Increasing Dietary Lysine Impacts Differently Growth Performance of Growing Pigs Sorted by Body Weight

Abstract

An experiment was conducted analyzing whether growing pigs classified in different initial body weight categories (BWCAT) have a different response to increasing standardized ileal digestible lysine to net energy ratio (SID Lys:NE), to assess whether light pigs might benefit from being differentially fed. A total of 1170 pigs in pens of 13 were individually weighed, classified in 3 BWCAT (Lp: 32.1 ± 2.8 kg, Mp: 27.5 ± 2.3 kg, and Sp: 23.4 ± 2.9 kg), and afterwards pens were randomly allocated to 5 dietary SID Lys:NE treatments (3.25 to 4.88 g/Mcal) fed over 47 days. Results reported a greater linear improvement of growth and feed efficiency of Sp compared to Lp when increasing SID Lys:NE. Modelling the response to SID Lys:NE using quadratic polynomial models showed that the levels to reach 98% of maximum growth from day 0-47 were 3.67, 3.88, 4.06 g SID Lys/Mcal NE for Lp, Mp, and Sp, respectively. However, due to the overlapping SID Lys:NE confidence intervals at maximum performance, it was not possible to determine if requirements were different between BWCAT. Summarizing, the results suggested that feeding small pigs greater SID Lys:NE than large pigs can improve their performance and increase the efficiency of the overall production system.

Keywords: body weight; growing pig; lysine; requirements.

Figure 1

Effects of initial body weight category (Large/Lp: red; Medium/Mp: green; Small/Sp: blue) on body weight (A), average daily gain (B), average daily feed intake (C) and feed to gain (D) of growing pigs in Experiment 1. Results in A are provided for the 3 weighing days. For B, C and D results are provided for Phase 1 (d 0–26), Phase 2 (d 26–47) and Overall (d 0–47). Error bars represent the standard error of the mean.

Figure 2

Effect of standardized ileal digestible lysine to net energy ratio (SID Lys:NE) on final backfat thickness and loin depth of medium body weight category pigs measured using an ultrasound scan at P2. (A) Backfat thickness was linearly (p = 0.004) reduced when increasing SID Lys:NE whereas there was no evidence of an effect of SID Lys:NE on (B) loin depth (p = 0.261).

Figure 3

Fitted broken-line linear (BLL, green), broken-line quadratic (BLQ, orange) and quadratic polynomial (QP, magenta) regressions models to optimize (A) average daily gain (ADG) and (B) gain to feed (G:F) as a function of standardized ileal digestible lysine to net energy ratio (SID Lys:NE) from 28–63 kg (Overall phases). For ADG, the BLL model estimated the optimum at 3.72 g/Mcal (95% CI: [3.58, 3.86], BIC = 908), the BQL at 3.91 g/Mcal (95% CI: [3.55, 4.27], BIC = 905) and the QP at 4.40 g/Mcal (95% CI: [4.21, 4.59], BIC = 905). Regarding G:F, BLL estimated the optimum at 4.29 g/Mcal (95% CI: [4.04, 4.53], BIC = 785), BLQ at 4.77 g/Mcal (95% CI: [4.27, >4.88], BIC = 774) and QP > 4.88 g/Mcal (95% CI: [4.25, >4.88], BIC = 774), both outside the range of the experiment.

Figure 4

Fitted regressions models to optimize (A) average daily gain (ADG) using quadratic polynomial models (QP) and (B) gain to feed (G:F) using broken-line linear (BLL) models as a function of standardized ileal digestible lysine to net energy ratio (SID Lys:NE) from 28–63 kg (Overall phases) for each body weight category (Large/Lp: brown, Medium/Mp: blue and Small/Sp: green) in Exp 1. For ADG, the QP models estimated the optimum of Lp at 4.28 g/Mcal (95% CI: [3.91, 4.67]), of Mp at 4.33 g/Mcal (95% CI: [4.13, 4.53]), and of Sp at 4.60 g/Mcal (95% CI: [4.02, >4.88]). Regarding G:F the BLL models estimated the optimum of Lp at 4.29 g/Mcal (95% CI: [3.68, >4.88]), of Mp at 4.75 g/Mcal (95% CI: [4.21, >4.88]), and of Sp at 4.36 g/Mcal (95% CI: [4.00, 4.73]).