Investigating the effects of a novel rumen-protected folic acid supplement on feedlot performance and carcass characteristics of beef steers.

Angus-crossbred steers (n = 180; 292 ± 18 kg) from a single ranch were used to investigate the effects of a novel rumen-protected folic acid (RPFA) supplement on feedlot performance and carcass characteristics. On d 0, steers were blocked by body weight to pens (5 steers/pen), and pens within a block were randomly assigned to dietary treatments (n = 6 pens/treatment): target intake of 0 (CON), 30 (RPFA-30), 60 (RPFA-60), 90 (RPFA-90), 120 (RPFA-120), or 150 (RPFA-150) mg RPFA·steer-1·d-1. Steers were weighed before feeding on d -1, 0, 55, 56, 86, 87, 181, and 182. Pen average daily gain (ADG), dry matter intake (DMI), and gain:feed (G:F) were calculated for growing (d 0 to 56), dietary transition (d 56 to 87), finishing (d 87 to 182), and overall (d 0 to 182). Liver and blood samples were collected from two steers/pen before trial initiation and at the end of growing and finishing. Steers were slaughtered on d 183, and carcass data were collected after a 48-h chill. Data were analyzed as a randomized complete block design using ProcMixed of SAS 9.4 (fixed effects of treatment and block; experimental unit of pen). Liver abscess scores were analyzed using the Genmod Procedure of SAS 9.4. Contrast statements assessed the polynomial effects of RPFA. Supplemental RPFA linearly increased plasma folate at the end of growing and finishing (P < 0.01), and linearly decreased plasma glucose at the end of growing (P = 0.01). There was a cubic effect of RPFA on liver folate at the end of growing (P = 0.01), driven by lesser concentrations for RPFA-30, RPFA-60, and RPFA-150. Growing period ADG and G:F were greatest for CON and RPFA-120 (cubic P ≤ 0.03). Transition period DMI was linearly increased due to RPFA (P = 0.05). There was a tendency for a cubic effect of RPFA on the percentage of livers with no abscesses (P = 0.06), driven by a greater percentage of non-abscessed livers in RPFA-30 and RPFA-60. Despite supplementing 1 mg Co/kg DM, and regardless of treatment, plasma vitamin B12 concentrations were low (<200 pg/mL), which may have influenced the response to RPFA as vitamin B12 is essential for recycling of folate.

Influence of dietary zinc concentration and supplemental zinc source on nutrient digestibility, zinc absorption, and retention in sheep.

The objective of this study was to assess whether supplemental Zn source or concentration would affect ruminant Zn retention and nutrient digestibility. Thirty-six weaned crossbred Polypay wethers, were sorted by BW to 3 periods and stagger started on a common diet (22 mg Zn/kg DM) for a 52-d depletion period. Day 52 BW was used to assign Zn treatments (3 lambs/treatment/period): no supplemental Zn (CON), or supplemental Zn (40 mg Zn/d) from Zn sulfate (ING; Zinc Nacional, Monterrey, SA, Mexico), Zn methionine (ORG; Zinpro 120; Zinpro, Eden Prairie, MN), or Zn hydroxychloride (HYD; IntelliBond Z; Micronutrients USA LLC, Indianapolis, IN). On day 53 (day 1 of Zn treatments), lambs were moved to metabolism crates for 10 d of adaptation and 5 d of total fecal and urine collection. Blood for plasma Zn analysis was collected on day 52 and day 68. Data were analyzed as a randomized complete design with fixed effects of treatment, period and the interaction, which was significant (P ≥ 0.19) for day 68 plasma Zn but was removed for all other variables. Contrast statements were used to separate treatment means: CON vs. ZINC (ING, ORG, HYD), ING vs. HYD, and ORG vs. HYD. Day 52 plasma Zn concentrations were similar when CON was compared with ZINC (P = 0.84), and when ING and ORG were compared with HYD (P ≥ 0.19). Dry matter and neutral detergent fiber digestibility were lesser in ORG compared with HYD (P = 0.05) and organic matter and acid detergent fiber digestibility tended (P ≤ 0.08) to be lesser in ORG compared with HYD. Intake and fecal excretion of Zn was lesser, while apparent absorption of Zn was greater, in CON compared with ZINC (P ≤ 0.001). Zinc retained as a percent of Zn intake was greater in CON compared with ZINC (P = 0.001). Zinc retained (mg/d) was similar in CON compared with ZINC (P = 0.58) and when ING or ORG were compared with HYD (P ≥ 0.83). There was a treatment × period interaction for day 68 plasma Zn where treatments did not differ for periods 1 and 3 but ORG lambs had increased plasma Zn in period 2 compared with other treatments (P = 0.02). Lambs receiving no supplemental Zn had increased apparent absorption, suggesting Zn absorption may be upregulated in these lambs. Similarities in Zn retention across treatments suggests Zn requirements of these lambs were met regardless of supplementation concentration or source. Nutrient digestibility was improved in HYD lambs compared with ORG, and further work is needed to clarify the influence of supplemental Zn source on nutrient digestion.

The influence of supplemental zinc and ractopamine hydrochloride on trace mineral and nitrogen retention of beef steers.

The study objective was to determine whether N retention was improved with supplemental Zn above NRC concentrations with or without ractopamine hydrochloride inclusion. Angus crossbred steers (n = 32, 485 ± 26 kg BW) with Genemax gain scores of 4 or 5 were utilized in a 2 × 2 factorial arrangement (8 steers/treatment). Steers were blocked by BW to a finishing diet with 1 of 2 mineral supplementation strategies (ZNTRT), no supplemental Zn (analyzed 32 mg Zn/kg DM; CON) or supranutritional Zn (CON + 60 ppm ZnSO4 + 60 ppm Zn-amino acid complex; analyzed 145 mg Zn/kg DM; SUPZN), fed 56 days in pens equipped with GrowSafe bunks and assigned to ß-agonist (BA) supplementation strategies of 0 (NON) or 300 mg steer-1 d-1 ractopamine hydrochloride (RAC) fed the last 30 d before harvest. Initial 56-d ADG was not affected by ZNTRT (P = 0.66), but DMI was greater in CON vs. SUPZN (P < 0.01). On day 56 (day 1 of BA supplementation), steers (4 groups; 8 steers/group; 2 steers/treatment) were moved to metabolism crates and adapted for 10 d, followed by 5 d of total fecal and urine collection. Total retention of Zn, Mn, Fe, Cu, and N were calculated. Data were analyzed as a 2 × 2 factorial arrangement, with group as a fixed effect and the 3-way interaction of ZNTRT × BA × group as random. No interactions between ZNTRT and BA were noted for any data (P ≥ 0.19). Collection DMI did not differ among treatments (P ≥ 0.23); however, Zn intake was lesser in CON vs. SUPZN (P < 0.01). Fecal and urinary Zn excretion and Zn and Mn retention were lesser in CON vs. SUPZN (P ≤ 0.03); however, Zn retention was not different between NON and RAC (P = 0.43). Retention of Cu and Fe was unaffected by strategies (P ≥ 0.49). Urine output and urine N excretion were greater in NON vs. RAC (P ≤ 0.05). Nitrogen retention (as percent of N intake) was lesser (P = 0.05) in CON (40.0%) vs. SUPZN (44.3%) and lesser (P = 0.02) in NON (39.5%) vs. RAC (44.8%). Zinc and N retention were found to be positively correlated (r = 0.46, P < 0.01). Average daily gain and G:F across the 86-d trial were lesser in NON vs. RAC (P < 0.03). Overall, SUPZN appears to improve N retention, suggesting that increasing dietary Zn may be important for cattle growth beyond that induced by ractopamine hydrochloride.