433
Prediction of primal cut weights in pigs using a non-linear mixed procedure
The objective of this trial was to model the relationships of carcass measurements and primal cut weights to carcass weight and estimate the residual variation. Data from 558 pigs (94.16 ± 7.6 kg of hot carcass weight, HCW) were collected at a pork processing plant. To get an accurate representation of a normal production day, several suppliers were chosen based on their relative participation on the total pigs provided to the plant. Hot carcass weight, loin depth (LD), backfat depth (BF) and percent lean (PL) were recorded for each pig during the slaughter process. Primal cut belly, butt, picnic, sparerib, ham and loin weights were recorded for each carcass side. To linearize the allometric function (Y = AXB), natural logarithm to natural logarithm transformation was performed (LN Y = LN A + B LN X). To evaluate which combination of explanatory variables were best, different models were tested. For all cut weights, a model that included LNHCW, SIDE, SUPPLIER and LNHCW*SUPPLIER interaction was used, then LD and BF were added. A non-linear mixed procedure (SAS) was used to fit the model for cut weight which was: cut weight =A*(HCW)B + b1(BF -19.65) + b2(LD – 62.37) + (b3*SIDE). The effect of SIDE was significant for estimating sparerib, ham, picnic and loin weights (P < 0.001). Also LD was significant for the estimation of loin weight (P < 0.001). For belly and picnic cuts, SUPPLIER was significant (P < 0.05). Estimates for an equation to predict belly and picnic weights for each supplier were performed. Pork primal cut weights can be estimated using a non-linear mixed model.
Table. Estimates for predicting cut weights using an overall equation.
|
A |
B |
b1-BF |
b2-LD |
b3-SIDE |
Residual |
|
Weight, kg |
Estimate |
Estimate |
SE |
Estimate |
Estimate |
Estimate |
Variance |
Belly |
0.054 |
1.074 |
0.04 |
0.041 |
|
|
0.35 |
Butt |
0.066 |
0.919 |
0.04 |
-0.037 |
|
|
0.15 |
Ham |
0.149 |
0.947 |
0.02 |
-0.047 |
|
0.090 |
0.41 |
Loin |
0.206 |
0.881 |
0.02 |
0.039 |
0.012 |
0.294 |
0.37 |
Picnic |
0.084 |
0.892 |
0.02 |
-0.021 |
|
-0.047 |
0.09 |
Sparerib |
0.013 |
1.092 |
0.04 |
-0.013 |
|
-0.083 |
0.04 |
All b1-BF estimates (P < 0.001)
b2-LD estimate (P < 0.001)
All b3-SIDE estimates (P < 0.001)
Keywords: primal cut, non-linear mixed procedure, allometric function.