|Sandelin, B - UNIV. ARKANSAS|
|Brown, JR., A. - UNIV. ARKANSAS|
|Johnson, Z - UNIV. ARKANSAS|
|Kellog, D - UNIV. ARKANSAS|
|Stelzleni, A - UNIV. ARKANSAS|
|Baublits, R - UNIV. ARKANSAS|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2001
Publication Date: February 1, 2002
Citation: Sandelin, B.A., Brown, A.H., Brown, M.A., Johnson, Z.B., Kellog, D.W., Stelzleni, A.M., Baublits, R.T. 2002. Maternal performance of four divergent biological types resulting from angus, brahman, and reciprocal cross cows grazing endophyte infected tall fescue or common bermudagrass. Journal of Animal Science. 80(Suppl. 2):11. Interpretive Summary: Differences in genetic potential for productivity in beef cattle are significantly influenced by differences in the genetic potential for mature weight, and the time that is required to reach mature weight (rate of maturing). However, little is known about how these factors interact with forage production system. Cooperative research conducted by the University of Arkansas and the USDA-ARS evaluated maternal performance of four divergent biological cow types of Angus, Brahman, and reciprocal cross cows grazing common bermudagrass (BG) or endophyte-infected tall fescue (E+). Biological types included large mature weight, early maturing cows; large mature weight, late maturing cows; small mature weight, late maturing cows; and small mature weight, early maturing cows. Maternal performance measures included calf birth weight, weaning weight, and weaning hip heights. Results from this research demonstrated that maternal performance of the different biological types depended on forage system on which the cows and calves were managed. This suggests the importance of properly matching genetic potential for mature weight and rate of maturing in cows to their production environment to insure optimal productivity.
Technical Abstract: Maternal performance of four divergent biological cow types of Angus, Brahman, and reciprocal cross cows grazing common bermudagrass (BG) or endophyte-infected tall fescue (E+) were evaluated over a 4-yr period. Growth curve parameters of mature BW and rate of maturing were estimated for 177 cows using the growth curve model as described by Brody (1945). Cows were assigned to one of four biological types: large late maturing (LL, mature BW > 583 kg, rate of maturing < 0.045% /mo), large early maturing (LE, mature BW > 583 kg, rate of maturing > 0.045% /mo), small late maturing (SL, mature BW < 583 kg, rate of maturing > 0.045% /mo), and small early maturing (SE, mature BW < 583 kg, rate of maturing > 0.045% /mo). Measurements on 374 calves over the 4-yr period included: birth weight, weaning weight, and weaning height. Distribution of calf measurements by biological type included: LL (n = 98), LE (n = 52), SL (n = 78), and SE (n = 146). The interaction of biological type x forage was significant (P < 0.05) for all traits with the exception of weight:height ratio. Calves from LE and SL dams were heavier at birth on E+ compared to BG (P<0.05), while birthweights of calves from LL and SE cows were similar on both forages. Calves from LL, SE, and SL cows were heavier at weaning on BG compared to E+ (P<0.01), while calves from LE cows had similar weaning weights on BG and E+. Calves from LL cows had larger hip heights on BG vs E+ (P<0.05), while calves from LE, SE, and SL cows were similar in hip height on both forages. These data suggest that biological type may have an effect on maternal performance and that the expression of this effect may depend on forage system.