Article (Scientific journals)
Optimal age at first calving for improved milk yield and lengh of productive life in Tunisian Holstein cows
Ben Gara, Abderrahmen; Bouraoui, Rachid; Rekik, Boulbaba et al.
2009In American-Eurasian Journal of Agronomy, 2 (3), p. 162-167
Peer reviewed
 

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Keywords :
true herd life; heritability; milk yield; age at first calving
Abstract :
[en] The effects of age at first calving on milk production and true herd life were studied in Tunisian Holstein cows. There were 33,407 first lactation records of cows born between 1987 and 2001 from 166 herds. Firstly, age at first calving was analyzed using an animal model that included herd, calving year, herd-calving year interaction, calving month, and age of dam as fixed effects and the random additive genetic effect. Secondly, differences in first lactation and productive life milk yields and in true herd life were explained by age at first calving in addition to herd, year at first calving, herd-year at first calving interaction and month at first calving. A cow produced on the average 5669.8 kg milk (SD=1812 kg) during a 305-d first lactation period. The lifetime production of a cow was was 19,496.3 kg (SD=12,192 kg) during 3.3 lactations (SD=1.8 lactations). Coefficients of determination ranged from 14% for true herd life to 64% for first lactation milk yield. The mean of true herd life was 38.6 months (SD=24 months) and the mean age at first calving was 28.7 months (SD=3.4 months). Posterior mean of heritability of the age at first calving derived by a Markov Chain Monte Carlo Bayesien method via a Gibbs sampling algorithm was 0.08. The reduction of age at first calving to around 24 months may result in improved 305-d and lifetime yields and a longer herd life in Tunisian Holsteins.
Disciplines :
Food science
Genetics & genetic processes
Animal production & animal husbandry
Author, co-author :
Ben Gara, Abderrahmen;  Ecole Supérieure d'Agriculture de Mateur, Tunisie > Productions animales
Bouraoui, Rachid;  Ecole Supérieure d'Agriculture de Mateur, Tunisie > Productions animales
Rekik, Boulbaba;  Ecole Supérieure d'Agriculture de Mateur, Tunisie > Productions animales
Hammami, Hedi ;  Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech
Rouissi, Hamadi;  Ecole Supérieure d'Agriculture de Mateur, Tunisie > Productions animales
Language :
English
Title :
Optimal age at first calving for improved milk yield and lengh of productive life in Tunisian Holstein cows
Publication date :
2009
Journal title :
American-Eurasian Journal of Agronomy
ISSN :
1995-896X
eISSN :
2221-3414
Publisher :
International Digital Organization for Scientific Information (IDOSI), Dubai, United Arab Emirates
Volume :
2
Issue :
3
Pages :
162-167
Peer reviewed :
Peer reviewed
Available on ORBi :
since 23 October 2009

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