Browsing IJAFR, volume 43, 2004 by Author "Monahan, Frank J"
Colour of subcutaneous adipose tissue and muscle of Irish beef carcasses destined for the Italian market.Dunne, Peter G.; O'Mara, Frank P.; Monahan, Frank J; Moloney, Aidan P; National Development Plan, 2000–2006; Teagasc Walsh Fellowship Programme (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)The purposes of this study were (i) to objectively measure the colour of carcass fat and muscle of heifers that had been previously selected, subjectively, for the Italian market and (ii) to define instrumental colour values which would describe the required fat colour for that market. On one day during each of 5 months (11 April, 13 June, 10 October, 10 November and 19 December) the ‘b’ (yellowness) value of carcass fat was measured at two positions (proximal pelvic limb area and the area between 9th rib and 4th lumbar vertebra) and the ‘L’ (lightness) and ‘a’ (redness) values of two muscles (M. longissimus dorsi (LD) and M. rhomboideus thoracis (RT)) were measured using a Minolta chromameter. Measurement date had a significant effect (P < 0.05) on ‘b’ values of fat at both positions, with carcasses displaying the most yellow fat on 13 June (P < 0.05). The LD was palest and most red on 11 April (P < 0.05) and the RT tended to be palest on 13 June but most red (P < 0.05) on 11 April. The ‘L’ value differed between muscles on 11 April (P < 0.01) and 19 December (P < 0.05) and the ‘a’ value differed between muscles on all dates except 13 June. The majority of carcasses on each date fell between muscle ‘L’ values of 31 and 35, regardless of muscle, and between muscle ‘a’ values of 18 and 22. It is concluded that application of a “cut-off” value to muscle colour would be futile but as 81% of accepted carcasses had fat ‘b’ values below 14.2, regardless of position, that this could be used as a threshold of acceptable yellowness.
Comparison of concentrates or concentrates plus forages in a total mixed ration or discrete ingredient format: effects on beef production parameters and on beef composition, colour, texture and fatty acid profileCooke, D.W.I; Monahan, Frank J; Brophy, P.; Boland, Maurice (Teagasc (Agriculture and Food Development Authority), Ireland, 2004)Diets consisting primarily of concentrates or of concentrates plus silage in a total mixed ration (TMR) or discrete ingredient format were compared for effects on beef production traits and on beef quality. Sixty continental cross heifers (377 kg, s.d. 31) were allocated to one of the following feeding regimens for 96 days pre-slaughter: (i) a control ration of grass silage, maize silage, a cereal-based concentrate and straw at proportionately, 0.23, 0.15, 0.59 and 0.03 of dietary dry matter, respectively; (ii) a total mixed ration (TMR) with the same dietary ingredients as the control ration; (iii) a high concentrate ration (HC) of a cereal-based diet and straw at proportionately 0.95 and 0.05 of dietary dry matter, respectively. Subcutaneous fat samples were taken from all animals at slaughter and the strip-loin was excised from 10 animals per group for colour, texture and fatty acid determination. The HC and TMR groups had higher (P < 0.05) daily live-weight gain, slaughter weight and carcass weight than the control group. Muscle protein was highest (P < 0.01) in the TMR group while muscle marbling was highest (P < 0.01) in the HC group. Subcutaneous fat from the HC group was less (P < 0.001) yellow than fat from the other groups. Fatty acid analysis of intramuscular fat showed that the HC group had higher C18:1 and lower C18:3 proportions than the control group (P < 0.05). The n-6:n-3 fatty acid ratio of intramuscular fat from the HC group was higher (P < 0.05) than that of the other groups. The results suggest that, at similar feed intakes, TMR feeding offers advantages for beef production over feeding ingredients separately, and yields muscle with a higher protein concentration, while high concentrate feeding yields whiter subcutaneous fat and intramuscular fat with a less nutritionally favourable n-6:n-3 fatty acid ratio.