Effect of different dietary total Lys:energy ratios and dietary energy concentrations in phase feeding from weaning to slaughter on performance and carcass measures of crossbred pigs selected for leanness

Abstract The objective of this study was to evaluate the effect of two treatments with varying dietary total Lys:NE ratios and NE concentrations in a concept of phase feeding from weaning to slaughter on growth performance and final carcass measures of crossbred pigs selected for leanness. All pigs were fed a meal diet according to a 5-phase ad libitum feeding scheme (8–12 kg, 12–20 kg, 20–40 kg, 40–70 kg, 70–105 kg). During the first phase (8–12 kg), all pigs were fed the same commercial starter diet, containing 1.14 g Lys MJ −1 NE and 9.77 MJ NE. Afterwards, the pigs were randomly assigned either to a standard diet or a concentrated diet. The standard diets during the last 4 subsequent phases were characterized by Lys:NE ratios of 1.14, 1.04, 0.97 and 0.91 g Lys MJ −1 NE and NE concentrations of 9.74, 9.83, 9.83 and 9.76 MJ NE. The concentrated diets contained increased levels of Lys:NE, i.e. 1.14, 1.04, 0.97 and 0.91 g Lys MJ −1 NE and NE concentrations, i.e. 10.02, 10.36, 10.36 and 10.19 MJ NE. Overall, no effect of feeding the concentrated diet was found on the growth rate from weaning to slaughter. However, analysing the data for each growing phase reveals that feeding the concentrated diet had a positive effect on daily gain, feed efficiency and energy efficiency from 12 to 20 kg and from 20 to 40 kg. After 40 kg, daily gain was unaffected by treatment, but feed and energy efficiency were positively affected when feeding the standard diet. Finally, lean meat content was unaffected by treatment. In conclusion, accurately tuning nutrient density to pigs' genetic capacity to grow and deposit lean meat is necessary, in order to maximize profitability in relation to feed cost. A negative effect on growth can be observed during the last phases before slaughter which was explained as an effect of oversupply of nutrients. Especially during these phases, feed cost is a deciding factor because of the lower feed efficiency in comparison with the earlier phases.