Effect of Age at First Calving on Some Productive and Longevity Traits in Iranian Holsteins of the Isfahan Province

• Published in: Journal of dairy science Vol. 87; no. 7; pp. 2130 - 2135
• Main Authors: Nilforooshan, M.A., Edriss, M.A.
• Format: Journal Article
• Language: English
• Published: Savoy, IL Elsevier Inc 01.07.2004; Am Dairy Sci Assoc; American Dairy Science Association
• Subjects: age at first calving; Aging; animal age; Animal productions; Animals; Biological and medical sciences; Breeding; breeding value; calving; Cattle - physiology; dairy cows; early calving; Female; Food industries; Fundamental and applied biological sciences. Psychology; heritability; Holstein; Iran; Lactation; lactation number; lifetime; Lipids - analysis; Longevity; Milk - chemistry; Milk and cheese industries. Ice creams; milk fat percentage; milk fat yield; milk yield; milk yield trait; Phenotype; phenotypic correlation; Pregnancy; production costs; productive life; Reproduction; sire evaluation; Terrestrial animal productions; Vertebrates; Iran; lifetime; milk yield trait; age at first calving; productive life; life- time; Dairy industry; Calving; Longevity; Age
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.S0022-0302(04)70032-6

Production and pedigree data of Iranian Holsteins were collected from 1991 to the end of 2001 on 45 herds in Isfahan province. Data on culled cows (birth and culling dates) were used to estimate the effect of age at first calving on total lifetime and productive life; and the effect of age at first calving on first-lactation yields was estimated from corrected (2× 305d) first-lactation records of 12,082 dairy heifers that calved between 1995 and 2001. The estimate of heritability of age at first calving obtained in this study was 0.086. This low heritability indicates the importance of using available information on relatives for selection on this trait. Age at first calving significantly affected all the traits investigated, including: milk yield, fat yield, fat percentage, lifetime, and productive life. Results indicated a positive effect of reducing age at first calving on milk yield and productive life, although reducing age at first calving to 21 mo of age had a negative effect on yields of milk and milk fat. Lifetime did not show a similar trend with age at first calving. However, a slight positive phenotypic correlation (0.052) was detected between age at first calving and lifetime. We conclude that due to negative effects of age at first calving on productive life and because of optimum age at first calving for milk yield was 24 mo in this study, the reduction of age at first calving to 24 mo of age could be an effective management practice.