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X-ray microscopy is a field that has developed rapidly in recent years. Two different approaches have been used. Zone plates have been employed to produce focussed beams with sizes as low as 0.07 pm for x-ray energies below 1 keV. Images of biological materials and elemental maps for major and minor low Z have been produced using above and below absorption edge differences. At higher energies collimators and focussing mirrors have been used to make small diameter beams for excitation of characteristic K— or L-x rays of all elements in the periodic
Decreasing the proportion of long forage in mixed diets from 400 to 100 g/kg at constant digestible energy intakes reduces milk fat content by approximately 5 g/kg for every 100 g/kg decrease in hay. This response varies widely and a safe minimum diet composition to maintain approximately 40 g fat/kg milk from Friesian cows in mid-lactation is approximately 450 g long forage/kg or 220 g acid-detergent fibre/kg dry matter. This, however, would reduce milk yields. With barley-based concentrates, milk yield increases as the proportion of hay in the diet is reduced, with the result that the reduction in the yield of fat is less than the fall in its concentration. Milk fat content is higher when ground maize, which is a slowly fermented starch source, or fodder beet or fibrous by-products replace rapidly fermented starch sources such as barley in low-roughage diets. Milk yield, however, is lower. Supplementary fats and oils generally increase milk yield but their effects on milk fat content and yield vary widely.
Increasing the intake of high-concentrate diets of fixed composition increases the yield of milk but reduces its fat content. Increasing the number of meals per 24 h reduces this milk fat depression without affecting milk yield. Thus, advice on milk fat production must take account of the level of intake, the pattern of feeding and the diet composition.
In most situations, the avoidance of low milk fat content requires control of rumen fermentation to prevent high proportions of propionic acid. However, with frequent feeding during the 24 h, high propionic acid in the rumen has less effect on milk fat. It appears that high plasma insulin concentration is the main factor reducing milk fat production.
The release of insulin is stimulated by the peaks of propionate, which are produced after large meals of concentrates but not by the steady supply of propionate associated with frequent feeding.
Available knowledge can permit wide variation in milk fat production by dietary manipulation with reasonable accuracy but the future aim should be for more direct intervention at metabolic control points.
At maintenance at least, the whole tract digestibility of several foods in sheep and cattle is similar, consequently much of the information on the nutritive value of dairy cow foods in food composition tables is derived from studies conducted in sheep. However, Adesogan (1996) reported that in whole-crop wheat (WCW), starch digestibility is higher in sheep than in dairy cows. This study examined the validity of using sheep to model the ruminal degradation of WCW in cows by comparing the degradability of dry matter (DM) and nitrogen (N) of urea-treated WCW in both species.
Winter wheat (cv. Hussar) was harvested at 540 g DM per kg and conserved following urea application at target rates of 20 or 40g/kg DM (WCW2 and WCW4 respectively). The degradability of the forages was examined in dairy cows given 6 kg dairy concentrate and grass silage ad libitum and in wethers given 2.4 kg/day of grass silage supplemented with 0.36kg/day of rolled, mineralized barley.
Ruminant feeding standards in Brazil are generally based on systems developed for temperate regions and there is a serious lack of information on grazed tropical pasture which is the main feedstuff. Signal grass (Brachiaria decumbens) represents half of the total cultivated pastures in Brazil (Miles et al., 1996). This study investigated the intake and digestibility by sheep of signal grass hay cut after re-growths of 28 and 56 days to represent the range used in practice in the Brazilian savanna. Lucerne hay was included as a positive control. The hays were offered at two levels of intake to Santa Ines wether sheep.
Whole oil seeds represent an alternative to many commercial rumen-protected fat sources as energy supplements in rations for lactating dairy cows. Rumen protection reduces the potential for negative effects of unsaturated fatty acids on fibre digestion, but the structure of many whole oil seeds are thought to reduce the reactivity of their fat in the rumen. Cotton seed is often imported for inclusion in UK dairy rations, but rape seed represents a home grown oil seed which has potential as an economical fat and protein source in UK dairy rations. However, the seed must be crushed or chemically treated to be digested effectively and crushing may liberate oil to the extent that rumen digestion is altered. In a 20 week lactation study, supplemental fat from rumen-protected fat, cotton seed and rape seed fed at 25 g/kg dry matter (DM) in a grass-silage based total mixed ration (TMR) increased milk yield to a similar extent. However, DM intake was reduced by cotton seed and milk protein was reduced by rumen-protected fat (Reynolds et al., 1998). These responses may reflect alterations in digestive function, thus the objective of the present study, conducted simultaneously to the lactation study, was to evaluate the effects of the same diets on rumen, postrumen and total digestion in lactating dairy cows.
Crushed rapeseed and other oil seeds offer an economical source of fat and protein in diets for lactating dairy cows, but the potential inhibitory effects of their unsaturated fatty acids on fibre digestion in the rumen are a concern. Feeding crushed rapeseed in a grass silage-based ration increased milk yield without affecting intake (Reynolds et al., 1998), and had no measurable effects on rumen or total tract digestion (Reynolds et al., 2000). In a companion study, feeding increasing amounts of ground rapeseed in a maize silage-based ration decreased DM intake at higher levels of inclusion (Reynolds et al., 2002). This effect may reflect metabolic effects of rapeseed fatty acid absorption, or negative effects of rapeseed oil on rumen fermentation and fibre digestion. The present study was conducted simultaneously to the production study to determine the incremental effects of ground rapeseed on rumen, post-rumen and total tract digestion in lactating dairy cows fed maize silage-based rations.
A significant proportion of the grass silage fed to lactating dairy cows may be of only modest quality due either to delayed harvesting and/or poor ensiling conditions. In such situations, both total feed intake and milk production are likely to be compromised with the consequent need to feed more concentrates. Part of this effect is considered to be due to the development of a solid mass of digesta in the rumen, with loss of the normal layered or biphasic stratification of rumen contents. Under such conditions, rumen motility, rate of forage digestion and hence voluntary feed intake will be compromised. Mertens (1997) stressed that chemical definition of dietary fibre such as neutral- (NDF) or acid-detergent (ADF) fibre content was an inadequate description of the fibre content of a diet as it affects rumen function and animal performance. Consequently he proposed both effective NDF (eNDF; ability of a feed to replace a roughage with no negative effect on milk fat content) and physically effective NDF (peNDF; a measure of the physical properties of fibre as it stimulates chewing activity and development of the biphasic stratification of rumen contents) as additional descriptors of the physical characteristics of dietary fibre but to date these concepts have attracted limited attention in the UK. This study examined the effect of replacing increasing amounts of grass silage (GS) on a dry matter (DM) basis in a silage:concentrate ration with pressed sugar beet pulp (PP) on various processes of digestion in the rumen of lactating dairy cows, specifically in relation to chewing activity and rumen mat density.
Cellulose and hemicellulose are the major structural carbohydrates present in forages and form between 30 and 60% of the forage component of ruminant diets. The complex network of structural carbohydrates and lignin generally leads to low digestibility and limits the efficient utilisation of forages by ruminants. This situation occurs in both developed and developing countries, and in the latter it is particularly pronounced as much of the forage component is based around the use of crop residues (Owen and Jayasuria, 1989). Because forage costs are significantly lower than those of other dietary ingredients, improving forage quality has been a major objective for many research programmes in both the developed and developing world. Improvements in forage quality have been sort through a number of different strategies. These have included conventional breeding techniques, which have included the integration of mutant genes, leading to the development of Brown Midrib varieties of maize and the use of chemical and biological additives. Enzyme supplements are commonly used to improve the nutritive value of feeds for non ruminants and as silage additives where they have been shown to improve silage fermentation, feed intake and performance. Recent work with ruminants has however focused on the use of enzyme supplements to improve feed efficiency by the use of “direct-fed” fibrolytic enzymes. This strategy involves the application of enzymes to feed at or only hours before feeding. These studies have yielded very variable production responses. For any new technology to be implemented widely, the responses achieved must provide an acceptable level of consistency and predictability. The current paper reviews developments in enzymology, production responses achieved and the effects on nutrient digestion.
Maize distillers grains (MDG) is a high quality by-product feed containing 317 g crude protein (CP)/kg DM and 13.5 MJ metabolisable energy/kg DM, and as such is a valuable traceable feed resource. An earlier study conducted at the Centre for Dairy Research (Sutton et al. 2000) with cows in late lactation using a total mixed ration (TMR) based on maize silage, compared the protein value of MDG with that of soyabean meal (SB). The study showed that MDG could be used to replace SB on a total nitrogen (TN) basis without effecting feed intake or nutrient digestion in the rumen, or flow of non-ammonia nitrogen to the duodenum. The aim of the current study was to determine the effect of replacing SB with MDG on a TN basis, on DM intake and milk production in high yielding lactating dairy cows.
We present correlation function results from galaxy and QSO redshift surveys. The galaxy correlation function shows evidence for a possible ‘shoulder’ feature in ξ(s) at s = 2h−1 Mpc. At scales between 10 and 100h−1Mpc the correlation function remains close to zero and shows no evidence for any large scale galaxy clustering. The QSO correlation function detects strong QSO clustering for scales s < 10h−1 Mpc. At larger scales (10 < s < 1000h−1 Mpc) no evidence of significant QSO clustering is seen.
Observations with a swept frequency machine show that the shapes of individual pulses from NP 0531 are truncated exponentials with widths proportional to λ~4, consistent with the broadening arising from scattering in the interstellar medium. A histogram of pulse intensity reveals two different populations. The very strong pulses are associated only with the main pulse and interpulse.
As a label for a distinct category of life, “living fossil” is controversial. The term has multiple definitions, and it is unclear whether the label can be genuinely used to delimit biodiversity. Even taking a purely phylogenetic perspective in which a proxy for the living fossil is evolutionary distinctness (ED), an inconsistency arises: Does it refer to “dead-end” lineages doomed to extinction or “panchronic” lineages that survive through multiple epochs? Recent tree-growth model studies indicate that speciation rates must have been unequally distributed among species in the past to produce the shape of the tree of life. Although an uneven distribution of speciation rates may create the possibility for a distinct group of living fossil lineages, such a grouping could only be considered genuine if extinction rates also show a consistent pattern, be it indicative of dead-end or panchronic lineages. To determine whether extinction rates also show an unequal distribution, we developed a tree-growth model in which the probability of speciation and extinction is a function of a tip’s ED. We simulated thousands of trees in which the ED function for a tip is randomly and independently determined for speciation and extinction rates. We find that simulations in which the most evolutionarily distinct tips have lower rates of speciation and extinction produce phylogenetic trees closest in shape to empirical trees. This implies that a distinct set of lineages with reduced rates of diversification, indicative of a panchronic definition, is required to create the shape of the tree of life.
We present pollen diagrams and sedimentological analyses from a lake site within an extensive dune system on the Aupouri Peninsula, Northland. Five thousand years ago, a regional Agathis australis–podocarp-broadleaf forest dominated the vegetation, which manifested an increasing preponderance of conifer species. Climate was cooler and drier than at present. From ca. 3400 bp, warmth-loving species such as A. australis and drought-intolerant species, Dacrydium cupressinum and Ascarina lucida, became common, implying a warm and moist climate. The pollen record also suggests a windier climate. The most significant event in the record, however, occurred after ca. 900 bp (800 cal bp) when anthropogenic deforestation commenced. A dramatic decline in forest taxa followed, accompanied by the establishment of a Pteridium–esculentum-dominated community. Fire almost certainly caused this, evidenced by a dramatic increase of charcoal. Sedimentological evidence for this site indicates a relatively stable environment before humans arrived and an increasingly unstable environment with frequent erosional events after human contact.
Official suicide statistics for England are based on deaths given suicide verdicts and most cases given an open verdict following a coroner's inquest. Previous research indicates that some deaths given accidental verdicts are considered to be suicides by clinicians. Changes in coroners' use of different verdicts may bias suicide trend estimates. We investigated whether suicide trends may be over- or underestimated when they are based on deaths given suicide and open verdicts.
Possible suicides assessed by 12 English coroners in 1990/91, 1998 and 2005 and assigned open, accident/misadventure or narrative verdicts were rated by three experienced suicide researchers according to the likelihood that they were suicides. Details of all suicide verdicts given by these coroners were also recorded.
In 1990/91, 72.0% of researcher-defined suicides received a suicide verdict from the coroner, this decreased to 65.4% in 2005 (ptrend < 0.01); equivalent figures for combined suicide and open verdicts were 95.4% (1990/91) and 86.7% (2005). Researcher-defined suicides with a verdict of accident/misadventure doubled over that period, from 4.6% to 9.1% (p < 0.01). Narrative verdict cases rose from zero in 1990/91 to 25 in 2005 (4.2% of researcher-defined suicides that year). In 1998 and 2005, 50.0% of the medicine poisoning deaths given accidental/misadventure verdicts were rated as suicide by the researchers.
Between 1990/91 and 2005, the proportion of researcher-defined suicides given a suicide verdict by coroners decreased, largely due to an increased use of accident/misadventure verdicts, particularly for deaths involving poisoning. Consideration should be given to the inclusion of ‘accidental’ deaths by poisoning with medicines in the statistics available for monitoring suicides rates.
We describe three new species of fruit flies (Tephritidae: Tephritinae) (Gymnocarena defoeisp. nov. and Gymnocarenanorrbomisp. nov., from eastern North America and Gymnocarena monzonisp. nov. from Guatemala) and redescribe Gymnocarena mississippiensis Norrbom. Gymnocarena monzoni is the first Gymnocarena species to be recorded from Guatemala. This brings the total number of named species in this genus to 19. New larval host plant (Asteraceae) records for Gymnocarena include Verbesina helianthoides Michx. for G. mississippiensis and G. norrbomi, Verbesinaalternifolia (L.) Britton ex Kearney for G. norrbomi, and Viguiera cordata (Hook. and Arn.) D'Arcy for G. monzoni. The latter represents the first record for Gymnocarena in Viguiera Kunth. Gymnocarena larvae were also recorded from Verbesina virginica L. but not identified to species. A revised key to the known species of Gymnocarena and additional information on larval host plants and biology are provided.