Cool Season Perennial Grasses as Complementary Forages to Winter Wheat Pasture

Three grazing trials with growing cattle were conducted to evaluate three cool season perennial grasses (Manska pubescent wheatgrass, Lincoln smooth bromegrass, and Paiute orchardgrass) as complementary forages for winter wheat pasture. Initial stocking rate averaged 1,359 kg BW/ha for approximately 60 d in the two spring trials (April and May) and 857 kg BW/ha for 40 d in the fall trial (late September and October). The ADG and gain per hectare averaged, respectively, 0.86 kg/d and 287 kg/ha and 0.50 kg/d and 59 kg/ha for the spring and fall trials. Generally, neither animal growth performance nor production per hectare was different among the three grasses. However, OM of wheatgrass was more digestible, and its CP was more ruminally degradable, than that of the other grasses. Crude protein concentrations of the grasses generally ranged from 13.6 to 32.4% of DM and were more than adequate to support BW gains of 1 kg/d for growing cattle. Grazing days per hectare and BW gain per hectare from the fall grazing period were only about 30 and 20%, respectively, of the totals for spring and fall 1999, which supports previous findings that most of the production of these grasses occurs in the spring. Orchardgrass was the least resistant to summer drought. Cattle must be removed from dual-purpose winter wheat at the first hollow stem stage of maturity in late winter. However, late winter forage production of these cool season perennial grasses was inadequate to serve as complementary forage to dual-purpose winter wheat.     

秋季补播多花黑麦草对扁穗牛鞭草草地产量、质量和植物组成的影响

本试验研究秋季补播多花黑麦草对扁穗牛鞭草草地产量、质量和植物组成的影响,为川西南丘陵山区及类似地区冬春季增加青绿饲料的供应提供最佳方案.结果表明,补播能显著增加产草量(P<0.05),补播时间显著影响牧草产量(P<0.05),早期补播(10月10日)牧草总产量达13 254.6 kg/hm2 DM,利用时间比其他补播时间提前2周.多花黑麦草补播量为22 kg/hm2时,牧草产量最高(13 080.7 kg/hm2 DM),粗蛋白产量比不补播处理增加750.9 kg/hm2 DM.补播改变了'广益'扁穗牛鞭草草地中的优势植物种类,在冬春季以多花黑麦草为主(占56%),并能有效抑制杂草.由此建议,在生产中采用22 kg/hm2的补播量,于10月10日前后播种,可提高'广益'扁穗牛鞭草草地全年牧草产量.     

Impact of forage diversity on forage productivity,nutritive value,beef cattle performance,and enteric methane emissions

Greenhouse gas emissions from the beef industry are largely attributed to the grazing sector, specifically from beef cattle enteric methane emissions. Therefore, the study objective was to examine how forage diversity impacts forage productivity, nutritive value, animal performance, and enteric methane emissions. This study occurred over three consecutive grazing seasons (2018 to 2020) and compared two common Midwest grazing mixtures: 1) a simple, 50:50 alfalfa:orchardgrass mixture (SIMP) and 2) a botanically diverse, cool-season species mixture (COMP). Fifty-six steers and heifers were adapted to an Automated Head Chamber System (AHCS) each year (C-Lock Inc., Rapid City, SD) and stratified into treatment groups based on acclimation visitation. Each treatment consisted of four pastures, three 3.2-ha and one 1.6-ha, with eight and four animals each, respectively. Forage production was measured biweekly in pre- and postgrazed paddocks, and forage nutritive value was analyzed using near-infrared reflectance spectroscopy. Shrunk body weights were taken monthly to determine animal performance. Forage availability did not differ between treatments (P = 0.69) but tended lower in 2018 (P = 0.06; 2.40 t dry matter ha⁻¹) than 2019 (2.92 t dry matter ha⁻¹) and 2020 (P = 0.10; 2.81 t dry matter ha⁻¹). Crude protein was significantly lower for COMP in 2018 compared with SIMP. Forage acid detergent fiber content was significantly lower for the COMP mixture (P = 0.02). The COMP treatment resulted higher dry matter digestibility (IVDMD48) in 2018 and 2019 compared with the SIMP treatment (P < 0.01). Animal performance did not differ between treatments (P > 0.50). There was a tendency for the COMP treatment to have lower enteric CH₄ production on a g d⁻¹ basis (P = 0.06), but no difference was observed on an emission intensity basis (g CH₄ kg⁻¹ gain; P = 0.56). These results would indicate that adoption of the complex forage mixture would not result in improved forage productivity, animal performance, or reduced emission intensity compared with the simple forage mixture.     

饲用小麦生产与利用研究现状及发展前景

随着生活水平的提高和食品消费结构的变化,对动物蛋白的需求迅速增长。然而,由于缺乏优质粗饲料,畜牧业的发展受到了很大的限制。饲用全株小麦产量高、营养品质好,已成为一种优质的饲料来源,因此,围绕饲用小麦的相关研究意义重大。梳理近年来国内外关于饲用小麦生产和利用的现状及发展趋势,重点概述的内容有:1)品种选育:种质创制技术、逆境分子育种和常规饲用小麦品种筛选;2)栽培管理:常规田间管理、放牧利用管理和粮饲兼用管理;3)青贮加工的影响因素:栽培管理、生育期、添加剂和其他因素;4)家畜的饲喂效果:采食量、消化率、畜产品产量和品质等。此外,总结了饲用小麦各研究领域中所存在的问题和不足。同时,对新形势下饲用小麦的研究趋势和研究重点进行了展望,以期对我国饲用小麦的生产和推广利用提供指导与参考。目前,饲用小麦的发展背景主要是粮食过剩、饲草供需矛盾和动物生产性能等问题,它在产量和营养方面表现优异,尤其在冬季饲料缺乏时,小麦具备更大的生长优势,无论是放牧还是青贮利用都较方便,这也缓解了目前的饲料危机,为畜牧业的安全发展提供了保障。但是,粮用小麦品种一般为矮秆,其全株产量受限,为更好地发挥小麦的饲用价值,培育饲用专用品种势在必行。     

Growth performance of stocker calves backgrounded on sod-seeded winter annuals or hay and grain

Economically viable options for retaining ownership of spring-born calves through a winter backgrounding program are somewhat limited in the southeastern United States. Although sod-seeded winter annual forages produce less forage than those same forages planted using conventional tillage practices, sod-seeded winter annual forages have the potential to provide a low-cost, rapid-gain, ecologically and economically viable option for retaining ownership of fall-weaned calves. A study was conducted during the winters of 1998, 1999, and 2000 using 180 crossbred calves (261 +/- 2.8 kg initial BW; n = 60 each year) to compare sod-seeded winter annual forages with conventional hay and supplement backgrounding programs in southeast Arkansas. Calves were provided bermudagrass hay (ad libitum) and a grain sorghum-based supplement (2.7 kg/d) on 1-ha dormant bermudagrass pastures or were grazed on 2-ha pastures of bermudagrass/dallisgrass overseeded with 1) annual ryegrass, 2) wheat plus annual ryegrass, or 3) rye plus annual ryegrass at a set stocking rate of 2.5 calves/ha. Calves grazed from mid-December until mid-April but were fed bermudagrass hay during times of low forage mass. Mean CP and IVDMD concentrations were 19.0 and 71.1%, respectively, across sampling dates and winter annual forages, but three-way interactions among forage treatments, year, and sampling date were detected (P < 0.01) for forage mass, concentrations of CP, and IVDMD. The IVDMD of rye plus ryegrass was greater (P < 0.05) than that of ryegrass in yr 2. A forage treatment x sampling date interaction was detected for forage CP in yr 1 (P < 0.05) and 2 (P = 0.05) but not in yr 3 (P = 0.40). Forage mass did not differ (P > or = 0.22) among winter annual treatments on any sampling date. During the first 2 yr, calves fed hay plus supplement gained less (P < 0.05) BW than calves that grazed winter annual forages; gains did not differ (P > or = 0.23) among winter annual treatments. During the 3rd yr, undesirable environmental conditions limited growth of the winter annual forages; total gain did not differ (P = 0.66) among the four treatments. Winter annual forages offer potential to provide high-quality forage for calves retained until spring, but consistent forage production and quality are a concern when sod-seeding techniques are used.     

Effects of establishment method and fall stocking rate of wheat pasture on forage mass, forage chemical composition, and performance of growing steers

Stocking rate is a fundamental variable for managing pastures, and there is a distinct relationship between stocking rate and animal performance for each forage type. This research was conducted to determine the effects of fall stocking rate (SR) and method of establishment of wheat pasture planted into dedicated crop fields on animal performance during the fall and subsequent spring. There was a factorial arrangement of tillage methods used in the establishment of wheat pasture and fall stocking rates. Tillage treatments included 1) CT, seed sown into a prepared seedbed, 2) RT, a single pass with a light disk followed by broadcasting of seed, or 3) NT, direct seeding into the undisturbed stubble of the grazed-out wheat pasture from the previous year. The fixed SR during the fall were 1.9, 2.5, and 3.7 growing beef steers (Bos taurus L.)/ha. In the spring all pastures were grazed at the same fixed SR by steers for graze out. Data were analyzed using the mixed procedure of SAS as a randomized complete block design with field as the experimental unit and year as the block. Forage mass, forage nutritive composition, and animal performance during the fall or spring were not affected (P ≥ 0.14) by tillage method. During the fall grazing season, with increasing SR there were linear (P < 0.01) decreases in BW of steers upon removal from pasture, BW gain per steer, and ADG, whereas grazing-day per hectare and BW gain per hectare increased linearly (P < 0.01) with increasing SR. The carryover effects of fall SR into the spring grazing season decreased (P< 0.01) grazing-day per hectare and tended (P ≤ 0.09) to produce quadratic changes in BW upon removal from pasture and BW gain per hectare. Across the fall and spring grazing seasons, grazing-day per hectare increased linearly (P < 0.01) with greater SR, and BW gain per hectare increased quadratically (P = 0.02) with increased fall SR. A tillage treatment by fall SR interaction (P = 0.10) indicates that although there was no difference (P ≥ 0.12) due to tillage treatment in BW gain per hectare at 1.9 or 2.5 SR, NT fields produced (P ≤ 0.04) more BW gain per hectare than CT or RT at the 3.7 SR. Although increasing SR of growing steers leads to reduced animal performance in the fall and reduced carrying capacity in the spring, NT appears to be capable of withstanding greater fall SR with less impact on total production per hectare than CT or RT.     

Integrating Ranch Forage Production,Cattle Performance,and Economics in Ranch Management Systems for Southern Florida

The presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha·cow^-1 on summer pastures and 0.93, 1.62, and 2.16 ha·cow^-1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility. Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant (P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves·ha^-1) was increased (P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch's fixed cost structure.     

The effect of strategic anthelmintic treatment on the breeding performance of hill ewes

A series of field trials involving 3500 Scottish hill ewes was carried out to determine the effect of different worming routines on subsequent flock performance. Combinations of the following seasonal dosings were examined in April lambing flocks: “early winter” (November/early December); “winter” (mid-January to early February) and “spring” (mid-March to early April). The effects upon numbers of barren ewes and on rearing percentages in comparison with untreated control sheep were evaluated.Barrenness was significantly reduced by the following treatments: “early winter” by 70% (P<0.10); “winter” by 7.8% (P<0.05); “early winter and winter” by 4.3% (P<0.05). Rearing percentages were significantly increased by the following treatments: “early winter and winter” by 10.7% (P<0.01); “early winter and spring” by 9.2% (P<0.01); “spring” by 7.9% (P<0.05).The increased rearing percentages indicated that a strategic dosing programme for breeding ewes between mating and parturition is worthwhile, with the routines involving two doses — either ”early winter and winter” and “early winter and spring” giving the greatest benefit.Attention is drawn to the high incidence of barrenness and low rearing percentages which was a constant feature in all the flocks used in the trial.     

Performance of Nellore heifers, forage mass, and structural and nutritional characteristics of Brachiaria brizantha grass in integrated production systems

Our objective was to evaluate production, nutritive value and carrying capacity of piatã grass (Brachiaria brizantha cv. BRS Piatã), and performance of Nellore heifers in agrosilvopastoral systems (ASPS) with three eucalyptus (Eucalyptus urograndis) tree densities, during winter, spring, summer, and fall. Three integrated systems were evaluated: ASPS-1 (357 trees ha^?1), ASPS-2 (227 trees ha^?1), and CON (5 trees ha^?1). In each system, two sward heights were evaluated: short and tall. A total of 80 11-month-old Nellore heifers were randomly allocated in a randomized split-plot block, 3?×?2 factorial. Greater dry matter availability was observed on CON pastures during the fall season. Greater percentage of leaf lamina was detected on ASPS-1 with short sward height and greater during summer, compared with other seasons. A greater forage production was observed between tree rows and for tall sward height. Spring was the season with less forage nutritive value. Average daily gain was greater during summer and fall. Gain per hectare and stocking rate were greater on CON system and on ASPS-2. Pastures with short sward height had greater gain per hectare and stocking rate. Agrosilvopastoral systems with intermediate tree density seem to be a good choice for producers willing to diversify their revenue sources without decreasing animal production.     

Intake and digestion of wheat forage by stocker calves and lambs

Because wheat forage contains high concentrations of N, NPN, digestible DM, and water, beef cattle and sheep require an adaptation period before positive BW are seen. The objective of the present experiment was to determine the impact of length of exposure of lambs and steers to wheat forage on BW gains, N retention, and forage digestibility. Sixteen steer calves (average BW = 210 +/- 12 kg) and 20 wether lambs (average BW = 31.5 +/- 2.0 kg) were randomly assigned to 1 of 2 treatment groups. Group 1 grazed a wheat pasture for 120 d during the winter, whereas group 2 was wintered on dormant warm-season grass pastures plus warm-season grass hay and plant-based protein supplements. In the spring (April 5), all lambs and steers grazed wheat pasture for 14 d and were then housed in metabolism stalls and fed freshly harvested wheat forage to determine forage digestibility and N metabolism. Data were analyzed for lambs and steers separately as a completely randomized design, using the individual animal as the experimental unit. Lambs and steers grazing wheat pasture for the first time in the spring had less ADG during the first 14 d than lambs (80 vs. 270 g, respectively; P = 0.01) and steers (1.06 vs. 1.83 kg, respectively; P = 0.09) that had grazed wheat pastures all winter. Digestibility of DM, NDF, and ADF fractions and N metabolism of freshly harvested wheat forage by lambs and steers were not different (P > 0.10) between the 2 treatment groups. Less ADG during the first 14 d of wheat pasture grazing is most likely the result of less DMI by nonadapted animals and is not due to diet digestibility or N metabolism.     

Summer and Winter Defoliation Impacts on Mixed-Grass Rangeland

Combined growing- and dormant-season pasture use has potential to increase herbage harvest without causing the undesirable shift in species composition that occurs with excessive utilization. The objective of this study was to determine the effect of summer clipping on winter pastures and winter clipping on summer pastures regarding standing crop, plant community composition, and forage quality. The study was conducted from 2003–2006 at the Antelope and Cottonwood Research Stations located in the mixed-grass prairie of western South Dakota. At each location, the experimental design was a randomized complete block with three replications that included 18 clipping treatments arranged as a split-split plot. Whole plots consisted of four summer clipping dates (May–August). Subplot treatments were two clipping intensities (clipped to residual height to achieve 25% or 50% utilization). Sub-subplots consisted of two winter clipping intensities (unharvested or clipped to a residual height to achieve a total utilization of 65%). Two winter control treatments were arranged in the subplot and split into two clipping intensities of 50% and 65% utilization. Winter biomass for the May 25% clipping treatment was similar to winter biomass for winter-only clipping. No increase in forage quality resulted from summer clipping compared with winter clipping. Three consecutive yr of combined growing-season and dormant-season defoliation to 65% utilization resulted in no change in functional group composition compared with ≤ 50% utilization treatments. Clipping in June resulted in reduced midgrass biomass at both stations and increased shortgrass biomass at Cottonwood. Results suggest that producers could combine growing and dormant-season grazing to increase the harvest of herbage on mixed-grass prairie, but should change season of use periodically to avoid an undesirable shift in plant composition.     

冬油菜茬复种饲用玉米效果研究

[目的]开展冬油菜茬复种饲用玉米生产潜力研究,为探索饲草料新型高效生产模式奠定理论基础。[方法]在平凉市选有代表性的东部旱塬地,开展冬油菜茬复种饲用玉米与普通春播玉米试验研究,分析各自生产潜力及效果。[结果]复种方式下全株玉米秸秆产量显著低于春播方式(P<0.05),生产成本明显低于春播方式。[结论]冬油菜茬复种玉米可降低全株玉米秸秆生产成本,提高养殖经济效益,在平凉市规模化养殖场有一定的推广价值。     

不同粮食和牧草前作对水稻生长、产量和品质的影响

为了探讨长江流域农区冬季种植牧草和粮食作物对后作水稻Oryza sativa生产的影响,对种植多花黑麦草Lolium multiflorum、黑麦Secale cereal和小麦Triticum eastivum的水田土壤理化性状以及水稻的生长发育、稻谷产量和稻米品质进行了研究.结果表明:冬季种植多花黑麦草和黑麦后土壤理化性状得到了改善,降低了土壤pH值,增加了土壤全氮含量和速效养分.种植小麦的土壤pH值降低,全氮含量增加,但速效养分增加较少或减少.相应地,多花黑麦草茬和黑麦茬水稻生长得到了明显的促进,单位面积有效穗数和产量显著高于小麦茬水稻,但对每穗粒数、千粒重和稻米品质的影响不大.可见,冬季种植牧草在生产大量青饲料的同时,还起到了改良土壤的作用,为提高农田生产力提供了有效途径.同时促进了农业种植业和畜牧业的有机结合,形成了包括土壤、粮食作物、牧草、家畜等多因子的生态农业系统.     

陕西省关中地区饲草型小麦种质资源筛选与评价

为筛选出能够在中国北方冬季提供鲜绿饲草的小麦种质,在大田条件下,以饲草产量、再生饲草产量、小麦分蘖数和抗逆性指标为基础,对适宜于陕西关中地区栽培的200份小麦种质材料的饲草特性进行了评价。筛选出ZM32、ZM132、ZM27、ZH895、ZH175、ZM33、XY58和XN928共8个具有较高饲草产量和再生能力的小麦材料,同时其可溶性蛋白含量和抗氧化酶活性等生理指标表现突出,可以作为饲草型小麦种质使用。此外,小麦刈割生物量和再生生物量与小麦冬季分蘖和春季分蘖数均极显著正相关,表明小麦冬前分蘖数和春季分蘖能力对饲草型小麦种质的筛选具有重要意义。而较高的可溶性蛋白含量、SOD和POD活性可以保证饲草型小麦安全越冬和春季补偿性生长,可作为饲草型小麦筛选的参考指标。     

冬季妊娠母猪饲养管理措施

母猪妊娠阶段的饲养管理十分重要,尤其是在冬春季节,由于日照时间少,外界气候寒冷,温度忽高忽低,如果没有做好妊娠母猪的饲养管理工作,会对母猪造成应激刺激,影响其机体的抵抗能力,易感染多种疾病。冬季妊娠母猪在饲养管理、疾病防控等方面有特殊要求,需要充分掌握母猪在妊娠阶段的具体生理特征,做到科学养殖、科学管理,避免因为冬春季节养殖管理不当造成妊娠母猪繁殖能力下降,初生仔猪体重较小。为提高母猪的生产性能,增加养殖场效益。该文主要论述冬季妊娠母猪的饲养管理。     

江淮地区冬闲田豆禾牧草混播生产模式的发展前景

随着动物性食品需求的快速增长和“粮改饲”政策的实施,推进农区产业结构调整和草食畜牧业全面发展势在必行,江淮地区作为我国南方重要的粮食生产基地和畜牧业发展基地,可充分利用其冬闲田的生产潜力,推行粮草兼顾型种植模式,探索出适合当地冬季种植的牧草生产模式。江淮地区冬闲田种草现多以黑麦草(Lolium perenne)、紫云英(Astragalus sinicus)等单播为主,多花黑麦草+紫云英(Astragalus sinicus)/白三叶(Trifolium repens)/光叶紫花苕(Vicia villosa)、燕麦(Avena sativa)+毛叶苕子(Vicia villosa)/金花菜(Medicago hispida)等冬闲田豆禾混播生产模式可以克服禾本科单播施肥较多、土地翻耕难、豆科单播产量较低和营养不全面等方面问题,能够更加有效地提高生产力,增强土地持久力,对于增加农民收入,推进江淮地区草食畜牧业发展,促进南方农业生态转型有着积极作用。本研究分析了江淮地区饲草种植的发展前景和现状,阐述了在江淮地区施行豆禾牧草混播生产模式的优势,并探讨了优质豆禾牧草混播模式及其生态经济效益,以期为江淮地区及类似地区的冬闲田牧草种植提供参考。     

Effects of Forage Management on Pasture Productivity and Phosphorus Content

The objectives of the current study were to determine the amounts of above- and below-ground plant biomass production, P uptake by forage, and P concentration of cool-season grass forage as influenced by management and season. Five forage management treatments were evaluated over 3 years in smooth bromegrass (Bromus inermis Leyss) pastures. Management practices were: ungrazed (U), hay harvest/fall stockpile grazing (HS), rotational stocking to residual sward heights of 10 (10R) or 5 (5R) cm, and continuous stocking to maintain sward height at 5 cm (5C). Forage samples were hand-clipped within and outside grazing exclosures monthly from April through November of each year and analyzed for mass and P concentration. Root samples were collected at the initiation and completion of the study for determination of root length density (RLD) and root surface area density (RSAD). Phosphorus concentrations of forage outside the grazing exclosures did not differ among 5C, 5R, and 10R treatments, which were greater than U paddocks in April and August and less than HS paddocks in June. Mean annual forage productivity was greater in HS, 10R, 5R, and 5C paddocks (6 744 ± 62 kg · ha^-1 mean ± SE) than in the U paddocks (1 872 ± 255 kg · ha^-1). Mean P concentration of forage outside exclosures was greatest during the spring (0.21 ± 0.01%), and lowest during the fall (0.13 ± 0.01%). Mean annual P uptake by forage followed the same trend as forage production, being greater in the HS, 10R, 5R, and 5C paddocks (13.9 ±  kg · ha^-1) than in the U paddocks (3.7 ±  kg · ha^-1). After 3 years, RLD decreased in the ungrazed paddocks, but was unchanged in the HS, 10R, 5R, and 5C paddocks. Forage production and P uptake by forage is stimulated by forage harvest, either by grazing or hay harvest in smooth bromegrass pastures.     

饲用小麦种植和利用的试验研究

本研究筛选小麦品种在南方冬闲田进行饲用种植和利用试验。结果表明在饲用小麦适应性好、产量较高,条播行距25 cm、播种量10 kg/667 m²时,其鲜草产量可达4 780 kg/667 m²,干草产量为1 070 kg/667 m²、全株收货时干物质29.85%。在南方冬闲田合理种植小麦,具有较好的生长优势,可获得较高生物学产量,适宜进行刈割鲜饲或青贮加工利用。本文可为本区域及相似地区的饲用小麦生产提供参考依据,缓解冬季饲草严重缺乏等实际生产问题。     

甘南州夏河县牧区冬春饲草储备与抗灾运营模式

 
雪灾是制约高寒牧区畜牧业可持续发展的主要灾害。高寒牧区由于冬春枯草期漫长,可利用饲草短缺,一旦遇有雪灾会对当地畜牧业发展产生致命打击。如何探索可利用饲草资源作为牧区冬春饲草储备,以预防、抵抗雪灾或用作冬春补饲是解决高寒牧区畜牧业发展的瓶颈问题。论文以夏河县某公司经营模式为例,介绍了甘南藏族自治州夏河县采取农牧交错区公司经营的模式种植优质饲草,并通过政府与公司签署订单收购牧草的模式,留够牧区抗灾、防灾饲草数量,从而有效预防和减轻了牧区雪灾的危害。     

Growth and reproductive performance of beef heifers grazing endophyte-free, endophyte-infected and novel endophyte-infected tall fescue

A three-year study was conducted to investigate the effects of endophyte-free (E−), endophyte-infected (E+) and novel endophyte-infected (EN) tall fescue on the growth and pregnancy rate of beef heifers during the spring. Each year, 48 beef heifers were strip-grazed on stockpiled fescue from December through February, fed fescue hay during late February to early April and then rotationally grazed on spring growth of fescue until June. At the end of the trial, heifers had been maintained on E+, E− or EN (pasture or hay) for a total of 152, 188 and 191 d in years 1, 2, and 3, respectively. In late March, heifers were synchronized using a controlled intravaginal drug-releasing device, (CIDR®) for 7 d followed by injection with PGF2α (Lutalyse®). Heatmount detectors (Kamar®) and observation for behavioral estrus were used to detect estrus for 63 d. Heifers were artificially inseminated 8 to12 h after the onset of standing estrus. Conception was determined by transrectal ultrasonography at approximately 30, 60 and 90 d after synchronization. Reproductive performance did not differ among treatments (P ≥ 0.20). Pregnancy rate was 54, 65, and 65% for E+, E− and EN, respectively. However, during the spring, growth and prolactin were decreased (P < 0.01) for heifers on E+. Gains on spring pasture were 0.24, 0.75, and 0.71 kg/d (SEM ± 0.03) for E+, E− and EN, respectively. Based on these results, the wild type endophyte-infected fescue can be used in production systems as a source of winter forage but producers should consider placing heifers on alternative forage (such as the novel endophyte-infected fescue) in the spring.