Abstract
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.
Highlights
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 is significant in genetic evaluation
Data from dairy record system and milk constituents curves as well as somatic cell count (SCC) and urea can be incorporated into mathematical models (Wood 1976; Stanton et al 1992; Pollot 2004; Silvestre et al 2009)
As the modeling ability of Wood’s function referring to traits others than milk production hasn’t been confirmed in scientific literature, the aim of the study was to investigate the ability of the model to fit lactation curves of milk yield (MY), fat (F%), protein (P%), dry matter (DM%), lactose (L%), somatic cell count (SCC) and urea (U) in cows’ milk of two breeds as well as assessment of the quality and applicability of its combined outputs
Summary
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 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. The main advantage of those methods is that the analysis is based on real data, not estimated or predicted on lactation yields (305 – day) and less biased (Grzesiak et al 2006) Another advantage of using TDM is the access to valuable information of lactation curves and persistency. Data from dairy record system and milk constituents curves as well as somatic cell count (SCC) and urea can be incorporated into mathematical models (Wood 1976; Stanton et al 1992; Pollot 2004; Silvestre et al 2009). Many authors confirmed the influence of breed, parity and production system on the shape of lactation curves (Wood 1980)
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