3.1 Growth of Pigs - T3 Flashcards
What is the growth cycle of pigs used in production?
Farrowing - birth - wk 3 @ 1.5-7 kg
Nursery - wk 3-9 @ 7-30 kg
Grow - wk 9-16 @ 30-70 kg
Finish - wk 16-24 @ 70-120 kg
What is the shape of the typical growth curve? What is feed efficiency? What does the curve mean for feed efficiency?
- Sigmoid curve
- kg of growth/kg of FI
- FE decreases as animal grows
What are the 5 body components of pigs? What are the main chemical components of swine parts? Which body components are more relevant for swine production?
- Muscle 44%
- 70% water, 20% protein, 8% fat - Fat 18%
- fat - Visceral organs 16%
- water, <20% protein, >8% fat
- heart, lungs, guts
- high energy expenditure and protein turnover - Bones 8%
- minerals - Skin 4%
How does chemical body composition change with age (aka to the end of nursery)?
Water decreases linearly to 25kg
Protein decreases at 7kg
Fat increases at 7kg then decreases at 25kg
- very little fat reserves at birth
- some fat is used at the end of the nursery phase to support protein deposition
Ash stays the same
At what point does FE decrease? Where would you expect this point to be in leaner genotypes?
Linear increase in water, protein, lipid, ash
- point at where lipid deposition happens at higher rate than protein deposition is when FE decreases bc now depositing fat instead of muscle
- would expect this point at a higher bw in leaner genotypes bc pigs will have a higher ability to deposit more protein
What is lean? What is viscera?
Lean = protein and water
Viscera = organs
*lean, fat, and viscera all have a linear increase as pigs grow
What happens with increases in BW in terms of changes in physical and chemical composition?
- Linear increase in lean, bone, skin, viscera -> water, protein, ash
- Fat accretion increases at an accelerated rate as pigs grow
- Lean increases faster than skin, bone and viscera
What happens to dressing percentage as pigs grow?
Increases bc they deposit more protein
= carcass wt (wt w/o viscera)/ live wt
What happens to leaness and fat accumulation as pigs grow? What happens to feed efficiency?
Proportional decrease in leanness (still accumulating more lean tissue but at a lesser rate than fat accumulation)
Feed efficiency decreases
What factors affect body composition?
- Age
- Genotype
- Sex
- Diet
How does body composition vary with genotype?
Different genotypes will have different accumulations of lean and fat
- might have the same BW but will have different chemical body compositions
- lean genotype: higher proportion of water and protein which are the main components of muscle
- fat genotype: almost double the amount of fat compared to the lean genotype
What are expected differences in body composition between boars, gilts and barrows?
Lean
- boar > gilt > barrow
Fat
- boar < gilt < barrow
Viscera
- boar < gilt < barrow
- higher feed intake = more developed gut = greater viscera
Considering the differences in body composition between boars, gilts and barrows:
1. What are the implications for feed efficiency?
2. Who has the highest dressing percentage?
3. Which one would be best for pork production? Why?
- Boars have greatest FE, barrows smallest FE
- Boars have greatest DP
- Boars would be but boar taint is an issue. So gilts are best for pork production!
What is boar taint?
Boars produce androstenone and skatole which have an unpleasant flavour. This is why we DON’T raise boars for pork production
Around 70kg what happens to barrows in comparison to gilts?
Barrows start to:
- deposit more fat; protein deposition rate decreases below gilts
- more viscera
- higher FI
- lower DP
How can diet affect body composition?
- Fiber
- high fiber diet = increase viscera = reduced DP - AA
- increased lys (limiting AA) = increased DP
- can stimulate higher protein deposition by providing more lys; achievable in research but not economically feasible for industry - Feed additives
- can increase rate of protein deposition
- DP increases
Maximum protein deposition
- showing protein deposition (PD) in g/day in relationship to energy intake
- when animals young, linear increase in PD with increased energy intake (so as the animals eat more, they deposit more protein) but only until they reach the point of MAX PROTEIN DEPOSITION
- At the point of maximum protein deposition, it doesn’t matter if you provide them with more energy, the protein depositon will not increase bc they have reached their max potential to deposit protein
- 1st phase is energy dependent; as you prove more energy pigs will deposit more lean tissue
- 2nd phase energy independent; you can feed as much energy as you want and pigs will not deposit more lean
When do modern/lean genotypes reach PDmax?
~100 kg BW
- important to know bc not economically feasible to continue feeding pigs once they reach this bw bc we aren’t getting anything more in return for feeding them; if we feed past this point we are looking for a bit of fat deposition to increase carcass quality
What does protein deposition depend on?
Energy intake until PDmax is reached
- after PDmax is reached, increased energy intake does not lead to increased protein deposition
- pigs have a limited capacity for protein growth
What factors affect protein deposition?
- Sex
- higher protein deposition in gilts vs barrows - Age/BW
- protein deposition increases linearly up to ~90-100kg BW, decreases after that - Genotype
- lean genotypes will have a higher PDmax than fat genotypes
How do barrows and boars differ in protein growth?
- reach PDmax around same amount of DE intake
- however, boars will have deposited more protein at this point
3 things to know about minimum lipid deposition
- ALWAYS occurs, even when energy intake limits growth
- Associated with physiological needs
- Inter- and intramuscular fat
- Suspension and protection of organs (visceral fat)
- Minimum energy reserves - Differs btw genotypes and sex
** There is a certain amount of lipid that MUST be deposited with protein
What is excess lipid deposition?
When energy intake exceeds requirements for protein and associated lipid deposition the excess energy is stored as fat
- fat is an energy sink -> mostly back fat
- if animal is restricted in energy, it can mobilize fat
Protein and lipid deposition
- Lipid deposition increases at a lower rate compared to protein deposition
- BUT once PDmax is reached, lipid deposition rate INCREASES; important for determining when to send the animals to slaughter
