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Growth Validation of Net Energy Estimates for Soybean Meal and Fat (CWG) Using12 to 30 kg Pigs
This study was conducted to verify that net energy (NE) values for soybean meal (SBM) and fat (CWG) give predictable results. Previous research by Hanor, using the Snyder growth assay (Boyd et al. 2010), confirmed that the NRC (2012) NE estimate for soybean meal (SBM) was reliable, but the estimate for fat (CWG) was at least 6.5% higher than the NRC. This study involved incremental changes in SBM, CWG and corn, while maintaining constant NE across diets. A growth assay was conducted with 12.7 kg (+ .3) pigs to determine if G:F ratio remains constant across diets. A total of 1,153 Pigs (Camborough x TR-4) were blocked by weight and sex and allotted to 1 of 5 treatments. There were 51 pens (22-23 pigs/pen; single sex) used in the 27 d assay (end wt, 30.8 ± .4 kg). Two diets (1, 5) were manufactured for summit blend; one having 38.8% SBM and the other with 25.9% (see table). Diets were formulated to 1.28% SID Lys, with crystalline amino acids used to maintain a minimum of 63, 19, and 60% for Thr, Trp, and M+C ratios to Lys, respectively. Diets 2-4 were blended from diets 1, 5 to deliver equal spacing in SBM reduction. NE values used for formulation: 2663, 2123, 7595 kcal/kg for corn, SBM, and fat, respectively. Metabolizable energy (ME, 2012 NRC) values used for calculation: 3395, 3294, 8124 kcal/kg for corn, SBM, and fat, respectively. While NE remained constant across diets, ME declined by 17 kcal/kg for each diet. If the latter were true, then G:F ratio would erode rather than remain constant. Since the G:F ratio was constant (.65, .66, .65, .65, and .65, ± .01, P=.4769), we conclude that NE estimates used for this trial are realistic and NE is superior to ME in predicting performance. This further validates Hanor NE valuations for SBM as 0.80 x corn NE, and 2.85 x corn NE for Fat (CWG), corrected to equivalent DM basis.
Diets |
1 |
2 |
3 |
4 |
5 |
SEM |
SBM, % |
38.8 |
35.6 |
32.4 |
29.2 |
25.9 |
- |
Fat (CWG), % |
2.45 |
2.09 |
1.73 |
1.37 |
1.00 |
- |
ADG, kg |
.670 |
.675 |
.663 |
.675 |
.671 |
.008 |
ADFI, kg |
1.03 |
1.02 |
1.02 |
1.04 |
1.04 |
.017 |
Gain:Feed, as is |
.654 |
.659 |
.650 |
.648 |
.646 |
.006 |
Gain:Feed, DM correcteda |
.654 |
.657 |
.655 |
.654 |
.653 |
.006 |
aDM of corn and SBM corrected to 88% standard
Keywords: Net Energy, Soybean Meal, Growth