The effect of three different growth rates on the chemical composition of the dressed carcass of cattle and the relationships between chemical and dissected components

Abstract

This paper describes the chemical composition of dressed carcasses of Angus steers and relationships between chemical and dissected components of these carcasses. These cattle were grown from 300 to 440 kg at three different rates. The rates were: High (H, 0-8 kg/day), Low (L, 0-4 kg/day) and High-Maintenance (HM, 0-8 kg/day followed by a period during which body weight was maintained constant).There were no significant differences between treatments in the regression equations for weight of water, protein or chemical fat against left side weight (half carcass). However, weight of ash was significantly greater in the HM group than in the H group. These results are similar to those obtained with dissection data on the right side of the same carcasses.There were no significant differences between treatments for regression equations predicting dissected composition from chemical composition. The common regressions for each component are as follows:log y (total side muscle) = 0-282 + 1-061 log x (protein) (S v §x 3 %), (i) log y (total side bone) = 1-055 + 0-836 log x (ash) (£"." 6 %) (ii) log y (total side fat) = -0-380 + 1-076 log x (chemical fat) (S vx 4%),where all values of x and y are in grams. Equations (i) and (ii) were used to predict the dissected composition of Angus steers from another experiment in which one group of cattle lost weight. Equation (i) gave useful predictions but equation (ii) did not.

Physical and chemical components of the empty body during compensatory growth in beef steers.

“…respectively, whereas in the carcass, fat was reduced by only 20% and protein actually increased 10% (TabIe 8). Murray et aL (1975Murray et aL ( , 1977 also demonstrated a differential response of carcass and noncarcass tissue to plane of nutrition. They examined the chemical composition of the carcass (Murray et al, 1975) and dissected offal compents (Murray et al, 1977) in growing A n g u s steers placed on either a high (.8 kgld) or low (.4 kg/d) plane of nutrition.…”

“…Murray et aL (1975Murray et aL ( , 1977 also demonstrated a differential response of carcass and noncarcass tissue to plane of nutrition. They examined the chemical composition of the carcass (Murray et al, 1975) and dissected offal compents (Murray et al, 1977) in growing A n g u s steers placed on either a high (.8 kgld) or low (.4 kg/d) plane of nutrition. Chemical composition of carcass tissue was unaffected by plane of nutrition, yet the weight of fat associated with abdominal organs was reduced by 21%, whereas the weight of the total fat-trimmed gastrointestinal tract was reduced by only 12% in cattle on the low plane of nutrition.…”

“…The existence of a differential response to nutritional plane by carcass and noncarcass tissues would perhaps explain some of the inconsistencies in the literature concerning nutritional modification of body composition at a constant weight. In several studies that found composition to be independent of plane of nutrition, only carcass compositional measurements were made (Murray et al, 1975) or carcassdensity measurements were used to estimate empty-body composition (Old and Garrett, 1987), thus nutritional effects on noncarcass composition may have been overlooked. This would not, however, explain the experiments of Reid et al (1968) and Jesse et al (1 976), who directly measured empty-body composition and found no differences due to plane of nutrition.…”

“…Although several studies have found composition of the carcass (Murray et al, 1975) and empty body (Jesse et al. 1976) to be independent of nutritional influences at a constant BW, it is now well established that increases in dietary energy intake can enhance the proportion of fat deposited in the carcass (Keane et al, 1990) or empty body (Forth et al, 1980).…”

Developing breeding objectives for beef cattle production 1. A bio-economic simulation model

“…In the present model, the following empirical equations reported by Murray et al (1975) are used to estimate lean (LEAN,) and fat (FAT t ) tissues from chemical protein and fat components as log 10 (LE AN,) = 0-282 + 1-061 log ]0 (CWP t XCTV,/100)(g) Berg and Butterfield (1976) mentioned that lean tissue contains some chemical fat and fat tissue is not all chemical fat but has protein and water as well.…”