Date of Award:

2012

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Nutrition, Dietetics, and Food Sciences

Advisor/Chair:

Dr. Daren P. Cornforth

Abstract

There is currently much interest in the comparative health benefits of various meat products, including pasture-fed beef. However, little is known about the specific pasture-finishing diets (mixed forages, alfalfa, or sainfoin, compared to grain) on meat quality, consumer preferences, and human health. Thus, additional information is needed to better understand and develop new animal feeding regimes for optimum animal growth, meat flavor, and meat nutritional quality. The objective of the current study was to examine how animal diets, including secondary metabolites in the diet, affect meat chemical characteristics, meat quality, and nutritional value. In study 1 (Chapter 3), grain- vs. pasture-fed beef rib steaks were evaluated. Ribs from pasture-fed animals had a much lower fat content (P < 0.01), which was its main positive nutritional attribute. Pasture-fed beef had more (P < 0.05) omega-3 polyunsaturated fatty acids (PUFAs) and conjugated linoleic acid (CLA) than grain-fed beef, but was only a moderately good source of PUFA, compared to salmon. Pasture-fed beef had higher antioxidant capacity and lower measures of oxidation (P < 0.05). Pasture and grain diets influenced the volatile profile of cooked meat. Flavor descriptors barny, gamey, and grassy were associated with pasture feeding, and were uniquely shown in this study to be positively correlated with specific aroma volatiles benzaldehyde, toluene, dimethyl sulfone, 3- heptanone, 2-ethyl-1-hexanol, and hexadecanoic acid methyl ester (P < 0.05). In study 2 (Chapter 4), the effects of legume pasture-finishing of beef cattle on meat quality were evaluated, comparing alfalfa pasture (containing saponins) versus sainfoin pasture (containing tannins). No strong differences (P > 0.05) were found between the two legume diets in all meat characteristics, indicating that sainfoin was similar to alfalfa as a cattle forage. Similar (P > 0.05) low TBA values after 12 d of storage at 2 °C were obtained from both diets, comparable to pasture-fed beef from study 1. This verified the prolonged retail shelf life benefit of forage-fed beef, compared to grain-fed beef.

In study 3 (Chapter 5), lambs fed four different diets, plain/control (P), tanninsrich diet (T), saponins-rich diet (S), or choice of them (C), were evaluated on metabolomics profiles using GC/MS technique. Forty metabolites were detected (30 named and 10 unknown). A principal component analysis (PCA) plot showed a clear separation of P, T, and S diet treatments while the C diet was overlapped with S and P diets, indicating that S or P diets were preferred while the T diet was avoided. In summary, the effects of ruminant diets on meat characteristics depended on the type and concentration of plant secondary compounds (PSC), especially the PSC levels contained in the pastures.

Comments

This work made publicly available electronically on September 20, 2012.

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