Milk fatty acid composition is determined by several factors including diet. The milk fatty acid profile of dairy cows is low in polyunsaturated fatty acids, especially those of the n-3 series. Efforts to change and influence fatty acid profile with longer chain polyunsaturated fatty acids have proven challenging. Several barriers prevent easy transfer of dietary polyunsaturated fatty acids to milk fat including rumen biohydrogenation and fatty acid esterification. The potential for cellular uptake and differences in fatty acid incorporation into milk fat might also have an effect, though this has received less research effort. Given physiological impediments to enriching milk fat with polyunsaturated fatty acids, manipulating the genome of the cow might provide a greater increase than diet alone, but this too may be challenged by the physiology of the cow.

We evaluated the effects of source of corn silage and trace minerals on lactational performance and totaltract digestibility (TTD) of nutrients in 16 Holstein cows averaging 82 (standard error = 3) days in milk in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments with 28-d periods. The diets consisted [dry matter (DM) basis] of 55% conventional (CON) or brown midrib-3 (BM3) corn silage, 2% chopped wheat straw, and 43% grain mix with either sulfate (STM) or hydroxy (HTM) sources of copper, manganese, and zinc trace minerals. The targeted supplemental concentrations of copper, zinc, and manganese were 194, 1,657, and 687 mg/d, respectively. The dietary treatments were CON-STM, CON-HTM, BM3-STM, and BM3-HTM. The dietary nutrient composition of the BM3 diets averaged 32.1% amylase neutral detergent fiber on an organic matter basis (aNDFom) and 6.9% undigested neutral detergent fiber at 240 h (uNDF240om; % of DM), and CON diets averaged 36.2% aNDFom and 8.6% uNDF240om (% of DM). The average supplemental concentrations of copper, zinc, and manganese for the STM diets were 10, 41, and 64 mg/kg, respectively, and the average supplemental concentrations of copper, zinc, and manganese for the HTM diets were 10, 40, and 62 mg/kg, respectively. The average total dietary concentrations of copper, zinc, and manganese for the STM diets were 17, 104, and 60 mg/kg, respectively, and the average total dietary concentrations of copper, zinc, and manganese for the HTM diets were 17, 91, and 66 mg/ kg, respectively. Data were summarized by period and analyzed as a replicated Latin square design with fixed model effects for corn silage, trace minerals, corn silage × trace mineral interaction, period within replicated square, and replicated square using the MIXED procedure of SAS. Cow within replicated square was a random effect. Cows fed the BM3 diets had greater dry matter intake (DMI) and milk yield (28.1 and 47.0 kg/d) than cows fed the CON diets (27.5 and 44.7 kg/d). We found no significant interaction between corn silage and trace minerals for DMI and milk yield. Cows fed the HTM diets (28.1 kg/d) had a greater DMI than cows fed the STM diets (27.5 kg/d). Cows fed the BM3 diets had greater TTD of DM and OM (72.8 and 74.1% of DM) than cows fed the CON diets (71.1 and 72.3% of DM). Cows fed the HTM diets had a tendency for greater TTD of aNDFom than cows fed the STM diets (56.8 vs. 54.9% of DM). Cows fed the CON diets ruminated longer during the day than cows fed the BM3 diets (524 vs. 496 min/d). Corn silage with greater NDF digestibility and lower uNDF240om enhanced DMI, milk yield, and TTD of DM and OM, and hydroxy trace minerals improved DMI and tended to improve TTD of aNDFom. The source of corn silage and trace minerals should be taken into consideration when formulating diets for high-producing dairy cows.

This study assessed the effects of enhanced dietary plane of nutrition (early nutritional program (ENH)) on the gene expression pattern of ruminal epithelial tissue of young Holstein calves. Male Holstein calves were fed (3 to 42 days of age) with reconstituted control milk replacer (MR) (20 % crude protein, 20 % fat; 1.25 lb solids/calf) plus conventional starter (CON; 19.6 % crude protein, dry matter basis) or a high-protein MR (ENH; 28.5 % crude protein, 15 % fat; at around 2 % of body weight) plus high-crude protein starter (25.5 % crude protein, dry matter basis). The calves were weaned on day 43. Groups of calves in CON and ENH treatment were harvested after 5 and 10 weeks of feeding. The ruminal epithelium from five calves in each group was used for transcript profiling using a bovine oligonucleotide microarray. The postweaning mass of the reticulo-rumen was greater (P < 0.01) in calves consuming ENH. Transcriptome analysis revealed that 208 genes were altered due to treatment and 587 due to time alone. Bioinformatics analysis revealed that "galactose metabolism," "citrate cycle," "pyruvate metabolism," and "basal transcription factors" were the most impacted and induced pathways due to feeding ENH; whereas, "valine, leucine, and isoleucine biosynthesis" and "glyoxylate and dicarboxylate metabolism" were among the most inhibited. The integrated interpretation of the results suggested an overall increase in metabolism after weaning, particularly biosynthesis of glycan and nucleotide metabolism. Furthermore, the preweaning alterations in the transcriptome were mostly associated with cell growth, death, tissue development, and cellular morphology. The postweaning response revealed overexpression of genes associated with cell adhesion molecules, p53 signaling, and fatty acid metabolism. Our results indicated that feeding ENH to young Holstein calves elicited a strong transcriptomic response in the ruminal epithelial tissue.