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21.
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)。  相似文献   
22.
Salt cedar (Tamarix spp.) readily invades and dominates riparian areas and lake basins throughout the western United States. Traditional control efforts (chemical and mechanical control) are expensive and provide limited long-term control. The salt cedar leaf beetle (Diorhabda elongata) provides a method of biological control through reduction in cover. However, population establishment of leaf beetles in some locations is often difficult because of environmental conditions. In previous research, goats readily consumed salt cedar, offering an alternative method of reducing salt cedar cover. For this study, we determined if sheep would consume salt cedar and consume a similar amount as goats. Twelve Rambouillet and 12 Suffolks lambs were fed salt cedar once daily (Trial 1) and three times daily (Trial 2). Intake of salt cedar by sheep was compared between breeds and with intake of salt cedar by goats (n = 10). Salt cedar was fed once a day in Trial 1 for 30 min over 15 d. Intake was recorded daily for individual animals. In Trial 2, salt cedar was offered three times daily for 13 d with intake recorded. There were no differences (P > 0.05) between breeds of sheep. In addition, sheep consumed more salt cedar than goats except on the last day of the study. When salt cedar was offered three times daily, both breeds of sheep increased intake and gained weight over the 13 d of feeding in Trial 2. By the end of the study, intake appeared to still be increasing. Collectively, these results illustrate that both Rambouillet and Suffolk sheep will consume a similar amount of salt cedar as goats and will provide another species of livestock that can be potentially used to reduce salt cedar cover.  相似文献   
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24.
Grazing behavior, diet selection and weight gain of heifers (with or without social models) were assessed in an unfamiliar site containing high plant diversity. The study was performed within a tropical forest ecosystem containing a mixture of grass forb/herb, shrub and tree species. Ten inexperienced crossbred Bos taurus × Bos indicus heifers (7 ± 1 months old) were randomly assigned to one of two groups: naive or naive + social model (sm) and two experienced heifers (16 months old) were assigned to the second group. Naive heifers were bottle-nursed from days 2 to 90 after birth and began grazing at 1 month of age in tropical grass monocultures, while experienced animals had been foraging in sites containing a high diversity of plant species for 3 months prior to the study. Each group grazed in separate paddocks for a 12-week period during the rainy season, and animals were observed using focal sampling from 7:00 to 19:30 h to assess diet composition based on bite counts. Weight gain was assessed every 14 days. Paddocks contained from 1481 to 1789 kg/ha of herbaceous dry matter, enough to support the heifers throughout the study without affecting diet selection. Shrub and tree cover ranged from 55.2 to 58.4% across treatments. Bites per minute were adjusted to a log-scaled quadratic-plateau model and the curves showed no differences between treatments (P = 0.756). However, diet composition differed between groups (P < 0.001), with naive + sm heifers ingesting a greater proportion of trees (P < 0.001) and shrubs (P = 0.02), while naive heifers ingested more forb/herbs (P = 0.02); no difference in grass consumption was observed (P = 0.92). Heifers in both treatments consumed the same plant species (50 from 26 families). Over time, utilization of several plant species increased or decreased (P < 0.05), eventually leveling off for the remainder of the study. Although differences in diet composition were observed, they did not affect overall weight gain (117 and 113 g/day in the naive and naive + sm groups, respectively; P = 0.913). However, initial post-weaning weight loss was avoided in the naive + sm group. Social learning facilitates a higher use of shrubs and trees in tropical pastures containing a high diversity of plant species with different growth habits. As many plant species have high potential as forage, more effort should be placed on developing mechanisms to increase their dietary inclusion by cattle.  相似文献   
25.
The aim of this study was to compare the effects of rotational and continuous grazing on herbage mass (HM), organic matter digestibility (dOM) and intake (OMI) and live weight gain (LWG) of sheep grazing on the inner Mongolian steppe, China at a stocking rate of 4.5 sheep/ha during the growing season. In the years 2005 and 2006, four 2-ha plots were used of which two were divided into four 0.5 ha paddocks each for rotational grazing, where sheep were moved each 10 days to the next paddock. The dOM was estimated from faecal crude protein concentration and OMI by oral administration of titanium dioxide. Herbage mass was similar in both grazing systems and dOM and OMI were higher (p < 0.05) at continuous grazing than at rotational grazing, but LWG did not differ probably because of extra energy expenditure for grazing and walking in a larger area. The dOM and OMI decreased (p < 0.05) with progress of the growing season and differed between years. Since precipitation during the growing season in both years was lower than the 30 years average which was probably the reason that positive effects of non-grazing periods on herbage regrowth and quality at rotational grazing could not occur, further studies are required in years with average precipitations before a final evaluation of these grazing systems can be made. Moreover, it seems necessary to quantify energy expenditure for physical activity of animals in grazing studies.  相似文献   
26.
日粮中添加丙烯酸对绵羊消化代谢的影响   总被引:1,自引:1,他引:1  
选取25只身体健康,体重32kg左右的8月龄中国美利奴(新疆型)细毛公羊,日粮精粗比为25∶75,采用分组试验设计,分别是对照组、添喂丙酸8,12mmol/(d·只)组和添喂丙烯酸8,12mmol/(d·只)组,研究丙烯酸对绵羊消化代谢和体增重的影响。结果表明,与对照组和添喂丙酸组相比,添喂丙烯酸组绵羊干物质采食量没有显著差异(P>0.05);添喂丙烯酸组与对照组相比,半纤维素消化率提高5.15%~9.70%,纤维素消化率提高3.64%~5.73%,但差异不显著(P>0.05);8mmol丙烯酸组钙、磷的消化率分别高于8mmol丙酸组2.86%和8.39%,但差异不显著(P>0.05);添喂8,12mmol/(d·只)丙烯酸组绵羊的尿氮排出量(g/d)分别低于对照组12%和18%,而N保留率与对照组相比分别提高5.35%和3.91%,但均没有显著差异(P>0.05)。添喂丙烯酸组绵羊的体增重和饲料利用率与对照组和丙酸组相比没有显著差异(P>0.05)。本研究表明,添喂丙烯酸对绵羊的采食量、干物质、有机物、粗蛋白、纤维素、半纤维素的消化量(率)均无显著影响(P>0.05),对绵羊氮、钙、磷的代谢无显著影响(P>0.05)。  相似文献   
27.
The objective of this study was to evaluate the effects of feeding vitamin and mineral (VTM) supplement and (or) rate of gain (GAIN) during early gestation on amino acid (AA) concentrations in allantoic fluid (ALF) and amniotic fluid (AMF) and maternal serum. Seventy-two crossbred Angus heifers (initial BW = 359.5 ± 7.1 kg) were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement with main effects of VTM supplement (VTM or NoVTM) and rate of gain (GAIN; low gain [LG], 0.28 kg/d, vs. moderate gain [MG], 0.79 kg/d). The VTM treatment (113 g•heifer−1•d−1, provided macro and trace minerals and vitamins A, D, and E to meet 110% of the requirements specified by the NASEM in Nutrient requirements of beef cattle. Washington, DC: The National Academies Press. doi:10.17226/19014, 2016) was initiated 71 to 148 d before artificial insemination (AI). To complete the factorial arrangement of treatments, at breeding heifers were either maintained on the basal diet (LG), or received MG diet which was implemented by adding a protein/energy supplement to the LG diet. Thirty-five gestating heifers with female fetuses were ovariohysterectomized on d 83 of gestation and maternal serum, ALF, and AMF were collected. Samples were analyzed for concentrations of neutral AA: Ala, Asn, Cys, Gln, Gly, Ile, Leu, Met, Phe, Pro, Ser, Thr, Trp, Tyr, and Val; cationic AA: Arg, His, and Lys; and anionic AA: Asp and Glu. In serum, a VTM × GAIN interaction (P = 0.02) was observed for Glu, with greater concentrations for VTM-LG than VTM-MG. Concentrations of serum Cys, Met, and Trp were greater (P ≤ 0.03) for MG than LG. In ALF, concentrations of Glu were affected by a VTM × GAIN interaction, where VTM-MG was greater (P < 0.01) than all other treatments. Further, ALF from VTM had increased (P ≤ 0.05) concentrations of His, Asp, and 12 of the 14 neutral AA; whereas GAIN affected concentrations of Arg, Cys, and Asp, with greater concentrations (P ≤ 0.05) in MG heifers. In AMF, AA concentrations were not affected (P ≥ 0.10) by VTM, GAIN, or their interaction. In conclusion, increased concentrations of AA in maternal serum and ALF of beef heifers were observed at d 83 of gestation in response to VTM supplementation and rate of gain of 0.79 kg/d, which raises important questions regarding the mechanisms responsible for AA uptake and balance between the maternal circulation and fetal fluid compartments.  相似文献   
28.
Icelandic Cattle is a local dairy cattle breed in Iceland. With about 26,000 breeding females, it is by far the largest among the indigenous Nordic cattle breeds. The objective of this study was to investigate the feasibility of genomic selection in Icelandic Cattle. Pedigree-based best linear unbiased prediction (PBLUP) and single-step genomic best linear unbiased prediction (ssGBLUP) were compared. Accuracy, bias, and dispersion of estimated breeding values (EBV) for milk yield (MY), fat yield (FY), protein yield (PY), and somatic cell score (SCS) were estimated in a cross validation-based design. Accuracy (r^) was estimated by the correlation between EBV and corrected phenotype in a validation set. The accuracy (r^) of predictions using ssGBLUP increased by 13, 23, 19, and 20 percentage points for MY, FY, PY, and SCS for genotyped animals, compared with PBLUP. The accuracy of nongenotyped animals was not improved for MY and PY, but increased by 0.9 and 3.5 percentage points for FY and SCS. We used the linear regression (LR) method to quantify relative improvements in accuracy, bias (Δ^), and dispersion (b^) of EBV. Using the LR method, the relative improvements in accuracy of validation from PBLUP to ssGBLUP were 43%, 60%, 50%, and 48% for genotyped animals for MY, FY, PY, and SCS. Single-step GBLUP EBV were less underestimated (Δ^), and less overdispersed (b^) than PBLUP EBV for FY and PY. Pedigree-based BLUP EBV were close to unbiased for MY and SCS. Single-step GBLUP underestimated MY EBV but overestimated SCS EBV. Based on the average accuracy of 0.45 for ssGBLUP EBV obtained in this study, selection intensities according to the breeding scheme of Icelandic Cattle, and assuming a generation interval of 2.0 yr for sires of bulls, sires of dams and dams of bulls, genetic gain in Icelandic Cattle could be increased by about 50% relative to the current breeding scheme.  相似文献   
29.
日粮中精料和牧草比例对舍饲山羊增重的影响   总被引:9,自引:0,他引:9  
报道了在四川省洪雅县进行的一项山羊舍饲试验。试验分3个阶段、4个分组,每组8只5月龄的波尔×成都麻羊杂交公羔(去势),按不同精料与牧草配比饲喂。在舍饲条件下,无论以哪种牧草为基础日粮,随着补饲精料比例的增加,总的干物质采食量相应增加,而牧草采食量有所下降。以牛鞭草为基础日粮时,如果不补饲精料,山羊日增重很低,补饲精料可明显提高日增重。在牛鞭草日粮的基础上增加苜蓿干草,最初阶段因试验羊不太适应,导致日增重降低,但是经过约2周的适应之后,山羊日增重显著提高,但苜蓿干草成本较高,用于饲养山羊并不划算。以多花黑麦草为基础日粮时,山羊增重效果最好,依补饲精料比例的不同(12%~43%),山羊日增重130~189g,10月龄时的胴体重为17.56~25.23 kg。以黑麦草为基础日粮结合补饲精料虽可以提高山羊日增重,但增加精料导致成本过高,净收入降低。综合比较,在黑麦草基础上添加10%精料(干物质基础)的配比最好,每只羊每日可通过增重获得0.64元净收入。  相似文献   
30.
In the horse, the body condition score (BCS) system to assess subcutaneous fat deposition is a useful tool for making feeding management decisions. The system includes assessing fat deposition at six body areas (neck, withers, shoulders, ribs, loin, and tail head) and was developed in Quarter Horse mares. It has not been tested for use on other breeds or genders, possibly compromising the system's ability to describe fat accretion in other classes of horse. The objective of this study was to examine the ability of the previously developed fat accretion characteristics to describe fat deposition in mature Thoroughbred (TB) geldings. An additional goal was to determine whether fewer body areas could be used. Fifteen mature TB geldings were fed for weight gain over an 8-month period on one of two diets and were independently assessed for BCS on a monthly basis by two judges. BCS was determined by averaging the scores that were assigned to each of the six body areas. Fat accretion characteristics were also recorded. Across both diets, the neck area scored significantly higher than the withers and loin (P < 0.05) throughout the study. A BCS derived only from the body areas of neck, shoulders, ribs, and tailhead was found to accurately predict the six body area−derived mean BCS. The results of this study provide justification for modifications of the BCS system for use in TB geldings and also demonstrated that fewer body areas can be used to accurately predict mean BCS.  相似文献   
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