Evaluation of immunoglobulin-Y in place of tylosin phosphate in the diets fed to Holstein Steers

and preliminary analysis of liver abscess duration on animal growth performance

ABSTRACT: Despite the regular use of feedgrade macrolide-antibiotics, bovine liver abscesses persist, representing a financial burden to pre- and post-mortem sectors of the beef industry. An immunoglobulin-Y (IGY) additive developed to target Fusobacterium necrophorum and Trueperella pyogenes, was evaluated for the control of liver abscesses. Research is needed for the impact of liver abscess severity as well as abscess duration on steer performance and carcass characteristics. Holstein steers (n = 64; initial body weight (BW) = 372.5 Å} 2.41 kg) consuming a finishing diet for 188 d were used in a completely randomized design where treatments included: TYL (tylosin phosphate 90 mg/d; n = 32) or IGY (2.5 g/d; n = 32) and steer was the experimental unit. Feed intake was recorded daily while BW and liver ultrasound outcome (normal or abnormal) was recorded every 28 d until slaughter to estimate duration of abscess presence (DUR).

Continuous variables of animal growth performance and carcass characteristics were analyzed using the MIXED procedure of SAS. Categorical quality grade and liver data were analyzed using the GLIMMIX procedure of SAS. Treatment did not affect live or carcass-adjusted growth performance (P ≥ 0.131). However, steers fed TYL had greater (P = 0.042) empty body fat (EBF) % and a greater proportion of carcasses grading premium choice than steers fed IGY (P = 0.030). Treatment did not affect prevalence of abscessed livers, abscess severity or estimated abscess duration (P ≥ 0.213) but datasets with greater experimental units are needed to substantiate this outcome. Increasing abscess severity tended (P ≤ 0.10) to linearly reduce carcass-adjusted gain to feed (G:F), fat thickness, and EBF. Carcass dressing % was only affected by severe (A+ and A+AD) abscess scores (P = 0.010). Carcass-adjusted final BW, average daily gain, G:F, and hot carcass weight was decreased only when the estimated DUR was ≥140 d (P ≤ 0.05). Carcass dressing %, however, was linearly affected by estimated liver abscess DUR (P ≤0.005), regardless of abscess severity. Preliminary evidence suggests that measuring the duration of liver abscess affliction during the feeding period may also give insight to the degree of performance reduction.

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RESULTS AND DISCUSSION

Treatment Effects

The effects of treatment on finishing cattle growth performance and carcass characteristics are presented in Tables 2 and 3, respectively. No differences (P ≥ 0.155) were observed for mid-test BW, final BW, DMI, ADG, G:F or carcass adjusted performance between steers fed IGY or TYL. Hot carcass weight, dressing percentage, LMA, and MARB were similar between treatments (P ≥ 0.139), but steers consuming TYL had greater FT than steers consuming IGY (0.813 vs. 0.613 cm, respectively; P = 0.033). This resulted in TYL-fed steers having a greater calculated YG than IGY-fed steers (2.86 vs. 2.45, respectively; P = 0.020). The estimated EBF was also greater for TYL fed steers compared to IGY fed steers (27.5% vs. 26.3%, respectively: P = 0.042), but there was no treatment effect on AFBW (P = 0.169). Steers fed TYL resulted in a greater percentage of carcasses grading premium choice than steers fed IGY (30.8% vs. 7.41%, respectively; P = 0.030), whereas steers fed IGY resulted in a greater percentage of carcasses grading low choice than steers fed TYL (59.3% vs. 30.8%, respectively; P = 0.038). While gain performance was not different between treatment groups, composition of gain may have been affected, favoring greater fat deposition in TYL fed steers, but at this time, it is not clear why this occurred. As this experiment was the first to examine this particular antibody combination, no literature exists to compare these findings between IGY and TYL. It was not anticipated that the egg yolk product would decrease the rate of fat deposition when compared to TYL, unless there was a difference in liver abscess rate, as liver abscesses have been shown to reduce 12th rib backfat thickness in beef carcasses (Brown and Lawrence, 2010). DiLorenzo et al. (2008) fed a similar IGY product containing both Streptococcus bovis and F. necrophorum antibody and did not detect a difference in gain performance or carcass characteristics when compared to control steers who were fed neither IGY nor TYL. In the current experiment, although DMI was not statistically different, the TYL fed steers consumed an average of 0.24 kg more per day than IGY fed steers, which may account for the difference in fat composition at harvest.

Treatment did not affect the prevalence of abscessed livers, distribution of abscess severity, or the estimated DUR (P ≥ 0.213; Table 3). The current experiment is limited in interpretation of this outcome due to the lack of a negative control. However, DiLorenzo et al. (2008) reported liver abscess score on a continuous scale and found that steers fed a F. necrophorum antibody preparation had a 41.6% reduction in liver abscess severity score than control steers who were fed neither IGY nor TYL. The author attributed this reduction in liver abscess severity to lesser ruminal counts of F. necrophorum, which was made apparent in a previous experiment (DiLorenzo et al., 2006). The pool of literature for specifically formulated immunoglobulin-Y products developed for the control of liver abscesses in cattle is small (DiLorenzo et al., 2006, 2008). Research focused on other antigens, however, has been conducted in beef calves to control bovine rotavirus and bovine coronavirus using a similar oral route of administration, resulting in significantly reduced viral shedding compared with calves not consuming the egg yolk product (Kuroki et al., 1994, 1997; Ikemori et al., 1997). More recent in vitro work by Zhen et al. (2008) and Xu et al. (2012) substantiated the concept of immunoglobulin-Y adherence to antigens as being dose-dependent when applied to Fusobacterium spp. or Staphylococcus spp. Outcomes of antigen selection, antibody combinations, and dosage, however, are yet to be established in the literature for the purposes of liver abscess control in cattle. Research determining optimal antibody combination and comparing customized IGY products with both negative controls (no feed additive) and positive controls (TYL) is needed before IGY can be considered as a suitable alternative to TYL in the cattle feeding industry. The outcomes of the current research add to the literature and may be used as an aid in determining an effect size for future experimental planning.