The effect of paragenetic factors on performance traits in complete lactations in Simmental cows

Abstract

nema

The effect of systematic factors on milk yield in Simmental cows over complete lactations

“…The age at first conception as a continuous factor had a statistically very highly significant (P<0.001) effect on the milk, milk-fat and 4% FCM production, and an insignificant effect (P>0.05) on the duration of complete lactations and their milk-fat content, as confirmed by studies of Petrović et al (2005). An insignificant (P>0.05) random effect of the age at first conception on milk-yield traits over complete lactations was reported by Djurdjevic (2001) and Djurdjevic et al (2002).…”

“…The highest milk and milk-fat production, primarily due to the longest period of lactation, was recorded in the autumn season. Maximum production is achieved in winter and spring, and minimum in summer and autumn, the fact reported by most authors (Miščević, 1995, Perišić, 1998, Kučera et al, 1999, Petrović et al, 2005, Panić, 2005.…”

“…Highly significant and very highly significant effects of the order of lactation on milk and milk-fat production were reported by most researchers. Furthermore, most authors found that the order of lactation did not affect significantly (P>0.05) the milk-fat content (Perišić, 1998, Djurdjevic, 2001, Gaydarska et al, 2001and Panić, 2005, as opposed to Petrović et al (2005), who determined a very highly significant effect (P<0.001).…”

“…Therefore, the calving season effect should be included in the model used in estimating the breeding value of dairy cows. Most authors (Ugur et al, 1995, Petrović et al, 1997, Saveli, 1997, Perišić, 1998, Kučera et al, 1999, Rychen, 1999, Djurdjevic, 2001, Gaydarska et al, 2001, Singh et al, 2001, Petrović et al, 2005, Panić, 2005 reported significant (P<0.05), highly significant (P<0.01) and very highly significant (P<0.001) effects of the calving season on the milk production and milk-fat yield, as opposed to few authors, such as Chladek and Kucera (2000), who underlined that the calving season did not affect significantly (P>0.05) the production traits of complete lactations. There is a great diversity of results on the effect of calving season on milk-fat content.…”

“…There is a great diversity of results on the effect of calving season on milk-fat content. Namely, the effect of the season was reported to be either insignificant (Petrović et al, 1997, Perišić, 1998, Đurđević, 2001, Petrović et al, 2005 or significant (Miščević, 1995, Singh et al, 2001, highly significant (Panić, 2005) and very highly significant (Gaydarska et al, 2001).…”