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 systems  Nervous, circulatory, respiratory, digestive, and reproductive  Skeletal, muscle, adipose

NUTRIENT PARTITIONING Adipose tissues  Mesenteric  Perirenal  Subcutaneous 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 and 11.2  Ex. 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 deposition  Yet, has little effect on muscle accretion  Table 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 value  Reference to protein quality Even though energy is sufficient, protein is essential for proper growth Tables 11.8,11.9, 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