부산대학교 도서관

Continuous genetic progress leads to significant improvements in growth and efficiency of PIC Camborough gilts. As an example, gilt weight gain per day of age has increased dramatically in the past decade. This implies that gilts are heavier at a similar breeding age, which increases the likelihood of breeding overweight gilts. Additionally, sows have less backfat depth and are leaner compared with their predecessors. It has been reported that gilt retention rate until parity 3 declines when breeding gilts with over 160 kg of body weight. Hence, controlling growth rate of developing gilts could be helpful to achieve the target breeding weight (135 to 160kg). A recent study reported that reducing dietary nutrient density (ME and SID Lys) from 57 kg until breeding significantly reduced breeding weight by 4 kg (P < 0.05). The slower growing gilts had reduced stillborn (P < 0.01), had 0.79 more pigs born alive (P = 0.10), and weaned a total of 238 more pigs over three reproductive cycles. However, with the genetic trend for faster growth rate, it is inevitable to breed overweight gilts in production. Energy requirement for maintenance (MEm) of gestating sows is a function of body weight of the sow. Thus, heavier gilts at breeding need more energy for maintenance. An assessment using data from 2,475 gilts collected in commercial sow farms evaluated how different feeding levels satisfy the MEm of a gilt herd bred at 154 kg. The results showed that feeding 5.90 Mcal of ME/day or 4.40 Mcal of NE/day results in only a few gilts fed below maintenance from 90 to 112 days of gestation. However, if a decreased feeding level (5.17 Mcal of ME/day or 3.85 Mcal of NE/day) was adopted, which has been seen in production with a purpose of reducing body condition, almost all the gilts would be fed under maintenance from 90 to 112 days of gestation. Gilts are still growing and developing during their first gestation and inadequate feeding level may jeopardize their growth and development, which could lead to poor lifetime productivity. Heavier gilts become heavier sows in the subsequent parities; thus, the sows also require more energy for maintenance during subsequent gestations. Therefore, PIC recommends feeding gilts, ideal and fat sows with 5.90 Mcal of ME/day or 4.40 Mcal of NE/day throughout gestation. Feeding this level throughout gestation will result in an estimation of no overall caliper change. Whereas for thin sows that need to recovery condition, PIC recommends feeding 8.60 Mcal of ME/day or 6.50 Mcal of NE/day (Figure 1). Feeding this level throughout gestation will result in an estimated overall gain of 3 caliper units. In summary, the increased potential for growth and efficiency of PIC gilts warrants the adoption of multiple strategies to improve longevity and lifetime productivity. [ABSTRACT FROM AUTHOR]