QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rumsey, T. S. Articles by Kahl, S. Search for Related Content PubMed PubMed Citation Articles by Rumsey, T. S. Articles by Kahl, S.

Roasted Soybeans and an Estrogenic Growth Promoter Affect Growth Hormone Status and Performance of Beef Steers^1,2,3,

Growth Biology Laboratory, Livestock and Poultry Sciences Institute, ARS, USDA, Beltsville, MD 20705-2350 ^* Department of Animal Sciences, University of Maryland, College Park 20742

This study investigated the effects of a roasted soybean (RSB)-supplemented diet and an estrogen implant (SYN; Synovex-S® ear implant, 20 mg estradiol benzoate plus 200 mg progesterone) in young crossbred beef steers on their performance and plasma growth hormone (GH) response to challenge injections of thyrotropin-releasing hormone (TRH) + GH-releasing hormone (GHRH). Twenty individually fed steers (body weight 255 ± 5 kg) were assigned to the following treatments: 1) no SYN and fed a soybean meal-supplemented diet, 2) no SYN and fed the RSB-supplemented diet, 3) plus SYN and soybean meal, and 4) plus SYN and RSB. Steers were fed 1.13 MJ metabolizable energy/kg metabolic body weight daily of an 18% protein diet. After a 5-wk growth period, all steers were challenged (intravenous injection) over a 3-wk period with three levels of a combination of TRH + GHRH (0.1 + 0.01, 1.0 + 0.1, 2.5 + 0.25 µg/kg body weight, respectively). After an additional 3 wk, steers were reimplanted and a second 5-wk growth period was followed by a single challenge of the 1.0 + 0.1 TRH + GHRH dose level. Plasma nonesterified fatty acid concentration was greater when steers were fed the RSB compared with soybean meal (265 vs. 205 µmol/L; P < 0.01; SEM = 9.5). Body weight gains for treatments 1, 2, 3 and 4 were 1.35, 1.21, 1.47 and 1.38 kg/d, respectively (RSB, P < 0.10; SYN, P < 0.07; SEM = 0.06). Gain/dry matter intake (g/kg) means were 184, 167, 197 and 184 (RSB, P < 0.04; SYN, P < 0.07; SEM = 7.5). Feeding roasted soybeans resulted in depressed area under the GH response curve [907, 555, 827 and 989 µg/(L*min) (SYN x RSB, P < 0.03; SEM = 117)] and depressed peak response (37.2, 26.6, 33.5 and 41.1 µg/L [SYN x RSB, P < 0.05; SEM = 4.5]), an effect alleviated by estrogen for young growing steers (Period 1) but not for heavier steers (Period 2).

KEY WORDS: • beef cattle • estrogens • somatotropin • thyrotropin releasing hormone • soybeans

¹ Presented in part in abstract form at Experimental Biology 95, April 1995, GA [Rumsey, T. S., Elsasser, T. H. & Kahl, S. (1995) Effect of an estrogenic growth promoter and roasted soybeans on weight gain and response to TRH-GHRH in beef steers. FASEB J. 9: A1019 (abs.)].

² Mention of a trade name, proprietary product, or specific equipment does not constitute a gaurantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.

³ The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

⁴ To whom correspondence should be addressed: Bldg. 200, Rm 102, BARC-East.

Manuscript received 19 March 1996. Revision accepted 12 July 1996.