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The impact of oestradiol only hormone growth promotants (HGPs) on eating quality

Pasture finished steers

A total of 200 Bos indicus/Bos taurus previously un-implanted steers were randomly allocated to two treatment groups; control (CON) or a 400 day oestradiol only (OES) HGP implant, and finished on pasture for 389 days to assess the impact of the OES implant on sensory and objective measurements of the mm. longissimus thoracis et lumborum (LTL) and gluteus medius (GM). The HGP treatment had a significant impact on live weight, carcass weight and ossification (P<0.05). There was a trend to decrease marbling scores, and increase ribfat, P8 fat depth and hump height. The HGP treatment interacted with days aged for all sensory scores in the LTL, apart from juiciness (P<0.01) whereby OES sensory scores for the LTL and GM were significantly lower than the CON group at 5 days, though the magnitude halved in the LTL after 35 days of aging. There was a trend for a days aged X HGP interaction in the GM for shear force (P=0.057), but not in the LTL (P>0.05). Shear force scores were significantly higher for the OES treatment in the LTL at 5 days (P<0.05), though reduced through aging. The HGP treatment significantly increased cooking loss in the LTL (P<0.05) but only a trend was present in the GM. The OES treatment significantly reduced L*, a* and b* colour dimensions for the LTL (P<0.05) but not the GM (P>0.05). Calpastatin activity was significantly greater for the OES treatment, which may aid in explaining part of the large impact on sensory and shear force scores at 5 days’ post mortem.

Feedlot finished steer carcasses

The Meat Standards Australia (MSA) beef grading model applies a variable penalty for different cuts for Hormonal Growth Promotant (HGP) treated carcasses but does not differentiate between different HGP types. Using 300 non implanted Bos indicus/Bos taurus composite steers an experiment was conducted to compare the effects on eating quality in the mm. longissimus dorsi (LD) and gluteus medius (GM) muscles of an oestradiol only (OES) and a combination trenbolone acetate with oestradiol (TBA+OES) implant with non-implanted animals (CON) fed a concentrate ration for 73 days prior to slaughter. Sensory and objective LD and GM samples were aged for either 5 or 35 days before freezing at -20°C. Carcass weights from each group were significantly different (P<0.05). Corrected for carcase weight, both HGP treatments had a significant effect on hump height, ossification score, marble score, P8 fat depth and eye muscle area. The TBA+OES treatment resulted in significantly tougher meat than the OES and CON treatments as assessed by shear force (P<0.05), although this difference was reduced with aging. Sensory scores (tenderness, juiciness, like flavour, overall liking and a composite MQ4 score) confirmed a negative HGP treatment effect, whereby TBA+OES was significantly lower than the CON and OES groups after 5 days of aging, and these differences were reduced through aging. TBA+OES had a greater impact on sensory scores in the LD when compared to the GM.  Both HGP treatments increased calpastatin activity, and the TBA+OES group was significantly different to the CON and OES groups (P<0.05). It was concluded that OES and TBA+OES implants have different impacts on meat eating quality measurements, which could have important implications for the Australian and international beef industry.


Title Size Date published
648.6KB 19/12/2016
587.8KB 30/06/2017


Contract No. Title Start date End date Funding type
The effect of oestradiol and trenbolone acetate combination implants on beef eating quality
01/05/2014 30/06/2017

This page was last updated on 10/10/2017

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