Introduction:  Swine production is globally distributed. The U.S. is the world's third-largest swine producing country behind China and the E.U. The U.S. has been the world’s largest or 2nd largest exporter of pork and pork products, with exports typically averaging over 20% of commercial pork production. Currently, U.S. pork production operations are heavily concentrated in the Midwest and eastern North Carolina. In 2016, about 118.3 million hogs were slaughtered in the U.S. for an estimated gross on-farm value of $18.9 billion (USDA, 2017). The average daily inventory was 72.9 million swine, of which 6.2 million were sows (USDA, 2018). Swine production is driven by the fact that pork continues to be one of the major high-quality sources of protein in human diets and, because of its flavor, pork is the meat of choice worldwide with an average per capita consumption of pork in the U.S. of 22.7 kg (USDA, 2018).

Need as indicated by the stakeholders: Swine enterprises constitute a major source of on-farm income in the Southern Region of the U.S. and pork production in the Southern Region represents a significant portion of U.S. pork production, especially sow production. The most rapidly growing component of swine production in the Southern Region has been in sow farms producing feeder pigs that are shipped to the Midwest for finishing. This trend is attributed to favorable environmental conditions, the availability of labor, and interest in contract swine production in the Southern Region and to an availability of feedstuffs in the Midwest.

A primary factor affecting the profitability of swine production is sow productivity. Optimum nutrition of the sow is essential to maximize sow productivity and longevity. An ideal nutrition program should provide adequate nutrients to maximize sow productivity while minimizing excreted nutrients and feed costs. The continuing trend to increased litter size and intensive production schedules places biological demands on the sow that make high performance difficult to obtain and maintain. An increase in the number of pigs marketed/sow/year through improved sow nutrition would result in increased profitability by allocating fixed sow costs over more pigs. However, increased productivity can decrease longevity in the herd without proper nutrition. Studies indicate that a sow must complete at least 3 parities before reaching a positive net present value (the point when she has covered purchase price and feed costs; Stalder et al., 2000, 2003).

The research committee of the National Pork Board (NPB) has identified improvements in sow nutrition as an area needing further research. The current S-1061 committee meets yearly with members of the American Feed Industry Association, the NPB, and representatives from large feed companies to survey their assessment of research priorities. The specific research objectives that we have chosen result directly from those meetings. All segments of the industry recognize sow productivity and nutrition as extremely important factors affecting profitability in swine production systems. In fact, sow longevity is one of the key research areas identified by the NPB for the use of the commodity checkoff monies that are appropriated for research. Although progress has been made in sow nutrition in the last 30 years, there is still a dearth of information relative to specific nutrient requirements of the prolific and high milk-producing sows used today. Further research is greatly needed to completely define the levels of various nutrients necessary for optimizing reproduction and lactation while minimizing nutrient excretion.

Importance of the work: It is extremely important to conduct research that provides solutions to potential sow nutrition and production problems and the impact that concentrated production systems have on the environment. Societal perspectives and governmental regulations place extreme pressures on our production systems. Solutions to these issues must be provided so that swine production, a critically important component of agricultural productivity, will remain, and that it will continue to be an economically viable opportunity for our work force.

Technical feasibility of the research: The original Southern Multi-State Research Group (S-145) and the current group (S-1061, previously S-1044, S-1012 and S-288) have made significant contributions in obtaining new knowledge and creating a better understanding of the nutritional needs of sows to improve reproductive efficiency. This Technical Committee has used the approach of: 1) defining high priority research areas after meeting with stakeholders, 2) developing common protocols that are followed by all participating stations [with certain aspects rigidly followed by all participants and other aspects having flexibility for individual stations], 3) pooling the data, 4) drawing conclusions, 5) publishing the pooled results as abstracts at professional meetings and in scientific journals and 6) dissemination of research results through extension programming, trade magazines, and direct producer contact. Since its inception, the Committee has published 18 refereed publications, 1 conference proceedings, 24 abstracts, and 1 extension publication. These publications are the direct result of the collaborative research efforts of the Southern Multi-State Research Group. Also, in collaboration with the NCCC-42 Committee, the Committee has published one book entitled "Swine Nutrition" (now in its second edition) and four book chapters. Committee members have been asked to speak at a number of producer and industry conferences to discuss research results. The S-1012 Committee was nominated by the Southern Region Departments Heads for the NASULGC award for Regional research. Over the last 20 years, participants in the Committee have clearly demonstrated that they can successfully collaborate in multi-state research. In addition, we meet annually with the NCCC-42 Committee, which is an informational exchange group working on swine nutrition. We have opened our objectives to their participation as well as participation by other institutions.

Justification for a multi-state approach: Sow research is well suited to a regional approach for three major reasons. First, in reproductive studies, large numbers of animals are required to generate meaningful data; individual experiment stations often do not have sufficient sow numbers for sow research. Progress in sow nutrition and management research is hampered by the large variation among sows in economically important reproductive traits (Aaron and Hays, 1991). In a summary of 7,925 farrowings in five herds, the coefficients of variation were 26-33% for total and live pigs farrowed and 36% for pigs weaned (Aaron and Hays, 2004). In contrast, the coefficients of variation for growth rate and feed efficiency were 5-8 and 4-7%, respectively, for pens of growing and finishing pigs. The number of replications needed to detect a 10% difference in litter size at birth and at weaning, at an 80% success rate and a 5% probability level, is 99 and 193 sows per treatment, respectively. Thus, it is difficult for individual experiment stations to generate the number of observations needed to reach statistically significant conclusions. Second, pooled results from several experiments conducted with a common protocol but under different environments provide valuable information from which broad inferences can be drawn, and more robust recommendations can be made. A further advantage of a multi-state approach is that the combined experience and expertise of several swine nutritionists can be focused on a few high-priority objectives. Also, a planned annual meeting provides opportunities to discuss new and old research findings.

Goals and impacts of the current research: The primary goal of this proposed project is to improve the reproductive performance of sows while increasing their retention in the herd, enhancing offspring robustness, and minimizing sow nutrient excretion. This research will include studies to evaluate sow boron requirements, phytogenic feed additives, and gestational phase feeding to determine the effects on reproductive efficiency, including offspring growth, in an attempt to improve the economic return to swine producers. Boron is an inadequately-examined mineral in food animal production. Outcomes from the previous S-1061 project have begun to demonstrate the value of phytogenic feed additives such as essential oils in sow diets as a means to reduce the overall reliance of pork production on antibiotics (another current societal issue for animal production) through improved sow health and performance and subsequently enhanced offspring performance. Finally, phase feeding has long been used in post-wean diets as a means to more closely meet changing nutrient demands, limit excess protein excretion, and reduce diet costs but there is little data on this feeding strategy for sows. As sow health and productivity is increased by success in any of these objectives, there is potential improvement in enterprise profitability. The results also will demonstrate responsiveness to societally-important issues of waste management and the environment as well as concerns about antibiotic use in animal production.