Browsing by Author "Hansen, Stephanie Laura"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    The Effect of Dietary Manganese on Growth, Reproductive Performance, and Manganese Status of Beef Heifers
    (2005-10-19) Hansen, Stephanie Laura; Jerry Spears, Committee Chair
    Three trials were conducted to examine the effects of dietary manganese (Mn) on growth, reproductive performance, and Mn status of beef heifers. In Experiment 1, 80 Angus and Simmental heifers, approximately 10 mo of age, were supplemented with 0 (control), 10, 30, or 50 mg Mn/kg DM from MnSO₄ in addition to a diet containing 15.8 mg Mn/kg DM for 196 d. Performance of heifers was not affected by treatment. Liver Mn concentration increased (P=0.04) as dietary Mn level increased. Serum cholesterol was greater (P=0.001), in Angus compared to Simmental heifers for the 196-d period, but was not affected by treatment. Reproductive performance was not affected by treatment. Numerically, the number of heifers cycling at 12 mo of age, heifers bred at first service, and pregnancy rate was higher in heifers supplemented with 50 mg Mn/kg DM, compared to control heifers. In Experiment 2, 20 pregnant heifers from the control (n = 10) and 50 mg Mn/kg DM (n = 10) treatments were selected from Experiment 1 to continue on their dietary treatments through gestation and early lactation, to observe the effects of dietary Mn concentration on offspring. Serum cholesterol and whole blood Mn concentration of pregnant heifers for the 267 d study was not affected by dietary treatment. Calves born to control heifers were lighter at birth than those born to heifers receiving supplemental Mn (P = 0.02). Whole blood Mn concentration of calves at birth were lower (P = 0.01) in calves born to control heifers than those born to supplemented heifers. Seventy-one percent of calves born to control heifers exhibited some degree of superior brachygnathism. Experiment 3 used 70 Angus and Angus-Simmental cross heifers, approximately 9 mo of age, to examine the effect of dietary Mn source and level on growth, reproductive performance, and Mn status of beef heifers. Diets consisted of a corn-silage diet (analyzed 36 mg Mn/kg DM) supplemented with 0, 30 mg Mn/kg DM from MnSO₄ (SO₄), or 30 mg Mn/kg DM from a chelated Mn source (Mn Bioplex). Performance and liver Mn concentration of heifers was not affected by source or level of dietary Mn. Serum cholesterol was affected by a treatment by breed interaction (P = 0.06), with cholesterol in Angus heifers increasing over time in response to treatment. Whole blood Mn concentration was not affected by source or concentration of dietary Mn. Dietary Mn source and concentration did not affect the percent of heifers cycling. Pregnancy rate was affected by dietary treatment (P= 0.01). Fewer SO₄ heifers were bred than control (P = 0.01) and Bioplex heifers (P = 0.04). Results suggest that a diet containing 15.8 mg Mn/kg DM is sufficient for growth of beef heifers. Supplementation of Mn to the control diet tended to improve reproductive performance and was necessary to overcome signs of Mn deficiency in the offspring of the heifers.
  • No Thumbnail Available
    Nutritional Interrelationships between Iron, Copper and Manganese in Domestic Livestock
    (2009-03-04) Hansen, Stephanie Laura; William Flowers, Committee Member; Vivek Fellner, Committee Member; Jerry Spears, Committee Chair; Jack Odle, Committee Member
    Oftentimes the diets of cattle and pigs contain levels of iron well beyond the nutritional requirement of the animal. This superfluous iron may come from feedstuffs naturally high in iron, or from the consumption of soil, though bioavailability of iron from soil is unknown. Additionally, excess iron in cattle diets has been shown to negatively impact the metabolism of manganese and copper, though the molecular mechanism behind this interaction is unclear. The purpose of this research was threefold: 1) to determine the effect of ensiling on bioaccessibility of iron from soil contamination of corn greenchop, 2) to identify proteins important in iron metabolism in bovine and swine, and 3) to determine if these proteins are affected by dietary iron concentration. The results reported herein suggest that bioaccessibility of iron from soil contamination is greatly increased when soil undergoes a prolonged exposure to a low pH environment, such as that found with fermenting forages. These data indicate that very little iron from soil is available to the animal if no prior exposure to an acidic environment occurs. Also, for the first time we report that several proteins known to be essential to iron metabolism in rodents are present in bovine small intestine and liver. Specifically, the iron importer divalent metal transporter 1, the iron exporter ferroportin, and the multi-copper ferroxidase hephaestin were all present in bovine duodenum. In the bovine, reduced iron status, as induced by a primary deficiency of copper, resulted in increased gene expression of divalent metal transporter 1 and ferroportin in duodenum and decreased expression of the ferroportin regulatory hormone hepcidin and divalent metal transporter 1 in liver. Protein expression of ferroportin and hephaestin were also increased in duodenum due to reduced iron status. The addition of excessive amounts of iron to the diets of young calves also appeared to regulate protein expression of transporters important in iron metabolism. Specifically, high iron tended to decreased duodenal protein levels of divalent metal transporter 1 and reduced ferroportin protein levels, though no effect on hephaestin was observed. We also examined iron metabolism in the young pig, in order to examine the effect of an iron deficient diet on expression of these proteins. We found that hephaestin protein in the duodenum was lowered by feeding a high iron diet, and levels of both ferroportin and divalent metal transporter 1 tended to be reduced by high dietary iron compared to pigs fed a low iron diet. Additionally, we found that feeding a high iron diet to pigs negatively impacted liver concentrations of manganese. And feeding a high iron diet to either pigs or calves reduced duodenal concentrations of manganese, suggesting that high dietary iron reduces manganese absorption. Because high iron diets fed to both pigs and calves tended to reduce duodenal levels of divalent metal transporter 1, a protein known in rodents to transport both iron and manganese, it appears that the observed reductions in duodenal manganese concentrations may be a result of reduced transporter availability. Collectively, our data suggest that high dietary iron may negatively affect manganese absorption, and because the iron content of livestock diets is often high, further research is warranted.