Limiting Dietary Lysine Increases Body Weight Variability by Restricting Growth Potential of the Lightest Growing Pigs

Abstract

The goal of this experiment was to determine the implications of dietary standardized ileal digestible lysine (SID Lys:NE) on body weight variability of growing pigs grouped in three initial body weight categories (BWCAT). Animals (N = 1170) were individually weighed and classified in 3 BWCAT (Lp: 32.1 ± 2.8 kg, Mp: 27.5 ± 2.3 kg, and Sp: 23.4 ± 2.9 kg). Afterward, pens were randomly allocated to five dietary SID Lys:NE treatments (3.25 to 4.88 g/Mcal) that were fed over 47 days. Pen coefficient of variation of Sp at day 47 was linearly increased when reducing SID Lys:NE (p < 0.01), from 9.8% to 15.4% between the two extreme dietary levels. The linear effect was different in Sp compared to Lp (p < 0.05) as no effect of SID Lys:NE was reported in the latter BWCAT (p = 0.992). Further analysis showed that this effect was explained by a growth restriction that was more severe the lightest the pigs were at the start of the trial. To summarize, swine body weight variability can be negatively affected when SID Lys requirements are not fulfilled.

Keywords: body weight; coefficient of variation; growing pig; lysine; variability.

Figure 1

Density plots of initial and final individual body weight (BW) distribution by standardized ileal digestible lysine to net energy ratio (SID Lys:NE) for each body weight category (BWCAT). Pen BWCAT were small (A,B, 23.4 ± 2.9 kg), medium (C,D, 27.5 ± 2.3 kg) or large (E,F, 32.1 ± 2.8 kg). The plots on the left side are for BW at day 0, whereas the ones on the right side are of BW at day 47. Vertical lines represent the 1/3 and 2/3 quantiles.

Figure 2

Scatterplot of individual initial and final body weight (BW), day 0 and 47, respectively, depending on the standardized ileal digestible lysine to net energy ratio (SID Lys:NE) fed. Lines represent the best fit of the multiple regression mixed model, including the interaction between initial BW and SID Lys:NE to predict final BW. The regression equations are: 19.8 + 1.57 × BW_d0, 16.1+ 1.72 × BW_d0, 14.5+ 1.76 × BW_d0, 15.0 + 1.74 × BW_d0, 5.9 + 1.97 × BW_d0 for 4.88, 4.77, 4.07, 3.66 and 3.25 g SID Lys/Mcal NE.