The objective of this study was to analyze the association of somatic cell score (SCS) with milk, fat and protein yields across parities. Records of production traits and somatic cell counts (SCC) from first, second and third parity that were collected by the Animal Breeding Center of Iran from 1993 to 2010 were used. All animals were grouped into six classes according to SCC and production traits were evaluated in these SCC classes. To obtain an approximate normal distribution, SCC records were transformed on the base of Loge to somatic cell score (LSCS, the lactation mean of the natural log of test-day somatic cell count). A single trait animal model that LSCS was fitted as covariate was used to assess relations of SCS with production traits in fist, second and third parities. Effect of SCS on production traits in all of parities was negative and significant (P<0.05). Ranges of depressing effects on milk, fat and protein production were 107.78-220.41, 2.32-7.08 and 2.1-5.2 kg per 1 unit increase in SCS.

Bulk milk somatic cell count (SCC), somatic cell score (SCS) and total bacterial count (TBC) are the most important milk health parameters. The aim of this study was to investigate SCC, SCS and TBC in a dairy herd of Khuzestan province. A general linear model (GLM) procedure was used for analyzing of data, The result showed effects of year and month are significant on variation of SCC, SCS and TBC. The highest and lowest see and SCS were observed in September and January respectively and the highest and lowest TBC was observed in January and May. The result showed SCC, SCS and TBC increased significantly over time, and it implies the quality of milk decreased in mentioned years. It seems to control this upward movement applying new policies is necessary. In addition, high total bacterial count showed pasteurization is necessary to produce more healthy milk.

The objective of this study was to estimate variance components, genetic and phenotypic trends for somatic cell score. Dataset that collected by the Animal Breeding Center of Iran was used in this study. Data file included 850, 729 test day records of somatic cell counts (SCC) on 32, 955 cows from lactations one to four, in 472 herds, gathered from years 2002 to 2013 in Iran. A test day repeatability animal model was used to estimate the genetic parameters and variance components using ASReml. The heritability was estimated 0. 176. Estimated repeatability (± SE) for within (rwit) and between (racr) parities were 0. 362± 0. 006 and 0. 230± 0. 002, respectively. The genetic and phenotypic trend based on regression of average breeding values of SCS on year of birth, was-0. 0246 and-0. 047, respectively. This trend could be due to genetic improvement and mastitis management control programs that are widely being used across the dairy farms in country.

Mastitis is a very important economic disease in dairy cattle. The TNFα gene as a key gene involved with mastitis and its polymorphisms and expression was evaluated as well as its correlation with somatic cell score (SCS). The gene expression of bovine TNFα profiling in Holstein cattle was also assessed. For this purpose, one hundred Holstein lactating cows were selected based on their breeding values for milk production, fat and somatic cell scores. Then cows based on their residual values for somatic cell scores were divided into two resistant and susceptible groups and 5 ml blood samples were collected from each animal. Selective genotyping of two target groups of susceptible and resistant animals to mastitis was done using PCR-RFLP approach, and then statistical association study was taken between identified genotypes and phenotypes records. Then, gene expression profiling between resistance and susceptible groups was evaluated using Real time PCR method. Results at this research showed significant correlation between TNFα gene polymorphism and values residuals of SCS (P<0. 01). Gene expression was difference between the susceptible and resistance groups which, can be indirectly reflect relationships between screen mutations and gene expression pattern. So that the highest gene expression was belonged to BB genotype. As the final message of the present study, AA genotype may play a role and associated with relative resistance phenotype to mastitis in the studied population.

Genetic parameters were estimated for somatic cell score (SCS) in dairy cattle of Iran using test day records. The records of first lactation were extracted from the database of National Animal Breeding Center for cows calved between 2001 and 2010. Data included 222923 test-day records, obtained from 29668 animals distributed in 100 different herds. Estimates were carried out through Gibbs sampling procedures and using a random regression test-day model. Lactation curve were described in the model with orthogonal Legendre polynomials on days in milk. In order to correct for heterogeneity effect of residual variance, lactation period (5 to 365 days in milk) was classified into 10 groups with unequal distances. According to the results, residual variance was highest at the beginning and it was steady and decreased slowly from the second months to the end of lactation. Low residual and permanent environment variances and high genetic variance were lead to increase of heritability at the end of lactation. The lowest and the highest of heritability were at days 68 (0.031) and 365 (0.098), respectively. Genetic correlations between individual test-day records were high for adjacent tests and decreased as the interval between tests increased. Daily breeding values and genetic curve across lactation were produced for all animals using predicted regression coefficients. Estimation of genetic and phenotypic trends for SCS were -0.0025 and -0.1075, respectively (P<0.01). The results show a desirable improvement for somatic cell score at genetic and phenotypic levels.

Lactoferrin and CXCR1 genes are involved in immune responses related to mastitis infection. In this study, the polymorphism and association of lactoferrin (LF) and CXCR1 genes with milk somatic cell counts, as an indicator for mastitis detection, were investigated in Guilan native cow (Taleshi breed) using DNA blood samples of 100 cows from three different geographical zones (west, center, and east of Guilan province). The LF gene with a 301 bp fragment and CXCR1 with a fragment of 311 bp were amplified through PCR by using their specific primers. Then LF polymerase chain reaction (PCR) product was digested by EcoRI enzyme due to a single nucleotide polymorphism (SNP) at the related position (T>C) in intron 6 of LF and CXCR1 PCR product by BaeGI enzyme due to G > C SNP at position +735. Two alleles and three geno-types were observed for both genes in the studied populations. The observed genotypic frequencies of AA, AB, and BB were 52, 39, and 9% for LF and 67, 12, and 20% for CXCR1 locus, respectively. Three geno-types of LF locus were under Hardy-Weinberg equilibrium (P˃ 0. 05) but it was not for CXCR1 locus. The mean of somatic cell counts was 138 × 103/mL, much lower than the reported data of pure-bred and cross-bred cattle. Although there was no significant association (P<0. 05%) between LF genotypes and somatic cell score (SCS), there was a tendency for association (P<0. 1). The CXCR1c. +735 genotype had a signifi-cant association (P<0. 05) with SCS. Sampling from different regions did not show a significant effect on SCS. The fix effects including lactation month, age, and lactation number had also no significant effect on SCS of the studied native cow.

The objective of this research was to estimate the genetic parameters and trend of somatic cell count in Holstein cows of Iran using test day records. The phenotypic the used data consisted of were consisting of 407167 first lactation test day records the which were collected by the center of Animal Breeding and Livestock Production Improvement center of Iran during 2009 to 2013. Somatic cell count was transformed to Somatic cell score using logarithm transformation method. The genetic parameters were estimated using random regression models with Bayesian statistical method based on Gibbs sampling. The results revealed that the observed trend for additive genetic variance and permanent environmental were similar high in early lactation compared to other days. The heritability was estimated between 0. 023-0. 065 for somatic cell score. Repeatability showed highest changes at the start and the end of lactation. Additive genetic correlations were estimated for days 5 and 305. The result showed high variation in genetic trend of somatic cell score in different years, without an specific trend.