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.     

Heritability estimates and genetic correlations of various production and reproductive traits of different grades of dairy cattle reared under subtropical condition

Inheritance of economic traits and their genetic correlation was studied in different breeds and their various grades (crossbred’s cattle) under the subtropical condition. Data on principal parameters comprising 10 years, that is 2004–2014, were utilized for the present study. Different grades of dairy cows comprising Holstein Friesian (HF), Sahiwal x Friesian (SxHF), Jersey (J), Jersey x Achai (JxAC) and Achai (AC) were included in the study. Heritability estimates and genetic correlations of some important productive and reproductive traits were worked out. Heritability estimates of certain economic traits were found to be: birthweight, 0.32 ± 0.181; age at maturity, 0.11 ± 0.136; age at first calving, 0.19 ± 0.162; days open, 0.09 ± 0.121; calving interval, 0.14 ± 0.211; dry period, 0.11 ± 0.124; lactation length, 0.04 ± 0.212 and lactation yield, 0.46 ± 0.206. Genetic correlation showed that body weight was significantly and positively correlated with lactation length (0.30) and lactation yield (0.81), while negatively correlated with age at maturity, age at first calving, days open, calving interval and dry period (?0.09, ?0.07, ?0.16, ?0.34 and ?0.002, respectively). Calving interval was positively and significantly correlated with the dry period (0.56), lactation length (0.72) and lactation yield (0.37). Moderate to higher heritability estimates with adequate genetic variance was found for body weight and lactation yield. The moderate to higher heritability estimates of birthweight in the present study revealed that this important trait might be considered in selection criteria.     

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.     

Relationship between the lactation curve and udder disease incidence in different lactation stages in first‐lactation Holstein cows

We examined the relationships between the shape of the first parity lactation curve and udder disease incidence at different stages of lactation in 538 Holstein cows. Data used were first‐parity daily milk yields and treatment records. Each cow was classified according to whether or not it had had udder disease at least once over the whole lactation period or in one of three stages within the lactation period. We then examined the differences in the shapes of the lactation curves between the disease incidence and non‐incidence group in each stage. Cows that had high rates of increase in milk yield and high milk yields in early lactation were predisposed to udder disease afterwards. Cows with high milk production over a long period but with low lactation persistency were predisposed to udder disease after the peak of lactation. There was no difference in total milk yield between incidence and non‐incidence groups in all stages, suggesting that, for a comparable level of lactation, cows without udder diseases have flatter lactation curves.     

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.     

Changes in circulating adiponectin and metabolic hormone concentrations during periparturient and lactation periods in Holstein dairy cows

Although our previous report demonstrated that adiponectin and AdipoR1 gene expressions changed among different lactation stages in the bovine mammary gland, its in vivo kinetics remain unclear in ruminant animals. In this study, we investigated the changes in circulating concentrations of adiponectin, as well as other metabolic hormones and metabolites, (i) during the periparturient period and (ii) among different lactation stages, in Holstein dairy cows. In experiment 1, serum adiponectin concentrations increased after parturition. Serum insulin concentrations were lower in the postpartum than prepartum period, whereas serum growth hormone (GH) concentrations increased in the postpartum period. Serum nonesterified fatty acids (NEFA) levels were increased during the postpartum period and were dependent on the parity. In experiment 2, there was no significant difference in plasma adiponectin concentrations among lactational stages. Plasma insulin concentrations tended to be lower in early lactation while plasma GH levels tended to be higher. Plasma NEFA concentrations were significantly lower in mid‐ and late‐lactation stages than non‐lactation stages. These findings indicate that elevation of serum adiponectin might be involved in energy metabolism just around parturition, and might exert its action through regulation of receptor expression levels in target tissues in each lactational stage in Holstein dairy cows.     

Genetic parameters for claw health and feet and leg conformation traits in Finnish Ayrshire cows

Genetic parameters for different claw disorders, overall claw health and feet and leg conformation traits were estimated for Finnish Ayrshire cows. The merged data set with records of claw health and feet and leg conformation traits consisted of 105 000 observations from 52 598 Finnish Ayrshire cows between 2000 and 2010. The binary claw health data and the linearly scored conformation data were analysed using an animal model and restricted maximum likelihood method by applying the statistical package ASReml. Binomial logistic models with mixed effects were used to estimate genetic parameters for sole haemorrhages, chronic laminitis, white‐line separation, sole ulcer, interdigital dermatitis, heel horn erosion, digital dermatitis, corkscrew claw and overall claw health. Estimated heritabilities for different claw disorders using a binomial logistic model ranged from 0.01 to 0.20. Estimated heritability for overall claw health using a binomial logistic model was 0.08. Estimated heritabilities for feet and leg conformation traits ranged from 0.07 to 0.39. The genetic correlations between claw health and feet and leg conformation traits ranged from ?0.40 to 0.42. All phenotypic correlations were close to zero. The moderate genetic correlation, together with higher heritability of feet and leg conformation traits, showed that RLSV (rear leg side view) is a useful indicator trait to be used together with claw trimming information to increase the accuracy of breeding values for claw health in genetic evaluation.     

Restricting access time at pasture and time of grazing allocation for Holstein dairy cows: Ingestive behaviour,dry matter intake and milk production

The objective of this study was to assess the effects of restricting access time to pasture and time of grazing allocation on grazing behaviour, daily dry matter intake (DMI), rumen fermentation, milk production and composition in dairy cows. Twenty-one autumn-calving Holstein cows were assigned to one of the following 3 treatments: providing access to a daily strip of pasture for either 8 h between 07:00 and 15:00 h (T7–15), 4 h between 07:00 and 11:00 h (T7–11), or 4 h between 11:00 and 15:00 h (T11–15). The experimental period consisted of 3 weeks of adaptation and 6 weeks of measurements. Cows were offered a daily herbage allowance of 18 kg DM/cow to ground level, 6.1 kg DM/day of a ground sorghum grain-based supplement and 5.2 kg DM/day of maize silage. Milk yield was greater for cows with 8 h access time to the pasture (25.4 vs. 24.1 for 8 and 4 h access time, respectively). Milk yield was not different between cows that access early (T7–11) or late (T11–15) to the grazing session. Milk protein yield was greater for cows with 8 h access time (0.75 kg/d) vs. 4 h access time treatments (0.72 kg/d). Cows with late access time to grazing in the morning produce more protein (0.74 kg/d) than cows with early access to the pasture (0.70 kg/d). Duration of access had a significant effect on herbage DMI (8.3 vs. 6.6 kg/d, for 8 and 4 h access, respectively), but there was no significant effect of time of grazing allocation. Intakes of concentrate and maize silage DM did not differ between treatments.     

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.     

The relationships between environmental parameters in livestock pen and physiological parameters of Holstein dairy cows

There has been an increase in temperature and the incidence of extreme weather events, such as heat wave, due to global warming, which has promoted the incidence of livestock diseases. Therefore, it is important to examine the effect of changes in environmental parameters on livestock performance. The aim of this study was to examine the relationship between ambient environmental conditions in livestock pen and the physiological parameters of Holstein dairy cows. The results showed that there was a decrease in the red blood cell counts, hemoglobin concentrations, and mean corpuscular hemoglobin concentration of the cows with increasing pen temperature, wet bulb globe temperature (WBGT), and temperature humidity index (THI). Additionally, high daily variation in temperature caused a decrease in the serum albumin levels of the cows. Moreover, the lowest serum calcium, inorganic phosphorus, and magnesium concentrations were observed in November, and were negatively correlated with the 24-hr temperature, WBGT, and THI range of the pen prior to sampling. Multiple regression analysis showed a positive correlation between serum cortisol concentration and 24-hr WBGT range of the pen prior to samplings and packed cell volume. However, serum cortisol and total protein concentrations were negatively correlated. Overall, the findings of the study suggest that large variation in temperature induced stress in the cows, which could be overcome by increased water consumption and improved protein digestion and absorption by the animals, and the addition of minerals, such as calcium to the diet.     

Sleep and lying behavior of milking Holstein cows at commercial tie‐stall dairy farms

The aim of this study was to clarify cow's sleep behavior on farm and to examine the influence of some environment and management factors on cow's sleep. Total 85 behavior data (summer 41, autumn 44) were corrected from 12 commercial tie‐stall dairy farm in northern Tohoku area. Daily duration, bout frequency, and averaged bout duration of sleep and lying were measured. Even though there was no significant difference in any lying measurements, daily duration, bout frequency, and averaged bout duration of sleep was significantly different among farms (p < 0.01, p < 0.01, and p < 0.05, respectively). However, we could not find that any managements influence on sleep. There was significant seasonal difference in daily sleep duration (p < 0.01) and sleep bout frequency (p < 0.05). On the other hand, daily lying duration and averaged lying bout duration were significantly different between seasons (p < 0.001 and p < 0.05, respectively). Primiparous cows slept longer and more frequent than multiparous (both p < 0.001). Milk solid‐non‐fat content was positively correlated with daily sleep duration (p < 0.05) and bout frequency (p < 0.01). These results might imply the productive importance of sleep related with anabolic hormones release.     

不同生理状态乳牛卵巢卵母细胞基因的差异表达

为了研究不同生理状态下的卵巢卵母细胞基因的表达情况，采集乳牛的卵巢，分离了卵母细胞，以单个卵母细胞的mRNA作为模板，用设计的随机引物和锚定引物，采用一步法RT-PCR扩增了卵母细胞基因。经聚丙烯酰胺凝胶电泳检测，发现有功能黄体和无黄体卵巢卵母细胞基因的电泳条带之间无明显差异，对一条明显差异条带进行回收、纯化，将纯化的PCR产物连接到T载体，阳性克隆经鉴定后，进行测序和同源性比较。结果显示，与体外培养的牛早期胚胎的一条序列具有很高的同源性。     

Endocannabinoids as endometrial inflammatory markers in lactating Holstein cows

The objective of this study was to consider endocannabinoid system as inflammatory markers in bovine endometrium to better understand the role of this system in regulating many of the functions that are related to inflammatory condition. At day 26 post‐partum, fourteen cows were divided into two groups depending on the inflammatory condition: 1‐ subclinical endometritis (n = 7, with purulent or mucopurulent uterine discharge detectable in the vagina) and 2‐ healthy (n = 7, No (muco)) purulent discharge. Blood samples were collected at 26 and 30 days relative to calving to determine plasma tumour necrosis factor (TNF) and lipopolysaccharide‐binding protein (LBP) concentrations; moreover, uterine biopsy was carried out on day 26 post‐partum to measure mRNA abundance of TNF, interleukin‐1B (IL1B), interleukin‐6 (IL‐6), C‐X‐C motif chemokine ligand 8 (CXCL8), endocannabinoid receptor (CNR2), N‐acyl phosphatidylethanolamine phospholipase D (NAPEPLD), fatty acid amide hydrolase (FAAH), N‐acylethanolamine acid amidase (NAAA) and monoglyceride lipase (MGLL) by real‐time PCR. Results showed mean plasma concentrations of TNF and LBP were lower in healthy cows compared to subclinical endometritis cows (p < .05). Relative mRNA expression for NAAA and FAAH was decreased (p < .05), and relative mRNA expression for CNR2 and NAPEPLD increased in cows with subclinical endometritis compared to healthy cows. In conclusion, relative mRNA expression of TNF, IL1B and CXCL8 and plasma concentration of LBP increased during inflammatory condition along with decreased endocannabinoids hydrolyzing enzyme (NAAA and FAAH), increased enzymes that synthesize endocannabinoids (NAPEPLD) and relative gene expression of the endocannabinoid receptor; together, these contribute to increased endocannabinoids levels during inflammation. Overall, we provide evidence that endocannabinoid system is altered in endometrium tissue during inflammation through increased mRNA expression of CNR2 and synthesis enzyme and decreased mRNA expression of hydrolyzing enzymes interfere with pro‐cytokine production and signalling, which may interfere with the onset and progression of inflammation.     

Expression of fibroblast growth factor 21 in the liver of dairy cows in the transition period and during lactation

Fibroblast growth factor 21 (FGF21) has been identified as a novel hormonal factor involved in the regulation of metabolic adaptations during energy deprivation. The present study aimed to investigate the expression of the FGF21 gene in the liver of dairy cows during the transition from pregnancy to lactation. Therefore, the relative mRNA abundance of FGF21 in liver biopsy samples of 20 dairy cows in late pregnancy (3 weeks pre‐partum) and early lactation (1, 5, 14 weeks post‐partum) was determined. It was observed that hepatic mRNA abundance of FGF21 at 1 week post‐partum was dramatically increased (110‐fold) compared to 3 weeks pre‐partum (p < 0.001). With progress of lactation, mRNA concentration of FGF21 was declining; nevertheless, mRNA abundance at 5 and 14 weeks post‐partum remained 25‐ and 10‐fold increased compared to 3 weeks pre‐partum (p < 0.001). Using a gene array technique, it was found that many genes involved in fatty acid oxidation, gluconeogenesis and ketogenesis were up‐regulated during early lactation compared to late pregnancy. Moreover, there were positive linear correlations between hepatic mRNA concentration of FGF21 and mRNA concentrations of genes involved in ketogenesis as well as carnitine synthesis and carnitine uptake at various time‐points during lactation, indicating that FGF21 could play a role in ketogenesis and carnitine metabolism in the liver of dairy cows (p < 0.05). In overall, the present study shows that expression of the FGF21 gene is strongly up‐regulated during the transition period. It is assumed that the up‐regulation of FGF21 might play an important role in the adaptation of liver metabolism during early lactation in dairy cows such as in other species.     

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。     

Adrenal cortex reactivity in dairy cows differs between lactational stages and between different feeding levels

Changes in ACTH challenge test characteristics in dairy cows changing their physiological status at different lactational stages and different feeding levels were not investigated in terms of repeatability yet. In 23 multiparous Holstein cows (10 cows fed a sole fresh herbage diet without concentrate, 13 cows fed with concentrate), three ACTH challenge tests were performed: once during pregnancy shortly prior to drying off ( T1 ), and in week 3 ( T2 ) and 8 ( T3 ) after parturition. Test characteristics were correlated to performance and metabolic parameters: DMI, BW, energy balance (EB), plasma concentrations of free fatty acids (NEFA) and beta‐hydroxybutyrate (BHB). Basal plasma cortisol concentrations were higher at T1 compared with T2 and T3 (p < .05). The adrenal cortex sensitivity (expressed as total AUC (AUC_t) of cortisol response after ACTH application) was lowest at T2 compared with T1 and T3 (p < .05). Ranking of the individual animals’ responses was not repeatable between time points of the ACTH tests. Enhancing the energy deficiency during early lactation by omission of concentrate did not affect baseline cortisol concentrations in plasma, but decreased peak height at T2 (p < .05). Baseline plasma cortisol concentrations were positively correlated with cortisol peak values after ACTH application, previous lactation performance, milk yield and BW (p < .05). The AUC_t was positively correlated with baseline cortisol concentrations, EB and DMI. Cortisol release after ACTH injection was lower in animals with high plasma concentrations of NEFA, BHB and with higher contents of fat and free fatty acids in milk (p < .05). Cortisol peak height after ACTH administration was higher in cows with a more positive EB, higher DMI and lower plasma concentrations of NEFA and BHB. In summary, cortisol responses to ACTH challenges in this study were not repeatable in dairy cows changing their physiological status.     

复方中草药添加剂对荷斯坦奶牛免疫和泌乳性能的影响

试验旨在研究自制的复方中草药添加剂对泌乳奶牛免疫机能与泌乳性能的影响。试验采用4×4拉丁方设计。选择4头胎次、泌乳天数、体重均相近的健康荷斯坦奶牛,分为4组,其中A组为对照组,饲喂基础饲粮,B、C、D组分别在基础饲粮中添加30、50和80 g/d复方中草药。试验分4期进行,每期28 d(预试期7 d,正试期14 d,排空期7 d)。结果显示:1)添加复方中草药显著增加了白细胞数、嗜中性细胞百分比及血小板数(P<0.05);但对血液生化指标无显著影响(P>0.05)。2)添加复方中草药显著降低了丙二醛(MDA)含量(P<0.05);与对照组相比,添加30 g/d复方中草药显著增加了血清免疫球蛋白M(IgM)及超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、过氧化氢酶(CAT)活力(P<0.05)。3)复方中草药添加剂可以增加血清生长激素(GH)和催乳素(PRL)含量,且添加30 g/d时显著增加(P<0.05)。4)与对照组相比,日粮添加30、50和80 g/d可以使产奶量分别增加10.18%、6.79%和5.19%,但是对产奶量、乳成分及体细胞数的影响均不显著(P>0.05)。试验结果表明,复方中草药添加剂可以调节奶牛机体免疫性能和提高抗氧化能力,且每头牛添加30 g/d时效果最佳。但其对奶牛泌乳性能无显著影响。     

Physiological changes during feeding and rumination in cows

In this study, we investigated the physiological changes in cattle during feeding and rumination. We collected blood samples every 5 min by using an automated blood sampling system and simultaneously recorded feeding, ruminating, and other behaviors using a video camera. Plasma non‐esterified fatty acid (NEFA) concentrations continuously decreased during feeding and decreased temporarily during rumination. Plasma glucose concentration continuously decreased during feeding and remained stable during rumination. During feeding and rumination, there were no characteristic increases and subsequent decreases in plasma insulin and growth hormone (GH) concentrations, although insulin concentrations were positively correlated with glucose concentration. NEFA concentrations were not correlated with GH and insulin concentrations. In terms of chewing behavior, feeding and rumination are similar; therefore, the changes in metabolites such as NEFA might have been the same. Combination of behavioral observations and application of an automated blood sampling system could contribute to new findings on behavioral and physiological changes regarding the temporary decrease in plasma NEFA concentration during rumination in ruminants.     

奶牛酮病发病原因及其对生产性能影响调查分析

探索奶牛酮病发病原因、发病规律及其对生产性能的影响,对986头围产期奶牛进行跟踪调查分析。结果表明,奶牛酮病发病率为31.74%,死亡率为4.15%;秋季发病率最高,可达37.4%,其次是冬季和夏季,春季发病率最低;随着胎次、年龄和产乳量的增加,奶牛酮病的发病率明显增高;在第1个泌乳月奶牛酮病的发病率最高,可达50.43%;日粮种类和微量元素越少,奶牛酮病就越容易发生;奶牛发病后受胎率明显降低;发病后产乳量、乳脂率、乳蛋白率、乳糖率和乳干物质比发病前均明显降低,差异显著（P〈0.05）。奶牛酮病发病具有一定的规律性,且可降低奶牛的繁殖性能、产奶量和乳品质。