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Title: Dose effects of encapsulated butyric acid and zinc on beef feedlot steer growth performance, dietary net energy utilization, rumen morphometrics, small intestine histology, and carcass characteristics.
Author: Francis FL, Rusche WC, LaFleur D, Hergenreder JE, Smith ZK.
Journal: J Anim Sci; 2024 Jan 03; 102():. PubMed ID: 39155509.
Abstract:
The objective of this study was to determine the effects that increasing doses of encapsulated butyric acid and zinc (BZ) have on feedlot steer growth performance, rumen morphometrics and small intestine histology (data not statistically analyzed), dietary net energy utilization, and carcass characteristics. Steers [n = 272; shrunk body weight (BW) = 360 kg ± 74 kg] were assigned to dietary treatments [0 (CON), 1, 2, or 3 g BZ/kg diet dry matter] in a randomized complete block design (RCBD) with pen (n = 32 total; n = 8 per treatment) as experimental unit. Pens were blocked by cattle source and location within the feedyard. Cattle were fed until visually assessed to have 1.27 cm rib-fat and were shipped for harvest at a commercial beef abattoir. Carcass and liver health data were recorded. A subset of steers (n = 8 total; n = 2 per treatment) was harvested at the SDSU Meat Laboratory to collect empty body measurements, rumen samples for morphometric analysis, and duodenal and ileal samples for histological analysis to provide context to feeding trial outcomes. Feedlot growth performance data was calculated on a carcass-adjusted basis: hot carcass weight (HCW)/0.625. Data were analyzed as a RCBD with fixed effects of BZ inclusion level and block was considered a random effect; pre-planned contrasts for CON vs. BZ, plus linear, and quadratic responses were tested. No differences (P ≥ 0.11) were observed for final BW, dry matter intake, average daily gain (ADG), feed conversion efficiency (G:F), performance calculated dietary net energy, HCW, ribeye area, rib-fat thickness, marbling score, estimated empty body fat, or distribution of USDA yield grade (YG) 1, 3, 4, 5, and USDA quality grade among treatments. A tendency (P = 0.10) was observed for CON vs. BZ for calculated YG. Tendencies were detected for USDA YG 2 carcass distribution (linear; P = 0.07) and for normal and abscessed liver prevalence (quadratic; P = 0.08). Dressed yield tended to be greater (P = 0.08) for BZ vs. CON and increased with dose (linear; P = 0.05). Receiving period shrunk BW, ADG, and G:F was improved (P ≤ 0.02) for BZ-supplemented steers compared to CON. Data from this study suggests that the addition of BZ to feedlot finishing diets to improve receiving period growth performance and decreasing the prevalence of abscessed livers should be further investigated. Encapsulating butyric acid and zinc (BZ) can allow a timed release through the gastrointestinal tract (GIT) which can potentially improve rumen and intestinal epithelial health, as well as improve growth performance and carcass characteristics of cattle. We conducted a study to determine how increasing dietary inclusion of BZ affects feedlot steer growth performance, GIT health, and carcass traits. Four inclusion levels were tested in this experiment: 0, 1, 2, and 3 g BZ/kg diet (dry matter basis). Inclusion of BZ improved growth performance during the initial 28 d receiving period but did not alter growth performance for the cumulative feeding period. Only minor differences were observed for GIT health markers and carcass traits for steers supplemented BZ compared to non-supplemented steers. However, the prevalence of liver abscesses was quadratically affected by an increasing dose of BZ where 0 and 3 g BZ/kg had the highest prevalence and 1 and 2 g BZ/kg had the lowest prevalence. These data indicate that the use of BZ may be beneficial during the dietary adaptation period, and growth performance benefits may persist through the finishing period.

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