围产期奶牛的代谢特点及其营养调控

围产期是奶牛泌乳周期中最为关键的阶段,该阶段奶牛代谢最大的特点是能量摄入减少而需求增加从而导致能量负平衡。探寻缓解围产期奶牛能量负平衡的调控措施是减少奶牛疾病发生率的重要基础。本文对近年来围产期奶牛能量负平衡的营养调控研究进行了归纳和总结,旨在为寻找提高奶牛健康水平和生产性能的途径提供新的思路。     

奶牛围产期营养、代谢病及其预防措施

奶牛围产期系指分娩前后各 1 5d时间 ,分围产前期 (后称干奶后期 )与围产后期 (分娩后 1 5d)。1　围产期奶牛营养需要与饲养要求应采用全混合日粮 (TMB)。干物质 (DM )采食量应占2 .5 %～ 3 .0 % ,奶牛能量单位 (NND/kgDM )为 2 ,粗蛋白蛋(CP)为 1 3 %～ 1 4 % ,Ca为 0 .8%～ 1 .2 % ,P为 0 .3 %～ 0 .4 % ,中性洗涤纤维 (NDF)为 2 3 %～ 2 5 %。临产前营养中上等水平 ,BCS≥ 3。临产前 7d酌情增加精料量 ,最大喂量不宜超过体重的 1 % ,日粮结构仍以优质干草为主。为做到因牛而宜 ,保证营养适中 ,笔者建议精料给量如表 1。表 1　奶…     

围产期奶牛代谢与营养调控研究进展

围产期是奶牛泌乳周期中最为关键的阶段,该阶段奶牛代谢的最大特点是能量摄入减少而需求增加从而导致能量负平衡.改善围产期奶牛的营养条件,最大限度地缓解能量负平衡,对于充分发挥奶牛的生产性能至关重要.本文综述了围产期奶牛的代谢特点以及营养调控研究进展,旨在为提高奶牛的生产性能和健康水平提供新的思路.     

奶牛围产期几种常见代谢病的营养调控措施

奶牛由妊娠后期（产前2～3周）转变为泌乳初期（产后2～3周）这一阶段称之为过渡期，亦称围产期。此时期代谢性疾病发病率很高，期间最高的当属产乳热、酮病和脂肪肝。据调查在美国大约7．2％的高产成年奶牛患有产乳热，患此病的奶牛平均寿命缩短3～4岁。且易感染率比未得此病的牛高2～5倍。如酮病和脂肪肝也是常见群发性多发病。有资料报道，我国奶牛酮病的发病率占泌乳牛的15％～30％。     

围产期奶牛的生理特点及营养代谢特征研究进展

围产期(产前3周至产后3周)是奶牛内分泌和代谢发生巨变的时期,此时期奶牛经历了不同程度的能量负平衡,可影响其产后生产性能和对疾病的易感性.本文综合阐述了围产期奶牛的生理特点及营养代谢特征,为以后围产期奶牛的饲养管理及科学研究提供新的思路.     

围产期奶牛能量负平衡营养调控研究进展

随着我国畜牧养殖业的快速发展,奶牛养殖业得到了进一步的发展,市场需求量持续增加。奶牛产量不断提升,奶牛被动淘汰率持续增加。奶牛生产前,胎儿快速发育,为满足产奶需求奶牛乳房会快速发育,营养需要持续增加,母牛的采食量大幅度降低,导致营养摄入量无法满足于奶牛的生长所需,进而造成能量负平衡。     

预防围产期奶牛酮病的营养策略

本文综述了围产期奶牛的脂肪代谢变化特点,对处在围产期奶牛酮病预防的营养调控策略进行了总结,以期为奶牛生产提供理论基础和实践参考.     

产前运动对围产期奶牛生理代谢指标的影响

本试验旨在研究产前运动对围产期奶牛生理代谢指标的影响,为围产期奶牛健康管理提供科学指导和理论依据。试验选取年龄相似,体况评分、胎次和预产期相近的经产荷斯坦奶牛24头,随机分为试验组（TRT组）和对照组（CON组）,每组12头,统一饲养管理。于预产期前21 d开始,TRT组奶牛每日09：00和16：00以<3 km/h的速度运动1 h,每头奶牛每日总运动量为（4.0±0.2） km/d;CON组自由活动。分别在预产期前21、7 d、分娩当天及产后7、30 d （分别记为－21、－7、0、+7和+30 d）,于晨饲前采集血液,测定血浆中非酯化脂肪酸（NEFA）、β-羟基丁酸（BHBA）、葡萄糖（GLU）、甘油三酯（TG）、胆固醇（CHOL）、肌酐（CREA）及尿素（UREA）浓度。结果显示,试验期间,TRT组血浆NEFA、BHBA浓度与CON组相比均呈下降趋势（0.05<P<0.1）,－7 d时TRT组NEFA浓度显著低于CON组（P<0.05）;TRT组血浆GLU浓度变化较CON组平稳,在＋30 d极显著高于CON组（P<0.01）;两组血浆TG浓度均在分娩当天急剧下降,产前血浆TG浓度均极显著高于分娩后各时间点（P<0.01）,＋30 d时TRT组极显著高于CON组（P<0.01）;血浆UREA、CREA浓度在两组间无显著差异（P>0.05）。综上,以<3 km/h的速度进行运动（4.0 km/d±0.2 km/d）,可有效降低围产期奶牛血浆NEFA和BHBA浓度,缓解能量负平衡（NEB）压力。     

奶牛围产期营养与疾病

奶牛不同生理时期的营养需要有很大差异。围产期的营养管理是奶牛泌乳、繁殖和控制围产期疾病发生的关键。围产期疾病是一组与营养代谢有关的、互相关联的代谢相关性疾病，其中营养不平衡造成的低钙血症是引起围产期相关疾病的根本原因。在保证围产期其它营养需要的同时，根据离子平衡理论给予阴离子盐调节离子差(DCAD)为-10～-15meq／DMI 110g，尿的pH为6．0～6．5时，体液偏酸性，可有效动员骨钙，使血钙浓度上升，从而减少围产期疾病的发生。     

Nutritional myodegeneration in dairy cows

A syndrome is described in which parturient dairy cows showed clinical signs consistent with milk fever but failed to respond to conventional therapy. The affected cows were reluctant to walk, moved stiffy and in severe cases became recumbent. The condition was apparently precipitated by low vitaimin E and selenium intake, stress of pregnancy and in one outbreak erratic feeding. Skeletal and cardiac myodegeneration were observed grossly and histologically but an almost full term fetus from an affected cow showed no muscle lesions. A high incidence of retained placentae was also recorded.     

Genetics and physiology of leptin in periparturient dairy cows

In dairy cattle, the increase in milk yield has been accompanied by a more negative energy balance (EB) during early lactation and a decrease in fertility. As the hormone leptin is involved in regulation of nutritional status and reproductive function this hormone is an interesting protein to investigate during the periparturient period in dairy cattle. This study was performed to get insight into the function of leptin during the periparturient period and to perform an association study between polymorphisms in the bovine leptin gene and leptin receptor gene and fertility as well as production traits. Leptin concentrations in the periparturient cow undergo remarkable changes; leptin concentrations were high during late pregnancy and declined to a nadir at parturition. Genetic analysis of the leptin gene indicated that a combination of three polymorphisms located at a 135 bp region of the leptin promoter explained most of the variance in prepartum leptin concentrations. The two extreme genotype combinations could be used to investigate the function of leptin concentrations in pregnant cows. A polymorphism located on intron 2 of the leptin gene explained a significant part of the variation in milk yield. On the promoter region of the leptin gene an SNP was detected that was associated with first postpartum luteal activity (FPLA). This SNP could be a candidate marker for fertility in dairy cows. Another SNP on the leptin promoter was associated with energy balance and dry matter intake (DMI) where a higher dry matter intake occurred together with a higher energy balance. Two genotype combinations of the aforementioned three associated SNPs were defined which had a good milk yield together with a good energy balance and fertility. Calculations of an economical value per trait have to validate if one of these genotype combinations would be a possible candidate to be used in selection.     

Evaluation of biochemical profile of dairy cows with metabolic diseases in tropical conditions

The aims of this study were to characterize the biochemical profile, the reproductive performance and to identify potential predictive biomarkers of disease state of dairy cows with hyperketonemia, lipomobilization and hypocalcemia raised in tropical conditions in southeastern Brazil. Dairy cows (n = 50) were divided into a group of healthy cows (n = 14), cows with lipomobilization (n = 14), cows with hypocalcemia (n = 11), and a group of cows with hyperketonemia (n = 11). Evaluation of body condition score (BCS), body weight (BW) and blood samples was performed on 21, 14, 7, 4 and 2 days before calving, parturition, 1, 7, 14, 21, 30, 45 and 60 days post-partum and milk production was recorded on days 7, 14, 21, 30, 45 and 60 after parturition. Blood samples were assayed for aspartate aminotransferase (AST), gamma-glutammyltransferase (GGT), albumin, total protein, globulin, fibrinogen, total cholesterol, triglyceride, urea and creatinine concentrations. The biochemical profile, BCS, BW, milk production and reproductive performance differed (p < .05) among the groups. Our findings indicate changes in the biochemical profile of dairy cows with metabolic diseases and impaired production and fertility of dairy cows in this group. Variable importance in projection plots demonstrated that cholesterol, urea, total protein, albumin and fibrinogen in the serum were the strongest discriminators between cows with hypocalcemia and healthy cows; and AST, cholesterol, urea and triglycerides for cows with hyperketonemia and healthy cows; and cholesterol, urea, triglycerides, total protein and fibrinogen for lipomobilization and healthy cows, which might be useful as predictive biomarkers of the disease state.     

Chronic metabolic acidosis in dairy cows]

Complex clinical and clinico-biochemical examination of the blood, urine and rumen liquor in a herd of dairy cows revealed chronical metabolic acidosis accompanied by rumen dysfunction and by a reduced butterfat content of milk. During the first examination of the acid-base state of the blood was almost at a standard level. An increased level of urea in blood plasma and a higher GOT transaminase activity testified to an excessive load on the liver. Urine pH was considerably deviated towards the acidic side and inorganic phosphorus was present in urine in a greater concentration. The pH of rumen liquor was slightly shifted towards alkalinity owing to the release of NH3 from urea in the food ration. The diagnosis--suspect chronical metabolic acidosis--was determined on the basis of the first examination. Chronical metabolic acidosis was definitely proved by the second examination when urea had been excluded from the feed ration. Repeated examinations revealed chronical metabolic acidosis which had originally been accompanied by a higher rumen liquor pH. On the basis of case histories and mechanisms of chronical acidosis, measures were proposed, resulting in an increase of the butterfat content of milk. Chronical metabolic disorders often follow a long-lasting latent pattern, manifesting themselves as a reduced milk yield and lower resistance; the clinical form of disease appears only at a later stage. The system of preventive diagnostics provides information on the changes in the composition of internal medium and of the faeces before a drop occurs in milk and fat production. These measures prevent metabolic disorders and high losses of produce which otherwise remain hidden for a long time.     

Body condition scores in dairy cows: associations with metabolic and endocrine changes in healthy dairy cows

Relationships between body condition scores (BCS), metabolic profiles and endocrine traits were investigated in 53 healthy Red Holstein cows. Cows were categorized into groups based on BCS ante-partum (a.p.: >3.25 or < 3.25) and on BCS losses during the first 8 weeks after calving (ABCS8 > 0.75 or < or = 0.75). Blood samples were collected 1 week before calving and every 2 weeks post-partum (p.p.). Cows with BCS a.p. >3.25 and deltaBCS < or = 0.75 were oldest and cows with BCS a.p. < or = 3.25 and deltaBCS < or = 0.75 were youngest. Cows with BCS > 3.25 a.p. and that lost > 0.75 BCS in the first 2 months of lactation exhibited signs of subclinical ketosis. If statistically adjusted for the effect of lactation number, average milk yield within the first 8 weeks p.p. and milk fat concentrations were similar between BCS groups, whereas milk protein concentrations differed significantly between BCS groups. Significant differences between groups were observed for blood plasma glucose, bilirubin, beta-hydroxybutyrate, non-esterified fatty acids and insulin concentrations. No differences were seen for albumin, urea, insulin-like growth factor-1, and 3.5.3'-triiodothyronine concentrations and for plasma activities of glutamate-oxalacetate transaminase, gamma-glutamyltransferase and glutamate dehydrogenase. There was a good agreement between BCS and profiles of metabolites and hormones related to energy metabolism in clinically healthy cows. Cows in good body condition a.p. had greater risks of metabolic problems because of excessive mobilization of body reserves. However, the metabolic status was best in cows with a BCS > 3.25 a.p.. if they did not lose much body condition p.p.     

Effect of yeast products supplementation during transition period on metabolic profile and milk production in dairy cows

Tropical Animal Health and Production - The aim of the current study was to assess the effect that supplementation with yeast culture plus enzymatically hydrolyzed yeast (YC-EHY) during the...     

奶牛亚急性瘤胃酸中毒的发生与危害

亚急性瘤胃酸中毒（SARA）是一个大多数牛场普遍存在的奶牛代谢性疾病。围产期、干物质采食量（DMI）过高、日粮配制差及采食模式变化过大等奶牛均易发生亚急性瘤胃酸中毒,继而造成干物质采食量下降、纤维素消化率降低、乳成分改变及引发腹泻等疾病。本文对奶牛亚急性瘤胃酸中毒的病因及危害等方面进行了简述。     

Nutritional evaluation of transgenic cottonseed in the ration of lactating dairy cows

The effects of feeding transgenic (Bt) whole cottonseed (WCS) were studied in lactating cows. Twenty multiparous crossbred cows (Karan Swiss × Karan Fries) in early lactation were given a concentrate mixture containing 40% crushed delinted non-transgenic (non-Bt) WCS, 2 kg wheat straw and green fodder ad lib for a 15-day adaptation period. Thereafter, the cows were divided in two similar groups of 10 each on the basis of milk yield, body weight (BW) and date of calving. The non-Bt control group continued on same ration, while for the Bt group the non-Bt WCS was replaced by transgenic WCS, in a feeding trial of four weeks. The diets provided a minimum of 2 kg cottonseed/cow/d. Mean DMI/100 kg BW and milk yield of non-Bt and Bt groups was 3.48 and 3.45 kg and 11.4 and 12.0 kg/d, respectively. Intake of nutrients, digestibility, milk production and body condition score (BCS) did not differ between the groups (P > 0.05), but BW gain was higher (P < 0.05) in the Bt group than the non-Bt group, probably as a result of hoof problem in two cows of non-Bt group, which when compared excluding two animals from each group did not differ significantly (P > 0.05). Transgenic protein (Cry1C) was not detected in the weekly milk samples or in blood plasma at the end of the experiment, showing that delinted WCS containing Cry1C protein can safely be fed to lactating cows.     

Nutritional and metabolic diseases involving the nervous system

This article will discuss eight diseases that alter normal nervous system function: hypovitaminosis A, water deprivation/salt toxicity, ammonia toxicosis, hypomagnesemia, hypocalcemia, nervous ketosis, hepatoencephalopathy, and rumen metabolic acidosis.