Partitioning components of maternal growth to determine efficiency of feed use in gestating sows

The objective of this study was to evaluate the effect of parity and stage of gestation on predicted maternal weight gain and efficiency of feed use in gestating sows from a commercial sow farm. A total of 712 females (Camborough, PIC, Hendersonville, TN) were group-housed from days 5 to 112 of gestation and individually fed with electronic sow feeders (ESF). Feed intake and body weight (BW) were recorded daily throughout gestation via the ESF and a scale located in an alleyway just after sows exited the feeding station. Gilts (parity 1) and sows received 6,450 or 7,418 kcal ME, respectively, whereas 12 thin females received 9,675 kcal ME per day. Maternal weight gain, not including products of conceptus, and feed efficiency were predicted using a series of equations to model nutrient utilization in gestation. Data were divided into 3 parity groups: 1, 2, and 3+, and gestation was divided into 3 periods: days 5 to 39, 40 to 74, and 75 to 109. After dividing energy requirements into tissue pools for maintenance, growth (maternal protein and fat deposition), and products of conceptus, the greatest portion of the energy requirement was for maintenance and maternal growth. The predicted energy used for maternal protein and fat deposition decreased (P < 0.05) in each period of gestation, regardless of parity group. Parity 2 sows had the greatest (P < 0.05) energy use for maternal protein and fat deposition in all stages of gestation, whereas parity 1 sows had a negative energy balance during the final stage of gestation. Parity 1 sow BW increased (P < 0.05) in each period of gestation; however, parity 2 and 3+ sow BW remained static from days 75 to 109 of gestation. Parity 3+ sows had the greatest (P < 0.05) maternal BW throughout the course of gestation compared with other parity groups. Regardless of parity, maternal ADG decreased (P < 0.05) from days 40 to 74 before increasing (P < 0.05) during the final stage of gestation. Parity 1 sows had the greatest (P < 0.05) ADG in all gestation periods. Parity 1 sow G:F decreased (P < 0.05) in each sequential period of gestation. Parity 2 and 3+ sow G:F decreased (P < 0.05) from days 40 to 74 but improved (P < 0.05) during the final period of gestation. Parity 1 sow G:F was greater than parity 2 and 3+ sows in most gestation periods. Overall, this study and subsequent prediction models show how stage of gestation and parity affect the growth of different tissue pools, sow maternal BW, and feed usage throughout the course of gestation.