MILK PRODUCTION

MATERIAL AND METHOD
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MILK PRODUCTION
Data from composition of milk from 301 buffaloes served as sample for this study, with a total of 2,833 observations over
a period of 18 months (May/2008 to October/2009). The animals were from a commercial herd, milked mechanically, and
located in a region with harsh climate, northeast of Brazil. Concentrations of fat (F), lactose (L), protein (P), solid (S),
somatic cell count (SCC) and somatic cell score (SCS) were measured. A polynomial linear regression model was used as
variable for time, with its degree determined by the model with all significant regression coefficients:
Where is the observed value for the variable at the moment i, is the intercept and are the regression
coefficients for the variable year-month, is the random error associated with it. The variable SCS was also analyzed by
means of covariance functions (Variance Component - VC, Compound Symmetry - CS, Heterogeneous Compound Symmetry
- CSH, Autoregressive - AR (1), Heterogeneous Autoregressive - ARH(1), Huiyn-Feldt - HF, Toeplitz - TOEP, Heterogeneous
Toeplitz - TOEPH), to interpret the relationship between the different observations:
Where is the value observed for somatic cell scores at time i, is the intercept and is the regression coefficient for
the variable year-month, is the random error associated with each observation being considered associated with the
different observations through the functions covariance.
RESULTS AND DISCUSSION
The best polynomial models for the variables were: S – linear, F - quadratic, L, SCC and SCS - cubic; P - grade four
(Table 1). The conclusion is that variations found are consistent with expectations for the region, based on
nutrition and pasture (F, L, P) and the influence of climate on the occurrence of subclinical mastitis (SCS and SCC).
Table 1 – Estimates of the parameters of the regression equations for the concentrations of the components
*All the parameters were significant at 1% (P < 0.01)
Proceedings 9 th World Buffalo Congress