Role of Essential Fatty Acids in Transition Sow Diet

Introduction

On average, piglet livability in Europe is 83%, ranging from 70% to 90%. It is determined by the number of still births and pre-weaning mortality in a given litter. With the increasing litter size, piglet survival is a persistent challenge to pig producers. This calls for a feeding and management strategy to improve nutrition and wellbeing of the sow in the transition phase covering late gestation, farrowing, lactation and breeding.

The transition period involves substantial metabolic dynamics in the high prolific sow during which she becomes catabolic, mobilising her body fat and protein reserves in order to meet increased nutrient demands for high priority of greater foetal growth as well as colostrum and milk production. Like with all other nutrients the sow gets into a negative balance of essential fatty acids at this crucial stage. Excessive loss of body condition affects lactation and reproductive performance.

Although a number of studies have shown in the past that supplementing sow diets during late gestation with fat can improve piglet condition at birth and growth performance prior to weaning, little emphasis has previously been placed on the type of fatty acids in the diets and which specific ones are involved. This is in contrast to the development of the concept of ideal protein in pig nutrition which has led to precise amino acid supplementation in pig feed to meet the exact nutritional requirements at each stage of growth and reproduction. Nutritionists are only beginning to consider in detail the essentiality of fatty acids in the same context. Indeed, the importance of fatty acids with specific roles in maintaining correct metabolic functions is emerging beyond the conventional consideration of fat simply as a source of energy to manipulate the caloric density of pig diets.

Lipids and reproductive hormones

In the last decade research into fat nutrition in dairy cows pointed to the fact that fats may have profound influence on health and reproduction, during transition period. The effects include increasing the number and size of ovulatory follicles, plasma concentration of progesterone, and decreasing the secretion of prostaglandins, leading to enhanced lifespan of the corpus luteum and improved fertility (Staples et al., 1998). Many of these outcomes are related to increased intake of the essential fatty acids.

In a similar manner to dairy cows, sows could benefit from balanced fat supplementation during gestation, lactation and breeding. Docosahexaenoic acid (DHA) stimulates oestrogen and progesterone release and diminishes cortisol concentrations in oestrus. In contrast, Arachidonic acid, parent source of prostaglandins, negatively affects oestrogen production and promotes cortisol concentrations in oestrus reducing progesterone concentrations in general (Nemeth et al., 2017). A stable concentration of progesterone dominates the entire period of gestation to maintain the pregnancy while other reproductive hormones remain lower up until the last 2 weeks before expected farrowing. As farrowing approaches, production of prostaglandins kicks in which activates the regress of corpora lutea to terminate pregnancy, allowing the hormones that initiate the farrowing process to commence. Omega-3 fatty acids play a role in the production of progesterone while omega-6 fatty acids are associated with prostaglandins. There is therefore a need for commercial nutritionists to formulate diets to an optimal omega-6:omega-3 ratio (< 5) as well as to consider the absolute levels of omega-3 in the diet and the conversion efficiency of C18:3(n-3) to longer chain omega-3 fatty acids.

Essential fatty acids

Linoleic and linolenic acids have been regarded as essential fatty acids. However, it is the longer fatty acids synthesised from them that have profound biological effects. Arachidonic acid is derived from linoleic acid and eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids from α-linolenic acid. The conversion process lacks in the foetus requiring the unborn piglet to depend on maternal supplies of the longer chain omega-3 fatty acids.

Limited attempts have been made to design feeds with lipid compositions that fulfil sows’ metabolic needs for PUFA (polyunsaturated fatty acids) including a well-balanced ratio of omega-6/omega-3 FA. Sampels et al. (2010) observed in sows fed varying levels of fat during breeding and pregnancy that the transport of omega-3 PUFA from sow to piglet was greater via milk than via bloodstream in the uterus. Increased content of α-linolenic acid in sow’s feed led to an increased accumulation of the fatty acids, EPA and DHA in piglets’ liver and brain with the potential to improve hepatic function and neurological development.

Fat supplementation on sow and piglet performance

Rooke et al. (2001) showed from work with 100 sows that supplementation of salmon oil (1.65%) in the diet during pregnancy increased gestation length but reduced pre-weaning mortality of piglets (see figure below). They were more active after birth, exhibited more udder-seeking behavior and, most significantly, heavier at weaning. The significance of this observation of increased gestation period may result in greater energy reserves at birth that improves livability. Similarly with lambs, Capper and others (2006) reported that supplementation of gestating ewe diet with omega-3 fatty acids from fish oil at 4.5% improved lamb’s ability to rise up and suckle which could improve survivability.

Role of Essential Fatty Acids in Transition Sow Diet - Image 1

In other studies (Gabler et al. (2007) were able to demonstrate that prenatal exposure to n-3 PUFA could enhance intestinal glucose absorption in weanling piglets. The supply of glucose can improve energy availability to the enterocytes and the animal as a whole thereby enhancing immune competence.

Smits and colleagues (2011) carried out the first ever study to show that feeding sows 9g/day omega-3 PUFA from fish oil before farrowing and during lactation increased litter size in the subsequent parity independent of energy intake. This phenomenon could become increasingly important with advancing sow age because of a possible progressive reduction of body bioactive fatty acids pool over successive lactations according to Rosero (2016).

Hansen et al. (2012a) found a low piglet mortality of colostrum suckling piglets when sows were fed 4% caprylic acid + 4% fish oil. Caprylic acid has antibacterial and antifungal effects plus anti-inflammatory properties similar to those of EPA and DHA.

In 2013, Wilkinson and others working with gilts made corroborative observations as the above study by feeding tallow and fish oil extracts. On the other hand, they noted that supplementing diets enriched with omega-6 PUFA alone significantly compromised growth and performance and concluded that this type of fatty acid when fed beyond a certain level may have negative health effects when consumed over long period. Consequently, the data suggests that the type of fatty acid added to a pig diet could have a major influence on feed formulation with regards to post-weaning growth and performance checks. There may be a benefit for a balanced fat supplementation in the transition period.

Rosero and co-workers (2015) evaluated the effects of supplementing sow diets with linoleic acid and α-linolenic acid on milk composition to determine the balance of the essential fatty acids for sows nursing large litters. The un-supplemented sows exhibited pronounced negative balance of linoleic acid and α-linolenic acid which compromised sow fertility by reducing farrowing rate, increasing culling rates, and lowering numbers of pigs born in the subsequent litter. See figure.

Role of Essential Fatty Acids in Transition Sow Diet - Image 2

Later Rosero et al. (2016) in partnership with industry collaborator conducted a larger scale study involving 480 high producing sows to evaluate reproductive responses to linoleic and α-linolenic fatty acid supplementation. The supplementation resulted in rapid return to oestrus, higher retention of pregnancy and increased litter size in subsequent parities. They concluded that a minimum intake of 10g and 125g/day of α-linolenic and linoleic respectively should provide for more than 95% of modern sow’s requirements and achieve optimum reproductive efficiency through multiple mechanisms such as rapid return to estrus, high maintenance of pregnancy and large subsequent litter size in mature sows, that appear to be especially susceptible to essential fatty acids deficiency. In other instances, lower levels have been proposed. The inconsistencies could be due maybe to some interactive relationships among fatty acids or essentiality of others that are yet to be established such as EPA and DHA which are equally important.

A recent study (Jin et al., 2017) involving 80 multiparous sows was conducted to investigate the effects of dietary supplementation with palm oil; fish oil and soybean oil (3.8–3.9% of each in a diet) during late pregnancy and lactation on a number of parameters. They included reproductive performance, fatty acid composition of colostrum, milk and serum of the offspring. Fish oil supplementation increased litter size of weaker piglets than control. Fish and soy oils improved the weaning survival rate, litter weaning weight, litter weight gain and milk fat content.

The highest anti-inflammatory markers in the colostrum and milk in the above trial were associated with fish oil. As well, the most concentration of EPA and DHA were characteristic of fish oil supplementation. Overall the inclusion of fish and soy oils in the diets enhanced growth rate of piglets by increasing milk energy content. Fish oil in particular benefited the young pigs through improved omega-3 availability and immunoglobulin secretion. Rooke et al (2001) have recommended a feeding rate of 6g/sow/day EPA and DHA as optimal from 60 days of gestation.

From the above studies there is evolving compelling evidence linking fish oil with health and reproductive efficiency in breeding sows and immune functionality in piglets and weaners. Of particular interest is how the ratio of omega-6 and omega-3 and absolute amounts of these fatty acids can be related to breeding performance. The most well established sources of poly long chain omega 3 fatty acids EPA and DHA are marine fish and algea oils while omega-6 fatty acids are derived mainly from vegetables oils. Pigs may have the ability to convert lionleic acid into EPA and DHA fatty but the ability is variable and inefficient. Feeding preformed omega 3 fatty acids is therefore more effective.

Research by Decoux (2017) suggested that a transition complementary feed rich in lipogenic-glycogenic components that supports recovery from parturition; stimulates reproductive hormones and supplies nutrients essential to early embryo development could improve sow performance and piglet viability. Using a transition sow feeding program it has had been possible to achieve significant improvements in piglet birth weight of 11.5%.

Transition sow supplement

Considering the research information available (Rooke et al., 2001; Smits et al., 2011; Decoux (2017). and Rosero et al., 2016) so far, formulating a transition sow diet based on a lipogenic-glycogenic supplement with balanced omega-6 and omega-3 fatty acids may merit consideration in a high prolific sow feeding program. The starting point could be to offer at least 7.5g-EPA and DHA, 10g-α-linolenic acid and 125g linoleic/sow/day with a omega-6:omega-3 ratio of close to 7:1. Eastwood et al. (2014) reported greatest weaning weight and ADG from birth to weaning for piglets born to sows fed 5:1-9:1 ratios. Similar observations on average daily gain were made recently with 10:1ratio and linseed as source of omega-3 (Upadhaya et al. 2018). Korean researchers (Nguyen et al., 2019) have demonstrated that by reducing omega‐6: omega‐3 ratio from 17:1 to 5:1 through increasing omega‐3 in the diet they increased body weight, energy digestibility, and reduced the low‐density lipoprotein concentrations of blood in growing pigs.