Abstract
In experiment 1, eighty crossbred steers (239±15 kg) were used in a 229-d experiment to evaluate the effects of increasing levels of enzymatically hydrolyzed yeast (EHY) cell wall in diets on growth performance feedlot cattle during periods of elevated ambient temperature. Treatments consisted of steam-flaked corn-based diets supplemented to provide 0, 1, 2, or 3 g EHY/hd/d. There were no effects on growth performance during the initial 139-d period. However, from d 139 to harvest, when 24-h temperature humidity index averaged 80, EHY increased dry matter intake (DMI) (linear effect, p<0.01) and average daily gain (ADG) (linear effect, p = 0.01). There were no treatment effects (p>0.10) on carcass characteristics. In experiment 2, four Holstein steers (292±5 kg) with cannulas in the rumen and proximal duodenum were used in a 4×4 Latin Square design experiment to evaluate treatments effects on characteristics of ruminal and total tract digestion in steers. There were no treatment effects (p>0.10) on ruminal pH, total volatile fatty acid, molar proportions of acetate, butyrate, or estimated methane production. Supplemental EHY decreased ruminal molar proportion of acetate (p = 0.08), increased molar proportion of propionate (p = 0.09), and decreased acetate:propionate molar ratio (p = 0.07) and estimated ruminal methane production (p = 0.09). It is concluded that supplemental EHY may enhance DMI and ADG of feedlot steers during periods of high ambient temperature. Supplemental EHY may also enhance ruminal fiber digestion and decrease ruminal acetate:propionate molar ratios in feedlot steers fed steam-flaked corn-based finishing diets.
Highlights
Temperature-Humidity index (THI; Mader et al, 2006) greater than 74 is considered stressful for cattle
This heat load causes a reduction in energy intake (Young and Hall, 1993; Hahn, 1994) and average daily gain (ADG) and gain efficiency (Blackshaw and Blackshaw, 1994; Hubbard et al, 1999)
All procedures involving animal care and management according to the equation: Dry matter intake (DMI) = EM/net energy of maintenance (NEm)+Energy gain (EG)/(0.877 were in accordance with and approved by the University of NEm –0.41), and can be resolved for estimation of dietary
Summary
Temperature-Humidity index (THI; Mader et al, 2006) greater than 74 is considered stressful for cattle. Shorthorn and Charolais breeds in various proportions) with reading of the Longissimus muscle (LM) at the 12th rib; an average weight of 239±15 kg were used in a 229-d subcutaneous fat (cm) over the LM at the 12th rib taken at a experiment to evaluate the effects of EHY cell wall location 3/4 the lateral length from the chine bone end (TruMax, Vi-COR, Mason City, IA, USA) supplementation (adjusted by eye for unusual fat distribution); kidney, pelvic on growth performance, dietary net energy, and carcass and heart fat (KPH), as a percentage of HCW; marbling characteristics of feedlot cattle. 1 Diets were supplemented to provide for an average estimated intake of 0, 1, 2, or 3 g/hd/d of EHY (TruMax, Vi-COR, Mason City, IA, USA) during respective feeding periods.
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