### INTRODUCTION

_{m}) and IFI for growth (IFI

_{g}). The IFI

_{m}is calculated based on the metabolizable energy (ME) of a diet and the mean body weight (BW) of an individual animal during the feeding period using an equation suggested by NRC (1998).

_{m}) has been estimated from various coefficients and exponents for metabolic BW (Kil et al., 2013). In NRC (1998), the use of ME

_{m}values calculated based on the metabolic BW using an exponent of 0.75 and a mean estimate of 106 as the coefficient for growing-finishing pigs: ME

_{m}, kcal/d = 106 kcal×kg BW

^{0.75.}However, Noblet et al. (1999) suggested that the exponent of metabolic BW be expressed as 0.60 rather than 0.75 for growing-finishing pigs. In NRC (2012), the ME

_{m}of growing-finishing pigs is described using the exponent of 0.60 and the mean coefficient of 197: ME

_{m}, kcal/d = 197 kcal×kg BW

^{0.60}. To our knowledge, the use of the coefficient and metabolic BW exponent for calculating ME

_{m}suggested in NRC (2012) has not been tested for the estimation of IFI.

_{m}to calculate IFI

_{m}improves the accuracy of the estimates of IFI for pigs and that the PM estimates IFI of pigs fed in group-housing systems with greater accuracy compared with other methods.

### MATERIALS AND METHODS

### Simulation study 1

*ad libitum*access to the diet (2,945 kcal of ME/kg) and water. Body weight of individual pigs and IFI were recorded weekly. Growth data on a bi-weekly basis were used to compare the actual and estimated IFI. The final BW of the pigs was 57.7 kg (SD = 3.7).

### Simulation study 2

*ad libitum*access to the diet of 3,312 kcal of ME/kg and to water. Pigs were fed in group pens of practical farms, and individual BW of pigs and IFI records were kept daily using FIRE System (Osborne Industries Inc., Osborne, KS, USA) and Acema-128 (Acemo, Pontivy, France). The growth data on a biweekly basis were used to compare the actual and estimated IFI. The final BW of the pigs was 101.8 kg (SD = 7.4).

### Partitioning method to estimate individual feed intake

_{m}and IFI

_{g}. Based on the ME in feed (kcal/kg), IFI

_{m}can be calculated as:

_{f}is the ME concentration in the feed (kcal/kg). The coefficient of 197 and exponent of 0.60 for metabolic BW is also used according to NRC (2012):

_{m}for all pigs within the pen represented as the pen FI (PFI) for maintenance (PFI

_{m}) is then subtracted from total PFI (kg), and the remainder is PFI for growth (PFI

_{g}) as:

_{m}is the sum of IFI

_{m}for all pigs in the pen, in kilograms.

_{g}by apportioning PFI

_{g}equally to each kg of BW gain during the period of interest within the pen:

_{m}and IFI

_{g}is IFI for the pig in the pen as:

### Ratio method to estimate individual feed intake

_{m}of pigs, but focuses of IBWG. This method only apportions the PFI equally to each kg of IBWG:

### Averaging method to estimate individual feed intake

### Comparison among methods to estimate individual feed intake

### Statistical analysis

### RESULTS

### Metabolizable energy for maintenance

_{m}(kcal/d) based on the different coefficients and exponents for metabolic BW ranged from 0 to 459.9 kcal/d for growing-finishing pigs (Figure 1). Point of intersection where the difference in values of ME

_{m}equaled 0 was approximately 62.3 kg of BW.

### Simulation study 1

### Simulation study 2

### DISCUSSION

_{m}estimated using the equation suggested by NRC (1998) becomes greater than ME

_{m}estimated using the equation suggested by NRC (2012) as the BW of pigs exceeds 62.3 kg (Figure 1). The mean BW of pigs for the total period of simulation studies 1 and 2 were 48.6 and 84.4 kg, respectively. The absolute difference between the respective ME

_{m}values of pigs with BW of 48.6 and 84.4 kg calculated based on the equations suggested by NRC (1998) and NRC (2012) were 74.0 and 132 kcal/d, which accounts for small portion of the daily FI when the ME

_{m}was divided by ME in the diets.

### CONCLUSION

^{0.60}as ME

_{m}in PM does not improve the accuracy of IFI estimates compared with the use of 106 kcal×kg BW

^{0.75}, and that partitioning the IFI into IFI

_{m}and IFI

_{g}provided the IFI of the pigs with greater accuracy compared with an AM or RM in group-housing systems.