乳源性生物活性肽生物学作用及其应用

乳中含有大量不同活性的生物活性肽。这些肽或自然存在于乳中或源于乳蛋白水解后的产物。在乳中已发现自然态存在的活性肽包括ＥＧＦ、ＴＧＦ、ＮＧＦ、ＩＧＦ－Ⅰ、ＩＧＦ－Ⅱ、胰岛素等，其浓度在初乳中一般比较高，而且因新生动物胃肠道蛋白酶的活性较低，乳中还存在着蛋白酶抑制剂，因此这些乳源性生物活性肽在新生幼畜胃肠道中比较稳定。灌（口）服ＥＧＦ、纱或ＩＧＦ－Ⅰ能刺激新生幼仔胃肠道的成熟，推测初乳源生物活性肽在调     

The polymorphism in the β4-defensin gene and its association with production and somatic cell count in Holstein-Friesian cows

The aim of this study was to find a polymorphism of the bovine β4‐defensin gene and search for its association with milk yield and composition and with the somatic cell count in milk. The data were from the years 1999 to 2004 on 212 Holstein‐Friesian (HF) dairy cows, descended from 70 sires. Based on the sequence of the bovine β4‐defensin gene (GenBank no. AF008307 ) the primers were designed for the amplification of the 924‐bp or 393‐bp long fragments. The 924‐bp long fragment was sequenced and the sequence was compared with that available in the GenBank. Ten putative nucleotide sequence polymorphisms were found in the intron of the bovine β4‐defensin gene. One of them, a C→T transition at position 2239, that creates a new NlaIII (Hin1II) restriction site, was genotyped with polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) in a cohort of 212 HF cows. The CC genotype was the most common (72%). The heterozygous CT genotype was found in 26% of the genotyped cows and four cows (2%) were TT homozygotes. In order to determine the relationship between the polymorphism of the β4‐defensin gene and milk production traits a multi‐trait repeatability test‐day animal model was used. The Derivative‐free Multivariate analysis program was used for computation. The differences between estimates for genotypes were checked using Student's t‐test. The model included the animal genotype, year‐season of calving and parity as fixed effects and the animal additive genetic effect and permanent environmental effect of individual cows as well as dates of the tests as random effects. Significant associations were found between the RFLP‐NlaIII and milk fat, protein and lactose contents. Also, a significant effect was shown of the defensin genotype on the somatic cell count in the milk.     

基于客户端/服务端结构的牧场奶源数字化管理系统的构建

根据牧场奶源管理的需要，采用NET软件平台，N层体系结构及客户端/服务端（client/server，C/S）模式，构建了牧场奶源管理系统，该系统可以实现牛群和个体等一般信息的管理，在此基础之上，实现了以奶源管理为中心，并可以实现产奶各项生产指标分析和统计的功能。为了实现牧场奶源管理的计算机化、规范化、数据化、透明化,为牧场企业资源计划（enterprise resource planning，ERP）管理提供数据支持。     

原料奶优良风味保持体系的建立及应用研究

本文旨在建立保持原料奶优良风味的危害分析关键控制点(HACCP)体系并研究其可行性。以呼和浩特市郊区某奶牛养殖场1 000头泌乳牛为试验动物,试验期90 d,其中前30天为对照期,采用常规饲喂和管理方式,后60天为正试期,采用HACCP体系。测定和分析原料奶的理化指标、风味物质浓度和风味强度以及感官评分的变化。结果表明:1)执行HACCP体系后,原料奶的乳脂、乳蛋白、乳糖和干物质的比率以及酸度、抗生素指标变化均不显著(P>0.05),但其中酸度趋于降低,抗生素指标趋于增高;细菌总数显著降低(P<0.05);产奶量显著提高(P<0.05);2)执行体系前后在挥发性风味物质种类及浓度上存在差异,导致了原料奶风味的差异,感官评价均属于1级奶,执行体系后感官评分均有所提高(P>0.05);3)执行体系后各来源的风味强度指数均大于执行体系前;挤奶过程及贮藏过程对原料奶风味的影响较大。本文建立的保持原料奶优良风味的HACCP体系,该体系不仅可保持原料奶的良好风味,而且可提高原料奶的质量。     

应用脂肪粒径预测UHT乳货架期的研究

以市售UHT乳为研究对象,应用Arrhenius模型通过对脂肪粒径的分析,预测UHT乳的货架期.UHT乳分别在25℃、45℃环境下恒温储藏,并定期随机抽样进行感官检验和脂肪粒径含量测定.应用Arrhenius方法分析用脂肪粒径含量来预测样品货架期,并建立了模型.     

Some Factors Affecting Variation in Milk Yield in Crossbred Dairy Cows on Smallholder Farms in North-East Tanzania

A 2-year longitudinal survey was carried out to investigate factors affecting milk yield in crossbred cows on smallholder farms in and around an urban centre. Sixty farms were visited at approximately 2-week intervals and details of milk yield, body condition score (BCS) and heart girth measurements were collected. Fifteen farms were within the town (U), 23 farms were approximately 5 km from town (SU), and 22 farms approximately 10 km from town (PU). Sources of variation in milk yield were investigated using a general linear model by a stepwise forward selection and backward elimination approach to judge important independent variables. Factors considered for the first step of formulation of the model included location (PU, SU and U), calving season, BCS at calving, at 3 months postpartum and at 6 months postpartum, calving year, herd size category, source of labour (hired and family labour), calf rearing method (bucket and partial suckling) and parity number of the cow. Daily milk yield (including milk sucked by calves) was determined by calving year (p < 0.0001), calf rearing method (p = 0.044) and BCS at calving (p < 0.0001). Only BCS at calving contributed to variation in volume of milk sucked by the calf, lactation length and lactation milk yield. BCS at 3 months after calving was improved on farms where labour was hired (p = 0.041) and BCS change from calving to 6 months was more than twice as likely to be negative on U than SU and PU farms. It was concluded that milk production was predominantly associated with BCS at calving, lactation milk yield increasing quadratically from score 1 to 3. BCS at calving may provide a simple, single indicator of the nutritional status of a cow population.     

Replacement Value of Undecorticated Sunflower Meal as a Supplement for Milk Production by Crossbred Cows and Buffaloes in the Northern Plains of India

The replacement value of undecorticated sunflower meal (SFM) in the diets of dairy animals was assessed on-station and on-farm. Eighteen primiparous crossbred (Bos taurus×Bos indicus) cows (350.4±8.84 kg), randomly allocated to three groups, were used in the on-station study. The animals were fed on either a conventional concentrate supplement (control) or on an experimental concentrate, in which SFM replaced 25% (SFM-25) or 50% (SFM-50) of the CP in the control supplement. Green oats (Avena sativa) were supplied ad libitum. A metabolism trial conducted following 60 days of experimental feeding revealed that the intakes of DM, DCP and TDN were similar among the groups. The digestibilities of OM, CP, EE, NDF and ADF were also without significant differences. All the groups were in positive nitrogen balance. Inclusion of SFM at either level had no effect on the intake, excretion or retention of nitrogen. The daily milk yield and its composition did not differ among the dietary treatments. Moreover, the efficiency of utilization of DOM and TDN for FCM production tended to reflect, although non-significantly, increasing levels of SFM inclusion. In the on-farm study, seven multiparous milking buffaloes belonging to six farmers were used to assess the effect of replacing 20% of the CP of the conventional supplement with SFM, in a predominantly crop residue-based diet. The study continued for 4 months and revealed that the average daily feed intake and milk production was similar in the control and SFM-fed groups. It was concluded that SFM can be effectively utilized as a cheaper replacement for costly oil cakes and wheat bran for economic milk production by smallholder farmers.     

In Vitro Effects of Acellular Milk on the Bactericidal Components of Caprine Polymorphonuclear Neutrophils

The effects of acellular milk on the activity of the microbicidal cationic enzymes of the polymorphonuclear cells of goats were studied in an attempt to explain the phenomenon by which PMN functions fail in mastitis. Assays were undertaken on the myeloperoxidase, lysozyme and elastase activities in a polymorphonuclear cell (PMN) lysate, both in the presence and absence of acellular milk from homologous species. There was a significant decrease (p<0.05) in the activity of lysozyme, myeloperoxidase and elastase in the presence of acellular milk. Superoxide and H₂O₂ production following activation of caprine PMNs by lipopolysaccharide (LPS) was significantly reduced (p<0.05) in the presence of acellular milk. Thus, the microbicidal function of PMNs is significantly impaired in the presence of acellular milk and this may contribute to the development of mastitis in dairy animals.     

加热大豆粕对高产奶牛血液代谢产物、产乳量和乳成分的影响

选用10头经产荷斯坦乳牛分为对照和试验组(n=5),以二乘反转法,研究了加热大豆粕对奶牛血液代谢产物、产乳量和乳成分的影响。试验组日粮用加热大豆粕替代了对照组日粮中的生大豆粕,使RUP比例提高3.9%,两组日粮其他组成和营养成分基本相同。结果表明,试验组牛血浆葡萄糖浓度有下降趋势(P<0.1),尿素氮、总游离氨基酸和必须氨基酸浓度两组间均无显著差异(P<0.1);两组牛干物质采食量无明显差异;试验组乳量、4%脂肪校正乳量、乳糖和无脂固形物产量显著增加(P<0.05),分别比对照组增加7.1%(2.3kg/d)、6.1%(1.9k9/d)、80g/d(5.8%)和180g/d(6.8%);试验组乳蛋白质和乳脂肪产量增加30g/d(3.3%)和40g/d(5.0%),但无显著差异(P>0.1);试验组与对照组比较乳蛋白质率低0.09%单位(P<0.1),乳脂率、乳糖率和无脂固形物率低0.06～0.08%单位(P>0.1),乳脂中脂肪酸比例无明显变化。以上结果显示:用加热大豆粕替代高产奶牛泌乳前期日粮中生豆粕可增加产奶量。但是,增加产奶量的同时要改善乳蛋白质为主的乳成分含量,需要平衡地改善能量、蛋白质甚至葡萄糖营养的供给状况。     

链霉素在牛奶中残留的微生物学检测方法

建立了链霉素在牛奶中残留的微生物学检测方法.样品用10%(W/V)三氯乙酸提取,通过冷冻离心使牛奶中残留的链霉素得到分离,再用枯草芽孢杆菌作为检定菌进行含量测定.结果显示,链霉素在0.10～3. 20 μg/mL的浓度范围内具有良好线性关系(r=0.998 1),牛奶中3种添加浓度0.20、0.80、1.60 μg/g的平均回收率为97.6%(n=9),RSD分别为1.6 %、3.7 %、1.2 %(n=3).