From Fertility to Foal: considerations for digestive tract health

  The success or failure of any breeding program is dependent on the nutritional status and digestive tract health of foals, mares, and stallions alike. Although this aspect of the operation is often overlooked, it is only by ensuring that these considerations are optimised that foals are given the best chance to survive and thrive, from birth through weaning and on to sale.       A weighty issue    There exists surprisingly little research surrounding the nutrient requirements of the breeding stallion. This may be in part complicated by the great variation in activity; some stallions may serve several mares a day during peak periods in the breeding season, while others may serve only that number in a year. Other influencing factors may include temperament, management routine, and competitive activities. However, it is generally agreed that energy demands are indeed above maintenance levels, and according to various National Research Council studies it has been suggested that active stallions require approximately a third more digestible energy than their non-breeding, sedentary counterparts.      Research in other species has shown that a body condition that deviates greatly from the ideal can be associated with an increased risk of infertility (Nguyen et al. 2009). Nutritional content is also of great importance, with zinc and omega-3 fatty acids playing important roles in sperm motility, mobility, and viability.     Extremes in body weight and condition can also affect the fertility of broodmares. Low levels of body fat in mares can inhibit or delay ovarian activity, and obesity is often associated with insulin resistance (equine metabolic syndrome, or EMS), which can also disrupt cyclicity. Gentry et al. (2002) found that mares with a body score of 3-3.5 demonstrated a longer anaestrus than mares with a good body score (eg., 5) (Henneke et al. 1983) and was accompanied by lower plasma leptin, prolactin, and insulin-like growth factors.     It would therefore be sensible to carefully manage the weight and condition of both broodmares and stallions to optimise breeding potential.    Safely improving body condition and weight    For horses struggling to maintain ideal body condition it is important to assess forage intake and quality, and to also increase concentrates. Energy-dense grains and fats are often employed in these situations; however, caution must be taken to avoid the digestive tract issues these can cause.     Adding fat-fortified feeds to the diet, or top dressing fats or oils, can be an effective way to increase caloric intake. However, oils can pose a palatability issue. For a significant caloric contribution, somewhere between 200-500 ml/day of vegetable oil would be required. This would also increase the need for additional vitamin E and selenium to counteract the greater antioxidant need of a horse on such levels of supplementation.     The horse is naturally limited in its capacity to digest large volumes of starch, so concentrations should be limited to about 2g starch/kg body weight per meal, which equates to 0.2% starch or 1.4kgs of grain per meal. Anything over this risks starch bypass through to the large intestine, which can cause a bacterial inversion and ultimately a range of issues from poor feed absorption and inflammation to colic and laminitis.         While it is prudent to ensure that a diet is appropriate both in volume and quality, the health of the digestive tract itself can sometimes be overlooked.  Optimal absorption can only be maximised when the mucosal surface of the tract and its vascular supply is healthy, the structure facilitates effective nutrient uptake, and the transit rate allows adequate time for digestion.     Other factors known to affect fertility and gestation can include naturally occurring contaminants found in feed, bedding, and housing. It has been well established that exposure to toxins produced by moulds and yeast can have detrimental effects on many biological systems. Of particular interest to breeders are mycotoxins, such as ergotalcaloids (found in some species of grass) and zearalenone (occurring in cereals). Zearalenone disrupts the oestrous cycle leading to lower conception rates, and ergotalcaloids can induce late gestation fetal loss and placental abnormalities. Mycotoxin binding agents can be a beneficial addition to a broodmare’s diet in a bid to combat mycotoxicosis. Biological products such as yeast cell wall, containing polysaccharides such as glucan or mannan, are emerging as potent adsorbers, with multibinding properties to numerous chemically different mycotoxins (Diaz & Smith, 2005).     Clearly, risk management should be applied at all levels of the feed production and manufacture chain to minimise contamination. Correct storage and regular quality assessment are paramount but the addition of a mycotoxin absorbent to the diet is also likely to be beneficial.    Nutritional demands of the pregnant mare     The nutrient and energy requirements of the pregnant mare begin to increase from month five of gestation (as placental tissues significantly develop). Consequently, a carefully devised diet containing adequate protein, vitamins, and minerals (major and trace) is imperative.     The pregnant mare’s caloric intake should also be increased and, depending on climate, housing, etc., feed volume may need to be increased by up to 30% by the end of gestation. This may be complicated during late gestation when the foal occupies an increasing proportion of the mare’s abdominal cavity, thus making large volumes of feed difficult to ingest.     The foal will gain approximately 80% of its birth weight during the last trimester, and the most rapid growth period will be in the few days before or after birth (Staniar et al. 2004). Ensuring optimal gastrointestinal support helps to safeguard the health of both the mare and her foal.      Colostrum IgG transfer crucial to foal health    The passive transfer of maternally derived immunoglobulins (predominantly IgG) to the newborn foal should occur via the mare’s colostrum within the first 1-8 hours after parturition. The immunoglobulin content of colostrum drops to 10-20% of levels recorded following parturition, and after the first 24 hours of life “gut closure” in the foal occurs. This means that the large IgG molecules can no longer be absorbed. Failure of passive transfer (FPT) leaves the foal particularly susceptible to bacterial infections, septicaemia, enteritis, pneumonia, and even death. Insufficient IgG transfer can occur for a variety of reasons, from premature birth, loss of colostrum due to lactation prior to parturition, to neglect or death of the mare. Another common reason for FPT is inadequate levels of IgG in the mare’s colostrum.     Dietary supplementation of certain nutrients has been shown to have a beneficial effect on colostrum IgG levels in numerous species (Krakowski et al. 1999, 2002, Khalkhane et al. 2013). In a pilot study (Carter & Pelligrini, unpublished) carried out on three thoroughbred breeding farms in the US, 26 broodmares were randomly placed into two groups. The experimental group received a polar lipid/beta glucan-based supplement 90 days prior to foaling, while the second group served as a control. The supplement, although primarily used to support the health and functioning of the gastrointestinal tract, also imparts immunomodulatory properties.     Adequate levels of IgG are accepted as between 4000 – 6000 mg/dl colostrum. The broodmares receiving the supplement reported a 97% higher IgG concentration in the colostrum (ave. 14038 mg/dl) when compared to the control group (ave. 7078 mg/dl). For broodmares with a history of poor colostral IgG concentrations, additional support may help to ensure a good transfer of immunity.     Supporting nutrition for lactation     Lactation is very demanding nutritionally for the broodmare, and it is well established that nutritional status and milk yield and quality are linked. This ultimately influences the foal’s growth rate, condition, and body weight. Within the first 30 days of lactation mares can produce up to 14kgs of milk a day, with a calorie content of 500 kcal/kg. Further, it takes up to 6-8 weeks before the hindgut of the foal is functional enough to absorb extra nutrition from non-milk sources. Balanced nutritional intake in the mare including adequate protein, calcium, and phosphorus is crucial, as is ensuring that the digestive tract is able to maximise uptake and absorption. Increased volumes of feed, however, can present a risk in itself, so smaller, more frequent feedings can help moderate the transit rate and ensure complete digestion.     Foal heat occurs at 14 days post foaling, and then at 22 day intervals. From a commercial aspect, and due to constraints of the breeding season, mares are often put back into foal as soon as is safe to do so; thus, returning fertility is paramount. It has also been shown that mares who foal in poor condition or who lose weight rapidly when lactating have reduced reproductive efficiency (Heneke et al. 1981). Meanwhile, R.M. Jordan (1982) found that if mares who foaled in poor condition were allowed to gain weight during lactation their conception rates were unaffected. Regardless, it is obvious that maintaining a healthy weight throughout gestation and lactation is always preferable to trying to rectify a problem that has developed in the process.    Development of the gut microbiome and common risks in the foal    By three months of age, the foal will have relied on the mare’s milk as a supply of energy and nutrients, again highlighting how the broodmare’s own nutrition is crucial. Prior to birth the foal’s gastrointestinal tract is relatively free of bacteria and microbes. After birth, it rapidly populates and is an important event contributing to the foal’s health and development (Julliand, 1992). While more research is warranted to establish how this can be further supported, it is clear that the health of the microbial ecosystem in the foal’s hindgut is integral to its ability to go on to absorb and digest certain feedstuffs and for its general wellbeing.       Digestive issues can be commonplace in the young foal. Gastric lesions in particular have been deemed common in foals under 10 days of age, and these foals often lack overt symptoms (Murray et al. 1990).  Diarrhoea is often associated with the mare’s first foal heat or during adaptation to other sources of food but is usually self-limiting. However, other causes, whether infectious or not, should not be ruled out. Rotavirus, Salmonellosis, Clostridium difficile, and Lawsonia intracellularis can all pose significant challenges to the foal. Appropriate veterinary treatment combined with gastrointestinal support can help promote effective recovery.     Optimal nutrition and gastrointestinal health in the broodmare, stallion, and foal is of primary concern for breeders. It warrants careful planning and consideration, with which many digestive issues can be limited or avoided while maintaining peak condition, weight, fertility, and overall health.               FJK 9 January 2018 3:10a -- re-looked at 11 January 2018 3:10a    Diaz DE, Smith TK. Mycotoxin sequestering agents: Practical tools for the neutralisation of mycotoxins. In: Diaz DE, editor. The Mycotoxin Blue Book. Nottingham, United Kingdom: Nottingham University Press; 2005. pp. 323–339.    Gentry LR, Thompson DL Jr, Gentry GT Jr, Davis KA, Godke RA, Cartmill JA. (2002) The relationship between body condition, leptin, and reproductive and hormonal characteristics of mares during the seasonal anovulatory period. J Anim Sci. 80(10):2695-703.    Henneke DR, Potter GD, Kreider JL. (1981) "Rebreeding efficiency in mares fed different levels of energy during late gestation." In: Proceedings of the 7th Equine Nutrition and Physiology Society. Warrentown, Virginia. pp. 101-104.    Henneke DR, Potter GD, Kreider JL, Yeates BF. (1983) Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J. 15(4):371-2.    Jordan RM. (1982) Effect of weight loss of gestating mares on subsequent production. J. Anim. Sci. 55 (Suppl 1):208.    Julliand V. (1992) Microbiology of the equine hindgut. 1. European Conference on the Nutrition of the Horse. Pferdeheilkunde, sonderausgabe, pp 42-47.    Khalkhane AS, Abbasi K, Zadeh FS, Arian AH. (2013) Effect of dietary beta-glucan supplementation on humoral and cellular immunologic factors in lambs. Global Veterinaria, 11, 38–43.    Krakowski L, Krzyzanowski J, Wrona Z, Siwicki AK. (1999) The effect of nonspecific immunostimulation of pregnant mares with 1,3/1,6 glucan and levamisole on the immunoglobulins levels in colostrum selected indices of nonspecific cellular and humoral immunity in foals in neonatal and postnatal period. Vet Immunol Immunopathol 68:1–11.    Krakowski L, Krzyzanowski J, Wrona Z, Kostro K, Siwicki AK. (2002) The influence of nonspecific immunostimulation of pregnant sows on the immunological value of colostrum. Veterinary Immunology and Immunopathology, 87, 89–95.    Murray MJ, Murray CM, Sweeney HJ, Weld J, Digby NJ, Stoneham SJ. (1990) Prevalence of gastric lesions in foals without signs of gastric disease: an endoscopic survey. Equine Vet J. 22(1):6-8.    Nguyen RH, Wilcox AJ, Skjaerven R, Baird DD. (2007) Men's body mass index and infertility. Hum Reprod. 2007 22(9):2488-93.     Scott Carter, PhD and Franklin L. Pellegrini, DVM. Effect of Adding SUCCEED™ to the Diet of Pregnant Mares 90 Days Pre-Foaling, unpublished.     Staniar WB, Kronfeld DS, Treiber KH, Splan RK, Harris PA. (2004) Growth rate consists of baseline and systematic deviation components in Thoroughbreds. J Anim Sci. 82(4):1007-15.        From Fertility to Foal     Considerations for Digestive Tract Health    Emma Hardy, PhD    

By Emma Hardy, PhD

The success or failure of any breeding program is dependent on the nutritional status and digestive tract health of foals, mares, and stallions alike. Although this aspect of the operation is often overlooked, it is only by ensuring that these considerations are optimised that foals are given the best chance to survive and thrive, from birth through weaning and on to sale.   

A weighty issue

There exists surprisingly little research surrounding the nutrient requirements of the breeding stallion. This may be in part complicated by the great variation in activity; some stallions may serve several mares a day during peak periods in the breeding season, while others may serve only that number in a year. Other influencing factors may include temperament, management routine, and competitive activities. However, it is generally agreed that energy demands are indeed above maintenance levels, and according to various National Research Council studies it has been suggested that active stallions require approximately a third more digestible energy than their non-breeding, sedentary counterparts.  

Research in other species has shown that a body condition that deviates greatly from the ideal can be associated with an increased risk of infertility (Nguyen et al. 2009). Nutritional content is also of great importance, with zinc and omega-3 fatty acids playing important roles in sperm motility, mobility, and viability.

Extremes in body weight and condition can also affect the fertility of broodmares. Low levels of body fat in mares can inhibit or delay ovarian activity, and obesity is often associated with insulin resistance (equine metabolic syndrome, or EMS), which can also disrupt cyclicity. Gentry et al. (2002) found that mares with a body score of 3-3.5 demonstrated a longer anaestrus than mares with a good body score (eg., 5) (Henneke et al. 1983) and was accompanied by lower plasma leptin, prolactin, and insulin-like growth factors.

It would therefore be sensible to carefully manage the weight and condition of both broodmares and stallions to optimise breeding potential.

Safely improving body condition and weight

For horses struggling to maintain ideal body condition it is important to assess forage intake and quality, and to also increase concentrates. Energy-dense grains and fats are often employed in these situations; however, caution must be taken to avoid the digestive tract issues these can cause.

Adding fat-fortified feeds to the diet, or top dressing fats or oils, can be an effective way to increase caloric intake. However, oils can pose a palatability issue. For a significant caloric contribution, somewhere between 200-500 ml/day of vegetable oil would be required. This would also increase the need for additional vitamin E and selenium to counteract the greater antioxidant need of a horse on such levels of supplementation.

The horse is naturally limited in its capacity to digest large volumes of starch, so concentrations should be limited to about 2g starch/kg body weight per meal, which equates to 0.2% starch or 1.4kgs of grain per meal. Anything over this risks starch bypass through to the large intestine, which can cause a bacterial inversion and ultimately a range of issues from poor feed absorption and inflammation to colic and laminitis.    

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