舍饲和放牧BMY牛血液生化指标比较

[目的]为了解不同饲养管理条件下,BMY牛血液生化指标的变化情况,以到达补充BMY牛的基础性资料,为BMY牛的人工饲养、疫病防治提供理论依据的目的。[方法]采用试剂盒对20头不同饲养管理条件下的BMY年母牛的血液生化指标进行了检测。[结果]显示:舍饲牛的STB、A/G、LDL、GLU、Crea和P等指标显著高于放牧组,放牧牛的GLO、ALT、AST/ALT、GGT和TG等指标显著高于舍饲牛(P<0.05),TP、HGB、ALP、BUN、URIC、T-CHOL、Ca、HDL在两组间差异不显著(P>0.05),舍饲牛的血液生化指标的变异系数要明显小于放牧牛。[结论]舍饲BMY牛的血液生化指标明显要优于全放牧条件下的BMY牛。     

海南坡鹿对采食部位的选择与饲草酸性洗涤纤维含量的相关性

在海南大田国家级自然保护区围栏内用食痕法(evidence of feeding on forage)观测海南坡鹿Cervus eldi hainanus(简称坡鹿)对18种草本和18种灌木类饲草的采食部分占整株草本植株或占整枝灌木主枝条的尺寸比,同时测定各饲草的酸性洗涤纤维(ADF)含量.结果显示,按旱季与雨季的(全年)平均值,坡鹿对草本类饲草的采食尺寸比为49.29%,对灌木类饲草为57.3%;草本类饲草的ADF含量为9.91%,灌木类饲草为9.19%;无论草本还是灌木类,坡鹿的采食尺寸比随饲草ADF含量的增加而显著降低.研究表明,在大田自然保护区围栏内,坡鹿对ADF含量在10%以上的饲草不喜食,饲草纤维物质含量是坡鹿在围栏内扩充采食部位以增加营养摄入量的限制性因子,在旱季种植并收割饲草投喂坡鹿时,应避免其纤维物质含量增高.     

Managing Grazing Intensity Linked to Forage Quantity and Quality Trade-off in Semiarid Rangelands

Knowledge of herbivory tolerance of dominant plant species and their responses to varying grazing intensity is required for sustainable grazing management in semiarid rangeland ecosystems. In a field experiment, we studied the effects of simulated grazing 0%, 30%, 50%, and 80% leaf removal (control, partial, intermediate, and heavy leaf removal) of three dominant perennial legumes: Astragalus cyclophyllon, Astragalus effuses, and Hedysarum criniferum in semiarid rangelands of southwestern Iran for 2 yr and tested 1) differential herbivory tolerance in terms of regrowth ability of belowground and aboveground biomass (AGB), fecundity, and nonstructural carbohydrate reserves; and 2) trade-off between forage quantity and quality—less defoliated plants produce larger amount of biomass with less forage quality and vice versa. The results showed a reduction in AGB and reproduction in each of the three plants. However, three forbs exhibited some sort of variations in shoot and root growth, reproduction and forage quality under intermediate and heavy leaf removal. Leaf removal in individuals of A. effusus and H. criniferum are more likely to compensate for tissue loss by allocating the available resources to the expansion of root biomass, at the cost of AGB and reproductive effort. Leaf removal also led to an increase in forage quality in each of the three forb species, depending on the level of height removal. The control plant had a higher amount of biomass production and lower amount of crude protein compared with heavy leaf removal treatments (i.e., 80%), by contrasting responses of acid detergent fiber and neutral detergent fiber, indicating a trade-off between forage quality and forage quantity. The results indicate that there is a balance among forage quantity, quality, and regrowth ability of belowground and aboveground tissues in intermediate leaf removal treatments of these forb species. This balance is used to develop principles for grazing management of steppe rangelands because such a regime meets different criteria including forage quantity, quality, and nonstructural carbohydrate reserves.     

Veld of the karoo areas

The Karoo areas are generally arid to semi‐arid with rainfall varying from less than 100 mm in the west to 400 mm in the east. The topography is mainly flat to undulating and the soils generally shallow and stony. There are 16 veld types present. Typcial Karoo veld is characterised by a dominant sparse to dense short shrubby vegetation (karoo bushes), interspersed to a variable degree, by short grass species and taller shrubs. Succulents are dominant in certain parts. These constituents exhibit different phenological rhythms of which the karoo bushes are largely vernal and autumnal and the grass aestival. Fodder and nutrition supply varies according to season and rainfall. A large numer of insect pests afflict Karoo vegetation. Stock diseases and physiological disturbances caused by certain species, are prevalent. Merino and Dorper sheep are the main defoliating agents of Karoo veld.     

Grassland research priorities: Ideas for the future

Abstract

Four levels of available dry matter (DM) were maintained on a continuously grazed irrigated Midmar Italian ryegrass (Lolium multiflorum Lam.) pasture by means of a “put‐and‐take” grazing procedure. The pasture was stocked with three successive sets of weaned lambs in winter, spring and early summer respectively. The relation between average daily gains (ADG) and available DM was positively linear At equivalent levels of available DM, gains were greater in spring than in either the winter and summer periods (P ≤0,01), but there were no differences in gains between winter and summer. There was a negative linear relation between average stocking rate (the rate required to achieve a given level of herbage availability) and available DM. Stocking rates in spring and summer were not significantly different, but both were higher (P≤0,01) than those in winter. Within the range of the differential treatments applied, relations between stocking rate and ADG were negatively linear, and there was an interactive effect (P≤0,01) between stocking rate and grazing period. Changes in ADG with a unit change in stocking rate were greatest in winter, intermediate in summer and least in spring. Gains/ha were curvilinearly related to available DM. The curves indicate that the amounts of available DM required for maximum gains/ha were least in spring, intermediate in summer and greatest in winter.

From a serial cutting trial conducted concurrently with the grazing, a growth rate curve was developed for Midmar ryegrass. This curve had two maxima, with the maximum growth rate in spring being more than double that in autumn. The in vitro digestible organic matter content and crude protein content decreased from 80,6% and 24,1% in autumn to 63,1% and 10,6%, respectively, in summer. Crude fibre content increased from 10,1 % in autumn to 30,1 % in summer.     

Evaluation of veld potential in east griqualand using beef cattle under two grazing management systems

Abstract

Beef production from veld, in the short term, was found to be greater under a continuous grazing system than under a rotational grazing system. Average daily gains decreased from a maximum in late‐spring and the highest three‐year mean value was 0,5 kg/animal/day. Livemass gains/ha were highest at a stocking rate of 2,2 animals/ha and were 131,4 kg/ha under continuous grazing and 88,6 kg/ha under rotational grazing. Estimated mean maximum gains/ha were 0,78 kg/ha/day at a stocking rate of 2,5 animals/ha under continuous grazing and 0,55 kg/ha/day at a stocking rate of 1,7 animals/ha under rotational grazing. However, optimum economic stocking rates were estimated to occur below those where beef production/ha was maximum.     

Exploratory trials on reinforcement of veld with legumes in the south‐eastern transvaal highveld

Abstract

The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement.     

Research note: Grazing‐index method procedures of vegetation surveys

Abstract

In the past, veld condition in the Karoo was assessed using the ecological index method. This recently changed to the grazing‐index method on account of the differently estimated grazing‐index values being used. The principles governing the method of survey remain the same. The method employs canopy‐spread‐cover strikes to record the species composition of different sites. By appropriate management of these line‐point data, different sites can be compared with one another by employing the Z‐index of agreement (similarity).     

Measuring the impact of indigenous herbivores: reply to Kerley andLandman

Pteronia paniculata is an indigenous, unpalatable shrub that invades mismanaged Karooveld, resulting in degraded rangelands with low species diversity and grazing potential. We conducted a series of trials in the Succulent Karoo Randteveld near Barrydale to determine if the uniform defoliation of P. paniculata dominated vegetation at two heights (0.05 m and 0.20 m above ground level) using a brush-cutter and, in one trial, application of a second cut will improve the plant species composition, productivity and grazing capacity of the veld. Brush-cutting treatments and the uncut control all resulted in a change in species composition towards greater species diversity and more palatable species and an average increase of 540 kg ha^?1 (28%) in above-ground biomass over four years. It appears that there was a pervasive improvement in species composition associated with a general decline in the cover and abundance of P. paniculata over the time-scale of the present study that was not influenced by the defoliation treatments, except for the 1996-cut treatment where the cover of P. paniculata increased. The absence of propagules of palatable species in the soil seed bank and competition from P. paniculata (a long-lived, perennial shrub) are assumed to be among the main reasons for the lack of response of the vegetation community to the defoliation treatments. Brush-cutting (in the absence of reseeding), aimed at reducing the dominance of unpalatable karoo shrubs, was more costly but not significantly better than long-term resting in improving veld composition or forage production.     

The influence of urine and dung deposition on patch grazing patterns of cattle and sheep in the Southern Tall Grassveld

Abstract

The effect of urine and dung deposition on the patch grazing patterns of cattle and sheep in the Southern Tall Grassveld was investigated using an experiment with four treatments, viz. artificial urine, fresh cattle dung, fresh sheep dung, and a control. Cattle and sheep preferentially grazed the sward surrounding and within urine deposits for six months after deposition. Cattle rejected herbage from both cattle and sheep dung patches for six months after deposition. Sheep initially rejected the herbage from cattle dung patches, but their grazing patterns were no longer affected at six months after deposition. Sheep grazing tended not to be influenced by sheep dung. Urine deposition may consequently be an important factor in patch initiation and patch development.