影响饲料脂质酸败的因素及其评价指标

本文讨论了饲料脂质酸败的类型、评价指标和影响因素。     

日粮精粗比对活体外瘤胃发酵和烟酸、烟酰胺合成的影响

本试验旨在研究日粮精粗比对活体外瘤胃发酵和烟酸、烟酰胺合成的影响。以4头装有永久性瘤胃瘘管的成年荷斯坦阉公牛作为瘤胃液供体,选用淀粉、微晶纤维素、酪蛋白3种成分配制成相同粗蛋白质水平(13.5%,DM)和不同精粗比(30:70、50:50、70:30,DM)的3种纯合日粮作为发酵底物。应用人工瘤胃体外产气量法进行培养发酵并测定产气量、挥发酸及发酵液中烟酸、烟酰胺含量的变化。结果表明,提高日粮精粗比可极显著降低发酵液pH、乙酸/丙酸摩尔比、乙酸摩尔比(L,P<0.01),显著降低氨态氮浓度(L,P<0.05),但却极显著增加72 h产气量、总挥发酸浓度、丙酸和丁酸摩尔比(L,P<0.01)。随日粮精粗比的提高,瘤胃发酵液中总烟酸(烟酸+烟酰胺)、烟酰胺浓度在24和48 h均呈线性增加(L,0.050.10)。由此得出,日粮精粗比可改变活体外瘤胃发酵模式和影响瘤胃微生物合成总烟酸和烟酰胺,且随日粮精粗比的上升,瘤胃合成总烟酸、烟酰胺的数量呈线性增加趋势。     

牛细小病毒病毒样颗粒的组装及其免疫原性评价

为研究牛细小病毒(BPV)VP2衣壳蛋白自组装病毒样颗粒(VLPs)以及VLPs的免疫原性.本研究以BPV-1型C7-5中国分离株的基因组序列为模板扩增VP2蛋白的编码基因,将其克隆至腺病毒穿梭载体pShuttle-CMV中,利用E.coliB J5183内同源重组将VP2基因插入腺病毒骨架质粒pAdEasy-1中,获得携带BPVVP2基因的重组腺病毒质粒(pAd-BPV-VP2).该重组质粒经Pac Ⅰ线性化后转染Ad293细胞,获得重组腺病毒rAd-BPV-VP2,第8代时滴度为107.25 TCID50/mL.间接免疫荧光、westemblot以及电镜观察结果显示,BPV VP2蛋白可以在腺病毒系统中稳定表达,并有效组装VLPs.将rAd-BPV-VP2肌肉注射免疫BALB/c小鼠,结果显示,针对BPV的血清IgG和中和(VN)抗体分别于加强免疫后2周和8周达最高水平,高峰抗体可持续至15周,VN抗体的最高滴度可达1:4 000.此外,与对照小鼠血清相比,免疫小鼠血清中的IL-2、IL-4及IFN-γ含量显著升高(p＜0.05).结果表明,rAd-BPV-VP2免疫小鼠后可以诱导机体产生针对BPV的特异性体液和细胞免疫.本研究为BPV的免疫预防及载体的开发奠定了基础.     

羊绒与羊毛的PCR-RFLP识别方法

羊绒价格昂贵,在销售中时常出现掺假现象,最常见的是用羊毛,因此精确识别羊绒和羊毛纤维的方法非常重要。本试验采用聚合酶链式反应-限制性片段长度多态（PCR-RFLP）的技术方法,利用提取的羊绒和羊毛线粒体基因组,根据细胞色素b（Cytochrome b）基因已知的DNA序列设计引物,通过内切酶SspⅠ进行酶切,得到不同的片段长度,根据酶切图谱鉴别羊绒和羊毛样品,用来进行羊绒掺假试验的定性检测。     

Changes in hormones, growth factor and lipid metabolism in finishing pigs fed betaine

An experiment was conducted to investigate the effect of dietary betaine supplementation on carcass characteristics, hormones, growth factor and lipid metabolism in finishing pigs. Forty-eight crossbred barrows and gilts (Seghers × Seghers × Duroc) weighing about 55 kg were divided into two groups, each with three replicates of eight pigs (four barrows and four gilts) per replicate, and fed corn–soybean meal basal diets supplemented with 0 and 0.125% betaine for 42 days. At trial termination, two pigs (one barrow and one gilt) weighing about 90 kg were selected from each replicate and slaughtered for analyses. The results showed that betaine increased carcass lean percentage and longissimus muscle area by 5.19% (P < 0.01) and 17.85% (P < 0.01), respectively, and decreased carcass fat percentage and average backfat thickness by 13.07% (P < 0.01) and 10.30% (P < 0.05), respectively. Serum growth hormone, insulin-like growth factor I, free triiodothyronine, free thyroxine and insulin levels in pigs fed betaine were elevated by 45.61% (P < 0.01), 55.50% (P < 0.01), 57.95% (P < 0.01), 51.80% (P < 0.01) and 42.34% (P < 0.05), respectively. Fatty acid synthase activity in the 10th rib subcutaneous adipose tissue was decreased by 24.35% (P < 0.05) with betaine supplementation, whereas hormone-sensitive lipase activity was significantly increased (P < 0.05). Meanwhile, serum free fatty acids concentration in betaine-fed pigs was 25.75% higher compared to controls (P < 0.01). The study suggested that betaine could induce changes in hormones and growth factor in finishing pigs, and therefore could inhibit fat synthesis through reducing lipogenic enzymes activities and promote fat degradation by increasing hormone-sensitive lipase activity, with a resultant decrease in adipose tissue mass and improvement in carcass characteristics.     

Effects of dietary neutral detergent fibre on production performance, nutrient utilization, caecum fermentation and fibrolytic activity in 2- to 3-month-old New Zealand rabbits

An experiment was conducted to determine the effects of different dietary neutral detergent fibre (NDF) levels on growth performance, nutrient utilization, caecum development, caecal fermentation, slaughter performance, immune organ and fibrolytic activity in 2- to 3-month-old New Zealand meat rabbits. Eighty 2-month-old rabbits were allocated in individual cages for five treatments in which they were fed each diet with NDF at 240, 270, 300, 330 and 360 g/kg respectively. The results are as follows: the average daily gain of 300 g/kg NDF group was the highest (30.09 g/day) and higher than that of 240 g/kg NDF group (p < 0.05). The feed/gain ratio of 300 g/kg NDF group was the lowest (4.27) and lower than those of 240 and 360 g/kg NDF groups (p < 0.05). The coefficient of total tract apparent digestibility (CTTAD) of energy, crude protein, crude fibre and ether extract decreased when dietary NDF increased (p < 0.05); CTTAD of NDF increased when dietary NDF increased (p < 0.01). Digestible nitrogen and retained nitrogen of 240, 270, 300 and 330 g/kg NDF groups were higher than that of 360 g/kg NDF group (p < 0.05). The caecum weight, the proportion of caecum weight to body weight and the acetic acid ratio of volatile fatty acid rose when dietary NDF concentration increased (p < 0.05). The NH(3)-N concentration of caecum dropped when dietary NDF increased (p < 0.05). The fibrolytic activity increased when the dietary NDF increased (p < 0.01).     

大豆磷脂油对河田鸡脂肪代谢与肉质性状的影响

研究了大豆磷脂对河田鸡生产性能、脂肪代谢和肉质性状的影响。结果表明，在日粮中添加大豆磷脂，可改善生产性能，降低料肉比，提高肌内脂肪含量，而降低腹脂率。在日粮中添加大豆磷脂可以显著降低肝脏苹果酸酶(ME)活性以及降低肌肉的滴水损失、烹饪损失、剪切力。     

银合欢对肉鸡临床毒性及减毒的研究

为研究银合欢对肉鸡的临床毒性和减毒作用,250只10日龄AA肉鸡随机分为五组,每组50只.在试验组的日粮中分别添加5%,10%,20%的银合欢进行试验,为期50天.通过对肉鸡生产性能,血液激素水平和粪中含羞草素含量的测定,结果显示适量添加银合欢可增加平均日增重,平均日采食量,减低饲料消耗率.银合欢的安全添加量应不超过饲料量的5%.     

鸡蛋消毒方法的对比研究

采用5种消毒方法对鸡蛋蛋壳表面细菌进行杀菌效果试验,结果表明,各处理组之间抑菌效果差异显著(P＜0.05),杀菌效果优劣依次为开水浸烫＞甲醛熏蒸＞过氧乙酸熏蒸＞高锰酸钾浸泡＞过氧乙酸浸泡,开水浸烫操作技术难度较大,容易引起蛋壳破裂,适宜实际生产的消毒方法为过氧乙酸熏蒸和甲醛熏蒸.将消毒处理后的鸡蛋在温度25℃,相对湿度60%～80%贮存20天,开水浸烫处理组鸡蛋仍保持较鲜的品质,其余各组鸡蛋品质较差.结果表明,常规消毒方法(除开水浸烫法)只能抑制蛋壳表面微生物的生长繁殖,不能延缓鸡蛋品质下降达到保鲜鸡蛋的作用.     

羊附红细胞体病PCR检测方法的建立

根据羊附红细胞体的16S rRNA基因参考序列，设计1对特异性引物．建立了检测羊附红细胞体的PCR技术。用本方法从感染血样中特异扩增出1条预期大小为1169bp的片段。该方法灵敏、快速、特异性高．可用于羊附红细胞体病的早期快速诊断和流行病学调查。