Phase-feeding programs have been widely used to closely meet the nutrient requirements of grow-finish pigs and to reduce nutrient excretion in the environment. Accurate estimates of nutritional requirements are essential to develop phase-feeding strategies and to minimize the supply of nutrients in excess or deficiency.
However, reducing the number of diets fed will, in most cases, improve feed mill efficiency. Once diets are removed from production, longer single runs of existing diets and simplification of load-out bin logistics and feed delivery are achievable.
Find the right balance
Over the past year, a series of commercial environment phase-feeding trials have been conducted by the Kansas State Applied Swine Nutrition Team. The objectives were to determine the impact of the number of phases and changes in amino acid concentrations by phase on growth performance and profitability of modern grow-finish pigs.
First, a study evaluated different dietary lysine regimes in different phase-feeding programs. The treatment structure was: MAX, a four-phase program with lysine levels for maximum growth; STD, a standard four-phase program with lysine levels to optimize income over feed costs (IOFC); STD/MAX, a four-phase program based on STD lysine levels in early finishing and MAX lysine levels in late finishing; and 2-PHASE, a two-phase program based on MAX lysine requirement estimates.
Overall in the 117-day study, pigs fed the 2-PHASE feeding program had increased average daily gain (ADG) compared to pigs fed the STD regimen. Feeding either the MAX or STD/MAX regimen resulted in intermediate ADG.
There was no evidence for differences in feed to gain ratio (F/G), carcass traits and IOFC across feeding programs. The results of this study demonstrate feeding lysine levels for maximum growth in either a two- or four-phase feeding program (2-PHASE or MAX, respectively) results in the same overall growth performance and profitability. In light of these results, the following studies focused on defining the optimum number of dietary phases for grow-finish pigs.
Another study evaluated either a one-, two-, three-, or four-phase feeding program with estimated lysine levels set for 100% of maximum growth rate and 98.7% of maximum feed efficiency for the weight range in each phase.
For the overall 121-day study, pigs fed the one-phase program had decreased ADG compared to those fed the two- and four-phase programs, with the three-phase program intermediate. The feeding programs with either two or four dietary phases resulted in similar ADG in the overall grow-finish period.
There were no differences for F/G, carcass traits or IOFC across the feeding programs. Thus, when formulating diets to the dietary amino acid requirement, using only two phases did not decrease performance or profitability.
A third study evaluated a scenario where lysine levels were set for 98.5% of maximum growth rate and 97.5% of maximum feed efficiency for the weight range in each phase. Again either one, two, three or four phases were tested.
Overall, in the 119-day study, the one-phase program resulted in lower ADG compared to the four-phase program, with two- and three-phase programs intermediate. The one-, two- and three-phase programs resulted in poorer F/G compared to the four-phase program, with the poorest F/G in the one-phase program. No evidence for differences was observed for carcass traits.
For economics, revenue and IOFC per pig were increased in the four-phase program compared to the one-phase program, with two- and three-phase programs intermediate. This suggests feeding dietary lysine levels, that are lower than what is required for maximum performance, throughout finishing results in poorer growth and profitability when feeding phases are reduced.
Simplification of feeding programs down to two dietary phases with lysine levels closely set to achieve maximum performance does not compromise overall growth performance, carcass characteristics and IOFC.
These results allow for the possibility of using fewer feeding phases during the grow-finish period, which might have practical advantages for feed manufacture, storage and delivery.