Broiler farmers and pig producers already appreciate the fact that their animals do not grow to full genetic potential. This is evidence by the disparity between commercial growth performance records and those achieved under more ideal conditions. So, what can be done to remove these obstacles that limit growth in young animals raised under commercial conditions, and can it be profitable?
Nutrition drives growth
The major drive for growth in young animals is protein deposition to reach maturity, because fat deposition persists beyond maturity. Daily protein deposition responds linearly to increasing intake of a balanced diet until it plateaus at genetic potential. In the linear phase, lipid accretion is limited to amounts essential for normal tissue development, but it accelerates when nutrient supply exceeds requirements for maximal protein growth.
In young pigs and broilers, protein deposition and growth will respond linearly to increasing feed intake because currently gut capacity almost invariably limits voluntary feed intake of typical diets. Hence, super nutrient-dense diets are required to enhance growth in young broilers and pigs. But these are invariably more expensive than typical feeds, and their cost must not outweigh their benefits.
Genetics affects growth
Genotype, of course, affects growth because it defines maximal potential for protein deposition rate under non-limiting conditions. This fact has been fully explored in broilers where specific genetic lines have been developed to meet local market demands.
But, this is not the case in pigs, where considerable work is still required. Indeed, among available pig genotypes, the differences in early growth are small and difficult to detect under commercial conditions, but they do surface as the animals approach market age. Depending on desired final weight, a different genetic combination is required to meet local market demands for carcass leanness and conformation.
Gender plays a role
Gender clearly affects protein deposition (males deposit more protein than females) and feed intake. Males tend to grow faster and more efficiently than females. Although gender affects both the rate and composition of growth, this is more prevalent as animals approach market age. To this end, penning and feeding male and female animals separately always improves their chances of expressing growth performance closer to full genetic potential. But, this is often creates logistics problems that can cost more to resolve than the actual payback of separate-sex feeding.
Immunological stress
Broilers and pigs are continuously exposed to pathogenic and non-pathogenic microorganisms through their interaction with the environment and other animals. Even though disease does not always prevail, chronic exposure to antigens constantly triggers the immune system. This rather needless activation reduces appetite, increases muscle protein degradation, slows down muscle protein synthesis and diverts nutrients to the synthesis of components of the immune system instead of growth. Improving farm biosecurity protocols, animal health and overall hygiene conditions has been shown to lead to higher growth rates and improved feed efficiency.
Management stress
In modern production systems, broilers and pigs are invariably exposed to several stress conditions caused (even by widely accepted as normal) management practices. Differences in ambient temperature, humidity and air velocity can seriously affect growth and feed intake, especially in young animals.
Inappropriate group size, increased stocking density and inadequate pen design may increase stress and reduce growth or access to feed. Frequent handling, disturbing, moving and mixing also increase stress and depress performance. It has been demonstrated that the negative effects of several management stress conditions (high temperature, frequent mixing and increased pen density) can be additive, each further reducing growth performance on its own.
