乳牛产后期生理性免疫状态的研究

为了研究乳牛在产后期的生理性免疫状态，检测了产后期乳牛淋巴细胞及其亚群数量和淋巴细胞增殖活化功能及其变化。结果发现，乳牛淋巴细胞及其亚群数量和淋巴细胞增殖活化功能在分娩后第1d最低，然后表现出缓慢上升的总体趋势。CD3细胞数在产后第15d低于产后第1d，到产后第30d时达到最高值；CD4细胞数一直多于CD8细胞数；CD21细胞数在产后第15d时达到最高值，以后缓慢下降；淋巴细胞的增殖活化能力在产后第30d最高，未观察到淋巴细胞有明显的凋亡和增生现象。结果表明，乳牛免疫状态在产后第1d最低，以后逐渐升高，第15d时细胞免疫最低而体液免疫最高，第30d时细胞免疫最强。     

Relationship between overfeeding and overconditioning in the dry period and the problems of high producing dairy cows during the postparturient period

Summary

In dairy cows, overfeeding during the dry period leads to overcondition at calving and to depression of appetite after calving. As a consequence, at calving overconditioned high‐producing dairy cows inevitably go into a more severe negative energy balance (NEB) postpartum than cows that have a normal appetite. During the period of NEB, the energy requirements of the cow are satisfied by lipolysis and proteolysis. Lipolysis results in an increased concentration of non esterified fatty acids (NEFA) in the blood. In the liver, these NEFA are predominantly esterified to triacylglycerols (TAG) that are secreted in very low density lipoproteins (VLDL). In early lactation in cows with a severe NEB, the capacity of the liver to maintain the export of the TAG in the form of VLDL in balance with the hepatic TAG production is not always adequate. As a result, the excess amount of TAG accumulates in the liver, leading to fatty infiltration of the liver (hepatic lipidosis or fatty liver). The NEB and/or fatty liver postpartum are frequently associated with postparturient problems. In general, a severe NEB induces changes in biochemical, endocrinological, and metabolic pathways that are responsible for production, maintenance of health, and reproduction of the postparturient dairy cow. These changes include a decrease in blood glucose and insulin concentrations, and an increase in blood NEFA concentrations. High NEFA concentrations caused by intensive lipolysis are accompanied by impairment of the immune system, making the cows more vulnerable to infections. Metabolic diseases such as ketosis, milk fever, and displaced abomasum are related to overcondition at calving. The changes in biochemical, endocrinological, and metabolic pathways are associated with delay of the first visible signs of oestrus, an increase in the interval from calving to first ovulation, a decrease in conception rate, and a prolonged calving interval. It is possible that the increased blood NEFA concentration directly impairs ovarian function.     

Feed intake, lactation performance, blood metabolites and fertility in early lactation dairy cows grazing a timothy pasture

The present study was conducted to investigate feed intake, milk yield, milk composition, blood metabolites and fertility in early lactation dairy cows grazing a timothy pasture. Fourteen multiparous Holstein cows that calved between 20 May and 19 July were used over a 3‐year period. The stocking rate was 3.6–4.3 cow/ha. Concentrates were fed separately at 9.5–11.5 kg/day per cow (dry matter basis) from 1 to 13 weeks postparturition. Herbage intake was estimated using chromium oxide as an indigestible marker. The mean contents of crude protein, total digestible nutrients and neutral detergent fiber of pasture during the 3‐year study period were 22.3%, 71.8% and 51.7%, and those of total diet were 18.9%, 77.3% and 40.3%, respectively. The mean herbage dry matter intake was 13.0 kg/day from 2 to 13 weeks postparturition during the study, total dry matter intake was 23.7 kg/day, the total digestible nutrients sufficiency rate was 105%, milk yield was 39.7 kg/day, and milk fat percentage was 3.30%. The decrease in bodyweight postparturition was slight. Urea nitrogen concentrations in serum were below 18.3 mg/dL. The mean days to first estrus and days open were 36 and 104 days, respectively. These results indicate that energy deficiency, decrease in bodyweight and fertility in early lactation barely occur when high producing dairy cows are fed enough grazing grass and suitable concentrates.     

Effect of fat supplementation during transition period on plasma leptin and non‐esterified fatty acid concentrations in Holstein cows

The objective of this experiment was to investigate the effect of fat supplementation during the transition period on pre and postpartum body weight (BW), body condition score (BCS), non‐esterified fatty acids (NEFA), glucose and leptin concentrations in Holstein cows. Holstein cows (n = 15) received a low fat diet (LF; 1.61 Mcal net energy for lactation (NEL)/kg of dry matter [DM]), moderate fat diet (MF; 1.68 Mcal NEL/kg DM) or a high fat diet (HF; 1.74 Mcal NEL/kg DM) for 4 weeks prior to calving. All cows were fed similar lactation diets ad libitum (1.74 Mcal NEL/kg DM) for 30 days after calving. Increasing diet energy density during transition period had no effect on prepartum DMI, BCS, BW, glucose and NEFA concentrations (P > 0.05); but leptin concentrations and energy balance (EB) were affected by treatments (P < 0.05). Animals fed HF had less plasma leptin prepartum. After parturition, BW, milk production, milk fat, protein, urea nitrogen and plasma glucose concentrations were affected by prepartum diets (P < 0.05). Fat supplementation prepartum did not affect postpartum NEFA. In conclusion, prepartum fat supplementation decreased leptin concentration prepartum.     

Characterization of ruminal dynamics in Holstein dairy cows during the periparturient period

We used four pregnant Holstein cows to delineate ruminal adaptations as cows transitioned from one lactation to the next. Cows were fed typical diets through far-off and close-up dry periods and lactation. We measured ruminal characteristics on day 72 (late lactation), 51 (far-off dry), 23 and 9 (close-up dry) prepartum and on days 6, 20, 34, 48, 62, 76 and 90 postpartum (early lactation). Measurements included: ruminal fill (weight of actual contents), ruminal capacity (volume of rumen when fully filled), digestibilities and ruminal passage rates. Ruminal capacity tended to increase linearly during early lactation but was stable during dry and transition periods. Both total and liquid fill decreased linearly during the dry period, increased across parturition, and increased linearly through early lactation. Dry matter fill decreased as cows were fed the close-up diet at day 23 prepartum then increased near parturition and continued to increase across early lactation. Solid passage rate was greatest when cows were fed the close-up diet, and decreased throughout the transition period. In lactation, solid passage rate responded quadratically with peak at day 48 followed by decreases through day 90 postpartum. Liquid passage increased linearly across the transition period. Total tract organic matter digestibilities increased linearly over the dry period with significant increases prior to or immediately after parturition, then they remained relatively stable over early lactation until they increased at day 90. Fibre digestibilities demonstrated quadratic responses over early lactation, being higher on day 6 and day 90 than at other times. Starch digestibilities decreased linearly across both the dry and transition periods with decreases in lactation until day 62 followed by increases until day 90. High producing lactating dairy cows go through a multitude of ruminal adaptations, in terms of digestion, passage, capacity and fill, as they transition from one lactation to the next.     

八珍汤对乳牛产后免疫状态的影响

为了探索提高乳牛产后期免疫状态的新方法，对试验乳牛分4组（产前第30d至产前第1d灌喂组、产前第15d至产后第15d灌喂组、产后第1d至第30d灌喂组、不灌喂中药对照组）灌喂中药八珍汤，检测产后期淋巴细胞及其亚群数量和淋巴细胞增殖活化功能。结果发现，产前组CD3细胞数量在产后第1d升高；产前产后组CD3、CD4和CD8细胞数量在产后第1d和第15d升高；产后组CD3细胞数量在产后第15d和第30d升高，CD4细胞数量也在产后第30d升高。淋巴细胞对ConA的反应能力，产前产后组在产后第1～30d明显提高，产后组在产后第15d和第30d明显提高。各组乳牛产后期CD21细胞数量的变化相近。结果表明，从产前第15d开始到产后第15d每日喂八珍汤，能明显提高乳牛产后期T细胞及其亚群数量和增加淋巴细胞增殖活化功能，而对B细胞数量增加的作用不明显。     

Effect of nutrient levels during the far‐off period on postpartum productivity in dairy cows

The present study aimed to determine the effects of differing nutrient levels during the far‐off period on postpartum metabolism and milk production in lactating cows. Twenty‐six multiparous cows were assigned to three dietary treatments in the far‐off period: a low‐energy diet (L, n = 9, 80% intake of the total digestible nutrients requirement), a moderate‐energy diet (M, n = 8, 105%) and a high‐energy diet (H, n = 9, 130%). During the close‐up period, all cows were provided with 105% intake. After parturition, all cows were fed a lactation diet. The BCS recovery was slow, and low milk yield was found in the H group. In the L group, BCS recovery was favorable after parturition, and lactation persistence was increased. The L group had low rumen endotoxin activity and a high initial ovulation rate after parturition. These findings indicate that a high‐energy diet during the far‐off period has a deleterious effect on milk production. In contrast, the restricted diet in the far‐off period increased adaptability with respect to peri‐parturition metabolic changes, improved the post‐parturition nutritional state, and increased milk production. Furthermore, it suggests that the nutrient levels in the far‐off period affect rumen endotoxin activity and reproductive function after parturition.     

Body phosphorus mobilization and deposition during lactation in dairy cows

Dairy cow bone phosphorus (P) mobilization and deposition and their influence on P requirements were studied over the lactation cycle. Thirty Holsteins received a common diet during the dry period and one of the following three dietary treatments that varied in P percentage during the subsequent lactation (44 weeks): (i) 0.36 throughout (constant P, 0.36‐0.36‐0.36), (ii) 0.36 for 30 weeks then 0.29 for 14 weeks (P changed once, 0.36‐0.36‐0.29), and (iii) 0.43 for 10 weeks, 0.36 for 20 weeks, and 0.29 for 14 weeks (P changed twice, 0.43‐0.36‐0.29). Six P balance studies were conducted during the experiment, including one during the dry period and five along lactation, based on P intake, faecal P, urinary P and milk P, when appropriate. Blood samples were taken during balance to analyse bone formation (osteocalcin) and resorption (pyridinoline) marker concentrations and rib biopsies performed to determine bone P content. Phosphorus balance was negative during weeks ?4 to ?1 relative to lactation for all groups and remained negative for cows fed 0.36% P during weeks 1–5, but showed a positive value for cows that received 0.43% P. The balance was close to zero for all groups at weeks 19–23 and showed a clear retention during weeks 38–42; by the end of lactation, cows re‐stored most of the P mobilized earlier. The pattern in P balance was consistent with changes in blood bone metabolism marker concentrations, rib bone P content, and faecal and urinary P concentrations over the experiment, indicating that cows, irrespective of the dietary P treatments received, mobilized P from bone during the late dry period when fed a low‐Ca diet and early lactation, and re‐stored P in late lactation. This dynamic of P metabolism can have important implications for dietary P requirements and ration formulations.     

Metagenomic profiles of the rumen microbiota during the transition period in low‐yield and high‐yield dairy cows

We investigated potential relationships between rumen microbiota and milk production in dairy cows during the transition period. Twelve dairy cows were divided into a low‐yield (LY) or high‐yield (HY) group based on their milk yield. Rumen samples were taken from dairy cows at 3 weeks before parturition, and at 4, 8, and 12 weeks after parturition. 16S rDNA‐based metagenomic analysis showed that diversities of rumen microbiota in both groups were similar and the number of operational taxonomic units (OTUs) was lower in the postpartum than prepartum period in both groups. The abundance of Bacteroidetes and ratio of Bacteroidetes:Firmicutes was higher in the HY than the LY group. OTUs assigned to Prevotella bryantii, Fibrobacter succinogenes, Ruminococcus albus, Butyrivibrio fibrisolvens, and Succinivibrio sp. were abundant in the HY group. These OTUs were significantly related to the propionate molar proportion of rumen fluids in the HY group. OTUs assigned to Lachnospiraceae, Bifidobacterium sp. and Saccharofermentans were dominant in the LY group. Predictive functional profiling revealed that abundance of gene families involved in amino acid and vitamin metabolism was higher in the HY than the LY group. These results suggest that the community structure and fermentation products of rumen microbiota could be associated with milk production of dairy cows.     

仙人掌果实对奶牛泌乳性能、氮利用及采食行为的影响

本研究评估了仙人掌果实与不同粗饲料结合对荷斯坦奶牛采食量、营养物质消化率、氮平衡、摄食行为和泌乳性能的影响。试验选择泌乳期为(72±11)d的8头奶牛,采用4×4拉丁试验设计,共4种试验日粮:T1组为75%青贮高粱组,T2组为75%象草组,T3组为37.5%青贮高粱+37.5%仙人掌果实,T4组为37.5%象草+37.5%仙人掌果实。结果:青贮高粱组干物质摄入量最高(P<0.05)。不同日粮组干物质、粗蛋白质、粗脂肪、非纤维碳水化合物和总可消化养分摄入量存在显著差异(P<0.05)。仙人掌果实组较青贮高粱和象草组日饮水量降低44.52%(P<0.05)。与象草组、象草+仙人掌果实组相比,青贮高粱组、青贮高粱+仙人掌果实组氮平衡降低59.71%和27.49%(P<0.05)。结论:奶牛日粮中以仙人掌果实与青贮高粱或象草的组合并没有改变荷斯坦奶牛的产奶量,但降低了营养物质和水分摄入量,同时提高了养分消化率。     

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。     

丙酸钙对泌乳早期奶牛泌乳性能和代谢产物的影响

选用32头经产奶牛,根据泌乳期、上个泌乳期305 d产奶量和预产期,采用随机区组设计分为4组,对照组饲喂基础日粮,处理1、2、3组分别在基础日粮基础上添加丙酸钙100、200、300 g/d.结果显示,日粮添加丙酸钙对奶牛的采食量、乳脂率、乳蛋白率、乳糖率和乳干物质率无显著影响,200、300 g/d组产奶量和饲料转化效率显著高于对照组(P<0.05).200、300 g/d组血浆葡萄糖和胰岛素浓度显著高于对照组(P<0.05),而血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05);200、300 g/d组尿酮浓度显著低于对照组和100 g/d组(P<0.05).试验结果表明,丙酸钙适宜添加量为200 g/d.     

不同淀粉水平日粮中添加酵母培养物对奶牛干物质采食量和瘤胃发酵功能的影响

文章旨在研究不同淀粉水平日粮中添加酵母培养物对奶牛生产性能和瘤胃发酵功能的影响。试验选择16头荷斯坦奶牛,随机分为4组,每组4个重复,每个重复1头牛。试验日粮采用2×2多因素方差设计,两个淀粉水平(23%和29%),两个酵母培养物水平(0和25 g/d),试验共进行28 d。结果显示:日粮添加酵母培养物后显著提高了产奶量、3.5%标准乳、能量校正奶(P <0.05)。无论是在低或高淀粉水平日粮中添加酵母培养物均显著提高乳脂含量(P <0.05)。高淀粉水平日粮或添加酵母培养物显著提高了乳蛋白含量(P <0.05)。高淀粉水平日粮中添加酵母培养物较对照组显著降低了血浆结合珠蛋白的含量(P <0.05)。高淀粉水平日粮中添加酵母培养无较对照组显著降低了淀粉表观消化率(P <0.05),低淀粉水平日粮组显著提高了乙酸含量(P <0.05)。高淀粉水平日粮组显著提高了瘤胃乳酸含量(P <0.05)。高淀粉水平日粮组较低淀粉水平组显著降低了氮沉积量(P <0.05),添加酵母培养物使氮沉积量显著升高(P <0.05)。高淀粉水平日粮中添加酵母培养物组氮摄入量和乳氮含量最高(P <0.05)。结论 :在本试验条件下,高淀粉水平日粮中添加15 g/d酵母培养物可以降低奶牛代谢紊乱症的发生,提高纤维消化率及微生物蛋白的产量,进而改善泌乳性能。     

Effects of body condition at far-off dry period on blood biochemistry,liver triacylglycerol and muscular monocarboxylate transporter-1 mRNA expression in tropical Holstein dairy cows during peripartum period

Effects of body condition score (BCS) at far-off dry period on blood biochemistry, liver triacylglycerol, and muscular monocarboxylate transporter-1 mRNA expression in tropical Holstein dairy cows during peripartum period were studied. Eight dry cows were divided into two groups of four cows based on their BCS at 8 weeks prepartum: high BCS (HBS) and low BCS (LBS). Blood samples were collected weekly from 8 weeks before expected calving date until 8 weeks postpartum for determination of serum glucose, non-esterified fatty acid (NEFA), and β-hydroxybutyrate (BHBA). Muscle and liver samples were biopsied at 2 weeks before expected calving date and at 2 weeks postpartum for determination of muscular monocarboxylate transporter-1 (MCT-1) mRNA expression and liver triacylglycerol concentrations. Decreased BCS and elevated serum NEFA and BHBA indicated that LBS cows entered to the NEB period earlier than did HBS cows. LBS cows showed lower liver TAG and higher muscular MCT-1 mRNA expression than did HBS cows. The MCT-1 mRNA expression at 2 weeks prepartum was negatively correlated with BCSs at 2–3 weeks prepartum and at 1–2 weeks postpartum. In conclusion, LBS cows most likely adapted to NEB by upregulation of muscular MCT-1 expression and had lower NEB consequences during postpartum period.     

Relationship among blood indicators of lipomobilization and hepatic function during early lactation in high-yielding dairy cows

Blood indicators are used as a tool to diagnose metabolic disorders. The present work was conducted to study the relationships among blood indicators of lipomobilization and hepatic function in high-yielding dairy cows. Two groups of Holstein cows were studied: 27 early lactation cows and 14 mid lactation cows from four different herds with similar husbandry characteristics in Galicia, Spain. Blood samples were obtained to measure beta-hydroxybutyrate (BHB), non-esterified fatty acids (NEFA), triglycerides (TG), and the activity of aspartate transaminase (AST) and gamma-glutamyl transferase. Cows in early lactation had higher levels of BHB and NEFA than mid lactation cows. High lipomobilization (NEFA > 400 µmol/L) was detected in 67% and 7% of early lactation and mid lactation cows, respectively, while subclinical ketosis (BHB > 1.2 mmol/L) was detected in 41% and 28% of the early lactation and lactation cows, respectively. TG concentrations were low in all cows suffering subclinical ketosis and in 61% of the cows with high lipomobilization. During early lactation, 30% of cows suffered hepatic lipidosis as detected by levels of AST. Compromised hepatic function was observed in early lactation cows as shown by lower concentrations of glucose, total protein, and urea.     

Increasing selenium supply during the close-up dry period improves nutrient metabolism and attenuates inflammatory response after calving in dairy cows

The objective of this study was to investigate whether feeding selenium (Se)-replete cows a Se-yeast supplement in late pregnancy affects nutrient metabolism and inflammatory response during the periparturient period. Twenty cows were randomly assigned to two groups with 10 cows each. Cows in one group received Se-yeast at 0.3 mg Se/kg DM during the last 4 weeks before calving in addition to fed a TMR containing supplemented sodium selenite at 0.3 mg Se/kg DM (Se-yeast), while cows in another group were only fed a TMR containing supplemented sodium selenite at 0.3 mg Se/kg DM (Control). Blood samples were collected and analyzed for nonesterified fatty acids (NEFA), β-hydroxybutyrate (BHBA), glucose, insulin, tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, serum amyloid A (SAA), haptoglobin (Hp), and albumin. In control cows, plasma NEFA, IL-1β, IL-6, SAA, and Hp levels increased after calving, but glucose, insulin, and albumin levels decreased after parturition. Se-yeast supplemental cows had lower postpartum concentrations of NEFA, TNF-α, IL-1β, IL-6, SAA, and Hp, and higher postpartum levels of glucose, insulin, and albumin compared with control cows. The results indicate that feeding Se-replete cows a Se-yeast supplement in late pregnancy improves nutrient metabolism and attenuates the inflammatory response after calving.     

日粮添加益生菌对干乳期奶牛生长性能、瘤胃发酵及氮平衡的影响

本研究旨在评估全混合日粮添加益生菌对干乳期奶牛生长性能、瘤胃发酵及氮平衡的影响.试验将体重为(440.92±3.33)kg、平均干乳期为42?d的60头荷斯坦奶牛随机分为2组,每组5个重复,每个重复6头.对照组饲喂玉米-豆粕型全混合日粮,处理组饲喂基础全混合日粮+200?mg/kg益生菌(枯草芽孢杆菌含量:1×106?...     

丙酸镁对泌乳早期奶牛体况、泌乳性能和代谢参数的影响

选用36头经产奶牛,根据泌乳期、上一泌乳期305 d产奶量和预产期,采用随机区组设计分为4组,对照组饲喂基础日粮,处理1,2和3组分别在基础日粮基础上添加丙酸镁50,100和150 g/d,研究丙酸镁对泌乳早期奶牛采食量、泌乳性能、血液代谢参数和尿酮浓度的影响。结果表明,添加丙酸镁对奶牛的采食量、乳脂率、乳蛋白率、乳糖率和乳干物质率无显著影响,添加丙酸镁100和150 g/d对产乳量、饲料转化效率、体况及代谢参数有改善,该二处理组产奶量、饲料转化效率、体况评分、能量平衡、血浆葡萄糖和胰岛素浓度均显著高于对照组(P<0.05),而血浆游离脂肪酸和β-羟丁酸浓度显著低于对照组(P<0.05),尿酮浓度(除100 g/d组产后7 d测定值与50 g/d组无显著差异外)显著低于对照组和50 g/d组(P<0.05)。根据试验结果,丙酸镁适宜添加量为100 g/d。     

Comparison of cholesterol levels among lipoprotein fractions separated by anion-exchange high-performance liquid chromatography in periparturient Holstein–Friesian dairy cows

Changes in lipoprotein profiles occur in dairy cows during the periparturient period and in cows with transition cow disease. Here, the lipoprotein profiles of Holstein–Friesian dairy cows during the periparturient period were obtained by anion-exchange, high-performance liquid chromatography to evaluate the usefulness of lipoprotein profile evaluation during the periparturient period and in cows with fatty liver and milk fever. Lipoprotein levels (including total and high- (HDL-C) and low-density lipoprotein (LDL-C) cholesterol) in 10 healthy cows were low 4 weeks prepartum, with the lowest values at calving or within 1 week of calving; the values increased at 8 weeks postpartum. The lipoprotein levels were measured in 16 cows diagnosed with fatty liver (n=10) or milk fever (n=6) and compared to 10 healthy dairy cows. A significant difference was observed in HDL-C between healthy cows (at calving and 1 week postpartum), and the fatty liver and milk fever cows. Cows with fatty liver and milk fever had a lower mean HDL-C than the 10 healthy dairy cows at calving and 1 week postpartum. HDL-C might be a good indicator of energy balance for differentiating healthy cows from those with transition cow disease.