Investigations of energy metabolism in weanling barrows: The interaction of dietary energy concentration and daily feed (energy) intake

¹ Prairie Swine Centre Inc., Saskatoon, SK, Canada S7H 5N9; Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada S7N 5A8
² Prairie Swine Centre Inc., Saskatoon, SK, Canada S7H 5N9

^* To whom correspondence should be addressed. E-mail: john.patience{at}usask.ca.

	Abstract

Much of our understanding of energy metabolism in the pig was derived from studies in which energy supply was controlled through regulated feed intake. In commercial practice, where ad libitum feeding is practiced, dietary energy concentration but not daily feed intake is under producer control. This study evaluated the interactive effects of dietary energy concentration and feeding level (FL) on growth, body composition, and nutrient deposition rates. Individually penned PIC barrows with an initial BW of 9.5 ± 1.0 kg were allotted to 1 of 9 treatments in a 3 x 3 factorial arrangement (n = 9/treatment) plus an initial slaughter group (n = 6) harvested at the start of the trial. Three NE concentrations (low, 2.15; medium, 2.26; and high, 2.37 Mcal NE/kg) and 3 feeding levels (FL: 100%, 80% or 70% of ad libitum access to feed) were investigated. Daily feed allowance for the restricted-fed pigs was adjusted twice per wk on a BW basis until completion of the experiment at 25 ± 1 kg BW. Average daily gain, ADFI and G:F were unaffected by NE (mean = 572 g, 781 g and 0.732 g/g, respectively). Average daily gain and ADFI increased (P < 0.05) with FL but not G:F. Empty body (EB) lipid concentration increased with dietary NE concentration and with FL; a significant (P < 0.01) interaction revelated that EB lipid concentration increased most rapidly as FI increased on the highest energy diet. Empty body lipid concentration was greatest in pigs with ad libitum access to the high NE diet. Empty body protein concentration decreased with increasing NE (P < 0.05) but was not affected by FL. Empty body protein deposition (PD) increased with increasing FL (P < 0.001), but not with NE. Empty body lipid deposition (LD) and LD:PD ratio increased (P < 0.01) in pigs with ad libitum access to the high NE diet. In conclusion, NE did not interact with FL on growth, body protein concentration, or PD, suggesting that conclusions regarding energy utilization obtained from experiments employing restricted feed intake may not easily be applied to pigs fed under ad libitum conditions. The interactive effects of NE and FL on body lipid concentration, LD, and LD:PD ratio indicate that changes in dietary energy concentration alter the composition of gain without necessarily changing overall bodyweight gain. Consequently, the composition of gain is an important outcome in studies on energy utilization.

Key Words: carcass composition, growth, net energy, maintenance energy, nutrient deposition, weaned pigs