In the hog industry it is imperative that we maximize the reproductive performance of sows in order to optimize pig flow and thus improve the economics of pork production. Modern sows are hyper-prolific, and due to a continual increase in litter sizes, the productivity of the pork industry is continually improving. This increase in piglet numbers, however, has several consequences on the survival and performance of piglets as well as on sow longevity.

Our overall objective was to improve the reproductive and productive functions of high producing sows. Specifically, we aimed to determine how altering the dietary fatty acid profile of sow diets would affect her whole body metabolism and her ability to provide nutrients and energy to her offspring by looking at milk energy output, piglet growth rate, sow feed intake and the role of leptin on feed intake and the responsiveness of sow adipose tissue to be mobilized when required.

Materials and Methods:
This experiment used five dietary treatments, each divided into a gestation and lactation ration. The diets were formulated to have a constant total fat concentration (5% crude fat), but varied in the ratio of n-6 to n-3 FA’s. The treatment groups consisted of a control (tallow), 3 diets with plant oil based n-6:n-3 ratios (10:1, 5:1, and 1:1) as well as a 5:1 fish oil diet.
Sows (n=150) were assigned to one of five test diets on d 80 of gestation and remained on these diets for three reproductive cycles. In order to determine the effects of dietary polyunsaturated fatty acids on high producing sows, any sow farrowing less than 11 piglets during cycle 3 was removed from trial, as were any sows that dropped below 10 nursing piglets throughout lactation. A set of sows for the 10:1(n=8) and 1:1 (n=7) diets had jugular catheters inserted on d 5 of lactation and underwent an epinephrine challenge in order to determine their ability to mobilize body fat, and a glucose challenge to determine the dietary effects on insulin sensitivity. Milk samples were collected on d 4 and d 16 of lactation and blood was collected for leptin analysis on d 5 and d 15.
Results and Conclusions:
Reducing the n-6:n-3 fatty acid ratio in sow diets had a wide range of effects on the reproductive performances of sows. A ratio of 5:1 increased piglet performance and sow feed intake. A plant based ratio of 1:1, and a fish based ratio of 5:1 lead to reductions in feed intake. Metabolic adaptations of the sows were measured in the 10:1 and 1:1 fed groups and results of this study show that sows fed at 1:1 ratio diet appeared to be in a state of negative energy balance relative to the 10:1 pigs throughout early lactation. There were no differences between diets on piglet performance, and thus on estimated milk energy and nutrient outputs. With the exception of the fish based diet, there were no major effects on piglet growth rates, indicating that sows will compensate for changes in feed intake through body fat mobilization, ensuring that their offspring are provided with an adequate supply of energy and nutrients for growth. This in turn would potentially have negative long term effects on the sow, in that if she is having to draw on her body reserves for each lactation, she will have a shortened lifespan in the herd and be more costly to a producer relative to a sow that does not have to draw on her own body to provide enough energy to her litter (or does so to a lesser extent). Combining the production data for all 5 dietary groups with the metabolic data of the 10:1 and 1:1 diet sows, it would appear that if the n-6:n-3 ratio becomes too low, negative effects on sow performance are seen, and a ratio of 5:1 appears optimal in terms of sow and piglet performance.
We observed optimal sow performance when diets with a n-6:n-3 fatty acids ratio of 5:1 were fed throughout gestation. This can be accomplished in a typical corn, soybean meal diet, or a wheat, barley based diet with added corn oil by adding about 0.5 % flaxseed oil.