Effect of somatic cell count on composition and hygiene indicators of bulk tank milk

Abstract

This study evaluated the effect of somatic cell count (SCC) on composition and hygienic quality of dairy herd bulk tank milk – specifically, the effect of SCC of bulk tank of dairy herds on composition (fat, protein, total solids, nonfat dry solids) and on total bacterial count (TBC), psychrotrophic count (PC) and coliform count (CC) were evaluated. A total of 230 dairy herds located south of Minas Gerais and west of São Paulo were selected based on SCC geometric mean obtained from five monthly analyses preceding the start of the sampling. The dairy farms were classified according to SCC in three groups: low (< 250,000 cells/mL, n = 84), medium (> 250,000 and < 750,000 cells/mL, n = 79) and high
SCC (> 750,000 cells/mL, n = 67). After herd selection, bulk tank milk samples were collected every 14 days for three months totaling 1380 samples, which were subjected to analysis of composition, TBC, PC, and CC. A decrease of TBC and CC was observed in herds with low SCC; however, herds with medium and high SCC had an increase in fat, crude protein, and total solids contents. A medium correlation was observed between TBC and PC (r = 0.6215), and also between PC and CC (r = 0.3692). Based on hygiene indicators and milk composition, a low and negative correlation between TBC and fat (r = -0.0585), PC and fat (r = -0.0585), and PC and total solids (r = -0.0662) was observed. Dairy herds with SCC < 250,000 cells/mL had higher bulk tank milk hygienic quality; however, considering the composition, herds with higher SCC produced higher milk fat and protein concentration.