Genetic and environmental effects on age at first calving and calving interval of naturally bred Boran (zebu) cows in Ethiopia

Abstract

Twenty-four years of data from a Boran cattle breeding and improvement ranch in the Rift Valley of Ethiopia were used to study the influence of genetic and environmental factors on age at first calving (AFC) and calving interval (CD using an individual animal model. The mean AFC and Cl were 41-8 months and 442 days, respectively. The h 2 values for AFC were 0-062 and 0-075 when estimated on the original and selected data, from which cows that did not calve after 5 years of age were deleted, respectively. The h 2 values for CI were 0-037 and 0-043 when estimated on the original and selected data, from which cows with AFC higher than 5 years and CI longer than 2 years were deleted, respectively. The corresponding c 2 values (ratio of permanent environmental variance to total) were 0-031 and 0-028 for the respective data sets. Parameter estimates of the original data from bivariate analysis were 0-012 (h 2 ), 0-065 (h 2 ), -0-054 and -0-176 for first CI, AFC, their genetic and environmental correlation, respectively. The h 2 values estimated in a bivariate analysis of the first three CIs varied between 0-002 and 0-093. Year and season had significant effects on both traits. The annual genetic change for both traits was not significant while the solutions for year effects were highly variable. The regression of the solutions of year effects for AFC on year showed that it increased by about 10 days while the variation in CI was due to random year to year fluctuation.

Milk yield and reproductive performance of dairy cattle under smallholder management system in North-eastern Amhara Region, Ethiopia

“…The observed CI (457 days) for indigenous cows in this study is close to the report of Haile et al (2009) for Boran cattle (435 days) and longer than the 366 to 435 days reported for Horro (Mulugeta et al 1991) and 411 to 420 days for Arsi (Negussie et al 1998) in Ethiopia. The 450 days of CI found for crossbred dairy cows in the present study was very close to 442 days reported by Hailemariam and Kassamersha (1994) and 450 days by Gebeyehu and Hegde (2003) in Ethiopia. Longer CI's were reported by Shiferaw et al (2003) Negussie et al (1998) and 412 days by Yifat (2005) in Ethiopia and Ahmed et al (2007) (386 days) in Sudan.…”

Estimation of dominance genetic variances for reproductive traits and growth traits of calves in Japanese Black cattle

“…This might be because cattle are mainly kept on pastureland on the islands in Okinawa, and as a result the genetic difference of fertility might be clearer. The estimates of heritability for foreign beef breeds ranged from 0.01 to 0.125 for CI (Haile‐Mariam & Kassa‐Mersha 1994; Frazier et al . 1999; Gutiérrez et al .…”

Heritability of reproduetive traits in Asturiana de los Valles beef cattle breed

“…For age at first calving and 7 published estimates, calculated unweighted and weighted heritability means were 0.14 and 0.06. The low heritability estimated for these traits could be explained by: 1) little number of animal available in estimations, 2) the existence of a very important environmental influence on these traits, 3) the decrease of genetic variability Coming from the culling policy that affects essentially non-regular cows, 4) the need for better adjustment of fixed effects, 5) failure to consider the influence of some other reproduetive traits (gestation length or days open) on calving interval and age at first calving, and 6) the use of fitted modeis that can not explain sufficiently the population structure (HANSET et al, 1989;LOPEZ de TORRE and BRINKS, 1991;REGET and FAMULA, 1993;HAILE-MARIAM and KASSA-MERSHA, 1994 LOBO (1998) using an animal model in zebu cows estimated a heritability of 0.14±0.01 and 0.29±0.09 for calving interval and age at first calving respectively. Heritabilities reported for these authors are in close agreement with those estimated in the present paper.…”