Growth and Development
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growth
increase in body weight until maturity is reached increase in animal tissue: muscle, fat, and bone measures of growth include: weight/unit time (WDT); height/unit time; average daily grain; days to 260 (swine); weaning weight; yearling weight
true growth
only growth that involves an increase in structural tissues- excludes fat as storage tissue
development
directive coordination of all diverse processes until maturity is reached involves growth, cellular differentiation and changes in body shape controlled by genetic make-up of the animal
maturity
state of being fully grown or developed in animal production, we often refer to sexual and compositional maturity
physiological age
refers to stages (landmarks) of development as the animal grows from conception to maturity -puberty
chronological age
refers to the animal’s age in terms of units of time
hyperplasia
an increase in the number of cells
hypertrophy
as increase in cell size
efficiency of growth
units of input per unit output cattle: 7:1 sheep: 4-6:1 swine: 3:1/2:1 broilers: 2:1 fish: 1.1/1 in animal production, how much feed put in (lbs or kgs) per unit gain (lbs or kgs)
normal growth curve
sigmoidal
tissues with the greatest importance to life are first
A. highest priority: brain and heart B. middle priority C. low middle priority D. lowest priority
tissue development
nervous, bone, then muscle, then fat wait to finish until fat has time to develop: rib and loin are last to develop
order of fat deposition
perinephric/internal/ KPH (kidney, pelvic, and heart fat)/kidney-pelvic fat/leaf fat -fat around the organs intermuscular fat- seam fat, between large muscle groups subcutaneous fat -external, back fat intramuscular fat- marbling, flank streaking
diversity of growth
heredity dependent breeds develop differently, breed type influences mature size phenotypic variation: outward visible expression influenced by heredity and environment
measures of growth in livestock
beef cattle birth weight, weaning weight, yearling weight, feedlot ADG, mature weight sheep birth weight, 60 day weight, 90 day weight, yearling weight, feedlot ADG, mature weight swine birth weight, weaning weight, days to 260lbs horses growth is generally measured in hands by a certain age poultry days to slaughter weight
genetic effects on growth and development
growth is a moderately to highly hereditable trait