Effects of ractopamine hydrochloride on performance, rate and variation in feed intake, and acid-base balance in feedlot cattle1

Abstract

Two experiments evaluated effects of ractopamine hydrochloride (RAC) on performance, intake patterns, and acid-base balance of feedlot cattle. In Exp. 1, 360 crossbred steers (Brangus, British, and British x Continental breeding; initial BW = 545 kg) were used in a study with a 3 x 3 factorial design to study the effects of dose [0, 100, or 200 mg/(steer x d) of RAC] and duration (28, 35, or 42 d) of feeding of RAC in a randomized complete block design (9 treatments, 8 pens/treatment). No dose x duration interactions were detected (P > 0.10). As RAC dose increased, final BW (FBW; P = 0.01), ADG (P < 0.01), and G:F (P < 0.01) increased linearly. As duration of feeding increased, ADG increased quadratically (P = 0.04), with tendencies for quadratic effects for FBW (P = 0.06), DMI (P = 0.07), and G:F (P = 0.09). Hot carcass weight increased linearly (P = 0.02) as dose of RAC increased. Thus, increasing the dose of RAC from 0 to 200 mg/(steer x d) and the duration of feeding from 28 to 42 d improved feedlot performance, although quadratic responses for duration of feeding indicated little improvement as the duration was extended from 35 to 42 d. In Exp. 2, 12 crossbred beef steers (BW = 593 kg) were used in a completely random design to evaluate the effects of RAC [0 or 200 mg/(steer x d) for 30 d; 6 steers/treatment] on rate of intake, daily variation in intake patterns, and acid-base balance. To assess intake patterns, absolute values of daily deviations in feed delivered to each steer relative to the total quantity of feed delivered were analyzed as repeated measures. There were no differences (P > 0.10) in feedlot performance, urine pH, blood gas measurements, or variation in intake patterns between RAC and control cattle, but steers fed RAC had increased (P = 0.04) LM area, decreased (P = 0.03) yield grade, and increased (P < 0.10) time to consume 50 and 75% of daily intake relative to control steers. Our results suggest that feeding RAC for 35 d at 200 mg/(steer x d) provided optimal performance, and no effects on acid-base balance or variation in intake patterns of finishing steers were noted with RAC fed at 200 mg/(steer x d) over a 30-d period.

Effect of ractopamine hydrochloride and zilpaterol hydrochloride on growth, diet digestibility, intake and carcass characteristics of feedlot lambs

“…Moody et al (2000) argue that increased weight gain and feed efficiency are generally expected when β-AA are included in animal feeding; although, variations in response to β-AA administration are common throughout published studies. Contrary to what has been observed in the present study, increments in ADG, FE, total gain and final BW have been reported in beef cattle fed RH (Abney et al, 2007;Winterholler et al, 2008) and ZH (Montgomery et al, 2009b;Plascencia et al, 2008;Vasconcelos et al, 2008), and in sheep fed RH (Robles-Estrada et al, 2009b) and ZH (Estrada-Angulo et al, 2008;RoblesEstrada et al, 2009b;Salinas-Chavira et al, 2004). However, in line with the present study, Quinn et al (2008) found that ADG by beef cattle was unaffected by RH administration; likewise Aguilera-Soto et al (2008) and Felix et al (2005) did not find any influence of ZH on ADG.…”

“…Feed efficiency ratio (FE) ([kg weight gain/kg feed intake] × 100) was calculated for every feeding period. Absolute within pen dayto-day variation in intake (DMI variation) was calculated as described for Abney et al (2007) as, DMI variation = (|d2 − d1|/d1) × 100; where d2 was the feed delivered the current day, and d1 was the feed delivered the previous day.…”

Ractopamine hydrochloride on performance and carcass traits of confined Nellores cattle

“…Similar results were observed by QUINN et al (2008), when fed cattle in termination diets containing 9.1; 18.2 and 27.3ppm of ractopamine hydrochloride, with increases in weight gain in 17.1, 19.6, and 25.7%, respectively, compared to bovine animals not supplemented with this beta blocker. These results presented here were also corroborated by those obtained by ABNEY et al (2007) with improvement in weight gain of cattle fed diets supplemented with Ractopamine. The increase in cattle weight gain probably has occurred due to the effect of this additive on the modification of cellular metabolism, which would promote increased protein synthesis and decreased lipogenesis.…”

The effect of zilpaterol hydrochloride on meat quality of calf-fed Holstein steers

“…extensively studied in beef cattle to produce animals that are heavier, have improved ADG, and have in creased feed efficiency (Avendaño-Reyes et al, 2006;Abney et al, 2007). In addition, use of BAA produces carcasses that are heavier and yield leaner meat (Molo ney et al, 1994).…”