Individual dairy curd production and association analysis with 14 candidate genes in Italian buffalo

The genetic merit of Italian buffaloes is mainly related to theability of producing mozzarella cheese. This trait is measured by the estimated mozzarella production (PK M index) according to Altiero et al. (1989). Several studies have shown that PKM based only on milk yield, fat (FP) and protein percentage (PP) may over-or under- estimate the real mozzarella yield. The individual curd production (ICP) is proposed as index of the mozzarella making ability. Values were compared with estimated PKM. Associations between ICP and 14 loci related to milk traits (ACACA, BLG, CSN1S1, CSN1S2, CSN2, CSN3, LEP, LPL, LTF, OXT, OXTR, PRL, PRLRand SCD) were tested. Idividual milk samples of 233 Italian river buffaloes were collected monthly along the whole lactation. A total o f36 variable swere measured: Fat(FP),protein(PP) and lactose % (LP), milk coagulation properties (r,clottingtime;k20,curd firming time; a30, curd firmness at 30min), SH, pH, Individual Curd Production at 24h (ICP24), etc. Cows were genotyped for published and new SNPs found in the explored genes. Associations between phenotypes and candidate gene polymorphisms were tested using a mixed linear model. Two out of 16 markers in 2 out of 14 investigated genes gave significant associations with ICP24 and FP: OXTR (g.129C>T) and SCD (g.-461A>C). The genotype AC at SCD showed an over-dominance effect with a higher increase vs AA of 13.15 g/kg milk (p=0.015) for ICP24 and + 0.54 FP (p=0.010). The estimated PKM/ICP ratio showed that the PKM under-estimates the prediction of mozzarella yield ( on average 0.929).These data confirm the findings of Parlato and Zicarelli (2015) on the necessity of a new prediction model, and offer useful indication for the application of MAS programs in buffalo.