Dunne P G, O'Mara F P, Monahan F J, Moloney A P
Teagasc, Grange Research Centre, Dunsany, Co. Meath, Ireland; School of Agriculture, Food Science and Veterinary Medicine, University College Dublin, Dublin 4, Ireland.
Meat Sci. 2006 Oct;74(2):231-41. doi: 10.1016/j.meatsci.2006.02.003. Epub 2006 May 19.
The objective of this experiment was to determine the effect of dietary composition and duration of feeding on subcutaneous (s.c.) adipose tissue and M. longissimus dorsi (LD) colour and pigment concentrations of heifers. Fifteen heifers were permanently housed and fed a concentrate diet (PH-CON). Fifty-four heifers were grazed on pasture (PAS) for 90d, housed and offered concentrates (PAS-CON), 200g grass silage (GS)/kg dry matter (DM) (PAS-GS20), 500g GS/kgDM (PAS-GS50) or zero-grazed grass (PAS-GRA). To facilitate assessment of the temporal pattern of tissue colour, 3 heifers/treatment were slaughtered at housing (following 7d adjustment to diets) and 28, 56, 91 and 120 days thereafter. Yellowness ('b' value) of s.c. adipose tissue and lightness ('L' value) and redness ('a' value) of LD were recorded 48h post-mortem. β-Carotene and lutein contents of s.c. adipose tissue and total LD haem pigments were determined. At housing, s.c. adipose tissue 'b' values of the PAS group (mean=13.47) were higher (P<0.01) than those of the PH-CON group (mean=10.35) but there was no difference in β-carotene or lutein concentrations. The change in s.c. adipose tissue 'b' for each diet following housing was best described by the following equations: PH-CON: y=-0.087 (SE 0.0347) X+0.0005 (SE 0.00029) X(2)+10.06 (SE 0.600), MSE 1.94, R(2) 0.57, P<0.01. PAS-CON: y=-0.102 (SE 0.0286) X+0.0006 (SE 0.00024) X(2)+13.32 (SE 0.598), MSE 2.30, R(2) 0.62, P<0.001. PAS-GS20: y=-0.106 (SE 0.0296) X+0.0008 (SE 0.00025) X(2)+13.10 (SE 0.618), MSE 2.46, R(2) 0.47, P<0.01. PAS-GS50: y=-0.077 (SE 0.0269) X+0.0006 (SE 0.00023) X(2)+13.29 (SE 0.552) MSE 1.95, R(2) 0.38, P<0.05. PAS-GRA: y=-0.018 (SE 0.0079) X+13.77 (SE 0.528), MSE 2.28, R(2) 0.24, P<0.05, where y='b' value, x=days post-housing (d96-d216) and MSE=mean square error. Treatment had a significant effect on s.c. adipose tissue β-carotene and lutein (both P<0.001) with PAS-GRA and PH-CON tending to have the highest and lowest concentrations, respectively. PH-CON heifers tended (P=0.058) to have lower LD haem pigments and lighter LD than other heifers. It is concluded that, while concentrate feeding led to the greatest decrease in s.c. adipose tissue yellowness relative to PAS-GRA, choice of dietary ingredients and duration of feeding will depend on the stringency of the colour criteria in particular markets.
本实验的目的是确定日粮组成和饲喂持续时间对小母牛皮下（s.c.）脂肪组织以及背最长肌（LD）颜色和色素浓度的影响。15头小母牛被永久圈养并饲喂精料日粮（PH-CON）。54头小母牛在牧场放牧90天，然后圈养并提供精料（PAS-CON）、200克青贮草（GS）/千克干物质（DM）（PAS-GS20）、500克GS/千克DM（PAS-GS50）或零放牧青草（PAS-GRA）。为便于评估组织颜色的时间变化模式，每个处理组在圈养时（适应日粮7天后）屠宰3头小母牛，此后在第28、56、91和120天各屠宰3头。宰后48小时记录皮下脂肪组织的黄度（“b”值）以及背最长肌的亮度（“L”值）和红度（“a”值）。测定皮下脂肪组织的β-胡萝卜素和叶黄素含量以及背最长肌总的血红素色素含量。在圈养时，PAS组皮下脂肪组织的“b”值（平均值 = 13.47）高于PH-CON组（平均值 = 10.35）（P<0.01），但β-胡萝卜素或叶黄素浓度无差异。圈养后每种日粮皮下脂肪组织“b”值的变化可用以下方程最佳描述：PH-CON：y = -0.087（标准误0.0347）X + 0.0005（标准误0.00029）X² + 10.06（标准误0.600），均方误差1.94，R² 0.57，P<0.01。PAS-CON：y = -0.102（标准误0.0286）X + 0.0006（标准误0.00024）X² + 13.32（标准误0.598），均方误差2.30，R² 0.62，P<0.001。PAS-GS20：y = -0.106（标准误0.0296）X + 0.0008（标准误0.00025）X² + 13.10（标准误0.618），均方误差2.46，R² 0.47，P<0.01。PAS-GS50：y = -0.077（标准误0.0269）X + 0.0006（标准误0.00023）X² + 13.29（标准误0.552），均方误差1.95，R² 0.38，P<0.05。PAS-GRA：y = -0.018（标准误0.0079）X + 13.77（标准误0.528），均方误差2.28，R² 0.24，P<0.05，其中y为 “b” 值，x为圈养后天数（d96 - d216），均方误差 = 均方。处理对皮下脂肪组织的β-胡萝卜素和叶黄素均有显著影响（均P<0.001），PAS-GRA组和PH-CON组的浓度分别趋于最高和最低。PH-CON组小母牛的背最长肌血红素色素含量趋于较低（P = 0.058），且背最长肌比其他小母牛更浅。得出结论，相对于PAS-GRA组，精料饲喂导致皮下脂肪组织黄度下降最大，日粮成分的选择和饲喂持续时间将取决于特定市场颜色标准要求的严格程度。
