Evaluation of a Rapid Method for the Determination of Urea in Cow’S Milk

A rapid method for the determination of urea in milk was evaluated. The method employed was a urease/glutamate dehydrogenase procedure where the decrease in absorbante of NADH is monitored spectrophotometrically at 340 nm. The repeatability expressed as a coefficient of variation, was 1.4 % and 0.8 % for whole milk and skim milk, respectively. The accuracy of the method for urea determinations in whole milk was satisfactory (coefficient of variation, 2.6 %). Adding the preservative bronopol (0.02%) to the milk or freezing of the milk samples for one week did not alter urea levels significantly (P > 0.05). The storage of preserved whole milk in a refrigerator for 14 days, however, increased milk urea levels measured by 3.1 % (P < 0.001).It was concluded that the method evaluated is simple, rapid (40–50 samples/h) and yields reliable results also when whole milk is used. Since the determination of milk urea may be useful in assessing the feeding of energy and protein, the method is suitable for integration in the existing milk recording system in Sweden.     

Diurnal variation and the effect of feed restriction on plasma and milk metabolites in TMR-fed dairy cows

The objective was to study the diurnal variation in metabolites in plasma and milk of dairy cows fed total mixed rations (TMR) with a low-energy (LE) or high-energy content (HE) expected to give a minor and a major diurnal variation, respectively. Further, the purpose was to quantify and compare the responses in plasma and milk parameters when cows changed from ad libitum to restrictive feeding. Eight multiparous, early-lactating Danish Holstein cows were used in a cross-over design with two consecutive 14-day periods. Blood and milk samples were collected hourly on day 11 of each period and on days 12-14 of each period, the cows were fed restrictively (65% of ad libitum dry-matter intake). The concentration of beta-hydroxybutyrate (BHB) in plasma was significantly higher in the evening for cows fed the HE TMR, than for cows fed the LE TMR. There was a significant diurnal variation in BHB in milk, with the highest concentrations between milkings and the lowest concentrations at milking. Non-esterified fatty acids (NEFA) in plasma showed significant diurnal variation that was caused by high concentrations in the morning. Plasma glucose did not show any diurnal variation. It has been argued that feeding a TMR removes diurnal changes related to feeding, which is contrary to earlier diurnal studies where concentrates have been fed twice daily. Feed restriction increased (P < 0.001) NEFA and BHB in plasma by 121 and 90%, respectively, while the glucose concentration decreased (P < 0.001) by 19%. Milk concentrations of BHB, citrate and fat increased (P < 0.001) by 163, 11 and 26%, respectively, because of feed restriction, while there were no changes in milk protein and lactose. The relatively high increase in BHB during feed restriction suggests that BHB is more advantageous as a milk indicator of metabolic status in dairy cows than citrate and fat.     

脂肪水平对早期断奶犊牛生长性能及血清生化指标的影响

早期断奶犊牛饲喂不同脂肪含量代乳品,研究脂肪水平对犊牛生长性能、血清生化指标及饲料进食量的影响,为犊牛生长规律和脂肪需要提供科学依据,为实际生产中犊牛早期断奶和培育提供技术指导。试验选取12头新生荷斯坦公犊牛,分为EE9、EE13、EE17 3组,每组４头,分别饲喂蛋白质水平相同、脂肪含量为9%、13%及17%的3种代乳品。每日记录犊牛开食料的采食情况,并于犊牛10、20、30、40、50、60日龄清晨空腹测定犊牛体重及体尺指标,同时采集犊牛的血液样本进行分析。研究结果表明,3组犊牛哺乳期的饲料日进食量分别为706.9、666.9、569.3 g;10~60日龄的平均日增重分别为498、544、488 g,EE13组犊牛日增重高于EE9、EE17组的犊牛;犊牛60日龄时,EE13组犊牛的体高、体斜长及管围均高于其它2组。血清尿素氮、血糖、甘油三酯的水平不受代乳品脂肪含量的影响,但日龄对哺乳期犊牛甘油三酯含量的影响差异显著(P<0.05)。随日龄的增加,犊牛的生长速度和饲料的进食量逐渐增加,低脂肪的代乳品(EE9)不能满足犊牛的能量需要,高脂肪的代乳品（EE17）抑制了犊牛对开食料的采食量,饲喂脂肪含量13％的代乳品（EE13）对犊牛生长发育优于其它2组。脂肪含量对犊牛血清生化指标的影响不显著。     

Effects of supplement feeding order on lactation, diurnal variation of ruminal ammonia and urea in the blood and milk of dairy cows

The present study examined the effects of feeding order of grain and protein supplements on ruminal nitrogen (N) loss through the diurnal variation of ruminal ammonia N and urea N in the blood and milk of dairy cows. Three ruminally fistulated cows were used in a 3 × 3 Latin square arrangement of treatments; that is, grain supplement fed at the first feed and then the protein supplement at the second (GS‐1st), protein supplement fed first and then the grain supplement (PS‐1st), and the grain and protein supplements mixed and divided into equal portions fed at each supplement feeding time (GP‐mix). No differences in the lactation parameters were observed among the treatments. In GS‐1st treatment, the increase in the concentration of ruminal ammonia N was inhibited after feeding, and the concentration was lower (P < 0.05) than with the other treatments 1–2 h after basal feeding. The concentrations of urea N in the blood and milk with the GS‐1st treatment were the lowest of all treatments throughout the sampling times, and were lower (P < 0.05) than with the GP‐mix treatment except for blood levels 1 h after basal feeding. The results suggest that grain feeding before protein feeding can reduce ruminal N loss.     

云南水牛乳成分分析及乳能量预测模型的建立

本试验旨在分析水牛乳成分中乳脂肪、乳蛋白、乳糖和乳尿素氮含量及其与乳能量的相关性,建立产奶净能的预测模型,用于奶水牛泌乳期科学的饲养管理。试验采取云南省主要奶水牛养殖场和养殖小区的2014—2015年9—12月份送达昆明市奶牛生产性能测定中心的304个原料乳样本,水牛乳的乳成分由昆明市奶牛生产性能测定中心用MilkoScan FT+FC乳成分体细胞联用仪和MilkoScan FT 120乳成分分析仪测定,鲜乳经真空干燥箱恒温烘干后用氧弹式热量计测定乳能量。结果表明:乳脂肪、乳蛋白、乳糖、乳尿素氮、乳总固形物含量和乳能量分别为6.45%、4.55%、5.31%、13.60 mg/dL、18.77%和4.02 MJ/kg;乳能量分别与乳脂肪和乳蛋白含量呈现极显著正相关(r=0.896 0、r=0.563 0,P0.01),乳能量受乳脂肪和乳蛋白含量的影响较大。分别以乳脂肪(F),乳脂肪和乳蛋白(F和P),乳脂肪、乳蛋白和乳糖(F、P和La),乳脂肪、乳蛋白、乳糖和乳尿素氮含量(F、P、La和MUN)为预测因子,建立的预测乳能量(E)的一元、二元、三元及四元回归方程的拟合度均在0.90以上,方程分别为:E=0.388F+1.540(R~2=0.933 6,P0.01);E=0.373F+0.221P+0.460(R~2=0.926 7,P0.01);E=0.396F+0.186P+0.105La-0.104(R~2=0.954 0,P0.01);E=0.397F+0.187P+0.106La+0.002MUN-0.146(R~2=0.958 0,P0.01)。由此可见,可通过水牛乳中的乳脂肪、乳蛋白、乳糖及乳尿素氮含量预测水牛乳产奶净能。     

日粮中添加植物提取物对泌乳初期奶牛生产性能的影响

选择100头健康泌乳初期奶牛,按照产量、泌乳天数、胎次基本一致原则随机分成对照组和试验组,每组各50头,进行植物提取物＂NE300＂对产奶量和乳成份的影响研究。结果表明：植物提取物＂NE300＂作为一种瘤胃调节剂,有促进奶产量、乳脂肪含量、乳蛋白含量增加的趋势,同时有降低乳体细胞数量、乳尿素氮含量的趋势。     

乳尿素氮测定的研究进展

综述了国内外测定乳尿素氮浓度的情况,评价了国内外测定乳尿素氮的优缺点以及乳成分和:样保存条件对乳尿素氮浓度测定的影响.     

不同品种泌乳母马不同泌乳月产奶量及乳成分的比较

[目的]研究伊犁马和哈萨克马泌乳母马在不同泌乳月产奶量及乳成分的差异,为开发利用伊犁马和哈萨克马乳用特性提供参考。[方法]随机选择年龄和胎次相近、产驹时间接近、健康的伊犁母马和哈萨克母马各12匹,在日粮营养水平和饲养管理水平相同的条件下,记录2个品种母马在泌乳30、60、90 d的产奶量;采集乳样,测定2个品种母马不同泌乳时间的乳中体细胞数、乳脂率、乳蛋白率、乳糖率和总固形物含量。[结果]泌乳30 d时,哈萨克马的产奶量高于伊犁马（P>0.05）,乳脂率极显著（P<0.01）高于伊犁马,乳中体细胞数显著（P<0.05）高于伊犁马,其他乳成分指标高于伊犁马（P>0.05）。泌乳60 d时,伊犁马的产奶量和乳糖率极显著（P<0.01）高于哈萨克马,乳脂率和乳蛋白率高于哈萨克马（P>0.05）,乳中体细胞数和总固形物含量低于哈萨克马（P>0.05）。泌乳90 d时,伊犁马的产奶量显著（P<0.05）高于哈萨克马,乳糖率、总固形物含量极显著（P<0.01）高于哈萨克马,乳脂率和乳体细胞数极显著（P<0.01）低于哈萨克马,乳蛋白率高于哈萨克马（P>0.05）。[结论]泌乳初期（30 d）,哈萨克马的产奶量和乳营养成分含量高于伊犁马;泌乳中期（60、90 d）,伊犁马的泌乳性能整体优于哈萨克马。在观察期内,哈萨克马的乳体细胞数大于伊犁马。     

Relationships between daily, morning, evening and peak yield and persistency in Turkish Saanen goats

A matrix of persistency values is given instead of one value of persistency or persistency values based on succeeding test days. Overall, the persistency matrix of morning milk had higher values than the persistency matrix of evening milk. As the distance between the test days increased, the correlations dramatically decreased. The effects of morning milk yield b = 0.23 (P < 0.01) on standard deviation of morning and evening milk yield and on peak the milk yield was higher compared to the evening daily milk yield b = 0.03 (P = 0.05) and the total daily milk yield 0.10 (P < 0.01). Increased persistency means that the lactation curve may be flatter. Since the peak value of morning milk (1597 mL) was lower than evening milk (1799 mL), and morning milk was more persistent than evening milk, morning milk can be said to contribute more to the flatness of the lactation curve. Overall, the morning milk volume (938 mL) was larger than the evening milk volume (835 mL). A 3D plot of peak milk versus morning and evening milk yield indicated that increasing the evening milk yield increases the peak yield while the morning milk yield holds the peak value lower and the curve stable.     

萨能奶山羊乳体细胞数与乳汁成分变化的研究

本研究采用DHI检测方法对云南高原饲养的萨能奶山羊进行体细胞数统计和相关分析,探讨奶山羊体细胞数对羊奶主要成分及含量的影响。结果表明,萨能奶山羊乳体细胞数与乳脂率呈正相关(P=0.141),与乳蛋白率呈极显著正相关(P<0.01),与乳糖含量呈极显著负相关(P<0.01),与总固形物含量呈显著正相关(P<0.05),与尿素氮含量呈极显著负相关(P<0.01)。乳汁体细胞数的增加对羊乳的品质产生很大影响,造成羊乳蛋白、脂肪含量和总固形物含量上升;乳糖和非蛋白氮含量降低。从多种因素考虑,6月份所测得的体细胞数和乳成分含量可作为萨能奶山羊乳品质质量标准的参考。     

牛奶增产剂—尿素营养舔块饲喂试验

用青海省畜牧兽医科学院研制的尿素营养舔块,在西宁奶牛场进行了40天的奶牛饲喂试验。试验结果:奶牛对尿素营养舔块适口性良好,无毒、无害、无副作用,平均日舔食1.88kg,增乳效果明显,试验组产奶量比对照组增加4.1kg/(头·d),提高24.96％。     

乳酸菌发酵青贮对奶牛产奶量及乳成分的影响

利用从优质青贮饲料中分离鉴定并筛选的2株乳酸菌进行全株玉米的青贮中试试验,玉米青贮30天即可成熟。感官评定的结果表明,乳酸菌处理组的青贮饲料品质比对照组显著提高(p<0.05)饲喂添加乳酸菌的玉米青贮饲料对奶牛的产奶量没有显著影响,但是牛乳中蛋白质和非脂乳固体的含量也显著提高(p<0.05),而对乳脂肪的含量没有影响。     

饲粮粗蛋白质水平对泌乳水牛产奶量及氮代谢的影响

本试验旨在研究饲粮粗蛋白质水平对泌乳水牛产奶量及氮代谢的影响。试验采用４×４拉丁方试验设计,选用 １６头体况良好、上期泌乳量相近、产犊胎次 ２～３胎、健康的泌乳前期水牛,随机分为４组,进行动物饲养试验和消化代谢试验。将４组泌乳水牛随机分配到４个梯度的饲粮粗蛋白质水平组,即 １６．０％、１５．２％、１４．４％、１３．６％ ４个组,每组 ４头,进行 ４期饲养试验,每期 ２１ｄ,共 ８４ｄ。按照 ４×４拉丁方设计给各期各组泌乳水牛饲喂不同粗蛋白质水平的饲粮,每期试验预试期 ７ｄ。在第 ２期和第 ４期饲养试验的最后 ４ｄ开展 ２期氮消化代谢试验。结果表明,总采食氮、可消化氮、乳氮／进食氮以及氮表观消化率在部分组间差异显著（Ｐ＜０．０５）;乳氮、粪氮、尿氮在各组间差异不显著（Ｐ＞０．０５）。饲喂不同粗蛋白质水平饲粮对水牛产奶量、乳蛋白率、乳脂率、乳非脂固形物率和乳糖率均无显著影响（Ｐ＞０．０５）。血清总蛋白和尿素氮含量各组间差异不显著（Ｐ＞０．０５）。以试验期间进食氮水平（ｇ／ｄ）为横坐标（ｘ）,标准乳产量（ｋｇ／ｄ）为纵坐标（ｙ）,获得进食氮水平与标准乳产量的二次曲线关系,即 ｙ＝－０．００１６ｘ２＋０．９５５６ｘ－１２９．９１。由此可见,饲粮粗蛋白质水平对泌乳水牛生产性能及血液生化指标影响不显著,根据进食氮水平与标准乳产量的二次曲线关系可得,当进食氮水平为 ２９８．６２５ｇ／ｄ时,得到水牛标准乳产量最大值为 １２．７７３ｋｇ／ｄ。     

Milk compositional changes of Laoshan goat milk from partum up to 261 days postpartum

Despite the global increasing demand for goat milk, no data exist on the nutrient potential of Laoshan goat milk and limited information exists on its composition according to lactation period. In this study, the measured indicators, including dry matter, protein, immunoglobulin, lactoferrin, fat, ash, lactose, calcium, titratable acidity and pH from partum to 261 days postpartum of Laoshan goat milk, followed the same law of change. There was a significant difference over the first 5 days postpartum, after which no significant difference was observed until days 225 postpartum. However, days 255 postpartum was like a turning point, after which their values showed either an increasing or decreasing trend. We concluded that the colostrum for Laoshan dairy goat was considered from days 1 to 5 postpartum and after 5 days it was as transitioned to milk when all measured parameters were according to the normal ranges as described in this study. This work provided updated information on the current nutritive characteristics of Laoshan goat milk, which may be of importance in the fields of milk production, food technology, and nutritional mutual replenishment.     

饲料蛋白质组分对泌乳奶牛乳脂率和乳蛋白的影响

本试验研究采用粗蛋白质相同而蛋白质组分水平不同的四种日粮(日粮粗蛋白质中瘤胃未降解蛋白质(RUP)比例由35.9%逐步提高到40.9%,其他营养成分基本保持一致),选择32头处于中产水平的荷斯坦奶牛,根据产奶量、胎次和泌乳日龄按配对法随机分为四组,研究了不同蛋白质组分水平的日粮对奶牛乳脂率、乳蛋白率和乳蛋白质产量的影响规律。结果表明,粗蛋白质相同而蛋白质组分水平不同的日粮对奶牛乳脂率、乳蛋白率和乳蛋白产量没有显著的影响(P>0.05),但乳脂率有下降的趋势,乳蛋白产量有增加的趋势。     

The effect of breed, stage of lactation and parity on sheep milk fat CLA content under the same feeding practices

The cis-9, trans-11 C_18:2 (CLA) content in milk fat of four pure sheep breeds (Awassi, Lacaune, Friesland and Chios) was examined. All sheep were kept indoors all year round under the same feeding practices, without any grazing at all. Sheep nutrition was based on alfalfa hay and concentrates. A total of 237 individual milk samples were collected at three sampling times (December, January and March) from sheep of different parity and different days in milk, for CLA determination. The results showed that: (a) there was a large variation in milk fat CLA content among individuals consuming the same diet, (b) the CLA content of milk fat was lower in Friesland breed, compared to the other three breeds but without any significant difference among the four sheep breeds, (c) the CLA content of milk fat was not affected by ewes parity or days in milk, (d) there was a negative but not significant correlation between milk fat and CLA concentration, (e) the CLA content of milk fat was not correlated with milk yield. In conclusion, no others factors, such as breed, parity, days in milk, etc., can affect CLA content in milk fat, which means that the dietary ones remain the sovereign factors explaining the highest proportion of CLA content variability in sheep milk fat.     

Effect of cow-specific factors and feeding frequency of concentrate on diurnal variations of blood metabolites in dairy cows

OBJECTIVE: To determine the effect of feeding frequency and cow-specific factors on diurnal variations of blood metabolites concentrations. ANIMALS: 40 dairy cows from 2 herds. PROCEDURE: Each herd was fed concentrate at a specific feeding frequency (automatic vs twice daily). Blood samples were collected 4 times daily. Plasma concentrations of glucose, nonesterified fatty acids (NEFA), and beta-hydroxybutyrate (BHBA) were analyzed, and concentrations of urea, cholesterol, and total protein (TP) were determined in serum samples. A multivariate repeated-measures ANOVA was used to test the effect of time, feeding frequency, production group, parity, days after parturition, and daily milk yield on diurnal variations of metabolites. RESULTS: Concentrations of glucose, BHBA, and urea remained relatively constant in the herd that was fed by use of automatic distribution of concentrate; however, significant diurnal patterns were detected in the herd fed only twice daily. Only slight differences in glucose and urea concentrations were detected between high- and low-producing cows, but concentration of BHBA was significantly influenced by number of days in lactation. In contrast, diurnal variations in NEFA and cholesterol concentrations were similar between the 2 herds but differed with regard to production group. Concentrations of TP did not have relevant diurnal patterns and did not differ between production groups. CONCLUSIONS AND CLINICAL RELEVANCE: Diurnal variations and feeding frequency affect glucose, BHBA, and urea concentrations in cows. In contrast, concentrations of NEFA, cholesterol, and TP appear to be less sensitive to time of sample collection. Feeding frequency, composition of feed, or both, have a major impact on blood metabolites concentrations.     

不同季节、地域及养殖方式对原料乳成分的影响研究

原料乳的质量是乳制品质量与安全的关键因素。我国奶牛养殖分布于不同的区域,不同饲养方式下的原料乳质量差异较大。本研究对不同养殖方式、不同季节和不同区域的原料乳成份进行了系统分析,建立了不同基地牛乳质量数据库,对控制原料乳质量具有重要意义。     

影响西农萨能奶山羊产奶性状的非遗传因素分析

本试验旨在探究母羊出生年度、季节、胎次、泌乳阶段4个固定效应对西农萨能奶山羊产奶性状的影响。以西北农林科技大学萨能羊原种场2006-2018年的645只泌乳母羊为研究对象,每月采集乳样1次,采样日早、晚各采集1次,将两次乳样等比例混合后,采用乳成分分析仪测定乳脂率、乳蛋白率、乳糖率、总脂固形物、非脂固形物、密度、冰点和酸度共8个指标,结合羊场产奶量记录,采用固定效应模型,通过SAS 9.4软件进行表型的描述性统计分析,再采用GLM模型进行固定效应对产奶性状的影响分析。结果表明,西农萨能奶山羊平均300 d产奶量为507.67 kg,乳脂率为3.58%,乳蛋白率为3.20%,乳糖率为4.19%;总固形物含量为12.21%,非脂固形物含量为8.46%;出生年度、胎次对产奶量影响极显著（P<0.01）,出生季节对产奶量影响不显著（P>0.05）;泌乳阶段、出生年度对乳脂率等8个乳成分性状均有极显著影响（P<0.01）,胎次对除乳蛋白率和总固形物的其他6个乳成分指标均存在极显著影响（P<0.01）。综合以上试验结果,胎次及泌乳阶段是影响西农萨能奶山羊产奶性状的两种主要非遗传因素,第3、4胎母羊产奶性能最佳,泌乳早期的乳品质更优,揭示了对种群进行良种选育工作和羊饲养管理的重要性,也为后期进行奶山羊经济性状遗传评估和群体遗传改良提供理论基础。     

Cow level sampling factors affecting analysis and interpretation of milk urea concentrations in 2 dairy herds.

The goals of this study were to determine the influence of the variations among udder quarters, the somatic cell count, the time of sampling during the day, sample conservation, and centrifugation on milk urea (UREA) concentrations, and to propose a sample collection procedure for herds that are not on a Dairy Herd Improvement (DHI) program. Forty cows from 2 herds with different feeding practices were randomly selected. The quarter sampled and the somatic cell count did not significantly influence UREA concentrations. Milk urea concentrations were highest in the morning. The diurnal pattern was not influenced by intrinsic factors like parity, days postpartum, or daily milk yield. The UREA concentrations were significantly higher after refrigeration for one week (mean UREA change = +0.41 +/- 0.24 mmol/L, P = 0.0001) and freezing for one month (mean UREA change = +1.52 +/- 1.25 mmol/L, P = 0.0001). Urea concentrations were slightly higher in lactoserum than in whole milk (mean UREA difference = +0.17 +/- 0.24 mmol/L, P = 0.0001). Although this study included only 2 herds and does not allow extrapolation, differences were found in the diurnal pattern of UREA in these 2 herds, which possibly reflect differences in feeding strategy. With consideration of these results, a 6-point sampling procedure for herds that are not on a DHI program is proposed.