E de la Garza Institute for Goat Research Langston University
Workshops & Field Day Newsletter Newsletter Subscription Demonstrations Demonstrations Langston University Research Building
Goat Menu




Adjustment factors for fat, protein, and somatic cell count for goat milk using different species-specific calibration standards

T.A. Gipson, and T. McKinney

E (Kika) de la Garza Institute for Goat Research, Langston University, Langston, OK

Currently, test-day samples of dairy goat milk are analyzed for fat, protein, and somatic cell count with laboratory equipment calibrated for cow milk, even though research has demonstrated that these measures are biased. The objective of this research was to examine breed, parity, and stage of lactation effects on this bias and to develop appropriate adjustment factors. Langston Dairy Herd Improvement (DHI) laboratory equipment was calibrated using both cow and goat milk standards. During 2001, 3,110 test-day samples from 875 does of six different breeds and 84 herds were analyzed for milk fat, protein, and somatic cell count with both calibrations. Of the 875 doe records, 373 were first parity, 181 second parity, 140 third parity, and 174 fourth or greater parity; and 196 were Alpine, 161 LaMancha, 284 Nubian, 45 Oberhasli, 124 Saanen, and 65 Toggenburg. Lactation was divided into 6 stages of 50 days according to days in milk (DIM). Differences (DIFF) in standards (cow vs goat) were analyzed as a repeated measures design using mixed model analysis. The statistical model included doe identity, breed, parity and stage of lactation with doe identity nested within breed as a random effect. There was no effect (P > 0.10) of breed or parity, on DIFF for fat, protein or somatic cell count. Stage of lactation affected (P < 0.01) DIFF for protein but not for fat or somatic cell count. Test-day samples analyzed with goat standards were regressed on test-day samples analyzed with cow standards to obtain adjustment factors. Multiplicative adjustments factors (cow standards adjusted to goat standards) were 1.027 for fat (R2 = 0.85), 1.164 for protein with DIM less than or equal to 100 d (R2 = 0.94), 1.125 for protein with DIM greater than 100 d (R2 = 0.99), and 0.937 for somatic cell count (R2 = 0.96). It appears that the bias in goat test-day samples analyzed under conventional DHI laboratory procedures can easily be alleviated using simple adjustment factors.


Extension Activities   |   Research Activities   |   Other Activities
Library Activities   |   Quiz   |   Search   |   About Us   |   Contact Us   |   Faculty & Staff
Research Extension Home   |   Top of Page

Copyright© 2000 Langston University   • Agricultural Research and Extension Programs
P.O. Box 730  • Langston, OK  73050 • Phone 405.466.3836