Effect of Thermal Processing on Estimated Metabolizable Protein Supply to Dairy Cattle from Camelina Seeds: Relationship with Protein Molecular Structural Changes

This study evaluated the effect of thermal processing on the estimated metabolizable protein (MP) supply to dairy cattle from camelina seeds (Camelina sativa L. Crantz) and determined the relationship between heat-induced changes in protein molecular structural characteristics and the MP supply. Seeds from two camelina varieties were sampled in two consecutive years and were either kept raw or were heated in an autoclave (moist heating) or in an air-draft oven (dry heating) at 120 °C for 1 h. The MP supply to dairy cattle was modeled by three commonly used protein evaluation systems. The protein molecular structures were analyzed by Fourier transform/infrared-attenuated total reflectance molecular spectroscopy. The results showed that both the dry and moist heating increased the contents of truly absorbable rumen-undegraded protein (ARUP) and total MP and decreased the degraded protein balance (DPB). However, the moist-heated camelina seeds had a significantly higher (<i>P</i> < 0.05) content of ARUP and total MP and a significantly lower (<i>P</i> < 0.05) content of DPB than did the dry-heated camelina seeds. The regression equations showed that intensities of the protein molecular structural bands can be used to estimate the contents of ARUP, MP, and DPB with high accuracy (<i>R</i>² > 0.70). These results show that protein molecular structural characteristics can be used to rapidly assess the MP supply to dairy cattle from raw and heat-treated camelina seeds

Immunization against Rumen Methanogenesis by Vaccination with a New Recombinant Protein

<div><p>Vaccination through recombinant proteins against rumen methanogenesis provides a mitigation approach to reduce enteric methane (CH₄) emissions in ruminants. The objective of present study was to evaluate the <i>in vivo</i> efficacy of a new vaccine candidate protein (EhaF) on methanogenesis and microbial population in the rumen of goats. We amplified the gene mru 1407 encoding protein EhaF using fresh rumen fluid samples of mature goats and successfully expressed recombinant protein (EhaF) in <i>Escherichia coli</i> Rosetta. This product was evaluated using 12 mature goats with half for control and other half injected with 400ug/goat the purified recombinant protein in day 1 and two subsequent booster immunizations in day 35 and 49. All measurements were undertaken from 63 to 68 days after the initial vaccination, with CH₄ emissions determined using respiration calorimeter chambers. The results showed that the vaccination caused intensive immune responses in serum and saliva, although it had no significant effect on total enteric CH₄ emissions and methanogen population in the rumen, when compared with the control goats. However, the vaccination altered the composition of rumen bacteria, especially the abundance of main phylum Firmicutes and genus <i>Prevotella</i>. The results indicate that protein EhaF might not be an effective vaccine to reduce enteric CH4 emissions but our vaccine have potential to influence the rumen ecosystem of goats.</p></div

Effects of the vaccination treatment on abundance of main phylum and taxa (mean ± SD) in goats (<i>n</i> = 12).

<p>*Taxa that could not be assigned a genus were displayed using the highest taxonomic level that could be assigned to them.</p><p>Effects of the vaccination treatment on abundance of main phylum and taxa (mean ± SD) in goats (<i>n</i> = 12).</p

Methane production of goats.

<p>Symbols are methane emission of each goat in control (●) and vaccination (■) group. The error bars represent standard deviation of the means.</p

Mass spectrometry identification of recombinant protein EhaF.

<p>There were eight matched peptides (Shown in red) and four of them were matched with expected sequence in MS/MS analysis, which were in line.</p

Prokaryotic expression analysis of the recombinant protein EhaF on SDS-PAGE.

<p>The recombinant protein was induced with 0.2% ɑ-lactose at 30°C for 16 h. Lanes 1: induced whole-cell harboring pET 30a (+) lysate; Lanes 2: induced whole-cell harboring pET 30a (+)-mru1407 lysate; Lanes3: purified protein after concentrated. The arrowhead points out the position of target protein.</p

Effects of the vaccination treatment on IgG titres against recombinant protein EhaF (mean ± SD) in goats (<i>n</i> = 12).

<p>The titres were defined as the reciprocal of the dilution that gave half the maximal optical density.</p

The relative abundance of the phyla of microbes in each group.

<p>Each colour represents one phylum and the length indict the mean percentage of each phylum among the whole microbes.</p

Effects of the vaccination treatment on abundance of each taxonomic level of Euryarchaeota phylum (mean ± SD) in goats (<i>n</i> = 12).

<p>Effects of the vaccination treatment on abundance of each taxonomic level of Euryarchaeota phylum (mean ± SD) in goats (<i>n</i> = 12).</p

The indices of alpha diversity (mean ± SD) of microbes in each treatment group of goats (<i>n</i> = 12).

<p>The indices of alpha diversity (mean ± SD) of microbes in each treatment group of goats (<i>n</i> = 12).</p