Thirty-nine mature cows were divided into three condition groups on the basis of their subcutaneous fat thickness as determined by real-time ultrasound. A representative animal from each group was measured and slaughtered. The remaining cows with each group were stratified evenly into two groups with one group fed to gain weight and the other to lose weight. Several ultrasound and other live measures were taken every 4 wk and two animals per subgroup were randomly slaughtered. Carcass data were collected and one side of each carcass was boned, ground, mixed, and subsampled for fat and protein determination. Four regression equations were generated to predict percentage of fat (FAT), percentage of protein (PROT), total fat (TOTFAT), total protein (TOTPROT), total calories (CAL), CAL per live weight (CAL/WT), yield grade (YG), and marbling (MARB). The first equation used all live measures (SUB), the second equation used only objective live measures (OBJ), the third equation incorporated traditional live measures (EAS), and the fourth equation used only carcass data (CAR). Adjusted R-squares of the most appropriate equation using the SUB, OBJ, EAS, and CAR measurements were .82, .73, .82, and .82 for FAT; .82, .57, .61, and .66 for PROT; .89, .87, .86, and .85 for TOTFAT; .95, .95, .93, and .74 for TOTPROT; .93, .92, .91, and .90 for CAL; .83, .78, .83, and .82 for CAL/WT; .86, .86, .78, and .93 for YG; and .75, .70, .74, and .74 for MARB, respectively. It seems that condition score or ultrasound with other objective live measures is as accurate in predicting cow composition as carcass measures.

The continued decline in the availability of water from the Ogallala Aquifer in the Texas Panhandle has led to an increased interest in conservation policies designed to extend the life of the aquifer and sustain rural economies. Four counties were chosen for evaluation. This study evaluates the effectiveness of five policies in terms of changes in the saturated thickness, crop mix, water How to cite this paper:

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We evaluated the accuracy of acid insoluble ash (AIA) as a digestibility marker in feedlot cattle diets containing corn-milling byproducts and examined the effect of fecal sampling frequency on digestibility estimates. Steers (n = 6) were used in a crossover split-plot design where 3 steers per period were assigned to 1 of 2 diets [receiving (REC) containing 19% roughage and 38% Sweet Bran™ or finishing (FIN) containing 8% roughage and 20% Sweet Bran] typical of those used in the beef feedlot industry. Steers were limit fed at 2.0% of initial body weight. After a 21-d adaptation period, steers were housed in metabolism crates for 7 d of total collection (TC) of feed and feces and simultaneous collection of fresh manure grab samples twice daily to calculate nutrient digestibility from AIA. Grab samples were then averaged to represent 7 (7dAIA), 5 (5dAIA), 3 (3dAIA) and 1 (1dAIA) days of the collection period. No interactions (P ≥ 0.13) were observed for DM, OM or NDF digestibility between diet and method of estimating digestibility. Digestibility of DM and OM were greater (P < 0.01) for FIN than for REC, and NDF digestibility was less (P < 0.01) for FIN than REC. Both DM and OM digestibility were greater (P < 0.01) for AIA estimates than for TC; however, estimates with 7dAIA were less than 3dAIA and 1dAIA, but not different from 5dAIA. Similarly, NDF digestibility was greater (P < 0.01) for all AIA estimates than for TC, but 7dAIA and 5dAIA were less than 1dAIA and not different from 3dAIA. A treatment × method interaction (P = 0.02) occurred for ADF digestibility. These data suggest that AIA over-estimated digestibility of beef feedlot diets containing corn-milling byproducts, but accuracy improved with greater grab sampling frequency.

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