Phenotypic correlations between longevity measures and age at first calving of dairy Zebu cattle

Indirect selection for longevity has been used through the selection of other traits of
economic importance early expressed and easily measured, such as age at first calving
or first calving interval (Miglior et al., 2005). Despite significant economic importance,
few studies are reported in the literarure on longevity in Zebu animals. The objective of
this study was to estimate the phenotypic correlation among different measures of
longevity and age at first calving of dairy Zebu cows. Age at first calving of cows was
considerate as the interval in days from birth to its first parturition. The average age at
first calving was 1531 days, ranging from 458 to 4003 days. Longevity was defined by
two measures: 1) as the interval in days from date at first calving to date of culling
(Long_1); and 2) as the interval in days from date at first calving to date at last calving
(Long_2). Animal information was used with birth occurred between 1985 to 2012,
with at least three births. Phenotypic correlations were obtained by the CORR procedure
of SAS(R) (2003). Significant (P < 0.01) and negative correlations were obtained
between age at first calving and Long_1 (-0.11) and between age at first calving and
Long_2 (-0.13). The increase in age at first calving negatively affects longevity.
According to Balieiro et al. (2003), more precocious cows have elevated genetic
potential for milk production, which would justify its longer permanence in the herd,
being discarded by low production and not for mastitis problems, hull, among others,
since the Zebu are more adapted animals. It was also observed that increasing age at
first calving affects the interval between the first and last calving (Long_2), that is,
animals that initiate later reproductive life remain less time in productive herd life. The
Long_1 and Long_2 showed significant (P < 0.01) and high positive correlation (0.79).
Phenotypic correlation between age at first calving and longevity indicated that
precocious animals are more long-lived. However, it is necessary more studies on
longevity and easily measured characteristics obtained at the beginning of the
productive life of the animal in order to identify early longer-lived animals.