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Abstract [Objectives] In this study， routine blood indexes of Guike pig were detected to clarify quantity variation and morphology distribution of different functional cells （red blood cells， white blood cells and platelets）， thus providing reference data for immunological evaluation and disease resistance research of Guike pig. [Methods] Blood samples were collected from forty-four 49-day-old healthy Guike pigs （22 males and 22 females） once a week for seven consecutive weeks to detect routine blood indexes， and the results were compared with routine blood indexes of Landrace pig and Enshi black pig. [Results] Among red blood cell indexes of Guike pig at different day ages， red blood cell count （RBC） and hemoglobin count （HGB） both reached the lowest levels （6.85×1012/L and 97.1 g/L） at 70 days of age， which were significantly lower than the corresponding indexes at 49， 56， 63， 84 and 91 days of age （P<0.05， similarly hereinafter）； mean corpuscular hemoglobin （MCH） and mean corpuscular hemoglobin concentration （MCHC） demonstrated basically the same variation pattern， which both reached the lowest levels （15.11 pg and 275.70 g/L） at 70 days of age and reached the highest levels （16.40 pg and 314.30 g/L） at 91 days of age； hematocrit （HCT）， mean corpuscular volume （MCV） and red blood cell distribution width （RDW） exhibited relatively stable changes with no significant differences among different day ages （P>0.05， similarly hereinafter）. Among white blood cell indexes of Guike pig at different day ages， white blood cell count （WBC） reached the lowest level （13.71×109/L） at 63 days of age and reached the highest level （17.52×109/L） at 84 days of age， with significant differences； neutrophil count （NEUT） reached the lowest level （3.61×109/L） at 70 days of age， which was significantly lower than that at 49， 56 and 77 days of age； lymphocyte count （LYMPH） exhibited relatively stable changes and was not significantly affected by the increase in day age. Among platelet indexes of Guike pig at different day ages， platelet count （PLT）， thrombocytocrit （PCT） and platelet volume distribution width （PDW） exhibited relatively stable changes among different day ages， which were not significantly affected by the increase in day age. Compared to 35-day-old Landrace pig and 5-month-old Enshi black pig， most routine blood indexes of Guike pig were similar to or ranged between those of Landrace pig and Enshi black pig except HCT， mean platelet volume （MPV）， PCT and PDW. [Conclusions] Guike pig has a certain uniqueness in routine blood indexes， which has developed a stable immune system at 49-91 days of age.
Key words Guike pig； Landrace pig； Enshi black pig； Routine blood indexes； Detection and analysis
Routine blood indexes are the basic indexes of immunological assays. Studies have shown that immune indexes can be used as indirect indicators for disease-resistance breeding because immune function is easy to measure. Therefore， immune index screening is a practical and feasible effective way to improve disease resistance of animals[1-2]. Blood plays an important role in ensuring body metabolism， physiological function regulation， and internal and external environmental balance. Once a problem arises in body function， it can be reflected by blood indexes. Conversely， the influence of any pathological changes in components or indicators of the blood will be reflected in tissues and organs[3-4]. Therefore， the detection of routine blood indexes has been regarded as an indispensable aid for disease diagnosis in clinical practice.
Cheng et al.[5] detected eight blood indexes of domestic swine and two crossed wild boar. The results indicated that higher consanguinity of wild boar could lead to stronger ability of red blood cells to transport O2 and CO2 in the blood and stronger motor function， which was conducive to improving meat quality； higher white blood cell count and hemoglobin content suggested stronger immune system and stronger resistance to diseases. Liu et al.[6] investigated the normal values of routine blood indexes and biochemical indicators of Landrace piglets and found that there were no differences in routine blood indexes and biochemical indicators between male and female Landrace piglets， but they exhibited significant differences compared with the reference values of Bama suckling pig， indicating that Landrace piglets had unique physiological and biochemical characteristics. Li et al.[7] studied the effect of Chinese traditional medicine additives on routine blood indexes of pigs and found that adding different proportions of Chinese medicine additives in the basal diet could significantly improve the content of macrolymphocytes， plasma cells and monocytes and the level of IgG and IgM， suggesting that Chinese medicine additives could promote weight gain and enhance immunity of pigs. Wang et al.[8] detected routine blood traits and T-lymphocyte subpopulation traits of Dapulian and Landrace piglets using automatic blood cell analyzer and flow cytometry， and analyzed the effect of breeds on these traits. The results showed that there were significant or extremely significant differences in most routine blood indexes and T-lymphocyte subpopulation traits between Dapulian and Landrace piglets. Chen et al.[4] reported that there were significant differences in mean corpuscular volume （MCV）， platelet count （PLT） and percentage of neutrophilic granulocytes （GRN） and extremely significant differences in mean corpuscular hemoglobin concentration （MCHC）， red blood cell distribution width （RDW）， mean platelet volume （MPV）， white blood cell count （WBC）， lymphocyte count （LYMPH）， median cell count （MID） and neutrophil count （NEUT） between diseased pigs and Landrace pigs， whereas no significant differences were found in other indexes. Specifically， changes in leukocyte indexes reflect the health status of pigs to a certain extent and can be used as an aid to evaluate the health status of the herds. Xiang et al.[9] compared and analyzed blood indexes of Enshi black pig and other pig breeds， and genotyped SNP loci in CXCR4 gene of Enshi black pig. The results confirmed that SNP loci in CXCR4 gene could be used to investigate changes in blood indexes. Guo et al.[10] analyzed the effect of different immune processes against classical swine fever （CSF） and porcine reproductive and respiratory syndrome （PRRS） on blood indexes to identify the optimal immune process based on blood indexes. Ultimately， the optimal immune process for attenuated vaccines against CSF and PRRS was as follows： pigs were vaccinated with the attenuated vaccine against CSF and then vaccinated with the attenuated vaccine against PRRS after seven days， which led to the best immunity and the best growth performance. Guike pig is a new breed obtained by hybridization between Luchuan pig and introduced breeds by Guangxi Veterinary Research Institute. So far， Guike pig is well received by farmers due to good pork quality and rapid growth[11-13]. However， there have been no reports on the determination of routine blood indexes of Guike pig.
In this study， quantity variation and morphology distribution of different functional cells （red blood cells， white blood cells and platelets） in Guike pig were clarified by detecting routine blood indexes， aiming at providing reference data for immunological evaluation and disease resistance breeding of Guike pig.
Materials and Methods
Materials
Forty-four 7-week-old （49 days old） healthy Guike pigs （22 males and 22 females）， weighing 35-60 kg， were provided by the Guike Pig Breeding Farm of Guangxi Veterinary Research Institute.
Methods
Collection of blood samples
Before blood collection， pigs were fasted for 12 h. The gender and number of each pig were recorded. Subsequently， 3.0 ml of blood sample was collected from the anterior venous sinus， placed in a centrifuge tube containing EDTA anticoagulant， mixed evenly， labeled， stored at 4-8 ℃ and sent to the animal hospital of Guangxi University for routine blood analysis. Blood samples were collected once a week for seven consecutive weeks.
Detection of routine blood indexes
Routine blood indexes were detected by using HS Compact digital automatic blood analyzer （Yoder， France）. A total of 18 blood indexes were obtained， including red blood cell count （RBC， ×1012/L）， hemoglobin count （HGB， g/L）， hematocrit （HCT， %）， mean corpuscular volume （MCV， fL）， mean corpuscular hemoglobin （MCH， pg）， mean corpuscular hemoglobin concentration （MCHC， g/L）， red blood cell distribution width （RDW， %）， white blood cell count （WBC， ×109/L）， neutrophil count （NEUT， ×109/L）， neutrophil percentage （NEUT， %）， lymphocyte count （LYMPH， ×109/L）， lymphocyte percentage （LYMPH， %）， median cell count （MID， ×109/L）， median cell percentage （MID， %）， platelet count （PLT， ×109/L）， thrombocytocrit （PCT， ml/L）， mean platelet volume （MPV， fL） and platelet volume distribution width （PDW， %）. The corresponding test reports were printed and numbered.
Statistical analysis
Experimental data were processed by using Excel 2010. One-way ANOVA and multiple comparisons （LSD） were performed with SPSS 17.0.
Results and Analysis
Analysis of routine blood indexes of Guike pig at different day ages Analysis of red blood cell indexes
As could be seen in Table 1， among red blood cell indexes of Guike pig at different day ages， RBC decreased first and then increased， which reached the lowest level （6.85×1012/L） at 70 days of age and was significantly lower than that at 49， 56， 63， 84 and 91 days of age （P<0.05， similarly hereinafter）； HGB also reached the lowest level （97.1 g/L） at 70 days of age， which was significantly lower than that at 49， 56， 63， 84 and 91 days of age； MCH and MCHC demonstrated basically the same variation pattern， which both reached the lowest levels （15.11 pg and 275.70 g/L） at 70 days of age and reached the highest levels （16.40 pg and 314.30 g/L） at 91 days of age， with significant differences； HCT， MCV and RDW exhibited relatively stable changes with no significant differences among different day ages （P>0.05， similarly hereinafter）.
Analysis of white blood cell indexes
As could be seen in Table 2， among white blood cell indexes of Guike pig at different day ages， WBC reached the lowest level （13.71×109/L） at 63 days of age and reached the highest level （17.52×109/L） at 84 days of age， with significant differences； NEUT reached the lowest level （3.61×109/L） at 70 days of age， which was significantly lower than that at 49， 56 and 77 days of age； LYMPH exhibited relatively stable changes and was not significantly affected by the increase in day age； median cell count reached the lowest level （3.05×109/L） at 63 days of age and reached the highest level （6.48×109/L） at 49 days of age， with significant differences； median cell percentage reached the lowest level （19.98%） at 77 days of age and reached the highest level （40.54%） at 56 days of age.
Analysis of platelet indexes
As could be seen in Table 3， PLT， PCT and PDW of Guike pig exhibited relatively stable changes among different day ages and were not significantly affected by the increase in day age； MPV reached the highest level （17.39 fL） at 91 days of age， which was significantly higher than that at 70 and 77 days of age （15.77 and 15.84 fL， respectively）.
Routine blood indexes of Guike pig， 35-day-old Landrace pig[6] and 5-month-old Enshi black pig[9] were compared and analyzed. The results indicated that HCT and PDW of Guike pig were significantly lower compared with Landrace pig and Enshi black pig； MPV and PCT of Guike pig were remarkably higher than those of Landrace pig and Enshi black pig； other routine blood indexes of Guike pig were similar to or ranged between those of Landrace pig and Enshi black pig （Table 4）. Discussion
Routine blood indexes can not only reflect the immune status and health status of pigs， but also serve as an important reference for breeding management， classification and selection[8]. In this study， blood samples were collected from 49-day-old Guike pig once a week for seven consecutive weeks to detect routine blood indexes. The results showed that routine blood indexes varied among different individuals and different day ages， but most indexes fluctuated within a relatively stable range. RBC and HGB of Guike pig both reached the lowest levels （6.85×1012/L and 97.1 g/L） at 70 days of age， which were significantly lower than the corresponding indexes at 49， 56， 63， 84 and 91 days of age； WBC reached the lowest level （13.71×109/L） at 63 days of age， which was significantly lower than that at 49 and 84 days of age； MPV reached the highest level （17.39 fL） at 91 days of age， which was significantly higher than that at 70 and 77 days of age. This may be related to boost immunization against swine fever at 70-77 days of age， but the specific reasons remain to be investigated.
HCT refers to the volumetric ratio of erythrocytes to whole blood after centrifugation of a certain amount of anticoagulated whole blood， which is a simple method that indirectly reflects the number and volume of red blood cells[14]. Reasonable HCT can improve gas exchange inside and outside the body and enhance metabolism. Most diseases will consume red blood cells and result in HCT reduction. In this study， routine blood indexes of Guike pig， Landrace pig and Enshi black pig were compared and analyzed. The results indicated that HCT of Guike pig was significantly lower than that of Landrace pig and Enshi black pig； MCV of Guike pig was lower than that of Landrace pig and Enshi black pig； MCHC of Guike pig was higher than that of Landrace pig but lower than that of Enshi black pig； RDW of Guike pig was lower than that of Landrace pig but higher than that of Enshi black pig； RBC and PLT of Guike pig were higher compared to Landrace pig and Enshi black pig， suggesting that Guike pig had mild iron deficiency symptoms. In addition， although MID of Guike pig was slightly higher compared to Landrace pig， there was no apparent increase in WBC. Therefore， it could not be determined whether there was a viral or bacterial infection.
In the present study， routine blood indexes of Guike pig were detected and the results could provide reference data for immunological evaluation and disease resistance breeding of Guike pig. Moreover， it is necessary to detect cytokines IFN-γ， IL-2， IL-4 and IL-10 of Guike pig， analyze the polymorphisms of exon 14 and intron 8 of MX1 gene， and utilize immune indicators， antibody titers and molecular genetic markers， thus providing scientific basis for commercial production and disease prevention and control of Gryllidae pig. Conclusion
Guike pig has a certain uniqueness in routine blood indexes， which has developed a stable immune system at 49-91 days of age.
References
[1] Arosa FA， Pereira CF， Fonseca AM. Red blood cells as modulators of T cell growth and survival[J]. Current Pharmaceutical Design， 2004， 10（2）：191-201.
[2] van de VE， van DJT， Ottenhoff TH. Genetic deficiencies of innate immune signaling in human infectious disease[J]. The Lancet. Infectious Diseases， 2009， 9（11）：688-698.
[3] Beutler B. Innate immunity： An overview[J]. Molecular Immunology， 2004， 40（12）：845-859.
[4] Chen SK， Wang XF， Li S， et al. Evaluation on healthy pigs assisted by blood routine indexes[J]. Jilin Animal Husbandry and Veterinary Medicine， 2015， （3）：20-22.（in Chinese）
[5] Cheng ZX， Ni X， Han YY， et al. Comparison of eight blood indexes among domestic swine and two crossed wild boar[J]. Hubei Agricultural Sciences， 2007， 46（3）：419-421.（in Chinese）
[6] Liu JW， Zhang YJ， Li ZX， et al. Investigation on the normal values of blood routine and serum biochemistry in Changbai piglet[J]. Chinese Journal of Comparative Medicine， 2007， 17（7）：393-394.（in Chinese）
[7] Li CY， Gan ZL， Tang DY， et al. Effects of Chinese herbal feed additives on weight gain， routine blood indexes and the level immunoglobulin in swine[J]. Progress in Veterinary Medicine， 2012， 33（10）：53-56.（in Chinese）
[8] Wang HZ， Lin S， Wang YP， et al. Analyses of breeds and little effect on routine blood traits and T-lymphocyte subpopulation traits in piglets[J]. Acta Veterinaria et Zootechnica Sinica， 2014， 45（11）：1760-1766.（in Chinese）
[9] Xiang Y， Li ZM， Li JP， et al. Enshi black pig blood index measurement analysis and analysis of the correlation and CXCR4 gene polymorphism[J]. Swine Industry Science， 2015， 32（7）：130-132.（in Chinese）
[10] Guo SQ， Shen GS， Dong Y， et al. Effect of different immune process of CSF and PRRS on blood index and ratio of feed to gain in pig[J]. Feed Industry， 2016， 37（5）：39-41.（in Chinese）
[11] Pan TB， Zhang JF， Xiao ZZ， et al. Effects of different energies and proteins on growth performance and blood biochemical indexes Guike maternal line pigs[J]. Heilongjiang Animal Science and Veterinary Medicine， 2010， （19）：71-72.（in Chinese）
[12] Xie BK， Huang GY， Nong SQ， et al. Guike I synthetic line pig production performance measurement[C]. Changchun： Proceedings of the Third Meeting of Fifth Session of Pig Branch of China Association of Animal and Veterinary Medicine·Development Forum on Swine Industry Science and Technology Innovation： 2012， 166-167.（in Chinese）
[13] Luo XQ， Yang C， Huang LX， et al. Analysis of fattening， slaughter performance and meat quality traits in Guike pig[J]. Journal of Southern Agriculture， 2015， 46（1）：133-137.（in Chinese）
[14] Tian PP， Zhu LS， Ma Q， et al. The relationship of HCT between age and ESR[J]. International Journal of Laboratory Medicine， 2017， 38（2）：209-210.（in Chinese）
Routine blood indexes are the basic indexes of immunological assays. Studies have shown that immune indexes can be used as indirect indicators for disease-resistance breeding because immune function is easy to measure. Therefore， immune index screening is a practical and feasible effective way to improve disease resistance of animals[1-2]. Blood plays an important role in ensuring body metabolism， physiological function regulation， and internal and external environmental balance. Once a problem arises in body function， it can be reflected by blood indexes. Conversely， the influence of any pathological changes in components or indicators of the blood will be reflected in tissues and organs[3-4]. Therefore， the detection of routine blood indexes has been regarded as an indispensable aid for disease diagnosis in clinical practice.
Cheng et al.[5] detected eight blood indexes of domestic swine and two crossed wild boar. The results indicated that higher consanguinity of wild boar could lead to stronger ability of red blood cells to transport O2 and CO2 in the blood and stronger motor function， which was conducive to improving meat quality； higher white blood cell count and hemoglobin content suggested stronger immune system and stronger resistance to diseases. Liu et al.[6] investigated the normal values of routine blood indexes and biochemical indicators of Landrace piglets and found that there were no differences in routine blood indexes and biochemical indicators between male and female Landrace piglets， but they exhibited significant differences compared with the reference values of Bama suckling pig， indicating that Landrace piglets had unique physiological and biochemical characteristics. Li et al.[7] studied the effect of Chinese traditional medicine additives on routine blood indexes of pigs and found that adding different proportions of Chinese medicine additives in the basal diet could significantly improve the content of macrolymphocytes， plasma cells and monocytes and the level of IgG and IgM， suggesting that Chinese medicine additives could promote weight gain and enhance immunity of pigs. Wang et al.[8] detected routine blood traits and T-lymphocyte subpopulation traits of Dapulian and Landrace piglets using automatic blood cell analyzer and flow cytometry， and analyzed the effect of breeds on these traits. The results showed that there were significant or extremely significant differences in most routine blood indexes and T-lymphocyte subpopulation traits between Dapulian and Landrace piglets. Chen et al.[4] reported that there were significant differences in mean corpuscular volume （MCV）， platelet count （PLT） and percentage of neutrophilic granulocytes （GRN） and extremely significant differences in mean corpuscular hemoglobin concentration （MCHC）， red blood cell distribution width （RDW）， mean platelet volume （MPV）， white blood cell count （WBC）， lymphocyte count （LYMPH）， median cell count （MID） and neutrophil count （NEUT） between diseased pigs and Landrace pigs， whereas no significant differences were found in other indexes. Specifically， changes in leukocyte indexes reflect the health status of pigs to a certain extent and can be used as an aid to evaluate the health status of the herds. Xiang et al.[9] compared and analyzed blood indexes of Enshi black pig and other pig breeds， and genotyped SNP loci in CXCR4 gene of Enshi black pig. The results confirmed that SNP loci in CXCR4 gene could be used to investigate changes in blood indexes. Guo et al.[10] analyzed the effect of different immune processes against classical swine fever （CSF） and porcine reproductive and respiratory syndrome （PRRS） on blood indexes to identify the optimal immune process based on blood indexes. Ultimately， the optimal immune process for attenuated vaccines against CSF and PRRS was as follows： pigs were vaccinated with the attenuated vaccine against CSF and then vaccinated with the attenuated vaccine against PRRS after seven days， which led to the best immunity and the best growth performance. Guike pig is a new breed obtained by hybridization between Luchuan pig and introduced breeds by Guangxi Veterinary Research Institute. So far， Guike pig is well received by farmers due to good pork quality and rapid growth[11-13]. However， there have been no reports on the determination of routine blood indexes of Guike pig.
In this study， quantity variation and morphology distribution of different functional cells （red blood cells， white blood cells and platelets） in Guike pig were clarified by detecting routine blood indexes， aiming at providing reference data for immunological evaluation and disease resistance breeding of Guike pig.
Materials and Methods
Materials
Forty-four 7-week-old （49 days old） healthy Guike pigs （22 males and 22 females）， weighing 35-60 kg， were provided by the Guike Pig Breeding Farm of Guangxi Veterinary Research Institute.
Methods
Collection of blood samples
Before blood collection， pigs were fasted for 12 h. The gender and number of each pig were recorded. Subsequently， 3.0 ml of blood sample was collected from the anterior venous sinus， placed in a centrifuge tube containing EDTA anticoagulant， mixed evenly， labeled， stored at 4-8 ℃ and sent to the animal hospital of Guangxi University for routine blood analysis. Blood samples were collected once a week for seven consecutive weeks.
Detection of routine blood indexes
Routine blood indexes were detected by using HS Compact digital automatic blood analyzer （Yoder， France）. A total of 18 blood indexes were obtained， including red blood cell count （RBC， ×1012/L）， hemoglobin count （HGB， g/L）， hematocrit （HCT， %）， mean corpuscular volume （MCV， fL）， mean corpuscular hemoglobin （MCH， pg）， mean corpuscular hemoglobin concentration （MCHC， g/L）， red blood cell distribution width （RDW， %）， white blood cell count （WBC， ×109/L）， neutrophil count （NEUT， ×109/L）， neutrophil percentage （NEUT， %）， lymphocyte count （LYMPH， ×109/L）， lymphocyte percentage （LYMPH， %）， median cell count （MID， ×109/L）， median cell percentage （MID， %）， platelet count （PLT， ×109/L）， thrombocytocrit （PCT， ml/L）， mean platelet volume （MPV， fL） and platelet volume distribution width （PDW， %）. The corresponding test reports were printed and numbered.
Statistical analysis
Experimental data were processed by using Excel 2010. One-way ANOVA and multiple comparisons （LSD） were performed with SPSS 17.0.
Results and Analysis
Analysis of routine blood indexes of Guike pig at different day ages Analysis of red blood cell indexes
As could be seen in Table 1， among red blood cell indexes of Guike pig at different day ages， RBC decreased first and then increased， which reached the lowest level （6.85×1012/L） at 70 days of age and was significantly lower than that at 49， 56， 63， 84 and 91 days of age （P<0.05， similarly hereinafter）； HGB also reached the lowest level （97.1 g/L） at 70 days of age， which was significantly lower than that at 49， 56， 63， 84 and 91 days of age； MCH and MCHC demonstrated basically the same variation pattern， which both reached the lowest levels （15.11 pg and 275.70 g/L） at 70 days of age and reached the highest levels （16.40 pg and 314.30 g/L） at 91 days of age， with significant differences； HCT， MCV and RDW exhibited relatively stable changes with no significant differences among different day ages （P>0.05， similarly hereinafter）.
Analysis of white blood cell indexes
As could be seen in Table 2， among white blood cell indexes of Guike pig at different day ages， WBC reached the lowest level （13.71×109/L） at 63 days of age and reached the highest level （17.52×109/L） at 84 days of age， with significant differences； NEUT reached the lowest level （3.61×109/L） at 70 days of age， which was significantly lower than that at 49， 56 and 77 days of age； LYMPH exhibited relatively stable changes and was not significantly affected by the increase in day age； median cell count reached the lowest level （3.05×109/L） at 63 days of age and reached the highest level （6.48×109/L） at 49 days of age， with significant differences； median cell percentage reached the lowest level （19.98%） at 77 days of age and reached the highest level （40.54%） at 56 days of age.
Analysis of platelet indexes
As could be seen in Table 3， PLT， PCT and PDW of Guike pig exhibited relatively stable changes among different day ages and were not significantly affected by the increase in day age； MPV reached the highest level （17.39 fL） at 91 days of age， which was significantly higher than that at 70 and 77 days of age （15.77 and 15.84 fL， respectively）.
Routine blood indexes of Guike pig， 35-day-old Landrace pig[6] and 5-month-old Enshi black pig[9] were compared and analyzed. The results indicated that HCT and PDW of Guike pig were significantly lower compared with Landrace pig and Enshi black pig； MPV and PCT of Guike pig were remarkably higher than those of Landrace pig and Enshi black pig； other routine blood indexes of Guike pig were similar to or ranged between those of Landrace pig and Enshi black pig （Table 4）. Discussion
Routine blood indexes can not only reflect the immune status and health status of pigs， but also serve as an important reference for breeding management， classification and selection[8]. In this study， blood samples were collected from 49-day-old Guike pig once a week for seven consecutive weeks to detect routine blood indexes. The results showed that routine blood indexes varied among different individuals and different day ages， but most indexes fluctuated within a relatively stable range. RBC and HGB of Guike pig both reached the lowest levels （6.85×1012/L and 97.1 g/L） at 70 days of age， which were significantly lower than the corresponding indexes at 49， 56， 63， 84 and 91 days of age； WBC reached the lowest level （13.71×109/L） at 63 days of age， which was significantly lower than that at 49 and 84 days of age； MPV reached the highest level （17.39 fL） at 91 days of age， which was significantly higher than that at 70 and 77 days of age. This may be related to boost immunization against swine fever at 70-77 days of age， but the specific reasons remain to be investigated.
HCT refers to the volumetric ratio of erythrocytes to whole blood after centrifugation of a certain amount of anticoagulated whole blood， which is a simple method that indirectly reflects the number and volume of red blood cells[14]. Reasonable HCT can improve gas exchange inside and outside the body and enhance metabolism. Most diseases will consume red blood cells and result in HCT reduction. In this study， routine blood indexes of Guike pig， Landrace pig and Enshi black pig were compared and analyzed. The results indicated that HCT of Guike pig was significantly lower than that of Landrace pig and Enshi black pig； MCV of Guike pig was lower than that of Landrace pig and Enshi black pig； MCHC of Guike pig was higher than that of Landrace pig but lower than that of Enshi black pig； RDW of Guike pig was lower than that of Landrace pig but higher than that of Enshi black pig； RBC and PLT of Guike pig were higher compared to Landrace pig and Enshi black pig， suggesting that Guike pig had mild iron deficiency symptoms. In addition， although MID of Guike pig was slightly higher compared to Landrace pig， there was no apparent increase in WBC. Therefore， it could not be determined whether there was a viral or bacterial infection.
In the present study， routine blood indexes of Guike pig were detected and the results could provide reference data for immunological evaluation and disease resistance breeding of Guike pig. Moreover， it is necessary to detect cytokines IFN-γ， IL-2， IL-4 and IL-10 of Guike pig， analyze the polymorphisms of exon 14 and intron 8 of MX1 gene， and utilize immune indicators， antibody titers and molecular genetic markers， thus providing scientific basis for commercial production and disease prevention and control of Gryllidae pig. Conclusion
Guike pig has a certain uniqueness in routine blood indexes， which has developed a stable immune system at 49-91 days of age.
References
[1] Arosa FA， Pereira CF， Fonseca AM. Red blood cells as modulators of T cell growth and survival[J]. Current Pharmaceutical Design， 2004， 10（2）：191-201.
[2] van de VE， van DJT， Ottenhoff TH. Genetic deficiencies of innate immune signaling in human infectious disease[J]. The Lancet. Infectious Diseases， 2009， 9（11）：688-698.
[3] Beutler B. Innate immunity： An overview[J]. Molecular Immunology， 2004， 40（12）：845-859.
[4] Chen SK， Wang XF， Li S， et al. Evaluation on healthy pigs assisted by blood routine indexes[J]. Jilin Animal Husbandry and Veterinary Medicine， 2015， （3）：20-22.（in Chinese）
[5] Cheng ZX， Ni X， Han YY， et al. Comparison of eight blood indexes among domestic swine and two crossed wild boar[J]. Hubei Agricultural Sciences， 2007， 46（3）：419-421.（in Chinese）
[6] Liu JW， Zhang YJ， Li ZX， et al. Investigation on the normal values of blood routine and serum biochemistry in Changbai piglet[J]. Chinese Journal of Comparative Medicine， 2007， 17（7）：393-394.（in Chinese）
[7] Li CY， Gan ZL， Tang DY， et al. Effects of Chinese herbal feed additives on weight gain， routine blood indexes and the level immunoglobulin in swine[J]. Progress in Veterinary Medicine， 2012， 33（10）：53-56.（in Chinese）
[8] Wang HZ， Lin S， Wang YP， et al. Analyses of breeds and little effect on routine blood traits and T-lymphocyte subpopulation traits in piglets[J]. Acta Veterinaria et Zootechnica Sinica， 2014， 45（11）：1760-1766.（in Chinese）
[9] Xiang Y， Li ZM， Li JP， et al. Enshi black pig blood index measurement analysis and analysis of the correlation and CXCR4 gene polymorphism[J]. Swine Industry Science， 2015， 32（7）：130-132.（in Chinese）
[10] Guo SQ， Shen GS， Dong Y， et al. Effect of different immune process of CSF and PRRS on blood index and ratio of feed to gain in pig[J]. Feed Industry， 2016， 37（5）：39-41.（in Chinese）
[11] Pan TB， Zhang JF， Xiao ZZ， et al. Effects of different energies and proteins on growth performance and blood biochemical indexes Guike maternal line pigs[J]. Heilongjiang Animal Science and Veterinary Medicine， 2010， （19）：71-72.（in Chinese）
[12] Xie BK， Huang GY， Nong SQ， et al. Guike I synthetic line pig production performance measurement[C]. Changchun： Proceedings of the Third Meeting of Fifth Session of Pig Branch of China Association of Animal and Veterinary Medicine·Development Forum on Swine Industry Science and Technology Innovation： 2012， 166-167.（in Chinese）
[13] Luo XQ， Yang C， Huang LX， et al. Analysis of fattening， slaughter performance and meat quality traits in Guike pig[J]. Journal of Southern Agriculture， 2015， 46（1）：133-137.（in Chinese）
[14] Tian PP， Zhu LS， Ma Q， et al. The relationship of HCT between age and ESR[J]. International Journal of Laboratory Medicine， 2017， 38（2）：209-210.（in Chinese）