Feeding behavior and ruminal pH of corn silage, barley grain, and corn dried distillers' grain offered in a total mixed ration or in a free-choice diet to beef cattle.

Seventy-nine continental crossbred beef heifers (524.4 ± 41.68 kg BW), 16 of which were ruminally cannulated, were used in a 53-d experiment with a generalized randomized block design to assess the effects of barley grain (BG), corn silage (CS), and corn distillers' grain (DG) offered in a free-choice diet on feeding behavior and ruminal fermentation. Treatments were total mixed ration (TMR) consisting of 85% BG, 10% CS, and 5% supplement or free-choice (i.e., self-selection) diets of BG and CS (BGCS), BG and corn dry DG (BGDG), or CS and corn DG (CSDG). Heifers were housed in groups of 9 or 10 in 8 pens and weighed 2 h before feed delivery at d 0, 21, 42, and 52 of the study. Pens were equipped with an electronic feed bunk monitoring system enabling feed intake and feeding behavior to be continuously monitored. Each of these pens was randomly allocated 2 cannulated heifers equipped with indwelling pH probes for continuous measurement of ruminal pH during wk 1, 2, 4, and 7. Blood and rumen contents were taken from cannulated heifers 2 h after feed delivery on d -3, 0, 7, 8, 42, and 49. Cattle fed either TMR or free-choice diets had similar (P > 0.10) ruminal fermentation, blood profile, and growth performance, with the exception of the CSDG diet, for which ruminal pH levels were consistently greater (P < 0.01) and performance was lower (P < 0.01). When DG was a component in free-choice diets, heifers reduced its inclusion in the diet (P < 0.05) over the experiment without affecting growth rate or ruminal fluid pH. Finishing feedlot cattle fed BG and CS separately selected a diet with a greater proportion of BG (85% DMI) compared to the TMR with no signs of acidosis. When cattle were given free-choice access to corn dry DG as an alternative to CS, they consumed levels up to 30% of their total daily DMI. Under the conditions of our experiment cattle can effectively self-select diets without increasing the risk of subclinical acidosis and still maintain similar levels of growth and feed efficiency compared with a TMR.

Relationship between feeding behavior and performance of feedlot steers fed barley-based diets.

The relationship between feeding behavior and performance of 274 feedlot cattle was evaluated using Charolais cross steers from 2 consecutive years averaging 293 ± 41 kg for yr 1 (n = 115) and 349 ± 41 for yr 2 (n = 159). Steers were blocked by BW and assigned to 3 (yr 1) or 4 (yr 2) feedlot pens equipped with a radio frequency identification system (GrowSafe Systems). Each pen contained 5 feeding stalls that allowed individual animal access to a feed tub suspended on load cells. The system recorded animal identification, duration, and frequency of feedings as well as the amount of feed consumed during each visit. Daily variation in DMI (DVI), calculated as the absolute difference in DMI from one day to the next, as well as eating rate were determined for each steer. Barley-based diets were delivered to meet steer ad libitum intake over the 213- and 181-d feeding periods for yr 1 and 2 of the study, respectively. The backgrounding periods included the first 85 and 56 d of yr 1 and 2, respectively, in which steers were fed a 14 to 30% concentrate diet, whereas the finishing periods included the last 116 and 101 d of feeding in yr 1 and 2, respectively, with the diet consisting of 77.9% concentrate. Steers were weighed individually every 14 d. To relate feeding behavior to performance, steers were grouped by ADG and G:F and categorized as high, average, or low (based on 1 SD greater than and less than the mean). In the backgrounding and finishing periods of both years of the study, steers classified as having high ADG exhibited greater (P < 0.001) DVI than steers classified as having average or low ADG. Total daily DMI was also greater (P < 0.001) for steers in the high ADG group than those in the low ADG group. Overall, those steers with the greatest G:F also tended (P = 0.15) to have greater DVI than average or low G:F steers. Compared with average or low G:F steers, DMI by high G:F steers in both years of the study was less during backgrounding, finishing, and overall (P = 0.02). Bunk visits and bunk attendance duration were less frequent and shorter (P ≤ 0.01) overall for high compared with low G:F steers. In this study, steers with more variable eating patterns exhibited greater ADG and tended to have greater G:F, a finding that is contrary to industry perception.

Feeding behavior and ruminal acidosis in beef cattle offered a total mixed ration or dietary components separately.

Eighty continental crossbred beef heifers (414.9 ± 37.9 kg of BW), 16 of which were ruminally cannulated, were used in a 52-d experiment with a generalized randomized block design, to assess if self-selection of dietary ingredients modulates ruminal pH and improves rumen function of feedlot finishing cattle. Treatments were total mixed ration [TMR; 85% barley grain (BG), 10% corn silage (CS), 5% supplement]; or free-choice (self-selection; FC) diets of barley grain and corn silage (BGCS), barley grain and wheat distillers grain (BGDG), or corn silage and wheat distillers grain (CSDG). Heifers were housed in groups of 10 in 8 pens equipped with the GrowSafe System (Airdrie, AB, Canada) enabling feed intake and feeding behavior to be continuously monitored. Two cannulated heifers were randomly assigned to each pen and equipped with indwelling pH probes for continuous measurement of ruminal pH during 4 periods (d 1 to 4, d 7 to 14, d 21 to 28, and d 42 to 49). Rumen fluid samples were collected from cannulated heifers on d 7 and 42 before feed delivery, and on d 4 and 49 at 2 h post-feed delivery for determination of VFA. Heifers fed the TMR had shorter (P = 0.01) and smaller (P = 0.03) meals than those fed the FC diets. Cattle fed BGCS and BGDG increased (P < 0.01) intake of BG over time by up to 80 and 70%, respectively. Increased consumption of BG arose from an increase (P < 0.01) in eating rate over the same (P > 0.10) feeding time, which was accompanied by an increase (P < 0.05) in eating rate but a decrease (P < 0.05) in feeding time of either CS or DG. Even with increased BG consumption, ruminal pH and VFA profiles were not different (P > 0.10) among FC diets or compared with the TMR. Cattle fed FC CSDG consumed DG at 60% of dietary DM over the trial, resulting in greater (P < 0.05) mean ruminal pH and acetate-to-propionate ratio and less (P < 0.05) area under the curve than those given the other FC diets or the TMR. Finishing feedlot cattle fed FC diets containing BG self-regulate intake of diets that have a similar composition, intake level, and ruminal fermentation profile to those fed a TMR.