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Asian-Australas J Anim Sci > Accepted Articles
DOI: https://doi.org/10.5713/ajas.20.0347    [Accepted] Published online October 13, 2020.
The effect of extended lactation on parameters of Wood’s model of lactation curve in dairy Simmental cows
Tomáš Kopec1  , Gustav Chládek1  , Daniel Falta1,*  , Josef Kučera2  , Milan Večeřa1  , Oto Hanuš3 
1Mendel University in Brno (FA). Zemědělská 1, 613 00 Brno, Czech Republic
2Czech Moravian Breeders Association. Benešovská 123, 252 09 Hradištko, Czech Republic
3Dairy Research Institute Ltd. Ke Dvoru 12a, 160 00 Prague, Czech Republic
Correspondence:  Daniel Falta, Tel: +420 545 133 214, Fax: +420 545 133 213, Email: daniel.falta@mendelu.cz
Received: 18 May 2020   • Revised: 24 July 2020   • Accepted: 13 September 2020
This study was focused on the estimation of parameters of Wood’s model and description of the lactation curve using the cows which were lactated over 24 months on the first lactation.
The database included 1 333 pure-bred dairy Simmental primiparous cows which lactated for 24 months (732 days). The initial dataset entering the procedure of assessment of parameters of Wood’s function included 35 826 milk yield records. Milk yield was recorded throughout lactation, with the earliest record taken on day 6 and the latest on day 1 348 of lactation. This dataset was used for the assessment of parameters a, b, c of Wood’s model using the non-linear statistical procedure. These parameters were estimated for different length of lactation. The assessed parameters were used for calculation of some characteristics of lactation curves.
The lowest value of a parameter (15.2317) of Wood’s model of lactation curve was found out in lactations up to 305 days long, contrary to b and c parameters which were highest in those lactations (0.1029 and 0.0015, respectively). The maximum value of a parameter (17.4329) was found out in lactations up to 640 days long, unlike b and c parameters which were minimal in those lactations (0.0603 and 0.0010, respectively).
It can be concluded that the parameters of Wood’s model and the shape of lactation curve are changing with the growing number of milk yield records. Also, the assessed parameters revealed a significant milk production potential after 305 days of lactation.
Keywords: Dairy Cows; Simmental Breed; Wood´s Function; Lactation; Milk Yield

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