MINERALS AND VITAMINS AS FACTORS AFFECTING REPRODUCTION IN RUMINANTS.
El-Talty, Y. I 1and Abdel-Ghani, A.A.2
1- Dept. of Anim. Prod., Fac. of Agric., Cairo University.
2- Dept. of Anim. Prod., Fac. of Agric., Minia University.
Nutritional factors needed for successful reproduction are the same as those needed for maintenance, growth, and lactation. They include protein, energy, minerals and vitamins. A deficiency or excess of any of these components, which is serious enough to affect reproduction, will also affect other physiological functions.
Lack of proper nutrition can reduce reproductive efficiency. Gross deficiencies or excess can be easily recognized and steps taken to correct the problem. Other imbalance in nutrition can be subtle and difficult to recognize. Diagnosis is sometimes difficult because reproductive symptoms associated with many deficiencies in nutrition are similar to symptoms caused by other disorders. It should also be recognized that nutrition is often a scapegoat, being falsely blamed for problems in reproduction that are caused by infection organisms or deficiencies in management.
There are no magic nutritional formulae that ensure efficient reproduction. If diets for animals are sufficient to meet their requirements, nutrition is not likely to limit reproduction. Most nutrition related reproductive problems result from their neglect or an overestimation of the nutritional value of the feedstuffs used in formulating diets.
Balakrishnan and Balagopal (1994) suggested that a mineral imbalance could be a cause of infertility in the repeat breeders. Requirements of most minerals are increased per unit of body weight by gestation, lactation, and growth. While gross deficiencies may reduce efficiency of reproduction, such deficiencies seldom occur in filed conditions. Mineral mixes containing calcium, phosphorus, iodized salt, and trace minerals are recommended in the nutritional management of animals for meat and milk production. If these minerals are supplied in sufficient quantities and ratios to meet the requirements for meet and milk production, it is doubtful that reproduction will be affected. If mineral mixes are not provided, some of the mineral content of natural feedstuffs must supply mineral needs. Reproductive problems have resulted in areas where deficiencies of specific minerals in the soil have reduced that found in natural feedstuffs. (Bearden and Fuquay, 1997)
Calcium deficiency is seldom a problem in ruminants. Animals have physiological control over both absorption and excretion of calcium. The effect of calcium deficiency on the development of fetal skeletal system might be more severe, except that the fetus can draw minerals from the skeletal system of the mother for development of its own system. If calcium reserves of the mother are not replenished between gestations, skeletal effects may be occur in later gestations. This is a potential problem but seldom occurs. Most defects in the development of the skeletal system of the fetus are due to the lack of vitamin D. (Bearden and Fuquay, 1997).
Wittkowski and Spann (1993) reported that feeding dairy cows according to requirements does not only include sufficient supply of energy and crude protein, but also major and trace elements. Undersupply of calcium and phosphorus influence infection of reproductive organs and lack of copper affect growth and causes silent estrus, while lack of manganese impairs fertility and zinc deficiency resulted in fertility disturbances. There can also be problems with oversupply of minerals.
Iodine deficiency has been reported to cause a number of disorders in reproduction. They include delayed development of the reproductive tract, irregular estrus, impaired fetal growth, and retained placenta. In males, iodine deficiency has been associated with low libido and poor semen quality. Toxic effects of too much iodine supplementation have been associated with abortion and fetal deformities. (Bearden and Fuquay, 1997).
A higher than normal incidence of retained placenta has been reported in cows in selenium deficient regions. Injection of selenium and vitamin E about two weeks before expected parturition will reduce the incidence of retained placenta. Vitamin E is needed for efficient utilization of selenium. High levels of selenium can be toxic, but specific adverse effects on reproduction have not been reported. (Bearden and Fuquay, 1997).
Supplementation of trace elements (Cu, Mn, Zn, Fe, Co and Se) have improved lambing rates in deficiency situations (Rattray, 1977; Robinson, 1983), but only for Se there is strong evidence that embryo survival during implantation is affected (Robinson, 1990). Salewski and Seegers (1994) reported that selenium supplementation improved insemination results and decreased fertility disturbances.
1-4. Other minerals.
Underwood (1981) reported that zinc deficiency is most apparent when cells are rapidly dividing growing or synthesizing. As a result reproduction may be impaired by inadequate zinc levels. Martin and White (1992) concluded that the specific effects of zinc deficiency on testis function were small. Most of the reduction in testis growth in rams fed a deficient diet was due to the fall in energy and protein intake caused by the loss of appetite. This led to a reduction in the frequency of GnRH pulses and to low rates of gonadotropin secretion by the pituitary gland. Saleh et al., (1992) reported that male goats had free access to water containing zinc sulfate had higher (P<0.05) semen volume, sperm concentration and sperm motility than control. The pH of semen was also higher for treated than for control animals. Wittkowski and Spann (1993) reported that lack of manganese impairs fertility and zinc deficiency resulted in fertility disturbances. There can also be problems with oversupply of minerals.
Bearden and Fuquay, (1997) observed that deficiencies of zinc in males have resulted in impaired spermatogenesis and testosterone production. Such deficiencies are not likely if trace mineralized salt is included in the diet or is available free choice. They mentioned that reduced calf crops have been reported in phosphorus deficient areas in the world. Low calf crop in phosphorus deficient cows appears due to irregular estrus patterns and periods of anestrus and delayed puberty. In addition, they reported that a deficiency of manganese is rare but has been associated with irregular estrus cycles and anestrus. While, copper and cobalt deficiencies have been associated with depressed estrus, low fertility and abnormal fetal development.
Fisher and MacPherson (1991) reported that cobalt deficiently in ewes resulted in produced fewer lambs and had more stillbirths and newborn moralities than cobalt sufficient controls. Lambs from deficient ewes were slower to start sucking. Cobalt supplementation in either the first or second half of pregnancy only did not fully alleviate these adverse effects.
Anke et al., (1993) reported that low bromine diet significantly decreased the success of first insemination and the conception rate and increased the abortion rate. Arnhold et al., (1993) found that vanadium deficiency adversely affected the success of first insemination, abortion rate, the number of matings per pregnancy and significantly shifted the sex ratio of kids to the female side. It is concluded that vanadium is essential for goats.
2. Effect of vitamins.
It is likely that all vitamins needed for growth and maintenance are also needed for reproduction. However, because of the availability in the usual animal feedstuffs, few have become sufficiently deficient to adversely affect production. (Bearden and Fuquay, 1997).
2-1. Vitamin A.
A deficiently in vitamin A can adversely affect reproduction in both males and females. It is necessary for the integrity of the germ cells in the seminiferous tubules in males. A deficiency can reduce or even stop spermatogenesis. In females, a deficiency of vitamin A lead to various problems including anestrus, repeat breeding, abortions, weak or dead offspring and retained placenta. Vitamin A can be stored in the liver. Therefore, a body reserve is available to prevent problems during short periods when the diet is deficient. Some researches reported impaired fertility in dairy cows and heifers on diets deficient in ß-carotene, (the plant source of vitamin A) even if the vitamin A statues of these animals are normal. Other researchers in similar experiments have seen no effect from diets devoid of ß-carotene. Likewise, supplementation of diets with ß-carotene has improved fertility in some cows but not in others. Various investigators reported that a specific function for ß-carotene in reproduction other than its role as a precursor for vitamin A. Therefore, conditions for a response need to be better defined before a general recommendation can be made. (Bearden and Fuquay, 1997).
Clinical signs of male infertility related to vitamin A deficiency include delayed onset of puberty (Bonsembiante et al., 1983), reduced testis size (Rao and Raja, 1977) and inferior semen characteristics (Kupfer et al., 1986). Advanced deficiency of vitamin causes degeneration of the somniferous tubules and testicular atrophy (Unni et al., 1983). Rode et al., (1995) reported that hypovitaminosis A significantly decreased paired testis weight, daily sperm production and epididymal sperm reserves, but did not affect daily weight gain.
2-2. Vitamin D.
Vitamin D is of interest in reproduction because of its role in absorption and retention of calcium and phosphorus. Principle effects of vitamin D deficiency have been related to development of the skeletal system of fetus. Rickets are common when a deficiency has existed during gestation. Vitamin D may influence the time of first postpartum estrus and calving interval. Vitamin D deficiencies do not occur unless animals are deprived of sunlight. Care must be exercised when supplementing diets with vitamin D, especially when animals are exposed to adequate sunlight. Vitamin D toxicity has occurred in farm animals from an excess of this vitamin. (Bearden and Fuquay, 1997)
Vitamin E called the “antisterility vitamin”. A deficiency resulted in death and resorption of fetuses. In male, degradation of the testis sometimes resulted in permanent sterility. The availability of vitamin E in cereal grains and forages makes a deficiency of this vitamin unlikely. Salespeople have promoted the use of vitamin E and wet germ oil, which is high in vitamin E, as a cure for both real and imagined reproductive problems. However, the need for this vitamin as a supplement has not been demonstrated. (Bearden and Fuquay, 1997).
Sing et al., (1989) recorded that vitamin E improved significantly the percent of live spermatozoa in Indian buffalo bulls. Velasquez-pereira et al., (1998) indicated that feeding vitamin E to bulls increased the percentage of sperm and improved the number of mounts in the first test and the time to first service in the second test.
Merino rams, were given an unsupplemented diet (controls), or diets supplemented with 2500 mg/kg vitamin E, 50 mg/kg selenium or 2500 mg/kg vitamin E plus 50 mg/kg selenium. Semen characteristics and acrosomal morphology were significantly better in the supplemented animals than in the controls. (Gokcen et al., 1990). Also, Laflamme and Hidiroglou (1991) reported that overall pregnancy rate was increased (P<0.05) with vitamin E supplementation, while age at first estrus, breeding and calving were not affected by supplementation with vitamin E.
Also, completely cottonseed and cottonseed meal are important sources of protein for ruminants, they contain the toxic polyphenolic pigment gossypol, which adversely affect reproduction capacity (Lindsey et al., 1980; Calhoum et al., 1990; Gray et al., 1990). Vitamin E feeding at a concentration of 4000 IU-bull-1d-1 reversed the negative effects of gossypol on reproductive measurements (Velasquez-pereira et al., 1998).
Most of other vitamins are either synthesized by the animals or are available in an adequate quantity in the usual feedstuff to prevent deficiencies. Although vitamin C is synthesized in the body and not required in the diet, supplemental doses have been beneficial in reducing fertility in males and females in some cases. Further research is needed on the mechanism of action and on conditions that suggest that this therapy may be beneficial. (Bearden and Fuquay, 1997).
Deshmukh and Honmode (1988) concluded that the supplementary vitamins improved vitality and resistance of spermatozoa, and vitamin C reduced slightly total sperm abnormalities.
Vitamin B12 is not available from plant sources. It s synthesized in the rumen in ruminants and provided through the addition of B12 supplement or meat products to the diet of simple stomached animals. (Bearden and Fuquay, 1997).
It is likely that all vitamins needed for growth and maintenance are also needed for reproduction. However, because of the availability in the usual animal feedstuffs, few have become sufficiently deficient to adversely affect reproduction. Requirements of most minerals are increased per unit of body weight by gestation, lactation and growth. While gross deficiencies may reduce efficiency of reproduction, such deficiencies seldom occur in field conditions. Mineral mixes containing calcium, phosphorus, iodized salt, and trace minerals are recommended in the nutritional management of animals.
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