Relationship of tissue growth to carcass growth

 What are the three lines?

 What would the curves look like for a smaller mature size animal?

Body composition of Dorset and Suffolk rams

 How does the growth of muscle, fat and bone influence efficiency of growth between two weights?

Animals that gain more fat require more energy because they gain less water:

• About 16 kcal of metabolizable energy are required to gain either a gram or protein or a gram of lipid.
• Muscle is about 70% water, 20% protein, and 10% lipid, so muscle requires about 4.8 kcal (0.3*16) of ME per gram of gain.
• Fat is about 20% water, 10% protein, and 70% lipid, so fat requires about 12.8 kcal (0.8*16) of ME per gram of gain.
• Thus fat tissue requires (12.8/4.8) about 2.7 times more ME per gram of tissue gain than muscle.

 How does the growth of muscle, fat and bone influence efficiency of energy gain between two weights?

• Lipid contains about 9.4 kcal of gross energy (provides about 9 kcal of ME).
• Protein contains about 5.65 kcal of gross energy (provides about 4 kcal of ME due to urinary loss).
• Thus each gram of muscle contains about (0.2*5.65 + 0.1*9.4) 2.07 kcal of gross energy and this energy costs about 4.8 kcal to gain so efficiency of energy gain is (2.07/4.8) 0.43 or 43%.
• Thus each gram of fat contains about (0.10*5.65 + 0.70*9.4) 7.14 kcal of gross energy and this energy costs about 12.8 kcal to gain so efficiency of energy gain in fat tissue is (7.14/12.8) 0.56 or 56%.

 How does the growth of muscle, fat and bone influence speed of growth between two weights?

Animals that gain more muscle are more efficient and consume at least as much feed. Therefore, they grow faster.

 How does the growth of muscle, fat, and bone influence carcass traits at a given carcass weight?

Animals that gain more muscle are leaner at a given carcass weight.