The effect of post weaning nutrition on the total fat content of cube roll (Longissimus dorsi) steaks from Brahman cross steers. (Short Communication)

Abstract

1OA THE EFFECT OF POST WEANING NUTRITION ON THE TOTAL FAT CONTENT OF CUBE ROLL (Longissimus dorsi) STEAKS FROM BRAHMAN CROSS STEERS I.D, LOXTON*, A.R. NEILL**, T.A. JAMES*'*, G.W. BLIGHT+, W.R. SHORTHOSE++ and R.G. HOLROYD+ In recent years, the public awareness of the role of animal products in the human associations between dietary patterns and the development of chronic degenerative heart disease Information on the fat content of lean portions of Australian beef has O'Dea (1987) published data based on Bos taurus breeds, while data from Bos indicus unavailable. diet has increased due to diseases such as coronary been limited. Sinclair and sourced animals has been At Brlgalow Research Station, Theodore, 624 Brahman crossbred steers from two year drafts were grown at four different nutrItiona regimes between weaning and turnofrat target carcase weights of 185,260 and 320 kg- The nutrItiona regimes comprised combinations of differing annual nutritional levels (growth rates) between weaning and each target car-case weight. The annual growth rates were 180kgYyear (H). 130kdyear (M) and 80kg/year (L) &x- the grassf;ed regimes and 3OOk@year (II*) for the g&tied regime (grain supplemented in paddock to 185 and 260kg car-case weight, or grain supplemented in paddock plus lot fed to 320kg carcase weight).. The combinations were LMH, MMM HHH in both drafts and H+ in one draft only. At 24 hours post slaughter. chilled samples of the cube roll (hngissimus dorsi, LD) were collected from each carcase? adjacent to the quarsering point between the eighth and twelfth thoracic vertebrae. Samples were plastic wrapped and frozenA 1OOg sample was sawn from the frozen LD before thawing at 56�C for 48 hours, finely minced, freeze dried, then soxhlet extracted with petroleum ether (b.p. 40-60') for 16 hours in order to determine total fat content. Data (excluding H* data) were tested by analysis of variance using the method of least squaresGrowth rates (kg/hcVd) between weaning and turnoff increased significantly with improved nutrition . ~,IIHEH(O.563)~MMM(O.467)~LMH(0.399)~ P~0.05) while growth rates across all regimes to 185kg target carcase weight were si@fkantYy greater (IkO.05) than to the 260 or 3ZOkg target carcase weight (0527>0.462 and 0.446)). The target carcase weight by nutritional regime interaction for growth rate was significant (P~0.05)~ Growth rates of the H-b nutritional regime were 0.743 to the 185kg, 0.578 to the 260kg and 0.652 to the 320kg ixget carcase weight. The nutritional regime had no significant effect (P>O.O5) on the total fat content of the lean (denuded of all surface fat) L.D samples, however, fat content increased significantly (P~0.05) as the target carcase weight increased (Table 1)- A similar trend occurred across target carcase weights (P-36, 2.06 and 4.14%, Average SEM of k 0.17%) for the H+ nutritional regime. The interaction between target carcase weight and nutritional regime for total fat content was not significant (P>O.O5). Although not statistically tested, there was no difference in LD fat content between the grassfed groups (LMH, MMM and HHH) and the graintd groups (H+) at any of the target carcase weights. In this study. the animals nutritional regime has not influenced total fat content of the LD. The total fat content of the LD from Brahman cross animals, is lower than the fat content of 2.3% and 3.9% from Hereford carcases weighing 209 and 258kg (Sinclair and O'Dea 1987). Prom both studies, fat content of the LD was low, which &odd help correct the perception that selective beef cuts are high in fat and thus unhealthy. The financial support of the Meat Research Corporation and assistance of QDPI and CSIRO staff is gratefully * . a&now [edged- _ SimIairq A.J. and O'Dea, K Cl987). Food Tech. in Aust. 39: 228. k *J; *** + -(c-c Queenslanc8 Department of Primary Industries, Box 6014 Rockhampton Mail Centre, QLD, 4702 Queensland Department of Primary Industries, Queensland Department of Primary Industries, Queensland Department of Primaly Industries, CSIRO. Meat Research Laboratory, Cannon Hill, GP0 Box 46 Brisbane, QLD, 4001 Brigalow Research Station, Theodore, QLD, 4719 Animal Research Institute, Yeerongpilly, QLD, 4105 QLD, 4170