营养师的一个新武器——益生木质纤维

<正>日粮纤维是家畜饲料的重要组成部分。益生木质纤维素(eubiotic lignocellulose)由新鲜木材制成,是一种相对较新的饲料原料,试验证明它是一种非常有价值的饲用纤维原料,对动物营养有众多的益处。日粮纤维是单胃动物消化调节的必需物质。高淀粉日粮易于快速发酵,通常在消化过程的早期就几乎被完全发酵,到达大肠时极少或已无物可发酵。在日粮中添加纤维能够使发酵进程后移至结肠,并且促进有益菌的增殖。益生菌所产生的挥发性脂肪酸能够提高肠道的健     

Oak and red maple seedling survival and growth following periodic prescribed fire on xeric ridgetops on the Cumberland Plateau

To test the hypothesis that repeated prescribed fires alone can improve the status of oak regeneration, a long-term seedling population study was established to follow permanently tagged chestnut oak (Q. prinus L.), scarlet oak (Q. coccinea Muenchh.), and red maple (Acer rubrum L.) seedlings over 8 years in sites where fire was excluded, and where fire was applied either three (3×) or four (4×) times.     

Establishment and growth of oak (Quercus alba, Quercus prinus) seedlings in burned and fire-excluded upland forests on the Cumberland Plateau

Recurrent problems with regeneration of oaks (Quercus spp.) have been documented across a wide range of ecosystems. In oak-dominated forests of the central and Appalachian hardwood regions of the United States, a lack of competitive oak regeneration has been tied, in part, to fire suppression in these landscapes, and managers throughout the region are using prescribed fire to address this concern. To examine fire effects on oak regeneration, researchers have generally relied on inventories or population studies of existing seedlings. These studies are valuable but do not permit examination of the role of fire in enhancing the establishment and growth of new oak seedlings stemming from oak mast events. In this study, white (Quercus alba) and chestnut oak (Quercus prinus) acorn mast crops serendipitously occurred in year three (fall 2005) of a landscape-scale prescribed fire experiment. We examined establishment, survival, height and diameter of new seedlings on sites on the Cumberland Plateau in eastern Kentucky. Treatments were fire exclusion, a single prescribed fire (1x-burn; 2003), and repeated prescribed fire (3x-burn; 2003, 2004, and after acorn drop in 2006), all conducted in late spring. Initial densities of newly established chestnut and white oak seedlings were statistically similar across treatments (P = 0.42), despite fires on the 3x-burn site having occurred after acorns were on the ground. Oak seedling density was significantly predicted by oak basal area on all sites (R² = 0.12–0.46), except for chestnut oak on fire-excluded sites (R² = 0.04). Litter depth was less on 3x-burn sites compared to 1x-burn and fire-excluded sites, whereas canopy openness was greater on both burn treatments compared to fire-excluded sites. Seedling mortality was generally higher on fire-excluded sites compared to burn sites, especially for white oak. Oak seedling mortality in the first two growing seasons was significantly predicted by initial litter depth and open sky, with greater litter depth and lower percent open sky leading to higher mortality. In the third growing season none of the measured variables predicted chestnut oak seedling survival; for white oak, percent open sky remained a significant predictor of mortality. Initially, seedlings on the fire-excluded sites had similar height but smaller diameter; after three growing seasons there were few differences in seedling height or diameter among treatments. Our findings suggest a potential role for prescribed fire in establishing forest floor and light conditions that may enhance the success of new oak germinants, although different responses among species may suggest the need to target management for individual oak species.     

Evaluation of welfare and productivity in pregnant sows kept in stalls or in 2 different group housing systems

One hundred eighty pregnant sows (Sus scrofa), from first to ninth parity, on a commercial farm were selected and used in 3 different replicates (60 sows per replicate). Sows were housed from day 29 of pregnancy to 1 week before parturition in conventional stalls, in groups of 10 with trickle feeding or in groups of 20 with an unprotected electronic sow feeder (Fitmix; 20 sows per housing system per replicate). All the sows were equally feed restricted. Behavior, acute-phase protein (APP) plasma levels, and productivity were assessed. General activity and stereotypies were measured by scan-sampling observation at different times of the day on 11 nonconsecutive days. Overall, sows in groups with Fitmix showed an increase in resting behavior and a greater decrease in the frequency of oronasofacial stereotypies than sows in groups fed by trickle feeding (P < 0.001). Sows in the group-housing system showed a decrease in the frequency of sham chewing (P < 0.001). Gilts showed a lower general activity and frequency of stereotypies than older sows in all of the systems (P < 0.001). In general, APP levels and productivity measures did not differ across systems. However, lameness and vulva injuries were more often detected in group-housing systems. Removal of animals was more frequent in sows with Fitmix than in the other systems. In conclusion, well-managed, group-housed sows seem to increase resting behavior and decrease stereotypies at similar productivity and tissue damage levels. However, higher quality stockmanship may be required for early detection and resolution of problems in group-housing systems. Nevertheless, long-term effects of group-housing systems on welfare should be further assessed before recommendations are made.     

Grassland improvement in Africa

Of all the continents, Africa has the highest proportion of land fit for agriculture. The principal vegetative cover on this land is grass, which, when it is well managed, gives good protection against erosion. Unfortunately, much of this grassland, and especially that north of the Sahara desert, is so heavily overstocked that it produces far too little forage for livestock, and scarcely any cover remains for protection of the soil. The very low productivity of the livestock is a major factor in the poor nutrition of the people—especially of young children suffering from kwashiorkor. It is still a common practice to keep as many cattle as possible, as an indication of the owner's social status and wealth. Consequently in Africa the commonest problems include a shortage of forage and inefficient use of what is available. This condition needs to be alleviated by increasing the output from native grassland and producing more forage on arable land. Each country needs a competent organization to cope with these problems. Improved practices such as rotational grazing and culling unproductive animals may increase the yield of the livestock from two to ten times. All such practices can be gradually adopted by the pastoral people, and by those doing mixed farming, with the help of their own technically trained youth. By the use of these practices, along with family planning to hold the population near the present level, it will be possible for the people to have an adequate diet and for the soil and other natural resources to be maintained.     

Effect of biochar on aerobic processes,enzyme activity,and crop yields in two sandy loam soils

Biochar added to agricultural soils may sequester carbon and improve physico-chemical conditions for crop growth, due to effects such as increased water and nutrient retention in the root zone. The effects of biochar on soil microbiological properties are less certain. We addressed the effects of wood-based biochar on soil respiration, water contents, potential ammonia oxidation (PAO), arylsulfatase activity (ASA), and crop yields at two temperate sandy loam soils under realistic field conditions. In situ soil respiration, PAO, and ASA were not significantly different in quadruplicate field plots with or without biochar (20 Mg ha^?1); however, in the same plots, volumetric water contents increased by 7.5 % due to biochar (P?=?0.007). Crop yields (oat) were not significantly different in the first year after biochar application, but in the second year, total yields of spring barley increased by 11 % (P??1, applied during two consecutive years, substantiated that biochar was not inhibitory to PAO and ASA as reference plots consistently showed lowest activities. For PAO, it was found that soil pH, rather than biochar rates, was a driving environmental variable. For ASA, the methodological approach was challenged by product sorption, but results did not suggest that biochar significantly stimulated the enzyme activity. Crop yields of maize in field experiments with 10–100 Mg biochar ha^?1 were unaffected by biochar except for a negative effect of the highest annual rates of 50 Mg ha^?1 in the first year after application. In conclusion, the present wood-based biochar poorly affected the measured microbial processes and generally resulted in similar crop yields in reference and biochar-amended soil plots.     

Soil structure and microbial activity dynamics in 20‐month field‐incubated organic‐amended soils

Soil structure formation is essential to all soil ecosystem functions and services. This study aims to quantify changes in soil structure and microbial activity during and after field incubation and examine the effect of carbon, organic amendment and clay on aggregate characteristics. Five soils dominated by illites, one kaolinitic soil and one smectitic soil were sieved to 2 mm, and each soil was divided into two parts and one part amended with ground rape shoots (7.5 t ha^?1) as an organic amendment. Samples were incubated in the field for 20 months with periodic sampling to measure water‐dispersible clay (WDC) and fluorescein diacetate activity (FDA). After incubation, WDC and FDA were measured on air‐dried 1–2‐mm aggregates. Tensile strength was measured on four aggregate classes (1–2, 1–4, 4–8 and 8–16 mm) and results used to assess soil friability and workability. Intact cores were also sampled to determine compressive strength. During incubation, the amount of WDC depended on soil carbon content while the trends correlated with moisture content. Organic amendment only yielded modest decreases (mean of 14% across all sampling times and soils) in WDC, but it was sufficient to stimulate the microbial community (65–100% increase in FDA). Incubation led to significant macroaggregate formation (>2 mm) for all soils. Friability and strength of newly‐formed aggregates were negatively correlated with clay content and carbon content, respectively. Soil workability was best for the kaolinite‐rich soil and poorest for the smectite‐rich soil; for illitic soils, workability increased with increasing organic carbon content. Organic amendment decreased the compression susceptibility of intact, incubated samples at smaller stress values (<200 kPa).     

Phosphorus adsorption and desorption in undisturbed samples from subtropical soils under conventional tillage or no‐tillage

The dynamics of P in soil is greatly influenced by the adsorption of phosphate onto Fe‐oxides. Access of phosphate to the surface of these minerals depends on the degree of soil aggregation, which in turn is influenced by soil management system. The primary purpose of this work was to investigate P adsorption and desorption in undisturbed and disturbed soil samples from an Ultisol (Rhodic Paleudult) and an Oxisol (Humic Hapludox) under conventional tillage (CT) or no‐tillage (NT). Phosphorus adsorption and desorption in undisturbed soil was studied by using a continuous flux system containing a P solution for adsorption measurements or deionized water and Mehlich‐I solution for desorption measurements. The Oxisol, which had higher clay, hematite, and goethite contents than the Ultisol, exhibited the highest maximum P adsorption capacity (P_max) values in disturbed samples. Also, the disturbed Ultisol samples had lower P_max values under NT than under CT. The undisturbed soil samples exhibited no significant differences in P adsorption between soil management systems, but P desorption was more marked under NT than under CT. The samples of Oxisol under NT exhibited lower P adsorption rates and higher P desorption rates than the CT samples of the same soil. The decreased P adsorption in undisturbed samples relative to disturbed samples suggests that P adsorption is influenced by physical properties of soil.