Rate of Maturing and Proportion of Mature Body Weight at Puberty of Crossbred Cows

Authors: Freetly, Harvey; Kuehn, Larry

Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/9/2009
Publication Date: 7/12/2009
Citation: Freetly, H.C., Kuehn, L.A. 2009. Rate of Maturing and Proportion of Mature Body Weight at Puberty of Crossbred Cows [abstract]. Journal of Animal Science 87 (E-Supplement 2):498.

Interpretive Summary:

Technical Abstract: Cows born (1999 – 2000) resulting from AI breeding Hereford (n = 58), Angus (n = 61), Red Angus (n = 70), Simmental (n = 74), Limousin (n = 80), Charolais (n = 74), or Gelbvieh (n = 78) bulls to Angus (A; n = 69), Hereford (H; n = 173), or MARC III composite (M; n = 253) cows were weighed 6 times as calves and then twice a year as cows through 7 years of age. Body condition scores (BCS; 1 through 9 scale) and BW were collected at the beginning of breeding and then again in 4 mo. Cow BW was standardized to a BCS of 6 by allowing ± 45 kg BW/BCS different than 6. Individual growth curves of BW on age (weeks) were fit with the nonlinear function f(age) = A – Be k×age using the Gauss-Newton iterations to minimize error sum-of-squares. Proportion of mature weight reached at puberty (n = 459) was solved for age at puberty with f(age) = 1 – (B/A)e k×age. Sire and dam breed effects were tested with a model including sire breed (S), dam breed (D), birth year (Y), S × D, S × Y, and D × Y. Sire nested within S, was treated as a random effect. There was no S × D interaction for k (P = 0.49), B/A (P = 0.21), and maturity at puberty (P = 0.61). Main effects for S differed for k (P = 0.01), B/A (P = 0.04), and tended to differ for maturity at puberty (P = 0.09). Sire breed means and standard errors _______________________________________________________________________________________________ Breed k B/A Maturity at puberty _______________________________________________________________________________________________ Hereford -0.01244 ± 0.00034 0.9135 ± 0.0035 0.508 ± 0.011 Angus -0.01382 ± 0.00029 0.9123 ± 0.0030 0.529 ± 0.007 Red Angus -0.01397 ± 0.00030 0.9075 ± 0.0031 0.532 ± 0.008 Simmental -0.01396 ± 0.00030 0.9099 ± 0.0031 0.532 ± 0.008 Limousin -0.01362 ± 0.00027 0.9178 ± 0.0027 0.545 ± 0.007 Charolais -0.01393 ± 0.00027 0.9200 ± 0.0027 0.538 ± 0.007 Gelbvieh -0.01390 ± 0.00027 0.9132 ± 0.0028 0.521 ± 0.007 _______________________________________________________________________________________________ Main effects for D differed for k (P < 0.001; H -0.01308 ± 0.00024, A -0.01426 ± 0.00015, M -0.01365 ± 0.00013), and for maturity at puberty (P < 0.001; H 0.523 ± 0.007, A 0.542 ± 0.004, M 0.523 ± 0.003), but not for B/A (P = 0.88). There were S × Y (P = 0.005), and D × Y (P = 0.02) interactions for k, and S × Y (P = 0.006), and D × Y(P = 0.02) interactions for B/A.