A total of 12 mature healthy Holstein dairy cows of the nearly body weight （580±30） kg, milk yield （22.5±2.8） kg in the early stages of lactation were selected in this experiment. The cows were randomly ...A total of 12 mature healthy Holstein dairy cows of the nearly body weight （580±30） kg, milk yield （22.5±2.8） kg in the early stages of lactation were selected in this experiment. The cows were randomly divided into 2 groups, every group had 6 cows, every group had 6 repeats, and every repeat had 1 cow. Added 20 g protected methionine in earlier lactating cow food every day. The results showed that protected methionine increased milk yield by 10.83%, testing group milk yield was significantly different than that of control （P〈0.05）; protected methionine increased milk fat by 5.98%, testing group milk fat was significantly different than that of control （P〈0.05）; Milk protein increased by 2.15%, but bad insignificantly different （P〉0.05）; dry matter of milk had the tendency of decrease, but had insignificant difference （P〉0.05）.展开更多
The probiotic Bacillus subtilis （B. subtilis） was widely applied in animal production as feed additive. Lysine （Lys） and methionine （Met） were the two most important limiting amino acids in livestock animal feed...The probiotic Bacillus subtilis （B. subtilis） was widely applied in animal production as feed additive. Lysine （Lys） and methionine （Met） were the two most important limiting amino acids in livestock animal feed. Raising Lys and Met contents in B. subtilis would provide better effects for animal production and save Lys and Met supplements. We still didn＇t know whether Lys- rich and Met-rich protein genes from plants could be transfected into B. subtilis and expressed at a high level so as to improve animal production, such as milk production as an additional diet. The Lys-rich protein gene （Cflr） and Met-rich 10 ku-δ Zein were cloned from pepper anther and maize endosperm, respectively. Then they were constructed into plasmids individually and successfully cotransfected into B. subtilis. Upon IPTG induction, mRNAs and protein expressions could be observed. Lys and Met contents in the fermentation broth were raised by 65.92% and 46.39%, respectively. After feeding 200 g and 400 g· cow^-1· d^-1, transgenic B. subtilis fermentation broth, the milk yield, milk protein and milk fat contents all significantly increased. The Lys-rich protein gene （Cflr） and Met-rich 10 ku-δ Zein were successfully transfected into B. subtilis. Contents of Lys and Met in the transgenic B. subalis obviously raised and the fermentation broth of the transgenic bacteria could effectively improve milk yield and quality.展开更多
The present study was conducted in four districts of Punjab Province to examine the attitude of milk producers and milk collection agents toward compliance of milk quality and safety parameters. In current scenario, t...The present study was conducted in four districts of Punjab Province to examine the attitude of milk producers and milk collection agents toward compliance of milk quality and safety parameters. In current scenario, the attitude of consumers for safe food in accordance to quality standards is ever increasing. The dairy industry in Pakistan is confronting many challenges to adapt these food safety and quality measures. This study was purposely conducted in the south region of Punjab Province, as this region has rich population of livestock and milk production. To collect essential data, field study was carded out in selected four districts of Punjab Province. Field survey for dairy farmers and milk collection centers was performed in two phases. The analysis of primary data was carried out by calculating the Likert scale mean value, analysis of variance （one-way） and other descriptive statistics tools. The results showed that 76.4% milk producers had no awareness about Punjab food quality laws; as Likert-scale mean value was 1.93. The compliance level for the management practices such as Hazard Analysis of Critical Control Point （HCCAP）, Good Animal Practices （GAP） and Good Veterinary Practices （GVP） etc. was also very poor. Approximately, 32.57% milk collectors （very frequently） applied milk quality testing parameters whereas 50.72% milk collectors merely used sensory quality inspection methods at the time of milk purchase from dairy farmers. For a sustainable supply of good quality raw milk to the dairy industry in Pakistan, it was recommended that the departments for hygiene and food inspection should be vigilant. The prescribed food safety laws relating to milk production and marketing activities should be enforced properly to improve the situation.展开更多
The main purpose of this study was to determine the effect of a corn straw or mixed diet on milk production, milk composition and the expression of genes associated with lactation in mid-lactation Chinese Holstein cow...The main purpose of this study was to determine the effect of a corn straw or mixed diet on milk production, milk composition and the expression of genes associated with lactation in mid-lactation Chinese Holstein cows. In this study, 10 healthy Chinese Holstein cows were randomly assigned to two groups and fed with different diets respectively, corn straw （CS） or mixed forage （MF） diet. CS group was fed roughage consisting of 53.8% corn straw only and the forge to concentrate （F ： C） ratio [dry matter （DM）] was about 40： 60. MF group was fed roughage consisting of 3.7% Chinese wildrye and 23.4% alfalfa hay, the forge to concentrate （F ： C） ratio （DM） was 70： 30. All the cows were fed 8 weeks and body weight, dry matter intake, body condition score, fat, protein, lactose, milk yield, total solid and somatic cell count （SCC） were recorded. Quantitative real-time PCR （qRT-PCR） was used to analyze cow mammary gland samples representing two different diets. The results suggested that different diet types had significant effects on milk yield, lactose, milk fat, milk protein, dry matter intake and somatic cell count in dairy cows, and cows fed MF diet improved milk production and lactation performance clearly （P〈0.05）. In addition, mRNA expression of genes ACC, roTOR, STATS, CSN2, PPAR）,, FABP3 and PTEN in MF group was extremely significantly higher than that in CS group （P〈0.05）. mRNA expression ofAKT1, FAS, SCD and SREBPlc in MF group was significantly higher than that in CS group （P〈0.01）. In summary, the milk yield and composition in mixed forage group were significantly improved than those in corn straw group.展开更多
In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the...In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the high performance liquid chromatography-mass spectrometry(HPLC-MS/MS)approach.The total contents of the hydrolytic amino acids in cow colostrum,cow mature milk,human colostrum and human mature milk were 5.00,4.38,2.12 and 2.48 g·L^(-1),respectively.Among these,the contents of the hydrolytic amino acids in cow milk were higher than those in human milk,indicating a decreasing trend with the prolongation of lactation.Additionally,principal component and hierarchical cluster analyses were used to further screen the differentially expressed amino acids.These results enhanced the understanding of the hydrolytic amino acids in cow and human milk across different lactation periods,which could provide potential directions for newborn dairy powder and nutritious supplementary.展开更多
Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of ...Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of records of 2496 Chinese Holsteins first lactation cows collected from 1989 to 2000.The model included 21 herd effects,four calving season effects,nine age at first calving effects,6697 animal effects.(Co)variance components of milk yield,fat yield and age at first calving were estimated with the software package for variance component estimation(VCE) by an animal model. The heritabilities were 0.14,0.21,0.38 for milk yield,fat yield and age at first calving,respectively.The estimates of genetic correlation between milk yield and fat yield,age at first calving were 0.96,-0.29,respectively.The estimate of genetic correlation between fat yield and age at first calving was -0.28.展开更多
A total of 90 cows from two farms (farm A 30 cows, farm B 60 cows) were used to study the effect of Bospro on milk production, milk quality and subclinical mastitis incidence. The cows in the test group were supplied ...A total of 90 cows from two farms (farm A 30 cows, farm B 60 cows) were used to study the effect of Bospro on milk production, milk quality and subclinical mastitis incidence. The cows in the test group were supplied with 20 g of Bospro per head per day and meanwhile, the percentage of milk fat, protein and lactose and moisture of the milk samples were analysed. The results showed that the milk yield of both high production and mid-to-low milk producting cows increased by 3.3% to 5.3% respectively compared with their control group of cows, but there was no changes on the milk content between the treated and the control cows. The treated cows also showed an increased body weight (P>0.05) and significantly reduced incidence of mastitis, as Compared with that of the control group.The experiment dcmonstrats that Bospro can increase milk yield, but not at the expense of milk quality and body weight.展开更多
Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model an...Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.展开更多
Reversed-phase high-performance liquid chromatography （RP-HPLC） method with C4 column and C18 column for analyzing β-lactoglobulin and α-lactalbumin in bovine milk was developed and the performance and characteris...Reversed-phase high-performance liquid chromatography （RP-HPLC） method with C4 column and C18 column for analyzing β-lactoglobulin and α-lactalbumin in bovine milk was developed and the performance and characteristic of two columns were compared. Shiseido Proteonavi C4 column （250 mm×4.6 mm×5μm） and Shiseido CAPCELL PAK SG 300 C18 column （250 mm× 4.6 mm×5 μm） were used in the experiment. Phase A was composed of 0.1% （V/V） trifluoroacetic acid （TFA） in ultrapure water and Phase B （organic phase） was composed of 0.1% TFA in acetonitrile. Gradient elution was taken. Flow rate was 1 mL min-1. The detection wavelength was 215 nm. The injection volume was 20 μL and the column temperature was 30℃. The results showed that linear relationship was good and recovery of α-lactalbumin and β-lactoglobulin was 86.12%-104.38%, C18 column had stronger ability to resist acid and more stable, and the method with C4 column had excellent sensitivities and good separation.展开更多
To research the relation among the erythrocytic membrane.liquidity and the contents of MDA, the activity of SOD in serum of the milk goat with fluorosis. An animal model with fluorosis was constructed, and the fluores...To research the relation among the erythrocytic membrane.liquidity and the contents of MDA, the activity of SOD in serum of the milk goat with fluorosis. An animal model with fluorosis was constructed, and the fluorescent probe technique of DPH was used to measue the erythrocytic membrane liquidity. At the same time, the contents of MDA and the activity of SOD in serum were measured. The results showed that the erythrocytic membrane liquidity in the control group and flurosis group were 5.6742 ± 0.4417 and 3.7248 ± 0.4521 （P 〈0.01） respectively, the contents of MDA in serum were 2.0408 ± 0.198 and 4.494± 0.438 （P 〈0.01） respectively, the activities of SOD were 175.638 ± 22.201 and 113.714 ± 34.258 （P 〈0.01） respectively. The correlation analysis indicated that the relation between the activity of SOD and the liquidity of erythrocytic membrane was positive correlation （ r= 0.7321, P 〈0.05）, whereas the relation between the contents of MDA and the liquidity of erythrocytic membrane was negative correlation （r = -0.6438, P 〈0.01）. The erythrocytic membrane liquidity decreased in milk goat with fluorosis, which played a role in the occurrence and development of the fluorosis. There was correlation among the erythrocytic membrane liquidity and the contents of MDA, the activity of SOD.展开更多
OBJECTIVE To investigate whether soy milk may cause reproductive disorders and decrease testosterone.METHODS Thirty two six weeks old male rats were divided into 4 groups including control group(non treatment)and thre...OBJECTIVE To investigate whether soy milk may cause reproductive disorders and decrease testosterone.METHODS Thirty two six weeks old male rats were divided into 4 groups including control group(non treatment)and three other groups were treated with soy milk powder(7.1,14.2and 21.3g·kg-1)everyday for 90 d.Histopathological examination of testis,epididymis and seminal vesicles were done using HE staining.Blood testosterone levels were assayed by ELISA.RESULTS There were positive correlations between the doses of soy milk with spermatogenesis in the testes,prostate epithelial cell hyperplasia.There were also positively correlation between dose of soy milk with vacuoles forming on epididymal epithelial cells and apoptosis in epithelial cells of seminal vesicles.The blood testosterone levels were not significantly difference between groups.CONCLUSION Subchronically soy milk feeding in rats induce histopathology changes of reproductive organs that closely related to the process of endocrine disruptors.展开更多
An experiment was conducted to determine the concentration variation of epidermal growth factors(EGF), include insulin-like growth factor -Ⅰ(IGF-Ⅰ), transforming growth factor-beta(TGF-Ⅰ ), and basic fibroblast gr-...An experiment was conducted to determine the concentration variation of epidermal growth factors(EGF), include insulin-like growth factor -Ⅰ(IGF-Ⅰ), transforming growth factor-beta(TGF-Ⅰ ), and basic fibroblast gr-owth factor (bFGF) in colostrum and normal milk of sows within 35 days after parturition. The results showed that the concentration of EGF, IGF-Ⅰ, TGF-β, bFGF was significantly higher in colostrum than that in normal milk. The concentration of these growth factors in colostrum was significantly decreased with the stage lapse of lactation, and then they remained stable in normal milk. Parity had a slight effect on the concentration of these growth factors.展开更多
Feedstuff intake plays key role in impacting the yield and quality of milk. In this study, we discussed the contents of trace metal elements in cow milk impacted by different feedstuffs. We detected the contents of Pb...Feedstuff intake plays key role in impacting the yield and quality of milk. In this study, we discussed the contents of trace metal elements in cow milk impacted by different feedstuffs. We detected the contents of Pb, Cd, As, Cu, Mg, Ca, Fe and Zn in different feedstuffs and milk by atomic absorption spectrophotometry. The determinations of Pb, Cd and As contents were by graphite furnace A_AS and Cu, Mg, Ca, Fe and Zn was by flame atomic absorption spectrometry. The results showed that Pb, Cd, As and Cu presented in feedstuffs, but Pb, Cd and As were lowly detected in milk samples, and Cu was not detected in milk samples. The content of Mg in concentrates was lower than that in forages. However, the content of Mg in milk from concentrate feed was higher than that in forage feed. This suggested that the utilization of Mg in concentrate feed was higher than that in forage feed. The contents of Ca and Zn were opposite to Mg, and the utilization of Ca and Zn in forage feed was higher than that in concentrate feed. There was no obviously change law of Fe in different feedstuffs and milk samples. The relationship between the contents of trace metal elements in milk to feedstuffs would provide a theoretical basis for dairy farming. It would be useful for improving the milk yield and milk quality of dairy production.展开更多
With 3, 3’5, 5’-tetramethylbenzidine（TMB） as the detection substrate, a reliable and highly selective method was established and optimized for the determination of Lactoperoxidase（LP） activity in raw milk. The m...With 3, 3’5, 5’-tetramethylbenzidine（TMB） as the detection substrate, a reliable and highly selective method was established and optimized for the determination of Lactoperoxidase（LP） activity in raw milk. The method was based on the enzymatic reaction principle, where hydrogen peroxide oxidated TMB in the presence of LP. The optimized conditions of this assay system were obtained, consisting of 20 mmol · L-1 TMB solution, 0.6 mmol · L-1 hydrogen peroxide and 0.1 mol · L-1 Citric Acid（CA）/0.2 mol · L-1 disodium hydrogen phosphate（Na P） buffer（pH 4.8）. TMB detection method was applied to the analysis of LP in milk samples with a practical working concentration range from 2 to 14 mg · L-1. The intra-and inter-batch variation coefficients were all below 5%, indicating a good repeatability. Confirmation test between TMB method and 2, 2-azinobi（3-ethylbenzothiazoline-6-sulphonate） diammonium salt（ABTS） method was carried out, and the results of TMB assay were in accordance with that of ABTS method.展开更多
基金National Key Research Program of China (2006BAD04A03-02)Heilongjiang Province Office of Education Funded Major Projects (10541z003)Dr. Start-up Funds of Northeast Agricultural University
文摘A total of 12 mature healthy Holstein dairy cows of the nearly body weight （580±30） kg, milk yield （22.5±2.8） kg in the early stages of lactation were selected in this experiment. The cows were randomly divided into 2 groups, every group had 6 cows, every group had 6 repeats, and every repeat had 1 cow. Added 20 g protected methionine in earlier lactating cow food every day. The results showed that protected methionine increased milk yield by 10.83%, testing group milk yield was significantly different than that of control （P〈0.05）; protected methionine increased milk fat by 5.98%, testing group milk fat was significantly different than that of control （P〈0.05）; Milk protein increased by 2.15%, but bad insignificantly different （P〉0.05）; dry matter of milk had the tendency of decrease, but had insignificant difference （P〉0.05）.
基金Supported by High Technology Project of Ministry of Science and Technology of China(863 Project)(2013AA102504-03)Major Project of Applying Technology Research and Development of Heilongjiang Province(GA15B203)
文摘The probiotic Bacillus subtilis （B. subtilis） was widely applied in animal production as feed additive. Lysine （Lys） and methionine （Met） were the two most important limiting amino acids in livestock animal feed. Raising Lys and Met contents in B. subtilis would provide better effects for animal production and save Lys and Met supplements. We still didn＇t know whether Lys- rich and Met-rich protein genes from plants could be transfected into B. subtilis and expressed at a high level so as to improve animal production, such as milk production as an additional diet. The Lys-rich protein gene （Cflr） and Met-rich 10 ku-δ Zein were cloned from pepper anther and maize endosperm, respectively. Then they were constructed into plasmids individually and successfully cotransfected into B. subtilis. Upon IPTG induction, mRNAs and protein expressions could be observed. Lys and Met contents in the fermentation broth were raised by 65.92% and 46.39%, respectively. After feeding 200 g and 400 g· cow^-1· d^-1, transgenic B. subtilis fermentation broth, the milk yield, milk protein and milk fat contents all significantly increased. The Lys-rich protein gene （Cflr） and Met-rich 10 ku-δ Zein were successfully transfected into B. subtilis. Contents of Lys and Met in the transgenic B. subalis obviously raised and the fermentation broth of the transgenic bacteria could effectively improve milk yield and quality.
基金Supported by the National Natural Science Foundation of China(7167031183)Impact of Infant Powder Milk Safety Trust Index on Product Competitiveness-Index Measurement,Construction of Related Market Model and Market Simulation(G0300502)
文摘The present study was conducted in four districts of Punjab Province to examine the attitude of milk producers and milk collection agents toward compliance of milk quality and safety parameters. In current scenario, the attitude of consumers for safe food in accordance to quality standards is ever increasing. The dairy industry in Pakistan is confronting many challenges to adapt these food safety and quality measures. This study was purposely conducted in the south region of Punjab Province, as this region has rich population of livestock and milk production. To collect essential data, field study was carded out in selected four districts of Punjab Province. Field survey for dairy farmers and milk collection centers was performed in two phases. The analysis of primary data was carried out by calculating the Likert scale mean value, analysis of variance （one-way） and other descriptive statistics tools. The results showed that 76.4% milk producers had no awareness about Punjab food quality laws; as Likert-scale mean value was 1.93. The compliance level for the management practices such as Hazard Analysis of Critical Control Point （HCCAP）, Good Animal Practices （GAP） and Good Veterinary Practices （GVP） etc. was also very poor. Approximately, 32.57% milk collectors （very frequently） applied milk quality testing parameters whereas 50.72% milk collectors merely used sensory quality inspection methods at the time of milk purchase from dairy farmers. For a sustainable supply of good quality raw milk to the dairy industry in Pakistan, it was recommended that the departments for hygiene and food inspection should be vigilant. The prescribed food safety laws relating to milk production and marketing activities should be enforced properly to improve the situation.
基金Supported by Fund of the National Basic Research Program of China(973)(2011CB100804)
文摘The main purpose of this study was to determine the effect of a corn straw or mixed diet on milk production, milk composition and the expression of genes associated with lactation in mid-lactation Chinese Holstein cows. In this study, 10 healthy Chinese Holstein cows were randomly assigned to two groups and fed with different diets respectively, corn straw （CS） or mixed forage （MF） diet. CS group was fed roughage consisting of 53.8% corn straw only and the forge to concentrate （F ： C） ratio [dry matter （DM）] was about 40： 60. MF group was fed roughage consisting of 3.7% Chinese wildrye and 23.4% alfalfa hay, the forge to concentrate （F ： C） ratio （DM） was 70： 30. All the cows were fed 8 weeks and body weight, dry matter intake, body condition score, fat, protein, lactose, milk yield, total solid and somatic cell count （SCC） were recorded. Quantitative real-time PCR （qRT-PCR） was used to analyze cow mammary gland samples representing two different diets. The results suggested that different diet types had significant effects on milk yield, lactose, milk fat, milk protein, dry matter intake and somatic cell count in dairy cows, and cows fed MF diet improved milk production and lactation performance clearly （P〈0.05）. In addition, mRNA expression of genes ACC, roTOR, STATS, CSN2, PPAR）,, FABP3 and PTEN in MF group was extremely significantly higher than that in CS group （P〈0.05）. mRNA expression ofAKT1, FAS, SCD and SREBPlc in MF group was significantly higher than that in CS group （P〈0.01）. In summary, the milk yield and composition in mixed forage group were significantly improved than those in corn straw group.
基金Supported by the National Key R&D Program of China(2018YFC1604302)the"Twelfth-Five Year"National Science and Technology Plan Project(2013BAD18B03)+2 种基金Shenyang Technological Innovation Project(Y17-0-028)Liaoning Revitalization Talents Program(XLYC1902083)Liaoning Distinguished Professor Project。
文摘In this study,the hydrolytic amino acids of Chinese human and Holstein cow milk of different lactation periods were analyzed by the advanced isobaric tags for relative and absolute quantitation(iTRAQ)combined with the high performance liquid chromatography-mass spectrometry(HPLC-MS/MS)approach.The total contents of the hydrolytic amino acids in cow colostrum,cow mature milk,human colostrum and human mature milk were 5.00,4.38,2.12 and 2.48 g·L^(-1),respectively.Among these,the contents of the hydrolytic amino acids in cow milk were higher than those in human milk,indicating a decreasing trend with the prolongation of lactation.Additionally,principal component and hierarchical cluster analyses were used to further screen the differentially expressed amino acids.These results enhanced the understanding of the hydrolytic amino acids in cow and human milk across different lactation periods,which could provide potential directions for newborn dairy powder and nutritious supplementary.
文摘Genetic parameters for milk,fat yield and age at first calving of Chinese Holsteins in Heilongjiang were evaluated using multiple trait restricted maximum likelihood procedures with an animal model.Data consisted of records of 2496 Chinese Holsteins first lactation cows collected from 1989 to 2000.The model included 21 herd effects,four calving season effects,nine age at first calving effects,6697 animal effects.(Co)variance components of milk yield,fat yield and age at first calving were estimated with the software package for variance component estimation(VCE) by an animal model. The heritabilities were 0.14,0.21,0.38 for milk yield,fat yield and age at first calving,respectively.The estimates of genetic correlation between milk yield and fat yield,age at first calving were 0.96,-0.29,respectively.The estimate of genetic correlation between fat yield and age at first calving was -0.28.
文摘A total of 90 cows from two farms (farm A 30 cows, farm B 60 cows) were used to study the effect of Bospro on milk production, milk quality and subclinical mastitis incidence. The cows in the test group were supplied with 20 g of Bospro per head per day and meanwhile, the percentage of milk fat, protein and lactose and moisture of the milk samples were analysed. The results showed that the milk yield of both high production and mid-to-low milk producting cows increased by 3.3% to 5.3% respectively compared with their control group of cows, but there was no changes on the milk content between the treated and the control cows. The treated cows also showed an increased body weight (P>0.05) and significantly reduced incidence of mastitis, as Compared with that of the control group.The experiment dcmonstrats that Bospro can increase milk yield, but not at the expense of milk quality and body weight.
基金Supported by"Academic Backbone"Project of Northeast Agricultural University(15XG26)the National High-level Talents Special Support Program of China
文摘Predictive microbiology was utilized to model Staphylococcus aureus （S. aureus） growth and staphylococcal enterotoxin A （SEA） production in milk in this study. The modifed logistic model, modifed Gompertz model and Baranyi model were applied to model growth data of S. aureus between 15℃ and 37℃. Model comparisons indicated that Baranyi model described the growth data more accurately than two others with a mean square error of 0.0129. Growth rates generated from Baranyi model matched the observed ones with a bias factor of 0.999 and an accuracy factor of 1.01, and ft a square root model with respect to temperature; other two modifed models both overestimated the observed ones. SEA amount began to be detected when the cell number reached106.4 cfu ？ mL-1, and showed the linear correlation with time. Besides, the rate of SEA production ftted an exponential relationship as a function of temperature. Predictions based on the study could be applied to indicate possible growth of S. aureus and prevent the occurrence of staphylococcal food poisoning.
基金Supported by the Project of Science & Technology Plans in Heilongjiang Province in the 11th Five-year Period (GB07B407)
文摘Reversed-phase high-performance liquid chromatography （RP-HPLC） method with C4 column and C18 column for analyzing β-lactoglobulin and α-lactalbumin in bovine milk was developed and the performance and characteristic of two columns were compared. Shiseido Proteonavi C4 column （250 mm×4.6 mm×5μm） and Shiseido CAPCELL PAK SG 300 C18 column （250 mm× 4.6 mm×5 μm） were used in the experiment. Phase A was composed of 0.1% （V/V） trifluoroacetic acid （TFA） in ultrapure water and Phase B （organic phase） was composed of 0.1% TFA in acetonitrile. Gradient elution was taken. Flow rate was 1 mL min-1. The detection wavelength was 215 nm. The injection volume was 20 μL and the column temperature was 30℃. The results showed that linear relationship was good and recovery of α-lactalbumin and β-lactoglobulin was 86.12%-104.38%, C18 column had stronger ability to resist acid and more stable, and the method with C4 column had excellent sensitivities and good separation.
文摘To research the relation among the erythrocytic membrane.liquidity and the contents of MDA, the activity of SOD in serum of the milk goat with fluorosis. An animal model with fluorosis was constructed, and the fluorescent probe technique of DPH was used to measue the erythrocytic membrane liquidity. At the same time, the contents of MDA and the activity of SOD in serum were measured. The results showed that the erythrocytic membrane liquidity in the control group and flurosis group were 5.6742 ± 0.4417 and 3.7248 ± 0.4521 （P 〈0.01） respectively, the contents of MDA in serum were 2.0408 ± 0.198 and 4.494± 0.438 （P 〈0.01） respectively, the activities of SOD were 175.638 ± 22.201 and 113.714 ± 34.258 （P 〈0.01） respectively. The correlation analysis indicated that the relation between the activity of SOD and the liquidity of erythrocytic membrane was positive correlation （ r= 0.7321, P 〈0.05）, whereas the relation between the contents of MDA and the liquidity of erythrocytic membrane was negative correlation （r = -0.6438, P 〈0.01）. The erythrocytic membrane liquidity decreased in milk goat with fluorosis, which played a role in the occurrence and development of the fluorosis. There was correlation among the erythrocytic membrane liquidity and the contents of MDA, the activity of SOD.
文摘OBJECTIVE To investigate whether soy milk may cause reproductive disorders and decrease testosterone.METHODS Thirty two six weeks old male rats were divided into 4 groups including control group(non treatment)and three other groups were treated with soy milk powder(7.1,14.2and 21.3g·kg-1)everyday for 90 d.Histopathological examination of testis,epididymis and seminal vesicles were done using HE staining.Blood testosterone levels were assayed by ELISA.RESULTS There were positive correlations between the doses of soy milk with spermatogenesis in the testes,prostate epithelial cell hyperplasia.There were also positively correlation between dose of soy milk with vacuoles forming on epididymal epithelial cells and apoptosis in epithelial cells of seminal vesicles.The blood testosterone levels were not significantly difference between groups.CONCLUSION Subchronically soy milk feeding in rats induce histopathology changes of reproductive organs that closely related to the process of endocrine disruptors.
文摘An experiment was conducted to determine the concentration variation of epidermal growth factors(EGF), include insulin-like growth factor -Ⅰ(IGF-Ⅰ), transforming growth factor-beta(TGF-Ⅰ ), and basic fibroblast gr-owth factor (bFGF) in colostrum and normal milk of sows within 35 days after parturition. The results showed that the concentration of EGF, IGF-Ⅰ, TGF-β, bFGF was significantly higher in colostrum than that in normal milk. The concentration of these growth factors in colostrum was significantly decreased with the stage lapse of lactation, and then they remained stable in normal milk. Parity had a slight effect on the concentration of these growth factors.
文摘Feedstuff intake plays key role in impacting the yield and quality of milk. In this study, we discussed the contents of trace metal elements in cow milk impacted by different feedstuffs. We detected the contents of Pb, Cd, As, Cu, Mg, Ca, Fe and Zn in different feedstuffs and milk by atomic absorption spectrophotometry. The determinations of Pb, Cd and As contents were by graphite furnace A_AS and Cu, Mg, Ca, Fe and Zn was by flame atomic absorption spectrometry. The results showed that Pb, Cd, As and Cu presented in feedstuffs, but Pb, Cd and As were lowly detected in milk samples, and Cu was not detected in milk samples. The content of Mg in concentrates was lower than that in forages. However, the content of Mg in milk from concentrate feed was higher than that in forage feed. This suggested that the utilization of Mg in concentrate feed was higher than that in forage feed. The contents of Ca and Zn were opposite to Mg, and the utilization of Ca and Zn in forage feed was higher than that in concentrate feed. There was no obviously change law of Fe in different feedstuffs and milk samples. The relationship between the contents of trace metal elements in milk to feedstuffs would provide a theoretical basis for dairy farming. It would be useful for improving the milk yield and milk quality of dairy production.
基金Supported by Project for Research and Development of Harbin Aapplication Technology(2016RAQXJ046)the National "Twelfth Five-year" Plan for Science and Technology Support Program of China(2013BAD18B06)
文摘With 3, 3’5, 5’-tetramethylbenzidine（TMB） as the detection substrate, a reliable and highly selective method was established and optimized for the determination of Lactoperoxidase（LP） activity in raw milk. The method was based on the enzymatic reaction principle, where hydrogen peroxide oxidated TMB in the presence of LP. The optimized conditions of this assay system were obtained, consisting of 20 mmol · L-1 TMB solution, 0.6 mmol · L-1 hydrogen peroxide and 0.1 mol · L-1 Citric Acid（CA）/0.2 mol · L-1 disodium hydrogen phosphate（Na P） buffer（pH 4.8）. TMB detection method was applied to the analysis of LP in milk samples with a practical working concentration range from 2 to 14 mg · L-1. The intra-and inter-batch variation coefficients were all below 5%, indicating a good repeatability. Confirmation test between TMB method and 2, 2-azinobi（3-ethylbenzothiazoline-6-sulphonate） diammonium salt（ABTS） method was carried out, and the results of TMB assay were in accordance with that of ABTS method.
