Farm Animal Metabolism and Nutrition

Juiciness

Genetic selection for leanness results in a

consistent decrease in cooked meat juici-

ness (Wood and Warris, 1992). A meat

quality advantage of phenethanolamine

repartitioning agents is that they improve

leanness without reducing juiciness. This

could be related to a lack of effect on

marbling. Aalhus et al. (1990) showed

reductions in both subcutaneous and

intermuscular (seam) fat in swine fed

ractopamine with no reduction of intra-

muscular fat. Merkel et al. (1990) and

Anderson et al.(1988) showed a similar

effect, although the phenomenon was time

related. Short-term feeding of phene-

thanolamines results in a decrease in only

subcutaneous and seam fat, while longer

term treatment also affects marbling (Fig.

4.5). Therefore, longer term treatment with

phenethanolamines may also result in

reduced juiciness as seen with genetic

selection for leanness. Short-term treatment

with phenethanolamines at the end of the

finishing period should allow improved

leanness without affecting juiciness.

Additional meat quality traits

Merkel (1988) reported that phenethano-

lamine treatment has negligible effects on

additional qualitative traits such as meat

flavour, colour, firmness, marbling and

water-holding capacity (WHC). More recent

work has shown small, but consistent effects

on colour (Uttaro et al., 1993; Schroeder,

personal communication, 1999) and WHC

(Uttaro et al., 1993). Ractopamine feeding

results in a small, but consistent reduction

Phenethanolamine Repartitioning Agents 73

Fig. 4.5.Effect of length of ractopamine feeding on carcass fat content of finishing pigs. Ether extracts of

subcutaneous + seam fat + marbling, seam fat + marbling, and marbling are shown as a percentage of the

control for four treatment lengths. Marbling appears to be depleted more slowly than other fat depots. (Data

adapted from Anderson et al., 1988.)

100

90

80

70

60

50

Percentage of control

0 5 7.5 10

Treatment length (weeks)

Subcutaneous, seam fat,

and marbling

Seam fat and marbling

Marbling

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