The objective of this study was to evaluate the influence of dietary protein and fat from distillers dried grains with solubles (DDGS) on feedlot performance, carcass characteristics, and meat quality in finishing steers. Angus-cross steers (n = 105; 443 +/- 20 kg of BW) were blocked by BW and randomly assigned to 1 of 5 dietary treatments: 1) corn-based diet with DDGS included at 25% of DM (CON), 2) CON with DDGS included at twice the amount of CON (50% of DM; 50DDGS), 3) CON with added corn protein to equal the CP in the 50DDGS diet (CON+CP), 4) CON with added vegetable oil to equal the fat in the 50DDGS diet (CON+VO), and 5) CON with protein and fat added to equal the CP and fat in the 50DDGS diet (CON+CPVO). Steers were fed to a common 12th-rib fat depth endpoint (1.3 +/- 0.2 cm; 68 to 125 d on trial). Loins and rounds were collected from 44 carcasses for Warner-Bratzler shear force (WBSF), ether extract, and case-life analyses. Data were analyzed using the MIXED procedure of SAS. Contrasts between 1) CON vs. elevated CP diets (50DDGS, CON+CP, and CON+CPVO; EP), 2) CON vs. elevated fat diets (50DDGS, CON+VO, and CON+CPVO; EF) and 3) CON vs. diets with elevated CP and fat (50DDGS and CON+CPVO; EPF) were analyzed. There were no differences in days on feed or DMI among treatments. Steers fed CON had greater ADG (P
To determine effects of clenbuterol (CB) on muscle protein turnover and growth hormone (GH) secretion, 16 crossbred wether lambs (14.4 kg) were randomized into two groups designated to receive daily oral boluses of gelatin capsules containing corn starch with either 0 (control, CTL) or 1.87 mg/kg body weight CB for either 14 (n = 8) or 28 d (n = 8). This calculates to be approximately 40 mg CB/kg diet. Lambs had ad libitum access to a 16% crude protein corn-soy diet and feed consumption (FC) was measured. After 14 and 28 d, lambs were slaughtered and semitendinosus (ST), longissimus (LD) and brachialis (BR) muscles were exercised, weighed and analyzed for protein (TP) content. For 6 h prior to slaughter of 28-d lambs, 2.5 microCi L-[U-14C]tyrosine/kg was infused intravenously, blood was sampled and plasma was analyzed for specific radioactivity of tyrosine. Plasma GH concentrations were assessed by radioimmunoassay. No differences due to treatment were found in FC, rate of gain or GH concentrations. Semitendinosus and BR weights of control lambs at 14 d did not differ between treatments. At 28 d, ST and BR weights of control lambs (58.8 and 18.5 g, respectively) were less (P less than .10) than those of lambs treated with CB (74.3 and 23.1 g, respectively). The TP per ST and BR at 28 d for control lambs was 71.5 and 85.1% (P less than .10) that of muscles of lambs treated with CB. Fractional protein synthesis rates (FSR) of the BR (9.4 vs 6.1%/d) and total protein synthesized in ST muscle per day (1.4 vs .8 g) were elevated (P less than .10) in lambs treated with CB compared to controls. These data suggest that the increased fractional accretion rate observed in lambs treated with CB for 28 d was caused by increased FSR.
Raising beef cattle on concrete floors can negatively impact their welfare by increasing joint swelling and body lesions, as well as abnormalities in resting behavior and postural changes. We hypothesized that the addition of rubber mats to concrete pens would improve beef cattle welfare by improving performance, health, hygiene, and resting behavior. Forty-eight crossbred Angus steers were housed in pens of 4 and randomly assigned to a single flooring treatment: (1) fully slatted concrete (CON), (2) fully slatted rubber mat (SLAT), or (3) solid rubber mat (SOLID; 60% of pen floor) from 36 to 48 wk of age. Weight, ADG, lesions, gait score, joint swelling, and animal and pen cleanliness were collected every 2 wk. Behavioral time budgets and frequency of postural changes (an indicator of floor traction and comfort) were collected at 0, 6, and 12 wk. No differences in weight gain or ADG were observed. Steers on SOLID flooring (0.80 ± 0.08) showed increased lesions compared to SLAT (0.38 ± 0.08) and CON (0.37 ± 0.08; both, = 0.05); however, there was no difference between SLAT and CON. SLAT steers (1.69 ± 0.04) showed a reduced gait score compared to SOLID (1.95 ± 0.04) and CON (1.98 ± 0.04; both, < 0.05), but SOLID and CON did not differ. Steers on SLAT flooring had less joint swelling (both knees and hocks) compared to SOLID and CON (all comparisons, < 0.05), but SOLID and CON did not differ. Steers on SOLID (3.64 ± 0.05) flooring were dirtier than those on SLAT (2.27 ± 0.05) and CON (2.19 ± 0.05; both, < 0.001), whereas SLAT and CON were similar. Additionally, SOLID and SLAT pens were less clean than CON pens ( < 0.001 and = 0.094, respectively), and SOLID was less clean than SLAT ( < 0.001). Time budget behavior was affected by treatment ( = 0.043), where SOLID differed from CON and SLAT (both, < 0.05). Steers on SOLID flooring preferred to rest on the rubber mat vs. slatted concrete ( = 0.001). Steers on SLAT flooring changed their posture more frequently than those on SOLID and CON flooring (both, < 0.05), but SOLID and CON did not differ. Compared to CON steers, SOLID steers showed an increase in lesions and a reduction in cleanliness, whereas SLAT steers showed a decrease in gait score and joint swelling and an increase in postural changes. Combined, these data suggest that the addition of slatted rubber mats to concrete pens may improve beef cattle welfare.
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