No abstract

Fifty-six autumn-calving Holstein-Friesian cows, blocked on the basis of days in milk (27.6 +/- 10.65 d), lactation number (3.1 +/- 2.21), and preexperimental milk yield (28.4 +/- 6.69 kg) were used to examine the effects of replacing 330 g/kg of dry matter (DM) of first-cut perennial ryegrass silage with either fermented whole-crop wheat (WCW), urea-treated processed WCW, or corn silage on subsequent feed intake, milk production, and efficiency of nitrogen utilization. The DM (g/kg), crude protein (CP, g/kg of DM) and in vitro DM digestibility (g/kg) of the forages were 204, 179, and 762 for grass silage; 389, 90, and 711 for fermented WCW; 795, 141, and 768 for urea-treated processed WCW; and 346, 93, and 783 for corn silage, respectively. Four forage treatments were evaluated as follows: 1) grass silage as the sole forage (GS); 2) a mixture of grass silage and fermented WCW silage, (F-WCW); 3) a mixture of grass silage and urea-treated processed WCW, (UP-WCW); and 4) a mixture of grass silage and corn silage (CS). In all cases, the alternative forages comprised 67% of the forage mix on a DM basis. Isonitrogenous diets were formulated by offering all cows 8 kg of concentrate as fed, formulated to different CP concentrations. Cows were offered these diets from 28 to 104 d in milk. Total DM intake and milk yield were greater on UP-WCW (20.0 and 30.2 kg/d) and CS (18.3 and 33.2 kg/d) than on GS (13.5 and 26.5 kg/d). Although DM intake was greater on F-WCW (17.1 kg/d) than on GS, milk yield was not significantly greater (+2.7 kg/d). Milk protein concentration was greater on F-WCW (30.5 g/kg), UP-WCW (31.3 g/kg), and CS (30.7 g/kg) than on GS (28.5 g/kg). However, there was no difference between treatments in milk fat or lactose concentrations. Body weight change was greater for cows offered GS (-0.27 kg/d) than for those offered UP-WCW (-0.01 kg/d) and CS (+0.05 kg/d) but not compared with those offered F-WCW (-0.06 kg/d). There was no effect of treatment on plasma glucose, nonesterified fatty acids, beta-hydroxybutyrate, urea, or total protein at d 64 +/- 17.4 and d 92 +/- 17.4 postpartum. Efficiency of N utilization was greatest for CS with 0.36 of N intake being recovered in milk compared with 0.28, 0.32, and 0.26 for GS, F-WCW, and UP-WCW, respectively. There was no effect of treatment on milk urea N concentration or the urinary allantoin N to creatinine N ratio. The results of this experiment indicate that corn silage is a more suitable supplementary forage to grass silage than fermented or urea-treated processed WCW, with advantages realized in milk production and more efficient N utilization.

Over the past 15 years the Corey-Chaykovsky (CC) epoxidation process 1 involving the reaction between sulfonium ylides and aldehydes has evolved into a highly synthetically useful, catalytic asymmetric methodology. 2The use of semistabilized ylides such as those derived from the reaction of either benzyl halides or α-haloesters/amides with chiral sulfides at catalytic loadings can result in excellent levels of product enantiomeric excess.3 In stark contrast however, the asymmetric synthesis of terminal epoxides via methylene transfer is characterized by moderate yields and a requirement for (super)stoichiometric loadings of chiral sulfide catalysts. 4,5 For example, the benchmark literature procedures (Scheme 1) for the asymmetric sulfonium ylide-mediated formation of styrene oxide (2) from the archetypal substrate benzaldehyde (1) developed independently by Aggarwal 6a,b and Goodman 6c involve the use of 100-200 mol% of the chiral sulfides 3-4 and produce 2 in ca. 50-60% yield and <60% ee. 7 Hiyama et al. (ref. 7a) claimed that 2 could be synthesized in 97% ee in the presence of a chiral phase transfer catalyst. However our group (ref. 7b) recently demonstrated that Hiyama was in error and has actually observed the decomposition of the catalyst to a related epoxide (with a relatively large specific rotation) during the formation of 2 as a racemate: (a) Hiyama, T.; Mishima, T.; Sawada, H.; Nozaki, H. J. Am.

The highly efficient asymmetric epoxidation of aldehydes by methylene transfer is now possible using new sulfonium salts.The importance of chiral epoxides as synthetic building blocks in asymmetric synthesis is extremely difficult to overstate. While the highly enantioselective Sharpless, 1,2 and JacobsenKatsuki, [3][4][5] protocols for the epoxidation of internal alkenes are now mature technologies of inestimable value, the conversion of terminal alkenes to enantioenriched 1-oxiranes has proven a considerably more difficult process to control. 5,6 Arguably the current method of choice (in terms of product ee) for the catalytic synthesis of these molecules is the Co-salen complexcatalysed kinetic resolution of racemic epoxides. 6a,7,8 While progress towards the efficient asymmetric oxidation of terminal alkenes has been made -e.g. Fe/Mn-porphyrin complexes, 9 chiral Ti 10 and Pt-complexes 11 and chiral dioxiranes (styrene substrates only), 12 the difficulties in preparing terminal epoxides in 490% ee via alkene oxidation has fostered interest in alternative protocols. 13 One methodology which holds promise is catalytic methylene transfer to aldehydes mediated by sulfonium ylides.14 Since it is often from the aldehyde that the alkene substrate for oxidation processes is prepared, a methylene transfer reaction would represent a more direct synthesis of the product, which could potentially be performed in an operationally simple manner, in a transition metal-ion free environment. The stabilised-and semi-stabilised sulfonium ylide-mediated asymmetric epoxidation of aldehydes catalysed by chiral sulfides has proven a highly useful process for the formation of 1,2-disubstituted epoxides with excellent product diastereo-and enantioselectivity. 15,16 In an unfortunate parallel to the alkene oxidation methodologies, the corresponding sulfonium ylide-mediated aldehyde oxidation to form terminal epoxides (nearly 40 years after the first disclosed asymmetric attempt) 17 is characterised by moderate yields and low-moderate levels of product enantiomeric excess.18-22 For instance, both benchmark methodologies (A and B, developed by Goodman 19 and Aggarwal 20 respectively, Scheme 1) for the conversion of the archetypal substrate benzaldehyde (1) to styrene oxide (2) involve the employment of (super)stoichiometric loadings of a chiral sulfide and a Simmons-Smith type Zn-carbenoid, and furnish the product in o60% yield and ee. In an attempt to develop a more atom-economic process, we have shown that the ylide can be generated via an alkylation and subsequent deprotonation route (C, Scheme 1).23,24b Sulfide 6 could be utilised at 20 mol% loading if the alkylating agent and base were added portion-wise, however no progress was made towards improving upon the mediocre enantioselectivity which bedevils this (otherwise) potentially very useful reaction.With the goal of solving this problem, we reflected upon the likely causes of the low enantioselectivity. The first major difficulty -as Aggarwal 14b has pointed out -associated with...