Improvements in growth rate and food conversion were significantly greater with crushed wheat than with ground wheat. None of the other differences between crushed wheat and ground wheat was significant.

4. An economic appraisal has been made which shows that, on the basis of certain assumptions, the feeding of wheat would have resulted in higher profit per year than the feeding of weatings under the price structure and system of grading prevailing during the period of the experiment.

5. Changes in the price structure (average price of bacon pigs, differentials between grades and cost of wheat and weatings), in the average quality of the carcasses (length of the carcass and fat at the shoulder and loin) and in the size of treatment effects on food conversion, all have a substantial effect on relative profits. The appraisal suggests, however, that feeding wheat would be more profitable than feeding weatings when the above changes were extremely severe.
Genotypic and environmental effects on curd weight of autumn-maturing cauliflowers
Authors: Crisp P. , Kesavan V.
Published: March 2009

Twelve genotypes of cauliflower were grown in two seasons from six seedling propagation treatments in three sequential sowings. There was a high genotypic component of variation for curd weight, indicating that this character can be improved by breeding. A large genotype × environment interaction included genotypic differences in stability to the environment, notably in the self-compatible genotypes. Mean curd weight and stability of genotypes to the environment for this trait were uncorrelated, indicating that high weight and high stability could be bred into a single variety.
Tiller development and yield of standard and semidwarf spring wheat varieties as affected by nitrogen fertilizer
Authors: Power J. F. , Alessi J.
Published: March 2009

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.
An assessment of dairy bull station progeny tests carried out at two centres in Britain
Authors: Pearson Lucia
Published: March 2009

1. Station progeny tests of twenty-four Ayrshire and twenty-two Friesian bulls were carried out by the British Oil and Cake Mills Ltd. at two centres in Britain between 1953 and 1961. The tests followed the Danish pattern: groups of ten to seventeen daughters were brought to the station approximately 6 weeks before first calving and milked under standardized conditions for an average of 270 days.

2. The place of the station system in modern dairy practice in Britain and abroad was discussed.

3. Earlier results had suggested that milk yield, butterfat percentage, S.N.F. percentage, milking rate and conception interval should be taken into account in a progeny test.

4. Correlations were calculated between the bulls 305-day field ratings for milk yield and fat percentage and their 90- and 270-day station assessments. Possible reasons for the discrepancies were investigated.

5. The selection system employed did not appear to lead normally to the choice of heifers whose dams' milk yield or fat percentage differed from the recorded averages for the breed. In two groups of special cases, deviations were apparent but the effect on the accuracy of the station test was shown to be small. It was concluded that bias due to maternal genetic variation was unlikely to be serious in the general case.
Studies on the nitrogenous manuring of winter wheat
Authors: Beveridge J. L. , Jarvis R. H. , Ridgman W. J.
Published: March 2009

1. The problem of when to apply nitrogenous top-dressings to winter wheat has nover been satisfactorily solved. Detailed field and glasshouse experiments on the effects of nitrogenous manuring on the development of wheat plants, and a number of other experiments involving the nitrogenous manuring of wheat are described and the results discussed.

2. Partial regression coefficients of grain yield on individual components of yield are used to show how variable is the relationship between grain yield and the components of yield.

3. It is concluded that field experiments are never likely to determine an optimum time for nitrogen top-dressing because of the unpredictable relationships between individual yield components and grain yield, and because of the variation in response to nitrogen introduced by seasonal and environmental factors.
The nutritional value of some tropical grasses
Authors: Grieve C. M. , Osbourn D. F.
Published: March 2009

1. Twenty feeding and digestibility trials were carried out on seven tropical grasses to determine their nutritional value at different stages of growth, and to study their suitability as possible pasture grasses.

2. Content of crude protein was relatively high at immature growth stages of the forages, and declined rapidly with the onset of flowering.

3. Digestibility of dry matter and gross energy increased in most of the forages tested to the 5-week stage of regrowth but declined rapidly in mature stages of forages tested at 6 or 8 weeks of regrowth. Digestibility of crude protein declined with increasing maturity of the forages.

4. The Nutritive Value Index of each forage was highest at four or five weeks of regrowth. The optimum time to graze the forages tested would occur between 4 and 5 weeks of regrowth, at the stage when flowering commences. This would combine high yield of forage with high nutritional value.
The utilization of Hyparrhenia veld for the nutrition of cattle in the dry season II. Veld hay compared with in situ grazing of the mature forage, and the effects of feeding supplementary nitrogen
Authors: Smith C. A.
Published: March 2009

Three methods of utilizing the natural Hyparrhenia grasslands for the dry-season nutrition of ranch cattle were tested in grazing trials. The feed regimes were:

(A) Late-cut veld hay plus aftermath grazing.

(B) The accumulated, seasonal growth of mature grass left as ‘standing hay’ for dry-season grazing.

(C) A combination of both practices in which half the area was cut for hay, and half left as ‘standing hay’. These treatments were compared with and without the feeding of supplementary protein.

Mature Hyparrhenia veld whether cut for hay or left as ‘standing hay’ was a stemmy, low-quality forage deficient in protein. The qualitative deficiency was such that all unsupplemented treatments were equally ineffective in preventing large cattle weight losses in the dry season.

The only significant treatment effect was that due to feeding a protein supplement. Otherwise, there were no differences between the three managements, i.e. there was no marked benefit from conserving forage as veld hay compared with in situ grazing of the standing grass.

The voluntary intake of veld hay was low; and with heifers, declined to negligible amounts. The feeding of supplementary nitrogen, either as protein or urea, increased the daily hay intake by 140%. As a result, a diet deficient in energy was altered into a productive ration, with consequent cattle weight gains.

Although the cattle preferentially sought-after, and grazed the aftermath from late-cut veld hay; its practical nutritional value was slight, and was not reflected in cattle weight gains.
A score card for lamb and mutton carcasses
Authors: Starke J. S. , Joubert D. M.
Published: March 2009

A score card is suggested for the judging of lamb and mutton carcasses. To apply the score card, measurements have to be recorded on length of leg (F), circumference of buttock (D), width (A) and depth (B) of ‘eye muscle’ (m. longissimus dorsi) and depth of back fat (C) and rib fat (J). In addition, visual judgement is required of fat covering on leg (E), marbling (G) and texture and colour of eye muscle (H). Points are deducted beyond an optimum weight which differs for lamb and mutton carcasses respectively.
Factors affecting the water and food intakes of European and zebu-type cattle
Authors: Horrocks D. , Phillips G. D.
Published: March 2009

1. The water and food intakes of sixteen grade Shorthorn and Boran zebu steers have been studied.

2. A difference has been shown in the water requirements of Shorthorn and Boran cattle.

3. Modest supplementation with salt, of animals on an otherwise sodium deficient diet, had no significant effect on either water or food consumption.

4. Differences in environmental temperatures are suggested to explain the higher intake of water in one of the experimental periods. The increased water intake for the Borans was less than half that for the Shorthorns, only the increase for the latter being significant.
The intake of Pangola grass (Digitaria decumbens, Stent.), under wet- and dry-season conditions in Trinidad
Authors: Butterworth M. H. , Groom C. G. , Wilson P. N.
Published: March 2009

The intake of dry matter from a pasture of Pangola grass by lactating dairy cows was measured. The chromic oxide administration technique was used. It was shown that the intake of dry matter was significantly higher in the dry season than in the wet. Reasons for this were discussed. An assessment of the nutrient intake of the animals was made and it was concluded that if the requirements of cattle in temperate climates was taken as a guide, this was adequate for at least maintenance and production of 1½ gal. per day of milk in the wet season. Under dry season conditions the intake of total digestible nutrients was adequate for the same level of production, but the digestible protein level was considerably below requirement. It was therefore concluded that supplementation with protein concentrates in the wet season was unnecessary save for high-yielding cows, but that all cows required concentrates during the dry season conditions of the experiment.
Grass as a food for the calf I. The value of cut grass in the diet of the unweaned calf in comparison with hay and concentrates
Authors: Chambers D. T.
Published: March 2009

1. The relative nutritive value to the unweaned calf of concentrates-with-hay and of grass cut from pasture in spring was measured.

2. No significant difference was found in liveweight gain or increase in body measurement between calves receiving these feedingstuffs.

3. There was some indication that rumen development, as measured by belly girth, may have been affected by the diet.

4. There was no interaction between the type of dry food consumed and the milk ration or housing conditions.

5. Results indicate that good quality grass, free from parasitic infestation, is capable of replacing hay and concentrates in the diet of the unweaned calf.
Grass as a food for the calf II. The effects of feeding grass or concentrates-with-hay during the pre-weaning period on the intake and utilization of grass during the post-weaning period
Authors: Chambers D. T.
Published: March 2009

1. Calves which had been reared for 12 weeks on three milk feeds and either cut grass or concentrates-with-hay, were introduced to an all-grass diet when weaned.

2. Eight animals were kept indoors and fed herbage cut from paddocks grazed by nineteen similar calves.

3. After an initial period of about 2 weeks there was a tendency for grass-reared calves to make slightly better live-weight gains.

4. No difference could be shown in the intake of herbage dry matter by these groups of calves.

5. There was little indication that grass-reared animals digested their food more efficiently. It appeared that they converted grass to animal tissue better, but further study is required to substantiate this.
A method of estimating the underlying input–output relations for beef cattle from large-scale experimental trials
Authors: Newbery D. M. G.
Published: March 2009

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.
The effect of route of dosing and method of estimation of tritiated water space on the determination of total body water and the prediction of body fat in sheep
Authors: Smith B. S. W. , Sykes A. R.
Published: March 2009

Eight mature female sheep were offered a ration which maintained body weight constant during a 20-week period. During the final 10 weeks a comparison was made in each animal of the pattern of equilibration and urinary losses of tritiated water during 8 h after dosing by four different routes. These were intravenous, intraperitoneal, intraruminal and a combination of the intraperitoneal and intraruminal routes. Tritiated water spaces were calculated from (a) the 8-h plasma specific activity and (b) by extrapolation to zero time of the plasma specific activities during the 7 days after injection. At the end of the experiment the fat and water contents of the bodies of the sheep were determined directly.

Complete equilibration of tritiated water between plasma and rumen water was not achieved in all animals 8 h after intravenous or intraperitoneal injection but was when the rumen was primed by the combination of intraperitoneal and intraruminal dosing. After intraruminal dosing equilibration was not achieved in any animal within 8 h of dosing.

Urinary losses of marker were lower after intraruminal dosing but otherwise averaged 4–5 % of the dose/1 urine. This was equivalent to 0·3–6·7% of the dose for individual sheep.

Errors resulting from incomplete equilibration and urinary loss of marker did not influence the efficiency of prediction of total body water from tritiated water space. The multiple correlation coefficient relating body fat with empty body weight and its water content was very high (r = 0·99). Errors introduced into this relationship by the inclusion of gut water in the prediction equations were apparently of a similar magnitude to those resulting from the errors in the estimation of tritiated water space.

The extrapolation method for the determination of tritiated water space was shown to have the same accuracy as equilibration techniques under these controlled dietary conditions.
Flowering and maturation of grain maize under British conditions
Authors: Gunn R. E.
Published: March 2009

The relationships between mid-silking date, mid-maturity date, spread of silking and spread of maturity were studied in four maize hybrids. Mid-maturity date and spread of maturity were positively related to mid-silking date. The spread of silking ranged from 13 to 18 days and the spread of maturity from 34 to 47 days in different hybrids. Grain moisture content at mid-maturity ranged from 40 to 35%. It was concluded that the common practice of harvesting grain crops at 40% dry matter is likely to result in appreciable loss of yield: variation in the proportion of mature kernels when the grain has reached 40% moisture may account for the large season to season variation in yield observed in commercial crops. The potential benefits of early flowering hybrids are briefly discussed.
A dynamic model for the effects of soil and weather conditions on nitrogen response
Authors: Greenwood D. J. , Wood J. T. , Cleaver T. J.
Published: March 2009

A dynamic model was derived to predict crop response to nitrogen fertilizer under different soil and weather conditions. It combined formulae representing existing principles about important processes such as leaching of nitrate through soil and nitrate uptake by plant roots. Starting values were given for the initial plant weight and its nitrogen content and parameters were included for the crop's growth and rooting characteristics under optimum growing conditions. For each day the model re-calculated the distribution of water, nitrate and roots down the soil profile and the increment of growth.

The validity of the model was tested by using it to forecast the effects of different weather conditions and cultural practices on the nitrogen responses of a test crop, lettuce, when grown in experiments that were entirely independent of those used to obtain parameter values for the model. It successfully predicted the effects on the general shape of the response curve of the distribution of rainfall during the growing season, the age of the plant, the depth of fertilizer incorporation and the application of the nitrogen partly as a top dressing instead of entirely as a base dressing.

The model was used to develop a strategy for nitrogen fertilizer practice for lettuce in the U.K. which was found to be broadly in agreement with the results of fertilizer experiments on grower's holdings.
Stocking rate trials in Ankole, Uganda: I. Weight gain of Ankole steers at intermediate and heavy stocking rates under different managements
Authors: Harrington G. N. , Pratchett D.
Published: March 2009

A series of stocking rate trials running for differing periods between 1961 and 1972 are summarized. Weight gains of steers grazed at 2·4, 1·2, 0·8 and 0·6 ha/300 kg animal on Cymbopogon/Hyparrhenia/Themeda pasture are detailed. Subtreatments included continuous and rotational grazing and the removal of the unpalatable Cymbopogon afronardus.

Weight gains at 0·6 ha/animal were higher than a linear relationship between stocking rate expressed as animals/ha and weight gain would predict. This was ascribed to the dominance of the high quality grass Brachiaria decumbens at this grazing pressure.

Rotational grazing was less productive than continuous grazing, because C. afronardus increased more rapidly under this management, but there was less soil erosion. Removal of C. afronardus increased cattle growth rates and gains/ha by over 40% at 0·6 ha/animal. The cost of clearing this weed should be recovered in 2 years from a commercial cattle ranch. A grazing pressure of ca. 0·8 ha/animal is expected to maximize long-term profits on C. afronardus-free Ankole rangeland and in 3 years in this trial average gains of 0·29 kg/day/animal were achieved. This was an annual production level of 131 kg/ha/annum, which compared with 53 kg/ha at 2·4 ha/animal and 143 kg/ha at 0·6 ha/animal.
The heat production of hens and cockerels maintained for an extended period of time at a constant environmental temperature of 23 °C
Authors: O'Neill S. J. B. , Jackson N.
Published: March 2009

Hens and cockerels of a White Leghorn strain (‘H & N’) were kept at a constant temperature of 23 °C from 1 year until 2¼ years of age. The mean fasting heat production, which was measured 6 times during this period, varied between 404 and 464 kJ/kg0·75/day for the hens and between 223 and 349 kJ/kg0·75/day for the cockerels. The sex difference in heat production is discussed and an attempt is made to explain the variation in heat production for each sex.
Nitrogen metabolism in the ovine stomach: 3. Urea in the abomasal secretions
Authors: Harrop C. J. F. , Phillipson A. T.
Published: March 2009

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.
The effect of cutting height and mulching on aerial tillering in two contrasting genotypes of perennial ryegrass
Authors: Simons R. G. , Davies Alison , Troughton A.
Published: March 2009

In simulated swards of perennial ryegrass the production of aerial tillers, in which the growing point has been raised some distance above ground level by internode extension, depended upon the genotype and management. In both genotypes studied decreasing the height of defoliation from 10 to 2·5 cm nearly halved the incidence of aerial tillering, while the presence of a mulch of chopped straw at the base of the sward more than doubled the occurrence of these tillers. The effects of management are also discussed in relation to herbage production. The differences between the genotypes in the degree of aerial tillering suggests that selection for reduced aerial tillering may be of benefit.
Electrical conductivity of foremilk for detecting subclinical mastitis in cows
Authors: Linzell J. L. , Peaker M. , Rowell J. G.
Published: March 2009

In order to assess the potential value of milk conductivity sensors for the detection of subclinical mastitis, measurements have been made manually on quarter foremilk samples for 10–74 days from 44 cows in two herds. Some measurements were also made of quarter cell counts and yields but the true status of the cows was established by bacteriological examination near the end of each run.

For uninfected cows, conductivities of the four quarters tended to move in parallel from day to day whereas for infected cows there were usually substantial departures from parallelism. A statistic which is a measure of departure from parallelism is the quarter × day interaction mean square (I.M.S.), the magnitude of which was used to discriminate between infected and uninfected cows. Using conductivity data obtained at the time of the bacteriological examination, I.M.S. correctly identified all 19 un-infected cows and 24 out of 25 infected cows, the single misclassified cow being only mildly infected. The procedure was further tested on data obtained from one of the herds a year later. In this case, using the I.M.S. limits established the year before, 14 out of 18 infected cows were correctly identified, the four failures being only mildly infected. With nine uninfected cows, there were three false positives but these cows were all pregnant and had been lactating for 44 weeks. Although special limits may have to be set for cows in late lactation, two of these animals had been infected during the lactation, so that conductivity changes may reflect past damage to the udder.

The same data used to set I.M.S. limits were also examined in simpler ways that required little or no calculation. These were ‘differential conductivity’ (the quarter with the highest conductivity divided by the value for the lowest), ‘absolute conductivity’, ‘mixed conductivity’ (mixed foremilk from all four glands) and ‘out-of-balance conductivity’ (the product of the conductivities of the fore quarters divided by the product of the hind quarters or vice versa). These methods of analysis were all less sensitive than the I.M.S. test for parallelism. Differential conductivity, absolute conductivity and mixed conductivity all detected severe cases but missed more mild cases. Out-of-balance conductivity was much less satisfactory because it missed some severe cases.
Productivity of S. 59 red fescue with and without S. 184 white clover under hill conditions: 2. Herbage measurements in relation to animal performance
Authors: Davies D. A.
Published: March 2009

Herbage availability, intake and nutritive value were recorded on swards of S. 59 red fescue (Festuca rvbra L.) and S. 23 perennial ryegrass (Lolium perenne L.), with and without S. 184 white clover (Trifolium repens L.), and correlated with animal performance. Intake of dry matter was similar on all treatments. Animal live-weight gains during 1969 were positively correlated with digestible organic matter intake (DOMI).

Poor animal performance from red fescue swards in mid-summer was attributed to the rapid fall in digestibility at this time which affected DOMI.

Differences between treatments in efficiency of conversion of DOMI into live-weight gains were observed. Superior conversion ratios in swards containing clover could not be related to any of the herbage quality measurements recorded.

Better animal productivity from red fescue swards in early spring and in late autumn were related to the longer growing season of this grass.

The merits and demerits of red fescue as a grass for hill conditions and the possibility of reducing its limitations by breeding are discussed.
A survey of fat characteristics of lamb with particular reference to the soft fat condition in intensively fed lambs
Authors: L'Estrange J. L. , Mulvihill T. A.
Published: March 2009

Two surveys, involving 288 lambs, were carried out on the effects of system of production on the melting (slip) point, iodine value, and fatty acid composition of perinephric and subcutaneous carcass fat. The systems studied were:

A, early Spring lambs fattened indoors on concentrates;

B, early Spring lambs off grass;

C, early Summer lambs off grass;

D, Autumn lambs off grass, and

E, Winter hoggets.

The melting point of both perinephric and subcutaneous fat increased progressively during the season from mean values of 41 and 32°C respectively in group A to mean values of 48 and 42°C respectively in group E. Discolouration of the surface fat was associated with the low melting points of group A.

Mean iodine values of both fats decreased progressively from group A to group E and this change was associated with a decrease in levels of oleic and palmitoleic acid and a corresponding increase in the level of stearic acid. In the fat, levels of myristic acid were highest in grass fed lambs while levels of linoleic acid were highest in the concentrate-fed lambs.

Within each group, perinephric fat contained more stearic and less oleic, palmitoleic, palmitic and myristic acid than subcutaneous fat.

Within animals, the levels between perinephric and subcutaneous fat of melting point, iodine value and most of the individual fatty acids were highly correlated.

Within animals also, the melting point of perinephric fat was correlated in decreasing order of significance with stearic acid, oleic acid, iodine value, linoleic acid and palmitoleic acid, while melting point of subcutaneous fat was correlated in decreasing order of significance with stearic acid, oleic acid, palmitoleic acid, iodine value, linoleic acid and total branched-chain fatty acids.
Effects of dietary unsaturated fat and of protein source on melting point and fatty acid composition of lamb fat
Authors: Gibney M. J. , L'estrange J. L.
Published: March 2009

Four groups of six store lambs were offered ad libitum a concentrate barley-based diet, supplemented with either 8% casein or 2% urea, each contributing the same level of nitrogen to the diet and each fed with or without a supplement of 5·8% sunflower oil. Daily food intake was significantly affected by treatment but there was no significant treatment effect on live-weight gain or food conversion efficiency. In rumen fluid the casein supplement resulted in more total volatile fatty acids and a greater proportion of valeric acid, while the sunflower oil supplement significantly increased the proportion of propionic acid. Sunflower oil supplementation decreased the melting point of perinephric fat by about 3 °C, associated with an increase in the proportions of palmitoleic, oleic, linoleic and linolenic acids and a decrease in the proportions of palmitic and stearic acids. Sunflower oil resulted in a smaller and nonsignificant decrease in the melting point of subcutaneous fat which was associated with an increase in the proportions of linoleic and linolenic acid and a decrease in the proportion of palmitic acid. Melting point of both fats was not affected by source of dietary nitrogen supplementation but in subcutaneous fat the urea supplement resulted in a small increase in the proportion of oleic acid and a decrease in the proportions of palmitic and palmitoleic acids. The proportions of branched-chain and oddnumbered n-acids in both fats were not affected by treatment.
Quantitative digestion of fresh herbage by sheep: IV. Protein synthesis in the stomach
Authors: Ulyatt M. J. , Macrae J. C. , Clarke R. T. J. , Pearce P. D.
Published: March 2009

The proportions of bacterial and dietary protein entering the duodenum of sheep fed fresh herbage were assessed using 2,6-diaminopimelic acid as a marker. The herbages fed wereLolium perenneL., ‘Grasslands Ruanui’ perennial ryegrass;L. (perenne × multiflorum), ‘Grasslands Manawa’ short-rotation ryegrass;Trifolium repensL., ‘Grasslands 4700’ white clover.

The dietary protein degraded in the stomach was approximately 70% for all herbages. The bacterial contribution to protein entering the duodenum was 43·1, 57·1 and 52·9% for Ruanui, Manawa and white clover respectively. Protein entering the duodenum contained only a small amount of protozoal protein.

Bacterial protein synthesis in the stomach was different for all three herbages, averaging 16·2, 30·7 and 19·8 g/100 g organic matter apparently digested for Ruanui, Manawa and white clover respectively. It is suggested that the micro-organisms digesting Manawa synthesized protein more efficiently.
Quantitative and qualitative influences of dietary urea on the composition of duodenal digesta in calves
Authors: Nikolić J. Anna , Pavličević A. , Zebrowska Tereza
Published: March 2009

The aim of the present investigation was to determine the effect of adding urea to a diet based on ground maize and dried sugar-beet pulp (2/1) on the composition of duodenal content and diet digestibility in calves.

Two bull calves (140 kg) were provided with duodenal fistulae and pair fed the ration alone or with 1·2% urea in a cross-over design. Lucerne hay was also given. The difference in intake of nitrogen between the two diets was 18·4 g/day.

The results obtained showed negligible differences between the diets in the amounts of dry matter, organic matter and energy disappearing both before and after the duodenum. Digestibility of nitrogen was greater with the urea-containing diet.

Although some of the added urea (25%) was apparently lost from the forestomach, the duodenal digesta contained 13·7 g N/day more with the diet containing urea. Of this a minimum of 6·5 g was in the form of amino acid-N and only 0·4 g as ammonia-N. All the amino acids determined were present in increased amounts but lysine and isoleucine showed smaller relative increases than the other amino acids.

From these results and calculations based on measurements of 2,6-diaminopimelic acid it is suggested that the extra protein in the duodenal content derives from both more efficient bacterial protein synthesis in relation to energy expended and decreased degradation of plant protein in the rumen.
A comparison of the effect of rainfall on spring- and autumn-dressed wheat at Rothamsted Experimental Station, Harpenden (With Five Text-figures.)
Authors: “Alumnus”
Published: March 2009

The effect of rainfall on the wheat crop grown on Broadbalk has been investigated, special attention being paid to the time of application of the nitrogenous manures.

In the years 1854–77, when plots were manured solely in the autumn, the average decrease in yield caused by each additional inch of rain is greater than the average decrease from 1854–1918. The difference in this case cannot be ascribed to the change in manurial treatment.

The period of 24 years was too short to allow seasonal variation in the effect of rain to appear, as it was only possible to compare such seasonal variation with that of 1854–1918 in the case of one plot. In this case it was observed that summer rainfall was more detrimental to autumn-dressed than to spring-dressed plots; this result was confirmed by studies of the effect of rain on the difference in yield of two plots which differed only in the time of application of their manures.
“Single value” soil properties: a study of the significance of certain Soil constants. VII. The moisture equivalent and some related quantities (With two text-figure.)
Authors: Coutts J. R. H.
Published: March 2009

The moisture equivalent has been measured (by a technique requiring only small quantities of soil) for a number of samples comprising Natal and Sind soils. It is concluded that while with the latter (alkaline and saline) soils the moisture equivalent gives valuable information, it adds little to the data obtained by other methods for the Natal soils. The xylene equivalent of the Natal soils has also been measured; from the moisture equivalent and the xylene equivalent, the imbibitional water can be calculated if the specific gravity of the soil is known.

Equations expressing the moisture equivalent and the xylene equivalent of the Natal soils in terms of their loss on ignition and mechanical composition are obtained, and the significance of the relative values of the numerical coefficients in these equations is discussed.