Abstract
Simple SummaryWeaning is very important for young ruminants. At this stage, calves’ main source of nutrients is transferred from milk into solid feed, such as starter and roughage. At the same time, the rumen function of calves undergoes tremendous changes, such as bacteria, which are the main players in rumen function. Our research found that the rumen bacteria network of post-weaning calves was more complex. The fermentation end products, such as acetate, propionate, and butyrate, were higher in the post-weaning calves than the pre-weaning group. However, digestive enzymes such as protease, carboxymethyl cellulase, cellobiohydrolase, and glucosidase were lower in the post-weaning calves than the pre-weaning calves. These findings provided useful information for reference regarding the feeding management of calves.To better understand the transition of rumen function during the weaning period in dairy calves, sixteen Holstein dairy calves were selected and divided into two groups: pre-weaning (age = 56 ± 7 day, n = 8) and post-weaning (age = 80 ± 6 day, n = 8). The rumen fluid was obtained by an oral gastric tube. The rumen fermentation profile, enzyme activity, bacteria composition, and their inter-relationship were investigated. The results indicated that the post-weaning calves had a higher rumen acetate, propionate, butyrate, and microbial crude protein (MCP) than the pre-weaning calves (p < 0.05). The rumen pH in the post-weaning calves was lower than the pre-weaning calves (p < 0.05). The protease, carboxymethyl cellulase, cellobiohydrolase, and glucosidase in the post-weaning calves had a lower trend than the pre-weaning calves (0.05 < p < 0.1). There was no difference in α and β diversity between the two groups. Linear discriminant analysis showed that the phylum of Fibrobacteres in the post-weaning group was higher than the pre-weaning group. At the genus level, Shuttleworthia, Rikenellaceae, Fibrobacter, and Syntrophococcus could be worked as the unique bacteria in the post-weaning group. The rumen bacteria network node degree in the post-weaning group was higher than the pre-weaning group (16.54 vs. 9.5). The Shuttleworthia genus was highly positively correlated with MCP, propionate, total volatile fatty acid, glucosidase, acetate, and butyrate (r > 0.65, and p < 0.01). Our study provided new information about the rumen enzyme activity and its relationship with bacteria, which help us to better understand the effects of weaning on the rumen function.
Highlights
Weaning, the most stressful and significant transition experienced by dairy calves, influences the ability of calves to adapt to the dramatic dietary shift and the production performance
The Shuttleworthia genus was highly positively correlated with microbial crude protein (MCP), propionate, TVFA, glucosidase, acetate, and butyrate (r > 0.65, and p < 0.01)
NH3 -N showed no difference between the two groups, but the MCP in the post-weaning group was higher than the pre-weaning group, which may be due to the microbiota in the post-weaning group having a higher ability to synthesize MCP
Summary
The most stressful and significant transition experienced by dairy calves, influences the ability of calves to adapt to the dramatic dietary shift and the production performance. The rumen becomes much more susceptible to changes in fermentability of diets after weaning [1]. Rumen buffering ability and metabolic adaptations increased after weaning, along with an increase in feed intake, especially the roughage [3,4,5]. Chong et al indicated that weaning could change the rumen fermentation profile and alter the rumen microbiota composition; the functional development of the rumen is influenced by weaning, which is associated with ruminal microbiota in lambs [6]. Oral inoculation of pre-weaned young calves with rumen microbiota from adult cows could affect the colonization of some rumen bacteria, methanogens, and protozoa, and some metabolic pathways, which showed that the regulation of rumen microbiota may be a promising way to shape the calves’ rumen function [7]. Rumen microbiota and fermentation progress are a comprehensive category, which needs further in-depth and detailed research
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