|Tait Jr, Richard|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/27/2017
Publication Date: 7/1/2017
Citation: Foote, A.P., Tait Jr, R.G., Freetly, H.C. 2017. Changes in feed intake, growth, feed efficiency, and body composition of beef cattle fed forage then concentrate diets [abstract]. Journal of Animal Science Supplement. 95(Supplement 4):64.
Technical Abstract: The objective of this experiment was to determine changes in production traits and body composition of beef steers and heifers when fed a forage-based ration followed by a concentrate-based ration. Cattle were progeny of composite breed cows bred to Charolais, Simmental, and Red Angus bulls. Approximately 4 weeks after weaning, steers (n=71) and heifers (n=79) were placed on a ration containing (DM basis) 69.8% corn silage, 30% alfalfa hay, and 0.2% salt. Feed intake was measured for 84 d and BW were measured at 7 time points to calculate ADG using a quadratic regression of BW on time. Cattle were then transitioned to a concentrate-based finishing ration containing (DM basis) 67.8% dry-rolled corn, 20% wet distillers grains with solubles, 8% alfalfa hay, and 4.2% vitamin/mineral supplement. Data were analyzed using a mixed model (SAS) with sex, sire breed, dam breed, period (forage vs. concentrate), and sex × period as fixed factors, sire as a random variable, and period treated as repeated variable. This allowed the calculation of correlations among residuals from within periods. Cattle consumed approximately 30% more DM on the concentrate-ration compared to the forage-ration (P<0.01) and steers consumed about 10% more DM than heifers (P<0.01). The residual correlation between forage and concentrate DMI was r = 0.51, indicating a positive association of DMI between the 2 rations. Regardless of sex, ADG was greater on the concentrate ration (0.9 vs. 2.1 kg/d; P<0.01); however, the residual correlation was r = -0.09. The residual correlation coefficient for G:F was r = -0.17 and RFI was r = 0.38. Increase in LM area was greater for heifers (P<0.01) and was greater during the concentrate-ration feeding period (P<0.01) and the residual correlation was r = -0.35. There was a sex × feeding period interaction for back fat change (P<0.01), indicating that steers had a greater increase in fat thickness on the forage ration while heifers had a greater fat thickness increase on the concentrate ration. The residual correlation for back fat gain was r = -0.27. There was a sex × feeding period interaction (P<0.01) for change in intramuscular fat (IMF), with steers gaining more IMF on the forage-ration (0.50 vs. 0.33%), but heifers gaining more IMF on the concentrate ration (1.64 vs. 0.65%). Data indicate there is correlation across different diets for feed intake and composition of growth traits in beef cattle.