369 Effects of Supplementing Sources of Zinc on Digestibility Parameters of Beef Steers

Abstract

Abstract Zinc (Zn) has numerous functions and many life-sustaining processes depend on the presence of Zn within the body. The objective of this study was to determine if apparent digestibility differed by Zn source. In this study, Angus steers (n = 12, 226 kg ± 16.17) underwent three isozinc treatments: Organic Zn glycinate, Inorganic Zn sulfate (ZnSO4), and Zn hydroxychloride (Phibro Animal Health, Teaneck, NJ). On day 1, steers were weighed, rumen fluid collected, liver biopsy performed, and blood collected. Steers were then placed in metabolism crates for a 4-day adaptation period. Each steer was assigned a source of Zn in a completely randomized design (4 steers/treatment). Steers had ad libitum access to hay and treatments were fed once daily. Treatments contained the assigned source of Zn 0.063 g/d, soybean pellets 0.063 g/d, ground corn 0.063 g/d, and molasses 0.2 g/d. Orts were quantified daily, and total fecal samples were collected and sampled daily at time of feeding (0600h) for 5 consecutive days (d 5 to d 10). On d 10, steers were removed from metabolism crates, weighed, rumen fluid collected, liver biopsy performed, and blood collected. Feed and fecal samples were composited for the entirety of the collection period. Each sample was dried, ground, and analyzed to determine DM, NDF, ADF, fat, protein, and mineral content. Data were analyzed using the proc mixed procedure of SAS. Digestibility results for Organic Zn, Inorganic ZnSO4, and Zn hydroxychloride were DM (70.74, 70.64, 72.46, respectively), NDF (75.98,76.03, 77.79, respectively), ADF (83.00, 82.47, 84.00, respectively), Fat (67.28, 66.00, 70.04, respectively), and protein (69.14, 68.56, 70.12, respectively). Hemicellulose and organic matter (OM) were calculated and determined, with digestibility of Organic Zn, Inorganic ZnSO4, and Zn hydroxychloride to be OM (74.13,73.50, 75.67, respectively), and hemicellulose (57.66, 59.27, 61.65, respectively). The results of proximate analysis reported digestibility of DM, NDF, ADF, fat, protein, OM, and hemicellulose, were not affected (P < 0.05) by treatment. Mineral analysis was performed by Inductively coupled plasma spectroscopy. Treatment did not affect Zinc liver concentrations. However, numerical differences indicate additional research is needed on rumen dynamics to fully understand the impact of mineral source within the animal, and ultimately its final environmental impact.