酮病对泌乳早期乳牛体内代谢和内分泌的影响

随机选取某奶牛场10头患临床酮病乳牛和10头同期健康对照组乳牛，检测了2组乳牛血液10项指标，阐明了酮病对泌乳早期乳牛体内代谢和内分泌的影响。结果显示，酮病乳牛血糖浓度极显著降低（P〈O．01），血浆NEFA和BHBA的浓度明显增高（P〈O．01）；酮病乳牛血浆Ins、LP、NPY、E2的浓度和Ins／Gn比值均明显降低（P〈O．05），而血浆Gn浓度未明显升高，P4未明显降低（P〉0．05）。表明，酮病乳牛体内某些激素协调作用紊乱会妨碍酮病乳牛能量负平衡的缓解，并将对产后生殖机能产生不良影响。     

泌乳奶牛脂肪肝早期诊断的研究

为了寻找泌乳奶牛脂肪肝早期诊断方法,本研究从某千头奶牛场随机选取了30头乳酮阳性的奶牛,其中临床酮病牛10头,亚临床酮病牛20头,测定其肝脂含量以及血中代谢指标和肝功指标。试验结果表明,脂肪肝的奶牛存在能量负平衡现象,机体呈现高游离脂肪酸血症、高酮血症,肝脂浸润越重,能量代谢障碍越严重;乳酮阳性出现时间的早晚与脂肪肝的严重程度密切相关,乳酮阳性产后出现的越早,乳酮阳性越明显,肝脂浸润越重;随肝脂浸润程度的加重,肝功多个指标会出现异常,重度的脂肪肝会引发肝功能不全。本试验证明,酮粉法可以作为早期诊断奶牛脂肪肝的初选方法,肝功指标异常可作为诊断脂肪肝的辅助方法,两者结合可作为奶牛脂肪肝的实用、有效和准确的早期诊断方法,准确率可达80%。     

亚临床酮病对泌乳早期奶牛繁殖性能的影响

为探究围产期亚临床酮病与泌乳奶牛繁殖性能及卵泡发育之间的关系,本试验选择了黑龙江省某大型集约化牛场开展试验,根据产后血酮水平确定亚临床酮病组和健康组奶牛共80头,该牛场亚临床酮病发生率为71%;两组奶牛跟踪到产后50 d进行直肠检查和B超检查了解卵泡发育状况,并记录繁殖性能数据。结果显示:与健康组奶牛相比,亚临床酮病组奶牛产后首次发情天数延长10 d,产后60 d内发情次数少0.58次;产后50 d子宫复旧不全高15%,与亚临床酮病呈显著正相关(R^2=8.74);产后60 d卵泡直径小3 mm(P<0.05)。结论:该牛场奶牛亚临床酮病发病率较高,是引起奶牛产后繁殖障碍的风险因素,也是造成卵泡发育受阻的不良因素,会导致奶牛繁殖力下降。     

不同过瘤胃淀粉日粮对泌乳奶牛消化代谢的影响

以3头体况良好,安装有永久性瘤胃瘘管的泌乳前期奶牛为试验动物,在日粮精粗比为55∶45的前提条件下,采用3×3完全拉丁方试验设计,研究了3种不同过瘤胃淀粉日粮对泌乳奶牛消化代谢的影响。研究结果表明:3组不同日粮对营养物质的采食、排泄以及消化利用有着一定的规律性。3组不同日粮之间的采食量和消化率无明显差异(P>0.05);低过瘤胃淀粉日粮组的粪NDF排出量明显高于其他2组(P<0.05),其他2组之间差异不显著(P>0.05),粪中其他营养物质的排出量3组之间没有差异(P>0.05)。与对照组相比,其他2组均使尿氮排出量降低,其中高过瘤胃淀粉日粮组达到了显著水平(P<0.05),并且高过瘤胃淀粉日粮的氮沉积量和可消化氮转化为沉积氮的效率也明显高于其他2组(P<0.05),其他2组之间差异不显著。     

Effects of autogenous toxoid-bacterin in lactating cows with Staphylococcus aureus subclinical mastitis

To evaluate clinical effects of autogenous toxoid-bacterin treatment for Staphylococcus aureus subclinical mastitis in lactating cows, 22 cows which had at least one S. aureus infected quarter were selected from among cows at a S. aureus prevalent dairy farm. Eleven cows were injected with their own autogenous toxoid-bacterin and the others were maintained as non-injected control. In the toxoid-bacterin injected group, 27% of infected quarters were cured during the 12-week trial, compared to 5% in the control group. New intramammary infections with S. aureus were only detected in 3 quarters of the control group. Mean IgG antibody titer against S. aureus somatic antigens and alpha-toxin in serum and milk were significantly increased in the toxoid-bacterin injected group (p<0.05) and remained higher than those of the control group which showed no significant changes (p<0.05). In contrast to the control group, from 3 weeks after the second injection of the toxoid-bacterin injected group, mean S. aureus cfu/ml in milk samples from injected quarters with S. aureus was significantly decreased until the end of the study (p<0.05). In the toxoid-bacterin injected group, significant decreases of mean SCC were detected from milk samples from infected quarters with S. aureus from week 7 to week 10 (p<0.05). These data show that autogenous toxoid-bacterin treatment against S. aureus subclinical mastitis in lactating cows may increase the cure rate of the infections, reduce the severity of the infections and also prevent occurrence of the new infections.     

Oxidative stress indices in the erythrocytes from lactating cows after treatment for subclinical ketosis with antioxidant incorporated in the therapeutic regime

The present investigation was carried out to assess the erythrocytic oxidative stress indices such as lipid peroxides level and activities of antioxidant enzymes such as superoxide dismutase and catalase, and some hematological parameters after treatment of subclinically ketotic lactating cows with antioxidants, vitamin E and selenium, incorporated in conventional treatment regimen. The study was carried out using lactating cows reared in small dairy herds in and around Bhubaneswar. Out of 250 urine samples examined, 42 cows were diagnosed positive for subclinical ketosis with an overall incidence of 16.8%. Blood samples were collected on day 0 (before treatment) and treatment was initiated on day 1 and the second sampling was carried out on day 7. The hematological parameters improved significantly following treatment as compared to pre-treatment level (day 0). A significant (P < 0.05) improvement was observed on day 7 with respect to hemoglobin level (8.66 ± 0.23 vs. 9.12 ± 0.14 gm/dl) and packed cell volume (29.7 ± 0.56 vs. 31.1 ± 0.50%) in the group given routine treatment along with antioxidants. The comparison of mean lipid peroxides level before (day 0) and after treatment (day 7) revealed a significant difference in group I (routine treatment, P < 0.05) and group II (routine treatment plus antioxidants, P < 0.01). The maximum reduction in SOD activity was recorded in group II animals after treatment with conventional regimes along with supplemented antioxidants (1.29 ± 0.08 against 1.89 ± 0.15 units/ mg of Hb, P < 0.01). The mean value of SOD activity recorded in group III animals kept as non-treated positive control (PC) on day 7 (2.59 ± 0.14 units/mg of Hb) was significantly (P < 0.05) higher than the mean level recorded on day 0 (1.91 ± 0.31 units/mg of Hb). An almost similar trend was observed in erythrocytic catalase activity where there was a significant (P < 0.05) reduction in catalase activity in the group II (RT+A) but there was no significant increase in catalase activity in non-treated positive control (PC) animals.     

Plasma cholesterol levels and short-term adaptations of metabolism and milk production during feed restriction in early lactating dairy cows on pasture

Low plasma total cholesterol (TC) concentrations are characteristic during the negative energy balance in early lactating dairy cows. The objective was to investigate short-term effects of different TC concentrations during an aggravated energy deficiency through a 1-week concentrate withdrawal on adaptations of metabolism and milk production. Multiparous Holstein cows (n = 15) were investigated during 3 week beginning at 24 ± 7 DIM (mean ± SD). Cows were kept on pasture and received additional concentrate in experimental week 1 and 3, while in week 2, concentrate was withdrawn. Blood was sampled once and milk twice daily. Based on their average TC concentration during week 1 (prior to concentrate withdrawal), cows were retrospectively assigned into a high (H-Chol; n = 8, TC ≥ 3.36 mmol/L) and a low TC groups (L-Chol; n = 7, TC < 3.36 mmol/L). Concentrations of phospholipids and lipoproteins were higher in H-Chol compared to L-Chol throughout the study (p < 0.05). During concentrate withdrawal, milk yield, glucose and insulin concentrations decreased similarly in both groups, while milk fat, milk acetone and plasma BHB were higher in H-Chol compared to L-Chol (p < 0.05). Compared to initial values, plasma NEFA, TAG and VLDL increased in both groups within 2 days after concentrate withdrawal (p < 0.05). Concentrations of NEFA during week 2 were greater in L-Chol compared to H-Chol (p < 0.05). Despite reintroduction of concentrate, milk yield in H-Chol remained lower for two more days compared to week 1 (p < .05), whereas milk yield recovered immediately in L-Chol. Activity of aspartate aminotransferase was higher in H-Chol compared to L-Chol in week 2 (p < 0.05). Greater plasma TC concentrations were associated with a reduced increase of NEFA. Further research is warranted if TC concentrations are related to adipose tissue mobilization and fatty acid turnover.     

围产后期亚临床酮病对奶牛氧化应激、免疫功能和生产性能的影响

试验旨在研究围产后期SCK奶牛机体是否产生了氧化损伤和炎症反应。试验选取胎次、体重、上一胎次产奶量接近的产前(5±2) d的50头临床检查健康的荷斯坦奶牛为试验动物,根据产后10 d奶牛血液中BHBA含量是否在1.2～3.0 mM范围内,选取其中10头奶牛作为对照组(健康奶牛,n=10),10头奶牛作为SCK组(n=10)。分别于产后第10 d、20 d早晨饲喂前采集尾静脉血液用于测定SCK参数(BHBA、NEFA)、氧化参数、抗氧化参数、炎性因子、生产性能。结果表明,SCK组奶牛血液中SCK参数(BHBA、NEFA)、肝功能指标(AST、ALT、ALB、CHOL和TG)、氧化参数(ROS、MDA和H_2O_2)、炎性因子(TNF-α、IL-1β、IL-2、IL-8和IFN-γ)和SCC在产后10 d和20 d均显著高于对照组(P<0.05),且随着泌乳时间的延长,SCK组奶牛产后20 d时以上所述参数仍显著高于对照组产后10 d的奶牛(P<0.05);而GLU含量、IgG含量、抗氧化参数(TAC、SOD和GPX)、DMI和产奶量在产后10 d和20 d则显著低于对照组(P<0.05),且随着泌乳时间的延长,SCK组奶牛产后20 d时以上参数仍显著低于对照组产后10 d的奶牛(P<0.05)。综上所述,奶牛在产后20 d内机体产生了亚临床酮病,SCK奶牛肝脏均产生了不同程度的氧化损伤和炎性损伤,显著降低了奶牛的生产性能和健康状况。     

Effects of amino acids infused into the vein on ghrelin‐induced GH,insulin and glucagon secretion in lactating cows

To investigate the effects of amino acids on ghrelin‐induced growth hormone (GH), insulin and glucagon secretion in lactating dairy cattle, six Holstein cows were randomly assigned to two infusion treatments in a cross‐over design. Mixture solution of amino acids (AMI) or saline (CON) was continuously infused into the left side jugular vein via catheter for 4 h. At 2 h after the start of infusion, synthetic bovine ghrelin was single injected into the right side jugular vein through the catheter. Ghrelin injection immediately increased plasma GH, glucose and non‐esterified fatty acids (P < 0.05) with no difference between both treatments. Additionally, plasma insulin and glucagon concentrations were increased by ghrelin injection in both treatments. The peak value of plasma insulin concentration was greater in AMI compared with CON (P < 0.05). Plasma glucagon concentration showed no difference in the peak value reached at 5 min between both treatments, and then the plasma levels in AMI compared with CON showed sustained higher values (P < 0.05). After plasma glucose concentration reached the peak, the decline was greater in AMI compared with CON (P < 0.05). These results showed that the increased plasma amino acids may enhance ghrelin action which in turn enhances insulin and glucagon secretions in lactating cows.     

Effects of cold treatment and ketosis induced by starvation on interferon production in leukocytes of lactating cows.

The production of interferons in blood and milk leukocytes of three groups of cows was measured to determine the effect of 6-days cold treatment (-2 degrees to -8 degrees C) and/or starving. The first group (cold) was treated with low ambient temperature (-2 degrees C to -8 degrees C) 11 hours every day for 6 days, the second (cold and starved) was treated with low temperature and starved for 6 days. The third group (controls) was fed normally and kept in a barn at room temperature (18 degrees to 20 degrees C). The leukocytes of the control and the cold treated cows responded normally to interferon induction with Newcastle Disease Virus (NDV) and mitogens: phytohemagglutinin (PHA) and concanavalin A (ConA). The cows treated with low temperature and starved for 6 days developed biochemical blood changes of ketosis. Leukocytes of these cows with ketosis produced less interferon (p less than 0.05) than before starvation and less than leukocytes of the control cows and the cold treated cows. It can be assumed that ketosis caused by starving decreases the ability of a cow's leukocytes to produce interferons.     

Efficacy of controlled-release capsules containing monensin for the prevention of subclinical ketosis in pasture-fed dairy cows

AIMS: To determine the effectiveness of intra-rumenal controlled release capsules (CRC) containing 32?g of monensin administered pre-calving to reduce the cumulative incidence of subclinical ketosis (SCK) in mainly pasture-fed dairy cows.

METHODS: Cows (n=837) due to calve in the first 6 weeks of the spring calving period were enrolled from four commercial herds in the Waikato region of New Zealand in a blinded, randomised, negative-controlled field trial. Three weeks before the start of the calving period cows were randomly allocated to receive either no treatment (control) or a single CRC containing monensin and then blood sampled on two occasions, 7 days apart within 12 days following calving for measurement of concentrations of beta hydroxybutyrate (BHBA) in blood. Cows were diagnosed with SCK if the concentration of BHBA in blood in either of these samples was ≥1.2?mmol/L.

RESULTS: Fewer treated cows were diagnosed with SCK within 12 days post-calving than control cows (144/340 (42.4%) vs. 192/336 (57.1%); p<0.001). There was no interaction between treatment group and age, breed or herd of origin. From the final multivariable model it was estimated that treatment with CRC containing monensin reduced the absolute cumulative incidence of SCK by 17.9 (95% CI=9.2–25.8)% compared to no treatment.

CONCLUSIONS: Treatment with a CRC containing monensin >10 days prior to calving reduced the cumulative incidence of SCK of pasture-based dairy cows in commercial dairy herds within 12 days post-calving.

CLINICAL RELEVANCE: Administration pre-calving of an intra-rumenal bolus containing monensin can be considered as one of a range of management options for the control of SCK in early lactation.     

Chromium improves production and alters metabolism of early lactation cows in summer

Metabolic demands of early lactation introduce enormous challenges to dairy cows when coincided with environmental stresses. The objective of this study was to determine effects of a chromium (Cr) supplement on feed intake and blood indicators of nutrient metabolism in early lactation cows in summer. Fifteen Holstein cows at 38 ± 6 days in milk were grouped based on parity and randomly assigned to three supplemental doses of 0, 0.05 and 0.10 mg Cr/kg of BW^0.75. Cows received a basal mixed ration with a forage to concentrate ratio of 57.7:42.3, twice daily at 09:00 and 16:00 h for 9 weeks. The first 2 weeks were for adaptation, and the following 7 weeks were for weekly sampling and data collection. The Cr supplement (a Cr–methionine product with 10% Cr and 90% Met from a compound containing one atom of Cr and three molecules of Met) was mixed with 100 g of ground corn and top dressed with the morning feed. The average ambient temperature–humidity index was 77.7 units during the study. Dry matter intake increased from 21.8 to 24.2 and 23.7 kg/day when 0.05 and 0.10 mg Cr/kg BW^0.75 was provided respectively. Milk output of energy, fat, protein and total solids increased by providing Cr at 0.05 mg but not 0.10 mg/kg BW^0.75. Both doses of Cr increased milk protein content, but the higher Cr dose reduced feed efficiency compared with control. While rectal temperature and body condition score were unaffected, cows receiving 0.05 mg and not 0.10 mg Cr/kg BW^0.75 tended to have greater respiration rate than control cows. Blood insulin and non‐esterified fatty acids concentrations and the insulin to glucagon ratio decreased, and serum albumin increased when cows received 0.05 mg of Cr/kg BW^0.75. Blood glucose, glucagon, insulin‐like growth factor‐1, total protein, globulins, urea, BHBA, triglycerides, cholesterol, cortisol, progesterone, and high‐ and very low‐density lipoproteins were not affected. Therefore, supplemental Cr supply at 0.05 and 0.10 mg/kg BW^0.75 improved feed intake, only at 0.05 mg/kg BW^0.75 increased milk secretion, and mainly at 0.05 mg/kg BW^0.75 altered peripheral nutrient metabolism in early lactation Holstein cows under high ambient temperatures.     

Peripartum back fat thickness of multiparous Holstein-Friesian cows with displacement of the abomasum or ketosis

To establish a method to predict postpartum diseases using prepartum back fat thickness (BFT), the peripartum BFTs of 54 healthy multiparous cows before calving, which were diagnosed with postpartum displacement of the abomasum (DA), clinical ketosis or subclinical ketosis were compared with those of healthy cows from 8 weeks before the expected calving date to 8 weeks after calving. The peripartum BFTs of the cows with DA or clinical ketosis were significantly higher than those of healthy cows. The peripartum BFTs of the cows with subclinical ketosis were not significantly higher than those of the healthy cows.     

The effect of subclinical ketosis in dry cows on the composition of the colostrum and on health indicators in newborn calves

Subclinical ketosis of dry cows was studied as to its effect on the composition of colostrum and on the health condition and selected clinico-biochemical parameters in the new-born calves of these cows. The experimental group consisted of eight cows with ketonuria and their calves. The control group consisted of six cows without ketonuria and their new-born calves. Calves of both groups were reared in similar conditions. Colostrum samples were taken from the first milking and then from the milking 24 hours after parturition. The blood of the calves was sampled before the intake of colostrum and 24 hours after birth. The concentration of ketone bodies, particularly beta-hydroxybutyrate, was much higher in the colostrum of both groups of cows than in the blood (62.6 mg total ketone bodies per 1 litre of the first colostrum of the cows of the experimental group). The concentration of ketone bodies slightly increased after parturition. The cows with ketonuria secreted into colostrum a larger amount of oxidated ketone bodies. Colostrum quality was good in both groups. Decreased viability was not recorded during the clinical examination of the calves after birth. The level of total ketone bodies in the blood of pre-colostral calves in the experimental group was 10.4 mg per litre (a much lower concentration than in blood of their dams), and exhibited no appreciable change after taking in the colostrum. The blood of calves born to cows with ketonuria contained significantly higher amounts of oxidated ketone bodies. No correlation was demonstrated between the contents of ketone bodies in the blood of cows, in the blood of calves, and in the colostrum. The calves of the experimental group were found to have a significantly higher AST activity in plasma, as compared with the control group. Twenty-four hours after birth, the quantity of immunoglobulins in the blood serum was significantly lower in the calves of the experimental group. Thanks to good attendance and hygiene, the morbidity did not increase and no losses occurred.     

Incidence of subclinical ketosis in cows supplemented with a monensin controlled-release capsule in Holstein cattle, Florida, USA

The objective of this study was to determine the effect of a monensin controlled-release capsule on the proportion of cows with subclinical ketosis (SK). During July to August 2001, 300 cows dried-off 50-70 days before expected parturition were randomly assigned to either a treatment (n = 150, oral capsule, 335 mg/d of monesin for 95 d) or control group (no capsule, n = 150). At 14 days postpartum, a milk sample was obtained and evaluated for beta-hydroxybutyrate (BHBA) using a semi-quantitative ketone test strip. In a sub-sample of 50 cows per group a blood sample was taken and analyzed for BHBA using an ELISA kit. Milk BHBA > or = 200 micromol/L was used as the cut-off value for diagnosis of SK. The incidence of SK based on the milk test was statistically different between groups (P < or = 0.05) with a value of 26.6% for control and 14.5% for cows treated with monensin, respectively. Cows treated with monensin were 0.68 times less likely to give a positive result for milk BHBA than non-treated cows (0.53-0.80; 95% CI). Serum BHBA concentrations did not differ between groups (0.81 +/- 0.09 mmol/L versus 0.70 +/- 0.07 mmol/L for controls and treated, respectively; P > 0.05). However, for each incremental increase in serum BHBA of 0.1 mmol/L occurrence of SK increased 52% (OR = 1.52; 1.21-1.91; 95% CI).     

Effects of Fusarium mycotoxins in rations with different concentrate proportions on serum haptoglobin and hepatocellular integrity in lactating dairy cows

It was hypothesized that long‐term intake of a diet contaminated with deoxynivalenol (DON) and differing in the proportion of concentrate might affect hepatocellular integrity and function as well as biomarkers of systemic inflammation in lactating dairy cows. In Period 1 (11 weeks), 26 lactating German Holstein cows (13 primiparous and 13 pluriparous, 31 days in milk, 522 kg body weight, on average) were divided into two groups and fed diets (50% concentrate) with (MYC, n = 12; on average 5.3 mg DON/kg DM) or without (CON, n = 14) DON contaminations. In Period 2 (16 weeks), each group was further divided into two groups to test whether elevated concentrate proportion as additional burden might enhance the toxicity of DON. The cows in MYC60 (n = 6; 4.6 mg DON/kg DM) and CON60 (n = 7) received the diet with 60% concentrate, while cows in MYC30 (n = 6; 4.4 mg DON/kg DM) and CON30 (n = 7) received the diet with 30% concentrate. Blood samples were taken in biweekly intervals for activities of aspartate amino transferase (AST), glutamate dehydrogenase (GLDH) and gamma‐glutamyl transferase as well as for concentration of total bilirubin and haptoglobin. Biopsies from liver were collected in week 27 for morphological analyses. No DON effect was found for the variables assessed in blood. The diet with 60% concentrate led to higher activities of AST and GLDH in Period 2. No morphological change was found by both light and electron microscopic analyses of liver samples. Results indicated that long‐term intake of DON‐contaminated diet over 27 weeks led to neither relevant damages of hepatocytes nor systemic inflammatory responses in lactating dairy cows, even if the dietary concentrate proportion was increased to 60%.     

泌乳早期发情和乏情奶牛机体代谢和生殖机能的变化

在某一集约化牛场,随机选取奶牛30头,在奶牛产后发情期(50～90 d)内根据奶牛是否发情将奶牛分为发情组和乏情组。通过对试验奶牛血液生化指标(Glu、BHBA、NEFA)、内分泌指标(FSH、LH、LP、E2、P4)等进行调查和检测。结果显示:当奶牛发情时,机体血浆Glu、FSH、LH、E2和LP浓度高,血浆NEFA、P4浓度低,但乏情时正好相反。当奶牛发情时,血浆leptin与LH、E2呈显著正相关,与P4呈显著负相关,但乏情奶牛未呈现相关性。这些结果提示奶牛乏情与机体能量代谢状况和Ins、Gn、E2、P4、Lp分泌少有关。能量平衡能促进奶牛产后发情,与机体高水平血糖、Lp、FSH、LH、E2和低水平P4、NEFA有关。LP是奶牛泌乳早期发情的一个重要调控因子,在奶牛产后能量平衡、生产性能和繁殖性能之间起到一个平衡纽带的作用。     

Effects of stocking density on oxidative stress status and mammary gland permeability in early lactating dairy cows

The current study was conducted to investigate the effect of stocking density (SD) on oxidative stress status and mammary gland permeability in early lactating dairy cows. Thirty‐two dairy cows were allocated into 16 blocks, basing on parity, previous milk yield, and body weight, and were then randomly assigned into one of the two treatments as follows: 75% (75SD) and 100% (100SD) SD. The cows were fed with same diet throughout the 8‐week experimental period. The milk yield and milk sample were collected on two consecutive days during the 8‐week experimental period weekly. Plasma samples were collected on fourth and eighth experimental weeks. Raw, energy‐corrected, and 4% fat‐corrected milk yield were significantly higher in 75SD‐cows than that of 100SD‐animals, respectively. The milk somatic cell count was lower in 75SD‐cows than that of 100SD‐animals. The levels of Na⁺, Na⁺/K⁺, bovine serum albumin and plasmin were lower in 75SD‐cows than those of 100SD‐cattle, respectively. The 75SD‐cows had reduced insulin and insulin/glucagon levels but higher prolactin and growth hormone concentrations, compared with those of 100SD‐animals, respectively. In conclusion, compared with low SD‐animals, early lactating cows with higher SD had higher oxidative stress status, which further led to a greater mammary gland permeability.