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J Dairy Sci. 2017 Sep;100(9):7165-7182. doi: 10.3168/jds.2017-12746. Epub 2017 Jul 6.

Transient changes in milk production efficiency and bacterial community composition resulting from near-total exchange of ruminal contents between high- and low-efficiency Holstein cows.

Author information

1
US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706; Department of Bacteriology, University of Wisconsin, Madison. Electronic address: Paul.Weimer@ars.usda.gov.
2
Department of Bacteriology, University of Wisconsin, Madison.
3
Department of Animal Science, Federal University of Mato Grosso, Cuiabá, 78060-900, Brazil.
4
Department of Animal Sciences and Technology, Yangzhou University, Yangzhou, Jiangsu 225009, People's Republic of China.
5
US Dairy Forage Research Center, USDA-Agricultural Research Service, Madison, WI 53706.

Abstract

The objectives of this study were to determine if milk production efficiency (MPE) is altered by near-total exchange of ruminal contents between high- (HE) and low-MPE (LE) cows and to characterize ruminal bacterial community composition (BCC) before exchange and over time postexchange. Three pairs of ruminally cannulated, third-lactation cows were selected whose MPE (energy-corrected milk per unit of dry matter intake) differed over their first 2 lactations. Approximately 95% of ruminal contents were exchanged between cows within each pair. Ruminal pH and volatile fatty acid (VFA) profiles, along with BCC (characterized by sequencing of the variable 4 region of 16S rRNA genes), were assessed just before feeding on d -8, -7, -5, -4, -1, 1, 2, 3, 7, 10, 14, 21, 28, 35, 42, and 56, relative to the exchange date. High-MPE cows had higher total ruminal VFA concentrations, higher molar percentages of propionate and valerate, and lower molar percentages of acetate and butyrate than did LE cows, and re-established these differences 1 d after contents exchange. Across all LE cows, MPE increased during 7 d postexchange but declined thereafter. Two of the 3 HE cows displayed decreases in MPE following introduction of the ruminal contents from the corresponding LE cow, but MPE increased in the third HE cow, which was determined to be an outlier. For all 6 cows, both liquid- and solids-associated BCC differed between individuals within a pair before contents exchange. Upon exchange, BCC of both phases in all 3 pairs was more similar to that of the donor inoculum than to preexchange host BCC. For 5 of 6 cows, the solids-associated community returned within 10 d to more resemble the preexchange community of that host than that of the donor community. Individual variability before the exchange was greater in liquids than in solids, as was the variability in response of bacterial communities to the exchange. Individual cows varied in their response, but generally moved toward re-establishment of their preexchange communities by 10 d after contents exchange. By contrast, ruminal pH and VFA profiles returned to preexchange levels within 1 d. Despite the small number of cows studied, the data suggest an apparent role for the ruminal bacterial community as a determinant of MPE.

KEYWORDS:

milk production efficiency; ruminal contents exchange; ruminal microbiome

PMID:
28690067
DOI:
10.3168/jds.2017-12746
[Indexed for MEDLINE]

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