Modulation of rumen fermentation and microbial community through increasing dietary cation-anion difference in Chinese Holstein dairy cows under heat stress conditions

AIMS

The effect of increasing dietary cation-anion difference (DCAD) on rumen fermentation and ruminal microbial community in dairy cows under heat stress (HS) conditions were evaluated.

METHODS AND RESULTS

This study was performed as a two-period cross-over design during the summer season, with eight lactating dairy cows randomly distributed to either a control DCAD diet (CON: 33·5 mEq/100 g DM) or high DCAD diet (HDCAD: 50·8 mEq/100 g DM). Throughout the present study, the temperature and humidity index (THI; 80·2 ± 4·29) was generally elevated above the threshold (THI = 72) that is reported to cause HS in lactating dairy cows. Rumen liquid samples were collected on 15 and 21 d during each 21 d-period. The absolute concentration of ruminal total volatile fatty acid (TVFA) in HDCAD treatment was significantly (P < 0·05) higher than those in the control, whilst the ruminal pH, NH₃ -N, and VFA molar percentages were unaffected through increasing DCAD. Furthermore, the copy numbers of the cellulolytic bacteria Ruminococcus albus and Ruminococcus flavefaciens in rumen fluid significantly (P < 0·05) rose along with the increment of DCAD. Although the Alpha diversity indexes and the bacterial microbiota structure were unaffected, increasing DCAD significantly (P < 0·05) enriched the phylum Fibrobacteres and genus Fibrobacter in the microflora of rumen fluid, whilst the genera Flexilinea and Dubosiella were the most differentially abundant taxa in the control.

CONCLUSIONS

Increasing DCAD under HS conditions resulted in a greater concentration of total VFA without affecting rumen bacteria diversity or structure, although the enrichment of some cellulolytic/hemicellulolytic bacteria was observed.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study provides information on the modulation of rumen fermentation and microbial community through the increment of DCAD in Holstein dairy cows under HS conditions.

The risk to the cutaneous nerve branches in the anterior (Wagner) and snuff-box approaches to the trapezium: a cadaveric study

We compared the risk with the subcutaneous nerves with the anterior (Wagner) and snuff-box approaches to the trapezium in cadavers. Branches that crossed tattooed incision markings or lay within 1 cm of the markings were identified on six matched pairs of fresh-frozen cadaveric hands. Their distance from the proximal end of the incision was recorded. For anterior incisions, there were 20 vulnerable branches in total, at a mean distance of 22 mm from the proximal end of the incision. A total of 13 lay in the distal half of the incision. For snuff-box incisions, there were 18 vulnerable branches in total, at a mean distance of 11 mm from the proximal end of the incision, with 17 of them lying in the proximal half of the incision. Neither incision is without risk to nerve braches, but our study suggests a lesser risk of subcutaneous nerve damage with the snuff-box approach and highlights the greater risk in the proximal half of this incision.