GENETIC ANALYSIS OF PRODUCTION TRAITS IN GIR CATTLE 1673
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Date
2012-11
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JAU,JUNAGADH
Abstract
The production and reproduction records on 228 Gir cows
with 680 lactations sired by 52 bulls, maintained at Cattle
Breeding Farm, Junagadh Agricultural University, Junagadh, for
24 years (1987 - 2010) were studied. The data were analyzed to
study the effect of period of calving, season of calving and parity
as fixed effect and effect of sire as random effect on the
production traits viz., lactation milk yield, 300-days milk yield,
peak milk yield, lactation length and dry period, and
reproduction traits viz., calving interval and age at first calving.
Least squares means for production traits viz., lactation
niilk yield, 300-days milk yield, peak milk yield, lactation length
and dry period were 2276.60 ± 171.32 kg., 2115.89 ± 129.81 kg.,
12.31 ± 0.51 kg., 328.27 ± 12.99 days and 109.81 ± 20.20 days,
respectively. Least squares means for reproduction traits viz.,
calving interval and age at first calving were 456.36 ± 22.06 days
and 1568.08 ± 39.82 days respectively.
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The analysis of variance revealed highly significant effect of
period of calving on lactation milk yield, 300-days milk yield,
peak milk yield, lactation length, dry period and age at first
calving. While non-significant effect was observed for calving
interval. Season of calving did not affect significantly to all these
traits under study, except dry period and animals calving during
July- October had shorter dry period as compared to those
calving in other seasons. Parity of calving highly significantly
affected lactation milk yield, 300-days milk yield, peak milk
yield, lactation length, dry period and calving interval and
significantly affected age at first calving.
Lactation milk yield, 300-days milk yield, peak milk yield,
lactation length, dry period and age at first calving had periodic
trend. Lactation milk yield, 300-days milk yield and peak milk
yield showed a significant drop during 1995-2002 and thereafter
showed an increasing trend during 2003 - 2010. The Average
lactation milk yield was rise to 2667.02 kg during 2007-10.
Age at first calving had increasing periodic trend over the
years rising from 1268.33 to 1787.96 days. Appropriate
measures should be taken to improve the trait.
Lactation milk yield, 300 days milk yield, peak milk yield,
lactation length dry period and calving interval are affected by
parity. There was significant drop in the lactation milk yield,
300-days milk yield, peak milk yield, lactation length and dry
period after eighth parity.
High heritability estimates for age at first calving (0.59 ±
0-07) and moderate heritability estimate for lactation milk yield
(0.17 ± 0.04) and 300-days milk yield (0.20 ± 0.05) were obtained
in present study, indicated more importance of additive genetic
variance in phenotypic manifestation of these traits. The lower
heritability estimates for rest of the traits viz., peak milk yield
(0.11 ± 0.04), lactation length (0.04 ± 0.03), dry period (0.12 ±
0.04) and calving interval (0.06 ± 0.03) were observed in present
study.
The repeatability estimates for lactation milk yield, 300-
days milk yield, peak milk yield, lactation length, dry period and
calving interval were found to be 0.45 ± 0.04, 0.38 ± 0.04, 0.21 ±
0.04, 0.37 ± 0.04, 0.32 ± 0.04 and 0.23 ± 0.04 respectively.
Highly significant (P<0.01) phenotypic correlations were
observed between lactation milk yield and 300 days milk yield,
peak milk yield, lactation length which were 0.901 ± 0.015,
0.684 ± 0.095 and 0.74 ± 0.137 respectively. Phenotypic
correlations between lactation milk yield and age at first calving,
calving interval and dry period were 0.158 i 0.179, 0.338 i
0.283 and -0.155 ± 0.223, respectively, which were non
significant (P>0.05).
Phenotypic correlations of 300 days milk yield with peak
rnilk yield and lactation length were 0.808 ± 0.066 and 0.456 ±
0.209, respectively, which were highly significant (P<0.01).
Phenotypic correlations between 300 days milk yield and dry
period, cadving interval and age at first calving were nonsignificant
(P>0.05) and were -0.183 ± 0.217, 0.171 ± 0.269 and
0.114 ± 0.178, respectively.
Phenotypic correlations of peak milk yield with lactation
length, calving interval, dry period and age at first calving were
non-significant (P>0.05) and were 0.225 ± 0.295, 0.079 ± 0.309,
-0.147 ± 0.255 and 0.104 ± 0.200, respectively. Phenotypic
correlations between lactation length and dry period, calving
interval and age at first calving were non-significant (P>0.05) and
were -0.065 ± 0.346, 0.501 ± 0.432 and 0.191 ± 0.234,
respectively. Phenotypic correlations of dry period with calving
interval was highly significant (P<0.01) and was 0.520 ± 0.178.
Phenotypic correlations of dry period with age at first calving was
0.021 ± 0.195, which was non-significant (P>0.05).
Genetic correlations of lactation milk yield vj^ith 300 days
milk yield, peak milk yield and lactation length were 0.985 ±
0.015, 0.813 ± 0.095 and 0.839 ± 0.137, respectively, which
were highly significant (P<0.01). Genetic correlations of lactation
milk yield with dry period, calving interval and age at first
calving were non-significant (P>0.05) and were -0.454 ± 0.223, -
0.003 ± 0.283 and 0.144 ± 0.179, respectively.
Genetic correlations between 300 days milk yield and
lactation length and peak milk yield were 0.744 ± 0.209 and
0.868 + 0.066, respectively, which were highly significant
(P<0.01). Genetic correlations between 300 days milk yield and
calving interval, dry period and age at first calving were non
significant (P>0.05) and were -0.100 ± 0.269, -0.472 ± 0.217 and
0.006 ± 0.178, respectively.
Genetic correlation of peak milk yield with lactation length
was 0.606 ± 0.295, which was highly significant (P<0.01).
Genetic correlation of peak milk yield with age at first calving,
dry period and calving interval were non-significant (P>0.05) and
were 0.069 ± 0.200, -0.382 ± 0.255 and -0.009 ± 0.309,
respectively.
Genetic correlation between lactation length and dry
period, calving interval and age at first calving were -0.518 +
0.346, 0.016 ± 0.432 and 0.752 + 0.234, respectively, which
were non-significant (P>0.05). Genetic correlation of dry period
with calving interval was 0.712 ± 0.178, which was highly
significant (P<0.01). Genetic correlation of dry period with age at
first calving was 0.058 ± 0.195, which was non-significant
(P>0.05).
Environmental correlation of lactation milk yield with 300
days milk yield, peak milk yield, lactation length, dry period, age
at first calving and calving interval were 0.795 ± 0.015, 0.606 ±