Investigating methods for using ractopamine hydrochloride in domestic beef cattle and factors affecting body condition of cattle on Il N'gwesi Group Ranch in Kenya, Africa
Abstract
Two experiments were conducted to evaluate the effects of ractopamine hydrochloride (RH) supplementation on 1) feeding performance and carcass characteristics of finishing steers, and 2) reproductive efficiency and maintenance of body condition of lactating primiparous cows. An additional experiment was conducted to determine physical factors of Kenyan cattle that contribute to differences in body condition. To determine the impact of RH on feedlot performance in cattle, 36 steers were blocked by initial body weight (BW), and randomly assigned to one of three treatments 1) control (0 mg RH fed: CON), 2) daily supplementation of 200 mg RH from d 0 to d 42 (CNT) and 3), daily supplementation of 100 mg RH from d 0 to d 21, no RH from d 21 to 28, and daily supplementation of 300 mg RH from d 28 to d 42 (STEP), all cattle were harvested prior to feeding on d 43. Steers in the CON treatment had greater marbling scores ( P = 0.04) than CNT, with STEP being intermediate to both treatments. Quality grade tended to differ (P = 0.08) between treatments. The CON treatment of steers had greater quality grade scores compared to the CNT treatment with STEP being intermediate to both. Feeding performance was not altered due to RH supplementation when fed continuously or in a step-up design over a period of 42 days. Carcass quality was not improved, and continuous RH administration may have a negative effect on marbling, and final quality grades of beef steers. To determine the impact of RH on reproductive function and weight changes in cows, 64 primiparous cows were stratified and blocked by days postpartum (DPP), resumption of estrus, BW, and body condition score (BCS), to receive either a control diet (CON) or a control diet including 300 mg/hd/d RH (OPT) fed 35 d prior to breeding. Cows in the CON treatment had greater (P < 0.01) daily losses in BW than the OPT treatment group (-1.08 ± 0.09 and -0.71 ± 0.09 kg/d, respectively). At the conclusion of the feeding period BCS of the CON treatment (5.55 ± 0.11) were decreased (P < 0.01) compared to the OPT treatment (6.02 ± 0.11). Timed AI (68.75%, 53.13%) and breeding season pregnancy rates 84.38% and 71.88%, CON and OPT, respectively) did not differ between treatments. Inclusion of RH in cow diets increased nutritional status, however, dietary RH failed to improve reproductive performance. The objective of the final study presented was to evaluate the factors affecting the body condition of cattle on Il N'gwesi group ranch in central Kenya, Africa. Weanling and yearling aged cattle had greater BCS (P < 0.001) than mature cattle (3.52, 3.66, and 3.08, respectively). Steers, bulls and heifers had greater BCS (P < 0.001) than cows (3.73, 3.60, 3.59, and 2.88, respectively). Additionally, there was a hide color × frame score (FS) interaction (P < 0.01), indicating the greatest BCS of light colored cattle is at FS-3, and the greatest BCS of dark colored cattle is at FS-4. Therefore, heifers, steers, and bulls, may be more apt to survive than mature cows, and hide color in relation to FS should be used as selection criteria.
Degree
M.S.
Advisors
Tormoehlen, Purdue University.
Subject Area
Animal sciences
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.