Article pubs.acs.org/JAFC
Breed and Lactation Stage Alter the Rumen Protozoal Fatty Acid Profiles and Community Structures in Primiparous Dairy Cattle Laura M. Cersosimo, Melissa L. Bainbridge, André-Denis G. Wright,† and Jana Kraft* Department of Animal and Veterinary Sciences, University of Vermont, 570 Main Street, Burlington, Vermont 05405, United States ABSTRACT: The protozoal fatty acid (FA) composition and community structure are important to dairy cattle nutrition and their products. The purpose of the study was to observe if the rumen protozoal FA profiles and protozoal community structure differed by breed and lactation stage. At 93, 183, and 273 days in milk (DIM), whole rumen digesta samples were collected from seven co-housed Holstein (H), eight Jersey (J), and seven Holstein−Jersey crossbreed (C) cows. Rumen protozoal linoleic acid was higher at 183 DIM (8.1%) and 273 DIM (8.3%) than at 93 DIM (5.7%). Oleic acid was the most abundant protozoal unsaturated FA (10.1%). Protozoal rumenic acid and protozoa of the genus Metadinium were higher in J (9.9%) than in H (0.52%) and C (0.96%). Protozoa belonging to the genus Entodinium were more abundant in H (45.2%) than in J (23.4%) and C (30.2%). In conclusion, breed and DIM affected several protozoal FAs and genera. KEYWORDS: bioactive fatty acids, conjugated linoleic acids, ciliates, Holstein, Jersey, Holstein−Jersey crossbreeds
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INTRODUCTION The rumen is an anaerobic environment, containing microorganisms (bacteria, fungi, and protozoa) that ferment feedstuff into volatile fatty acids (VFAs), the main energy source for animal production. Bacteria make up the majority of the rumen microbiome (1010−1011 cells/mL of rumen digesta).1 The protozoal density (104−106 cells/mL of rumen digesta)1 is much lower, yet they account for 40−50% of the microbial biomass.2 Rumen protozoa are anaerobic ciliates representing a diverse group of over 30 characterized genera.3 The two major groups include the orders Entodiniomorphida and Vestibuliferida. Entodiniomorphids (e.g., Entodinium, Eudiplodinium, Polyplastron, and Metadinium spp.) have cilia around their cytostomes, feed on plant surfaces, and engulf starch granules. In contrast, Vestibuliferids (e.g., Dasytricha and Isotricha spp.), have cilia covering their entire body.4−6 In comparison to rumen bacteria, much less is known about rumen protozoa. Similar to rumen bacteria, protozoa breakdown starch, fiber, and proteins.2,6 Polyunsaturated fatty acids (PUFAs) are toxic to rumen bacteria as a result of their double bonds, and thus, rumen bacteria biohydrogenate feed-derived PUFAs to saturated fatty acids (SFAs).7 Rumen protozoa engulf chloroplasts8 that are high in the PUFAs linoleic acid (LA; 18:2 9c,12c) and αlinolenic acid (ALA; 18:3 9c,12c,15c). Although several studies demonstrated that protozoa do not biohydrogenate unsaturated fatty acids (UFAs),8−10 Or-Rashid et al.11 suggested that protozoa might convert stearic acid (SA; 18:0) to vaccenic acid (VA; 18:1 11t) through Δ11-desaturase activity. It has been suggested that biohydrogenation of intraprotozoal chloroplasts may occur as protozoa engulf bacteria into their vacuoles.12 The lipid membranes of protozoa contain more UFAs, including biohydrogenation intermediates, such as VA and conjugated linoleic acids (CLAs), than bacteria.11 Because rumen protozoa provide UFAs for duodenal absorption that are subsequently incorporated into meat and milk,11 they have the potential to contribute to a more appealing product to the consumer. © XXXX American Chemical Society
In the United States, Holstein and Jersey cows are the most popular breeds of dairy cattle. Holsteins are known for their high milk production, whereas Jerseys are known for their milk solids.13 Holstein−Jersey crossbreeds are of interest because they combine favorable qualities from both breeds. Previous research using clone libraries suggested differences in the rumen methanogen communities between lactating Holstein and Jersey dairy cows,14 whereas the abundance of the rumen bacterium Ruminococcus albus was higher in Jersey cows.15 Although Beecher et al.15 observed no differences in the density of rumen protozoa in Holstein, Jersey, and Holstein−Jersey crossbreed cows, protozoal taxa were not identified. Few studies have identified rumen protozoal genera,16−19 while no studies have identified the rumen protozoal fatty acid (FA) profile at different days in milk (DIM) and/or in three breeds of dairy cattle. To date, the majority of rumen protozoal research has focused on culture-dependent strategies rather than culture-independent metagenomic strategies, such as nextgeneration sequencing (NGS) of the eukaryote-specific 18S rRNA gene. Furthermore, Lima et al.19 used a NGS platform to demonstrate differences in protozoal taxonomic classes before and after calving when cows transition from a high-neutral detergent fiber (NDF) to a high-starch diet but did not identify 18S rRNA gene sequences to species or genus levels at different DIM. Little is known about how DIM and breed affect rumen protozoa. Because the rumen protozoal community contributes to the fermentation of carbohydrates and the protozoal FA composition contributes to the milk FA composition, it is important to gain knowledge about each component. We hypothesized that breed and DIM would alter the rumen protozoal FA composition, community structure, and density in co-housed, primiparous Holstein, Jersey, and Holstein−Jersey Received: November 5, 2015 Revised: December 29, 2015 Accepted: January 11, 2016
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DOI: 10.1021/acs.jafc.5b05310 J. Agric. Food Chem. XXXX, XXX, XXX−XXX
Article
Journal of Agricultural and Food Chemistry crossbreeds consuming a total mixed ration (TMR) at 93 DIM (early-lactation), 183 DIM (mid-lactation), and 273 DIM (latelactation). Our objectives were to (1) identify and quantify the protozoal FA compositions, (2) classify the rumen protozoal 18S rRNA gene sequences to genera, (3) measure the protozoal cell densities, and (4) determine if correlations exist between rumen protozoal genera and protozoal FA compositions at 93, 183, and 273 DIM.
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Table 2. FA Composition of the TMR Fed to Holstein, Jersey, and Holstein−Jersey Crossbreed Cows at 93, 183, and 273 DIM DIM FA (% of total)
12:0 14:0 15:0 16:0; PA 16:1 9c 17:0 18:0; SA 18:1 9t 18:1 9c; OA 18:1 11c; VA 18:2 9c,12c (n-6); LA 20:0 18:3 6c,9c,12c (n-6) 18:3 9c,12c,15c (n-3); ALA 20:1 8c (n-12) 21:0 20:2 11c,14c (n-6) 22:0 22:1 13c (n-9) 20:4 5c,8c,11c,14c (n-6) 23:0 24:0 24:1 15c 22:5 4c,7c,10c,13c,16c (n-6) ∑SFAb ∑MUFAc ∑PUFAd ∑n-3 ∑n-6
MATERIALS AND METHODS
Experimental Design. A total of 22 primiparous dairy cattle [7 Holstein (H), 8 Jersey (J), and 7 Holstein−Jersey crossbreeds (C)] were co-housed in free stalls at the Paul Miller Research Complex of the University of Vermont in South Burlington, VT, from May 2013 to May 2014. All cows calved within a 2-month period. The Institutional Animal Care and Use Committee of the University of Vermont approved all animal sampling procedures under protocol 13-031. Diet. At the start of their lactation, cows were transitioned to a TMR diet of corn silage (52.3% DM), haylage (15.9%), and concentrate (31.8%) that was consumed throughout the study. The concentrate contained corn grain (24.6%), citrus pulp (19.1%), amino max (16.4%), soybean meal (16.4%), canola meal (10.9%), amino enhancer (5.5%), calcium carbonate (2.5%), sodium sesquinate (2.2%), salt (1.2%), magnesium oxide (0.7%), trace mineral premix and vitamins (0.4%), zinc methionine (0.1%), and rumensin (
