不同季节南方人工改良草地载畜量研究

在南方高海拔山区，研究不同放牧强度（7．5、15、30和45羊／hm2）和放牧季节对人工改良草地和家畜生产性能的影响，对不同季节人工改良草地适宜载畜量进行探讨。结果表明：不同放牧强度对地上现存量和家畜生产性能有显著影响（P〈0．05）。地上现存量（Yh，g／m2）与放牧率（S，羊／hm2）之间呈线性负相关；日增重（Ya...     

内蒙古典型草原草畜系统适宜放牧率的研究Ⅰ.以绵羊增重及经济效益为管理目标

(1)绵羊个体增重与放牧率呈线性负相关,个体最大增重临界放牧率,因季节不同而变化,随着个体增重与放牧率回归系数b绝对值的增大而降低,以始、终放牧期间所得临界放牧率最小,(2.04羊/hm²)。(2)公顷增重与放牧率的关系符合二次曲线,在达到公顷最大增重以前,随着放牧率的增大而增大,之后则随着放牧率的增大而下降,平均543羊/hm²。(3)公顷最大增重并不一定获取公顷最大利润,主要视买卖价格及其差值而定。(4)以冷蒿小禾草为主的退化草原,宜以个体最大增重的适宜放牧率作为管理标准,以使该类草原在利用中得以恢复。     

Absence of a weight gain response to Vitamin B12 supplementation in weaned dairy heifers grazing pastures of marginal cobalt content

Aim. To obtain information on serum and liver vitamin B₁₂ and urinary methylmalonic acid concentrations as diagnostic tests to predict a weight gain response to supplementation with vitamin B₁₂ in young dairy cattle when grazing pasture of low cobalt content.

Methodology. Forty dairy cattle (12 Friesian, 14 Friesian × Jersey and 14 Jersey) were allocated to two equal sized groups, treated and untreated, based on liveweight. At monthly intervals for 14 months, all animals were weighed, their serum and urine sampled, their liver biopsied and the pasture sampled from the paddocks they were grazing and going to graze. Serum and liver were assayed for Vitamin B₁₂ concentrations. For the first 5 months of the trial, urine was assayed for methylmalonic acid concentrations. Both washed and unwashed pasture samples were assayed for cobalt concentrations.

Results. No weight gain response occurred to Vitamin B₁₂ supplementation in young growing cattle grazing pasture with a cobalt concentration of 0.04-0.06 mg/kg DM. For 5 months of the trial, liver Vitamin B₁₂ concentrations from untreated calves were in the range 75-220 nmol/kg and serum vitamin B₁₂ concentrations were as low as 72 pmol/1. There was no associated growth response to supplementation.

Conclusion. Further trials involving young cattle grazing pastures with cobalt concentrations less than 0.04 mg/kg DM are required to reliably determine liver and serum Vitamin B₁₂ concentrations at which growth responses to Vitamin B₁₂ or cobalt supplementation are likely under New Zealand pastoral grazing conditions.     

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.     

小麦/玉米/大豆套作和施氮对玉米生长及氮吸收利用的影响

为研究小麦/玉米/大豆套作种植模式和施氮水平对玉米生长、产量及氮吸收利用规律的影响,进行了2个种植模式(玉米单作和小麦/玉米/大豆套作)和2013年3个施氮水平(0,180,360 kg/hm²)及2014年4个施氮水平(0,90,180,270 kg/hm²)的双因素随机区组实验,以期揭示施氮及套作对玉米产量的影响规律,为进一步提高小麦/玉米/大豆套作体系产量提供理论依据。研究结果表明,1)在N₀及N₉₀处理下套作玉米的产量分别比单作低20.5%、7.5%,表现为套作劣势,而在N₁₈₀、N₂₇₀、N₃₆₀处理下,套作玉米与单作玉米产量无显著差异。2)单/套作玉米地上部生物量在各生育时期均表现为随施氮量的增加先增加后略有降低,干物质积累速率均在吐丝期到收获期达到最大。相对单作,各施氮处理下小麦对套作玉米的茎秆生长均产生显著不利影响,在拔节期套作玉米茎秆生长率比单作低12.5%,这种影响随施氮量的增加而减小,在施氮量到达180 kg/hm²后影响不显著。3)在N₀、N₉₀处理下,单作玉米花期氮积累量在生殖生长期更多转运到籽粒,而在N₁₈₀、N₂₇₀、N₃₆₀处理下,套作花期前氮积累量转移到籽粒的比例更高。而两种模式下均以施氮180~270 kg/hm²下氮转运指标最优,这说明在该施氮条件下最有利于提高植株氮素转运机能。综上所述,适量施氮有利于稳定小麦/玉米/大豆套作种植模式中的玉米产量,提高氮的吸收转运效率,减轻小麦对玉米生长和氮吸收利用的影响,本研究条件下,套作玉米施氮量以180 kg/hm²为宜。     

Rumen fermentation and liveweight gain in beef cattle treated with monensin and grazing lush forage

Objective To determine the prevalence of subacute rumen acidosis (SARA) in beef cattle grazing lush pasture and the effect of monensin on reducing SARA and improving animal performance. Design Commercial Angus and Murray Grey steers received a monensin slow‐release capsule (n = 19) or remained untreated (n = 19). Cattle grazed an oats crop or tetraploid ryegrass pasture for a total of 91 days. Rumen fluid pH, volatile fatty acids (VFA) and lactic acid concentrations and body weight data were collected prior to treatment and again 28, 56 and 91 days after treatment. Changes in measures over time were analysed using mixed model repeated measures analysis. Differences in average daily gain between treatment groups were determined. Results The prevalence of SARA was low during the study, with only one animal satisfying criteria for SARA at one time point. Cattle treated with monensin capsules were 11.9 kg heavier at the completion of the study compared with untreated controls (414.5 ± 3.88 kg vs 402.6 ± 4.03 kg, P = 0.04). Rumen VFA and L‐ and D‐lactate levels did not differ between cattle treated with monensin and untreated cattle. However, the ratio of propionate to acetate plus two times butyrate was higher (P < 0.001) when cattle were treated with monensin. Conclusions Subacute rumen acidosis was not consistently detected under the conditions of the study. The higher body weight of cattle treated with monensin may have been due to improved energy utilisation of the pasture, indicated by increased propionate proportions in the rumen, rather than prevention of SARA.     

草地家畜放牧系统草畜平衡调控技术研究

划区轮牧是提高草地家畜系统产出和实现草地畜牧业可持续发展的最佳放牧制度。放牧管理的方针是把草层高度(草地牧草生物量)保持在最利于草地生长、草地质量和家畜采食的范围内。饲料计划依据不同的时期和管理层次分为饲料概算、饲料预算和放牧计划三个水平。饲料供给由草地牧草生长速度、草地生物量和补饲确定,而饲料需求由牧场家畜数量及其生产指标水平决定。实行季节畜牧业的经营管理策略,使草地供给和家畜需求达到季节和全年的动态平衡。系统管理和效益的三个关键是划区围栏、畜群结构和载畜量。     

草原放牧系统持续管理试验研究:试验设计及放牧率对草-畜系统影响分析

在内蒙古典型草原区中国科学院草原生态定位站研究不同放牧率、放牧方式和放牧季节对草原植物和家畜生产的影响。结果表明,地上现存量随着放牧率的增加而降低,但达到峰值的日期提前了。地上生物量与放牧率无明显趋向性变化。家畜增重随着放牧率的增大而下降,公顷总增重与放牧率成二次曲线关系。将放牧率对草原生产力的动态确定为可持续放牧率和改良放牧率。     

The horizontal barrier effect of stems on the foraging behaviour of cattle grazing five tropical grasses

The rate of nutrient intake (RNI) is a primary determinant of animal performance in grazing cattle and depends on both diet quality and instantaneous intake rate (IIR). In turn, diet quality and IIR are a function of the foraging behaviour of the animal (selectivity, bite mass and bite rate) and the characteristics of the sward. In this study we evaluated the effect of the stem density and the tensile resistance of stems on the foraging behaviour of cattle grazing tropical pasture species. The methodology involved the use of small sown microswards offered to tethered cattle. The experiment consisted of a factorial combination of five tropical grasses [Bothriochloa pertusa (Bp), Chloris barbata (Cb), Chloris gayana (Cg), Cynodon dactylon (Cd) and Heteropogon contortus (Hc)] and three stem densities (0, 400 and 800 stems m^− 2). Bp and Cd had stems of significantly lower tensile resistance (19 and 15 N respectively) (Group 1) than those of Cb, Cg and Hc (110, 211 and 167 N respectively) (Group 2). The steers avoided stems of Group 2 and thus, reduced bite area, bite mass, IIR and RNI as stem density increased. However, the animals did not avoid stems of Group 1 and there was no effect of stem density on any of the foraging behaviour variables when cattle grazed species in Group 1. These results confirm that RNI and plant part selection is closely associated with the tensile resistance of the stem.     

苗期追施氮肥对沙地燕麦生长特性及叶绿体色素含量的影响

在内蒙古通辽市珠日河牧场沙化草地,通过苗期追施0、10.00、20.00、30.00、40.00kg/hm~2氮肥(纯N,下同)对沙地燕麦(Avena sativa)分蘖力、株高、茎粗、功能叶长度、植株重量及叶绿体色素含量的影响,分析沙地燕麦苗期追施氮肥的最佳用量。结果表明:苗期追施氮肥在10.00~40.00kg/hm~2燕麦生长指标均表现为先增加后降低的变化趋势,其中,分蘖率、株高、叶长、干重和鲜重值均在追施30.00kg/hm~2氮肥时达到最大,且均与对照差异极显著(P0.01);茎粗则在追施20.00kg/hm~2氮肥时达到最大,且与对照差异极显著(P0.01);苗期追施氮肥增加到40.00kg/hm~2时,燕麦各生长指标较追施30.00kg/hm~2氮肥降低,但差异均不显著;苗期追施10.00~40.00kg/hm~2氮肥均促进叶绿体色素合成,且叶绿素a、叶绿素b和类胡萝卜素含量均在追施30.00kg/hm~2氮肥时含量最高,并均与对照差异极显著(P0.01)。由此说明,在科尔沁沙地苗期追施30.00kg/hm~2氮肥,明显促进燕麦生长及叶绿素体色素合成。     

张掖地区围栏育肥牛场防风墙后不同风速对肉牛场环境及肉牛生产性能的影响

本试验旨在研究防风墙在不同遮蔽距离的减风效果以及风速对牛生产性能的影响。选取初始体重差异不显著的40头牛随机平均分布在选定的4个牛栏中,根据牛栏距防风墙的远近分为2组,测定其日增重。同时根据牛场实际条件和天气状况布置测点,对测点的风速、温度等其他环境指标和肉牛的产热进行现场实测与计算分析。结果表明:安装防风墙的围栏育肥牛场在墙后1.2 m高度,水平遮蔽距离10倍墙高的范围内,可折减风速40%～70%;防风墙后的最佳遮蔽区域是在距离防风墙2～4倍墙高处、水平遮蔽距离6倍墙高距离范围内,风速折减效果明显,最大折减率可达70%左右;肉牛平均体重为480 kg,在外部风冷指数为-15.61的条件下,安装防风墙的围栏育肥牛场的风冷指数可以降低到-9.00,每头牛每小时可减少热量损失3.31 MJ;由于距离防风墙的远近不同,肉牛日增重相差0.15 kg/(头·d),但差异不显著(P>0.05)。     

BMY热带肉牛屠宰测定报告

热带牛（BMY）生长快，产肉性能好。在完全放牧条件下。18月龄体重可达300kg以上，18月龄和30月龄牛的平均屠宰率达55.53%，平均净肉率为46.30%。分别比云南黄牛提高18.10和21.92个百分点，优质切块占胴体重的39.30%，且抗蜱耐热，适应性广，不仅能适应炎热的气候，而且在冰天雪地的环境中表现也较好。     

5个草地型草地牧草的生长速率和养分动态研究

在牧草生长季节(5~9月)对小哨牧场放牧演替形成的5个草地型草地的牧草进行生长速率、牧草产量及养分的逐月观测,生长速率测定显示,白三叶+东非狼尾草和东非狼尾草+非洲狗尾草两个草地型草地均出现两个生长峰值,分别在6月和9月,其余3个草地型草地只有一个生长高峰。干物质产量和牧草养分测定结果表明,白三叶+东非狼尾草和白三叶+非洲狗尾草+画眉草两种草地型草地表现最好,可以在气候环境条件类似的地区推广种植利用;白三叶+画眉草和白三叶+非洲狗尾草两种草地型草地表现优良,可以在草地改良中,根据当地实际情况选择性地加以种植;东非狼尾草+非洲狗尾草型草地表现较差,不提倡种植。     

壳聚糖对肉牛生长性能及营养物质消化率的影响

试验旨在研究壳聚糖(chitosan,CHI)对肉牛生长性能及营养物质表观消化率的影响。选择体重、月龄接近,健康无病的24头西门塔尔育肥公牛,随机分为3个日粮处理组,每组8头牛,饲养试验分前、中、后三期,每期28 d,共84 d。三组日粮分别是在基础日粮中添加0、500和1 000 mg/kg的壳聚糖配制而成。结果表明:试验全期500 mg/kg壳聚糖组的平均日增重(ADG)和日采食量(ADFI)最高、料肉比(F/G)最低;日粮添加500 mg/kg壳聚糖可提高肉牛干物质、蛋白质、能量和钙表观消化率。说明日粮中添加500 mg/kg壳聚糖可提高肉牛营养物质的消化率,进而促进肉牛的生长。     

刈牧后休闲期对草地牧草生产的影响

通过不同间隔时期对多年生黑麦草、白三叶混播草地牧草产量的监测与分析,得出随着休闲期的增加,青绿物质和死亡物质均呈现上升趋势,在较低和较高草地牧草现存量下都会降低牧草生长率。     

Factors affecting pregnancy rate in Holstein-Friesian cattle mated during summer in a tropical upland environment

SUMMARY The relationships between some environmental factors and reproductive rates of dairy cattle during summer in a tropical upland area were studied using records for Holstein-Frieslan milking cows and non-lactating growing helfers maintained at the Kalri Research Station on the Atherton Tableland in north Queensland. The Station is situated in a tropical upland environment with warm, wet summers and dry, cool winters. Data were collected over a 12-year-period (1977 to 1988) for cows grazing nitrogen (N)-fertilised grass pastures and receiving either no supplement or about 3.5 kg molasses/cow/day. Cattle were mated over a 10-week period starting from mid-January to early February, with 32 to 36 cows and 5 to 42 heifers used in each year. There was considerable variation among years in the pregnancy rate after 3 Inseminations, with a low of 39% and a high of 94% pregnancy. This variation from year to year was reduced for cows grazing pastures receiving 300 kg N/ha/yr after molasses feeding commenced in 1984–85. Pregnancy rates after molasses Introduction were higher for cows grazing pastures receiving 300 compared with 100 kg N/ha/yr. Pregnancy rate in cows and heifers was reduced from 80 to 55% as mean daily maximum temperature increased from 26°C to 27.5°C. At mean maximum temperatures above 27°C for cows and 27.6°C for heifers pregnancy rates to 3 Inseminations were consistently below 60%. Much of the year to year variation in pregnancy rate was related to rainfall during the mating period. There was a positive association between pregnancy rate and rainfall up to 1000 mm, and this was associated with differences in growth rate of pasture. In years of very high rainfall, above 1500 mm, there was a depression in pregnancy rate, which may be related to the intense humidity in very wet years causing heat stress in cows and associated problems such as feet infections, or a deterioration in pasture quality. We conclude that much of the variation in pregnancy rate during summer may have been related to heat stress and the level of feed supply in the form of pasture and supplements.     

A comparison of highveld fodders and fodder flows for growing out long yearling steers

Abstract

A fodder flow/animal experiment 40,8 ha in extent (7,5 ha irrigated), with 19 paddocks, was carried out over a two and a half year period.

The aims were: firstly, to compare fodder crops within seasons, and fodder flows over three seasons (winter‐spring‐summer), by means of pasture and animal parameters; secondly, to make economic comparisons between different fodder flows, for growing out beef steers.

The conclusions were that: Digitaria eriantha ssp. eriantha is superior to Eragrostis curvula cv. Ermelo for animal production; maize residue gives economically favourable results due to low costs and compensatory growth of cattle; an irrigated pasture providing fodder in more than one season of a flow, for example, Festuca foggage — Festuca pasture — Digitaria pasture, gives a very profitable fodder flow, because the costs of production are divided between two seasons; dryland fodder flows with the sequence maize residue — silage or hay — Digitaria or, with silage or hay replacing the maize residue, were also very profitable; and, the fodder flow giving the highest livemass gain per steer, is not necessarily the most economic. Different kinds and classes of livestock require different fodder flows.     

The Effect of Management Factors on the Seroprevalence of Anaplasma marginale in Bos indicus cattle in the Mexican Tropics

A cross-sectional study with a two-stage design and proportional distribution was carried out to determine the effect of management factors on the seroprevalence of Anaplasma marginale in Bos indicus cattle in the Mexican tropics. Serum was obtained from 384 cattle aged 1-2 years on 92 farms. The number of samples was proportionally distributed according to the number of farms in eastern Yucatan. Antibody activity against A. marginale was assessed using the card agglutination test. A primary screening using a 2 x K contingency table of the exposed variables with the outcomes was performed. All variables for which p < 0.20 were included in a fixed-effects log regression. The seroprevalence in the cattle was 69.75% (SE +/- 0.02). Sixty-four per cent of the farms had a seroprevalence > or = 75%. The risks related to managemental factors were stocking density ( > or = 1 animal/ha, OR = 10.94), type of acaricide (pyrethroids, OR = 3.8), dipping interval ( > 60 days, OR = 0.13) and type of veterinary instruments used (needles, scalpels, ear tattoos, and dehorners, OR = 0.17).     

Long-term cattle gain responses to stocking rate and grazing systems in northern mixed-grass prairie

The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (< 10 years) studies, and often stocking rates are confounded within grazing systems with higher stocking rates for short-duration rotational grazing systems compared to season-long grazing. A grazing system (season-long and short-duration rotational grazing) × stocking rate (light: 16 steers/80 ha, 18.0 animal unit days/ha; moderate: 4 steers/12 ha, 30.1 animal unit days/ha; and heavy: 4 steers/9 ha, 40.1 animal unit days/ha) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years (1991–2006) for yearling beef cattle gains. Average daily gains (kg/head/day) across all years with season-long grazing decreased with increasing stocking rate and grazing pressure. Heavy stocking rates reduced average daily gain by 16% and 12% compared to light and moderate stocking rates, respectively. In contrast to average daily gain, beef production (kg/ha) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April + May + June) precipitation. Grazing season gains (kg/head) and beef production both exhibited significant increasing hyperbolic relationships with spring precipitation, with the percentage of variation explained by spring precipitation substantially higher (62–83%) for beef production compared to grazing season gains (32–45%). The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment.