PSVII-25 Intra-Farm Variability: Growing pigs have different SID Lys:NE requirements depending on their BW category

Abstract

Abstract The objective of this experiment was to determine if pigs with different initial body weight within the same farm batch have different SID Lys:NE requirements. In the trial 1,170 growing crossbred pigs were distributed in 90 pens (13 pigs/pen) and split in three initial BW categories: Large, Medium and Small (32.1 ± 2.8, 27.5 ± 2.3 and 23.4 ± 2.9 kg, respectively). Each pen was randomly assigned by BW to one of the SID Lys:NE levels (3.25, 3.66, 4.07, 4.47 and 4.88 g SID Lys/Mcal NE), with 6 replicates per dietary treatment. All diets were isoenergetic (2460 kcal NE/kg), and CP ranged from 14.50 to 17.50 %. The dietary treatments were fed for 26 days. Statistical analysis to determine the effect of SID Lys:NE was performed using the GLM procedure of SAS with linear and quadratic polynomial contrasts. In addition, broken-line linear models were fit with the NLIN procedure of SAS to determine the break-point to maximize ADG or minimize FCR for all categories together or independently. The ADG break-point for all pigs was determined at 3.89 g SID Lys/Mcal NE. However, when analyzed by categories, the break-point was 3.86, 4.07 and 4.76 g SID Lys/Mcal NE for large, medium and small pigs respectively. The general break-point for FCR was determined at 4.25 g SID Lys/Mcal NE. By BW categories the different break points determined were: 4.27, 4.15 and 4.59 g SID Lys/Mcal NE for large, medium and small pigs, respectively. In conclusion, the estimated requirement to maximize ADG and optimize FCR via broken-line models is higher for small pigs than large or medium. Therefore, pigs within the same farm batch should be differentially fed in relation to the SID Lys:NE ratio.