NUTRITIONAL REGULATION OF GROWTH

ANSC 590 ANIMAL GROWTH AND DEVELOPMENT

NUTRIENT PARTITIONING

Plane of nutrition Homeostasis Maintenance Growth Production

Repro, milk, finishing, etc.

NUTRIENT PARTITIONING

Dietary energy Energy density Order of priority for energy on

physiological systemsNervous, circulatory, respiratory, digestive,

and reproductiveSkeletal, muscle, adipose

NUTRIENT PARTITIONING

Adipose tissuesMesentericPerirenalSubcutaneous or intermuscular Intramuscular or marbling

NUTRIENT PARTITIONING

Homeorhesis – longterm coordination of nutrient partitioning

Positive energy balance When food is plentiful to take care of maintenance, growth and

fattening Feed efficiency is in favor of greater muscle deposition Efficiency is in favor of lactation over dry cow

Negative energy balance – when animals don’t have adequate energy for maintenance and production needs Loss of weight and reduced performance

Undernutrition

Pre-natal: fetal concentration of nutrients are greater than that of maternal plasma

Low birth weights are often due to undernourishment during fetal development

Table 11. 1 and 11.2Ex. Runt piglets

Undernutrition

Runt pigs- less weight with smaller vital organs, less DNA in skeletal muscle with less muscle fibers. Thus, they grow slower, produce less muscle and deposit fat faster or sooner and ultimately less feed:gain ratios

Postnatal

Increased metabolic activity at the time of birth for maintaining body temp

Glycogen and white adipose fat tissues are called upon for energy

Colostrum is essential for energy and for immune response

Milk production plays an integral role in plane of nutrition versus growth

Postnatal

Weaning- ultimate stress and nutrient change

Creep feeding Ad libitum versus limited feed

Limited provides less fat intake and depositionYet, has little effect on muscle accretionTable 11.5

Compensatory Growth

Compensatory growth after a period of nutrient restriction

If fed a high level of nutrition late in production after being deprived of nutrients will deposit more fat

If fed a low level of nutrition late in production, then they will produce leaner carcasses

Figure 11.9 and table 11.6 & 7

Dietary Protein

Biological valueReference to protein quality

Even though energy is sufficient, protein is essential for proper growth

Tables 11.8,11.9, 11.10 Yet, excess protein is metabolized for

energy and/or excreted

Dietary Protein

Ruminants utilize microbial protein to satisfy part of protein requirements

Amino acids synthesized to ammonia, CO2, and VFA’s (these are required for microbial protein growth)- degradation

Nitrogen is the key for microbial protein satisfaction (NPN can be a source)

Dietary Protein

Bypass protein – protein that escapes the rumen

Degradable versus non-degradable prot. Increased muscle accretion requires more

protein

Dietary Protein

Non-ruminants Essential versus non-essential amino acids Limiting amino acids in basal diets Amino acid balance/supplementation Feed intake decreases with amino acid deficiencies Catabolism of unused a.a.’s require energy which

reduces efficiency Table 11.11

Dietary Energy

Requirements increase along with body size Composition of wt. gain dictates total dietary

energy requirements and f:g ratios Supplemental fats are added to give more

nutrient density Non ruminants will assimilate fats to be similar

type as to the type in the diet Soft and oily fat due to melting point and type of fats

in the feed

Feed Additives

Ionophores- carboxylic polyether ionophores to increase growth efficiency in cattle

Coccidiostats Antibiotics

Subtherapeutic levels- changes microbes to improve efficiency

Regulation of Protein Accretion

Alters rates of protein synthesis and degradation Dependent upon nutritional regime versus plane

of nutrition required Synthesis and degradation occurs at varying

rates Synthesis is more sensitive than degradation Amino acid and insulin supplies are important in

mediating muscle protein metabolism

Regulation of Protein Accretion

Protein accretion rates in liver appear to be regulated by nutritional status through changes in protein degradation rates rather than through changes in synthesis rates