The digestible energy, metabolizable energy, and net energy content of dietary fat sources in thirteen- and fifty-kilogram pigs

Abstract

The objective was to determine the energy concentration of a diverse array of dietary fat sources and, from these data, develop regression equations that explain differences based on chemical composition. A total of 120 Genetiporc 6.0 × Genetiporc F25 (PIC, Inc., Hendersonville, TN) individually housed barrows were studied for 56 d. These barrows (initial BW of 9.9 ± 0.6 kg) were randomly allotted to 1 of 15 dietary treatments. Each experimental diet included 95% of a corn-soybean meal basal diet plus 5% either corn starch or 1 of 14 dietary fat sources. The 14 dietary fat sources (animal-vegetable blend, canola oil, choice white grease source A, choice white grease source B, coconut oil, corn oil source A, corn oil source B, fish oil, flaxseed oil, palm oil, poultry fat, soybean oil source A, soybean oil source B, and tallow) were selected to provide a diverse and robust range of unsaturated fatty acid:SFA ratios (U:S). Pigs were limit-fed experimental diets from d 0 to 10 and from d 46 to 56, providing a 7-d adaption for fecal collection on d 7 to 10 (13 kg BW) and d 53 to 56 (50 kg BW). At 13 kg BW, the average energy content of the 14 sources was 8.42 Mcal DE/kg, 8.26 Mcal ME/kg, and 7.27 Mcal NE/kg. At 50 kg BW, the average energy content was 8.45 Mcal DE/kg, 8.28 Mcal ME/kg, and 7.29 Mcal NE/kg. At 13 kg BW, the variation of dietary fat DE content was explained by DE (Mcal/kg) = 9.363 + [0.097 × (FFA, %)] - [0.016 × omega-6:omega-3 fatty acids ratio] - [1.240 × (arachidic acid, %)] - [5.054 × (insoluble impurities, %)] + [0.014 × (palmitic acid, %)] ( = 0.008, = 0.82). At 50 kg BW, the variation of dietary fat DE content was explained by DE (Mcal/kg) = 8.357 + [0.189 × U:S] - [0.195 × (FFA, %)] - [6.768 × (behenic acid, %)] + [0.024 × (PUFA, %)] ( = 0.002, = 0.81). In summary, the chemical composition of dietary fat explained a large degree of the variation observed in the energy content of dietary fat sources at both 13 and 50 kg BW.

Determination of net energy content of dietary lipids fed to growing pigs using indirect calorimetry1

“…The ME and NE estimates in NRC (2012) assumed that the conversion ratio of DE to NE is the same across all fat sources. However, it has been emphasized that more studies are required to determine if these relationships are correct and can be broadly applied to different fat sources (Kellner and Patience, 2017). Across the 5 dietary fat sources tested in our study, the DE to GE ratio varied from 91% to 98%, while the ME to DE ratio (averaged 99%) and the NE to ME ratio (averaged 90%) were relatively stable among the 5 lipid sources.…”

“…Accurate assessment of the energy values to dietary fat sources not only allows pork producers to judge the financial value of supplemental lipids but also supports differentiation of available fat sources (Van Heugten et al, 2015;Kellner and Patience, 2017). Kerr et al (2015) also emphasized the need for accurate determination of the NE content of dietary lipids, because NE systems may allow for a more accurate prediction of the energy value of dietary lipids than DE and ME systems .…”

Measures Matter—Determining the True Nutri-Physiological Value of Feed Ingredients for Swine

“…Third, energy prediction equations derived from various lipids with diverse fatty acid profiles are assumed to provide reasonably accurate predictions when compared with energy values directly determined from in vivo experiments. However, results from Kellner and Patience [141] and Kerr et al [144] have shown that this often does not occur. There may be at least two explanations for this.…”

“…Fortunately, there continues to be considerable interest in developing and using robust equations to accurately estimate DE, ME, and NE content of lipids based on chemical composition (Table 8). However, although several equations have been developed for swine, their accuracy in predicting in vivo determined DE content is generally poor [141,144,150]. Kerr et al [150] determined the DE content of five sources of distillers corn oil (DCO) containing 0.04% to 93.8% FFA, and compared these values with predicted DE content using equations by Wiseman et al [151], which included FFA content and UFA to saturated fatty acid (SFA) ratio as the main variables (Table 9).…”

“…The predicted DE content of these lipids averaged about 300 kcal/kg more than the in vivo determined DE content for all DCO sources except for the source containing 93.8% FFA, which was predicted to have 1100 kcal/kg more than was actually determined in vivo (Table 9). Kellner and Patience [141] determined the DE content of 14 different lipids, including two sources each of choice white grease, corn oil, and soybean oil fed to 13 kg and 50 kg pigs, and compared these in vivo values with predicted values using equations from Powles et al [129] and equations derived from chemical composition of lipids evaluated in their study (Table 10). Their results showed that the differences in chemical composition among lipid sources resulted in different energy values depending on the body weight of pigs.…”