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EQUINE NUTRITION: JENQUINE- FEEDING FERTILITY
FEEDING FERTILITY
Of all the domesticated animals, horses have the lowest fertility rate. This may be because horses are selectively bred for their performance and conformation characteristics rather than their fertility.
© ARTICLE BY: DR JENNIFER STEWART BVSC BSC PHD EQUINE VETERINARIAN, CEO JENQUINE AND CONSULTANT NUTRITIONIST
Equine fertility is a tangled complex with a great variety of influencing environmental and management issues and the animals themselves.
What makes a fertile sperm? Like all cells, sperm need oxygen and, as a consequence, are faced with the oxygen paradox; oxygen is necessary for sustained life, but the waste products of using oxygen endanger the cell’ s survival. Both before and after ejaculation, sperm are exposed to the waste products of metabolism which limit the fertilization capacity of transported semen. These waste products, called reactive oxygen species or oxidants damage the delicate outer plasma membranes of the sperm( Figure 1,), reducing sperm motility, longevity and viability. Supplementing the diet with antioxidants helps prevent damage to the sperm and improves fertility.
Like all cells, sperm use oxygen and, as a consequence, are faced with the oxygen paradox- oxygen is necessary for sustained life, but waste products from oxidative processes can endanger the cell’ s survival. Stallion semen is damaged by oxidative stress during cooling and transport. The principle antioxidants are omega 3, vitamin E, selenium, vitamin C, zinc, copper, and manganese. Apart from vitamin C, the body cannot manufacture these and they must be supplied in the diet. Omega-3 oils are high in fresh grass and flaxseed, however grains and vegetable oils, including rice bran oil, are too low in omega 3 and too high in omega-6. Omega-3 increases sperm motility and concentration and decreases the number of abnormal sperm. Abnormal sperm are incapable of fertilising the egg. Some abnormalities are shown in Figure 2.
Dietary supplementation with natural antioxidants helps prevent oxidative damage. Lepidium meyenii( Maca)- a traditional Andean crop enhances fertility due to it’ s anti-oxidant activity. A 2018 study found that daily feeding of 20g maca powder for 60 days, improved motility and integrity and reduced oxidant damage to sperm. Vitamin E deficiency in stallions has been linked to the development of a higher number of abnormal sperm with poorer motility and supplementation improves both the total and progressive sperm motility of cooled semen. Vitamin A is also required for healthy spermatogenesis, protect against the development of abnormal sperm and assists motility. Zinc and selenium in combination with vitamin E enhance progressive motility, viability and morphology.
It takes about 60 days to make a sperm and to achieve the benefits of correct omega 3 intake, studies have found that the oil must be fed for at least 126 days.
FIGURE 1, Diagram representing a stallion spermatozoon( Image obtained from Amann & Pickett, 1987)
FIGURE 2, Some common sperm abnormalities: MD = mid-piece defect; LH = loose head; PD = Proximal Droplet; CRT = Curved Tail; HD = Head Defect; BT = Bent Tail
While no differences in sperm were found in trials feeding omega 3 oils for 84 days, after 126 days the sperm motility and velocity were higher. There was also a reduction in the number of abnormal sperm. Taking part in competitions has been shown to have no negative effect on semen quality – in fact, semen motility and total sperm count at most times during the breeding season were higher in stallions taking part in equestrian competitions than in stallions used for breeding only.
Australian Quarter Horse Association- www. aqha. com. au