Interrelationship of growth hormone AluI polymorphism and hyperketonemia with plasma hormones and metabolites in the beginning of lactation in dairy cows

A polymorphic site of the growth hormone gene (AluI polymorphism) that results in an amino acid change at position 127 of the protein chain (leucine, L to valine, V) has been linked to differences in circulating metabolites and metabolic hormones of calves and bulls and to milk yield traits of lactating cows. Our objective was to investigate the interrelationship of this polymorphism with plasma concentrations of β-hydroxybutyrate, insulin, IGF-I and leptin in postpartum dairy cows. Blood samples were taken from clinically healthy, spring-calving, group-fed Holstein-Friesian cows (n = 257; 7 large-scale farms) 4–13 days after calving. Of all herds, 100 cows had plasma β-hydroxybutyrate levels above 1.2 mmol/l and 157 cows were normoketonemic. The proportion of valine carriers and LL cows was not different within groups of normo- and hyperketonemic animals. Genotype was not associated with plasma β-hydroxybutyrate, insulin, IGF-I and leptin levels either in all of the herds or in the two with the highest proportion of the valine allele carriers (n = 28, 72%). We found significantly lower insulin, IGF-I and leptin concentrations in the presence of hyperketonemia compared to normoketonemic cows. There were strong negative correlations between BHB and the other blood parameters, while insulin, IGF-I and leptin were positively related to each other. In conclusion, in the first two weeks after calving we could not demonstrate any effect of AluI polymorphism on plasma concentrations of β-hydroxybutyrate and metabolic hormones studied. Hyperketonemia was associated with a significant decrease in insulin, IGF-I and leptin blood levels. We infer that cows homozygous for the leucine allele or carrying the valine allele may have a similar endocrine and metabolic response to the challenge of increased nutrient demand early postpartum and that the presence of hyperketonemia is mainly linked to the hormonal and metabolic changes occurring at the onset of lactation.     

Maize silage particle length modulates feeding patterns and milk composition in loose-housed lactating Holstein cows

This study analysed feeding patterns and feed selective consumption by loose-housed lactating dairy cows fed diets based on maize silage (MS) with different particle length (PL) to establish its effects on overall dry matter intake (DMI) and productive performance. Twelve multiparous Holstein cows were offered a total mixed ration (TMR) with three different PL of MS at harvesting (i.e., long, medium, and short). Results demonstrated greater numbers of day-time meals (i.e., 07:30–19:00 h) when PL was decreased from long to medium (P < 0.05). Night-time (i.e., 19:00–06:30 h) changes in the feeding pattern included an increased amount of feed per meal (P < 0.05) and a tendency to increase eating time per meal (P < 0.10) in cows fed the short-PL diet. Lowering the PL of MS also lowered the selective consumption against physically effective fibre larger than 1.18 mm (peNDF_> 1.18; P < 0.05) and in favour of fine particles (i.e., particles passing through 1.18 mm screen; P < 0.01). Decreasing PL of MS from long to medium and short increased daily DMI as well as the intake of energy and other nutrients contained in the diet including the amount of peNDF_> 1.18 (P < 0.01). The decrease in the PL of the diet also was associated with increased milk protein and lactose yield and milk urea nitrogen (P < 0.05). The actual milk yield and fat-corrected milk were not affected by the diet (P > 0.10). Although lowering of the PL tended to increase daily milk energy output (P < 0.10), the ratio between energy milk output and the energy intake was linearly decreased (P < 0.01), indicating a lower milk efficiency for the lower-PL diets. In conclusion, particle length of MS in a TMR has the potential to modulate circadian feeding patterns, selective consumption of the feed, daily DMI, and milk composition in high-producing dairy cows.     

柑橘渣对奶牛泌乳性能、养分消化率及乳成分的影响

试验评估不同水平柑橘渣对奶牛泌乳性能、养分消化及乳成分的影响。将32头泌乳性能一致的奶牛随机分为4个组,每组4个重复,每个重复2头。对照组饲喂粗脂肪水平为3%的日粮,处理组分别饲喂粗脂肪水平为5.5%的日粮同时添加0(T1)、5%(T2)和10%(T3)柑橘渣。结果显示,与对照组相比,处理组奶牛的粗脂肪摄入量、干物质和粗脂肪表观消化率显著提高(P<0.05),T2和T3组奶牛粗蛋白表观消化率显著高于对照组和T1组(P<0.05)。与对照组相比,处理组乳中粗脂肪含量显著降低(P<0.05),总固形物含量显著降低(P<0.05),乳中粗脂肪产量显著降低(P<0.05)。对照组乳中C10∶0脂肪酸含量最高,而T3组乳中C8∶0脂肪酸和单不饱和脂肪酸浓度最高,饱和脂肪酸浓度表现最低。处理组乳中n-3/n-6脂肪酸显著高于对照组(P<0.05)。研究表明,在高脂肪(5.5%粗脂肪)日粮中添加5%或10%柑橘渣可以提高奶牛粗蛋白表观消化率,且对奶牛的泌乳量和乳品质无负面影响。     

高表达线粒体融合蛋白2(MFN2)可抑制高BHBA活化的奶牛肝细胞NF-κB炎性通路

为研究线粒体融合蛋白2(mitofusin 2,MFN2)对高β-羟丁酸(β-hydroxybutyrate,BHBA)活化NF-κB炎性通路的影响,体外培养奶牛肝细胞,添加不同浓度(0.0,1.2,2.4,4.8 mmol/L)的BHBA,并转染过表达MFN2的腺病毒,运用Western blot和qRT-PCR技术检测NF-κB炎性通路关键分子的基因和蛋白表达。结果显示,随着BHBA浓度的增加,IKBα和NF-κB p65的磷酸化水平以及IL-1β、IL-6和TNFα的mRNA表达均显著升高,MFN2的基因和蛋白表达水平则显著降低;过表达MFN2后,显著抑制了高BHBA诱导的IKBα和NF-κB p65磷酸化水平及IL-1β、IL-6、TNFαmRNA表达水平的升高。结果表明,在奶牛肝细胞中过表达MFN2可以显著抑制高BHBA活化的NF-κB炎性通路。     

四川凉山地区奶牛乳房炎主要病原菌分离鉴定及药敏情况分析

通过开展凉山地区奶牛乳房炎主要病原菌的分离鉴定和药敏情况试验,为指导凉山地区奶牛场临床合理使用抗生素以及提高抗生素的防治效果提供理论指导。通过采样、增菌培养、细菌鉴定、药敏试验、数据统计分析等方法,结果发现193 份患有乳房炎的乳样中有134 份分离出12 种病原菌,其中65 份检出两种及以上菌,占检出数的48.50%﹔共分离出234 株不重复菌株。分离率居前五位为：葡萄球菌63 株（26.9%）、大肠杆菌56 株（23.8%）、肺炎克雷伯菌42 株（17.9%）、肠球菌24 株（10.3%）、链球菌13 株（5.6%）。对本试验分离到的大肠杆菌、葡萄球菌、肺炎克雷伯菌等12 种菌中的10 种细菌药敏试验结果显示,不论是革兰氏阳性菌还是革兰氏阴性菌对试验选取的17 种常见抗生素均表现不同程度的耐药,有部分菌株还表现严重的多重耐药,有些菌株对部分药物耐药率达100.00%。     

1株奶牛源松鼠葡萄球菌的分离鉴定及耐药性分析

为确定奶牛垫料中是否含有病原菌并深入了解垫料中优势生长菌的类型、耐药性及致病性等情况,本试验进行了细菌分离培养、革兰染色镜检、生化试验鉴定、16S rDNA序列分析及同源性比对、药敏试验、小鼠致病性试验。结果显示,分离菌在普通营养琼脂平板上形成圆形、表面光滑的白色菌落,血琼脂平板上形成黏稠、较大的白色菌落。革兰染色镜检结果显示,分离菌为革兰阳性,球型,呈葡萄串状排列,或单个散落。生化试验结果显示,分离菌对木糖、葡萄糖、麦芽糖、果糖、乳糖、硝酸盐还原等呈阳性反应,而蜜二糖、木糖醇、山梨醇、尿素、V-P反应等呈阴性反应。16S rDNA序列分析结果显示,扩增的16S rDNA序列长度为1 298 bp,与松鼠葡萄球菌的核苷酸同源性达99.85%~100%;系统进化树结果显示,分离菌与松鼠葡萄球菌处于同一分支。动物试验结果表明,分离菌株对试验小鼠有较强的致病性,以0.2 mL/只（7.9×10⁸ CFU/mL）菌液的剂量接种小鼠,在48 h内死亡率为60%（3/5）。药敏特性分析结果显示,分离菌株对复方新诺明、氨苄西林等7种药物敏感,对克林霉素、头孢噻肟和头孢呋辛中度敏感,对青霉素、红霉素和林可霉素耐药。本研究为奶牛源松鼠葡萄球菌的分离鉴定及防控提供了参考依据。     

微生态制剂在奶牛养殖中的应用

随着畜禽养殖技术的不断提升,当代畜禽养殖业的发展方向逐渐由追求“数量”向追求“品质”发展。微生态制剂是利用正常微生物或促进微生物生长的物质制成的活的微生物制剂,具有改善动物饲料利用率,提高生长速度和机体免疫力,改善畜产品品质等作用。本文从微生态制剂的种类、作用机理以及在奶牛养殖中的应用效果和存在问题等方面进行阐述,为微生态制剂的发展提供思路。     

奶牛常见繁殖疾病诊断与治疗

中国乳制品消费水平位于全球前三,奶牛养殖业在国内具有很大的发展潜力。随着奶牛养殖业的发展和扩大,繁殖疾病成为影响奶牛场经济效益的因素之一。繁殖疾病的发生和很多因素有关,包括营养、卫生等方面,体内激素不平衡也会诱发繁殖疾病的发生。本文对引起奶牛繁殖疾病的主要发病原因、临床症状、病理变化、临床诊断及治疗方法进行归纳总结,以期为繁殖疾病的诊断治疗提供理论基础。     

Green tea polyphenols supplementation alters immunometabolism and oxidative stress in dairy cows with hyperketonemia

Peripartal cows often experience negative energy balance, and are therefore prone to suffering from metabolic diseases such as hyperketonemia, which causes financial losses in dairy farms. This study aimed to investigate the effect of green tea polyphenol (GTP) supplementation during the periparturient period on production performance, oxidative stress and immunometabolism in dairy cows with hyperketonemia. One hundred Holstein cows were assigned to GTP (0.2 g/kg DM; n = 50) or control (without GTP; n = 50) group based on body weight, previous milk yield, and parity on d 15 before expected parturition. Subsequently, 10 cows with hyperketonemia were selected from each group, according to blood β-hydroxybutyric acid (BHBA) concentration between 1.2 and 2.9 mmol/L from 2 to 3 d postpartum. All cows were fed a close-up diet and a lactation diet with or without GTP supply from 15 d prepartum until 30 d postpartum. Milk and blood samples were obtained from 20 cows selected with hyperketonemia on 10, 20, and 30 d postpartum. Compared with control cows, greater milk yield and lower somatic cell count were observed in GTP cows. The GTP group had lower concentrations of BHBA, free fatty acids, cholesterol, triglyceride, reactive oxygen species, malondialdehyde, and hydrogen peroxide, greater concentrations of glucose, lower activities of aspartate aminotransferase, alanine aminotransferase, and glutamyl transpeptidase, alongside greater activities of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity. Additionally, GTP supplementation up-regulated concentrations of interleukin-6 and interleukin-10, but down-regulated concentrations of tumor necrosis factor-α, interleukin-1β, interleukin-2, interleukin-8, and interferon-γ in plasma. Greater concentrations of plasma immunoglobulin G were also detected in the GTP group. Overall, the data suggested that GTP supplementation from 15 d prepartum to 30 d postpartum improved the milk yield and health status in cows with hyperketonemia during early lactation.