Introduction

Because calves entering the feedlot are often vitamin E deficient (^{Mass et al., 2008}), administration of vitamin E during receiving is recommended (^{Secrist et al., 1997}). Previous work (^{Hidiroglou and Batra, 1996}; ^{McDowell et al., 1996}) demonstrates that plasma tocopherol concentrations are affected by dosage level, frequency of administration, and chemical form of vitamin E and its carrier. Traditionally, vitamin E is administered via intramuscular (IM) injection. It has been maintained that, compared to IM administration, the subcutaneous (SQ) administration of vitamin E result in lower rate of uptake to appreciably increase plasma and tissue alpha-tocopherol concentrations (^{Judson et al., 1991}). However, direct comparisons between IM and SQ routes of administration have not been conducted. Thus, there is no conclusive experimental basis for this recommendation. With increased interest in reduction of injection-site blemishes resulting by IM injections in feedlot industry (^{Roeber et al., 2001}), it is preferable that, where feasible, injection treatments be applied SQ.

The objective of this trial was to compare IM vs SQ routes of vitamin E administration on plasma alpha-tocopherol concentrations and incidence of injection site inflammation in the first 56 days of the arrival of newly received calves.

Materials and Methodology

All animals care, handling, and surgical techniques followed protocols that have been approved by the University of California, Davis, Animal Use and Care Committee.

Fifty Holstein steer calves (121 ± 4 kg) were used to evaluate the influence of SQ versus IM injection of vitamin E on plasma alpha-tocopherol concentrations and incidence of injection site inflammation during the initial 16 days following their arrival into the feedlot. Calves were purchased as steers (previously castrated via elastration). Upon arrival, steers were vaccinated for bovine rhinotracheitis parainfluenza3 (TSV-2, Zoetis, Florham Park, NJ), Clostridials (Fortress 8, Zoetis, Florham Park, NJ), and Pasteurella haemolytica (One Shot, Zoetis, Florham Park, NJ), were treated for parasites (Dectomax Injectable, Zoetis, Florham Park, NJ), and randomly assigned to three treatment groups. Steers were group-fed a steam-flaked corn-based receiving diet with an expected concentration of 22 mg/kg vitamin E (^{NRC, 1996}). The formulation of receiving diet is shown in Table 1.

Table 1 Ingredients and composition of receiving diet. 

Trace mineral salt contained: CoSO₄, .068%; CuSO₄, 1.04%; FeSO₄, 3.57%; ZnO, 1.24%; MnSO₄, 1.07%, KI 0.052%; and NaCl, 92.96%, Chemical composition and calculated net energy are based on tabular concentration of nutrients and net energy (NE) values for individual feed ingredients (^{NRC, 1996}).

Ten steers served as controls, receiving no vitamin E injections. The remaining 40 steers (20 steers/treatment) were injected either IM or SQ with 1500 IU of d-alpha tocopherol (5 mL of Vital E-A+D₃, Stuart Products Inc., Bedford, TX). Site of injection was located in front of the shoulder and midway of the neck in the “injection triangle” below the nuchal ligament and above the jugular furrow. Vitamin E treatments were administered on days 1 and 8. Blood samples were obtained from all steers (controls and treated with vitamin E) on days 1 (before administration of vitamin E treatments), 4, 8, 12 and 16. Blood samples were collected via jugular puncture into heparinized tubes. Immediately, blood was centrifuges at 1070×g for 10 min. Plasma alphatocopherol analyses was conducted by the Veterinary Diagnostic Laboratory (College of Veterinary Medicine, Iowa State University, Ames, IA) according to procedures described by ^{Stahr (1991)}. On the final day of the study (day 16), incidence of injection site inflammation was recorded based on presence of absence of visible swelling. The trial was analyzed as a completely randomized design. Data were analyzed by repeated-measures analysis of variance using the MIXED procedure of SAS version 9.1 (Cary, NC. USA). The means were compared by the Tukey test at 5% of probability.Treatment effects on proportion of steers with injection-site inflammation was analyzed using the Mantel-Haenszel chi-square analysis. Differences were considered significant when the P-value was ≤ 0.05.

Results and discussion

Treatment effects on plasma tocopherol concentrations is shown in Table 2. Plasma alphatocopherol concentrations of control steers remained low throughout the 16-day period of the study, averaging 0,06, 0,06, 0,06, 0,11, and 0,10 mg/dL for days 1, 4, 8, 12, and 16, respectively.

Table 2 Influence of subcutaneous versus intramuscular administration of vitamin E on plasma alpha-tocopherol concentrations (mg/dL) in newly arrival feedlot calves. 

Vitamin E treatments were administered on day 1 and day 8 immediately following blood collection; SQ = subcutaneous injection; IM = Intramuscular injection.

As expected (^{Batra et al., 1995}), tocopherol injection increased (P < 0.01) plasma alphatocopherol concentrations. However, plasma alpha-tocopherol concentrations were not different (P > 0.10) for IM and SQ routes of administration, averaging 0.41 ± 0.29, 0.28 ± 0.12, 0.56 ± 0.31 and 0.37 ± 0.13 mg/dL for days 4, 8, 12, and 16, respectively. The similarities in plasma alpha-tocopherol between IM and SQ suggest that the rates of uptake or mobilization are similar. This contrasts with ^{Judson et al. (1991)} who did not observed a significant increased plasma tocopherol following SQ administration during the first four days following administration of 120 mg/kg of dl-alpha tocopheryl acetate to sheep.

Route of vitamin E administration did not influence (P > 0.10) the incidence of injection site inflammation, averaging 17.5% (χ², P>0.05). Furthermore, plasma alpha-tocopherol concentrations were not affected (P > 0.30) by the presence or absence of injection site inflammation, averaging 0.40 ± 0.11 and 0.36 ± 0.14 mg/dL, respectively.

Since the risk of lesions in meat are considerably higher with intramuscular application (^{Li et al., 2012}) and plasma alpha-tocopherol concentrations were not different between routes of application, it is concluded that subcutaneous administration is a practical alternative to the traditional intramuscular of administration of injectable vitamin E for feedlot cattle.