Acta Vet. Brno 2011, 80: 73-80
Analysis of lactation curves, milk constituents, somatic cell count and urea in milk of cows by the mathematical model of Wood
Analysis of lactation curves of milk, basic milk constituents, somatic cell count and urea in milk provide sufficient information for efficient dairy herd management and also is significant in genetic evaluation. The aim of the study was to apply the Wood’s model to fit lactation curve of milk yield as well as fat, protein, dry matter, lactose, somatic cell count and urea in cows’ milk. This study was conducted on dairy cows of Montbéliard (n = 686) and Polish Holstein-Friesian (n = 933) breeds. We analyzed data on the above mentioned milk constituents in the samples collected between 1995 and 2007. Data from 5,034 lactations were collected. Type C1 of the curve typical for standard lactation was the most frequent when daily milk yield, lactose and urea were analyzed. However, curves of fat protein and dry matter were described as type C4. The Wood’s model showed the highest accuracy when milk yield and protein content were investigated; poor fitting was observed for fat content. The Wood’s model brought better accuracy for Polish Holstein-Friesian cows compared to Montbéliards. Precision of mathematical models fitting is R2 (adjusted determination coefficient). The highest values of R2 were noticed when lactation and protein curves were investigated. The lowest R2 was determined for urea and somatic cell count.
Keywords
Montbéliard, Polish Holstein Friesian, linear regression, dairy cows.
