草业琐谈之十七--从"以草定畜"到"以畜定草"

"以草定畜"是求得草畜的供求平衡,防止草地因放牧过重而遭受破坏;同时也防止家畜营养不良,降低畜产品质量的基本原则.这是无可置疑的,这将是我们长期坚持的方向.     

Responses of yearling steers to different stocking rates on a subtropical grass-legume pasture

Despite potential benefits, limitations of individual tropical legumes have restricted development of sustainable grass-legume pastures in tropical and subtropical regions. Sowing mixtures of complementary legumes may overcome limitations of individual species. Responses of yearling steers grazing a mixture of three tropical legumes with bahiagrass (Paspalum notatum Flugge) were evaluated at three stocking rates under continuous grazing. Carpon desmodium (Desmodium heterocarpon [L.] DC.), which is persistent under grazing but often difficult to establish, was combined with the short-lived legumes aeschynomene (Aeschynomene americana L.) and phasey bean (Macroptilium lathyroides [L.] Urb.). Diet composition, as determined by microhistological analysis of fecal samples, and animal performance were evaluated in three grazing periods: summer 1987 and spring 1988 (2.0, 3.5, and 5.0 steers/ha) and summer 1988 (3.0, 5.3, and 7.5 steers/ha). Stocking rate did not affect percentage of the selectively grazed legumes, aeschynomene and phasey bean, in the diet. Average daily gain decreased linearly (P less than .05) with increased stocking rate, as is typical for grass pastures. Aeschynomene and phasey bean contributed to diets during the first summer, and carpon desmodium contribution was greater in the second summer. These results indicate that this pasture mixture can provide legume herbage from aeschynomene and phasey bean in the year of sowing and from carpon desmodium thereafter. Over the range of grazing pressures obtained, legume responses were generally consistent; thus, optimizing stocking rate for gain per hectare or for economic returns can be targeted without additional constraints to maintain the contribution of these legumes to grazing livestock.     

Effects of stocking density, flock size and management on the welfare of laying hens in single-tier aviaries

Management practices, stocking rate and flock size may affect laying hen welfare but there have been few replicated studies in commercial non-cage systems that investigate this. This study used a broad range of physical and physiological indicators to assess the welfare of hens in 36 commercial flocks. Six laying period treatments were examined with each treatment replicated 6 times. It was not possible to randomly allocate treatments to houses, so treatment and house were largely confounded. Three stocking rates were compared: 7 birds/m(2) (n = 2450), 9 birds/m(2) (n = 3150) and 12 birds/m(2) in either small (n = 2450) or large (n = 4200) flocks. In addition, at 12 birds/m(2), in both small and large flocks, birds were subjected to either standard (SM) or modified (MM) management. MM flocks had nipple drinkers and no nest-box lights. Bone strength, fracture incidence, heterophil:lymphocyte (H:L) ratio, live weight, organ weights, serum creatine, serum osmolality, muscle pH and faecal corticosterone were measured on samples of birds at the end of the rearing period and at the end of lay. During the laying period, mortality, production and integument condition were recorded at regular intervals. Birds housed at 9 birds/m(2) had higher mortality than birds housed at 12 birds/m(2) by the end of lay, but not higher than birds housed at 7 birds/m(2). Birds housed at 7 and 9 birds/m(2) had lower percent liver weight, and worse plumage condition than most of the 12 bird/m(2) treatments. Modified management tended to improve plumage condition. There were no clear effects of flock size on the welfare indicators recorded. At the end of the rearing period fracture incidence was almost negligible and H:L ratio was within a normal range. By the end of lay fracture incidence was 60% and H:L ratio was high, with no treatment effect for either measure. This, together with information on faecal corticosterone, feather loss and mortality, suggests that the welfare of birds in all treatments was relatively poor by the end of lay.     

新疆裕民县夏季草地合理放牧强度监测报告

通过开放式的定点样方笼移动法,监测当前放牧强度下草地的产草量与不同阶段的存量,以此估算夏草地的合理放牧强度。监测结果显示：裕民县禾草＋苔草＋杂类草类型夏草地的牧草产量为鲜草5238kg／hm^2,干草2017kg／hm^2实际利用率约为84％,超载率约40％,合理放牧强度为9．96羊单位／hm^2,放牧90d。     

应用牧草生长-消费模型分析牧民的放牧行为--作为对政府管理行为的建议

利用牧草生长与消费模型,从理论和实际两个方面,对实施"双权一制"后牧民放牧行为的选择进行了分析.结果显示,由于牧民对草场使用权的预期不高,所以当前牧民采取的放牧策略不但对于其自身收益不是最优的,而且对生态环境的破坏也是最严重的,出现了草牧场使用的"非理性"现象.预期不高的主要原因是政策不稳定、不连续,因此保持政策的连续性、稳定性和协调性至关重要,且政府应该提前一段时间与牧民续签草场承包合同,而不是等到承包期限到期时再续签.同时,不断明晰产权,用允许牧民转让与买卖草场的方法来防止牧民破坏草场是可行的,而且也是畜牧业的规模化和产业化经营所必须的.因此,尽快明晰产权,建立健全草牧场流转市场是解决草牧场使用"非理性"的根本途径.     

The effect of stocking rate and parasite control on the performance of replacement beef heifers on pasture

This study was designed to compare the animal production per unit area and per animal at 3 different stocking rates in combination with two deworming programs. Due to drought conditions, fecal egg output, serum pepsinogen levels and herbage larval counts were low throughout the grazing season. The beneficial effects of the strategic deworming program were, however, indicated by lower fecal egg counts and serum pepsinogen levels in the treated groups during most of the grazing season. Differences in weight gain, favoring the treated groups, were also observed and a clear effect of stocking rate was demonstrated. The lowest stocking rate groups continuously had the lowest egg output and serum pepsinogen levels and the highest average weight gain per animal. The experiment also clearly showed that the production per unit area increased with an increase in stocking rate. The medium and high stocking rate groups had a production per unit area exceeding that of the conventional stocking rate group by 15 and 45%, respectively.     

Using ultrasound technology to predict pork carcass composition

Twenty market hogs were evaluated with real-time ultrasound both before and after slaughter. Fat measures (n = 9) were taken at various body locations along with the longissimus muscle area measurement at the 10th rib. After live ultrasound, the hogs were slaughtered and the unsplit carcasses were measured with ultrasound at the same live ultrasound locations. After chilling, carcass measures were taken at the same locations using a backfat probe for fat measures and a loin eye dot grid for measuring the longissimus muscle area. One side of each carcass was fabricated into the four lean cuts, which then were expressed as a percentage of the side weight. The most appropriate prediction equation found was a two-variable equation (fat thickness at the anterior tip of gluteus medius and longissimus muscle area) with a R2 of .83 and a RSD value of 1.67. This prediction equation was verified on a different sample of 20 market hogs; actual vs predicted four lean cuts revealed that the prediction equation had a R2 of .63 and a RSD value of 2.04. Although some accuracy and precision was lost when this live animal prediction equation was incorporated in market hog evaluation, this equation offers producers an objective mechanism for identifying carcass merit in live hogs.     

Using red blood cell creatine concentration to evaluate the equine erythropoietic response

Red blood cell creatine concentration was examined to determine its association with the equine erythropoietic response. Studies were conducted on 9 healthy horses, 4 healthy ponies, 24 anemia horses, and 2 horses in which anemia was experimentally induced. A modified Jaffe reaction was used to measure RBC creatine concentration. The mean RBC creatine concentration of the 9 healthy horses was 5.72 +/- 0.42 mg/dl, and that of the 4 healthy ponies was 2.59 +/- 0.31 mg/dl. Density-separation of erythrocytes from the healthy horses revealed significantly higher (P less than 0.001) creatine content (7.72 +/- 0.57 mg/dl) in the young RBC populations than in the old RBC populations (4.03 +/- 0.27 mg/dl). The RBC creatine content was assayed in 19 hot-blooded horses which were anemic due to a variety of causes. Of these anemic horses, 12 with PCV between 25% and 30% had a mean RBC creatine concentration of 6.12 +/- 0.46 mg/dl. The 7 other anemic horses with PCV less than 25% had a mean RBC creatine value of 6.07 +/- 0.12 mg/dl. Bone marrow films were examined from 5 anemic horses and in the 2 horses in which anemia was experimentally induced. The RBC creatine concentration correlated positively (P less than 0.001) with the reticulocyte count in the bone marrow and negatively with the myeloid-erythroid ratio (P less than 0.001).     

Using the genomic relationship matrix to predict the accuracy of genomic selection

Estimated breeding values (EBVs) using data from genetic markers can be predicted using a genomic relationship matrix, derived from animal's genotypes, and best linear unbiased prediction. However, if the accuracy of the EBVs is calculated in the usual manner (from the inverse element of the coefficient matrix), it is likely to be overestimated owing to sampling errors in elements of the genomic relationship matrix. We show here that the correct accuracy can be obtained by regressing the relationship matrix towards the pedigree relationship matrix so that it is an unbiased estimate of the relationships at the QTL controlling the trait. This method shows how the accuracy increases as the number of markers used increases because the regression coefficient (of genomic relationship towards pedigree relationship) increases. We also present a deterministic method for predicting the accuracy of such genomic EBVs before data on individual animals are collected. This method estimates the proportion of genetic variance explained by the markers, which is equal to the regression coefficient described above, and the accuracy with which marker effects are estimated. The latter depends on the variance in relationship between pairs of animals, which equals the mean linkage disequilibrium over all pairs of loci. The theory was validated using simulated data and data on fat concentration in the milk of Holstein cattle.     

白三叶人工草地数量化管理指数的研究

在综合分析影响白三叶人工草地生长发育的管理因子基础上,选择了4个管理因子,进行封闭型管理因子梯度试验设计,模拟草地管理过程。并采用数量化理论I方法,以白三叶单株产草量为因变量,以管理因子为自变量,建立管理指数的回归模型,通过逐步回归筛选出主导因子,以主导因子建立预测方程,编制出了白三叶人工草地数量化管理指数表。该管理指数表经检验符合精度要求,可以对白三叶人工草地进行管理效率的统一评价。     

加强放牧管理控制血吸虫病效果试验

岳阳县下湘良湖湖洲枯水季节有草洲1.5万余亩,由于气候温和多雨,牧草生长茂盛,为发展草食动物提供了牧草资源,也是血吸虫中间宿主钉螺繁殖孳生的温床.除涨水季节牧草被淹外,日均有1 000余牛羊在湖洲上放牧,感染血吸虫病并传播病原,是我县血吸虫病疫情最为严重的地区之一,1997年我们在此设点,开展加强放牧管理控制血吸虫效果试验,通过4年的工作,人、畜血吸虫病感染率分别由11.3%和7.8%下降到5.2%和3%,人均年收入增加800元,取得了良好的效果与效益.     

Practice management software for the equine practitioner.

Practice management software benefits the equine practitioner in many ways. Ready access to patient records, rapid entry and lookup of clinical findings, easy invoicing and monitoring of revenues, inventory management, rapid search and sorting of data, reminder and recall maintenance, and integrated word processing are just some of the software functions that assist the successful practitioner. Computer use in veterinary practice may have seemed to many to be a gimmick at one time. Now that computers have become a part of our everyday life, it is clear that they can be an essential component of the modem, successful, and profitable equine practice.     

Development of a new approach of pasture management to control Rhipicephalus microplus infestation

Tropical Animal Health and Production - Despite several decades of chemical control, the cattle tick Rhipicephalus microplus remains an important constraint for cattle farmers. The regular use of...     

Using ultrasound measurements to predict body composition of yearling bulls

Carcass traits have been successfully used to determine body composition of steers. Body composition, in turn, has been used to predict energy content of ADG to compute feed requirements of individual animals fed in groups. This information is used in the Cornell value discovery system (CVDS) to predict DM required (DMR) for the observed animal performance. In this experiment, the prediction of individual DMR for the observed performance of group-fed yearling bulls was evaluated using energy content of gain, which was based on ultrasound measurements to estimate carcass traits and energy content of ADG. One hundred eighteen spring-born purebred and crossbred bulls (BW = 288 +/- 4.3 kg) were sorted visually into 3 marketing groups based on estimated days to reach USDA low Choice quality grade. The bulls were fed a common high-concentrate diet in 12 slatted-floor pens (9 to 10 head/pen). Ultrasound measurements including back-fat (uBF), rump fat, LM area (uLMA), and intramuscular fat were taken at approximately 1 yr of age. Carcass measurements including HCW, backfat over the 12th to 13th rib (BF), marbling score (MRB), and LM area (LMA) were collected for comparison with ultrasound data for predicting carcass composition. The 9th to 11th-rib section was removed and dissected into soft tissue and bone for determination of chemical composition, which was used to predict carcass fat and empty body fat (EBF). The predicted EBF averaged 23.7 +/- 4.0%. Multiple regression analysis indicated that carcass traits explained 72% of the variation in predicted EBF (EBF = 16.0583 + 5.6352 x BF + 0.01781 x HCW + 1.0486 x MRB - 0.1239 x LMA). Because carcass traits are not available on bulls intended for use as herd sires, another equation using predicted HCW (pHCW) and ultrasound measurements was developed (EBF = 39.9535 x uBF - 0.1384 x uLMA + 0.0867 x pHCW - 0.0897 x uBF x pHCW - 1.3690). This equation accounted for 62% of the variation in EBF. The use of an equation to predict EBF developed with steer composition data overpredicted the EBF predicted in these experiments (28.7 vs. 23.7%, respectively). In a validation study with 37 individually fed bulls, the use of the ultrasound-based equation in the CVDS to predict energy content of gain accounted for 60% of the variation in the observed efficiency of gain, with 1.5% bias, and identified 3 of the 4 most efficient bulls.     

Effect of stocking rates and anthelminthic treatments on weight gains in weaned Nellore cattle on improved pasture in the Brazilian cerrado

Summary The results are presented of 6 years of field trials with weaned Nellore cattle on improved pasture in the midwest of Brazil, using 2 stocking rates and 4 anthelminthic treatment regimes. The most profitable regime included treatments in May, June and September, which yielded an additional 41 and 42 kg of liveweight on the 2 stocking rates. No significant additional gains were obtained by treating during the rainy season, or by treating animals more than 24 months of age. The higher stocking rate (1.8 AU/ha) proved excessive on the improved pasture which deteriorated during the 6 year experimental period, yielding suboptimal liveweight gains.

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Efecto De La Tasa De Carga Animal Y Tratamientos Antihelminticos Sobre La Ganancia De Peso De Ganado Destetado Nellore En Pasturas Mejoradas En El Cerrado Brasileno

Resumen Se presentan resultados de 6 años de pruebas con ganado Nellore destetado pastoreando praderas mejoradas en el oriente medio de Brasil, usando 2 tasas de carga animal y 4 regimenes de tratamiento con antihelmínticos. El mejor régimen fue aquel que incluyó tratamientos en mayo, junio y septiembre, mediante el cual se obtuvo 41 y 42 kg adicionales de peso corporal bajo los 2 tipos de carga. No se obtuvo ganancias adicionales cuando los animales se trataron durante la estación lluviosa, o cuando se trataron animales mayores de 24 meses. La carga más alta (1.8 UA/ha) fue deletérea para la pradera mejorada, la que se deterioró durante los 6 años de período experimental, rindiendo tasas inferiores de ganancia de peso.

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Influence Des Taux De Charge Et Des Traitements Anthelminthiques Sur Les Gains De Poids De Bovins Nellore Sevres, Entretenus Sur Paturage Ameliore Du Cerrado Bresilien

Résumé Des essais sur le terrain ont été réalisés pendant 6 ans avec des bovins sevrés de race Nellore, sur pâturage amélioré dans le moyen ouest brésilien. Deux taux de charge ont été utilisés et quatre traitements anthelminthiques ont été administrés aux animaux. Les traitements les plus profitables ont été ceux effectués en mai, juin et septembre avec un rendement additionnel de 41 et 42 kg de poids vif avec les deux taux de charge. Aucun gain additionnel significatif n'a été obtenu avec un traitement pendant la saison des pluies, ou chez des animaux âgés de plus de 2 ans. Le taux de charge le lus élevé (1,8 AU/ha) s'est revélé excessif sur le pâturage amélioré qui s'est détérioré pendant les 6 ans d'expérience, avec un rendement inférieur en gain de poids vif.

     

Efficacy of the nematophagous fungus Duddingtonia flagrans in reducing equine cyathostome larvae on pasture in south Louisiana

The effectiveness of Duddingtonia flagrans in reducing the free living third stage larvae (L(3)) of equine cyathostomes on pasture when fed to horses has been demonstrated in cold temperate climates. The objective of this experiment was to assess the efficacy of D. flagrans against equine cyathostomes in the subtropical environment of southern Louisiana. Fecal pats were prepared by mixing feces obtained from a parasite-free horse fed D. flagrans at a dose of approximately 2 x 10(6) spores kg(-1), with feces containing cyathostome eggs from a parasitized horse. Control pats contained feces from a parasite-free horse mixed with feces containing cyathostome eggs. The fecal pats were placed on pasture in six replicates at 4-week intervals from March 1997 until January 1998. Comparison of recoveries of L(3) from non-treated control pats in the field with non-treated coprocultures maintained in the laboratory indicated that L(3) survival on pasture was reduced during the months of May, June, July, August and September. The efficacy of the fungus was determined by L(3) recovery from grass surrounding the fecal pats of treated and control groups. D. flagrans significantly reduced L(3) during the months of April, May, and October 1997 to January 1998 (range 66-99% reduction, p=0.0001), and for the year as a whole (p=0.0001).     

Assessment of possible methods for estimating the stocking density of sheep being carried on commercial vehicles

Five methods for estimating the stocking density of sheep confined in a pen were assessed. The pen (2.35 m x 3.01 m) simulated the pens on a normal road transporter. The trial used 50 lambs (average weight 34 kg) of mixed sex and breed, held at five stocking densities--0.466 to 0.824 m2/100 kg or 214 to 121 kg/m2--covering the range used in commercial practice, and 14 assessors, all experienced in handling animals. The best method was that based on the girth measurement of a sample of animals to estimate liveweight and a count of the animals in the pen. The methods based on using a moveable gate to take up free floor space, assessing the difficulty of moving through the pen of animals, using photographic scales, and counting the numbers of sheep across transects were generally less successful.