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The breeding herd is the engine room of pork production: If it’s not performing optimally, it is difficult to produce the number of piglets required for sustainable pig farming. An effective breeding herd means that there is a high proportion of selected gilts entering the breeding herd, and those sows are retained as productive animals for as long as possible, maximising sow longevity. Research from the USA suggests that producers should aim for < 5% replacement rate before parity one and a parity distribution with more than 75% of sows staying in the herd beyond their third litter. However, currently the industry is only at 65% (Mote et al., 2008). Raising a gilt is a costly process due to the cost of feed, facilities, labour, vaccinations and other health strategies invested in her early development. Minimizing the number of gilts being introduced into the herd also reduces the risk of new diseases entering the herd from outside sources. The performance of parity five sows is typically still higher than parity one and two sows, so retaining these animals for longer is critical to effectively managing the cost of replacement animals. Investment in a replacement sow seldom reaches breakeven point until she has completed her third parity (Mote et al., 2008).
Sow death or early removal of sows from the herd is a significant financial burden and directly impacts farm profitability. Metafarms data from 2021 (Eckberg, 2022) indicated that sow deaths ranged from 5% to 35% across more than 400 farms surveyed, and that annual sow mortality has increased by 66% from 2012 to 2021 (8.2% to 13.6%). Assuming typical European production and feed costs, the death of a sow could result in losses up to €905/hd. For a 1,000-sow herd producing 30 pigs weaned per sow per year, 1% sow mortality would have a herd impact of €9,005 or €0.30 per pig produced. From the US study (Eckberg, 2022), while euthanasia due to leg weakness or prolapse were identified as the highest individual cause of death, over 50% of sows died from unknown causes. With the trend for hyper-prolificacy in breeding programs and the associated increase in metabolic stress, the modern sow is more susceptible to on-farm health challenges and other stressors than her counterparts 10 years ago. In particular, postpartum dysgalactia syndrome (PDS) is a multifactorial subclinical inflammatory syndrome associated with reduced feed intake and milking efficiency that is growing in prevalence, particularly as prudent antibiotic practices are implemented.
Kemper (2020) identified mycotoxins as one potential predisposing factor contributing to PDS. Mycotoxins are globally recognised contaminants in sow feeds and bedding (DSM Mycotoxin Survey, 2021). While severe mycotoxicoses resulting in sow death are not commonly reported, sub-acute exposure to mycotoxins are known to trigger a number of conditions that can lead to poor performance and reduced longevity of sows. Furthermore, as outlined in the ‘prepare’ pillar of the DSM Piglet Care program, effective preparation of the piglet starts with a healthy and robust sow, and managing mycotoxin risk in the sow can also improve piglet performance.
The wide-ranging effects mycotoxins can have in female pigs and the main organ groups that can be impacted by mycotoxins are shown in Figure 1.
Figure 1. The four main organs in sows that are affected by mycotoxins.
The liver has many functions, the key one being its role in detoxifying metabolites. Any impact on liver functionality could have wide ranging effects on animal health. Skiepko et al. (2020) identified that the mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) detrimentally affected the ultrastructure and histology of pig livers within one week of exposure. Similar work by Dolenšek et al. (2021) observed liver damage in pregnant gilts fed mycotoxins, as evidenced by an increased number of leukocytes (indicator of inflammatory processes) and apoptotic cells in the liver.
Mycotoxins are known to have general effects on reducing feed intake in sows and also direct effects on the developing piglets (Dänicke et al., 2007). Dänicke et al. (2007) was unable to determine which component had the greatest impact on the impaired piglet development – the decreased feed intake and therefore reduced nutrient supply to the piglets or the direct effects of the Fusarium mycotoxins on the developing piglets. Numerous studies in weaners and grower pigs have demonstrated a range of effects on gut function of mycotoxins (Akbari et al., 2017) but such studies are rarely conducted in sows due to experimental methodology constraints and animal ethic concerns. Studies in pregnant sows (Liu et al.,2017) identified that ZEN intake had a number of negative effects on microbiota, villus height and oxidative stress indicators. ZEN also decreased the prevalence of beneficial bacteria, Lactobacillus and Bifidobacterium spp. Expression of tight junction proteins was inhibited by either DON or ZEN, however when both mycotoxins were present together, the effect was even more pronounced (Liu et al., 2017).
Two key requirements for a successful pregnancy are:
1) the capacitation of oocytes to blastocysts, and
2) maintenance of the pregnancy hormone profile.
If there are delays to ovulation or oocyte development, the earlier implanted embryos elongate faster and occupy an uneven share of the uterine space with a larger placenta relative to the later embryos (Geisert and Schmitt, 2002 and Vallet et al., 2009) leading to uneven birth weights. The cleavage process and blastocyst formation was observed to be significantly affected ex-vivo by the presence of DON and ZEN (Malekinejad et al., 2007). ZEN is an analogue of estrogen and is therefore particularly implicated in many aspects of the development and functional disruptions of the reproductive system observed due to mycotoxins. In addition to bleeding in the ovary and uterine tissue due to effects of ZEN, Zhou et al. (2022) also observed negative alterations in the pregnancy hormone (progesterone) and in luteinizing hormone which may disrupt the farrowing process and initiate estrus in lactation.
Due to ZEN’s high estrogenicity, one of the few clearly visible signs of ingestion of ZEN by female pigs is the presence of a swollen vulva. Swollen vulvas have been reported in suckling pigs (Hennig-Pauka et al., 2018), evidence that ZEN can be transferred in-utero. A dose-dependent effect of ZEN on vulva size in gilts was observed as early as six-days after feeding of ZEN was initiated (Grenier et al., 2019). Zhou et al. (2022) also observed damage to the mammary epithelial cells of gilts when ZEN was ingested.
It is clear that mycotoxins can have a range of impacts across many different organs. As the resulting negative performance effects and impacts on sow longevity from mycotoxins may not be easily differentiated from other challenges on farm, understanding the occurrence of mycotoxins is a key element of managing the risk of potential contamination. The annual global DSM Mycotoxin Survey helps to create a detailed overview of mycotoxin risk in different feed raw materials by region across the major groups of mycotoxins including aflatoxins (Afla), fumonisins (FUM), zearalenone (ZEN), deoxynivalenol (DON), T-2 toxin (T-2), and ochratoxin A (OTA). The use of more sophisticated analytical technologies can also accurately quantify over 400 emerging mycotoxins and provide valuable insights into the potential risk of these fungal metabolites.
Some of the key observations from the latest DSM Mycotoxin Survey (2021) by geographic region are discussed below. In the Latin American countries, contamination of finished feed, wheat, corn, wheat bran and corn DDGS with DON was common. Corn and wheat samples analyzed were also found to contain FUM contamination. Although ZEN was detected in soybean meal and corn with a medium prevalence, the levels detected were found to be often quite high. In Sub-Saharan Africa, complete feed for swine was found to have the highest DON prevalence followed by wheat bran, which had the second highest level. A high prevalence of FUM was also found in finished feed and corn, which is often the case in this region due to the warm and moist climatic conditions. In North America, DON and FUM prevalence was high in the feed and raw materials analyzed (corn, finished feed and corn DDGS). Both finished feed and corn DDGS were also found to contain ZEN in this region. In Asia, all analyzed raw materials were contaminated with FUM including swine complete feed. DON was mainly found in complete feed and corn DDGS. Rice and corn DDGS were found to be contaminated with ZEN and complete feed was also contaminated with Afla. China was found to be the region with the highest risk, having high prevalence of ZEN, DON and FUM in the majority of raw materials analyzed including corn, soyabean, wheat, corn DDGS, rice, wheat bran and complete feed.
Across Europe, DON was routinely detected in all commodities including corn, rye, wheat, triticale and soybean meal and complete feed for swine. Interestingly, sows in straw-based systems are known to consume significant amounts of straw, and in the survey, straw was found to have a high prevalence of DON. ZEN was often found in corn, wheat, sugar beet, triticale, soybean meal and complete feed. While the impact of individual levels of mycotoxins on animal performance can be estimated from the literature, the impact of the synergistic effects when multiple mycotoxins are present at low levels is harder to quantify.
As mycotoxins have a wide range of differing physical and chemical properties, targeted strategies are required to reduce their impacts. As physical binding of some mycotoxins to inert materials can be reversed in the gastrointestinal tract, a more complete strategy for mycotoxin risk management is required. Irreversible deactivation of the mycotoxin through enzymatic cleavage is the innovative approach employed by DSM and authorized by the European Food Safety Authority (EFSA). Enzymes to deactivate fumonisins and trichothecenes combined with bentonite have been shown to be an effective way of reducing the direct impacts of mycotoxins. Plant and algal extracts offer additional support to the animal through improving gut integrity and liver support.
In summary, maximizing the performance and longevity of sows is essential to the sustainability of pork production. There are many factors that can impair lifetime sow performance, starting as early as the piglet period, and mycotoxins are implicated across many of these. Mycotoxins can impact many organs such as the liver, gut, uterus, ovaries, vulva and mammary glands. Surveys have shown widespread occurrence of mycotoxins across the globe and in all major feedstuffs and feeds fed to pigs. Effective mycotoxin risk management relies on irreversible deactivation of the mycotoxins coupled with compounds to support gut and liver function and can be achieved by the solutions offered in the DSM sow longevity program.
25 July 2022
Dr. Gannon is an Australian with a Bachelor of Agricultural Science (Honours) and a PhD in pig nutrition from the University of Sydney, Australia. Early in his career, Dr. Gannon worked as a research scientist for university and government organisations in the USA and Australia before moving to the commercial sector in a pig technical and nutrition role with the largest feed miller in Australia. After 10 years, Dr. Gannon started his own nutrition and research consultancy and had a part time appointment as a senior lecturer at the University of Queensland, Australia. In 2011, Dr Gannon joined BIOMIN and prior to the acquisition of BIOMIN by DSM in 2021, Dr. Gannon was the Regional Product Manager for Gut Performance in Asia. At DSM, Dr. Gannon continues his technical support of customers and sales colleagues and research interests as Global Swine Technical Manager.
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