bluuebunny/crossref_metadata_2025_split huggingface dataset:
Density and row spacing effects on irrigated short wheats at low latitude
Authors: Fischer R. A. , I. Aguilar M.  , R. Maurer O.  , S. Rivas A.  
Published: March 2009

SummaryDuring four winter seasons eight spacing and density experiments were made under irrigated high fertility conditions in north-west Mexico (latitude 27° N). Experiments included various Triticum aestivum and T. durum genotypes of spring habit, short stature derived from Norin 10 genes, and contrasting plant type. Measurements included dry-matter production, photosynthetic area index, and light interception during one experiment, total dry matter at maturity in most others and grain yield and its numerical components in all experiments.Grain yield and most other crop characters were unaffected by row spacings within the range 10–45 cm interrow width. The optimal seeding density for maximum grain yield was 40–100 kg/ha (80–200 plants/m2). Yield reductions at lower densities (20, 25 kg/ha) were slight and accompanied by reduced total dry-matter production. Yield reductions at higher densities (160–300 kg/ha) were also slight and were associated with more spikes/m2 but fewer grains/m2 and reduced harvest index. It is suggested that lower than normal preanthesis solar radiation or weather conditions leading to lodging can magnify these yield depressions at higher densities.Measurements showed rapid approach of crops to 95% light interception, reached even at a density of 50 kg/ha within 50 days of seeding. It is suggested that provided this occurs before the beginning of substantial dry-matter accumulation in the growing spikes (60 days after seeding) there will be no loss of grain yield with reduced seeding density. Results point to a ceiling photosynthetic area index for maximum crop growth rate although there was a tendency for rates to fall at very high indices (> 9). This tendency was associated with very high density, high maximum numbers of shoots, poor survival of shoots to give spikes (< 30%) and reduced number of grains/m3;. The relatively low optimal densities seen here may be characteristic of genotypes derived from Norin 10.Genotype × spacing, genotype × density and spacing × density interactions were generally non-significant and always small. There was a tendency for the presence of non-erect leaves or branched spikes to reduce the optimal density, but large differences in tillering capacity had no influence. Differences in lodging susceptibility can however lead to substantial genotype x density interactions.
Seasonal changes, breed differences and repeatability of plasma copper levels of sheep at pasture
Authors: Wiener G. , Field A. C. 
Published: March 2009

SummaryPlasma copper levels were determined at intervals of 9 weeks over a period of 1 year on 131 female sheep of a grassland flock starting at the age of 5 months in September. The 107 survivors were re-bled 3 years later. There was a steady decline in copper levels from about 100 µg/100 ml plasma in November to about a third of that level at the beginning of the following June. Thereafter there was a partial recovery in level.Three breeds, Scottish Blackface, Cheviot and Welsh Mountain and their crosses were represented. There were marked differences in plasma copper level among the breeds with cross-breds having levels as high or higher than the corresponding pure breeds. Breed differences in copper levels were already present at 5 months old. Part of the breed differences in copper levels were attributable to differences among the breeds in the frequency of the HbA and HbB alleles.Correlations were calculated among the plasma copper levels from successive bleedings for individuals within breeds and subclasses. From the time the sheep reached about 9 months old these correlations ranged from 0·4 to 0·9 including bleedings more than 3 years apart in time.
The examination of some winter hardiness components in grasses using canonical variate analysis
Authors: Thomson A. J. 
Published: March 2009

SummaryWinter vigour, winter burn, freezing damage and early spring yield were measured in 24 perennial ryegrass varieties which varied in their degree of winter adaptation. Winter vigour and winter burn were negatively correlated due to senescence in the dormant varieties. Cold resistance, measured in a freezing test, was also negatively correlated with winter burn but was independent of spring yield. Spring yield was positively related to winter vigour but negatively related to winter burn. The more dormant varieties which sustained most winter burn were better able to survive freezing.A canonical variate analysis showed that the first two canonical variates accounted for 87·8% of the total variation. Interpolation from the means of the four characters suggested that the first canonical variate represented adaptation to winter conditions. A generalized model based on these findings is proposed and its use in the formulation of grass breeding strategies discussed.
Rumen fermentation studies on two contrasting diets. 2. Comparison of the performance of anin vitrocontinuous-culture fermentation within vivofermentation
Authors: Barry T. N. , Thompson A. , Armstrong D. G. 
Published: March 2009

SummaryAn impermeable continuous-culture artificial rumen was constructed and rumen microbial populations were culturedin vitrofor periods of up to 23 days. Diets of hay and 20:80 hay:cooked flaked maize (concentrate diet) were fed to thein vitrocultures and also to sheep, and the performance of thein vitrofermentation compared with that of thein vivofermentation.With the hay diet, changing the initial inoculum from strained rumen liquor to unmodified rumen contents (containing solid ingesta) reduced the time required to attain a steady-state fermentationin vitrofrom 13 to 4 days. VFA molar proportions and the CO2: CH4ratio indicated that the type of fermentation taking placein vitrowas remarkably close toin vivofermentation. However, rates of cellulose digestion, CH4production and number of bacteria/unit volume (as judged by DNA concentration) were much lessin vitrothanin vivo, showing that the rate of fermentation was reduced in the artificial rumen. Total VFA concentration and the osmotic pressure of fermentor liquor were slightly higher than the maximum values foundin vivo, and it was concluded that these were responsible for the reduced rate of fermentation.Regardless of the duration of culture, a satisfactory steady-state fermentation was never attained when the concentrate diet was administered. DNA concentration in fermentor liquor declined to very low levels after 4 days; CH4production rapidly declined and was replaced by H2production after 5 days. VFA molar proportions bore little resemblance to those foundin vivo. Both the osmotic pressure of fermentor contents and total VFA concentration rapidly increased with time, and by day 3 were approximately 2·5 times the values foundin vivo. It was concluded that high VFA concentration, and the associated increase in osmotic pressure, were the main factors responsible for the unrealisticin vitrofermentation, and that this problem was much greater than encountered with the hay diet due to starch being digested at a faster rate than cellulose and hemicellulose.Methods of regulating VFA concentration in continuous culturein vitrorumen systems are discussed and some improvements suggested.
Zinc nutrition of onions as influenced by phosphorus
Authors: Asif M. I. , Khan A. A. , Ajakaiye M. N. 
Published: March 2009

SUMMARYIn a field study it was found that application of high P induced Zn deficiency symptoms on onion (Allium cepaL.) plants, increased P concentration but decreased that of Zn. Conversely, application of Zn tended to increase Zn concentration of both tops and bulbs and lowered P concentration. Effectiveness of Zn varied with the amount of P applied. Evidently P and Zn are mutually antagonistic. Using sub-soil on the top of raised beds and heavy P fertilization appear to be responsible for inducing Zn deficiency in onions in northern Nigeria.
Total nitrogen concentration in leaves of potatoes (Solanum tuberosumL.) as an index of nutritional status
Authors: Gupta A. , Saxena M. C. 
Published: March 2009

SummaryLeaf samples were collected, at weekly intervals, throughout the growing season, from potato (Solanum tuberosumL.) plants supplied with varying amounts of nitrogen (0, 60, 120, 180 and 240 kg N/ha) and analysed for total N. Application of nitrogen increased the N concentration in the green leaves at all stages of growth. There was a significant curvilinear relationship between the final tuber yield and the total N concentration in the leaves at 48–90 days after planting in 1968–9 and at 79–107 days after planting in 1969–70. The N concentration at 70–90 days after planting was consistently related to the final tuber yield in both years. Thus this period was ideal for assessing the nitrogen status of potato plants. The critical concentration of total nitrogen generally decreased with advance in age. It ranged from 4·65% at 76 days to 3·30% at 90 days during 1968–9, whereas in 1969–70 it ranged from 4·20% at 79 days to 3·80% at 93 days. During the period from 83 to 86 days the critical percentage was around 3·6% in both the years.
In situ estimation of root length at natural soil profiles
Authors: Böhm W. 
Published: March 2009

SummaryA thin layer of soil was washed from a smoothed soil profile and the length of the roots visible at the profile wall estimated. A grid net was used to count every visible part of a root which was nearly 5 mm long. Roots which were longer than 5 mm were counted more than once. This improvement of the traditional trench profile method provides an estimate of the root length in a soil volume.
Pollination as a factor limiting the yield of field beans (Vicia faba L.)
Authors: Free J. B. , Williams Ingrid H. 
Published: March 2009

SummarySelf-pollinating and cross-pollinating by hand samples of flowers in field bean crops usually gave an increased set of seed compared with control flowers left to be pollinated naturally. Hence, insect pollination of field bean crops is often inadequate. In large fields of more than 12 ha the seed yield was greater by plants near the edge than near the centre. Fewer pods were produced from nodes at the upper than the lower parts of a stem, and they contained fewer seeds which were of a smaller size.
Statistical procedures for distinctness, uniformity and stability variety trials
Authors: Weatherup S. T. C. 
Published: March 2009

SummaryThis paper describes statistical methods for analysing data arising from distinctness, uniformity and stability variety trials carried out to fulfil Statutory Regulations in the United Kingdom. Both univariate and multivariate methods are considered. It is shown that multivariate techniques can separate some variety pairs which could not be separated using univariate methods. A computer system for routinely analysing these trials is also described.
Multifactorial experimentation on continuous winter wheat grown in sandy clay soil at Saxmundham, Suffolk
Authors: Widdowson F. V. , Johnston A. E. , Penny A. 
Published: March 2009

SummaryWe present results from an experiment at Saxmundham measuring the effects of growing different numbers of successive winter wheat crops, each year, from 1971 to 1976; it followed five cropping sequences introduced from 1966 to 1970.From 1971 to 1973 four seed rates, two row spacings and three nitrogen rates were tested in all combinations with four of the previous cropping sequences. The remaining sequence was sown traditionally for continuity. Number of ears, leaf area, yield and nutrient content showed little benefit from increasing or decreasing seed rate, around that usually sown. Rows 15 cm apart gave the largest yield independently of N, because they produced most ears. There was no loss in yield from growing up to eight consecutive crops of winter wheat. 100 kg N/ha was sufficient for maximum yield.From 1974 to 1976 two varieties of different potential (Cappelle-Desprez and Maris Huntsman), chlormequat chloride (CCC), three amounts of N, as single, or as divided dressings, were tested in all combinations with the four cropping sequences. The fifth sequence again was sown traditionally, but with or without autumn-applied N. Maris Huntsman gave a grain yield only 0·22 t/ha larger (4·5%) than that of Cappelle-Desprez, and mean yields were larger (also by 4·5%) where CCC was given. Divided dressings of N increased yields by 0·11 t/ha (2·2%). The mean increase in yield from adopting all three improvements was 0·5 t/ha (or 11%). Yields of the 10th and 11th consecutive wheats declined, probably because black grass (Alopecurus myosuroides) became abundant. There was a good inverse relationship between losses of N in drainage during winter and subsequent yield and grain nitrogen uptake, which helped to explain large yield variations from year to year.
A mathematical model of fertilization failure and early embryonic mortality in sheep
Authors: Geisler P. A. , Newton J. E. , Mohan A. E. 
Published: March 2009

SummaryThe reproductive potential of a sheep system is much reduced by the failure of released ova to be fertilized and to survive to parturition. This paper looks at currently available information on fertilization failure and early embryonic deaths. Separate hypotheses are proposed for fertilization and for early embryonic mortality. For fertilization, the hypothesis is that a ewe that mates with a ram will end up with either all or none of her released ova fertilized. For embryonic mortality, the hypothesis is that the survival of a fertilized ovum depends only on how many ova were released with it and is independent of the survival or death of those released with it. A mathematical model is constructed on these hypotheses and its predictions are compared with published experimental results of other workers.
The influence of loss of plumage on temperature regulation in laying hens
Authors: Richards S. A. 
Published: March 2009

summaryThe acute thermoregulatory responses of normally feathered (control) and poorly feathered laying hens were studied in the ambient temperature range from 0 to 38 °C.Core body temperature in the poorly feathered birds began to fall at between 15 and 20 °C but this difference from the controls was significant only at 0 and 5 °C, when there was severe hypothermia. The temperature on the skin of the back was significantly lower at 20 °C and below, but the comb temperatures did not differ.The rate of oxygen consumption in the poorly feathered hens was significantly higher than that of the controls at 30 CC and below; at the acclimation temperature (20–25 °C) the difference was about 62%. The rate of increase of heat production with falling ambient temperature was 2–6 W/ma/°C in the poorly feathered group and 1–0 W/ma/°C in the controls.Absolute rates of evaporative heat loss did not differ between the two groups.The ratio of the coefficients of dry heat transfer in the poorly feathered and control birds at 0–30 °C was 2–1:1.
Insulin-secreting ability in Pietrain and Large White pigs
Authors: Gregory N. G. , Lovell R. D. , Wood J. D. , Lister D. 
Published: March 2009

summaryMesomorphic, stress-sensitive Pietrain pigs were found to have a lower insulin secretory response to intravenous tolbutamide, glucose and arginine, when compared with ectomorphic, stress-resistant Large White pigs. Pietrain pigs have also been observed to be insulin-insensitive in comparison with Large White pigs. The combination of a low production of and low sensitivity to insulin in the Pietrain breed could account for their enhanced sensitivity to lipolytic agents and for their reduced ability to deposit body fat.
Interactions between dietary carbohydrate and nitrogen and digestion in sheep
Authors: Oldham J. D. , Buttery P. J. , Swan H. , Lewis D. 
Published: March 2009

SummaryRumen fermentation, duodenal digesta flow and N balance were studied in three sheep fed diets which contained urea or fishmeal as nitrogen supplement and either barley straw, barley + corn starch or molassed wheat straw (60% molasses) as carbo-hydrate source.The molar composition of rumen volatile fatty acids (VFA) with straw diets was high in acetate (64–68%), with barley diets high in propionate (32–36%) and with molasses diets high in butyrate (28–34%). Rumen ammonia concentrations (RAC) were low and constant with fishmeal diets (< 10 mM) but varied with carbohydrate source with urea diets. RAC was very high (24 mM) after feeding molasses + urea.With barley and molasses diets 73–75% of digestible dry matter (DDM) was digested in the stomach, but only 54–59% with ground and pelleted straw diets. For all diets less N passed the duodenum than was eaten. The lowest daily duodenal N passage was with molasses + urea. Daily urinary N output was highest (P < 0·01) for this diet and nitrogen balance lowest.Daily intakes of amino acids differed widely between diets but differences in duodenal passage were not so great. Molasses + urea provided the lowest values for daily duodenal amino acid flow. The amino acid content of duodenal N (mM amino acid/16 g N) was relatively constant despite broad variation between diets. Digesta alanine and valine (mM/16 g N) were higher for barley than for straw diets (P< 0·05). Digesta methionine (mM/16 g N) was lower for fishmeal than for urea diets (P< 0·01).Very little sucrose reached the duodenum with any diet.It was concluded that the form of energy-yielding nutrient inuflenced duodenal N flow by affecting ammonia-N capture in the rumen, but that the amino acid content of duodenal N was little affected. The interaction between molasses and urea was not beneficial to efficient use of urea-N in this work when molasses was the major carbohydrate component of the diet.
Changes in albumin, globulin, glucose and cholesterol concentrations in the blood of dairy cows in late pregnancy and early lactation and relationships with subsequent fertility
Authors: Rowlands G. J. , Manston R. , Stark A. J. , Russell A. M. , Collis K. A. , Collis S. C. 
Published: March 2009

SummaryWeekly blood samples were collected from 42 Friesian cows between 5 weeks before and 10 weeks after calving, and analysed for serum cholesterol, albumin, total protein, glutamate-dehydrogenase, sorbitol-dehydrogenase and ornithine-carbamyl-transferase and blood glucose.Cholesterol concentrations increased 2½-fold during the first 8 weeks of lactation. There was also a transient decrease in glucose concentration at calving, but there was no relationship between conception rate and the concentrations of these two constituents.Albumin concentrations decreased at calving in some but not all cows and remained low for up to 2 weeks. Average concentrations of albumin determined by two analytical methods, a HABA dye-binding and a single radial diffusion assay method, were significantly lower (P< 0·05) between 0 and 2 weeks post-partum in eight cows which required four or more services than in 32 cows which conceived after fewer services. Similarly, the average decrease in concentration over calving was greater in those cows which conceived only after four or more services (P < 0·01).Globulin concentrations (total protein minus albumin) decreased during the 5 weeks before, and increased in the 3 weeks following calving. The net change over calving was significantly related to conception rate, and the albumin/globulin ratio was reduced (P< 0·001) in the eight cows requiring four or more services.Activities of all three enzymes doubled after calving, but there was no correlation between these increases and the decreases in albumin concentration, suggesting that, if liver insufficiency is a factor, it is probably due to malfunction rather than tissue damage.
Concentration of N, P and K in leaves, straw and grain of wheat and barley as influenced by N and P fertilizers under semi-arid conditions
Authors: Orphanos P. I. , Krentos V. D. 
Published: March 2009

SummaryThe N, P and K contents of leaves, straw and grain of the durum wheat Kyperounda, the aestivum wheat Pitic 62 and Athenais barley under semi-arid conditions (150–400 mm) as influenced by N and P fertilizers are reported (N rates: 0–105 kg/ha; P rates: 0–26 kg/ha).Fertilizer N increased linearly the N content of the leaves, straw and grain as well as the K content of leaves and straw, but slightly reduced P content of the grain. Straw K content was increased relatively more in Athenais barley. Such increases of N and K content occurred beyond the N rates giving maximum grain and sheaf yields. Increased K content of the straw resulting from fertilizer N is wasteful where the straw is removed, and accelerates depletion of soil K. Durum wheat grain containing more than 2–8% N showed less than 6% yellow berry (mealy grains) but at lower N contents yellow berry could be high or low depending on location.Fertilizer P did not significantly influence the P content of any of the components analysed even though it increased grain and straw yields, particularly in the drier years.
The effect of the reproductive state of ewes on their voluntary intake of diets varying in straw content
Authors: Owen J. B. , Lee R. F. , Lerman P. M. , Miller E. L. 
Published: March 2009

SummaryTwo experiments, involving a total of 112 sheep, are described, in which ewes at different reproductive states were given complete diets with a varying grain: straw ratio. In Expt 1 ewes at three reproductive states (dry, pregnant and lactating) were given diets with four levels of coarsely ground oat straw (10, 25, 40 and 55% straw). In Expt 2 ewes in five reproductive states (early pregnancy, mid pregnancy, late pregnancy, lactation and dry) were given a basal diet similar to that given in Expt 1 but with five levels of straw (15, 25, 36, 45 and 55% straw).The results showed that the intake of ewes varied with reproductive state, the highest intakes occurring during lactation. No significant diet × reproductive state interaction was observed which suggests that in ewes the physiological state can override some of the physical limitations to intake imposed by increased dietary roughage concentration.