芪黄素对奶牛乳房炎及其生产性能影响的研究

为了研究芪黄素对奶牛乳房炎及其生产性能的影响,通过对产奶牛中随机选择177头奶牛,进行拌料饲喂双盲对比试验。每月统计牛奶产量、乳房炎发生率等数据,研究芪黄素对奶牛乳蛋白率、乳脂率、产奶量、体细胞数和乳房炎发病率的影响。结果表明:芪黄素对奶牛体细胞数的改善和产奶量的提升具有显著作用,乳房炎的平均发病率在用药后出现了明显的下降,且呈显著下降,这表明芪黄素预防奶牛乳房炎效果显著。     

奶牛乳房炎的中西医诊治

奶牛乳房炎是泌乳奶牛的常发病之一,发病率较高．所造成的经济损失较大。根据对部分奶牛场和饲养户的调查统计．乳房炎发病率占泌乳牛的20％～40％．有的阳性检出率达50％．而隐性乳房炎占全部乳房炎的30％以上。由于该病初期症状不明显,易造成误诊、漏诊而延误治疗,致使产奶量日渐减少．并影响牛奶的质量,造成较大的经济损失;还可使奶牛发情期延迟,情期受胎率下降;病重者造成瞎奶头或败血症而淘汰。     

温湿指数(THI)对摩尼本水牛产奶量影响的研究

本试验研究了温湿指数(THI)对摩尼本水牛产奶量影响。试验证明：产奶量随温湿指数的增大而下降，平均温湿指数与平均产奶量为负相关，相关系数R=-0．9。     

奶牛隐性乳房炎综合防制措施的研究与应用

先后在6个奶牛场开展了为期2~3年的试验,通过加强饲养管理,人工药物干奶及淘汰久治无效的病牛等措施;采集试验前后的奶样,统计分析试验前后乳房炎的发病率及产奶量。结果表明,经过2~3年的防制,6个牛场隐性乳房炎平均检出率由试验前的43.29%降为20.96%;临床型乳房炎的发病率与试验前相比,平均降低了59.84%。经人工药物干奶,试验组奶牛(908头,干奶期乳区内注射干奶安)产犊后比干奶前的隐性乳房炎发病率降低了74.78%,而对照组奶牛(310头,干奶期不做处理)的发病率仅降低了23.62%;产犊后与干奶前瞎奶头数相比,试验组减少25.51%,而对照组却升高32.26%。与试验前相比,奶牛产奶量平均提高了11.85%。结果说明制定的奶牛隐性乳房炎综合防制措施行之有效,能降低奶牛乳房炎发病率,提高奶产量和质量。     

中草药添加剂(蒲公英流浸膏)对奶牛乳房炎及其生产性能的影响

笔者选择110头产奶量相近、泌乳日相近的高体细胞奶牛,分为对照组和试验组,试验组饲粮中加喂商品名康华素,主要成分为蒲公英流浸膏的中草药添加剂。结果表明,试验期40 d内对照组平均体细胞数上升了20万,试验组平均下降32万。试验组临床乳房炎乳区数比试验前降低了3.18%,头把坏奶数增加了0.91%。添加康华素的试验组隐性乳房炎检测3+比例比试验前降低了5.91%,但2+比例上升了5.45%。产奶量急剧下降,但是通过分析产奶量下降的幅度来看,40 d内对照组产量平均下降5.1 kg,试验组平均下降3.8 kg。试验组下降幅度却比对照组少下降1.3 kg。本试验证明了蒲公英浸流膏对奶牛乳房炎的控制与治疗上有明显的作用,对奶牛产奶量的维持有一定效果。在使用期间没有抗生素残留,符合安全绿色的养殖要求。     

奶牛应用中草添加剂的试验效果观察

消化道疾病和子宫炎、乳房炎、代谢病是奶牛常见病,提高饲料利用率,增加产奶是实现畜牧业提质增效的有效途径.本文报道应用三种中药添加剂可以达到预防消化道疾病发生,降低子宫炎、乳房炎发病率,提高饲料利用率,增加产奶量.     

奶牛应用中草药添加剂的试验效果观察

消化道疾病和子宫炎、乳房炎、代谢病是奶牛常见病，提高饲料利用率，增加产奶是实现畜牧业提质增效的有效途径。本文报道应用三种中药添加剂可以达到预防消化道疾病发生，降低子宫炎、乳房炎发病率，提高饲料利用率，增加产奶量。     

胎次、妊娠天数及月份与奶牛产后疾病相关性探析

研究不同胎次、妊娠天数、围产时间、犊牛初生重及月份与奶牛产后疾病的相关性,为降低奶牛产后疾病发病率提供参考。本文调查了宁夏某场2 975头中国荷斯坦牛不同胎次、妊娠天数及月份等对奶牛产后疾病胎衣不下、乳房炎、子宫炎、蹄病及产后瘫痪的影响程度,并进行相关分析。研究结果表明,随着胎次的增加,奶牛胎衣不下、乳房炎、蹄病和产后瘫痪的发病率逐渐增加,但对子宫炎发病率的影响不明显,其中第6胎奶牛的产后发病率最高。5-7月份奶牛产后疾病的发病率最高。妊娠天数和奶牛进入围产圈时间的增加使得产后疾病的发病率降低。犊牛初生重的增加使得奶牛胎衣不下和产后瘫痪的发病率升高。患胎衣不下导致乳房炎和子宫炎发病率增加,患蹄病导致胎衣不下、乳房炎和子宫炎发病率增加,产后瘫痪导致胎衣不下、乳房炎发病率增加。不同胎次、妊娠天数、产犊月份、围产时间和犊牛初生重对奶牛产后胎衣不下、乳房炎、子宫炎、蹄病和产后瘫痪有一定的影响,且产后疾病间相互影响。     

腐植酸钠对奶牛产奶量和隐性乳房炎的影响

选用泌乳天数和产奶量相近的初产新西兰荷斯坦奶牛60头,随机分为两组(n=30),通过饲养实验的方法,研究了日粮中添加腐植酸钠对奶牛产奶量和隐性乳房炎的影响。试验组牛每头饲喂腐植酸钠40g/天,拌到精料中,分2次给予,连续饲喂30天,两组牛基础日粮和饲养管理条件一致。试验期间,试验组牛和对照组牛平均产奶量分别为22.6kg/天和22.2kg/天,组间差异不显著(P>0.05)。CMT法检测隐形乳房炎的结果,试验组乳区均分值与对照组比较下降了59.1%(P<0.01),腐植酸钠添加前后比较下降了60.8%(P<0.01)。奶牛日粮中添加腐植酸钠可明显降低隐性乳房炎的发病率,具有提高产奶量的趋势。     

奶牛乳房炎的综合防治措施

乳房炎是奶牛泌乳期发病率很高的一种乳房疾病,可使患牛泌乳机能及产奶量急剧下降,造成奶牛生殖机能失调,成为奶牛的常见病和多发病。据统计,奶牛发生一次乳房炎产奶量平均下降8%,严重影响养牛经济效益。就此本刊专家给出了综合防治措施,供大家参考。     

温湿指数(THI)对摩尼本水牛产奶量影响的研究

本试验研究了温湿指数（THI）对摩尼本水牛产奶量的影响。试验证明：产奶量随温湿指数的增大而下降，平均温湿指数与平均产奶量为负相关，相关系数R=-0．9。     

温湿度指数与奶牛生产性能的关系

本研究用温湿度指数(THI)为指标,探讨了奶牛生产性能随THI变化的全年动态关系。奶牛的直肠温度、呼吸频率和乳中体细胞数在THI小于68时保持相对平稳,超过68时开始大幅度上升,而采食量、产奶量、乳脂率、乳蛋白率在THI小于70时保持相对平稳,超过70时开始大幅度下降。结果表明,只有当THI大于70时才会导致奶牛生产性能下降,THI每升高1个单位,产奶量下降0.4 kg。当THI从68上升到79时,THI每升高1个单位,乳脂率下降0.02%,乳蛋白率下降0.01%,体细胞数则上升2.77×104个/mL。奶牛生产性能指标、乳成分指标及乳中体细胞数与THI间均呈良好的三次曲线关系。因此,THI是用于评估温热环境对奶牛生产性能影响的一个有效且方便的指标。     

Length of lags in responses of milk yield and somatic cell score on test day to heat stress in Holsteins

We used daily records from provincial Japanese weather stations and monthly test‐day records of milk production to investigate the length of the lags in the responses of cows’ milk yield and somatic cell score (SCS) to heat stress (HS). We also investigated the HS thresholds in milk yield and SCS. Data were a total of 17,245,709 test‐day records for milk and SCS in Holstein cows that had calved for the first time between 2000 and 2015, along with weather records from 60 weather stations. Temperature–humidity index (THI) values were estimated by using average daily temperature and average daily relative humidity. Adjusted THI values were calculated by using temperature, relative humidity, wind speed, and solar radiation. The model contained herd, calving year, month of test day, age group, days in milk, and THI as a fixed effect. THIs for each day from 14 days before the test day until the test day were used to represent the HS effects. The HS occurring 3 days, and between 8 and 10 days, before the test day had the greatest effect on the milk yield and SCS, respectively. The threshold THI values for the HS effect were about 60–65 for both traits.     

Genetic variation of adaptation to heat stress in two Spanish dairy goat breeds

Monthly test-day records of milk yield and composition in Murciano-Granadina (MG) and Payoya (PYA) dairy goats were combined with weather data from meteorological stations, to analyse the effects of heat stress on dairy traits, measured with an index of temperature and relative humidity (THI). A 'repeatability animal model' and a 'reaction norm animal model' were used to estimate genetic (co)variance components. Estimates obtained with both models were very similar. The h(2) of daily yields in MG did not vary throughout the THI scale, but the pattern of variation of content traits showed negative trends for increasing THI values. In PYA, a slight positive tendency throughout the THI scale was observed for the same traits. The genetic correlations between subsequent points in the THI scale were lower than 0.80 when they were computed between low and high THI points. The same reaction norm was observed for all traits. Using the 'reaction norm animal model', it was possible to identify those animals that show the same performance throughout the THI trajectory (robust) and those with varying performances (tolerant and non-tolerant to heat stress). Results in this study also show that heat tolerance decreases, while the genetic level for milk traits increases. Losses because of heat stress were equivalent to 1.9 and 3.1% in the yearly yield of fat and protein for MG and PYA, respectively.     

Dual-purpose Guzerá cattle exhibit high dairy performance under heat stress

The present study evaluated the heat stress response pattern of dual-purpose Guzerá cattle for test-day (TD) milk yield records of first lactation and estimated genetic parameters and trends related to heat stress. A total of 31,435 TD records from 4,486 first lactations of Guzerá cows, collected between 1986 and 2012, were analysed. Two random regression models considered days in milk (DIM) and/or temperature × humidity-dependent (THI) covariate. Impacts of −0.037, −0.019 and −0.006 kg/day/THI for initial and intermediate stages of lactation were observed when considering the mean maximum daily temperature and humidity to calculate THI. Heritability estimates ranged from 0.16 to 0.35 throughout lactation and THI values, suggesting the possibility to expect gains from selection for such trait. The variable trajectory of breeding values for dual-purpose Guzerá sires in response to changes in THI values confirms that the genotype × environment interaction due to heat stress can have some effect on TD milk yield. Despite the high dairy performance of Guzerá cattle under heat stress, estimated genetic trends showed a progressive reduction in heat tolerance. Therefore, new strategies should be adopted to prevent negative impacts of heat stress over milk production in Guzerá animals in future.     

Exploration of factors determining milk production by Holstein cows raised on a dairy farm in a temperate climate area

In this study, we examined factors that affected milk production by cows raised in a temperate climate area. We conducted this study on a large dairy farm containing approximately 2000 Holstein cows, located in a temperate climate area. We collected 7803 calving records for 4069 cows from 2012 to 2016. We then assessed the effect of hot weather on milk yield by examining three climate factors: season, maximum temperature (MAX), and the temperature and humidity index (THI). We found that increases in heat stress caused linear decreases in milk yield (P?<?0.05). Additionally, the effects of the three climate factors on milk yield varied depending on cow parity and days open (P?<?0.05). Thus, management procedures should consider cow parity and lactating stage to minimize the negative effects of heat stress on milk production. We also found that the lowest Akaike information criterion value was obtained in our model when using THI for 305-day milk yield. This suggests that THI is a more accurate variable for evaluating heat stress than MAX or season.

     

Estimation of genetic parameters for heat stress,including dominance gene effects,on milk yield in Thai Holstein dairy cattle

Heat stress in tropical regions is a major cause that strongly negatively affects to milk production in dairy cattle. Genetic selection for dairy heat tolerance is powerful technique to improve genetic performance. Therefore, the current study aimed to estimate genetic parameters and investigate the threshold point of heat stress for milk yield. Data included 52 701 test‐day milk yield records for the first parity from 6247 Thai Holstein dairy cattle, covering the period 1990 to 2007. The random regression test day model with EM‐REML was used to estimate variance components, genetic parameters and milk production loss. A decline in milk production was found when temperature and humidity index (THI) exceeded a threshold of 74, also it was associated with the high percentage of Holstein genetics. All variance component estimates increased with THI. The estimate of heritability of test‐day milk yield was 0.231. Dominance variance as a proportion to additive variance (0.035) indicated that non‐additive effects might not be of concern for milk genetics studies in Thai Holstein cattle. Correlations between genetic and permanent environmental effects, for regular conditions and due to heat stress, were ? 0.223 and ? 0.521, respectively. The heritability and genetic correlations from this study show that simultaneous selection for milk production and heat tolerance is possible.     

Genetic and Environmental Effects on the Productivity of Holstein–Friesian Cattle under the Climatic Conditions of Central Sudan

A herd of 370 Holstein–Friesian cows were maintained in Central Sudan, Khartoum for intensive dairy production during the period 1990–1996. The area is characterized by high temperatures during the day and cools down at night, with an average thermal-humidity index (THI) of 74.8. The average adjusted lactation milk yield, milk yield per day, milk yield per day of calving interval and lactation length of the animals in the herd were 5117±123 (SE) kg, 14.7±0.25 kg, 11.3±0.36 kg and 350±8.0 days, respectively. Heifers calved at 25.2±2.3 (SD) months of age. The variation was large, which suggested large environmental fluctuations. Sire variance contributed 1.35% and 19.6% to the total variance in cows and heifers, respectively, while cow within sire contributed 19%. The heritabilities of total lactation yield, 305-day yield, milk per day of lactation, milk per day of calving interval, and lactation length in heifers were 0.78±0.24, 0.36±0.34, 0.39±0.24, 0.23±0.23, and 0.23±0.22, respectively. In cows, the heritability estimates were 0.05±0.24, 0.06±0.24, 0.08±0.24, 0.00 and 0.00 for the same traits, respectively. The repeatabilities of total lactation yield, 305-day yield, milk per day, milk per day of calving interval and lactation length were 0.02±0.03, 0.22±0.03, 0.17±0.02, 0.05±0.02 and 0.00, respectively. Regression analysis showed that, for each unit increase in THI, milk yield decreased by 0.29±0.04 kg. The stress usually caused by the combined effects of temperature and humidity was not severe in this area.     

Impact of diet composition and temperature–humidity index on water and dry matter intake of high‐yielding dairy cows

The temperature–humidity index (THI) is widely used to characterize heat stress in dairy cattle. Diet composition is known to induce variation in metabolic‐associated heat production. However, the relationships between THI and diet are poorly characterized with regard to performance and intake behaviour. Therefore, the objectives were to evaluate the impact of THI on water intake (WI), dry matter intake (DMI) and the frequency of drinking and feeding bouts in lactating dairy cows offered four dietary treatments: each contained 20% grass silage and additionally (i) 20% maize silage, 60% concentrate (M‐HC); (ii) 60% maize silage, 20% concentrate (M‐LC); (iii) 20% pressed beet pulp silage, 60% concentrate (BPS‐HC); or (iv) 60% pressed beet pulp silage, 20% concentrate (BPS‐LC) (DM basis). Individual WI and DMI were recorded from April to July 2013. Furthermore, dietary effects on milk production and reticular pH were estimated. Milk yield was lowest for M‐LC, while energy‐corrected milk was similar for all diets. Milk fat percentage was higher and milk protein amount lower for cows offered both LC diets. Reticular pH below 6.3, 6.0 and 5.8 lasted longest for BPS‐LC. WI was higher for HC diets. However, the frequency of drinking bouts was not influenced by the ration. Lower DMI occurred for BPS‐LC compared to M‐LC. Frequency of feeding bouts was significantly higher for LC diets. THI was significantly related to WI, DMI as well as drinking and feeding bouts. Per increasing THI, WI increased slightly more for LC diets and DMI decreased more for HC diets. Frequency of drinking bouts increased slightly higher for BPS rations per rising THI, while the decrease in feeding bouts was highest for M‐HC. In conclusion, TMR composition and moderate heat stress impacted WI and DMI of dairy cows, while both dietary energy density and ruminal filling might intensify the THI impact.     

自然生产条件下热应激周期变化揭示泌乳中期奶牛出现“热应激乳蛋白降低征”

本试验在连续3年时间里测定了上海地区热应激周期变化对泌乳中期奶牛生产性能和牛奶品质的影响。通过实地测定并计算分析,绘制了上海地区热应激周期变化图谱,揭示了整个热应激周期中不同热应激程度的分布状况。研究对比了自然生产环境下无热应激与中度热应激对奶牛生产性能和牛奶品质的影响,发现中度热应激极显著降低了奶牛采食量、产奶量、乳脂校正乳产量、能量校正乳产量、乳脂率、乳蛋白含量、总固体含量(P<0.01),而且显著增加了乳中尿素氮含量(P<0.05)。在热应激周期变化研究中发现,中度热应激显著升高泌乳奶牛的直肠温度和呼吸频率(P<0.05),而且呼吸频率比直肠温度对热应激变化的反应更快、更敏感。热应激周期变化对奶牛干物质采食量、产奶量的影响取决于热应激程度,2012年整个热应激周期的热应激程度比较低,热应激周期变化对奶牛干物质采食量、产奶量无显著影响(P>0.05),但是2013年热应激程度更加严重,热应激周期变化对奶牛干物质采食量、产奶量产生了极显著影响(P<0.01)。在牛奶品质中,受热应激影响最大的是乳蛋白合成量(P<0.01)。2012年和2013年2个热应激周期变化对其他乳成分含量没有显著影响(P>0.05),但是两年的热应激周期变化都导致乳蛋白含量显著下降(P<0.05)和乳中尿素氮含量显著升高(P<0.05)。尤其值得注意的是,2012年热应激周期变化并没有导致奶牛采食量下降(P>0.05),而且产奶量也没有显著性差异(P>0.05),但是仍然出现了乳蛋白含量下降和乳中尿素氮含量升高(P<0.05)。这表明热应激周期变化改变了泌乳中期奶牛氮代谢的途径,发生了氮营养重分配(repartitioning)现象,而且这种现象不依赖于采食量和产奶量,可以称之为“热应激乳蛋白降低征”(heat-stressed milk protein decrease syndrome,HS-MPD)。