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This experiment compared performance, health, and physiological responses of weaned cattle receiving Bacillus subtilis derivative in a 90-d grazing period. Recently weaned Angus-influenced steers (n = 120) were obtained from an auction yard on d -1 and transported 150 km to research facility. Immediately after arrival on d -1, shrunk body weight (BW) was recorded and steers were grouped with access to native forage and water. On d 0, an additional body weight was recorded and combined with d -1 values to represent initial body weight (BW; 236 ± 2 kg). Steers were ranked according to initial BW and allocated to 1 of 12 pastures (4-ha pastures; 10 steers/pasture). Pastures were randomly assigned to receive daily supplementation with dried distillers grains at 1% of BW with either: 1) Bacillus subtilis ingredient (BOV; 2 g/steer daily of Bovacillus; Chr Hansen A/S, Horsholm, Denmark), or 2) no additive (CON). Cattle received treatments for the duration of the experiment (d 0 to d 90) while housed in pastures containing stockpiled native forage, primarily Cynodon dactylon and Paspalum dilatatum, as well as free-choice access to water and a commercial mineral + vitamin mix not including ionophores. Bovine respiratory disease (BRD) signs were assessed daily throughout the experimental period. Steer unshrunk BW was recorded on d 14, 28, 56, and 90 and shrunk BW recorded on d 91 added 8% shrink as final BW. Blood samples and fecal swabs were collected from all steers on d 0, 14, 28, 56, and 90. Average daily gain (ADG) was increased in BOV groups compared with CON (0.858 and 0.760 kg/d, respectively) from d 56 to d 90 (P = 0.09) although this BW gain was not sufficient to impact final BW. Steer BW did not differ between treatments for all days (P = 0.43). Incidence of BRD was within the expected range for high-risk stocker cattle, although the number of sick animals was not reduced due to BOV supplementation (P = 1.00). Steers not completing the trial due to health-related complications tended to be increased in CON vs. BOV (P = 0.08). Differences in percentage of steers not completing the experiment, in conjunction with treatment effects for ADG in the final third of the experiment, increased the production total BW per BOV pasture by 43% (790 vs. 550 kg BW change; P = 0.02). Bacillus subtilis supplementation was effective in increasing production BWt during a 90-d grazing period despite no observed difference in BRD incidence. [ABSTRACT FROM AUTHOR]

This experiment evaluated growth and reproductive development of beef heifers reared at a high stocking density and provided with access to an exercise area. The experiment was replicated over 2 yr, with a total of 180 Angus x Brahman heifers. Each year, 90 heifers were ranked by age (264 ± 1 d) and body weight (BW; 200 ± 2 kg) on d 0, and assigned to a) 1 of 6 drylot pens (10 x 14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m²/heifer (DENS), or b) 1 of 3 paddocks (2-ha paddocks; 10 heifers/paddock) resulting in a stocking density of 2,000 m²/heifer (CON). On d 15, 3 DENS pens were randomly selected and given access to an exercise area (DENS-EX) for 1 h three times weekly. Negligible forage was available for CON heifers, whereas all heifers received the same limit fed diet which averaged 13 kg/heifer daily of a corn-based diet. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on d -3 and 225 for BW gain calculation. Heifer temperament (chute score, exit velocity, and temperament score) were evaluated on d 0 and 225. Heifers were also fitted on d 0 with a pedometer behind their shoulder and an ear tag (CowManager, Select Sires, Plain City, OH) to record behavioral responses. Each week, pedometer results were recorded, and blood samples were collected for puberty evaluation via plasma progesterone. Heifers from CON had more (P < 0.05) steps per week compared with DENS and DENS-EX (23,973, 6,706, and 12,354 steps/week, respectively; SEM = 1,247), and DENS-EX heifers had more (P < 0.05) steps per week compared with DENS. Heifers from CON spent more (P < 0.05) time ruminating and eating compared with DENS and DENS-EX. No treatment effects (P > 0.91) were detected for heifer BW gain (0.820, 0.815, and 0.824 kg/d for CON, DENS, and DENS-EX, respectively; SEM = 0.016). Heifers from DENS had greater (P ≤ 0.05) exit velocity and temperament score on d 225 compared with DENS-EX and CON. Heifers from DENS experienced delayed puberty attainment (treatment x day; P < 0.01) compared with DENS-EX and CON. A greater (P ≤ 0.05) proportion of CON heifers were pubertal by day 105 compared with DENS and DENS-EX (30.0, 11.6, and 15.0%, respectively; SEM = 6.5), whereas a greater (P < 0.05) proportion of CON and DENS-EX heifers were pubertal by d 154 compared with DENS (61.7, 66.7, and 43.3%, respectively; SEM = 6.5). Results from this experiment demonstrate that providing heifers with an exercise area alleviated the negative effects associated with high stocking density on their reproductive development. This work is supported by the USDA-NIFA AFRI program (#2021-67015-34083). [ABSTRACT FROM AUTHOR]

This experiment evaluated the physiological and reproductive responses of beef heifers reared at a high stocking density and provided with access to an exercise area. Ninety Angus × Brahman heifers were ranked by age (257 ± 2 days), body weight (BW; 216 ± 2 kg), and temperament score on day 0 and assigned to a) 1 of 6 drylot pens (10x14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (DENS), or b) 1 of 3 paddocks (2-ha paddocks; 10 heifers/paddock) resulting in a stocking density of 2,000 m2/heifer (CON). On day 15, 3 DENS pens were randomly selected and given access to an exercise area (DENS-EX) for 1 hour three times weekly. Negligible forage was available for CON heifers, whereas all heifers received the same limit fed diet which averaged 13 kg/heifer daily of a corn-based diet. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 225 for average daily gain calculation. On day 0, heifers were fitted with a pedometer behind their shoulder and an ear tag (CowManager, Select Sires, Plain City, OH) to record behavioral responses. Each week, pedometer results were recorded, and blood samples were collected for puberty evaluation via plasma progesterone. Heifers from CON had more (P < 0.05) steps per week compared with DENS and DENS-EX, and DENS-EX heifers had more (P < 0.05) steps per week compared with DENS. Heifers from CON spent more (P < 0.05) time ruminating and eating compared with DENS and DENS-EX. No treatment effects (P = 0.12) were detected for heifer BW gain or temperament variables. Heifers from DENS experienced delayed puberty attainment given a greater (P < 0.05) proportion of CON heifers were pubertal by day 98 compared with DENS and DENS-EX, whereas a greater (P < 0.05) proportion of DENS-EX heifers were pubertal by day 154 compared with DENS heifers (treatment × day interaction, P < 0.01). Collectively, results from this experiment demonstrate that providing heifers reared at a high stocking density access to an exercise area does not result in similar reproductive responses as those reared on pasture at a low stocking density. This work is supported by the USDA National Institute of Food and Agriculture (#2021-67015-34083). [ABSTRACT FROM AUTHOR]

There is a need to understand the feeding behavior ontogeny of newly received high-risk steers. Understanding how calves learn to eat out of a bunk will facilitate the implementation of management practices that expedite this process and allow animal managers to exploit this information to monitor individual animal health. To address this knowledge gap, the feeding behavior of high-risk steers that were received for backgrounding was quantified and characterized using electronic feedbunks in this context. To create this paradigm, crossbred steers (n = 20) were purchased in two groups (Group: n = 64 steers; Group 2: n = 56 steers) from a local auction market, transported 800 km to the Prairie Research Unit in Prairie, MS, and immediately weighed (shrunk body weight, BW). Steers were purchased according to research unit space availability. Therefore, purchases occurred 133 days apart. The subsequent day, steers were ranked by shrunk BW (227 ±.3 kg) and allocated to 1 of 8 drylot pens (n = 8 steers/pen) with two GrowSafe automated feeding systems per pen. Steers were fed a total mixed ration ad libitum for a 28-day period and steer BW was recorded on d 0, 2, 6, 10, 13, 21 and 28. Daily feeding behavior [e.g., meal duration (sec), intake (g/d), meal frequency (count/d), bunk visit frequency (count/d), head down duration (sec), maximum non-feeding interval (NFI, s), ratio of head down duration to bunk visit duration)] were calculated using Meal Criterion Calculation Software. The impact of time on feeding behavior and performance was analyzed using a mixed linear model (PROC MIXED). To determine when steers had established consistent dry matter intake (DMI), consistency was defined as when the DMI of a steer remained within one standard deviation of the 7-day average DMI of the steer. Latency to first bunk attendance (d), first feed consumption, attainment of NEm requirement, and latency (d) to establish consistent feed intake levels were analyzed using a generalized linear mixed model (PROC GLIMMIX) for binomial data. Steer BW increased across days (P < 0.01), whereas average daily gain was.48 ± 0.4 kg/d. All feeding behaviors changed across days (P < 0.01). Meal and bunk visit (duration and frequency), meal intake (mean and sum), head down duration, and maximum NFI increased over time. All steers visited the bunk and consumed their first meal by day 4 (P < 0.01). All steers achieved NEm requirements by day11 (P < 0.01). These results quantify the acclimation period of steers to a new environment and characterizes the learning and development of novel modes of eating. These results inform the development of behavioral expectations for newly received high-risk calves that can be used to monitor cattle health, understand cattle perception, and promote cattle welfare. [ABSTRACT FROM AUTHOR]

This experiment aimed to validate feed intake and bunk attendance data collected from a portable, self-contained feeding unit (SmartFeed; C-Lock Inc., Rapid City, SD) by comparing estimates collected electronically (electronic observations; EO) with direct observations and video recording (direct observations; DO). To validate individual animal intake, 30 cows were allowed access to 3 portable units (2 feeding bins/unit) for 6 hours. Feed in each bin was removed and weighed in an external scale at the end of each cow visit. To validate total feed disappearance, 75 cows were assigned to 1 of 3 pastures equipped with a portable unit. Feed disappearance over 24 h was assessed manually over 21 consecutive days using an external scale. Ten cows per pasture were randomly selected and identified to facilitate collection of video observational data. Two trained observers recorded animal identification and start and end times for a visit (n = 480 minutes/day; 3 days). When regressing the EO and DO results within individual cow visit, a linear fit was detected (P < 0.01; r2 = 0.95). Methods were very strongly correlated (r = 0.91) when all visits were analyzed but decreased to strong (r = 0.78) when DO intake was = 0.1 kg. When regressing the EO and DO results for total feed disappearance, a linear fit was detected (P < 0.01; r² = 0.97) as DO total feed disappearance increased the EO output linearly increased. For observational data, Cohen's kappa coefficient for agreement between DO and EO was considered strong (0.96). The sensitivity of EO in yielding true positive results was 97%, whereas specificity in yielding true negative results was 99%. These results indicate the portable, self-contained feeding units utilized herein are sufficiently effective for detecting cow presence at a bunk and measurement of feed consumption. [ABSTRACT FROM AUTHOR]