Am. Rota et al., EFFECTS OF STAGE OF LACTATION AND PARITY ON SOMATIC-CELL COUNTS IN MILK OF VERATA GOATS AND ALGEBRAIC MODELS OF THEIR LACTATION CURVES, Small ruminant research, 12(2), 1993, pp. 211-219
Effect of stage of lactation and parity on somatic cell counts in milk
was studied in 100 goats of the Verata breed (25 each in the first, s
econd, third and fourth lactation) free of clinical mastitis. Counts f
rom aliquot milk samples collected at 21 d intervals were used to eval
uate the parameters of a cell count curve through the lactation with a
n incomplete gamma function according to Wood (1967): Y(n) = A x n(b)
x e(cn), where Y(n) is the average somatic cell counts (SCC) in the 21
0 d lactation, expressed in millions/ml. Cell counts varied from 0.92
x 10(6)/ml in the 1st week and 0.57 X 10(6)/ml in the 5th week to 1.81
X 10(6)/ml in the 30th week of lactation. Average cell concentration
was significantly affected (P < 0.05) by parity, and did tend to incre
ase from the first (1.27 X 10(6) SCC/ml) to the fourth lactation (2.02
X 10(6) SCC/ml). The curve of somatic cell counts was the inverted im
age of the lactation curve. That is the reason why the curve was fitte
d by the incomplete gamma functions of Wood (R2 = 0.97). From their eq
uations a minimum cell concentration (-(b/c)) was deduced on the follo
wing days: first lactation, 28; second lactation, 55; third lactation,
13 and fourth lactation, 25. We observed that the estimation of infle
ction appearing in conjunction with the first and second months of lac
tation occurred in the same way as with yield and quality of milk.