Full text in pdf format

Age-month factors - mature equivalent factors for three yield traits for non-registered and registered cattle

Marcus Cordeiro Durães^I; Jeffrey F. Keown^II

^IEMBRAPA/CNPGL-CNPq, 36155 Coronel Pacheco, MG, Brasil
^IIDepartment of Animal Science, University of Nebraska, Lincoln 68583-9898, USA. Send correspondence to J.F.K.

ABSTRACT

Age-month adjustment factors for registered and non-registered cows were estimated for milk, fat and protein yields. Records used i analysis considered 419,860 lactation records of Holsein cows freshening from 1983 to 1985 in nine states of the Mid-West region of the United States: Arkansas, Illinois, Iowa, Kansas, Missouri, Nebraska, North Dakota, Oklahoma and South Dakota. The mixed model used to describe the data contained fixed effects due to an overall mean, age-month of calving for non-registered and registered cows, the herd-year; and as random effects, cow and error terms. There were 30 age groups by 12 months of freshening for a total of 720 age-month estimates for each of the three traits. The ratio of (s²e/ (s ²c = 13/12 based on a repeatability of .48 for milk yield was used. Results showed a definitive age by month interaction. Age is more important for younger cows while month effects assumed more importance for mature cows. Multiplicative age-month adjustment factors were developed and are presented along with plots of the age-month factors for milk, fat and protein yield. Factors differed for the three yield traits. Milk and fat factors were larger than the corresponding factors for protein. There was a general trend for factors from non-registered to be larger than those from registered cows for same age and months of calving.

Keywords: Age-month factors; Cattle.

REFERENCES

Cooper, J.B. and Hargrove, G.L. (1982). Age and month of calving adjustment of Holstein protein, milk, and fat lactation yields. J. Dairy Sci. 65: 1673.

Keown, J.F. and Everett, R.W. (1985). Age-month adjustment factors for milk, fat, and protein yields in Holstein cattle. J. Dairy Sci. 68: 2664.

McDaniel, B.T. (1973). Merits and problems of adjusting to other than mature age. J. Dairy Sci. 56: 959. Miller, P.D. (1973). A recent study of age adjustment. J. Dairy Sci. 56: 952.

Miller, P.D. and Henderson, C.R. (1968). Seasonal age-correction factors by maximum likelihood. J. Dairy Sci. 51: 958.

Miller, P.D., Lentz, W.E. and Henderson, C.R. (1970). Joint influence of month and age at calving on milk yield of Holstein cows in the northeastern United States. J. Dairy Sci. 53: 351.

Norman, H.D., Miller, P.D., McDaniel, B.T., Dickinson, F.N. and Henderson, C.R. (1974). USDA-DHIA factors for standardizing 305-days lactation records for age and month of calving. ARS-NE-40. Washington, Agriculture Research Service. U.S. Department of Agriculture.

Norman, H.D. and Powell, R.L. (1983). Use of grade animals in United States Department of Agriculture programs. J. Dairy Sci. 66: 1567.

Powell, R.L. and Norman, H.D. (1986). Genetic and environmental differences between registered and grade Holstein cows. J. Dairy Sci. 69: 2897.

Wunder, W.W. and McGilliard, L.D. (1967). Seasons of calving and their interactions with age for lactational milk yield. J. Dairy Sci. 50: 986.