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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #99589
Title: NEW AGE-MONTH CORRECTION FACTORS FOR MILK PRODUCTION OF HOLSTEIN CATTLE IN MEXICO

Author
item VALENCIA-POSADAS, M. - FMVZ-UNAM, MEXICO
item RUIZ, F. - CENIFMA-INIFAP, MEXICO
item MONTALDO, H. - ICA-UGTO, MEXICO
item TREJO, B. - CIMAT-AGS, MEXICO
item KEOWN, JEFFREY - UNIV. OF NEBRASKA-LINCOLN
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Correction factors (CF) for milk production used nationally in Mexico were estimated 23 years ago using a sire model with few records and assuming a value of heritability. Since those CF were adopted, many changes of management practices have occurred. New CF are needed to reduce possible biases in genetic evaluations. The objectives of this study were to estimate age-month CF for milk production by region and to compare currently used CF and those obtained in this study. Records were provided from Mexican Holstein Association. Only 305d milk yields were considered. Records were classified by three regions. Numbers of records including all lactations were 12,062, 42,059 and 17,990 for the North (N), Central (C) and South (S) regions, respectively. The base group included cows calving in January between 70-73 months of age. Variance components and age-month solutions were obtained by REML using an animal model. Averages of milk production and heritability estimates were 8,446, 7,841 and 7,176 kg and 0.26, 0.24 and 0.18 for N, C and S regions, respectively. Deviations of solutions from base groups were smoothed through polynomial regression and then used to obtain the CF. Differences (DIF) between new CF for each region and current national CF were obtained. Analysis of variance was used to test equality between them. Correlations between CF's also were estimated. Correlations between current CF and the new CF by region were only 0.89 to 0.92. The new CF were different because group of age and month effects were significant for DIF. The new CF could be less biased than current CF because an animal model was used with most recent records and with specific CF for each region.