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Effects of dietary organic acid and plant botanical supplementation on growth performance in Holstein calves challenged by heat stress.

A. B. P. Fontoura

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06-22-2020

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Abstract:

M100
Effects of dietary organic acid and plant botanical supplementation on growth performance in Holstein calves challenged by heat stress.
A. B. P. Fontoura*1, V. S�inz de la Maza-Escol�1,2, B. N. Tate1, J. T. Siegel Nieves1, A. T. Richards1, F. Wang1,3, L. F. Wang1,4, M. E. Van Amburgh1, E. Grilli2,5, J. W. McFadden1. 1Cornell University Ithaca, NY, 2University of Bologna Bologna, Italy, 3China Agricultural University Beijing, China, 4Henan Agricultural University Zhengzhou, China, 5VetAgro S.p.A Reggio Emilia, Italy.

Our objectives were to evaluate the effects of heat stress (HS) and dietary organic acid and plant botanical (OA/PB) supplementation on growth in calves. In a completely randomized design, 62 bull and heifer calves were assigned to 1 of 5 groups (n = 12—13/group): thermoneutral conditions (TN-Con), HS conditions (HS-Con), thermoneutral conditions pair-fed to HS-Con (TN-PF), HS with low-dose OA/PB (75 mg/kg of BW; 25% citric acid, 16.7% sorbic acid, 1.7% thymol, 1.0% vanillin, and 55.6% triglyceride; AviPlus R; Vetagro, Italy; HS-Low), or HS with high-dose OA/PB (150 mg/kg of BW; AviPlus R; HS-High). Supplements were delivered as a twice daily bolus via the esophagus wk 1 through 13 of life; all calves received boluses equivalent for triglyceride. Post weaning, calves (62 � 2 d; 91 � 10.9 kg) remained in thermoneutral conditions (temperature-humidity index [THI]: 60 to 69) for a 7-d covariate period. Thereafter, calves remained in TN conditions or were moved to HS conditions (THI: 75 to 83) for 19 d. Clinical assessments and BW were recorded, and blood was sampled. Organs from HS-Con and TN-Con were harvested at trial completion. The mixed model included fixed effects of BW at birth, treatment, time, and their interaction. Rectal and skin temperatures, and respiration rates were greater in HS-Con, relative to TN-Con (P < 0.01). Dry matter intake (DMI) and average daily gain (ADG) were lower in HS-Con, relative to TN-Con (P < 0.01). Comparing HS-Con and PF-Con, ADG and gain:feed were similar. Plasma fatty acids were elevated in TN-PF versus all other groups (P = 0.04; not observed for HS-Con). Liver and small intestine weights were lower in HS-Con, relative to TN-Con (P = 0.03 and 0.15, respectively). DMI was greater with HS-Low, relative to HS-Con (P < 0.01). ADG for HS-Low and HS-High were not different from HS-Con or TN-Con (i.e., effect was intermediate). Compared with HS-Con, calves fed OA/PB tended have greater gain:feed (P = 0.08). We conclude that reductions in DMI account for losses in growth during HS and dietary OA/PB supplementation enhances HS resilience in calves.

Keywords: calf, heat stress, organic acid.