Transcriptome adaptation of the bovine mammary gland to diets rich in unsaturated fatty acids shows greater impact of linseed oil over safflower oil on gene expression and metabolic pathways

Differentially expressed genes implicated in apoptosis of cows in LSO treatment as compared to the same cows on the control diet. Expression direction of several genes predicted to decrease apoptosis. (DOCX 35 kb

Prediction of nitrogen excretion from data on dairy cows fed a wide range of diets compiled in an intercontinental database: a meta-analysis

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Effect of Metabolizable Protein Supply on Milk Performance, Ruminal Fermentation, Apparent Total-Tract Digestibility, Energy and Nitrogen Utilization, and Enteric Methane Production of Ayrshire and Holstein Cows

In North America, the nutrient requirements of dairy cattle are predicted using the Cornell Net Carbohydrate and Protein System (CNCPS) or the National Research Council (NRC). As Holstein is the most predominant dairy cattle breed, these models were developed based on the phenotypic, physiological, and genetic characteristics of this breed. However, these models may not be appropriate to predict the nutrient requirements of other breeds, such as Ayrshire, that are phenotypically and genetically different from Holstein. The objective of this study was to evaluate the effects of increasing the metabolizable protein (MP) supply using CNCPS on milk performance, ruminal fermentation, apparent total-tract digestibility, energy and N utilization, and enteric methane production in Ayrshire vs. Holstein lactating dairy cows. Eighteen (nine Ayrshire; nine Holstein) lactating cows were used in a replicated 3 × 3 Latin square design (35-d periods) and fed diets formulated to meet 85%, 100%, or 115% of MP daily requirement. Except for milk production, no breed × MP supply interaction was observed for the response variables. Dry matter intake (DMI) and the yields of energy-corrected milk (ECM), fat, and protein were less (p < 0.01) in Ayrshire vs. Holstein cows. However, feed efficiency and N use efficiency for milk production did not differ between the two breeds, averaging 1.75 kg ECM/kg DMI and 33.7 g milk N/100 g N intake, respectively. Methane yield and intensity and urinary N also did not differ between the two breeds, averaging 18.8 g CH4 /kg DMI, 10.8 g CH4 /kg ECM, and 27.6 g N/100 g N intake, respectively. Yields of ECM and milk protein increased (p ≤ 0.01) with increasing MP supply from 85% to 100% but no or small increases occurred when MP supply increased from 100 to 115%. Feed efficiency increased linearly with an increasing MP supply. Nitrogen use efficiency (g N milk/100g N intake) decreased linearly (by up to 5.4 percentage units, (p < 0.01) whereas urinary N excretion (g/d or g/100 g N intake) increased linearly (p < 0.01) with an increasing MP supply. Methane yield and emission intensity were not affected by MP supply. This study shows that feed efficiency, N use efficiency, CH4 (yield and intensity), and urinary N losses did not differ between Ayrshire and Holstein cows. Energy-corrected milk yield and feed efficiency increased, but N use efficiency decreased and urinary N losses increased with increasing dietary MP supply regardless of breed. Ayrshire and Holstein breeds responded similarly to increasing MP levels in the diet

Diet-Induced Alterations in Total and Metabolically Active Microbes within the Rumen of Dairy Cows

<div><p>DNA-based techniques are widely used to study microbial populations; however, this approach is not specific to active microbes, because DNA may originate from inactive and/or dead cells. Using cDNA and DNA, respectively, we aimed to discriminate the active microbes from the total microbial community within the rumen of dairy cows fed diets with increasing proportions of corn silage (CS). Nine multiparous lactating Holstein cows fitted with ruminal cannulas were used in a replicated 3×3 Latin square (32-d period; 21-d adaptation) design to investigate diet-induced shifts in microbial populations by targeting the rDNA gene. Cows were fed a total mixed ration with the forage portion being either barley silage (0% CS), a 50∶50 mixture of barley silage and corn silage (50% CS), or corn silage (100% CS). No differences were found for total microbes analyzed by quantitative PCR, but changes were observed within the active ones. Feeding more CS to dairy cows was accompanied by an increase in <i>Prevotella</i> rRNA transcripts (<i>P</i> = 0.10) and a decrease in the protozoal rRNA transcripts (<i>P</i><0.05). Although they were distributed differently among diets, 78% of the amplicons detected in DNA- and cDNA-based fingerprints were common to total and active bacterial communities. These may represent a bacterial core of abundant and active cells that drive the fermentation processes. In contrast, 10% of amplicons were specific to total bacteria and may represent inactive or dead cells, whereas 12% were only found within the active bacterial community and may constitute slow-growing bacteria with high metabolic activity. It appears that cDNA-based analysis is more discriminative to identify diet-induced shifts within the microbial community. This approach allows the detection of diet-induced changes in the microbial populations as well as particular bacterial amplicons that remained undetected using DNA-based methods.</p> </div

Indicator value (IV, %) of the bacterial LH-<i>rrs</i> fingerprints from lactating cows (<i>n = 9</i>) fed diets with 0, 50 or 100% corn silage (CS).

1<p>IV  =  relative abundance × relative frequency. Maximum IV for each amplicon is underlined.</p>2<p>Standard deviation.</p>3<p>IV were tested for significance using a Monte Carlo technique.</p

Principal component analysis ordination of bacterial LH-<i>rrs</i> amplicons that compose the total and the metabolically active bacterial communities.

<p>Total ruminal content (<i>n</i> = 9 cows for each diet) was collected before the a.m. feeding from dairy cows fed 0, 50 or 100% corn silage (CS). The percentage of total variance accounted for by each of the two principal components (PC1 and PC2) is shown in parentheses.</p

Bacterial diversity indices in lactating cows (<i>n</i> = 9) fed diets with 0, 50 or 100% corn silage (CS).

<p>Bacterial diversity indices in lactating cows (<i>n</i> = 9) fed diets with 0, 50 or 100% corn silage (CS).</p

Abundance of <i>rrs</i> and <i>mcrA</i> gene copies and transcripts in total ruminal content of lactating cows (<i>n</i> = 9) fed diets with 0, 50 or 100% corn silage (CS)¹.

1<p>Results are expressed as log₁₀ gene copies/g DM of total ruminal content.</p>a, b, A, B<p>Within a row, means without a common superscript differ significantly (<i>P</i>≤0.05) for lowercase letters or tended (0.05<<i>P</i>≤0.10) to differ for uppercase letters.</p