The effect of dietary molybdenum and iron on copper status, puberty, fertility and oestrous cycles in cattle

Abstract

Two experiments were conducted to examine the effects of supplementation of a control diet of barley grain and barley straw containing 4 mg copper (Cu)/kg dry matter (D.M.) either with 5 mg molybdenum (Mo)/kg D.M. or with 500 or 800 mg iron (Fe)/kg D.M. on puberty, fertility and oestrous cycles of cattle. Puberty occurred normally in control, Fesupplemented and control animals on a restricted intake whereas it was delayed by 12 and 8 weeks respectively by Mo supplementation. This effect of Mo was not due to the low Cu status since this was equally low in the Fe-supplemented animals, nor was it due to the reduced growth rate since puberty occurred normally in control animals that had a similar live-weight gain. A significant reduction in the pulsatile release of luteinizing hormone was observed within 11 weeks of the Mo supplementation and before any of the other clinical signs were evident, suggesting that Mo may be affecting puberty by altering the release of luteinizing hormone either directly or indirectly.Mo supplementation significantly reduced the percentage conception rate to 12-33% compared with 57-80% in control and Fe-supplemented animals. This effect was not dependent on the rate of live-weight gain which was standardized across the different treatments at approximately 0 -6 kg/day. Within 12 weeks of the replacement of dietary Fe by Mo a lower conception rate occurred; replacing dietary Mo by Fe led to a normal conception rate within 12 weeks without any accompanying changes in Cu status or in the rate of live-weight gain. The plasma Mo concentrations, however, changed significantly during these alterations in dietary supplementation. The pre-ovulatory peak height of luteinizing hormone was significantly lower in animals on the Mo-supplemented diet compared with control and Fe-supplemented animals, but the administration of LHRH did not alter the conception rate.More Mo-supplemented animals failed to ovulate following prostaglandin induced synchronization in comparison with the other treatments, and by the 84th week a significantly greater number of Mo-supplemented animals (12/18) had become anoestrous compared with the other groups (2/30). Cu repletion of these anoestrous Mo animals for a period of 20 weeks did not result in resumption of normal oestrous cycles, but ovulation and oestrus were induced by progesterone and LHRH treatment. Results in the latter part of the study indicated that Mo caused superovulation.These data show that Mo supplementation delayed the onset of puberty, decreased the conception rate and caused anovulation and anoestrus in cattle without accompanying changes in Cu status or in live-weight gain. It is suggested that these effects of Mo are associated with a decreased release of luteinizing hormone that might be due to an altered ovarian steroid secretion.

Effect of copper and thiomolybdates on bovine theca cell differentiation in vitro

“…Therefore, a reduction in the production of androstenedione, as we have reported for TTM doses greater than 5, is likely to limit the production of oestradiol due to substrate limitation. The results of the present study are consistent with an effect of molybdenum-induced copper deficiency on the development of the preovulatory follicle, especially steroid secretion, and would therefore be expected to perturb both behavioural oestrus and ovulation to a varying degree, as has been observed in animals with molybdenum-induced copper responsive subfertility (Phillippo et al 1987, Du Plessis et al 1999a, 1999b. Further, it is well established that ovarian oestradiol plays a key role in controlling gamete transport and in priming the uterus for implantation, so that even if ovulation does occur, fertility rates are likely to be impaired if preovulatory oestradiol production is sub-optimal .…”

“…The effects of thiomolybdates in the whole animal have previously been shown to include reduced conception rates, anovulation and anoestrus, which were associated with a decreased release of LH (Phillippo et al 1987). The pre-ovulatory oestradiol peak is the endocrine signal responsible for induction of both behavioural oestrus and the preovulatory LH surge (Baird & McNeilly 1981) and the dominant follicle in ruminants is the source of over 96% of ovarian oestradiol secretion (Baird & Scaramuzzi 1976).…”

“…Molybdenum-induced copper depletion has been reported to reduce fertility with associated reduced conception rates, anovulation, anoestrus, decreased basal luteinising hormone (LH) levels, reduced peak surge of LH and a reduction in the number and frequency of LH pulses (Phillippo et al 1987). Du Plessis et al (1999a) have also shown that behavioural anoestrus occurs relatively quickly, within 6 weeks, in sheep fed a high molybdenum and sulphur diet, with true anoestrus occurring after a much longer supplementation time in the trial.…”

Assessment of Molybdenum Induced Alteration in Oxidative Indices, Biochemical Parameters and Sperm Quality in Testis of Wistar Male Rats

“…The diminished level of FSH and LH could be due to copper deficiency caused by molybdenum exposure (Phillippo et al, 1987). It was further elucidated by Haywood et al (2004) that reduced copper content make it unavailable for a copper-dependent enzyme peptidylglycine α-amidating mono-oxygenase (PAM) that appears to be crucial for the bioactivation of many peptide hormones, including FSH and LH.…”

Is there a relationship between serum minerals (Ca, Mg) and trace elements (Cu, Fe, Mn, Zn) at mating on pregnancy rates in fat-tailed Morkaraman sheep?*

“…Iron is a mineral acting as 1.66-2.22 g/dl in many areas of metabolism (Phillipo et al, 1987). However, Antunovic et al (2002) reported that although there was a marked increase in serum Fe levels depending on foetal growth particularly during the last trimester of pregnancy, while the levels decreased immediately before the lambing of Akkaraman ewes.…”