Copper, zinc, and manganese in beef cattle production: effects of supplementation and source on reproduction, mineral status, feedlot performance, immunity, and carcass characteristics
Date
2004
Authors
Ahola, Jason K., author
Engle, Terry E., advisor
Burns, Patrick D., advisor
Seidel, George E., committee member
Whittier, Jack C., committee member
Field, Thomas G., committee member
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Abstract
Over a two-year period, crossbred mature beef cows ( n = 178, Year 1; n = 148, Year 2) and young females (n = 43 nulliparous heifers, Year 1; n = 37 primiparous cows, Year 2) grazing in eastern Colorado were used to evaluate the effects of Cu, Zn, and Mn supplementation and source on reproduction, mineral status, immunity, and cow and calf performance. Cow treatments included: 1) control (no supplemental Cu, Zn, or Mn); 2) organic (50% organic and 50% inorganic Cu, Zn, and Mn); and 3) inorganic (100% inorganic CuSO4, ZnSO4, and MnSO4) trace minerals. Heifer treatments included: 1) organic, or 2) inorganic trace minerals. Free-choice mineral feeders were used to provide current NRC-recommended concentrations of Cu, Zn, and Mn from 54 and 82 d (Year 1, heifers and cows, respectively) and 81 d (Year 2) prior to the average calving date of the herd through 110 and 119 d (Year 1, cows and heifers, respectively) and 135 d (Year 2) post-calving. Terminal steer and heifer calves from each year's calf crop were maintained on their appropriate pasture trace mineral treatments and had exclusive access to mineral treatments via creep feeders from approximately 95 d of age until weaning. After weaning, calves were grown and finished in a feedlot on the same pre-weaning trace mineral treatments. Performance, immune response, mortality, morbidity, mineral status, carcass traits, and longissimus dorsi fatty acid profiles were evaluated. In the grazing portion of the experiment, results indicate that trace mineral supplementation in cows and source in cows and heifers affected trace mineral status. Reproductive results were variable in heifers; however, in cows trace mineral supplementation improved pregnancy rate to AI compared to cows not supplemented with Cu, Zn, or Mn for more than 1 yr. Calf performance was greater in non-supplemented control calves vs. supplemented calves in both years, while source also affected calf performance but not consistently in both years. Trace mineral source did not affect calf performance in young grazing females. During the feedlot phase in Year 1, gain to feed ratio was greater in Inorganic vs. Organic calves in both the growing and finishing phases and greater in non-supplemented control calves vs. supplemented calves only during the finishing phase; however, gain to feed ratios were not affected by either supplementation or source in Year 2. Liver Cu and Mn concentrations were affected by supplementation, however immune response, morbidity, carcass traits, and longissimus dorsi fatty acid profiles were not different across treatments. Based on the reduced reproductive performance in non-supplemented cows, as well as literature indicating that Cu affects luteinizing hormone (LH) release, the effect of Cu status, supplementation and source on pituitary responsiveness to gonadotropin releasing hormone (GnRH) were evaluated using 12 multiparous, non-pregnant, non-suckling, ovariectomized Angus cows. After receiving 5 mg Mo/kg diet and 0.3% S during a 216-d Cu depletion phase, nine cows were considered Cu deficient (liver Cu concentrations < 30 mg Cu/kg) and were stratified based on age, BW, BCS, and liver Cu concentration and randomly assigned to treatments. Treatments included: 1) control (deficient Cu status; no supplemental Cu), 2) organic (adequate Cu status; 100% organic Cu, 10 mg Cu/kg diet), and 3) inorganic (adequate Cu status; 100% inorganic CuSO4 , 10 mg Cu/kg diet). By d 77 of the 159-d repletion phase all supplemented cows had adequate liver Cu, and liver Cu concentrations were greater in supplemented cows vs. non-supplemented controls, and this was maintained throughout the repletion phase. Beginning on d 99, cows were catheterized every fifth day and blood samples were collected at 15 min. intervals for 1 h prior to, and 4 h after, GnRH administration at low (0, 3, and 9 ug; experiment one) and high doses (0, 27, and 81 ug; experiment two) and analyzed for LH concentration. Copper status, supplementation, and source had no effect on pituitary sensitivity to GnRH (based on basal, peak, and total LH released at varying GnRH doses) or pituitary stores of LH.
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Subject
Trace elements in animal nutrition
Beef cattle -- Feeding and feeds
Beef -- Quality