The effect of long-term acidifying feeding on digesta organic acids, mineral balance, and bone mineralization in growing pigs

Feeding a Negative Dietary Cation-Anion Difference to Female Goats Is Feasible, as Indicated by the Non-Deleterious Effect on Rumen Fermentation and Rumen Microbial Population and Increased Plasma Calcium Level

Simple Summary

Diets with a lower dietary cation-anion difference could prevent hypocalcemia, enhance health, and extend the economic life of transition mammary animals. However, there is less information on rumen fermentation, cellulolytic bacteria populations, and microbiota for female goats fed a negative dietary cation-anion difference diet. We speculate that a negative dietary cation-anion difference would not affect the rumen fermentation parameters. Therefore, the present study was conducted to evaluate the effect of a negative dietary cation-anion difference diet on rumen pH, buffering capability, volatile fatty acids of acetic acid, propionic acid, butyric acid, total volatile fatty acid and acetic acid/propionic acid profiles, ruminal cellulolytic bacteria populations, and microbiota. These results provide a further evaluation on the feasibility of feeding a negative dietary cation-anion difference diet to goats.

Abstract

The dietary cation-anion difference (DCAD) has been receiving increased attention in recent years; however, information on rumen fermentation, cellulolytic bacteria populations, and microbiota of female goats fed a negative DCAD diet is less. This study aimed to evaluate the feasibility of feeding a negative DCAD diet for goats with emphasis on rumen fermentation parameters, cellulolytic bacteria populations, and microbiota. Eighteen female goats were randomly blocked to 3 treatments of 6 replicates with 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 lasted 45 days with a 30-d adaption and 15-d trial period. The results showed that the different DCAD levels did not affect the rumen fermentation parameters including pH, buffering capability, acetic acid, propionic acid, butyric acid, sum of acetic acid, propionic acid, and butyric acid, or the ratio of acetic acid/propionic acid (p > 0.05). The 4 main ruminal cellulolytic bacteria populations containing Fibrobacter succinogenes, Ruminococcus flavefaciens, Butyrivibrio fibrisolvens, and Ruminococcus albus did not differ from DCAD treatments (p > 0.05). There was no difference in bacterial richness and diversity indicated by the indices Chao, Abundance Coverage-based Estimator (Ace), or Simpson and Shannon, respectively (p > 0.05), among 3 DCAD levels. Both principal coordinate analysis (PCoA) weighted UniFrac distance and unweighted UniFrac distance 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, the relative abundances of 11 genera were not affected by DCAD treatments (p > 0.05). The level of DCAD had no effect (p > 0.05) on growth performance (p > 0.05). Urine pH in LD was lower than HD and CON (p < 0.05). Goats fed LD had higher plasma calcium over HD and CON (p < 0.05). In summary, we conclude that feeding a negative DCAD has no deleterious effects on rumen fermentation and rumen microbiota and can increase the blood calcium level, and is therefore feasible for female goats.

Effects of Acidifying Pig Diets on Emissions of Ammonia, Methane, and Sulfur from Slurry during Storage

Ammonia (NH) volatilization from intensive livestock production is a threat to natural ecosystems. This study investigated pig diet manipulation by 1% (w/w) benzoic acid (BA) amendment and lowering of dietary electrolyte balance through substituting 1.4% (w/w) CaCO with 2.0% (w/w) CaCl. Urine and feces were collected separately from 24 pigs fed one of four diets (Control, +BA, +CaCl, +BA+CaCl) in metabolic cages and mixed as slurry. During 103 d of storage, all acidifying diets consistently reduced pH in the slurry by 0.4 to 0.6 units. There was a strong relationship between slurry pH and NH emissions, which were considerably reduced by the three acidifying diets. The +BA diet decreased NH emission by 28%, the +CaCl diet by 37%, and the combined +BA and +CaCl diet by 40%. Acidifying diets had no effect on S cycling or emission of volatile S compounds under the prevailing conditions of restricted S feeding. Methane (CH) emissions were increased by 73% in diets with CaCl. An initial delay in CH emissions was investigated in a separate experiment with manipulation of pH (5.4, 6.7, or 8.8) and inoculation with adapted pig slurry (0, 4, 11, or 19%), which showed that methanogenic potential, rather than inhibitory effects of the chemical environment, caused the delay. In conclusion, NH emissions from slurry could be reduced by addition of BA to pig diets or by controlling the dietary electrolyte balance, but there was no additive effect of combining the two strategies. However, CH emissions from slurry may increase with acidifying diets.