Adding polyethylene glycol to steer ration containing sorghum tannins increases crude protein digestibility and shifts nitrogen excretion from feces to urine

Biao Xie; Xiao Yang; Ling Yang; Xianjiang Wen; Guangyong Zhao

doi:10.1016/j.aninu.2021.03.002

Adding polyethylene glycol to steer ration containing sorghum tannins increases crude protein digestibility and shifts nitrogen excretion from feces to urine

Anim Nutr. 2021 Sep;7(3):779-786. doi: 10.1016/j.aninu.2021.03.002. Epub 2021 May 13.

Authors

Biao Xie¹, Xiao Yang¹, Ling Yang², Xianjiang Wen², Guangyong Zhao¹

Affiliations

¹ State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, 100193, Beijing, China.
² Sorghum Research Institute, Shanxi Academy of Agricultural Sciences, 030600, Jinzhong, China.

Abstract

The objectives of the experiment were to study the effects of adding polyethylene glycol (PEG) to steer ration containing high sorghum tannins on rumen fermentation, nutrient digestion, nitrogen (N) balance and plasma biochemical parameters. Eight growing steers at 16 months of age were allotted to a replicated 4 × 4 Latin square design with 4 treatments and 4 periods (19 d each). Polyethylene glycol at 0, 1.75, 3.50 and 7.00 g/kg dry matter (DM) were added to a basal ration containing 27.82% DM of sorghum grain (total tannins 3.3 g/kg DM) as the treatments. The results indicated that adding PEG quadratically increased the ruminal pH (P = 0.049), tended to linearly increase the ruminal concentration of total volatile fatty acids (P = 0.070), increased the molar proportion of acetate (P = 0.016), linearly decreased the molar proportion of butyrate (P = 0.015), and tended to increase the molar proportion of iso-valerate (P = 0.061) and the ruminal concentration of ammonia N (P = 0.092). Adding PEG tended to quadratically decrease the relative abundance of methanogenic archaea (P = 0.082), linearly decreased the relative abundance of Fibrobacter succinogenes (P = 0.008) and decreased the relative abundance of Butyrivibrio fibrisolvens (P = 0.048) at 7.00 g/kg DM. Dietary addition with PEG increased the crude protein (CP) digestibility (P < 0.001) and tended to increase the neutral detergent fiber digestibility (P = 0.066) in a linear manner. Adding PEG to basal ration also increased the plasma globulin concentration (P = 0.029) and tended to linearly increase the plasma total protein concentration (P = 0.069). Adding PEG linearly decreased the fecal N excretion (P < 0.001) and the fecal N-to-total N excretion ratio (P = 0.004) and increased the urinary N-to-total N excretion ratio (P = 0.004) and urinary urea excretion (P = 0.010) without affecting the urinary N and total N excretions (P > 0.05). It was concluded that adding PEG effectively improved the CP digestibility of the ration containing high sorghum tannins but increased the urinary urea excretion without improving the N retention and N retention rate in steers.

Keywords: Cattle; Nitrogen retention; Nutrient digestibility; Polyethylene glycol; Rumen fermentation; Sorghum tannin.