Abstract A conventional phase-feeding system is typically formulated to meet the nutrient requirements of a representative pig within a group (average). However, smaller pigs may not fully express their growth potential under this approach. For instance, due to their lower digestive capacity, lighter pigs consume less lysine and energy compared to their heavier counterparts. Therefore, this study aimed to evaluate the effects of increasing the standardized ileal digestible lysine (SIDLys) to net energy (NE) ratio on growth performance and body composition of growing pigs categorized by initial body weight (BWCat) into three groups (Small, Medium, and Large). A total of 200 pigs were individually weighed, and only 90 pigs were selected and classified into three homogeneous BW categories (Small: 19.29 ± 1.68 kg; Medium: 23.32 ± 1.44 kg, and Large: 28.71 ± 2.18 kg). These BWCat were randomly assigned into two dietary treatments (Control and High-SIDLys:NE). The experiment consisted of two feeding phases (PI and PII), each lasting 28 days. Control diets (SID Lys: 1.00% in PI and 0.87% in PII; both containing 2.475 Mcal NE/kg) were formulated according to NRC (2012). The High-SIDLys:NE diets provided a 15% increase in SIDLys and a 3% increase in NE. Pigs were fed ad libitum. BW and body composition (DXA) were assessed on days 0, 28, and 56. Data were analyzed using analysis of variance, including BWCat, diet, and their interaction. During PI, pigs fed diet with High-SIDLys:NE showed a greater G:F compared with those fed the control diet (Table 1, P 0.05). Within BW categories, pigs in the Small and Medium groups fed the High-SIDLys:NE diet showed numerically greater G:F than those fed the control diet; however, no BWCat × diet interaction was observed. During PII, pigs fed the High-SIDLys:NE diet had greater percentage of lipid in weight gain (LipGain%) and body lipid (P 0.05), and tended to have a greater percentage of protein in weight gain (PtnGain%) (P = 0.06) compared with pigs fed the control diet. Within BW categories, pigs in the Small BWCat fed the High-SIDLys:NE diet showed numerically greater LipGain% and body weight than pigs fed the control diet, but again no BWCat × diet interaction was detected. Overall, pigs fed the High-SIDLys:NE diet showed a tendency for greater LipGain% compared with those fed the control diet (P = 0.08). Within BW categories, pigs in the Small BWCat fed the High-SIDLys:NE diet showed numerically greater average daily gain (ADG) than pigs fed the control diet, with no significant BWCat × diet interaction. Increasing the SIDLys:NE ratio improves G:F during the first phase of the growing period, indicating a potential dietary strategy to enhance overall productivity in pigs.
Silva et al. (Wed,) studied this question.