Implementation of SCC breeding values in Italian Jersey breed

In the framework of the LATTeco project, ANAFIJ (Associazione Nazionale Allevatori della Razza Frisona e Jersey Italiana) has been working on improving animal welfare, biodiversity and sustainability. Focusing on animal welfare, ANAFIJ has implemented a genetic evaluation for somatic cell count (SCC) in the Italian Jersey population. The aim of this study is to describe this implementation which became official in December 2020. It is expected that breeding values for SCC will help farmers to produce a progeny more resistant to mastitis, with a consequent reduction of veterinary costs and a valorisation of milk in quality payment systems. The dataset included 284,904 records of SCC collected on 19,305 cows belonging to 774 herds during the official test day milk recording program. Data ranged from 2005 to 2016. Means of SCC and somatic cell score (SCS), calculated as 3+log2(SCC/100), were 277.47±677.43 cells/µL and 3.14±1.76. Bulls’ breeding values were estimated using a repeatability animal model which included the fixed effects of parity (first, second and third lactation), the season of calving (4 classes, 3 months each), days in milk (10 classes of 30-d each, ranged from 4 to 305 d), and herd-test-day (26,866 records) as a contemporary group. The random effects were an additive genetic animal, permanent environment and the residual. Breeding values for 187 bulls with a minimum of 10 daughters in at least 10 herds were estimated and they were referred to ANAFIJ genetic base, which is updated every 5 years and at the moment of the study, included animals born between 2010 and 2015. Somatic cell score was standardised to mean 100 and standard deviation 5. Breeding values reliability averaged 0.80±0.13 and the mean of daughters’ phenotype for SCC was equal to 275.41±92.81 cells/µL. Bulls were divided into 3 groups according to their breeding values for SCS: as expected, bulls with higher ebvs had lower mean SCC; while a decrease in ebvs was associated with increased SCC. In January 2021, the new breeding value was submitted to Interbull for the test-run routine to validate it; this will allow ANAFIJ to have an international result for the SCC breeding value of the Italian Jersey population.