我国气候因素的变化对奶牛生产的影响

在分析我国气候因素变化的基础上,着重阐述了气候因子对我国奶牛采食,饲料利用率,产奶量和乳成分,奶牛的繁殖力,日增重及发病率等生产性能的影响。结果表明,高温高湿是奶牛生产的主要环境因子。作者不提出了控制奶牛环境的若干措施。     

Concordance between Results of Medium-term Liver Carcinogenesis Bioassays and Long-term Findings for Carcinogenic 2-Nitropropane and Non-carcinogenic1-Nitropropane in F344 Rats

This study was conducted to determine the concordance of results for a pair of structural isomers, 2-nitropropane (2-NP) and 1-nitropropane (1-NP), using the rat medium-term liver carcinogenesis bioassay (Ito test) and previously published long-term carcinogenicity tests. Male F344 rats were given a single intraperitoneal injection of DEN (200 mg/kg b.w.) to initiate hepatocarcinogenesis. After 2 weeks, they received per os 0, 0.8, 4 or 20 mg/kg/day of 2-NP or 1-NP six times a week and were subjected to two-thirds partial hepatectomy at week 3. Non-initiated groups receiving 0 or 20 mg/kg/day were also included. The animals were sacrificed for quantitative analysis of GST-P-positive foci at week 8. With the highest dose of 2-NP, significantly increased numbers and areas of GST-P-positive foci were demonstrated as compared with the respective control but were not noted with 1-NP. In the non-DEN-initiated groups, many small GST-P-positive foci of less than 0.2 mm in diameter were also induced in the rats treated with 2-NP at 20 mg/kg/day but were lacking with 1-NP. These results strongly support that 2-NP is a complete hepatocarcinogen with a potent initiation activity, whereas 1-NP is not.     

中药复方对低温条件下锦江黄牛生产性能及血清抗氧化指标的影响

本试验选择5月龄,150 kg左右的锦江黄牛15头,分为低温对照组、中药添加剂1组和中药添加剂2组三个组别,每组5头,研究中药复方添加剂对冬季饲养锦江黄牛的抗冷应激作用。试验为期30 d。结果表明:与低温对照组相比,中药1组日增重明显升高,料重比显著下降,血清MDA含量下降59.26%(P<0.01);中药2组日增重和料重比与低温对照组差异不显著(P>0.05),血清MDA含量下降了81.48%(P<0.01);两个中药添加组肉牛的血清SOD活性与低温对照组均无显著差异(P>0.05)。以上结果表明,饲粮中添加中药复方1后可有效缓解冬季饲养的锦江黄牛冷应激反应,提高其血清抗氧化能力,改善生产性能,且其效果优于中药复方2。     

微生物发酵饲料对肉牛免疫机能的影响

试验旨在研究微生物发酵饲料对肉牛免疫机能的影响。选择90头月龄相近、体型结构相似、体重(373.4~425.3) kg的健康西杂牛,采用随机区组试验设计,将90头牛分为3组,每组5个重复,每个重复6头牛。对照组饲喂基础精料日粮,试验Ⅰ、Ⅱ组分别用25%和40%微生物发酵饲料替代基础精料,各组每头牛每天饲喂相同重量的精料(4 kg)和玉米秸秆颗粒(2.7 kg),酒糟自由采食,拴系饲喂,自由饮水;预试期10 d,正试期48 d。结果显示,与对照组相比,2个试验组中血清总蛋白、白蛋白、免疫球蛋白A、G、M浓度显著(P＜0.05)或极显著(P＜0.01)提高,谷草转氨酶、谷丙转氨酶活性及丙二醛浓度均显著(P＜0.05)或极显著(P＜0.01)下降;且总抗氧化能力和总超氧化物歧化酶的活性极显著增强(P＜0.01)。提示,利用微生物发酵饲料能提高肉牛免疫力。     

Clinical and pathologic features of acute bovine liver disease in Australia

Acute bovine liver disease (ABLD) is a sporadic hepatic disease affecting cattle in southern Australia, characterized histologically by striking periportal hepatocellular necrosis. The cause of ABLD is unknown; however, the seasonality and acute presentation of outbreaks suggest mycotoxin involvement. We describe here the clinical and pathologic findings of ABLD in 45 naturally affected cattle from 13 outbreaks occurring from 2010 to 2019 in Victoria, Australia. Outbreaks occurred in herds located along the southern coastal plain of Victoria and were observed most frequently in lactating dairy cattle. Clinical signs commonly included a combination of mild photosensitization, progressive neurologic signs, and hypogalactia, which preceded death by ≤ 48 h. All affected animals had marked elevations in activities of glutamate dehydrogenase, aspartate aminotransferase, and gamma-glutamyl transferase. At autopsy, the most common lesions were serosal petechiae and/or gastrointestinal hemorrhage, and hepatomegaly with a pronounced hepatic reticular pattern. The principal histologic lesion was widespread—severe periportal hepatocellular coagulative necrosis and erythrocyte pooling—which often extended to massive necrosis. Lesions in other organs were uncommon. Our study of ABLD suggests involvement of a potent hepatotoxin that is either directly cytopathic or requires bioactivation by periportal-specific enzymes.     

Effects of feeding different levels of concentrate on growth and carcass characteristics in younger Japanese Black cattle

The effects of a higher concentrate feed during the raising period on the growth and carcass of Japanese Black cattle being fattened at a younger age were investigated using three pairs of artificially bred identical twins and three pairs of full‐sibs. The animals were fed the concentrate at 2.4%/day (2.4% group) and 1.2%/day (1.2% group) comparative bodyweight (BW) during the raising period. The BW and subcutaneous fat thickness were measured every month using ultrasonic equipment. The animals were slaughtered at the age of 24 months. The BW of the 2.4% group from the age of 6–10 months appeared to be higher than that of the 1.2% group (P < 0.1). The subcutaneous fat of the 2.4% group from the age of 7–11 months was thicker than that of the 1.2% group (P < 0.1). After those ages, the BW and subcutaneous fat of the two groups did not differ and there was no difference in the carcass characteristics between the two groups. Using a higher concentrate feed during the raising period for younger fattening of Japanese Black cattle influenced growth from the late half of the raising period to the early part of the fattening period.     

关于平凉红牛分段式目标育肥效果的研究

[目的]研究不同育肥模式对"平凉红牛"产肉性能的影响,探寻适宜于当地的"平凉红牛"分段式目标育肥模式。[方法]将"平凉红牛"公牛按不同初始体重和不同育肥阶段分为3组,即A组(360～630kg)、B组(315～585kg)、C组(270～540kg),测定不同组别试验牛的平均日增重、屠宰率、净肉率、优质高档肉块产量及比例等。[结果]育肥期平均日增重,3组间无显著差异(P0.05),但以B组最高;屠宰率、净肉率,3组间差异不显著(P0.05),但以A组最高;优质肉块总重、高档肉块总重占宰前活重的比例均以A组最高。[结论]综合考虑育肥期日增重、产肉性能、优质高档肉块比例、经济效益等因素,适宜于平凉当地的育肥模式为315～585kg。     

Nitric oxide impacts bovine sperm capacitation in a cGMP‐dependent and cGMP‐independent manner

We aimed to elucidate whether NO acts in in vitro sperm capacitation in bovine via cGMP/PKG1 pathway. For this, cryopreserved bovine sperm were capacitated in vitro with 20 µg/ml heparin (Control) plus treatments: 1 mM L‐arginine (L‐arg, NO precursor), 50 µM Rp‐8‐Bromo‐β‐phenyl‐1,N²‐ethenoguanosine‐3′,5′‐cyclic monophosphorothioate (Rp‐8‐Br‐cGMPS, selective inhibitor of the binding site for cGMP in PKG1), 1 mM 2‐Phenyl‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl 3‐oxide (PTIO, NO scavenger), and the combinations of L‐arg + RP‐8‐Br‐cGMPS and L‐arg + PTIO. Sperm motility and vigour were determined by phase‐contrast microscopy, capacitation status by chlortetracycline staining, and the intracellular concentration of cGMP was measured by ELISA. Data were subjected to analysis of variance and means compared with SNK test at 5% probability. Motility and vigour were lower in sperm treated with PTIO when compared to Control and other treatments (p < .05). The L‐arg treatment showed the highest percentage of capacitated sperm when compared to the Control and other treatments (Rp‐8‐Br‐cGMPS, L‐arg + Rp‐8‐Br‐cGMPS and PTIO) (69.8 ± 3.4%, 51.2 ± 3.0, 51.1 ± 2.1, 51.2 ± 3.0 and 45.5 ± 2.7, respectively) (p < .05). The capacitation ratio (%) was lower in treatments with Rp‐8‐Br‐cGMPS, L‐arg + Rp‐8‐Br‐cGMPS and PTIO, respectively (p < .05). Lastly, cGMP concentration (pmol/ml) was lower in PTIO and L‐arg + PTIO (1.3 ± 0.3 and 1.6 ± 0.4) and was higher in Rp‐8‐Br‐cGMPS and L‐arg + Rp‐8‐Br‐cGMPS (3.7 ± 0.4 and 4.0 ± 0.5) treatments. We showed that during in vitro capacitation of cattle: (a) NO influences sperm motility and vigour; (b) NO is associated with cGMP synthesis through two independent pathways and (c) the cGMP/PKG1 pathway has a partial role in sperm capacitation and does not involve the L‐arg/NO.     

Contribution of insulin to the ascorbate recycling system in the chicken liver

The effect of insulin on the ascorbate recycling system in the chicken liver was examined. First, insulin was injected subcutaneously into the chicken, and liver glutathione‐dependent dehydroascorbate reductase (GSH‐DHAR) activity was determined. Insulin increased liver GSH‐DHAR activity, but did not affect plasma and liver ascorbate concentration. Dehydroascorbate increased plasma and liver ascorbate levels, and liver GSH‐DHAR activity. However, distinct changes in plasma insulin level were not observed by dehydroascorbate injection. In addition, reduction of external dehydroascorbate in cultured chicken hepatocytes could not be observed in an insulin‐deprived culture, although the cells reduced external dehydroascorbate in a serum‐free culture with insulin. We concluded that insulin affects the ascorbate recycling system as an essential factor in the chicken liver.