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In cattle, there are 2 significant forms of vitamin D: ergocalciferol (ERG) from fungi on roughage and cholecalciferol (CHO) from vitamin supplements or endogenous synthesis in the skin. The hypothesis of the present study is that vitamin D from the 3 sources is transported in different plasma fractions in the body. This is hypothesized to explain the lower efficiency of ERG compared to CHO in securing a sufficient plasma status of 25-hydroxyvitamin D and explain the inefficient excretion of dietary CHO into milk compared to endogenous CHO. Twenty vitamin D-depleted cows were assigned to 5 treatments: D2, housed indoor and fed 625-μg/d (25.000 IU) ERG; D3, housed indoor and fed 625-μg/d CHO; D2+D3, housed indoor and fed 625-μg/d ERG and 625-μg/d CHO; SUN, let out for daily pasture to facilitate CHO synthesis from sunlight; and D2+SUN, fed 625-μg/d ERG and let out for daily pasture. Blood samples were taken twice weekly and plasma fractionated by ultracentrifugation into 3 fractions: light lipoprotein (LLP), heavy lipoprotein (HLP), and protein and analyzed for content of ERG and CHO and their liver derived metabolites 25-hydroxyergocalciferol (25ERG) and 25-hydroxycholecalciferol (25CHO), respectively. Liver biopsies were taken on the last day of the study to asses gene expression related to vitamin D metabolism. During 4 wk of study, the vitamin D status in plasma increased to 19.3 to 22.8 ng/mL 25ERG in ERG-treated cows with the highest concentration in D2 (P ≤ 0.05) and to 25.0 to 33.4 ng/mL 25CHO in pasture or CHO-treated cows with the highest concentration in SUN (P ≤ 0.01). In plasma fractions, CHO was mainly found in the HLP fraction, whereas 25CHO was almost exclusively found in the protein fraction, probably due to its reported high binding affinity to vitamin D-binding protein. About 70% to 90% of 25ERG was found in the protein fraction and the remaining 25ERG was found in HLP, whereas ERG was found in both HLP and LLP fractions. In liver tissue, the expression of vitamin D-25-hydroxylase was lower in D2+D3 (P ≤ 0.05) and SUN (P ≤ 0.05) than that in the remaining groups, and the vitamin D receptor was expressed in the liver to a larger extent in D2+SUN than that in D2+D3 (P ≤ 0.05) and SUN (P ≤ 0.05). In conclusion, different plasma transport mechanisms may explain the lower physiological efficiency of ERG compared to CHO in securing the vitamin D status in plasma but do not explain the lower efficiency of synthetic CHO compared to endogenous CHO from sunlight or UV light in securing a high CHO content in milk., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Starch is an important energy-providing nutrient for dairy cows that is most commonly provided from cereal grains. However, ruminal fermentation of large amounts of easily degradable starch leads to excessive production and accumulation of volatile fatty acids (VFA). VFA not only play a vital role in the energy metabolism of dairy cows but are also the main cause of ruminal acidosis and depressed feed intake. The aim of the present study was to compare maize cob silage (MCS) as an energy supplement in rations for dairy cows with highly rumen-digestible rolled barley and with sodium hydroxide wheat (SHW), which has a higher proportion of by-pass starch than barley. Two studies were carried out: (1) a production study on 45 Danish Holstein cows and (2) an intensive study to determine digestibilities, rumen fermentation patterns and methane emission using three rumen-cannulated Danish Holstein cows. Both studies were organised as a 3×3 Latin square with three experimental periods and three different mixed rations. The rations consisted of grass-clover silage and maize silage (~60% of dry matter (DM)), rapeseed cake, soybean meal, sugar beet pulp and one of three different cereals as a major energy supplement: MCS, SHW or rolled barley (~25% of DM). When MCS replaced barley or SHW as an energy supplement in the mixed rations, it resulted in a lower dry matter intake; however, the apparent total tract digestibilities of DM, organic matter, NDF, starch and protein were not different between treatments. The energy-corrected milk yield was unaffected by treatment. The fat content of the milk on the MCS ration was not different from the SHW ration, whereas it was higher on the barley ration. The protein content of the milk decreased when MCS was used in the ration compared with barley and SHW. From ruminal VFA patterns and pH measures, it appeared that MCS possessed roughage qualities with respect to rumen environment, while at the same time being sufficiently energy rich to replace barley and SHW as a major energy supplement for milk production. The environmental impact, expressed as methane emissions, was not different when comparing MCS, SHW and barley.

We investigated the influence of Swedish recommended vitamins A, D3 and E supplementation levels on muscle tenderness and fatty acid (FA) composition under indoor or outdoor finishing programmes. Swedish Red breed steer calves were divided into vitamin supplemented (n = 12) and non-supplemented (n = 15) groups while on pasture prior to the finishing period. This trial began at the beginning of the winter housing period during which the steers were fed a 55 : 45 dry matter barley : grass silage diet indoors. The indoor finished group was comprised of vitamin supplemented (n = 6) and non-supplemented (n = 8) steers slaughtered after about 155 days on feed. Vitamin supplemented steers were provided with 100 g mineral supplement providing 400 000 IU vitamin A, 100 000 IU D3 and 3000 IU E daily as recommended for Swedish production practices. In spring, outdoor finished vitamin supplemented (n = 6) and non-supplemented (n = 7) steers grazed semi-natural grassland for an additional 120 days before slaughter. During pasture, vitamin supplemented steers had free-choice access to a mineral supplement containing vitamins A, D3 and E. The mineral supplement for the non-supplemented steers did not contain vitamins A, D3 and E and was provided at the same amount as the vitamin supplemented steers. Shear force values were similar between vitamin supplemented and non-supplemented steers after ageing 2, 7 and 14 days within indoor and outdoor finishing programmes. The shear force values had decreased by 14 days of ageing within all programmes. The μ- and m-calpain activity did not differ between vitamin supplemented and non-supplemented steers for either the indoor or outdoor finishing programmes. The calpastatin activity was higher for the indoor, vitamin supplemented steers. Indoor finished vitamin supplemented steers had a greater proportion of C18:1c-9 and total monounsaturated fatty acids, whereas the non-supplemented steers had a greater proportion of total saturated fatty acids. We concluded that the meat quality from steers not receiving vitamin supplementation was similar to that of steers receiving vitamins A, D3 and E supplementation at Swedish recommended levels under indoor and outdoor finishing programmes.

Two physiologically important forms of vitamin D exist: vitamin D(2) and vitamin D(3), which by liver based hydroxylase enzymes are converted to 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3), respectively. These hydroxylated metabolites of vitamin D are measured in plasma to assess the vitamin D status of animals and humans. Therefore cheap and reliable analytical methods are very much in demand in nutritional and physiological research. After saponification and extraction of plasma or serum samples the current method uses reverse phase high performance liquid chromatography on a C(30) column and with UV detection at 265nm for quantifying vitamin D(2), vitamin D(3), 25-hydroxyvitamin D(2), and 25-hydroxyvitamin D(3). The method proved versatile with respect to plasma lipid content, sample amount, and plasma concentration of the vitamin D metabolites as it was tested using plasma from six different species: cattle, pigs, poultry, mink, horses, and humans. In cattle plasma recoveries were between 86.6 and 101.0%, within day error between 0.9 and 5.9%, and between day error between 0.2 and 1.7%. However, depending on species and sample amount error percentages varied. When running the method on standard reference material® 972 "Vitamin D in human serum" from the National Institute of Standards and Technology (NIST) (Gaithersburg, USA) the results for 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) concentrations were within the boundaries provided by NIST, reflected by Z-scores between 0.1 and 0.9., (Copyright © 2011 Elsevier B.V. All rights reserved.)