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South African Journal of Animal Science

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Lactation curves of Holstein-Friesian and Jersey cows in Zimbabwe

E Collins-Lusweti

Abstract


Mean daily milk yield for 478 Holstein-Friesian cows from two herds, recorded between 1984-1985, and for 218 Jersey cows from two herds, recorded between 1984-1985, were used to estimate lactation curve parameters for Wood's gamma function: Yn = A nbe-cn. Yn is the predicted average daily milk yield in the nth week; A is a scalar representing 'starting yield'; and e is the base of natural logarithm. The values of b and c (lactation curve constants describing the rates of rise to and decline from peak lactation, respectively), lactation persistency (s), goodness of fit (R2) and projected 44 week milk yield were estimated. The analysis of variance indicated significant effects (P<0,01) of herd, parity and season on most of the lactation curve parameters in both breeds. The year effects were significant (P<0,05) in the Jersey but non-significant (P>0,05) in the Holstein-Friesian. The use of monthly or weekly milk yield totals to calculate mean daily yield had highly significant effects (P <0,01) on the lactation curve parameters of the Jersey.

Die gemiddelde daaglikse melkproduksie van 478 Holstein-Frieskoeie uit twee kuddes, vir die tydperk 1984-1985, en van 218 Jerseykoeie uit 2 kuddes, vir die tydperk 1984-1986, is gebruik om die laktasiekurwe parameters vir Wood se gammafunksie te bereken: Yn = A nbe-cn. Yn is die beraainde gemiddelde daaglikse melkproduksie in die nde week, A verteenwoordig aanvangsproduksie en e is die grondtal van die natuurlike logaritme. Die waardes van b en c (laktasiekurwe konstantes wat, respektiewelik, die styging voor en daling na pieklaktasie aandui), laktasie volhouvermoë (s), akkuraatheid van passing (R2) en voorspelde 44-week melkproduksie is bepaal. Die variansieanalise het betekenisvolle effekte (P<0,01) aangedui vir kudde, pariteit en seisoen vir meeste van die laktasiekurwe parameters by beide rasse. Jaareffekte was betekenisvol (P<0,05) by die Jersey, maar nie betekenisvol (P>O,05) by die Holstein-Fries nie. Die gebruik van maandelikse of weeklikse melkproduksie totale om gemiddelde daaglikse produksie te bereken, het hoogs betekenisvolle effekte (P<0,01) op die laktasiekurwe parameters van die Jersey gehad.

Keywords: Milk production, lactation curves, Holstein-Friesian, Jersey.




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