Reducing dietary cation–anion difference seldom affects rumen fermentation, cellulolytic bacteria populations, and microbiota in goats

Abstract

Background: Dietary cation–anion difference (DCAD) has been receiving increased attention in recent years; however, information on the rumen fermentation, cellulolytic bacteria populations, and microbiota of goats fed a low-DCAD diet is less. This study aimed to evaluate the feasibility of feeding a low-DCAD diet for goats with emphasis on rumen fermentation parameters, cellulolytic bacteria populations and microbiota. Growth performance, urine pH, and plasma metabolites were also analyzed as well. Materials and method: Eighteen goats were randomly allocated to 3 treatments with six replicates of each treatment and 1 goat per replicate. Animals were fed diets with varying DCAD levels at +338 (High DCAD; HD), +152 (Control; CON), and −181 (Low DCAD; LD). This study includes 15-d experimental period and 30-d adaption period. Results: The DCAD level did not affect the rumen fermentation parameters including pH, buffering capability, acetic acid, propionic acid, butyric acid, total volatile fatty acids, and ratio of acetic acid/propionic acid (P > 0.05). The 4 main ruminal cellulolytic bacteria populations including Fibrobacter succinogenes, Ruminococcus flavefaciens, Butyrivibrio fibrisolvens and Ruminococcus albus did not differ from DCAD treatments (P > 0.05). The DCAD levels did not affect bacterial richness and diversity indicated by the indices Chao, Ace and Simpson and Shannon, respectively (P > 0.05). Both weighted UniFrac and unweighted UniFrac showed no difference in the composition of rumen microbiota for CON, HD and LD (P > 0.05). At the phylum level, Bacteroidetes was the predominant phylum followed by Firmicutes, Synergistetes, Proteobacteria, Spirochaetae, and Tenericutes, and they showed no difference (P > 0.05) in relative abundances except for Firmicutes, which was higher in HD and LD compared to CON (P < 0.05). At the genus level, relative abundance of 11 genera were not affected by DCAD treatments (P > 0.05). Level of DCAD had no effect (P > 0.05) on growth performance including dry matter intake, average net gain, average daily gain, and feed conversion ratio; and nutrients digestibility of crude protein, neutral detergent fiber, acid detergent fiber, and organic matter (P > 0.05). Urine pH in LD was lower than HD and CON (P < 0.05). LD resulted in higher plasma calcium than HD and CON (P < 0.05) but not for other plasma metabolites (P > 0.05). Conclusion: We conclude that, with regard to the great importance of rumen fermentation, these results suggest that reducing DCAD is unharmful for rumen status and provide the feasibility of feeding a low-DCAD to goats.