Efficiency of Energy Utilisation by Finishing Pigs Selected for Potential Growth Rate23 October 2013
Pigs separated into slow, average or fast potential growth rates, by determining their growth rates in the nursery has comparable growth rates and feed intake.
Feeding pigs specific diets based on potential growth rate as determined by growth rate in the nursery may decrease variability in grow-out and finishing.
In this study, however, pigs separated into slow, average or fast potential growth rates by determining growth rate in the nursery had comparable growth rates, feed intake and rates of protein and lipid deposition in late finishing.
The normal variability in growth rate that exists within a group of pigs causes inefficiencies in nutrient utilisation and contributes to variation in carcass composition.
Managing this variability is a significant challenge for the pork industry. Prairie Swine Centre researchers have conducted a series of experiments designed to develop cost-effective feeding regimes which minimise the negative effects of variability on the producer’s bottom line.
The specific objective of this experiment is to characterise the utilisation of energy by pigs of differing potential growth rate (PGR).
Materials and Methods
This experiment used a total of 120 finishing (90 to 120kg bodyweight) barrows. Twenty-four pigs were assigned to an initial slaughter group (ISG) and 96 pigs were assigned to one of 12 treatments (n=8 pigs per treatment).
The treatments were arranged as a 3×2×2 factorial and consisted of three potential growth rates (PGR; slow, average or fast), two dietary energy concentrations (EC; 2.18 or 2.40Mcal Net Energy per kg) and two levels of feed intake (FL; 85 or 100 per cent of ad libitum intake).
Barrows were identified at nursery exit as having a slow, average or fast PGR, based on their bodyweight per day of age from birth to nursery exit. When the pigs reached 90kg bodyweight, they were randomly assigned, within PGR, to the EC and FL treatments.
Except for the ISG group, pigs were slaughtered when they reached 120kg bodyweight. Carcasses were ground and analysed for nutrient content. Dietary NE (NECST) was calculated as the sum of the energy retained in the carcass (RE) and fasting heat production (FHP), estimated according to Noblet et al. (2003) as 179kca per kg BW0.60. Dietary Net Energy was estimated based on nutrient content and digestibility using prediction equations from the French National Institute for Agricultural Research (INRA; Sauvant et al., 2004).
Pigs were identified as having either a slow, average or fast PGR based on their bodyweight per day of age from birth to nursery exit.
Previous studies conducted at the Prairie Swine Centre have demonstrated a correlation (r2 ~0.35) between bodyweight at nursery exit and growth rate in the grow-finish barn. Interestingly, in the present study performance, expressed in terms of average daily gain (ADG), average daily feed intake (ADFI) and feed conversion efficiency (FCE) was unaffected by PGR (P>0.05; Table 1).
Pigs receiving the high-energy diet had reduced ADFI (P<0.05), however, ADG was similar across EC treatments. By design, ADFI was greater in pigs fed at 100 per cent of ad libitum than those fed at 85 per cent, which led to an increase in ADG (P<0.05; Table 2).
The efficiencies with which pigs used dietary energy for bodyweight gain and for accretion of protein and lipid in the carcass were unaffected by PGR (Table 3). Pigs fed the low-energy diet were more efficient (g protein deposited per g Mcal intake) in their accretion of carcass protein than pigs fed the high-energy diet (P<0.05).
Although pigs fed at 100 per cent of ad libitum grew faster and took fewer days to reach 120kg than those fed at 85 per cent of ad libitum, the latter were more efficient in their use of dietary energy for bodyweight gain (P<0.05) and for carcass protein accretion (0.50<P< 0.10; Table 3).
Growth performance and the efficiency of energy utilisation for growth and for carcass nutrient accretion in finishing (90 to 120kg) pigs was similar among pigs identified at nursery exit as having a slow, average or fast potential growth rate.
This suggests that segregating pigs at nursery exit based on PGR is not an effective tool to manage variability in the grow-finish herd.
The authors gratefully acknowledge the National Sciences and Engineering Research Council (NSERC) and Cargill Ltd. for funding this study; and Sask Pork, the Manitoba Pork Council, Alberta Pork, Ontario Pork and the Saskatchewan Agriculture and Food Development Fund for strategic funding provided to the Prairie Swine Centre.