“双蛋白”开发战略与国民膳食结构最佳选择

“双蛋白”开发战略是以植物蛋白质为基础,实行植物蛋白质与动物蛋白质开发并举的战略。以大豆产业和奶业为重点,论述了实施这一开发战略的必要性与有效途径。     

The utilisation of a high level energy/protein diet for lactating Mediterranean buffaloes: Intake capacity and effects on quanti–qualitative milk parameters

The trial was carried out using 14 multiparous buffaloes divided into two groups according to yield in the previous lactation (2653 vs. 2625 kg), number of lactations (4.8 vs. 4.1), live weight (670.6 vs. 657.1 kg), days post-calving (21.6 vs. 23.6 days) and average yield at the on-set of the trial (11.18 vs. 10.90 kg/day). The effects of both feed intake and the quanti–qualitative parameters of the milk yield were evaluated following the ad libitum administration of two diets containing two different forage/concentrate ratios, diet 1 = 48 : 52 (0.94 Milk FU/kg DM, 158.3 g/kg DM of crude protein); diet 2 = 55 : 45 (0.85 Milk FU/kg DM, 144.4 g/kg DM of crude protein). The trial lasted for 114 days, on average from day 23 to 137 of lactation. The dry matter intake for diet 1 was 16.37 kg/day, for diet 2 it was 16.53 kg/day. No significant differences were found with live weight of the animals; however, the buffaloes in group 1 showed gains of 35.0 kg compared to 54.2 kg of those in group 2. A significant difference (P < 0.05) in milk yield favouring group 1 (11.66 vs. 9.42 kg/day) was observed while fat (73.20 vs. 80.08 g/kg) and protein content (43.24 vs. 46.41 g/kg) was higher for group 2. Coagulation data indicated that the milk yield of group 2 showed better coagulation properties (r = 18.35 min, K₂₀ = 3.88 min, A₃₀ = 47.00 mm), than group 1.     

Prevention of milk fever (hypocalcemic paresis puerperalis) by dietary salt supplements.

Twelve cows of 14 given a basic diet supplemented with Na₂GO₃ and NaHCO₃ during four weeks pre partum and one week past partum were attacked by milk fever (hypocalcemic paresis puerperalis), while 12 cows of 13 receiving the same basic diet supplemented with sulfates and chlorides remained healthy. A mixture of CaCl₂, Al₂(SO₄)₃ and MgSO₄ was found to be a convenient prophyllactic supplement.It was found possible to induce and prevent milk fever at successive parturitions in the same cow by altering the dietary conditions.The data give further support to the hypothesis that the alkali alkalinity of the diet is the major factor in induction or prevention of milk fever.     

Quantitative trait loci for milk production and functional traits in two Danish Cattle breeds

Quantitative trait loci (QTL) in Danish Jersey and Danish Red cattle were independently mapped by least squares regression analysis. For Jersey breed, five grandsire families were genotyped for 186 markers on 16 chromosomes (BTAs). Eight traits analysed were milk yield (MY), fat percentage (FP), protein percentage (PP), clinical mastitis (CM), somatic cell score (SCS), maternal stillbirth, maternal calf size (MCS) and maternal calving difficulty. For Red breed, nine grandsire families were genotyped for 166 markers on 18 BTAs. Six traits analysed were MY, FP, PP, CM, SCS and female fertility. Nine and five QTL were detected in Jersey and Red breed, respectively, in across family tests. In Jersey breed, the results indicate QTL for CM and MCS on BTA 3. Additionally, there is an indication of QTL for MCS and FP on BTA 1 and a tentative evidence for a QTL for MY on BTA 26. There is a high risk of detected QTL being false positives. The detected QTL in Jersey breed indicate interesting results from a breeding perspective, but a practical application should await genome-wide association studies.     

Listeriosis in sheep. Listeria monocytogenes excretion and immunological state in sheep in flocks with clinical listeriosis.

The excretion of Listeria monocytogenes (Lm) in the faeces and milk, and humoral immunity against Lm, were examined in a sheep flock with outbreaks of listeric encephalitis and in a flock with outbreaks of listeric abortion. The encephalitis flock consisted of 86 ewes and 20 hoggs, the abortion flock of 45 ewes and 3 hoggs, all of them pregnant. Faecal excretion rate in the encephalitis flock varied from about 25 % in the first part of the indoor season to nearly zero 1 month later, to about 30 % 1 month before lambing and about 15 % at lambing. About 15 % of the animals also excreted Lm in the milk. Lm 4 was the dominating serotype.In the abortion flock about 2/3 of the animals excreted Lm in the faeces and 1/3 in the milk at lambing. All the isolates belonged to serotype 1, which also was isolated from grass silage and strawbedding samples.In the encephalitis flock ewes with ≥ 3 foetuses had a higher excretion rate than the remainder, while no such differences were found in the abortion flock.Antibody titres against Lm in sera and whey in the encephalitis flock were of the same order as in the healthy flock described in an earlier publication (Grønstøl 1979), except that the highest titres were found in the hoggs. Serum titres from the abortion flock after lambing were significantly higher than in the encephalitis flock, while whey titres were of the same order.Treatment with 2-mercapto-ethanol reduced the titres substantially in sera from the abortion flock, indicating that the antibodies belonged to the IgM-fraction, while only a slight reduction was seen after similar treatment of the whey.     

Climatic Changes and Emerging Diseases

The relationships between welfare and udder health indicators were investigated in 120 midlactation Comisana ewes over a 90-day period. The welfare indicators monitored were the humoral response to chicken egg albumin (OVA), the cell-mediated immune response to phytohemagglutinin, and the plasma cortisol levels. Changes in milk components, in somatic cell count (SCC) and in bacterial count, in leukocyte populations and in anti-OVA IgG concentration were used to monitor the ewe udder health. Correlations between welfare and udder health indicators were then tested. The skinfold thickness, representative of the cell-mediated immune response, was correlated positively with the percentage of neutrophils in milk and negatively with the chloride content, the percentage of lymphocytes and anti-OVA IgG concentrations in milk. The plasma antibody titres to OVA, representative of the humoral immune response, correlated positively with the anti-OVA IgG levels in milk and negatively with the lactose content and to the percentage of neutrophils. Plasma cortisol levels correlated positively with the chloride content in milk. Our study demonstrates that information about the immune condition of animals can be successfully achieved by monitoring the immunological responses of the mammary gland. The detection of reliable indicators of animal welfare in milk can help in reducing the stress from animal handling and blood sampling from lactating animals.     

Risk factors for the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) infection on 59 Irish dairy herds

Since 1994, Irish cattle have been exposed to greater risks of acquiring Mycobacterium avium subspecies paratuberculosis (MAP) infection as a consequence of the importation of over 70,000 animals from continental Europe. In recent years, there has been an increase in the number of reported clinical cases of paratuberculosis in Ireland. This study examines the prevalence of factors that promote the introduction and within-herd transmission of Mycobacterium avium subspecies paratuberculosis (MAP) on selected Irish dairy farms in the Cork region, and the association between these factors and the results of MAP screening tests on milk sock filter residue (MFR). A total of 59 dairy farms, selected using non-random methods but apparently free of endemic paratuberculosis, were enrolled into the study. A questionnaire was used to collect data about risk factors for MAP introduction and transmission. The MFR was assessed on six occasions over 24 months for the presence of MAP, using culture and immunomagnetic separation prior to polymerase chain reaction (IMS-PCR). Furthermore, blood samples from all entire male and female animals over one year of age in 20 herds were tested by ELISA. Eighteen (31%) farms had operated as closed herds since 1994, 28 (47%) had purchased from multiple sources and 14 (24%) had either direct or indirect (progeny) contact with imported animals. Milk and colostrum were mixed on 51% of farms, while 88% of farms fed pooled milk. Thirty (51%) herds tested negative to MFR culture and IMS-PCR, 12 (20%) were MFR culture positive, 26 (44%) were IMS-PCR positive and seven (12%) were both culture and IMS-PCR positive. The probability of a positive MFR culture was significantly associated with reduced attendance at calving, and with increased use of individual calf pens and increased (but not significantly) if mulitiple suckling was practised. There was poor agreement between MFR culture and MFR IMS-PCR results, but moderate agreement between MFR culture and ELISA test results. This study highlights a lack of awareness among Irish dairy farmers about the effect of inadequate biosecurity on MAP introduction. Furthermore, within-herd transmission will be facilitated by traditional calf rearing and waste management practices. The findings of viable MAP in the presence of known transmission factors in non-clinically affected herds could be a prelude to long-term problems for the Irish cattle and agri-business generally.     

Detection of staphylococcal enterotoxin A, B, and C in milk by an ELISA procedure

Enterotoxigenic reference strains of Staphylococcus aureus were cultivated in sterile whole and skim milk for 18 h at 37°G. Staphylococcal enterotoxin A, B, and C were detected directly in the milk by an enzyme linked immunosorbent assay (ELISA), sensitive down to 1 ng/ml. Enterotoxins in the range of 1 ng–20 µg/ml milk were detected without any concentration or extraction. Skim and whole milk were almost identical as medium for enterotoxin production.     

干扰CREB基因对奶山羊乳腺上皮细胞脂质合成相关基因表达及甘油三酯合成的影响

旨在筛选奶山羊cAMP应答元件结合蛋白CREB（cAMP response element binding protein）基因的siRNA,揭示干扰该基因后对乳腺上皮细胞中乳脂合成相关基因表达及甘油三酯合成的影响。本研究通过qRT-PCR方法从西农萨能奶山羊乳腺组织中扩增CREB基因完整的CDS区,进行序列分析和不同泌乳时期表达水平分析,合成靶向CREB基因的siRNA,利用荧光定量PCR筛选有效siRNA,并检测脂质合成相关基因的表达,采用试剂盒检测细胞内甘油三酯含量。结果表明：1）克隆得到全长为984 bp的奶山羊CREB基因的CDS区（GenBank登录号：MK158073）,并对其进行生物信息学分析。2）该基因在奶山羊泌乳盛期乳腺组织的表达量为干奶期的1.93倍（P<0.05）。3）成功筛选到靶向CREB基因的有效siRNA,干扰效率为72%（P<0.01）;并将其在奶山羊乳腺上皮细胞进行转染,通过qRT-PCR检测脂质合成相关基因的表达,与对照组相比,干扰CREB基因后显著抑制了FASN、ACACA、SCD1、FABP3、LPL、CPT1B、GPAM和DGAT2基因表达量（P<0.05）,并显著增加了HSL基因表达量（P<0.05）;且细胞内甘油三酯含量被显著下调（P<0.05）。综上所述,CREB基因在奶山羊原代乳腺上皮细胞中很可能通过调控脂质代谢相关基因的表达及甘油三酯含量对山羊的乳脂合成过程发挥重要作用。     

QuEChERS-分散固相萃取-气相色谱-质谱法测定牛乳中喹氧灵残留

建立气相色谱-质谱联用技术测定牛乳中喹氧灵残留量的检测方法。以乙腈作为提取剂,借助分散固相萃取(填料为C18和N-丙基乙二胺)作为净化手段,经Agilent HP-5MS色谱柱分离,通过基质匹配外标法校正定量。结果表明:目标物在0.00~1.00μg/mL范围内线性关系良好,R2>0.998 7,样品基质在3个添加水平(5、10、20μg/kg)下的回收率为83.2%~100.8%,相对标准偏差为2.1%~4.3%,定量限为5μg/kg;该方法步骤简单、可靠、稳定,可以推广应用于牛乳中喹氧灵含量的测定;采用该方法对75个奶户牛乳中喹氧灵含量进行测定,结果均小于国家限量值。