caa a22 4500 386319995 CHVBK 20180307111622.0 cr unu---uuuuu 161130e198810 xx s 000 0 eng 10.1017/S0003356100003287 doi S0003356100003287 pii (NATIONALLICENCE)cambridge-10.1017/S0003356100003287 Effects of oestradiol-17β or zeranol with or without trenbolone acetate on live-weight gain, carcass composition and zeranol residues in steers on an 18-month beef system [Elektronische Daten] A comparison of anabolic treatment regimes was made in 761 autumn-born Friesian steers on 14 farms. Prior to turn-out for grazing at 6 months of age and approximately 180 kg live weight, steers were weighed and divided into three equal-weight groups. Group 1 received silastic implants containing 45 mg oestradiol-17β. Group 2 received 36 mg zeranol and group 3 were untreated controls. All steers were weighed at intervals of approximately 3 months (i.e. mid summer, yarding at autumn, mid winter and pre-slaughter) and group 2 steers received a further 36 mg zeranol at the second, third and fourth weighing. At the third weighing half the cattle in each of the treatment groups 1 and 2 received 300 mg trenbolone acetate. Also at the third weighing, group 3 (controls) were subdivided into three equal-weight groups, the first of which received 45 mg oestradiol-17β and 300 mg trenbolone acetate and the second 36 mg zeranol and 300 mg trenbolone acetate. The third subgroup remained as untreated controls. From 10 farms a 25% sample close to group mean weight at mid winter were slaughtered on the same day and subjectively assessed for subcutaneous fat score and conformation on 15-point scales. The left thin flank was separated into tissues. Samples of lean fat, liver and kidney were analysed for zeranol residues. All implant treatments resulted in higher live-weight gain, heavier slaughter weights and earlier slaughter. Trenbolone increased daily gain only during the first 3 months after treatment. Implanted carcasses were heavier both in the fore- and hindquarter but trenbolone also produced heavier forequarters. Carcasses from treated steers had more subcutaneous fat, less perinephric and retroperitoneal fat and less intermuscular fat in the thin-flank joint. Zeranol residues in implanted steers were not significantly higher than controls except in the kidney, but even these were significantly below accepted tolerance levels. Copyright © British Society of Animal Science 1988 Southgate J. R. Meat and Livestock Commission, PO Box 44, Queensway House, Bletchley, Milton Keynes MK2 2EF Peters A. R. British Technology Group, 101 Newington Causeway, London SE1 6BU Dixon S. N. Food and Veterinary Laboratory Ltd, 25-26 Frederick Sanger Road, Surrey University Park, Guildford GU2 5YD Animal Production Cambridge University Press 47/2(1988-10), 209-214 0003-3561 47:2<209 1988 47 ASC https://doi.org/10.1017/S0003356100003287 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0003356100003287 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Southgate J. R. Meat and Livestock Commission, PO Box 44, Queensway House, Bletchley, Milton Keynes MK2 2EF NATIONALLICENCE 700 1- Peters A. R. British Technology Group, 101 Newington Causeway, London SE1 6BU NATIONALLICENCE 700 1- Dixon S. N. Food and Veterinary Laboratory Ltd, 25-26 Frederick Sanger Road, Surrey University Park, Guildford GU2 5YD NATIONALLICENCE 773 0- Animal Production Cambridge University Press 47/2(1988-10), 209-214 0003-3561 47:2<209 1988 47 ASC CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge