Yellow fat reduces the acceptability and value of beef table cuts within the high priced Asian markets. The concentration of carotenoids in fat, leads to this yellowness. A systems experiment which ran for 2 years, studied the effects of nutrition and age on fat carotenoid concentration (FCC). In each year, rising 1-year (R1) and 2-year (R2) Angus steers were offered either full access to winter and spring feed (fast rotation, FR); or were nutritionally restricted during winter (slow rotation, SR) and then given full access to feed during spring. Fat biopsy samples were collected every 4 months and carotenoid concentration determined. FCC increased as animals became older. The effect of the nutritional growth path was to increase FCC during winter where feeding was restricted, particularly in the R1 steers. In both years, the SR systems compensated during spring, with both live weight and FCC being similar for the 2 nutrition treatments by the end of spring. From a practical perspective, farmers who seek to supply beef with satisfactory fat colour should not restrict feeding during the period of 3-4 months prior to slaughter. The experiment also provided data which allowed FCC to be followed from weaning through to slaughter for individual animals. These data provided the opportunity to investigate the prediction of carcass FCC based on earlier fat measurements. Correlations (r) ranged from 0.31 at 24 months to 0.71 at 3 months before slaughter. Correlations are not sufficiently strong to justify early selection of cattle for targeted markets and growth paths. However, there is opportunity for processors to use fat biopsy and objective colour measurement techniques in the selection and purchase of cattle for high priced markets.
Proceedings of the New Zealand Society of Animal Production, Volume 57, , 282-285, 1997
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