摄入水平和苜蓿替代禾本科干草对肉牛纤维消化瘤胃动力学和颗粒通过的影响

两个试验旨在评价肉牛日粮中紫花苜蓿替代禾本科干草的消化动力学。试验1：要测试的饲草组合分别为：100%大须芒草,25%苜蓿和75%大须芒草,50%苜蓿和50%大须芒草,100%苜蓿。采用非线性回归测定即刻可溶性分数A,潜在的可降解分数B,不降解分数C,干物质和中性洗剂纤维消失率。随着苜蓿添加量的增加,干物质分数A线性升高（P=0.03）,干物质和中性洗剂纤维分数B线性降低（P=0.01）,干物质和中性洗剂纤维消失率线性升高（P≤0.02）。试验2：采用2×2因子设计,测试苜蓿替代鸭茅干草和采食水平的影响。苜蓿添加水平为不添加或含25%（作为饲喂基础）,采食水平为每天限制在体重的1%（以干物质为基础）或自由采食。限饲组肉牛营养素摄入量最低（P≤0.05）,自由采食鸭茅干草的肉牛营养素摄入量居中,自由采食鸭茅干草和苜蓿的肉牛营养素摄入量最高。采食水平和饲草来源对除蛋白质外的所有营养素的总消化道表观消化率没有影响（P≥0.23）。与单独饲喂鸭茅饲草的肉牛相比,采食鸭茅干草和苜蓿的肉牛蛋白质总消化道表观消化率显著提高33%（P=0.01）。干物质和中性洗剂纤维消失的延迟时间不受苜蓿或采食水平影响（P≥0.20）。限制日粮组和自由采食组,与单独采食鸭茅饲草的肉牛相比,采食鸭茅饲草和苜蓿的肉牛对鸭茅饲草干物质和中性洗剂纤维的消失率更快（P≤0.01）。与限饲组肉牛相比,自由采食组肉牛对鸭茅饲草大、小颗粒的平均贮留时间有缩短的趋势（P≤0.06）。在自由采食和添加苜蓿的条件下,小颗粒鸭茅饲草通过率趋向于更快（P=0.09）。自由采食与鸭茅饲草平均贮留时间缩短和小颗粒鸭茅饲草通过率加快相关;然而添加苜蓿能提高小颗粒鸭茅饲草通过率,干物质和中性洗剂纤维消失率。     

STUDIES OF RESPONSE TO FERTILIZER NITROGEN

Fifteen out of 36 possible combinations of 3 cutting dates for hay, 3 rates of N application and 4 intervals between N application and cutting date were compared to study the effects of pre-harvest application of N on the N, P, K, Mg and Ca contents of the aftermath and the effectiveness of utilization of these elements. According to the method of calculation given by ARC (1), the control haycrop harvested on 16 June was deficient in N, Ca, P and Mg, and the aftermath which was given no further N after harvest was of low bulk, but adequate in mineral content. Earlier harvesting improved the quality of the hay, and increased the bulk and reduced the mineral content of the aftermaths. Applying 125.6 kg N/ha after harvest resulted in a satisfactory increase in bulk, plus an improved mineral content in the aftermath. Applying N before harvest resulted in increased uptake of N, K, Ca, P and Mg in the hay and in the increased percentage of N, K, and Ca in the DM of the hay. Very early application of pre-harvest N increased the percentage of Mg. The general effect of pre-harvest N on the aftermath was to reduce yield and uptake of N, K, Ca, P and Mg. Doubling the pre-harvest N raised the mineral uptake. Very early pre-harvest application resulted in low mineral uptake in the aftermath. The percentage of N, K and P in the aftermath was reduced by pre-harvest N applied at both levels and on both dates. Deferring the application of fertilizer N until 4 days after harvesting the hay crop produced the highest mineral contents in the aftermath, without reducing its bulk. Mineral uptake in the regrowths was linearly related to N uptake at 1.43 kg K, 0.34 kg Ca, 0.157 kg P, 0.006 kg Mg/kg N uptake.     

Interplay of rotational, relaxational, and shear dynamics in solid ⁴He

Using a high-sensitivity torsional oscillator (TO) technique, we mapped the rotational and relaxational dynamics of solid helium-4 ((4)He) throughout the parameter range of the proposed supersolidity. We found evidence that the same microscopic excitations controlling the torsional oscillator motions are generated independently by thermal and mechanical stimulation. Moreover, a measure for the relaxation times of these excitations diverges smoothly without any indication for a critical temperature or critical velocity of a supersolid transition. Finally, we demonstrated that the combined temperature-velocity dependence of the TO response is indistinguishable from the combined temperature-strain dependence of the solid's shear modulus. This implies that the rotational responses of solid (4)He attributed to supersolidity are associated with generation of the same microscopic excitations as those produced by direct shear strain.     

Humoral mediation of radiation-induced motivation in parabiont rats

Parabiont rat pairs with a skin-vascular anastomosis were used to test for a radiation-induced transferable humoral factor which would motivate aversive conditioning in a nonirradiated (shielded) recipient. The shielded partner, by tasting saccharinflavored fluid shortly after its partner was x-irradiated (360 roentgens), was aversively conditioned to saccharin. This was interpreted as evidence for a humoral motivating factor.     

STUDIES OF RESPONSE TO FERTILIZER NITROGEN

The effects of 59, 118 or 177 kg N/ha were measured on 7 occasions from 8 to 57 days after application to a perennial ryegrass sward in terms of changes in composition. The first increase Dt of N significantly raised percentages of CP, non-protein N, K, P, Ca, Na and Mg and significantly depressed percentages of DM, OM and OM digestihility. The second increment of N resulted in a further rise in the percentages of CP, true protein, non-protein N, K, P, Ca, Na and Mg; the percentages of DM and OM were further depressed but OM digestihility was not significantly depressed. Percentages of P and Na showed increased responses for the more mature herbage; while percentage non-protein N showed a more marked response in younger herbage. As herbage matured percentages of OM and Na rose, the latter only from days 16 to 45. All other attributes showed falling percentages to levels which could be inadequate for a 500 kg dairy cow yielding 15 kg milk. CP percentage reached this critical level (1.4% N) at days 37, 45 or 56 given 59, 118 or 177 kg N/ha; P percentage became critically low (< 0.36%) at days 27, 35 or 38, respectively; Mg percentage fell to the critical level (0.12%) at days 23, 35 and 46. Na percentage showed the reverse trend, being deficient (< 0.13%) in the earliest samples and becoming satisfactory from days 23 or 27 at 118 and 177 kg N/ha but it remained inadequate at 59 kg N/ba.     

Increased tolerance to annual ryegrass toxicity in sheep given a supplement of cobalt

SUMMARY To determine whether oral cobalt supplements could modify the clinical onset of annual ryegrass toxicity, groups (n = 5) of sheep were dosed orally with 0, 4 or 16 mg cobalt/day. After 3 weeks on this treatment, toxic ryegrass seed was added to their feed to provide 0, 0.15 and 0.30 mg corynetoxins/kg body weight, daily. Sheep receiving cobalt ingested 30% more toxin than did unsupplemented sheep before clinical signs developed (P = 0.03). There was no significant difference between groups receiving 4 and 16 mg cobalt. The results showed that cobalt delayed, but did not prevent, the onset of clinical signs of annual ryegrass toxicity.     

Microbial regulation in gorgonian corals

Gorgonian corals possess many novel natural products that could potentially mediate coral-bacterial interactions. Since many bacteria use quorum sensing (QS) signals to facilitate colonization of host organisms, regulation of prokaryotic cell-to-cell communication may represent an important bacterial control mechanism. In the present study, we examined extracts of twelve species of Caribbean gorgonian corals, for mechanisms that regulate microbial colonization, such as antibacterial activity and QS regulatory activity. Ethanol extracts of gorgonians collected from Puerto Rico and the Florida Keys showed a range of both antibacterial and QS activities using a specific Pseudomonas aeruginosa QS reporter, sensitive to long chain AHLs and a short chain N-acylhomoserine lactones (AHL) biosensor, Chromobacterium violaceium. Overall, the gorgonian corals had higher antimicrobial activity against non-marine strains when compared to marine strains. Pseudopterogorgia americana, Pseusopterogorgia acerosa, and Pseudoplexuara flexuosa had the highest QS inhibitory effect. Interestingly, Pseudoplexuara porosa extracts stimulated QS activity with a striking 17-fold increase in signal. The stimulation of QS by P. porosa or other elements of the holobiont may encourage colonization or recruitment of specific microbial species. Overall, these results suggest the presence of novel stimulatory QS, inhibitory QS and bactericidal compounds in gorgonian corals. A better understanding of these compounds may reveal insight into coral-microbial ecology and whether a therapeutic potential exists.     

Isolation and characterization of an adventitious avian leukosis virus isolated from commercial Marek's disease vaccines

Commercial Marek's disease (MD) vaccines produced by two manufacturers were tested for possible contamination with avian leukosis virus (ALV). Samples of MD vaccines manufactured by two companies (A and B) were received from a breeder company; samples were also received directly from vaccine company B. Using virus isolation tests, samples initially tested positive for subgroup E (endogenous) ALV. However, upon repassage, the vaccines also tested positive for exogenous ALV. The isolated exogenous ALV proved to be a subgroup A virus, as determined by flow cytometry using polyclonal chicken antibodies specific for various subgroups of ALV, and by DNA sequencing of the envelope glygoprotein (gp85). The exogenous ALV isolated from MD vaccines was inoculated in chickens from ADOL lines 15I(5) x 7(1) and 0 to determine its pathogenicity and compare it with that of Rous-associated-virus-1 (RAV-1), the prototype strain of ALV-A. Each chicken from each line was inoculated with approximately 10,000 infectious units of RAV-1 or the ALV-A isolated from vaccines termed B-39 virus at 7th day of embryonation. At hatch, and at 4, 8, and 16 wk of age, chickens were tested for viremia and cloacal shedding; chickens were also observed for ALV-induced tumors within 16 wk of age. Viremia and cloacal shedding results suggest that chickens from both lines were susceptible to infection with either virus. Within 16 wk of age, the proportion of ALV tumors induced by strain B-39 in line 0 and line 15I5 x 7(1) chickens was 0% and 12%, respectively, compared with 62% and 67% in chickens inoculated with RAV-1. The data indicate that commercial MD vaccines produced by two manufacturers were contaminated with endogenous subgroup E and an exogenous subgroup A ALV. Further, data from biological characterization suggest that the ALV-A isolated from commercial MD vaccines is of low oncogenicity, compared with that of RAV-1. GenBank accession numbers: The gp85 gene sequences of ALV isolated from commercial Marek's disease vaccines have been deposited in GenBank and assigned the following accession numbers: A46 subgroup A, DQ412726 ; B53 subgroup A, DQ412727; A46 subgroup E, DQ412728; B53 subgroup E, DQ412729.