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A four-parity study is proposed to examine the effects of nutritional manipulation during gilt development on subsequent sow performance. Gilts will be selected from two genetic lines that are highly prolific, but differ in rate and composition of growth. During the development period (45 to 250 lb), gilts will be provided either; i) ad libitum access to feed, or ii) ad libitum access to feed until 120 days of age (180 lb) and 75% of ad libitum feed intake thereafter (until first post-pubertal estrus). Sow and litter performance criteria will be examined. In addition, the economics of sow productivity and longevity will be evaluated using a return on equity model. Crossbred females of the Nebraska Index Line (NIL) with other maternal lines are being used in several herds within Nebraska and the United States. Not only has there been little research conducted investigating the effects of nutritional manipulation during gilt development on future sow productivity of the NIL crosses, but little information is available regarding how gilt development (as affected by nutritional manipulation) influences sow productivity of early-maturing, prolific sows. Results from this research project will help producers make decisions regarding the management of replacement gilts and define management scenarios that will optimize sow lifetime productivity. Project progress and research data updates will be provided annually in the University of Nebraska Swine Report until the completion of the study.