Evaluation of Equations to Predict Carcass Fat Iodine Value

Fangzhou Wu

Lee Johnston, Pedro Urriola, and Gerald Shurson

Pork fat quality is affected when pigs fed high DDGS diets

Feeding DDGS reduces firmness and appearance of pork carcass fat

Traditionally, DDGS has contained > 10% oil• Corn oil contains primarily unsaturated fatty acids

Wu et al. (2014)DDGS FA profile

0% 20% 40% 60% 80% 100%

SFA MUFA PUFA

Corn-SBM diet30% DDGS diet

• Soft and “oily” belly• Less desirable for bacon

manufacturing

Current U.S. pork fat quality standards Iodine value (IV) measures the unsaturation of FA

• An accepted indicator of fat firmness• Maximum acceptance of IV

• 70 – National Pork Producers Council• 74 – Boyd et al. (1997)

DDGS level in diets linearly increase IV of belly fat

0% 10% 20% 30%0

20

40

60

80

Belly fat IV, g/100gFirmness score, degree

% of DDGS in dietXu et al., 2010

Based on quantity and composition of dietary lipid• Linoleic acid (C18:2) concentration• IV product (IVP) = dietary IV × % dietary lipids × 0.10• Inclusion level of DDGS in diet

Paulk et al. (2015) included more predictors including:– Essential FA (C18:2 and C18:3)– Days on initial and final diets– NE content of diets– Carcass composition

Which prediction is the best?

Prediction of IV helps to manage acceptable carcass fat IV

Objectives

1. Determine the carcass fat IV of pigs fed 7 sources DDGS with variable oil content

2. Evaluated the precision and accuracy of published IV prediction equations for carcass fat depots

Experimental Design Two experiments with identical design and procedure Housing and animal management

• 432 pigs/experiment (initial BW = 22.0±4.3 kg)• Randomized complete block design

• 9 pigs/pen• 12 replications/treatment

• Confinement grower-finisher facility at WCROC, Morris, MN

Choice of feed ingredients• 7 sources of DDGS with variable ether extract (EE) content

Experimental Design

A B C D E F G0.0

5.0

10.0

15.0

5.9

9.9

14.2

5.6

10.7

14.216.0

EE (%) of DDGS, as-fed

Exp. 1 Exp. 2

Experimental Design Diet formulation (averaged among phases; as-fed):

Exp. 1 Exp. 2CON A B C D E F G

Corn, % 75.2 52.5 52.8 52.7 44.5 44.5 44.5 44.5

Soybean meal, % 22.4 4.7 4.7 4.7 13.1 13.1 13.1 13.1

DDGS, % - 40.0 40.0 40.0 40.0 40.0 40.0 40.0

Minerals, vitamins, AA, % 2.4 2.8 2.5 2.6 2.4 2.4 2.4 2.4

Total, % 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

• No additional source of lipid was added

• Met requirements from NRC (2012) model

Data Collection

• Fatty acid profile– 2 pigs/pen, with BW closest to pen average BW

• BW = 114.6 ± 7.9 kg • Backfat, belly, and jowl fat depots

• Calculation of IV (AOCS, 1998)

IV =[C16:1] × 0.95 + [C18:1] × 0.86 + [C18:2] × 1.732 + [C18:3] × 2.616 + [C20:1] × 0.785 + [C22:1] × 0.723

*Brackets indicate concentration

Statistical analysis and calculations• Mixed procedure of SAS

– Experimental unit = pen (n = 12)– Split plot design: whole plot = diet, subplot = depot

• Fixed effect: diet, depot, and diet × depot• Random effect: block

– Significance P ≤ 0.05

• Prediction error (precision):

• Bias (accuracy):

Results

Exp.1 - carcass fat IV, g/100g

CON A (6%EE) B (10%EE) C (14%EE)55.0

60.0

65.0

70.0

75.0

80.0

Diet (P < 0.01)depot (P < 0.01)Diet × depot (P < 0.01)Pooled SEM = 0.79

abc

efdd

fgdede

ighh

a - i Least squares means with different superscripts differ (P ≤ 0.05)

Exp.2 - carcass fat IV, g/100g

D (6%EE) E (11%EE) F (14%EE) G (16%EE)60.0

65.0

70.0

75.0

80.0

85.0

Diet (P < 0.01)Depot (P < 0.01)Diet × depot (P = 0.08)Pooled SEM = 0.78

abac

aac

babc

edf

a - f Least squares means with different superscripts differ (P ≤ 0.05)

Determined backfat IV

a-f Least squares means with different superscripts differ (P ≤ 0.05)

CON D A B E F C G0.0

20.0

40.0

60.0

80.0

57.7

68.774.1 74.3

70.3 71.379.0

82.3

Bac

kfat

IV, g

/100

g

ba d d cbc e f

P = 0.12R2 = 0.42

IV = 65.9 + 0.762 EE% of DDGS

Diet

EE of DDGS, % - 5.6 5.9 9.9 10.7 14.2 14.2 16.0

Max. IV of 74

Prediction of backfat IVSource Equations PE Bias

Benz et al., 2011 51.946 + 0.2715 × Diet IVP 6.45 -5.05

Boyd et al., 1997 52.4 + 0.315 × Diet IVP 4.60 -2.15

Estrada, 2013 60.13 + 0.27 × Diet IVP 5.04 3.05

Madsen et al., 1992 47.1 + 0.14 × IVP/day 6.43 -4.95

Benz et al., 2011 35.458 + 14.324 × Diet C18:2, % 8.36 -1.08

Cromwell et al., 2011 64.5 + 0.432 × % DDGS in diet 8.26 7.10

Estrada, 2013 70.06 + 0.29 × % DDGS in diet 9.19 8.00

Paulk et al., 201584.83 + (6.87 × I EFA) - (3.90 × F EFA) - (0.12 × I d) - (1.30 × F d) - (0.11 × I EFA × F d) + (0.048 × F EFA × I d) + (0.12 × F EFA × F d) - (0.0060 ×

F NE) + (0.0005 × F NE × F d) - (0.26 × BF) 4.01 -0.84

Prediction of jowl fat IVSource Equations PE Bias

Benz et al., 2011 56.479 + 0.247 × Diet IVP 4.92 -3.69

Estrada, 2013 64.54 + 0.27 × Diet IVP 6.55 5.66

Benz et al., 2011 47.469 + 10.111 × Diet C18:2,% 5.57 -1.37

Estrada, 2013 72.99 + 0.24 × DDGS in diet, % 8.33 7.37

Paulk et al., 201585.50 + (1.08 × I EFA) + (0.87 × F EFA) -

(0.014 × I d) - (0.050 × F d) + (0.038 × I EFA × I d) + (0.054 × F EFA × F d) - (0.0066 × I NE) + (0.071× I BW) - (2.19 × ADFI) - (0.29 × BF)

4.73 -3.37

Prediction of belly fat IV

Source Equations PE Bias

Estrada, 2013 58.32 + 0.25 × Diet IVP 3.43 1.41

Estrada, 2013 67.35 + 0.26 × DDGS in diet, % 6.66 5.53

Paulk et al., 2015

106.16 + (6.21 × I EFA) - (1.50 × F d) - (0.11 × I EFA × F d) - (0.012 × I NE) +

(0.00069 × I NE × F d) - (0.18 × HCW) - (0.25 × BF)

3.27 1.73

Conclusions In general, more oil in DDGS results in higher carcass fat IV.

Only using oil concentration does not adequately predict carcass fat IV because lipid digestibility need to be considered.

When only using the characteristics of dietary lipid, diet IVP and C18:2 are better single predictors than dietary DDGS level

Including more comprehensive predictor variables (Paulk et al, 2015) improves the accuracy and precision of prediction.

Questions

AcknowledgementsFunding provided by:

MN Pork BoardMN Corn Research & Promotion CouncilAgricultural Utilization Research Institute

True ileal and ATT digestibility of acid-hydrolyzed EE (%) in Corn Co-Products and Soybeans

%

Kim et al. (2013)

ATTD of EE in DDGS

1 2 3 4 5 6 7 8 9 10 11 12 13 14 150

102030405060708090

Sources of DDGS

%

Kerr et al.,2013