|RILEY, DAVID - Texas A&M Agrilife|
|Chase, Chadwick - Chad|
Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2015
Publication Date: 9/20/2015
Citation: Riley, D., Burke, J.M., Chase, C.C., Coleman, S.W. 2015. Genetic effects for reproductive performance of straightbred and crossbred Romosinuano and Angus cows in a temperate zone. Livestock Science. 180:22-26.
Interpretive Summary: Reproduction in cows in the southeastern U.S. can be hampered by environmental factors such as the dominant forage, tall fescue, and heat stress, which costs the beef industry millions of dollars annually. Use of a tropically adapted Bos taurus beef breed, Romosinuano, that is more thermo-tolerant may allow for a tolerance to fescue toxins and improve production parameters on Arkansas pastures. Scientists from Texas A&M, USDA, ARS Booneville, AR, El Reno, OK and Clay Center, NE determined that the Romosinuano might be considered for inclusion in a breeding program due to direct favorable effects on calving and weaning rate, lower death losses and better stayability compared with Angus, even considering the negative effects of tall fescue. These results provide information on potential genetics for cow-calf production on endophyte-infected tall fescue, information that is important to producers, extension agents, and scientists.
Technical Abstract: The objectives of this work were to: 1) estimate heterosis and breed direct effects for cow reproduction traits of Romosinuano, Angus, and F1 cows in a temperate climate, and 2) assess the effects of the type of forage grazed (bermudagrass, endophyte-infected and endophyte-free tall fescue) during the breeding season on those traits and on the estimates of heterosis and breed effects. Calving and weaning rate (n = 666 records) were evaluated for 145 cows of the 4 breed types (sire breed-dam breed interactions) from 2005 through 2012. Most cows calved as 2-yr-olds in Florida and were transported pregnant to Arkansas in November or December. Some Angus females were purchased in Arkansas. Calving interval (n = 400) and day of conception within breeding season (n = 547) were recorded. Mixed models included combinations of fixed effects: year of record or cow age within year of record, breed type parameterized as main and interaction effects of sire breed and dam breed of cows with records. Additive genetic effects were included as a random component. The sire breed-dam breed interaction was characterized by lower (P < 0.005) Angus calving and weaning rates (0.75 ± 0.03, 0.65 ± 0.04, respectively) than all other combinations of sire and dam breed, which ranged from 0.88 ± 0.02 (Romosinuano) to 0.92 ± 0.04 (Romosinuano-sired F1 cows) for calving rate and ranged from 0.81 ± 0.03 (F1 cows sired by Angus) to 0.82 ± 0.03 (Romosinuano-sired F1 cows) for weaning rate. Romosinuano cows conceived later (P < 0.02) in the breeding season (25.2 ± 2.3 d) than cows of the other sire breed-dam breed combinations (range from 16.9 ± 3.1 to 17.3 ± 1.8 d). No parameterization of breed type was detected (P > 0.65) in analyses of calving interval. In subsequent analyses, calving and weaning rates were highest (P < 0.05) for cows grazing bermudagrass during the breeding season (0.98 ± 0.02, 0.93 ± 0.03), and lowest (P = 0.002) for cows grazing endophyte-infected tall fescue (0.85 ± 0.03, 0.78 ± 0.04); cows grazing endophyte-free tall fescue were intermediate (0.94 ± 0.02, 0.88 ± 0.03). No interaction of forage type with sire or dam breed was detected (P > 0.24). Forage type was not influential in analyses of calving interval or conception day within breeding season (P > 0.18). Estimates of heterosis were 0.09 ± 0.03, 0.11 ± 0.04, and –3.7 ± 2.0 d (P < 0.05) for calving and weaning rate, and conception day within breeding season, respectively. Romosinuano direct effects in cows for these traits were large (P < 0.003) and favorable for calving and weaning rate (0.14 ± 0.05%, 0.2 ± 0.05%), but unfavorable for conception day within breeding season (8.7 ± 2.9 d; P < 0.05). These genetic effects were not detected in evaluation of these 2 breeds as a part of a larger study in a subtropical climate. Cow breed type (sire breed-dam breed combinations) proportions of calf losses and cow deaths and culls differed from expectation (P < 0.001); Angus cows had the greatest proportion of calf loss (0.33) and cows that died or were culled (0.8). These results suggest that this tropically-adapted Criollo breed , Romosinuano, may merit consideration for inclusion in breeding programs in temperate climates, even when grazing harsh forage containing antiquality factors.