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Genetic parameters for somatic cell count and clinical mastitis in the first lactation of Iranian Holstein cattle
Data comprised records of milk production and clinical mastitis (CM) belonged to Holstein cows in North-East of Iran. Information included milk production; calving and recording dates, somatic cell counts (SCC), pedigree, and mastitis. Log2-transformed of SCC was used for normalization. Environmental effects were analyzed by linear and logistic regressions for SCS and CM, respectively. Random regression and logistic bi-variate models were used to analyze SCS and CM (co)variance components. Model included fixed effects, additive genetic effect and common permanent environmental effects as random effects with 5-degree of Legendre. SCS or CM was increased by increasing of lactation number or higher temperature. Heritability of SCS ranged from 0.043 to 0.136; although heritability of CM was lower (0.037). Genetic correlation was positive and high (0.712). Regarding to low heritabilities, genetic gain against SCS could be slow but it is stable and does not include expenditures of treatments.
Keywords:
SCS,
Mastitis
