| This study is aimed at heat tolerance and functioning mechanisms of Jersey×Holstein dairy cows for accumulating basis to breed high heat tolerance cows in China. In this paper, milk abilities was compared among Jersey×Holstein F1 and Jersey×(Jersey×Holstein) and Holstein cows, the effect of heat stress on hemorheology status and plasma inorganic ion concentrations and plasma enzyme levels in dairy cows were detected. The effects of heat stress on changes in nitric oxide synthase (NOS) activities, nitric oxide(NO) concentrations, MDA contents, T-SOD and T-AOC activities were evaluated. Changes of immunological function in different dairy populaions under different temperature condition were analysed, MTT chromatometry, ELASA, erythrocyte rosette test, western blot methods were useed to discuss the variation law of hot season affected immunological function of dairy cows. At the same time, the expressions of HSP70 in blood lymphocytes were studied. The polymorphisms of HSP gene and their correlation to biochemical indexes in serum of Holstein and Jersey×Holstein F1 dairy cows were investigated. The single-strand conformation polymorphism (PCR-SSCP) method was used to analyze for SNPs of the HSP gene. Expression profiles of HSP70 and cell apoptosis in liver and spleen of heat stress cows were analysed. The results indicated that Jersey xHolstein cows had higher heat tolerance than Holstein cows.1 Analysis on milk performance of Jersey×Holstein and Holstein dairy cows30 Jersey×Holstein F1 and Jerseyx(JerseyxHolstein) and Holstein cows in first parturition and same lactation stage were selected into 3 groups.The milk performance of first lactation and rectal temperature, skin temperature and breath rate of dairy cows were recorded. The results were shown as follows:In heat stress period, the average temperature was 31.10℃, the average THI was 81.75, rectal temperature, skin temperature and breath rate of Jersey×Holstein F1 and Jerseyx(Jersey×Holstein) in hot season had significantly differences (P<0.05) than Holstein cows, but there were no significantly differences (P >0.05) between Jersey×Holstein F1 and Jersey×(Jersey×Holstein). At the same nutritional level, milk fat percentage and milk protein percentage of Jerseyx(JerseyxHolstein) and JerseyxHolstein F1 had significantly differences (P<0.01)than Holstein cows.305 d milk yield and 4% standard milk yield of Holstein cows higher than those of Jersey×(JerseyxHolstein) and JerseyxHolstein F1, but there were no significant difference(P>0.05). Milk yield/kg body weight and feed efficiency of Jerseyx(JerseyxHolstein) had significantly differences(P<0.05)among JerseyxHolstein Fi and Holstein cows, but there were no significant difference(P> 0.05) between JerseyxHolstein F1 and Holstein cows. The milk decline rate per month from July to August of Holstein cows, JerseyxHolstein F1 and Jersey×(Jersey×Holstein) were 14.50%, 2.31%; 13.89%,3.19%; 13.38%,11.08%, respectively, there were significantly differences (P<0.05) among JerseyxHolstein F1, Jersey×(JerseyxHolstein) and Holstein cows. The results indicated that Jersey×Holstein had higher heat tolerance and better milk performance.2 Effect of heat stress on hemorheology status and biochemistry parameters in dairy cowsThe effects of heat stress on changes in hemorheology and plasma inorganic ion concentration and plasma enzyme levels were evaluated in two groups of 60 healthy Holstein and Jersey×Holstein F1 and Jersey×(Jersey×Holstein) dairy cows. These animals were subjected to a cool environment when the mean temperature-humidity index (THI) was 47.24 and temperature was 10.35℃during the month of December. This experiment was repeated during the hotter month of July of the following year, when the mean THI was 82.61 and temperature was 31.07℃. The results were showed as follows:Heat stress had no effect on ESR in Holstein and Jersey×Holstein cows but whole blood and plasma viscosity and PCV were elevated in hot season and had significantly differences compared with those in cold season (P<0.01), while there were no significantly differences between Holstein and Jersey×Holstein cows in hot or cold season. In addition, the content of plasma potassium of Jersey×Holstein cows was significantly different between hot and cold season (P<0.05), while there were no significantly differences between Holstein and Jersey×Holstein cows in hot or cold season. Heat stress decreased plasma natrium and calcium content (P<0.01), while there were no significantly differences between Holstein and Jersey×Holstein cows in hot or cold season. The content of plasma chloride was not significantly different between two breeds and two season. The content of ALT and ALP were elevated (P<0.05) with heat stress in Holstein and Jersey cows. The AST content was significantly different between Holstein and Jersey×Holstein cows in cold season (P< 0.05). These results indicated that whole blood and plasma viscosity and PCV, plasma natrium, calcium, and ALT and ALP had close relation with heat-stress, those indexes were independent of dairy breed.3 Effect of heat stress on anti-oxidative capability in Holstein and Jersey dairy cowsThe effects of heat stress on changes in the nitric oxide synthase (NOS), nitric oxide(NO), MDA contents, T-SOD and T-AOC activities were evaluated in three groups of 60 healthy Holstein and Jersey X Holstein dairy cows. These animals were subjected to a cool environment during the month of December and hotter month of July of the following year. The results were showed as follows:the levels of nitric oxide synthase (NOS) in blood serum in summer were significantly lower than those in winter both in Holstein and Jersey×Holstein cows (P<0.01). In summer, levels of nitric oxide synthase (NOS) of Jersey cow were significantly lower than those of Holstein (P<0.01). But in winter, the levels of nitric oxide synthase (NOS) in blood serum were no significant difference between Holstein and Jersey×Holstein cow (P>0.05). The levels of nitric oxide(NO) in blood serum in summer were significantly lower than those in winter in Holstein cow(P<0.05). But in Jersey×Holstein cow, the levels of nitric oxide (NO) in blood serum were no significant difference between summer and winter(P>0.05). In winter, the levels of nitric oxide (NO) in blood serum were significant difference between Holstein and Jersey×Holstein cow (P<0.05),but in summer there is no significant difference. In summer, compared with Holstein, the MDA contents of Jersey×Holstein evidently decreased (P< 0.05) and T-SOD activities of Jersey significantly increased (P<0.05), the T-AOC of Jersey×Holstein no significantly increased. however, in winter, there were no significant differences on the MDA contents and the T-SOD,T-AOC activities between Jersey×Holstein and Holstein cow. the MDA contents decreased (P<0.01) and the T-SOD activities increased (P<0.01) of both Jersey×Holstein and Holstein cow; the T-AOC activities of Holstein serum increased evidently (P<0.05) between hot and cold season. The experiment results indicated that heat stress would do harm to dairy cattle significantly; during heat stress the anti-oxidation capability of Jersey×Holstein was higher than Holstein, Jersey×Holstein was more suitable to live in the tropic and semi-tropica area than Holstein. It provided a scientific theory for the diagnosis of heat stress and selecting heat-resistant dairy cattle.4 Effect of heat stress on immunological function in dairy cowsChanges of immunological function under different temperature condition with MTT chromatometry, ELASA, erythrocyte rosette test were tested to discuss the variation law of hot season affected immunological function of dairy cows. The results indicated that:(1) the concentrations of immunoglobulin (IgG, IgA and IgM) in the serum of Jersey×Holstein cows were higher than Holstein cows, but there were not significantly different (P>0.05) in different months. In summer, the concentrations of IgM in the serum of Jersey×Holstein cows were significantly higher than Holstein cows (P<0.05). (2) In July, the somatic cell count (SCC) of different dairy cows were significant differences (P<0.05) than that of in March and November, but there were not significantly different (P>0.05) between Holstein and Jersey×Holstein cows in whole year. (3) In November, stimulated index of lymphocyts higher than that of in March and July (P<0.05), but there were not significantly different (P>0.05) between Holstein and Jersey×Holstein cows in different periods. In July, the erythrocyte rosette rate of different dairy cows were significant differences (P <0.05) than that of in March and November, the erythrocyte rosette rate of Jersey×Holstein cows were higher than that of Holstein cows. The results indicated that Jersey×Holstein had higher immunological function and could resist the harmfulness of heat stress.5 Studies on the relation between Polymorphism of HSP Gene and expression of heat stress protein 70 and heat tolerance in Dairy CowThe polymorphisms of HSP gene and their correlation to biochemical index in serum of Holstein and Jersey×Holstein F1 dairy cattle were investigated for the purpose of providing molecular maker information to facilitate the breeding efficiency. The heat tolerant traits were studied in Holstein and Jersey×Holstein F1 dairy cows. SNPs of HSP gene were analyzed by PCR-SSCP. And gene and genotype frequencies were calculated for the polymorphic loci in HSP gene. At the same time, the expression of HSP70 in blood lymphocytes were studied. Effects of genotypes in different locus on heat tolerant traits were estimated.The results indicated that T deletion mutations (C→G,T→C) in HSPA8 and (C→A) in HSPA3-exonl were detected. Results showed that the PCR products demonstrated polymorphisms, and showed three kinds of genotype AA/AB/BB in two populations, genotype BB only exist in Jersey×Holstein F1 population at locus HSPA8, however there were three kinds of genotypes AA/AB/BB and mainly was genotype BB in two populations at locus HSPA3. This polymorphic locus of HSP gene was at Hardy—Weinberg equilibrium (P>0.05). Correlation analysis showed that there was no relationship between the polymorphisms of HSPA3 and HSPA8 and T-AOC; However there were positive relationships between polymorphisms of HSPA3 and HSPA8 and MDA content and T-SOD activity.The single-strand conformation polymorphism (PCR-SSCP) method was used to analyze for polymorphism at the 5'-flanking region of the HSPA1A gene. The PCR-SSCP products of primer showed polymorphisms and could be divided into four genotypes:AA, AB, AC, CC among 80 Jersey×Holstein F1 and Holstein cows. The AC genotypic cows showed higher heat tolerance level than those of AA, AB, and BB genotype. These mutation sites can be used as molecular genetic markers to assist selection for anti-heat stress cows.In July, the expression of HSP70 in Holstein dairy cows were the highest, the next was in November, the expression of HSP70 in Holstein dairy cows in March were the lowest. the expression of HSP70 in Holstein dairy cows were significantly different (P<0.05) between March and November, there were significantly different (P<0.01) among July, November and March, the expression of HSP70 in Jersey×Holstein F1 was 2.1 times higher than that of Holstein dairy cows, it was significantly different (P<0.05) between two populations.6 Expression Profiles of HSP70 and cell apoptosis in liver and spleen of heat stress cowsTo investigate the effects of heat stress on histomorphology and function of cows, the histology of liver and spleen of initial stage of weaning calf in experimental heat stress were observed and the expression profiles of HSP70 in liver and spleen were analysed, the apoptotic cells were assayed. The result showed that the construction of liver and spleen in every group revealed no difference at normal temperature condition. Compared with Holstein cows, Jersey×Holstein cows had the larger bounds of microfold, the better structural and functional of red-eared slide and white-eared slide, the more compact lymphocyte arrangement of microfold in spleen, which reflected the difference in tissue construction and caused the difference in heat resistance. The different heat stress could damage liver and spleen at different degrees in all the groups, and the ultrastructure changed with the heat stress times going. The contents of HSP70 showed a curve change with the heat stress times prolonging, and had a certainty relation with histiocyte damages, which inferred that the contents of HSP70 could be as one of indicator to determinate histiocyte damages. The damages degree of organs and tissues in heat stress cows were gradually aggravated, part of lymphocyte were showed from apoptosis to putrescence as the hyperthermia stress increase, the damages of structures and cells in liver and spleen aggravated.Conclusion:In heat stress period, rectal temperature of Jersey×Holstein cows lower than that of Holstein cows, milk yield/kg body weight of JerseyxHolstein cow higher than that of Holstein cows. The milk decline rate per month of JerseyxHolstein cows significantly lower than that of Holstein cows. During heat stress the anti-oxidation capability of Jersey×Holstein was higher than Holstein, the erythrocyte rosette rate and the content of IgM of Jersey×Holstein cows were higher than that of Holstein cows. Correlation analysis showed that there were positive relationships between polymorphisms of HSPA3 and HSPA8 and MDA content and T-SOD activity. There were positive relationships between polymorphisms of HSPA1A and heat tolerance level, the AC genotypic cows showed higher heat tolerance level than those of AA, AB, and BB genotype. The expression of HSP70 in Jersey X Holstein cows was significantly higher than that of Holstein dairy cows.The results indicated that JerseyxHolstein had higher heat tolerance than Holstein cows, reflected in the differences in blood biochemical parameters, anti-oxidative capability and immunological function.The analysis of SNPs indicated that molecular marker for selection of anti-stress dairy cows. The damages degree of organs and tissues in heat stress cows were gradually aggravated, part of lymphocyte were showed from apoptosis to putrescence as the hyperthermia stress increase, the damages of structures and cells in liver and spleen aggravated. Jersey×Holstein was more suitable to live in the tropic and semi-tropica area than Holstein.
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