This study evaluated the effects of feeding fresh forage either as pasture plus a concentrate (PAS) or as a silage-based total mixed ration (TMR), combined with either a ruminally inert lipid supplement high in saturated fatty acids (-) or a ruminally protected microalgae containing 22 g of docosahexaenoic acid (DHA)/100 g of fatty acids (+) on the fatty acid (FA) composition and oxidation of milk and butter. For the 8 mid-lactation Holstein cows in this study, milk yield was not significantly affected by treatment, averaging 32.3 ± 1.28 kg/d. Milk fat content was higher for PAS⁻, averaging 5.05 compared with 4.10 ± 0.17% for the mean of other treatments, and was significantly depressed with microalgae supplementation (3.97 vs. 4.69 ± 0.17%). The saturated fatty acid level in the milk of cows fed TMR⁻ was significantly higher than that of the other treatments (66.9 vs. 61.2 g/100 g of FA). The level of monounsaturated FA was lowered by feeding TMR⁻ (27.4 vs. 32.0 g/100 g of FA), whereas levels of polyunsaturated FA were elevated by feeding PAS+ compared with the mean of the other treatments (6.54 vs. 5.07 g/100 g of FA). Feeding the rumen-protected microalgae increased the DHA content of milk more than 4-fold (0.06 to 0.26 g/100g of FA) with the PAS treatment. The conjugated linoleic acid content of milk was highest for PAS+ compared with the other treatments (4.18 vs. 3.41 g/100g of FA). In general, the fatty acid composition of butter followed that of milk. Overall, feeding the TMR supplemented with the rumen-protected microalgae increased the levels of volatile products of oxidation in milk and butter. No effect of forage type or microalgae supplementation was observed on the oxidative stability or antioxidant capacity of milk, although the oxidative stability of butter exposed to UV was reduced with microalgae supplementation, particularly with TMR, as assessed by using the ferric reducing ability of plasma assay.

The objective of this study was to examine the interaction between lipid supplement (LS) and management system (MS) on fatty acid (FA) composition of milk that could affect its healthfulness as a human food. Forty-eight prepartal Holstein cows were blocked by parity and predicted calving date and deployed across pasture (PAS; n=23) or confinement (CONF; n=25) systems. Cows within each system were assigned randomly to a control (no marine oil supplement) or to 1 of 2 isolipidic (200 g/d) marine oil supplements: fish oil (FO) or microalgae (MA) for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole-plot treatment and LS as the subplot treatment. Cows were housed in a tie-stall barn from -30 until 28 ± 10 d in milk (DIM) and were fed total mixed rations with similar formulations. The PAS group was then adapted to pasture and rotationally grazed on a perennial sward until the end of the experiment (95 ± 5 DIM). Milk samples were collected at 60 and 90 DIM for major components and FA analyses. Milk yield (kg/d) was lower in PAS (34.0) compared with CONF (40.1) cows. Milk fat percentage was reduced with MA compared with FO (3.00 vs. 3.40) and the control (3.56) cows. However, milk fat yield (kg/d) was not affected by lipid supplements. Compared with CONF, PAS cows produced milk fat with a lower content of 12:0 (-38%), 14:0 (-28%), and 16:0 (-17%), and more cis-9 18:1 (+32%), 18:3 n-3 (+30%), conjugated linoleic acid (CLA; +70%) and trans 18:1 (+34%). Both supplements, regardless of MS, reduced similarly the milk fat content of 16:0 (-12%) and increased CLA (+28%) and n-3 long-chain polyunsaturated FA (n-3 LC-PUFA; +150%). Milk fat content of trans 18:1 (trans-6 to trans-16) was increased with FO or MA, although the effect was greater with MA (+81%) than with FO (+42%). The interaction between MS and LS was significant only for trans-11 18:1 (vaccenic acid, VA) and cis-9,trans-11 CLA (rumenic acid). In contrast to CONF, feeding FO or MA to PAS cows did not increase milk fat content of VA and rumenic acid. We concluded that compared with CONF, milk from PAS cows had a more healthful FA composition. Feeding either FO or MA improved n-3 long-chain polyunsaturated FA and reduced levels of 16:0 in milk fat, regardless of MS, but concurrently increased the trans 18:1 isomers other than VA, at the expense of VA, particularly in grazing cows.

Despite its large size (200 -2400 kilobase pairs), the mitochondrial genome of angiosperms does not encode the minimal set of tRNAs required to support mitochondrial protein synthesis. Here we report the identification of cytosolic-like tRNAs in wheat mitochondria using a method involving quantitative hybridization to distinguish among three tRNA classes: (i) those encoded by mitochondrial DNA (mtDNA) and localized in mitochondria, (ii) those encoded by nuclear DNA and located in the cytosol, and (iii) those encoded by nuclear DNA and found in both the cytosol and mitochondria. The latter class comprises tRNA species that are considered to be imported into mitochondria to compensate for the deficiency of mtDNA-encoded tRNAs. In a comprehensive survey of the wheat mitochondrial tRNA population, we identified 14 such imported tRNAs, the structural characterization of which is presented here. These imported tRNAs complement 16 mtDNA-encoded tRNAs, for a total of at least 30 distinct tRNA species in wheat mitochondria. Considering differences in the set of mtDNA-encoded and imported tRNAs in the mitochondria of various land plants, the import system must be able to adapt relatively rapidly over evolutionary time with regard to the particular cytosolic-like tRNAs that are brought into mitochondria.

Research was conducted to evaluate the effects of management system (MS), marine lipid supplementation (LS), and their interaction on the relative mRNA abundance of 11 genes involved in lipid synthesis in mammary, liver, and subcutaneous adipose tissues in lactating dairy cows. These genes included those involved in FA uptake (LPL), de novo FA synthesis (ACACA, FASN), FA desaturation (SCD1, FADS1, FADS2), and transcriptional regulation of lipogenesis (SREBF1, SCAP, INSIG1, THRSP, and PPARG). Forty-eight peripartal Holstein cows were blocked by parity and predicted calving date and assigned to either a pasture (n=23) or confinement (n=25) system. Within each system, cows were allocated randomly (7-9 cows per treatment) to a control (no oil supplement) or 1 of 2 isolipidic (200 g/d) supplements, fish oil (FO) or microalgae (MA), for 125 ± 5 d starting 30 d precalving. The experiment was conducted as a split-plot design, with MS being the whole plot treatment and LS as the subplot treatment. At 100 ± 2 DIM, 4 cows from each treatment combination (24 cows in total) were euthanized and tissue samples were collected for gene expression analysis. No interactions between MS and LS were observed regarding any of the variables measured in this study. Milk production (34.0 vs. 40.1 kg/d), milk fat (1.10 vs. 1.41 kg/d), protein (0.95 vs. 1.22 kg/d), and lactose (1.56 vs. 1.86 kg/d) were lower for pasture compared with confinement. The effect of LS on milk production and milk composition (yields and contents) was significant only for milk fat content that was reduced with MA compared with FO (3.00 vs. 3.40%) and the control (3.56%). The mammary mRNA abundance of PPARG (-32%) and FASN (-29%) was lower in grazing compared with confined cows, which was accompanied by reduced (-43%) secretion of de novo synthesized fatty acids in milk. Grazing was associated with reduced expression of ACACA (-48%), FASN (-48%), and THRSP (-53%) in subcutaneous adipose tissues, which was consistent with the lower body condition score (i.e., lower net adipose tissue deposition) in grazing compared with confined cows. Feeding either FO or MA downregulated hepatic expression of FASN, SCD1, FADS2, and THRSP. The reduced secretion of de novo synthesized fatty acids in milk of grazing cows compared with confined cows might be related in part to the downregulation of genes involved in lipid synthesis, and that LS have tissue-specific effects on expression of genes involved in lipid metabolism, with liver being the most responsive tissue.

ARTICLEInteractions between cultivars of legume species (Trifolium pratense L., Medicago sativa L.) and grasses (Phleum pratense L., Lolium perenne L.) under different nitrogen levels Abstract: The transfer of nitrogen (N) from legumes to grasses is an important process in low-input forage production systems, and may be improved by selecting compatible species and cultivars. This study sought to examine what effect species and cultivar have on plant growth and N accumulation in temperate grass-legume mixtures under a range of nitrogen fertility levels. A pot study using two cultivars each of alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), perennial ryegrass (Lolium perenne L.), and timothy (Phleum pratense L.) in all grasslegume combinations was devised. Compatibility indices, based on plant performance grown in combination versus alone, were used to quantify the net impact legumes and grasses had on each other. The presence of legumes had an overall negative effect on the growth of grasses (87% compared with growing alone), but did improve tissue N content by weight and total accumulated N. Improvements in total N were highest in a single timothy cultivar (Champ; 169%), but highest net total N was achieved in a ryegrass cultivar (Bastion; 1.92 mg N). Results indicate that grass N accumulation in legume-grass mixtures may be influenced more by grass N demand than legume supply, which suggests that competition between grasses and legumes may be a major determinant of N transfer efficiency.Résumé : Le transfert d'azote (N) des légumineuses aux graminées est un processus important dans les régimes de culture fourragère à faibles intrants et on pourrait l'intensifier en sélectionnant des espèces et des cultivars compatibles. Cette étude devait préciser dans quelle mesure l'espèce et le cultivar agissent sur la croissance de la plante et l'accumulation de N dans les mélanges combinant graminées et légumineuses pour climats tempérés, compte tenu d'un degré de fertilité variable pour l'azote. Les auteurs ont réalisé une expérience en pot sur deux cultivars, dans chaque cas, de luzerne (Medicago sativa L.), de trèfle rouge (Trifolium pratense L.), de raygrass vivace (Lolium perenne L.) et de fléole (Phleum pratense L.) en combinaisons graminées-légumineuses. Ils se sont servis d'indices de compatibilité s'appuyant sur la performance des plantes cultivées ensemble par rapport à leur performance lorsqu'elles sont cultivées seules, afin de quantifier l'impact net des légumineuses sur les graminées, et vice-versa. Les légumineuses ont un effet généralement négatif sur la croissance des graminées (87 % par rapport à la croissance observée sans compagnon), mais elles rehaussent la teneur en N dans les tissus selon le poids ainsi que la quantité totale de N accumulée. La hausse du N total la plus élevée a été observée chez un unique cultivar de fléole (Champ; 169 %), mais la plus forte hausse nette du N total a été obtenue avec un cultivar de raygrass (Bastion; 1,92 mg de N). Ces résultats indiquent que l'accu...