Growth and Development – Composition • Function of genotype and environment • Cattle have 30 pairs of chromosomes • Sex determines the development and function of the organs and glands Example: • Glands produce hormones which cause certain things to occur in the body – some seen and others unseen Examples:
Growth and Development • Frame size is a convenient way of • describing skeletal size within age of cattle and under normal feeding • Frame size • related to the live weight at which a feeder animal will reach a constant level of fatness • Basis for management decisions
market puberty Wt. Time Growth Curve(postnatal) 4 3 2 1. Prenatal 2. Rapid Growth 3. Fat deposit begins 4. Fat 1 Johnson, 1997
Growth and Development – Composition • Results: 1. Later maturity of large framed cattle Period 1 – no difference between types for ADG and F/G Period 2 – small framed cattle gained slower and were less efficient Period 3 – large framed cattle became less efficient 2. Large type cattle had higher DFI and ADG (P < 0.01) • F/G over total feeding period nearly the same
Growth and Development – Composition • Results: 3. Implants improved ADG (P < 0.01); 44 lb. in large and 70 lb in small framed cattle • F/G was improved + 13.3% in small type cattle, but no difference in large type cattle
Growth and Development – Composition • Results: 4. Large frame cattle had less BF and larger LEA; when adjusted for carcass weight, small type had larger LEA (P < 0.01) 5. Small framed cattle appear to respond more to implants than large framed cattle
Growth and Development – Composition • Endocrinology – Interrelationships of small, medium and large frame cattle and estradiol implants Study: Assumptions: 1. 2.
Growth and Development – Composition • Results: 1. Small frame, earlier maturing cattle, had higher concentrations of insulin (P < 0.05) and lower concentrations of GH 2. Large frame, later maturing cattle, had higher concentrations of GH (P < 0.10) and lower concentrations of insulin 3. Within each cattle type, implanted cattle had higher concentrations of GH
Growth and Development – Composition • Results: 4. Thus, higher insulin concentrations in small, early maturity types of cattle may explain earlier fat deposition Whereas, the greater concentrations of GH in large, later maturing types of cattle may account for the greater growth rate and later fat deposition
Fat distribution in carcass • Commonly suggested order of fat depots • 1. Abdominal, 2. Intermuscular. 3. Subcutaneous, 4. Intramuscular • Fat deposited greater rate than muscle later in life such that the % of intramuscular fat, is late maturing • Rate of fat accretion in intramuscular fat is not late maturing
Fat distribution in carcass 1. Internal (KPH) = 2. Subcutaneous (Back Fat)= 2. Intermuscular= 3. Intramuscular (Marbling)=
Sex hormones • The distribution of fat within beef carcasses is be similar for both sexes • Bulls generally produce leaner carcasses than steers • the deposition of fat tends to occur at a lighter weight in heifers than in steers, and at a lighter weight in steers than in bulls.