呼伦贝尔羔羊及呼杜杂交一代羔羊的肌肉与脂肪组织胆固醇含量比较研究

试验旨在比较研究呼伦贝尔羔羊(HL)及呼杜杂交一代羔羊(HZ)的肌肉与脂肪组织的胆固醇含量。采用2×2完全随机试验设计,选择4月龄断奶HL和HZ羔羊各60只,共120只,分为4组,每组30只。因素1为育肥方式,分为NG与GS;因素2为品种,分为HL和HZ。育肥期均为60 d,分为育肥前期和育肥后期两个阶段。试验结束时,放牧补饲组和自然放牧组中选择接近平均体重的5只羔羊(禁食24 h、禁水2 h)进行屠宰试验。结果表明:品种显著影响肌肉与脂肪组织的胆固醇含量,HZ羔羊的臂三头肌与股二头肌的胆固醇含量显著或趋于显著地高于HL羔羊(P=0.02、P=0.063),大网膜脂、肾周脂肪、尾脂、肠系膜脂与背脂的胆固醇含量显著或趋于显著低于HL羔羊(P0.05,0.05P0.10)。与NG相比,GS显著增加了羔羊背最长肌和股二头肌胆固醇的含量(P0.05),显著降低了大网膜脂、肾周脂肪、肠系膜脂及背脂的胆固醇含量(P0.05)。不同部位的肌肉与脂肪组织其胆固醇的变化规律不完全相同,呼伦贝尔羔羊与呼杜杂交一代羔羊的肌肉与脂肪组织的胆固醇含量存在组织部位的差异。呼杜杂交一代羔羊的臂三头肌与股二头肌的胆固醇含量显著或趋于显著地高于呼伦贝尔羔羊,但大网膜脂、肾周脂肪、尾脂、肠系膜脂与背脂的胆固醇含量显著或趋于显著地低于呼伦贝尔羔羊。     

自然放牧与放牧补饲育肥对肉羊血浆和肌肉中氨基酸组成的影响

本试验研究了呼伦贝尔羊(HL)和呼伦贝尔羊与杜泊羊杂交1代(HZ)羔羊在自然放牧(NG)与放牧补饲(GS)2种不同育肥方式下,其血浆和肌肉组织(背最长肌、臂三头肌、股二头肌)中氨基酸(AA)组成的变化。采用2×2完全随机试验设计,选择体重、体况接近的健康4月龄断奶HL和HZ公羔各60只。因素1为育肥方式,分为NG与GS;因素2为品种,分为HL与HZ。共分为4组,每组30只。进行为期60 d的育肥。结果表明:1)NG组血浆中必需氨基酸(EAA)、限制性氨基酸(LAA)、功能性氨基酸(FAA)和总氨基酸(TAA)含量显著低于GS组(P0.05),呈味氨基酸(DAA)含量有低于GS组趋势(0.05≤P0.10)。2)与GS组相比,NG组背最长肌中粗蛋白质(CP)、LAA含量显著升高(P0.05)。3)与GS组相比,NG组臂三头肌中LAA和DAA含量显著降低(P0.05),EAA含量均有降低的趋势(0.05≤P0.10)。4)NG组股二头肌中CP、EAA、NEAA、TAA、LAA、BCAA、DAA含量显著低于GS组(P0.05)。5)与HL组相比,HZ组血浆EAA,背最长肌LAA,臂三头肌BCAA和股二头肌EAA含量显著(P0.05)或有显著趋势升高(P0.10)。由此可见,GS羔羊肉蛋白质营养价值优于NG,HZ羔羊肉蛋白质营养价值优于HL羔羊。     

不同饲养模式对阿尔巴斯白绒山羊羔羊育肥增重及屠宰性能的影响

试验主要研究了不同饲养模式对阿尔巴斯白绒山羊羔羊育肥增重及屠宰性能的影响。从内蒙古白绒山羊种羊场的4月龄断奶羔羊中选择日龄为(130±10)d的母羔和去势公羔(羯羔)各30只作为放牧补饲组,从淘汰群中选择与放牧补饲组日龄相近的母羔和去势公羔(羯羊)各30只作为舍饲组进行舍饲育肥,共120只,分为4组,每组30只。采用2×2完全随机试验设计,第一因素为饲养模式,设放牧补饲和舍饲育肥两种,其中,放牧补饲的羔羊按照原厂方式,每天在天然草场上放牧并每只补饲玉米(风干基础)300 g,舍饲育肥的羔羊,按照试验设计饲喂全混合日粮;第二因素为性别,分为母羔与羯羔,育肥期3个月。育肥结束时,采用单因子完全随机试验设计,分别从舍饲育肥和放牧补饲的羯羔组中每组选择接近平均体重的6只羯羔屠宰,研究不同饲养方式对羯羔屠宰性能的影响。结果表明,与放牧补饲相比,舍饲模式的育肥体重和增重显著增加,育肥期内舍饲组的日增重较放牧补饲组提高69%,饲料转化效率是放牧补饲组的2倍。屠宰试验结果表明,舍饲模式的胴体重、屠宰率、净肉率显著提高,分别较放牧补饲组增加64.60%、27.56%、37.39%。因此,阿尔巴斯白绒山羊羔羊进行短期舍饲育肥与放牧补饲相比,对增重性能、饲料转化效率和屠宰性能的促进效果明显,可显著提高产肉量。     

舍饲与放牧育肥对绒山羊成年母羊育肥和屠宰性能的影响

试验主要研究了放牧育肥与舍饲育肥两种饲养模式对绒山羊育肥性能、营养物质表观消化率及屠宰性能的影响。从内蒙古白绒山羊种羊场淘汰母羊中选择平均体重为(40.38±0.84)kg的5岁阿尔巴斯白绒山羊60只随机分为对照组和试验组,对照组进行放牧育肥,试验组进行舍饲育肥,饲喂全混合日粮。育肥期为60 d。在育肥试验开始20 d和试验结束时,分别从试验组和对照组中选择6只羊进行消化试验,采用内源指示剂法测定营养物质的消化率。在育肥试验结束时,分别从对照组和试验组中随机选取6只羊进行屠宰,测定屠宰性能指标。结果表明,与放牧育肥相比,舍饲育肥可显著增加绒山羊成年母羊的全期日增重、干物质采食量(DMI)与饲料转化效率(P<0.05),分别较放牧育肥组增加了1.02%、137.50%与107.58%;显著增加母羊对日粮总能(GE)、消化能(DM)、粗蛋白(CP)、钙(Ca)和磷(P)等营养物质表观消化率(P<0.05);但显著降低了中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的消化率(P<0.05)。舍饲育肥组的胴体重、屠宰率、净肉重、净肉率和眼肌面积均显著高于放牧育肥组(P<0.05),分别较放牧育肥组提高了55.57%、25.89%、67.97%、35.64%和46.18%。舍饲育肥母羊的内脏总重、胃重、肠总重与皮重显著高于放牧育肥组(P<0.05),但所占体重的比例均显著低于放牧育肥母羊(P<0.05)。按照代谢体重表示,舍饲育肥母羊的营养物质进食量DE为1.18~1.25 MJ/(W0.75·kg)、CP为12.37~16.29 g/(W0.75·kg)、Ca为0.43~0.63 g/(W0.75·kg)、P为0.17~0.25 g/(W0.75·kg)时,绒山羊成年母羊具有较好的育肥性能与屠宰性能,经济效益显著。     

不同育肥方式对呼伦贝尔羔羊育肥性能及屠宰性能的影响

试验主要研究不同育肥方式对内蒙古自治区呼伦贝尔市羔羊育肥性能和屠宰性能的影响,研究结果为呼伦贝尔羊科学育肥方案的制定提供理论依据。选择120只(公母各半)4月龄断奶后羔羊做为试验动物,采用二因素完全随机试验设计,第1因素为育肥方式,分为自然放牧和放牧补饲2种方式;第2因素为羔羊性别,分为公羔和母羔2种,共分为4组。研究不同育肥方式和性别对呼伦贝尔羔羊育肥性能的影响。试验结束时,分别从放牧补饲组和自然放牧组中选择接近平均体质量的5只公羔羊进行屠宰试验,研究不同育肥方式对公羔羊屠宰性能的影响。结果表明,与自然放牧相比,放牧补饲羔羊的育肥体质量和日增质量显著增加(P0.05),羔羊出栏体质量达到39.37 kg,在整个育肥期较自然放牧羔羊日增质量增加38.46%。屠宰试验结果表明,放牧补饲公羔羊胴体质量、屠宰率、净肉质量、净肉率和大网膜脂肪质量均显著高于自然放牧羔羊(P0.05),分别提高34.43%、13.76%、40.55%、19.21%和87.50%,屠宰率和净肉率分别达到54.47%和45.67%。与自然放牧相比,对断奶羔羊放牧补饲可显著增加育肥性能和屠宰性能,产肉量显著增加(P0.05)。在呼伦贝尔地区对断奶羔羊补饲是一种有效的育肥方式。     

库鲁斯台草原羔羊育肥及屠宰性能测定

选用 6月龄的当地新疆细毛羊羔羊和当地新疆细毛羊与南非肉用细毛羊杂交一代羔羊各 40只 ,分成两组 ,研究不同育肥方式对两组羔羊生长性能的影响。结果表明 ,在放牧条件下 ,对断奶羔羊适当补饲适量精料能极显著地提高日增重(P <0 0 1)。试验结束后 ,选取 9月龄羔羊进行屠宰试验 ,比较不同育肥方式对羊胴体品质的影响。结果表明 :补饲能极显著地提高胴体重 (P <0 0 1) ,同时屠宰率、净肉率和眼肌面积等指标也得到不同程度的改善。并且杂交一代羊在育肥和屠宰性能等方面都优于当地羊。     

育肥方式对呼伦贝尔羊及其与杜泊羊杂交1代羔羊消化道酶活性的影响

本试验旨在研究育肥方式对呼伦贝尔羔羊及呼伦贝尔羊与杜泊羊杂交1代羔羊小肠及胰腺酶活性的影响。采用2×2完全随机试验设计,第1因素为育肥方式,分自然放牧和放牧补饲;第2因素为品种,分呼伦贝尔羔羊及呼伦贝尔羊与杜泊羊杂交1代羔羊(由呼伦贝尔母羊与杜泊公羊杂交而来)。选择体重相近的健康4月龄断奶呼伦贝尔羔羊和呼伦贝尔羊与杜泊羊杂交1代羔羊各60只,各分为2组,每组30只。育肥阶段分为育肥前期、育肥后期2个阶段,共60 d。放牧补饲组羔羊每只每天补饲精料在育肥前期为0.27 kg,育肥后期为0.53 kg。育肥试验结束时,分别从每组羔羊中随机选取5只羔羊进行屠宰,取小肠及胰腺组织测定酶活性。结果表明:与自然放牧相比,放牧补饲可显著提高羔羊十二指肠的胰蛋白酶、脂肪酶及糜蛋白酶活性,空肠、回肠与胰腺的淀粉酶、脂肪酶及胰蛋白酶活性(P0.05)。与呼伦贝尔羔羊相比,呼伦贝尔羊与杜泊羊杂交1代羔羊的十二指肠淀粉酶、糜蛋白酶活性,空肠及回肠的脂肪酶和胰蛋白酶活性显著增加(P0.05);十二指肠胰蛋白酶、胰腺脂肪酶活性的增加趋于显著(0.05≤P0.10)。总之,与自然放牧相比,放牧补饲能够提高羔羊的小肠及胰腺的消化酶活性,呼伦贝尔羊与杜泊羊杂交1代羔羊的小肠及胰腺的消化酶活性高于呼伦贝尔羔羊。     

内蒙古阿尔巴斯白绒山羊羔羊短期育肥效果与屠宰性能分析

[目的]研究内蒙古阿尔巴斯白绒山羊羔羊短期育肥效果,并评价育肥羊的屠宰性能。[方法]选择体重相近的4月龄断奶羔羊520只,选取260只作为试验组,采取全舍饲的饲养模式,分别在3个牧户家饲养,饲养管理标准与饲料保持一致;选取260只作为对照组,采取传统放牧饲养模式,选择草场质量相近的2个牧户家饲养。育肥期为4个月。测定、计算并比较不同饲养模式下阿尔巴斯白绒山羊在不同育肥阶段的体重以及平均日增重;育肥结束后进行屠宰试验,测定并比较不同饲养模式下阿尔巴斯白绒山羊的屠宰性能指标;计算不同饲养模式下阿尔巴斯白绒山羊的养殖经济效益。[结果]与对照组相比,试验组在育肥120 d的体重显著（P<0.05）高于对照组;试验组在育肥30~60 d、60~90 d的平均日增重显著（P<0.05）高于对照组,在育肥90~120 d的平均日增重极显著（P<0.01）高于对照组。试验组宰前活重、胴体重、屠宰率、净肉重、净肉率、骨骼重、肾脏及肾脂重量、眼肌面积均极显著（P<0.01）高于对照组,骨肉比极显著（P<0.01）低于对照组;在非胴体组成部分重量方面,试验组血重、头蹄重、皮重、消化系统重（胃、肠）、内脏重（心、肝、肺）、大网膜脂肪及肠系膜脂肪重均极显著（P<0.01）高于对照组。试验组育肥纯利润较对照组增加345.60元/只。[结论]阿尔巴斯白绒山羊舍饲育肥与传统放牧模式相比,育肥增重效果和屠宰性能显著提高,取得了良好的经济效益,适合在鄂尔多斯市推广。     

放牧强度和草地类型对育肥羔羊生产性能的影响

在华北农牧交错带坝上地区 ,研究放牧强度和草地类型对肥育羔羊生产性能的影响。结果表明 ,在育肥期间 ,放牧强度对育肥羔羊个体增重的影响主要与季节有关。试验结束时 ,供试羔羊体重间差异不显著 (P>0 .0 5) ,但是单位面积家畜生产性能之间差异极显著 (P<0 .0 1 ) ,其中以重牧区畜产品产量最高 ,达 1 92 .53kg/hm2× 1 0 8d,中牧和轻牧区分别为 1 81 .6和 1 1 0 .9kg/hm2 × 1 0 8d。杂花苜蓿—扁穗冰草—新麦草草地对羔羊育肥增重效果最为显著 (P<0 .0 5)。放牧强度和草地类型互作对羔羊的增重差异极显著 (P<0 .0 1 )。不同草地类型适宜的放牧强度各异。羔羊干物质和蛋白质日采食量均随着放牧强度的增加而降低     

柴达木地区羔羊暖季放牧育肥效果研究

在柴达木盆地的暖季,经151d的放牧育肥,半细毛羔羊平均体重增长12.42kg,日增重为82.25g;藏系羔羊同期121d的放牧育肥,平均体重增长10.65kg,日增重为88.02g;用地产的饲草料进行舍饲育肥,半细毛羔羊日增重为89.76g,藏系羔羊为85.46g;放牧与舍饲育肥的增重效果差异极不显著(p>0.01)。     

Growth performance of yearling horses grazing bermudagrass pastures at different grazing pressures

Body weight gains and height at the withers were measured in yearling geldings grazing bermudagrass (Cynodon dactylon [L.] Pers.) pastures with neither energy nor protein feed supplementation at stocking rates of 6.7, 8.0, 9.5 and 12.4 yearlings per hectare. Weekly forage samples were taken to estimate the quantity and quality of available forage. These samples were clipped and separated into three equal lengths to characterize upper, middle and lower thirds of the canopy and to determine relationships between available forage and yearling growth rate. Average daily gain was influenced by stocking rate, but gain in height was not affected by stocking rate. Average daily gain ranged from -.31 to .37 kg/d and was negatively related to stocking rate. A quadratic relationship between available forage and ADG was detected. However, a linear relationship between ADG and available forage in top layers of the canopy indicated that animal performance might have been limited by availability of top layer forage in pastures subjected to light grazing pressure.     

Timing of herbage allocation in strip grazing: Effects on grazing pattern and performance of beef heifers

The timing of grazing bouts (GB) determines how cattle allot time to meet their nutritional needs. Net photosynthesis and evapotranspirational losses increase herbage nonstructural carbohydrate and DM concentrations, which may lead to longer and more intense GB at dusk. Hence, linking the grazing pattern, plant phenology, and herbage allocation time emerges as an option to manipulate the GB and nutrient intake. The objectives of this work were to analyze grazing behavior and performance of beef heifers when herbage allocation was at 0700 each morning (MHA) or at 1500 each afternoon (AHA). Two pairs of experiments were conducted during the winter and spring examining behavior and performance. Measurements were grazing, rumination, and idling times during daylight hours, and their patterns, as well as bite rate, ADG, change in BCS, and daily herbage DMI. In the behavioral experiments, 8 heifers strip-grazed annual ryegrass (Lolium multiflorum Lam.). The grazing, rumination, and idling times as well as bite rate were measured and also analyzed per time of day. In the performance experiments, 48 beef heifers strip-grazed annual ryegrass in 2 groups according to treatments. Daily DMI, ADG, and changes in BCS were analyzed. The AHA increased daily idling time (P < 0.01) and decreased grazing time (P < 0.01). The AHA concentrated grazing time in the evening, when bite rate was greater (P < 0.01). The daylight rumination time varied by time of day (P < 0.01), but total daylight rumination time did not differ (P = 0.11). With AHA, rumination time and idling time were concentrated in the morning and afternoon. In the performance experiment during the winter, there was a treatment x week effect (P < 0.01) for ADG and change in BCS. Beginning in wk 4, heifers in AHA gained 150 g of BW and 0.0145 points of BCS more than those in MHA (P < 0.05) per day. In the spring, AHA increased ADG by 549 g and 0.0145 points of BCS more than those in MHA (P < 0.05) per day during the entire 6 wk. The herbage DMI (kg/d) did not differ in winter (AHA, 5.0 vs. MHA, 4.5) or spring (AHA, 5.6 vs. MHA, 5.0). These results suggest that timing of herbage allocation alters grazing, rumination, and idling patterns; AHA leads to longer and more intense GB when herbage has greater quality, which improves cattle performance.     

Comparison of grazing behaviour, dietary overlap and performance in non-lactating domestic ruminants grazing on marginal heathland areas

During the years 2000–2001, 7 non-lactating beef cows, 40 ewes and 40 does were managed in mixed grazing on a natural heathland vegetation plot (22 ha) with 20% improved pasture (perennial ryegrass) on a hill (1000 m a.s.l.) experimental farm located in the NW of Spain. Samples of faeces and vegetation components were collected monthly to estimate diet selection, using the alkane markers, and diet overlapping level. Animals were weighed monthly to quantify live weight changes and performance of the three livestock species during different periods (spring, summer, autumn, winter) of the grazing season.

The percentage of shrubs in the diet was significantly higher in the small ruminants (ranging between 36% and 85%) than in cows (less than 25%) in any period. Gorse (Ulex gallii) and heather (Erica spp., Calluna) percentages were always significantly higher in does than in ewes, except in autumn for heather. Herbaceous component (namely grasses) was higher in cattle (75–99%) than in small ruminants (15–64%). The lowest mean dietary overlap was found between cattle and goats (50.4%), with large differences during the grazing season, ranging between 20% and 70%.

The three animal species increased their live weight in the first grazing period (spring), when the mean sward height on the improved area was higher than 6.0 cm. However, when the sward height was lower than 3.5 cm (summer–winter), cows lost weight (− 437 g/day) while ewes and goats were still able to increase their weight (29 and 5 g/day, respectively).

Therefore, it seems that small ruminants, mainly sheep, are more suitable than cattle from the vegetation utilization and animal performance points of view, as cows were unable to maintain live weight when the preferred grass availability decreases. Goats were the species that included the highest proportion of heathland vegetation components in the diet, especially gorse, although their performance was significantly lower than in sheep. In consequence, small ruminant production systems could be more sustainable than cattle. The results indicate that mixed grazing of sheep and goats could be appropriate in these vegetation communities, allowing the development of sustainable systems, in which animal performance and the efficiency of resource use are maximized.     

Mefluidide effects on smooth brome composition and grazing cow-calf performance

Mefluidide, a plant growth regulator, was evaluated in two cow-calf grazing trials and one herbage trial on smooth brome (Bromus inermis) pastures stocked at recommended densities in eastern Nebraska. Mefluidide-treated pasture increased cow and calf production during August of 1982 (P = .03) and calf production was greater during July of 1983 (P = .09). Mefluidide-treated smooth brome pastures increased calf production over the 1982 grazing season (P = .11) and cow gain over the 1982 (P = .12) and 1983 grazing seasons (P = .13). Mefluidide decreased neutral detergent fiber (NDF) content and increased crude protein content of smooth brome during both years (P less than .05), and increased in vitro dry matter disappearance (IVDMD) in 1982 (P less than .05). In ungrazed smooth brome, mefluidide treatment appeared to shift dry matter production to green leaves from green stem and brown leaf and stem fractions. Cell wall components [NDF, acid detergent fiber (ADF) and lignin] of green leaves were not affected significantly by mefluidide treatment, although green stems treated with mefluidide were lower in ADF and lignin (P less than .05).     

Effects of salinomycin on ruminal characteristics and performance of grazing beef steers

Grazing trials were conducted for 2 yr using weanling Brahman crossbred beef steers to evaluate graded levels of salinomycin (0, 50, 100 or 150 mg. head-1.d-1) for 161 d and to evaluate salinomycin in a free-choice mineral supplement (99 d). The 40 and 48 steers in trials 1 and 2 had average initial weights of 198 and 285 kg, respectively. In trial 1, steers were group-fed to consume either 0, 50, 100 or 150 mg of salinomycin.head-1.d-1 in .9 kg ground corn while grazing bermudagrass pastures. Both linear (P less than .01) and quadratic (P less than .05) effects were observed for steer performance as salinomycin level increased from 0 to 150 mg.head-1.d-1. Linear increases (P less than .01) in ruminal NH3-N (mg/100 ml) and in the molar proportion of propionate and decreases (P less than .01) in butyrate and acetate/propionate were detected. In trial 2, mineral supplements with and without salinomycin were fed free-choice to steers on bermudagrass pasture. The mean salinomycin intake of 38 mg.head-1.d-1 was lower than anticipated as a result of the instability of salinomycin in the mineral supplement and the slightly lower intake (65 g/d) than anticipated (75 g/d). Performance of steers was not influenced by salinomycin supplementation in trial 2. The ionophore salinomycin at intakes over 50 mg.head-1.d-1 appears to increase the performance of steers grazing bermudagrass pasture.     

Effects of previous grazing nutrition and management on feedlot performance of cattle

Management strategies designed to improve grazing animal performance can influence feedlot performance and carcass traits both positively and negatively. In spite of the economic relevance of potential interactions between grazing and finishing performance, controlled experiments evaluating integrated production systems are limited in number. Effects of grazing treatments can result from, or be overshadowed by, changes in gut fill, thus making it difficult to assign precise costs to different phases of production. Published reports have considered the effects of stocking rate, duration of grazing, forage characteristics, supplementation, and growth-promoting implants on subsequent finishing performance. Improvements in cattle performance attributed to changes in stocking rate generally have been neutral to positive with respect to effects on finishing performance. Comparisons among forages have led to the suggestion that forage species may contribute to differences in gastrointestinal fill of grazing cattle, thereby influencing gain and efficiency during the subsequent finishing phase. Creep-feeding suckling calves generally has increased preweaning performance but has had relatively little influence on performance during the subsequent finishing phase. Grain supplementation of stocker cattle during the grazing period has improved grazing performance, but effects on subsequent feedlot performance have been inconsistent. Potential carryover effects from protein and mineral supplementation also have been inconclusive. Lack of congruence among studies is puzzling but may be the consequence of highly varied production systems, differences in experimental procedures, and changes in gut fill or mass of internal organs. Based on the studies reviewed, the expression or absence of compensatory growth during the finishing phase appears to be related to the nutritional quality of forages utilized in the grazing period, with higher quality forages tending to yield greater compensatory effects. The bulk of evidence with suckling cattle and stocker implants suggests that effects on subsequent finishing performance are minimal. Attention is drawn to the noticeable lack of research pertaining to integrated production systems. A more thorough understanding of the interactions among grazing nutrition and management, finishing performance, and carcass traits is needed to facilitate greater economic exploitation of these relationships.     

放牧率对绵羊体重及繁殖性能的影响

通过不同放牧率对内蒙古本地绵羊(母羊)连续2年(2008～2009)的体重和繁殖性能的影响的研究表明:(1)在试验期内,随着时间的推移,不同放牧率下的绵羊体重总体上都呈上升趋势;间隔1个放牧率或以上的处理间,存在不同程度的显著性差异;(2)绵羊的个体增重与放牧率之间存在负相关关系;而公顷增重与放牧率的关系符合二次曲线关系,在达到公顷最大增重前,随着放牧率的增大而增大,之后随着放牧率的增大减小;(3)单位家畜增重和单位面积增重的交点的生态学意义在于放牧率为1羊/hm2,公顷增重和家畜个体增重相同;单位家畜个体增重对应的畜产品最优放牧率为0.50羊/hm2,单位面积家畜最大增重对应的畜产品最优放牧率为2.38羊/hm2;(4)过高的放牧率导致绵羊出现空怀现象及产羔率下降;羔羊的初生重和个体增重均随着放牧率的增大而减小,但其显著性差异仅表现在较高的放牧率与较低的放牧率之间,而在相邻放牧率间差异不显著。     

Relationship between terrain use and performance of beef cows grazing foothill rangeland

A study was conducted on foothills rangeland to determine whether grazing patterns differed among cow breeds and to determine whether there was a relationship between individual grazing patterns and performance of beef cows. Hereford (HH), Tarentaise (TT), 3/4 Hereford x 1/4 Tarentaise (3H1T), 1/2 Hereford x 1/2 Tarentaise (HT), and 1/4 Hereford x 3/4 Tarentaise (1H3T) cows were observed during the summers of 1997 (n = 183) and 1998 (n = 159). Locations of individual cows were recorded two to three times per week during 1.5- to 2.5-h periods in the morning by observers on horseback. Statistical models included cow breed, age, and nursing status. Data from each year were analyzed separately. During 1997 and 1998, nonlactating cows were located at greater (P < 0.05) vertical distances from water than lactating cows. In 1998, nonlactating cows used steeper (P < 0.05) slopes than lactating cows. However, nonlactating cows did not travel as far horizontally from water (P < 0.05) as lactating cows in 1997. Younger cows (3 yr) traveled further (P < 0.05) from water both vertically and horizontally than older cows (5+ yr) in 1997, but not during 1998. Tarentaise and 1H3T cows were observed at greater (P < 0.05) vertical distances from water than HH cows during both years of the study. During 1998, TT and 1H3T cows used steeper (P < 0.05) slopes than HH cows. Using residual correlations, there were no consistent relationships between topographic aspects of individual grazing locations and cow weight, height, and body condition score. In 1997, cows with earlier calving dates and correspondingly heavier calf weaning weights used areas that had greater vertical distances to water; however, in 1998 there were no relationships (P > 0.05) of calving date and weaning weight with cow location. During both years, pregnant and nonpregnant cows used terrain similarly (P > 0.05), which suggests that cow reproductive performance was not related to terrain use. Grazing patterns in foothills rangeland varied among cow breeds. Performance of cows that used more rugged topography was similar to cows using gentler terrain.     

Effects of rate of gain during winter on subsequent grazing and finishing performance

Sixty mixed British breed yearling steers (237 kg) were used each year for 2 yr to study the effects of rate of gain during the winter on subsequent pasture and finishing performance. Winter gains of .28, .38 and .50 kg/d (P less than .05) were established for the low, medium and high gain treatments, respectively. Daily gain of steers on pasture was reduced (P less than .01) 81 g for each 100-g increase in winter daily gain. No differences in BW were observed among the treatment groups after grazing summer pasture. Wintering performance did not affect finishing performance. Daily gains during the finishing period increased slightly as pasture gain decreased due to increased feed intake, but efficiency was not altered. These data suggest that within this range of ADG during the winter and under the conditions of this study, it was not beneficial to winter cattle for an ADG more than .28 kg/d.