Contagem de Células Somáticas e Produção de Leite em Vacas Holandesas Confinadas 1

ABSTRACT - The relationship between milk somatic cells count (SCC) and milk yield has been the aim of countless researchesin several countries; however, in Brazil, the literature related to this subject is scarce. Therefore, the objective of this st udy is to verifyif the losses in milk yield due to SCC increase are proportional to the yield, or absolute (independent of it) and starting fro m which SCC,the losses become evident. For this study, 13.725 observations were used, collected monthly from 6 different herds, from Januar y/2001up to June/2002. The analysis model, for lactation curve, was based upon the incomplete gama function, considering the effects of lactationorder, herd and calving season. The SCC entered in that model in two ways: as multiplicative factor (representing relative loss es) andas addictive factor (representing absolute losses). The best model was chosen based on the information criteria of Schwarz (BIC ). It isconcluded that the losses are absolute, becoming evident from 17.000 cells/mL, and they are 238 and 868 mL/day for each increas e ofone unit in the natural logarithm scale, starting from that SCC, respectively, for primiparous and multiparous.Key Words: SCC, subclinical mastitis, bovine mastitis, milk yield