TITLE:
Evaluation of the Genetic Relationship between Longevity and Growth, Milk Yield and Fertility Traits in the Sahiwal Breed in Kenya
AUTHORS:
Benjamin Musyimi Musingi, Leah Mumbi Mahianyu, Dorcas Mutheu Musingi
KEYWORDS:
Correlated Response, Fertility, Genetic Correlation, Longevity, Sahiwal
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.12 No.1,
November
10,
2021
ABSTRACT: Direct selection for longevity results in improved health and fitness and
even milk production of cows. However, longevity is lowly heritable and
phenotypic information is obtained at the end of an animal’s life. Traits
expressed early in life and which are favorably correlated to longevity can be
useful in selecting for this trait. The aim of this study was to estimate
genetic correlations between longevity and age at first calving, first
lactation calving interval, number of services per conception, first lactation
milk yield, and first parity lactation length. Heritability estimates for
measures of longevity were also calculated. The measures of longevity were time
between birth and last milking in days (Long1), time between first calving and
last milking record in months (Long2), number of lactations initiated (Long3),
and total number of days in lactation over all lactations (Long4), total milk
yield over all lactations (kg) (Long5). A series of five-variate animal models
were fitted to estimate the nature and magnitude of genetic and phenotypic
correlations between each measure of longevity and the fertility and production
traits. Genetic correlations between measures of longevity and age at first
calving, calving interval and number of services per conception were negative
ranging from -0.14 ± 0.05 to -0.96 ± 0.06, -0.06 ± 0.03 to -0.67 ± 0.08 and -0.02 ± 0.02 to -0.73 ± 0.34, respectively. Correlations between measures of
longevity and first lactation milk yield ranged from 0.88 ± 0.01 to 0.97 ±
0.03. Those with first parity lactation length ranged from -0.10 to 0.72.
Long1, Long4 and Long5, which measure time between birth and last milking day,
total number of days in lactation over all lactations and total milk yield over
all lactations (kg), respectively, had the highest heritability estimates.
These three could therefore be used to directly select for longevity. Among the
traits studied, first lactation milk yield and age at first calving had the
highest genetic correlation with measures of longevity. Therefore, first
lactation milk yield and age at first calving could, therefore, be used to indirectly select for longevity.