不同饲喂方式下荷斯坦公犊牛生产小牛肉的效果分析

研究了全乳饲喂(Ⅰ组)、牛奶+定量采食犊牛料(Ⅱ组)和牛奶+自由采食犊牛料(Ⅲ组)3种饲喂方式对荷斯坦公犊牛生产小牛肉的影响效果。结果表明:经3个月肥育后,Ⅰ组、Ⅱ组和Ⅲ组荷斯坦公犊牛的体质量分别为64.55、69.15、81.10kg,日增质量分别为380、400、560g,胴体质量分别为34.10、36.49、44.56kg,屠宰率分别为55.91%、55.89%、56.77%.其中,Ⅲ组犊牛体质量、体高、体斜长、胸围均显著高于Ⅰ组(P0.05),与Ⅱ组无显著差异(P0.05);III组犊牛全期平均日增质量、胴体质量及肉骨比也均显著高于Ⅰ组和Ⅱ组(P0.05).3组犊牛生产的小牛肉,肉质细嫩、柔软多汁、肉色呈浅红色,组间差异不显著,均属优质牛肉.说明牛奶+自由采食犊牛料的肥育方式可提高犊牛的生长速度和部分屠宰性能,是奶牛公犊牛较好的肥育方式.     

白头翁皂苷B4对犊牛生长性能、消化代谢和瘤胃发酵的影响

【目的】通过探究白头翁皂苷B4对犊牛生长性能、消化代谢和瘤胃发酵参数的影响。为新型饲料添加剂的开发提供理论基础。【方法】试验选取60头新生荷斯坦公犊牛,随机分为4组(每组15头),分别饲喂0(C组)、15(A1组)、30(A2组)、45(A3组)mg·d^-1的白头翁皂苷B4。试验周期为56d。在犊牛14、28、42和56日龄晨饲前称量体重,并在28、42和56日龄晨饲后2 h采集瘤胃液,测定瘤胃发酵参数。分别在42和63日龄进行两期消化代谢试验,测定营养物质表观消化率和能氮代谢指标。【结果】(1)白头翁皂苷B4对哺乳期犊牛体重和干物质采食量无显著影响(P>0.05),但犊牛14—28日龄的平均日增重与白头翁皂苷B4呈显著正相关(P<0.05),饲料转化比与添加量呈显著负相关(P<0.05),其中A3组犊牛的平均日增重显著高于C组(P<0.05),饲料转化比显著低于C组(P<0.05)。(2)A3组犊牛7—56日龄和7—14日龄的粪便评分和腹泻率显著低于C组(P<0.05),A2组犊牛15—28日龄的粪便评分和腹泻率显著低于C组(...     

补饲对放牧西门塔尔犊牛生长性能及血液指标的影响

为研究放牧加补饲对西门塔尔犊牛生长性能和血液指标的影响,选取内蒙古赤峰草原的放牧犊牛16头,分为放牧组和放牧加补饲组,测量体重、体尺等生长性能指标,用酶联免疫法测定血清中总蛋白(TP)、尿素氮(BUN)、葡萄糖(GLU)、白介素1(IL-1)和白介素2(IL-2)等血液指标。结果表明:1)在正试期的0~30 d 2组犊牛的日增重无显著差异(P>0.05),但在31~60 d放牧加补饲组犊牛日增重显著高于放牧组(P<0.05);在整个试验阶段,放牧加补饲犊牛体尺指标除胸围外,均高于放牧组,但差异不显著(P>0.05)。2)放牧加补饲使犊牛血清中尿素氮(BUN)和葡萄糖(GLU)含量显著提高(P<0.05);而总蛋白(TP)和甘油三酯(TG)含量差异不显著(P>0.05)。3)放牧加补饲犊牛免疫球蛋白G(IgG)和白介素1(IL-1)含量显著升高(P<0.05);而三碘甲状腺原氨酸(T₃)、甲状腺素(T₄)、生长激素(GH)和白介素2(IL-2)含量有高于放牧组的趋势,但差异不显著(P>0.05)。综上,补饲可提高放牧西门塔尔犊牛的生长性能,改善血液生化指标和血清激素水平,并可改善西门塔尔犊牛整体免疫水平。     

日粮磷水平对泌乳奶牛生产性能及磷排放的影响

 【目的】研究日粮磷水平对奶牛生产性能及磷排放量的影响,为中国奶牛饲养标准中磷需要量的制定提供数据参考。【方法】采用单因子试验设计,30头中国荷斯坦奶牛随机被分为3组,每组10头,分别饲喂干物质基础磷含量分别为0.32%、0.44%和0.56%的日粮,试验期75 d;其中,预试期15 d,正式期60 d,正式期最后5 d为采样期。【结果】磷的不同摄入量对采食量、生产性能及乳成分无显著影响（P＞0.05）,血清中钙、磷、碱性磷酸酶、羟脯氨酸以及唾液磷含量均处于正常值。0.32%磷日粮组每天通过粪尿向环境排磷量分别比0.44%和0.56%的磷日粮组少20.40 g（P＜0.01）和45.84 g（P＜0.01）;其中,粪中水溶性磷排放量分别比0.44%和0.56%磷日粮组少15.24 g（P＜0.01）和45.61 g（P＜0.01）,奶牛的饲养成本每天分别降低了0.60元/头和0.40元/头。【结论】日粮干物质基础磷水平为0.32%时对中国泌乳奶牛生产性能无不利影响,且显著降低粪磷含量,增加奶牛养殖的经济效益和生态效益。     

发酵玉米蛋白粉对犊牛生长、血液指标、瘤胃菌群和营养物质消化的影响

选取20头健康荷斯坦公犊,经两周适应期后,将犊牛按体重和日龄随机分为两组:①对照日粮组(未处理基础日粮);②FCGM日粮组(50 kg FCGM·kg~(-1)基础日粮;DM基础),试验期42 d。结果表明,日粮中添加FCGM显著(P<0.05)提高犊牛平均日增重和饲料效率;饲喂FCGM犊牛血浆TP、CAT、T-SOD、T-AOC、IgA和IgG含量显著(P<0.05)增加,UN和CHOL含量显著降低(P<0.05);试验组黄色瘤胃球菌、白色瘤胃球菌、栖瘤胃普雷沃氏菌、溶纤维丁酸弧菌和原虫相对丰度均显著(P<0.05)高于对照组;日粮中添加FCGM显著(P<0.05)增加CP和NDF表观消化率。日粮中添加FCGM可提高犊牛生长性能,改善血浆生化指标,提高犊牛抗氧化和免疫能力,调节瘤胃微生物菌群结构,促进营养物质消化。     

荷斯坦奶牛生长发育规律研究

[目的]探究我国南方集约化饲养条件下特定阶段荷斯坦奶牛生长发育及体态结构的变化。[方法]对扬州大学实验农牧场的279头荷斯坦奶牛(49头犊牛、35头青年牛、195头成年牛)进行体尺测量,将测量所得原始数据进行处理得出各个生理阶段的体尺指数,用SPSS 15.0软件分析体尺指数在各生理阶段、成年牛胎次间的变化,并绘制散点图对场内犊牛和青年牛的体高、体长、胸围指标进行拟合。[结果]牛只年龄越大,体型越长;犊牛生长发育均衡;青年牛不同月龄体尺发育不均衡;成年牛因胎次的不同其体态结构呈现出无规律性,但要注意对产胎多的母牛加强补充骨骼生长发育所需营养。[结论]为奶牛场的犊牛饲养管理、青年牛培育及饲养管理、成年牛的选种选配工作提供了借鉴。     

固定乳头对哺乳期仔猪乳头秩序及生产性能的影响

乳头秩序为影响哺乳仔猪生产性能的重要因素,其稳定程度为评价哺乳期仔猪乳头秩序的重要指标。试验选取胎次、体况相近待产民猪母猪、大白猪母猪各30头,将每品种母猪随机分成人工固定乳头组(15头)和自由选择乳头组(15头),人工固定乳头组将体重较小仔猪固定至母猪前部乳头吮乳、体重较大仔猪固定至母猪后部乳头吮乳,探究各组仔猪乳头秩序建立过程及其生产性能。结果表明,人工固定组仔猪哺乳初期乳头竞争水平低于自由选择组,建立稳定乳头秩序所需时间和哺乳次数均极显著低于自由选择组(P<0.01);民猪建立稳定乳头秩序所需时间少于大白猪(P>0.05)。人工固定组民猪仔猪21日龄窝重、体重、增重、断奶仔猪均匀度及成活率均显著高于自由选择组(P<0.05);人工固定组大白猪仔猪21日龄、断奶体重、增重及窝重均显著高于自由选择组(P<0.05);民猪、大白猪人工固定组仔猪腹泻频率显著低于自由选择组(P<0.05)。可见,人工固定乳头可降低仔猪乳头竞争水平,缩短乳头秩序建立时间,提高母猪泌乳力、仔猪成活率和生产性能。     

全乳添加小麦粉对荷斯坦公犊牛的屠宰性能及肉质的影响

对初生体重相近的20头荷斯坦公犊全乳饲喂至35日龄后,随机分为继续饲喂全乳的对照组和全乳中添加2%、4%和6%小麦粉的试验组,至90日龄进行测定,研究了对荷斯坦公犊的屠宰性能和肉质的影响.结果表明:在全乳中添加小麦粉可显著提高荷斯坦公犊的宰前活重、胴体重、净肉重、胴体产肉率和眼肌面积(P＜0.05),提高了肌肉的嫩度和脂肪含量(P＜0.05),且屠宰性能与肉质的改善效果随着小麦粉添加比例的增加而提高.因此,全乳中添加6%以内的小麦粉,既提高了屠宰性能,又能改善肉质.     

不同饲喂条件下犊牛胃形态发育的比较研究

为探讨3种不同饲喂条件对犊牛胃形态发育的影响,选择新生的健康荷斯坦公犊牛15头,每5头1组,随机分为牛奶和犊牛料自由采食组(Ⅰ组)、牛奶和犊牛料按比例定量采食组(Ⅱ组)和全乳饲喂组(Ⅲ组),饲喂3个月后,用大体解剖学方法,对3组犊牛胃的黏膜上皮颜色、胃黏膜形态各胃室及质量、大小比例进行观察和分析比较.结果表明:Ⅰ组犊牛胃前胃黏膜上皮颜色较深,呈现深褐色或黑色,Ⅱ组与Ⅰ组基本相似,但瓣胃黏膜上皮颜色略浅,Ⅲ组前胃与皱胃黏膜上皮颜色则均为白色;Ⅰ组、Ⅱ组黏膜形态与成年牛胃基本一致,Ⅲ组前胃黏膜乳头略显退化,但皱胃比前2组发达;Ⅰ组、Ⅱ组瘤胃质量占犊牛胃总质量的比例较大,分别为52.76%和49.78%,接近胃总质量的一半,而Ⅲ组为40.42%,占胃总质量的相对比例较小.不同饲喂条件对犊牛胃的形态发育影响显著,全乳饲喂条件下犊牛的前胃发育受到明显抑制,而牛奶与犊牛料自由采食或定量采食条件下的犊牛胃形态发育基本正常.     

Effect of group size and regrouping on physiological stress and behavior of dairy calves

Mixing or regrouping of calves from different pens is a common animal management practice on the farm, which frequently occurs after weaning and has a negative effect on calve welfare.  Social integration before regrouping may relieve stresses, but more evidences are needed to verify this hypothesis.  The present study aimed to investigate acute physiological and behavioral variations of individually- or group-housed calves after being introduced into a mixed group.  A total of 132 postnatal calves were randomly divided into groups of 1, 3, 6 and 12 animals (S, G3, G6, and G12; 6 replicates in each group) until 59 days of age.  At 60 days of age, every two replicates from different groups (S, G3, G6 and G12) were introduced in a larger pen which containing 44 of the aboved experimental calves.  Before and after regrouping, physiological parameters of stress, including heart rate (HR), saliva cortisol (S-CORT), saliva secretory immunoglobulin A (SIgA), interleukin-2 (IL-2), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) levels, and behavioral responses were recorded.  After regrouping, HR and S-CORT increased immediately (P<0.05), and higher (P<0.05) levels of such molecules were found in S calves compared to those in group-housed calves.  Levels of SIgA and IL-2 were decreased (P<0.05), and the lowest (P<0.05) IL-2 values were found in S calves compared to those in group-housed calves.  In addition, the introduced calves displayed a distinct behavior, including altered active and rest time, which was associated with negative emotions triggered by the novel surroundings.  Allogrooming, play, exploration behaviors and lying time were increased significantly (P<0.05) in group-housed calves than those in S calves.  Conversely, self-grooming, aggressive behaviors, standing and walking time were increased (P<0.05) in S calves than those in group-housed calves.  These findings suggest that individually-housed calves may be more susceptible to stressors arising from regrouping than group-housed calves, which consequently negatively affected behavioral and neuroendocrine responses.  Furthermore, moving calves with previous social experience may help mitigate regrouping stress.     

高比例植物蛋白的代乳粉对断奶犊牛消化道酶活性的影响

选取20头7日龄左右的荷斯坦奶公犊牛分配于试验组MR1、MR2、MR3和对照组CK,每组共5头.试验组MR1、MR2、MR3分别饲喂60%、70%、80%3种不同植物蛋白含量的代乳粉,对照组CK饲喂鲜奶,研究不同植物蛋白含量的代乳粉对断奶犊牛消化道主要消化酶活性的影响.犊牛8周龄时测定其小肠各段食糜中胰蛋白酶、糜蛋白酶和脂肪酶活性.结果表明,试验组MR1、MR2、MR3的小肠各段食糜中胰蛋白酶、糜蛋白酶活性均显著低于对照组CK(P＜0.05),且试验组中MR1的活性最高,MR3的活性最低.试验组MR1、MR2、MR3的小肠各段食糜中脂肪酶活性均显著低于对照组CK(P＜0.05),且试验组中MR1的活性极显著高于MR2、MR3(P＜0.01),MR2的活性最低.由试验结果得出,断奶犊牛消化酶的活性随着代乳粉中植物蛋白含量的升高呈下降趋势,其中植物蛋白的种类也对断奶犊牛消化酶活性有很大的影响.     

不同比例植物蛋白代乳粉对早期断奶犊牛免疫指标的影响

将20头7日龄左右荷斯坦公犊牛随机分为A、B、C、D四个组,每组5头,A、B、C组分别饲喂60%、70%、80%三种不同植物蛋白含量的代乳粉,D组饲喂牛奶作为对照组,研究不同植物蛋白含量的代乳粉对犊牛免疫相关指标的影响.犊牛7、14、30、60日龄时,颈静脉采血并分离血清.分别测定血清免疫球蛋白G(IgG)、血清总抗氧化能力(TAOC)、一氧化氮(NO)、溶菌酶(LZM)、碱性磷酸酶(AKP)水平.结果表明,30日龄前,犊牛血清IgG、TAOC 水平A和B组与D组之间差异均不显著(P>0.05),C组显著低于D组(P<0.05),30日龄后各组间差异均不显著(P>0.05).14～60日龄犊牛血清NO浓度A组和B组与D组比较无显著性差异(P>0.05),C组显著高于D组(P<0.05).血清AKP浓度在14～60日龄B和C组显著高于D组(P<0.05),A组与D组差异不显著(P>0.05).各日龄犊牛血清LZM在各组间差异均不显著(P>0.05).综合各指标考虑,代乳粉植物蛋白含量为70%左右时,有利于犊牛免疫机能的发挥,犊牛30日龄以后对70%及以下的植物蛋白含量的代乳粉表现出较好的适应性.     

荷斯坦奶牛与德系西门塔尔牛杂交对其后代产肉性能和肉品质的影响

为了提高荷斯坦奶牛后代的产肉性能和肉品质,将德系西门塔尔牛冻精冷配荷斯坦奶牛,选择杂交一代的公牛(试验组)和荷斯坦公牛(对照组)各20头,通过育肥和屠宰试验比较其生长发育指标、屠宰性状指标和肉品质指标。结果表明,与对照组相比,18月龄试验组体质量极显著提高7.74%,优质肉块质量牛柳+西冷、大米龙+小米龙分别极显著提高30.56%、27.07%,眼肌面积极显著提高21.09%,牛肉中粗蛋白、总氨基酸、谷氨酸、甘氨酸和天门冬氨酸的含量分别显著提高17.63%、8.19%、10.39%、19.19%和28.75%。综上,利用德系西门塔尔牛冻精冷配荷斯坦奶牛可以提高荷斯坦牛后代公牛的生长性能、产肉性能和肉品质。     

不同NFC/NDF水平饲粮对肉公犊牛生长性能和屠宰性能的影响

为研究非纤维性碳水化合物/中性洗涤纤维(NFC/NDF)水平对夏杂公犊牛生长性能、屠宰性能和肉品质的影响,选取2~3月龄健康、平均体重为(94.38±0.25)kg的夏杂断奶公犊60头,随机分为4组,每组15头。分别饲喂粗蛋白质水平相近,NFC/NDF为1.35(A组)、1.23(B组)、0.94(C组)和0.80(D组)的4种全混合饲粮。试验期105d,其中预试期15d,正试期90d。每天记录每头犊牛的采食量,在试验开始和结束时分别测定每头犊牛的体重、体尺;试验结束时每组随机选取6头犊牛进行屠宰试验,测定屠宰性能、器官鲜重和肉品质。结果表明:1)饲粮NFC/NDF水平对犊牛平均日增重和体斜长的增长率有显著影响(P0.05),A组高于其他各组;2)犊牛采食A组饲粮后胴体重达到111.40kg,显著高于C组和D组(P0.05),但对屠宰率和净肉率均无显著影响(P0.05);3)采食A组饲粮的犊牛肝脏和脾脏分别为3.25和0.70kg,显著高于其他3组(P0.05),且脾脏指数有随饲粮NFC/NDF水平降低而降低的趋势,对其他器官重量及指数均无显著影响(P0.05)。综上所述,NFC/NDF为1.35组的饲粮可提高犊牛生长性能,更能满足3~6月龄肉公犊牛生长需要。     

Evaluation of a povidone-iodine and chitosan-based barrier teat dip in the prevention of mastitis in dairy cows

Postmilking teat dip is an important tool used to prevent mastitis in the modern dairy industry. In this study, we evaluated the in vitro and in vivo efficacies of a barrier teat dip containing povidone-iodine and chitosan for the prevention of mastitis. In experiment 1, we evaluated the antibacterial effects of chitosans with different molecular weights against six mastitis-causing bacteria based on the minimal inhibitory concentration test. The results showed that 50 k Da chitosan had the maximum antibacterial activity compared with 5, 150 and 350 k Da chitosans. In experiment 2, the inhibition zone test indicated that the barrier teat dip with 4.0% povidone-iodine and 1.0% chitosan had higher(P0.05) in vitro antibacterial efficacy against most tested mastitis-causing bacteria than the barrier teat dip with 4.0% povidone-iodine and no chitosan. In experiments 3 and 4, we evaluated the efficacies of two postmilking teat dips, 1) a barrier teat dip containing 1.0% chitosan and 4.0% povidone-iodine and 2) a conventional nonbarrier product containing 10% povidone-iodine in a field trial at two commercial dairy herds(1 and 2). A 56-d split-udder experiment(experiment 3) was conducted using 47 lactating Chinese Holstein cows in herd 1. Both left teats were immersed in barrier postmilking dip, and both right teats were dipped with nonbarrier postmilking dip. During a 56-d split-herd experiment(experiment 4), a total of 139 lactating Chinese Holstein cows from herd 2 were allocated to two groups: 1) all teats of 67 cows were dipped in the nonbarrier teat dip, and 2) all teats of 72 cows were dipped in the barrier teat dip. Milk samples were collected and analyzed for somatic cell count(SCC), fat content, protein content, and fat-to-protein ratio prior to the start of sampling(0 d), and at 28 and 56 d after initiation. Bacteriological analysis was only performed on milk samples with SCC≥200 000 cells m L~(–1). In experiment 3, no differences(P0.05) in SCC, somatic cell score(SCS) or other milk quality indicators were observed between nonbarrier and barrier teat dip treatment teats throughout the experiment. At the end of experiment 4, compared with nonbarrier teat dip group, a reduction(P0.05) of 29% was observed for subclinical mastitis infection prevalence in the barrier teat dip group. In the barrier teat dip group, the subclinical mastitis infection prevalence on 56 d was lower(P0.05) than 0 d. No differences(P0.05) in milk qualities or clinical mastitis incidence were detected between groups. Bacteriological analysis demonstrated that the barrier product containing povidone-iodine and chitosan reduced the subclinical mastitis infection prevalence induced by mastitis pathogens. This effect was mainly due to the reductions in Klebsiella pneumoniae, Pseudomonas aeruginosa, and Escherichia fergusonii infections. Overall, the data indicated that a barrier teat dip containing 4% povidone-iodine and 1% chitosan was more effective than 10% povidone-iodine in preventing subclinical mastitis.     

Weaning methods affect ruminal methanogenic archaea composition and diversity in Holstein calves

The objective of the present study was to examine the effect of different weaning methods on the ruminal methanogenic archaea composition and diversity in Holstein calves.Thirty-six newborn Holstein bull calves were assigned to 1 of 3 treatments:(1)conventional weaning(d 56)and fed a high proportion of solid feed(CWS);(2)conventional weaning(d 56)and fed a high proportion of liquid feed(CWL);(3)early weaning(d 42)and fed with a high proportion of solid feed(EWS).High-throughput sequencing of the methyl coenzyme M reductase(mcr A)gene,which encodes theα-subunit of methyl coenzyme M reductase-the enzyme that catalyzes the final step in methanogenesis was used to determine the composition and diversity of rumen methanogens.No significant difference(P0.05)was observed for operational taxonomic units(OTUs)or richness indices,but diversity indices increased(P0.05)for calves fed high dietary solids.Predominant families across the three treatments were Methanobacteriaceae,Thermoplasmataceae and Methanomassiliicoccaceae.Calves in the EWS treatment had a higher(P0.05)relative abundance of Methanobrevibacter sp.strain AbM4 and Methanosphaera stadtmanae,while calves in the CWL treatment had a higher(P0.05)abundance of Methanosphaera sp.strain SM9.A positive(P0.05)relationship was identified between butyrate and Methanobrevibacter sp.strain AbM4.In conclusion,the composition and diversity of methanogens in the rumen of Holstein calves varied under the different weaning methods.This study identified a positive relationship between butyrate and Methanobrevibacter sp.strain AbM4,potentially reflecting correlations between ruminal fermentation variables and methanogenesis function.These in-depth analyses provide further understanding of weaning methods for intensified production systems.     

维生素及矿物元素补饲对奶牛生产性能及健康的影响

通过对16头断奶后犊牛、32头育成牛、82头泌乳牛、24头干奶牛基础日粮中补充维生素(VA、VD、VB3、VE)和矿物质(硒、硫酸亚铁、氧化镁)元素,研究营养料(维生素、矿物质元素)对不同生理阶段奶牛生产性能和健康的影响.试验分试验组和对照组,对照组只饲喂基础日粮,试验组基础日粮中补加营养料.结果表明:在奶牛基础日粮中补饲营养料能够显著影响奶牛产犊难易程度以及低产奶牛干物质采食量和产奶量(P≤0.05);对不同阶段育成牛体质量的增加有显著影响(P<0.05);对奶牛产后第1次发情时间、发情表现和高产奶牛产奶量的影响较小;能减少多种疾病的发生率,如胎衣不下、乳房炎、流产、蹄病等.     

营养调控剂对育肥牛的影响

选取45头新疆褐牛,分为3组,在同一营养水平下饲喂添加不同的营养调控剂,经过3个月的育肥后屠宰,结果表明,两个试验组与对照组相比,日增重(P>0.05)和屠宰率等差异不显著,净肉率和肉骨比方面却均有提高,分别为7.87;、33.44;和2.02;、24.69;.另选取荷斯坦公牛15头,以新疆褐牛为对照组,在同一营养水平下经过3个月的育肥后屠宰,结果表明,荷斯坦公牛在日增重上显著高于新疆褐牛对照组(P<0.01);荷斯坦公牛的屠宰率、净肉率和肉骨比均高于新疆褐牛对照组,分别提高达2.56;、5.34;和12.50;.     

日粮添加亮氨酸和苯丙氨酸对荷斯坦公犊生长性能及血清代谢物的影响

【目的】研究日粮添加亮氨酸和苯丙氨酸对犊牛生长性能和血清代谢物的影响,为亮氨酸和苯丙氨酸在奶牛高效生产中的应用提供理论参考。【方法】试验选取20头1日龄体重为(38±3)kg的荷斯坦公犊,随机分为4组,分别为对照组、亮氨酸组(1.435 g·L~(-1))、苯丙氨酸组(0.725 g·L~(-1))、混合氨基酸组(1.435 g·L~(-1)亮氨酸和0.725 g·L~(-1)苯丙氨酸),每组5头牛,各组以丙氨酸调节为等氮日粮。犊牛单独饲喂,试验共8周,预试期1周,正试期7周。试验犊牛单圈饲养,试验日粮由原奶和开食料组成。犊牛出生后,1 h内饲喂4.0 L初乳。此后1周为过渡期,日喂原奶2次,每次3.0 L。过渡期内以氨基酸添加量的20%为梯度逐天增加,至出生第6天达到添加量的100%。2—8周为正试期,日饲喂添加氨基酸的原奶2次。第2—3周每次3.5 L,4—8周每次4.0 L。第3周开始定量供给开食料,自由饮水。在犊牛1、3、5、7、8周龄测定体重、体高、体斜长和胸围,计算体躯指数和体长指数;采集10 mL血液用于获得血清,并检测其氨基酸组成、葡萄糖、尿素氮、胰岛素和胆囊收缩素。采用IBM SPSS Statistics V22.0统计软件GLM过程进行统计分析,采用LSD法进行多重比较。【结果】混合氨基酸组平均日增重显著低于其余3组(P0.05)。相对于对照组,各处理组显著提高最终体斜长(P0.05)。亮氨酸和苯丙氨酸具有降低最终体高的趋势(P0.10),而苯丙氨酸显著降低最终胸围(P0.05)。与对照组相比,亮氨酸组和混合氨基酸组显著提高犊牛8周龄体躯指数(P0.05)。但各组犊牛初始体重、体斜长、体高、胸围、体躯指数、体长指数和最终体重及体躯指数无显著差异(P0.05)。添加亮氨酸显著提高血清组氨酸、亮氨酸、苏氨酸、甘氨酸和总必需氨基酸的浓度(P0.05),趋于增加天冬氨酸和总氨酸浓度(P0.10),但显著降低丙氨酸和甘氨酸浓度(P0.05)。苯丙氨酸显著提高血清苯丙氨酸、谷氨酸和甘氨酸浓度(P0.05),对照组因添加丙氨酸调节为等氮日粮,其血清丙氨酸浓度显著高于亮氨酸组与混合氨基酸组(P0.05)。苯丙氨酸和亮氨酸对血清各种氨基酸浓度无交互效应(P0.05)。亮氨酸显著提高血清葡萄糖浓度(P0.05),苯丙氨酸降低血清葡萄糖浓度(P0.05),且与亮氨酸存在负交互效应(P0.05)。此外,苯丙氨酸显著提高血清尿素氮含量(P0.05),但亮氨酸和苯丙氨酸添加对血清中胰岛素及胆囊收缩素浓度无显著影响(P0.05)。【结论】日粮中添加亮氨酸可提高犊牛血清部分必需氨基酸、葡萄糖浓度、8周龄体躯指数和平均日增重。从以上指标可见,亮氨酸添加效果优于苯丙氨酸,但二者在影响血清葡萄糖浓度方面存在负交互效应。     

蚜虫的取食排蜜与繁殖行为概述

蚜虫行为包括取食行为、繁殖行为、防御行为、社群行为等,本文概述了蚜虫取食行为、排蜜行为、繁殖行为。指出通过对蚜虫取食、排蜜、繁殖行为的研究可以更好地了解其行为发生机制和方式等,为蚜虫的综合治理提供理论基础。