Effect of increasing zinc supplementation on post-transit performance, behavior, blood and muscle metabolites, and gene expression in growing beef feedlot steers

Abstract

Fifty-four Angus-cross steers (297 kg ± 12) were stratified by body weight (BW) to pens (six steers per pen) to determine the effects of supplemental Zn on posttransit growth performance and blood and muscle metabolites. Dietary treatments started 25 d before trucking: control (CON; analyzed 54 mg Zn/kg DM), industry (IND; CON + 70 mg supplemental Zn/kg DM), and supranutritional Zn (SUPZN; CON + 120 mg supplemental Zn/kg DM). Supplemental Zn was bis-glycinate bound Zn (Plexomin Zn; Phytobiotics North America, Cary, NC). On day 0, steers were loaded onto a commercial trailer and transported in 18 h (1,822 km). Individual BW was recorded on days -26, -25, -1, and 0 (pre-transit), 1 (posttransit), 6, 27, and 28. Blood was collected on days -1, 1, 6, and 27. Longissimus thoracis biopsies were collected on days -1, 1, and 28. Daily individual feed disappearance was recorded via GrowSafe bunks. Data were analyzed using Proc Mixed of SAS with fixed effect of diet and steer as the experimental unit (growth performance, blood: n = 18 steers per treatment; muscle: n = 12 steers per treatment). Individual initial BW was used as a covariate in BW analysis. Contrast statements to test linear, quadratic, and Zn effects were used to analyze performance and blood parameters. Repeated measures analysis was used for posttransit DMI recovery and weekly posttransit DMI and Zn intake with the repeated effect of time. MetaboAnalyst 5.0 was utilized for statistical analysis of day 1 (off truck) muscle metabolites. Plasma Zn linearly increased due to Zn on days 1, 6, and 27 (P = 0.01), and off-truck (day 1) serum lactate increased over day -1 by 20%, 0%, and 20% in CON, IND, and SUPZN, respectively (Quadratic: P = 0.01). Muscle lactate tended to increase posttransit in CON and IND (P ≤ 0.07) but not SUPZN. Muscle metabolites relating to amino acid and nitrogen metabolism were increased in all treatments posttransit (P ≤ 0.02), and alanine-glucose cycle metabolites tended to increase in CON and IND (P ≤ 0.07). Steers supplemented with Zn recovered pretransit DMI quicker than CON (by d 2: P = 0.01), while IND had greater overall posttransit DMI than CON with SUPZN intermediate (P = 0.04), and Zn-fed steers had greater ADG posttransit (P = 0.04). Zinc supplementation mitigated muscle or serum lactate increases due to transit and increased posttransit ADG.

Keywords: behavior; cattle; feedlot; muscle; transportation; zinc.

Figure 1.

Recovery of dry matter intake (DMI) after transportation of beef feedlot steers. Pretransit DMI was used to calculate the percent of DMI recovery. CON: no supplemental Zn (n = 18 steers); IND: 70-mg supplemental Zn/kg DM (n = 18 steers); SUPZN: 120 mg supplemental Zn/kg DM (n = 18 steers). All supplemental Zn provided via Plexomin Zn (Phytobiotics, Cary, NC). ^a,bMeans with different superscripts in the same day are different (P ≤ 0.05).

Figure 2.

Average dry matter intake (DMI) for the 28 d following transportation of beef feedlot steers. CON: no supplemental Zn (n = 18 steers); IND: 70-mg supplemental Zn/kg DM (n = 18 steers); SUPZN: 120 mg supplemental Zn/kg DM (n = 18 steers). All supplemental Zn provided via Plexomin Zn (Phytobiotics, Cary, NC). Treatment × week: P = 0.94. ^a,bMeans with different superscripts are different (P ≤ 0.05).

Figure 3.

Average daily Zn intake of beef feedlot steers in the 28 d after transportation. CON: no supplemental Zn (n = 18 steers); IND: 70 mg supplemental Zn/kg DM (n = 18 steers); SUPZN: 120 mg supplemental Zn/kg DM (n = 18 steers). All supplemental Zn provided via Plexomin Zn (Phytobiotics, Cary, NC). ^a,bMeans with different superscripts within treatment are different by week (P = 0.01).

Figure 4.

Standing behavior area under the curve (AUC) for each day after arrival back to the farm from transportation event. Treatment × day: P = 0.57. ^a,bMeans with different superscripts are different (P ≤ 0.05).