- Genetic makeup and breed influence growth rates and fat content in meat animals through differences in cell division, gestation periods, and genes that control traits like dwarfism. - Environmental conditions like temperature, humidity, and climate affect growth and development, with some breeds adapted to extreme hot or cold. Plane and quality of nutrition also differentially impact growth of tissues and organs. - Interactions with other species, soil fertility, plant nutrition, and trace mineral deficiencies or excesses in pastures can further influence animal growth and health.

1. FACTORS AFFECTING THE
GROWTH AND DEVELOPMENT
OF MEAT ANIMALS

2. Genetic Makeup/Breed
• The genetic makeup of animals influences the growth in
earlier embryonic life as differences exist in the rate of cell
division of their embryo
• The breed of animals has significant impact on different
parameters of commercial importance and one main among
them is degree of fatness
• The fatness level in carcasses varies greatly in animals having
same weight or age but different breed
• e.g. sheep breed Suffolk and Southdown slaughter at same
weight (20 kg) have 32.9 and 38.5% fat respectively in their
carcass

3. • The physiological age at birth depends upon how a great part
of growth is spent in uterus
• The birth weight of young ones is influence by age, size and
nutritional status of mother
• The length of gestation period (5 months for sheep and 9
months for cattle), sex and number of young one born also
have impact on the birth weight
• The young mothers generally have low birth weight offspring
compared to mature females and similarly the birth weight of
offspring is greater from larger animal compared to smaller
mothers
• The recessive genes in cattle control certain growth features
like dwarfism

4. • The responsible gene controls the longitudinal bone growth
and vertebral development in lumbar region
• A major gene having significant role in meat animal growth
and quality of their flesh is the “Barooroola gene (F)”
• The selection of animals for improved performance can be
done based on the heritable characters like birth weight,
growth from birth to weaning, post-weaning growth and feed
conversion efficiency (Table 1.4)
• The differences in requirement of essential nutrients like
vitamin D and pantothenic acid by domestic animal are
genetically controlled
• One of the important aspects of gene variability is the
determination of the endocrine control balance of growth
and development

5. • The genetic compatibility with environment affects the
apparent variation in growth
• The lambs with higher rate of thyroid secretion have rapid
growth compared to those with intrinsically low rate of
thyroid secretion
• The advances in genetics and breeding have made it possible
to alter the specific features of muscles
Environmental conditions
• The regulation of heat in farm animals is the subject of wide
economic importance
• The body temperature is maintained at constant level by
cattle and sheep required for optimum biological activity

6. • The living organism can tolerate normally an environmental
temperature lying in the range of 0-40oC but some animal are
habitual to extreme conditions like below freezing or above
50oC
• The short periods of even more sever conditions are
compatible with polar animal survival as they can tolerate -
80oC by maintaining their body temperatures
• The development of animals is extended in the environment
of low temperature while high temperatures retard the
development of un-adapted livestock
• The uniform low or high temperature has lesser impact on the
metabolism of animals but variable temperatures have greater
influence

7. • An animal can tolerate prolong exposure to heat or cold
waves by hormonal changes to these two stress conditions
• The animals having large bodies can better withstand the low
temperature of cold environment because of low surface to
volume ratio while small animals due to high surface to
volume ratio can efficiently dissipate heat in warm
environment
• The yak among cattle has heavy and compact body with short
neck and legs covered with thick long hair inhabitant to the
regions of cold environment and rarefied atmosphere
• The temperate regions cattle have somewhat less compact
body than cold environment cattle

8. • The cattle of tropical regions have angular frame, long legs
and neck, large dewlap to increase surface to volume ratio
and have coat of short hair
• Furthermore, the tropical cattle have lightly colored coat as
dark coloration absorb more radiant energy
• The temperate region animals will have higher body
temperature than tropical animals under conditions of heat
stress
• The heat disposal mechanisms are less efficient in temperate
region animals and they maintain their body temperature
through behavioral changes like voluntary restriction of feed
intake, seeking shade and inactivity

9. • Feed and Nutrition
• The development, dominance and survival of all living
organism are determined by the most important factor of
finding enough foods of right kinds
• The major proportion of life time of all cold blooded
animals and most of warm blooded animals is spent doing
nothing
• They spent greater part of their life in eating when they start
doing
• The feed and nutrition factors affecting the growth and
development of animals are plan and quality of nutrition,
interspecies interaction, plant nutrition and micronutrients

10. • Feeding plan and nutritional quality
• The feeding plan and nutritional quality of feed at any stage
of animal life alter the growth of animal in general and also
affect the development of different regions, tissues and
organs differentially
• The animal of same breed and weight will vary in form and
composition if they have different feeding plans and nutrients
quality
• The brain and nervous system have priority over bone,
muscles and fat in development order in relation to plan of
nutrition
• The tissues and body regions are utilized in reverse order of
their maturity for energy and protein supply to body under
conditions of low nutrients diets

11. • Fats are utilized first under these conditions followed by
proteins and bones and these are first depleted from those
regions latest to maturity
• The high plan of nutrition lead to faster growth rate causing
earlier onset of growth’s fattening phase
• The fastest growing animals may become leaner by increasing
the protein/energy ratios and at very high ratio the growth
rate can be diminished
• Male animals require diets having high protein/energy ratio
than female and this requirement can causes the difference in
carcass composition between two sexes fed on same
protein/energy ratio diet

12. • The rumen microflora substantially determined the intake to
ruminant tissues so they have quite different relationship with
quality of diet
• Ammonia derived from deamination of soluble protein
entering the rumen is the major nitrogen source for microbial
synthesis and activity of the micro-flora and is determined by
amount of energy available to animals
• The ingested protein through high protein diet may be
excreted as non-incorporated ammonia
• The non-protein nitrogen of low protein fed diets can be
converted to proteins and ruminant may vary in their protein
requirements depending upon their rumen microflora and
these amino acids can be supplemented in the feed of
ruminants

13. Plane and quality of nutrition
• Differences in the plane of nutrition at any age from the late
foetal stage of maturity not only alter growth generally but
also affect the different regions, the different tissues and the
various organs differentially
• Thus animals on different planes of nutrition, even if they
are of the same breed and weight, will differ greatly in form
and composition
• The relationship of the ruminant to the quality of the diet is
different since the intake into the tissues is substantially
determined by the rumen microflora
Interaction with other species
• In general, there are definite upper and lower limits to the
size of animal which a carnivore can utilize

15. • The most serious effects of other animal species on
domestic stock, however, arise indirectly when the rate of
natural increase of small species
• The rabbit, when introduced into Australia, increased at a
phenomenal rate and denuded vast areas of the vegetation
upon which stock had previously subsisted
• Some species, of course, are beneficial to domestic stock
• Ruminants largely depend on the micro-organisms in their
digestive tract to break down the cellulose of plant foods
• They are thus equipped to make use of poor-quality diets

16. Soils and plant growth
• Although some animals are carnivores they are ultimately
as dependent on plant life for their sustenance as the
herbivores
• Food represents stored energy utilizable by animals and it
can be released at a rate determined by metabolic needs
• The major ultimate source of energy is sunlight; and it is
only in the Plant Kingdom that a mechanism exists for its
conversion into a stored form
• The fertility of soils depends not only on the chemical
nature of the rocks from which they have been formed but
also on particle size

17. • The latter determines how much moisture soils will hold
and for how long, and the availability of its nutrients to
plants
• Soils and climate affect plant growth qualitatively as well
as quantitatively
• The grasses of low nitrogen content develop on acid soils
• The nitrogen content of grasses and legumes diminishes on
prolonged exposure to high temperatures
• The digestibility of plants may be altered artificially
• The increasing use of plant growth substances, such as
gibberellic acid, which increases the internode distance in
grasses, tends to lower the nitrogen content of grasses and
to decrease digestibility

18. Trace materials in soils and pastures
• It is being increasingly recognized that many animal
ailments can be explained on the basis of dietary
deficiencies or excesses of biologically potent materials
which are present only in minute quantities in soils and
pastures
• A deficiency of cobalt in the soils of certain areas was the
cause of various wasting and nervous diseases in cattle and
sheep which had been known for many years by settlers
• Animals, after grazing for several months, would lose their
appetite and finally die in the midst of rich pasture
• Copper deficiency inhibits the action of various amine
oxidases, and, thereby, the structural integrity of elastin and
collagen in connective tissues

19. • An excess of molybdenum in the soil is said to enhance
copper deficiency in animals
• An excess of selenium interferes with metabolism by
displacing sulphur from the essential –SH groups of
dehydrogenase enzymes
• An excess of potassium, by interfering with the
accumulation of sodium, alters the ionic balance of body
fluids and may cause hypersensitivity to histamine
• Conditions such as grass tetany and milk fever, wherein
the magnesium or calcium content of blood serum is
especially low

20. • Toxicity in stock may also arise by the excess ingestion of
trace organic substances
• Some pastures, may contain sufficient isoflavones or
flavones of oestrogenic potency to affect the reproductive
activity of grazing ewes