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 β-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.

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),

No abstract

Although cattle can synthesize vitamin C (VC) endogenously, stress may increase VC requirements above the biosynthetic threshold and warrant supplementation. This study investigated the effects of a VC injection delivered before or after a long-distance transit event on blood parameters and feedlot performance of beef steers. Fifty-two days prior to trial initiation, 90 newly weaned, Angus-based steers from a single source were transported to Ames, IA, USA. On day 0, 72 steers (356 ± 17 kg) were blocked by BW and randomly assigned to intramuscular injection treatments (24 steers/treatment): saline injection pre- and post-transit (CON), VC (Vet One, Boise, ID, USA; 5 g sodium ascorbate/steer) injection pre-transit and saline injection post-transit (PRE) or saline injection pre-transit and VC injection post-transit (POST). Following pre-transit treatment injections, steers were transported on a commercial livestock trailer for approximately 18 h (1675 km). Post-transit (day 1), steers were sorted into pens with one GrowSafe bunk/pen (4 pens/treatment; 6 steers/pen). Steers were weighed on day 0, 1, 7, 30, 31, 56 and 57. Blood was collected from 3 steers/pen on day 0, 1, 2 and 7; liver biopsies were performed on the same 3 steers/pen on day 2. Data were analyzed as a randomized complete block design (experimental unit = steer; fixed effects = treatment and block) and blood parameters were analyzed as repeated measures. A pre-transit VC injection improved steer average daily gain from day 7 to 31 (P = 0.05) and overall (day 1 to 57; P = 0.02), resulting in greater BW for PRE-steers on day 30/31 (P = 0.03) and a tendency for greater final BW (day 56/57; P = 0.07). Steers that received VC pre- or post-transit had greater DM intake from day 31 to 57 (P = 0.01) and overall (P = 0.02) v. CON-steers. Plasma ascorbate concentrations were greatest for PRE-steers on day 1 and POST-steers on day 2 (treatment × day; P < 0.01). No interaction or treatment effects were observed for other blood parameters (P ≥ 0.21). Plasma ferric-reducing antioxidant potential and malondialdehyde concentrations decreased post-transit (day; P < 0.01), while serum non-esterified fatty acids and haptoglobin concentrations increased post-transit (day; P < 0.01). In general, blood parameters returned to pre-transit values by day 7. Pre-transit administration of injectable VC to beef steers mitigated the decline in plasma ascorbate concentrations and resulted in superior feedlot performance compared to post-transit administration.

Thirty-six newly weaned, crossbred beef steers (323 ± 12 kg; SD) from a single-source were used in a 56-d study to examine the effects of a Saccharomyces cerevisiae fermentation product (SCFP; Original XPC, Diamond V, Cedar Rapids, IA) on total tract nutrient digestibility and response to a vaccination challenge. Twelve d after arrival, steers were blocked by body weight (BW) and randomly assigned to treatments: SCFP at 0 (CON), 14 (SCFP14), or 28 (SCFP28) g·steer-1·d-1. Steers were fed via bunks that measured individual intake and received ear tags (CowManager, Select Sires, Plain City, OH) that recorded rumination and activity. Body weights were collected on d -1, 0, 14, 28, 42, 55, and 56. Titanium dioxide was fed as an indigestible marker to all steers from d 12 to 27, followed by consecutive d fecal samples, for determination of total tract nutrient digestibility. On d 34, steers received a Mannheimia haemolytica vaccination (One Shot, Zoetis, Kalamazoo, MI) to induce an acute phase protein (APP) response. Blood was collected from all steers on d 34 (prior to vaccination) and 3, 6, 9, 11, and 14 d post-vaccination. Data were analyzed using Proc Mixed of SAS (experimental unit = steer; n = 12/treatment); the model included the fixed effect of treatment and block and the random effect of steer. Blood measures, ear tag, and dry matter intake (DMI) data for the 15-d vaccination period were analyzed as repeated measures. Contrast statements (CON vs. SCFP14; SCFP14 vs. SCFP28) were used to compare treatment means. Digestibility of dry matter and organic matter was greater for SCFP14 vs. SCFP28 (P ≤ 0.03). Steers fed SCFP14 exhibited greater crude protein digestibility compared to CON (P < 0.01). Steers fed SCFP14 exhibited greater DMI for 15 d post-vaccination (P = 0.02) and greater ADG from d 28 to 56 (P = 0.05) vs. SCFP28-fed steers. Post-vaccination, steers fed SCFP14 spent less time ruminating per kg of dry matter, neutral detergent fiber (NDF), and physically effective NDF consumed than CON or SCFP28 (P ≤ 0.07). Serum IL-8 and haptoglobin concentrations tended to be lesser for steers fed SCFP14 vs. SCFP28 (P ≤ 0.08). Ceruloplasmin concentrations were lesser on d 14 post-vaccination for steers fed SCFP14 vs. CON or SCFP28 (treatment × d; P = 0.004); there were no differences on other sampling days due to treatment. Although no overall performance benefit was noted, steers fed SCFP14 responded better to a vaccination challenge vs. SCFP28-fed steers.