Abstract
Longevity traits, lifetime milk and calf productivities are one of the primary interests of dairy cattle producers. We used lifetime data of 523 crossbred dairy cows that born between 1980 and 2003 in the central tropical highlands of Ethiopia with the purpose to evaluate longevity traits and associated lifetime milk and calf productivity. Based on the type of sires used and level of exotic gene inheritances, the crossbred dairy cows were classified in to six genetic groups. These include F1 Friesian x Boran (F1 FxBo), F1 Jersey x Boran (F1 JxBo), F2 Friesian x Boran (F2 FxBo), F2 Jersey x Boran (F2 JxBo) and 75% Friesian and Jersey inheritances. A Generalized Linear Model in the statistical analysis system (SAS, 2004) was used to analyze the data. The overall least squares means ± s. e. for total life (TL), herd life (HL), productive life (PL), lifetime milk yield (LTMY) and lifetime calf crop production were 4036 ± 126.3 days, 2675.74 ± 201.7 days, 1951.00 ± 173.8 days, 10460.6 ± 1117.4 L and 5.70 ± 0.2 calves, respectively. The overall least squares means ± s. e. for lifetime milk yield per day of total life (LTMY/TL), lifetime milk yield per day of herd life (LTMY/HL) and lifetime milk yield per day of productive life (LTMY/PL) were 2.56 ± 0.2, 3.97 ± 0.3 and 5.26 ± 0.3 L, respectively. In conclusion, first generation crosses of all types, particularly those sired by Jersey semen were superior in all the lifetime performance traits considered in this study while second generation (F2) crosses were inferior in all the lifetime productivity indicators. Key words: Herd life, lifetime milk yield, longevity, productive life.
Highlights
Longevity is one of the economically most important functional trait in dairy cattle populations
The entire lifespan is defined as longevity or total life and part of lifespan from first calving to disposal from the herd is defined as herd life
First generation Jersey (F1) crosses had significantly longer herd life (HL) (P
Summary
Longevity is one of the economically most important functional trait in dairy cattle populations. The definition given to the term longevity is inconsistent in several literatures It has been defined as the number of lactations completed (Ibeawuchi, 1984), length of productive life (Arthur et al, 1992; Enyew et al, 1999), the entire lifespan from birth until disposal from the herd (Chaudry and Shafiq, 1995) and survival to certain lactations (Brotherstone et al, 1997; Jairath et al, 1998). Productive life is usually defined as the total number of days that dairy cows stay in milking in their entire lifespan. This lifespan classifications patterns seem more informative and used throughout this report
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