Validation of a bulk tank milk antibody ELISA to detect dairy herds likely infected with bovine viral diarrhoea virus in New Zealand

AIMS: To assess the sensitivity and specificity of a bulk tank milk (BTM) antibody enzyme-linked immunosorbent assay (ELISA) to detect likely infection of a dairy herd with bovine vi- ral diarrhoea virus (BVDV). The ELISA was subsequently used to estimate the prevalence of likely infected herds in parts of the North Island of New Zealand.

METHODS: BTM samples from 724 randomly selected dairy herds in the Waikato, Bay of Plenty and Northland regions of New Zealand were tested for BVDV antibodies. From this group, 20 herds were again randomly selected from each of the quartiles of the ELISA percentage inhibition (%INH) result. From each participant herd, serum from 15 randomly selected calves aged 6–18 months and 15 cows was collected and tested using an indirect blocking ELISA for BVDV antibodies.

RESULTS: Among serum results from calves from 50 herds available for analysis, 34 (68%) herds were classified as likely non-infected (0-3 seropositive among 15 calves) and 16 (32%) as likely infected (5–15 seropositive among 15 calves). Receiver- operator characteristic (ROC) analysis identified an optimal cut-off for BTM of 80%INH associated with 81% sensitivity and 91% specificity for likely herd infection. The prevalence of BVDV antibodies in cows within herds and %INH for BVDV in bulk milk were positively correlated (p<0.01). The association between bulk milk %INH and the prevalence of BVDV antibodies in calves was stronger than the same association in cows. Based on the threshold of 80%INH, the 95% confidence interval (CI) for prevalence of likely infection in the 724 herds in the Waikato, Bay of Plenty and Northland regions of New Zealand was 12–17%. Vaccination against BVDV was not significantly associated with the likely infection status of the herd based on prevalence of BVDV antibodies among calves.

CONCLUSION: An ELISA test result for BVDV antibodies in BTM ≥80%INH can be used as a threshold to indicate the presence of likely infection with BVDV in dairy herds in New Zealand, with 81% sensitivity and 91% specificity.     

Phosphorus net absorption in dairy cows subjected to abomasal infusion of inorganic phosphorus – a pilot study

In this pilot study, the effects of phosphorus (P) supply on inorganic phosphorus (P_i) net absorption in dairy cows were investigated. Three non‐lactating, non‐pregnant, rumen‐fistulated Swedish Red breed dairy cows were studied in a 3 × 3 Latin square design. Monosodium dihydrogen orthophosphate dihydrate (NaH₂PO₄*2H₂O) was continuously infused into the abomasum for 4 days. The solutions provided 0, 14.4 or 28.8 g P_i/day. Rumen fluid volume and outflow rate were estimated at day four of each experimental period using cobalt‐lithium EDTA as an external marker. Acid insoluble ash in feeds and faecal samples was used to quantify P faecal excretion. Concentrations of P_i in collected samples of rumen fluid, blood, faeces and urine were determined. P_i flow into the small intestine increased (p < 0.05) with P_i infusion. P_i net absorption tended to increase (p = 0.08) but proportion of absorbed P_i tended to decrease (p = 0.08). Urinary P_i excretion was negligible and did not affect P homoeostasis (p = 0.50). There was no change in plasma P_i concentration (p = 0.45) in response to P_i infusion. The increase in total faecal P excretion (p < 0.05) with increasing level of infused P_i was solely because of increased soluble faecal P_i (p < 0.05). It is suggested that at P overfeeding, intestinal P_i net absorption is saturable in dairy cows.     

奶牛阴道植入式电阻传感器与无线监测系统研究

针对人工监测奶牛发情费时、费力,仅依靠活动量和非接触式视频监测无法实现奶牛安静发情预警的问题,根据奶牛发情时阴道粘液生理特征变化,提出基于奶牛阴道电阻变化的奶牛发情监测方案。设计了由黄铜电阻探头、8爪防滑装置构成的奶牛阴道植入式电阻传感器,对阴道电阻值进行采集。借助2.4GHz的ZigBee网络开发了无线传输系统,将阴道电阻无线传送给协调器节点,协调器经由RS485总线传输到监控中心。开发了奶牛阴道电阻上位机实时监测系统,实现了奶牛阴道电阻的精确采集和远程实时监测。分别对植入式电阻传感器和监测系统进行了准确性、稳定性、可靠性及能量可用性试验,结果表明,植入式电阻传感器电阻测量探头体积小、安装方便,可测定1~1000Ω范围的电阻,测量精度在±2%以内,24h内电阻最大波动为2Ω;在450m2奶牛养殖区范围内,ZigBee网络数据发送成功率不低于98.5%;植入式电阻传感器终端节点在7.4V/6500mA·h锂电池能量供应下可连续工作38d。监测系统运行稳定,能够精确、可靠、实时地监测奶牛阴道电阻的变化,为奶牛发情程度和排卵时间的准确预测提供了一种新的监测方法。     

奶牛人工授精的优缺点和技术要点

奶牛人工授精技术加速了奶牛品种改良进程,实现了将优秀种公牛精液跨区域、超时限的利用共享,极大地促进了养牛业的发展。以奶牛人工授精应用现状为出发点,介绍了人工授精技术的优点和不足,最后结合自身工作经验,从发情鉴定、适时配种、精液解冻、精液检测、输精、精液保存和妊娠检测等技术要点进行概述,以期更好地促进奶牛人工授精技术的应用。     

冀中平原奶牛舍温热环境评价及温热参数与生理指标的相关性分析

试验旨在评价冀中平原地区四季奶牛舍的温热环境，并分析温热参数与奶牛生理指标的相关性。选择3栋不同建筑结构的奶牛舍，对各舍温湿度和奶牛的呼吸频率、直肠温度和体表温度等生理指标进行检测。结果显示，奶牛舍四季环境温湿度和温湿指数（THI）变化显著（P<0.05），其中夏季日均温最高，为28.59 ℃；冬季日均温最低，为1.55 ℃。奶牛夏季每天平均15.5 h遭受轻度热应激，6.0 h遭受中度热应激；冬季每天平均12.0 h遭受轻度冷应激。除冬季外，各季节不同牛舍的温度和THI均未表现出显著差异（P>0.05）。相比带矮墙或卷帘的棚舍，仅设顶子的棚舍夏季平均温度要高0.80~1.27 ℃，冬季低1.36~1.84 ℃。另外，夏季奶牛各项生理指标极显著高于其他季节（P<0.01），且夏季不同舍奶牛的呼吸频率和直肠温度均表现出显著差异（P<0.05），体表温度各季节差异均达显著水平（P<0.05）。从环境温湿参数与奶牛生理参数的相关性分析可看出，各项生理参数（呼吸频率、直肠温度和体表温度）与THI、环境温度均呈显著正相关（P<0.05），但与湿度未表现出显著相关性（P>0.05）。本研究可为奶牛舍环境的评价提供科学依据，并通过环境温热参数的检测推断奶牛生理状况，为应激的发生及预警提供数据。     

Associations between sole ulcer, white line disease and digital dermatitis and the milk yield of 1824 dairy cows on 30 dairy cow farms in England and Wales from February 2003-November 2004

The milk yields of 1824 cows were used to investigate the effect of lesion-specific causes of lameness, based on farmer treatment and diagnosis of lame cows, on milk yield. A three-level hierarchical model of repeated test day yields within cows within herds was used to investigate the impact of lesion-specific causes of lameness (sole ulcer, white line disease, digital dermatitis and other causes) on milk yield before and after treatment compared with unaffected cows. Cattle which developed sole ulcer (SU) and white line disease (WLD) were higher yielding cattle before they were diagnosed. Their milk production fell to below that of the mean of unaffected cows before diagnosis and remained low after diagnosis. In cattle which developed digital dermatitis (DD) there was no significant difference in milk yield before treatment and a slightly raised milk yield immediately after treatment. The estimated milk loss attributable to SU and WLD was approximately 570 and 370 kg, respectively. These results highlight that specific types of lameness vary by herds and within herds they are associated with higher yielding cattle. Consequently lesion-specific lameness reduction programmes targeting the cow and farm specific causes of lameness might be more effective than generic recommendations. They also highlight the importance of milk loss when estimating the economic impact of SU and WLD on the farms profitability.     

围产期奶牛氧化应激初步预警体系的建立

旨在通过对围产期奶牛能量负平衡指标与其他血液生化指标的分析,初步建立围产期奶牛氧化应激的预警体系。本试验以能量负平衡为判定标准,BHBA>1.2 mmoI/L,NEFA>0.4 mmoI/L,GLU<3 mmoI/L为发病组,BHBA<1.2 mmoI/L,NEFA<0.4 mmoI/L,GLU>3 mmoI/L为健康对照组,各采集围产期发病组和对照组各25头奶牛的血液并对血中能量代谢、矿物质代谢、微量元素代谢、氧化应激、免疫抑制指标进行独立样本T检验和spearman相关分析,并利用logistic二元逻辑回归预测疾病,最后利用ROC分析确立分界值和诊断效果。结果显示:发病组奶牛血液中的Ca、GSH-Px、CAT、Ve、Mg、Se、Cu水平小于健康组;发病组奶牛血液中的IL-1、IL-6、CRP、IL-2、HP、TNF-α的水平高于健康组,表明能量负平衡的奶牛机体存在氧化应激并伴有炎症和矿物质代谢紊乱。奶牛血液中的Ca、Mg、GSH-Px、CAT、Cu、Se、Ve与BHBA呈显著的负相关,IL-1、IL-2、IL-6、HP、TNF-α与BHBA呈显著的正相关;奶牛血液中的Ca、Mg、GSH-Px、CAT、Ve、Cu与NEFA呈显著的负相关,IL-2、HP、TNF-α与NEFA呈显著的正相关;奶牛血液中的Ca、GSH-Px与GLU呈显著的正相关,IL-6、HP与GLU呈显著的负相关。经回归分析确定Ca、Mg、GSH-Px、CAT、Cu、Se、Ve、IL-1、IL-2、IL-6、TNF-α、HP、BHBA 13项指标与围产期泌乳奶牛氧化应激相关,经ROC分析确立GSH-Px、CAT、Se、IL-6、IL-2、TNF-α、BHBA 7项指标可作为氧化应激发生的预警指标。结果表明,因此,能量负平衡、VE、Se缺乏、炎性因子增多和矿物质代谢紊乱是奶牛产后氧化应激发生的风险因素,但VE和Ca未成为氧化应激的预警指标。初步证实了围产期奶牛氧化应激发生的预警指标,为今后更有效的监控和预防奠定理论基础。     

植物黄酮在缓解奶牛热应激上的应用前景

奶牛是一种耐寒畏热的动物,当奶牛对环境温度的适应能力超过其阈值时就会产生热应激。热应激对奶牛的生产性能、抗氧化能力、免疫机制、内分泌和代谢产生不利影响,是阻碍奶牛业健康发展的一大问题。近年来,植物提取物作为一种兼具营养价值和保健价值的饲料添加剂被广泛应用。植物黄酮作为一种存在广泛的植物提取物,具有提高家畜生产性能和抗氧化能力、增强机体免疫力和抗炎能力、调节机体代谢等功效。因此,植物黄酮可以对症治疗奶牛热应激。本文将从热应激对奶牛生产性能、抗氧化能力、免疫机制、内分泌和代谢的影响以及近些年来将植物黄酮用于改善动物热应激的相关研究进行综述,以期为植物黄酮用于缓解奶牛热应激的深入研究提供理论支持。     

宿主防御肽在奶牛乳腺中的表达及应用

宿主防御肽是生物体内产生的一类具有抗菌作用的阳离子多肽,是生物体非特异性免疫功能的重要组成部分。宿主防御肽具有广谱、抗菌、耐热、无毒、不易产生耐药性等诸多特性,在畜牧生产中具有广阔的应用前景。本文主要对宿主防御肽在先天免疫系统中的作用、奶牛乳腺中的表达及乳房炎诊断与治疗应用的研究进展进行综述,为宿主防御肽作为抗生素替代品在畜牧生产中的研究与应用提供理论支持。     

过瘤胃豆粕替代常规豆粕对奶牛生产性能及血浆生化指标的影响

本试验旨在探究不同比例过瘤胃豆粕替代常规豆粕对奶牛生产性能及血浆生化指标的影响。选择胎次、体重、平均泌乳量和泌乳天数相近的健康荷斯坦奶牛60头,随机分为4组,每组15头。对照组饲喂基础饲粮,试验Ⅰ组用过瘤胃豆粕替代基础饲粮中12.5%的常规豆粕,试验Ⅱ组用过瘤胃豆粕替代基础饲粮中25.0%的常规豆粕,试验Ⅲ组用过瘤胃豆粕替代基础饲粮中50.0%的常规豆粕。预试期为15 d,正试期为45 d。结果表明:1)各试验组奶牛的干物质采食量均显著高于对照组(P<0.05),且随着过瘤胃豆粕替代比例的增加而升高,但各试验组之间均差异不显著(P>0.05)。2)各试验组奶牛的产奶量均显著高于对照组(P<0.05),且随着过瘤胃豆粕替代比例的增加而显著升高(P<0.05)。试验Ⅲ组奶牛的乳蛋白率显著高于试验Ⅱ组、试验Ⅰ组和对照组(P<0.05)。试验Ⅲ组和试验Ⅱ组奶牛的乳尿素氮含量显著高于试验Ⅰ组和对照组(P<0.05)。各组之间奶牛的乳脂率、乳糖率、非脂乳固体、乳体细胞数差异不显著(P>0.05)。3)各试验组血浆总蛋白和葡萄糖含量均显著高于对照组(P<0.05),且随着过瘤胃豆粕替代比例的增加而显著升高(P<0.05)。各组间血浆尿素氮含量及谷丙转氨酶、谷草转氨酶、碱性磷酸酶活性差异均不显著(P>0.05)。由此可见,在我国规模化奶牛场应用过瘤胃豆粕替代常规豆粕可以提高奶牛的干物质采食量,改善乳成分,同时改善奶牛机体代谢。在本试验条件下,以过瘤胃豆粕替代基础饲粮中50.0%的常规豆粕效果最佳。