Results and discussion There were no significant differences between sex for any parameter across all phases. Also, no differences were ob- served among treatments for the first week of the trial in ADG and ADFI. However, there was a quadratic increment in G:F ratio (P < 0.05) when the SID lysine concentration in the diets was increased. From days 7 to 14, a quadratic increase in ADG and ADFI (P < 0.05) was observed and a linear in- crease (P < 0.05) of G:F of weanling pigs as the dietary SID lysine concentration was increased. During the last week, from days 14 to 21, there was a quadratic increase (P < 0.05) in ADG and G:F. For the whole period, increasing dietary SID lysine increased the final BW, ADG and G:F linearly and quadratically (Table 1). The ADG for pigs fed the 1.48% SID lysine diet was 36% greater compared to pigs fed the lowest (1.00%) SID lysine diet. Also, pigs fed the 1.48% SID lysine diet had a 21% higher G:F compared to those fed the lowest (1.00%) SID lysine diet. The PUN concentration was similar across treatments at day 0, whereas at days 14 and 21 PUN decreased linearly and quadratically (P < 0.05) as the SID ly- sine level increased. Plasma urea nitrogen is used as an indi- cator of protein utilisation and thus its concentration indi- cates the utilisation of AA either for anabolic or catabolic purposes. As observed in this study, the PUN concentration declines as the dietary lysine intake increases up to a point where the lysine requirement is met, indicating more effi- cient utilisation of AA.
Using the values for ADG observed during the entire experi- mental period, the SID lysine requirement was estimated at 1.38% using the quadratic broken-line model (Figure 1). For the overall G:F, the quadratic broken-line model estimated the optimal level of SID lysine to be 1.46% (Figure 2). This re- sults in a mean SID lysine requirement of 1.42% for 7-15 kg weanling pigs with a high lean genetic potential, which is higher than the value of 1.35% SID lysine requirement sug- gested by NRC (2012), but closer to the recommendations of Topigs (1.34-1.39% SID Lys) and Evonik (1.37%) designed to optimise growth performance.
The results of the study show that increasing dietary SID ly- sine increased final BW, ADG and G:F.
Table 1 – Effect of dietary lysine level on performance and plasma urea nitrogen (PUN) concentration.
BW at d 0, kg BW at d 21, kg Overall ADG, g Overall ADFI, g Overall G:F, g/g
PUN at d 0, mmol/L)
1.00 6.50
Standardized ileal digestible lysine, % 1.16 6.51
PUN at d 14, mmol/L) 3.94 PUN at d 21, mmol/L) 3.58
386 505 0.77 3.10 3.45 3.24
P-value
1.32 1.48 1.64 1.80 SEM Linear 6.50 6.53 6.53 6.51 0.20 0.20 0.50
13.32 14.61 15.57 15.88 15.22 15.46 0.52 0.01 0.01 325 475 0.68 3.03
433 443 414 417 18.5 558 540 500 527 25.9
0.01 0.24
*a-b Values in a row with different letters are different (P < 0.05). ▶ ALL ABOUT FEED | Volume 28, No. 9, 2020 27 Quad.
0.01 0.07
0.79 0.82 0.81 0.81 0.02 0.01 0.01 3.15 3.04 2.86 3.51 0.39 0.59 0.72 1.80 1.46 2.13 1.03 0.40 0.01 0.01 1.36 2.01 1.64 1.66 0.27 0.01 0.01
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