Masters Theses

Date of Award

12-1980

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

Gordon W. Davis

Committee Members

W.T. Butts Jr, C.C. Melton, S.L. Melton

Abstract

Part I: Effect of Days on Feed, Carcass Traits and Chemical Measures on Various Muscle to Bone Ratios from Forage and Grain Finished Steers.

A total of 60 (30 Hereford and 30 Angus) steers varying in body type (frame score 1 to 5) were grouped into 10 sextets according to breed, frame score and feeder calf fat thickness. This basic design created five groups of six Angus and five groups of six Hereford steers. Each group of six was similar in predicted days to reach 12 mm of fat thickness. Ten steers, one steer from each sextet, was slaughtered at six serial slaughter points: 0 (all forage), 28, 56, 84, 112, and 140 days on full feed. Following a 48-hour chill period, carcasses (n=60) were ribbed and evaluated for USDA grade factors and various other measures. Following determination of objective measurements, one round from each carcass was dissected. Tissue separation of the wholesale round resulted in determination of the five measures of muscle to bone ratio: total muscle of round to total bone of round (M:B-1 ); total muscle of round plus acceptable fat (1.3 cm) to total bone of round (M:B-2); Biceps femoris (BF) to femur (M:B-3); BF plus semimembranosus (SM) and adductor (AD) to femur (M:B-4); and BF plus SM plus AD to femur (M:B-5).

Data indicated that the effects of days on feed, carcass traits and histological measures on carcass muscling of 60 serial slaughtered Angus and Hereford steers are as follows: (1) five measures of muscle to bone ratio were linearly related (P<.01) to time on feed; (2) that the predicted value of M:B-1 at 140 days was near the maximum value usually observed; (3) among five objective measures of muscle to bone ratio, M:B-3 (BF to femur) and/or M:B-5 (BP + SM + AD + to femur + tibia) provided an acceptable objective index for carcass muscling when dissection time and accuracy were both considered; (4) certain carcass traits (weight, adjusted fat thickness and rib-eye area) and histological measures (percentage white fibers, fiber diameter and fat cell diameter) were significantly related to all measures of muscle to bone ratio and to time on feed; (5) an eight variable multiple regression model consisting of two fixed effects, three carcass traits and three histological measures accounted for approximately 61% of the observed variation in M;B-5; (6) fixed effects (breed and time on feed) carcass traits and histological measures accounted for approximately 49, 42, and 22% of the observed variation in M:B-5, respectively; and (7) for a population sample of serial slaughtered steers, fixed effects (time on feed and breed) explained 16 and 31.8% of the variation in M:B-5 not previously accounted for by carcass traits and histological measures, respectively.

Part II: The Effects of Time on Feed, Carcass Traits, and Chemical Measures on Tenderness and Flavor of Forage- and Grain-Fed Beef.

A total of 60 (30 Angus, 30 Hereford) steer calves varying in body type (frame score 1 to 5) were purchased (October, 1979) from Tennessee Graded Feeder Calf Sales and Auction Markets. The cattle were wintered (October to March) on a low energy hay ration. The small framed steers gained 1.12 Kg per day (123.6 Kg total) on forage, whereas the large framed Angus and Hereford steers gained 1.18 Kg per day (144.5 Kg total) during a 122 day limited grazing period (March to August). Following maximum utilization of forage, the 60 steers were grouped into 10 sextets according to breed, frame score and fat thickness; thus creating five groups of six Hereford steers and five groups of six Angus steers. Each group of six was similar in predicted days to reach 12 mm of subcutaneous fat thickness. Ten steers (one steer from each sextet was slaughtered at six serial slaughter points: all forage, 28, 56, 84, 112, and 140 days on full feed. Data in this study indicated the following: (1) time on feed was related to sensory flavor and tenderness of the loin steaks; (2) sensory flavor of the semimembranosus was related to time on feed, while tenderness was not; (3) among all physical, chemical and histological measures studied. Fragmentation index accounted for the greatest percentage of variation in sensory tenderness; (4) the fatty acids C14:0, C17:0, C16:1 and C18:1 increased whereas C18:0 and C18:3 decreased with time on feed; (5) sensory flavor rating of loin steaks could be predicted using time on feed, carcass traits, histological or chemical measures.

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