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Previous research has demonstrated that cattle with divergent RFI have distinctive differences in feeding behavior patterns, and carcass fat content. Objectives of this study were to develop and validate predictive equations for RFI utilizing feeding behavior and carcass ultrasound traits as independent variables. Three consecutive- year trials were conducted using Angus crossbred steers (N = 508) with an initial age of 293 ± 18 d and BW of 309 ± 56 kg. For each study, steers were blocked by BW and randomly assigned to 1 of 2 pens equipped with GrowSafe feed bunks. DMI and feeding behavior (FB) traits were measured daily for 70 d while fed a grainbased feedlot diet. Initial and final carcass ultrasound measurements (intra-muscular fat, backfat (BF) depth, rib eye area) were collected on days 0 and 70, and BW was measured at 14-d intervals. Fourteen FB traits were evaluated including frequency and duration of bunk visit (BV) and meal events, head-down duration (HDD), time to bunk, and the corresponding day-to-day variances (SD) of these traits. Additionally, HDD per meal event and BV per meal were included. RFI (0.00 ± 0.78 kg) was calculated within trial by linear regression of DMI (10.1 ± 1.1) on ADG (1.71 ± 0.27 kg/d) and mid-test BW0.75. Separate RFI prediction equations were developed using partial least squares procedures with FB and FB plus ultrasound (FB+) traits included as independent variables. Coefficients of determination for calibration (R2 c) were 0.42 and 0.46 for FB and the FB+ models respectively. For the FB+ model, traits with variable of importance (VIP) scores >1 included HDD, BV duration, daily HDD SD, HDD per meal, daily BV duration SD, BV frequency, and gain in BF. Two validation methods (cross and test-set validation) were used to evaluate the accuracies of the RFI predictive equations. The accuracies of cross validation (R2 cv) were 0.41 and 0.46 for the FB and FB+ models, respectively. For testset validation, pen 1 was used for calibration and pen 2 for validation, and the reciprocal. Accuracies for test-set validation (R2 v) were 0.32 and 0.39 for FB models and 0.38 and 0.45 for the FB+ models. These results indicate that phenotypic RFI can be predicted based on feeding behavior traits with moderate accuracy. More studies are warranted utilizing larger databases to develop more robust equations for the accurate prediction of individual- animal RFI. [ABSTRACT FROM AUTHOR]

Objectives of this experiment were to determine if statistical process control (SPC) procedures coupled with remote collection of rumen temperature (RT) and feeding behavior (FB) patterns could accurately differentiate between animals experimentally inoculated with Mannheimia haemolytica (MH) or phosphate buffer solution (PBSo) and to determine if live yeast (LY) supplementation would mitigate responses to MH challenge. Thirty-six crossbred steers (352 ± 23 kg BW) seronegative for MH were allocated within a 2 × 2 factorial treatment arrangement: Factor1 = roughage-based diet with or without LY (Saccharomyces cerevisiae boulardii I-1079 at 1 × 1010 cfu/d; Lallemand) and Factor2 = bronchoselective endoscopic inoculation with MH or PBSo. Electronic feed bunks (GrowSafe) were used to measure DMI and FB traits, and ruminal thermo-boluses (Medria) used to measure RT at 5-min intervals. Data were collected 28 d prior to and following inoculation. Steers inoculated with MH exhibited elevated levels of haptoglobin, white blood cells, and neutrophils (P < 0.02), indicating that the MH challenge effectively stimulated immunologic responses. However, only 1 animal displayed overt clinical signs of disease. Shewhart charts (SPC procedure) were used in this analysis, and sensitivity, specificity, and accuracy were computed to evaluate univariate and multivariate models based on principal components analysis (PCA). Of the FB traits monitored, time to bunk had the highest model sensitivity (94%) and accuracy (94%), with model accuracies for head-down duration and bunk visit duration and frequency being less (80, 79, and 56%, respectively). Model accuracy for DMI was intermediate at 85%. To address the diurnal nature of RT, data were averaged over 6-h intervals, and quarterly RT models were evaluated separately. Model accuracy for the first quarter RT was more accurate (84%) than the other quarterly RT periods (82, 76, and 79%). Two PCA models were constructed separately using all FB and RT traits. Model sensitivity and accuracy were relatively higher for the FB PCA model (94 and 95%) than for the RT PCA model (78 and 85%), with both PCA models performing slightly better than the best respective univariate trait model. The performance of a combined PCA model (all traits) was intermediate in accuracy at 91%. In this study, LY supplementation did not influence the sensitivity or accuracy of the univariate or PCA models. These results indicate that Shewhart procedures can effectively identify deviations in FB and RT patterns for the purpose of subclinical bovine respiratory disease detection. Furthermore, the PCA models were numerically more accurate than univariate traits and should be more robust in application due to their multivariate nature. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of Levucell SC (Saccharomyces cerevisiae CNCM l-1077) supplementation on growth efficiency, ruminal temperature and feeding behavior traits in yearling steers. Crossbred beef steers (N = 48), blocked by source and initial BW (441 ± 30.8 kg), were used in a completely randomized block design. Steers were assigned to 1 of 2 treatments (2 pens per treatment); Levucell SC (10 x 109 cfu/hd/d) or control (carrier only) in a high-grain diet (ME = 2.84 Mcal/kg DM). This trial was conducted for 70 d in pens equipped with a GrowSafe feed intake monitoring system during the summer months in McGregor, TX. There were no statistical differences detected among treatments in DMI, ADG, feed conversion ratio or ruminal temperature. However, supplementation with live yeast tended to reduce bunk visit (BV) frequency (-9%, P = 0.07) and increase BV duration (+22%, P < 0.05) and head down duration (+41%, P < 0.05), which resulted in an 18% reduction (P < 0.05) in BV eating rate. Meal criterion was 47% greater (P < 0.01) for animals fed live yeast, which resulted in reduced meal frequency (-13%, P = 0.07) and increased meal duration (+13%, P < 0.05) and average meal length (+27%, P < 0.05). Steers supplemented with live yeast spent more time feeding, although similar DMI was consumed compared to control steers, resulting in a reduction of meal eating rate (-10%, P < 0.05). Additionally steers supplemented with live yeast began feeding 25 min earlier (P < 0.001) than control steers following feed truck delivery. Steers supplemented with live yeast spent more time eating, ate less often and at a reduced rate compared to control steers. Live yeast supplementation could potentially aid in mitigating metabolic stress in steers fed high-grain diets by altering their feeding behavior patterns in a manner that is more favorable for microbial fermentation. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the effects of Levucell SC (Saccharomyces cerevisiae CNCM l-1077) supplementation on growth efficiency, ruminal temperature and feeding behavior traits in yearling steers. Crossbred beef steers (N = 48), blocked by source and initial BW (441 ± 30.8 kg), were used in a completely randomized block design. Steers were assigned to 1 of 2 treatments (2 pens per treatment); Levucell SC (10 × 109 cfu/hd/d) or control (carrier only) in a high-grain diet (ME = 2.84 Mcal/kg DM). This trial was conducted for 70 d in pens equipped with a GrowSafe feed intake monitoring system during the summer months in McGregor, TX. There were no statistical differences detected among treatments in DMI, ADG, feed conversion ratio or ruminal temperature. However, supplementation with live yeast tended to reduce bunk visit (BV) frequency (-9%, P = 0.07) and increase BV duration (+22%, P < 0.05) and head down duration (+41%, P < 0.05), which resulted in an 18% reduction (P < 0.05) in BV eating rate. Meal criterion was 47% greater (P < 0.01) for animals fed live yeast, which resulted in reduced meal frequency (-13%, P = 0.07) and increased meal duration (+13%, P < 0.05) and average meal length (+27%, P < 0.05). Steers supplemented with live yeast spent more time feeding, although similar DMI was consumed compared to control steers, resulting in a reduction of meal eating rate (-10%, P < 0.05). Additionally steers supplemented with live yeast began feeding 25 min earlier (P < 0.001) than control steers following feed truck delivery. Steers supplemented with live yeast spent more time eating, ate less often and at a reduced rate compared to control steers. Live yeast supplementation could potentially aid in mitigating metabolic stress in steers fed high-grain diets by altering their feeding behavior patterns in a manner that is more favorable for microbial fermentation. [ABSTRACT FROM AUTHOR]