Five lactating dairy cows with a permanent cannula in the rumen were given (kg DM/d) a normal diet (7.8 concentrates, 5.1 hay) or a low-roughage (LR) diet (11.5 concentrates, 1.2 hay) in two meals daily in a two-period crossover design. Milk fat (g/kg) was severely reduced on diet LR. To measure rates of production of individual volatile fatty acids (VFA) in the rumen, 0.5 mCi 1-(14)C-acetic acid, 2-(14)C-propionic acid, or 1-(14)C-n-butyric acid were infused into the rumen for 22 h at intervals of 2 to 6 d; rumen samples were taken over the last 12 h. To measure rumen volume, we infused Cr-EDTA into the rumen continuously, and polyethylene glycol was injected 2 h before the morning feed. Results were very variable, so volumes measured by rumen emptying were used instead. Net production of propionic acid more than doubled on LR, but acetate and butyrate production was only numerically lower. Net production rates pooled across both diets were significantly related to concentrations for each VFA. Molar proportions of net production were only slightly higher than molar proportions of concentrations for acetate and propionate but were lower for butyrate. The net energy value (MJ/d) of production of the three VFA increased from 89.5 on normal to 109.1 on LR, equivalent to 55 and 64% of digestible energy, respectively. Fully interchanging, three-pool models of VFA C fluxes are presented. It is concluded that net production rates of VFA can be measured in non-steady states without the need to measure rumen volumes.

Twenty-four Friesian cows were allocated to one of four diets for weeks 3-14 of lactation following 2 weeks on a common diet. The diets (kg air-dry feed/day) were 7-2 kg hay and 10-8 kg either starchy or fibrous concentrates (60S and 60F) or 3-5 kg hay and 14-0 kg either starchy or fibrous concentrates (80S and 80F). Rumen samples were taken by stomach tube in weeks 10 and 12 of lactation and the digestibility of the diets was measured with four cows per treatment during weeks 13 and 14. The digestibility of the same feeds was also measured in sheep at maintenance.The principal carbohydrate constituents of the concentrates were barley, wheat and cassava in the starchy concentrates and citrus pulp, sugar-beet pulp and wheat feed in the fibrous concentrates. The concentrates were designed to have similar concentrations of metabolizable energy (ME) and the diets were planned to provide similar intakes of digestible energy and crude protein.Milk yield and composition were very similar for treatments 60S and 60F. With the higher proportion of starchy concentrates (80S), milk yield was about 20% greater than on 60S, fat concentration fell severely but protein and lactose concentrations were unaffected. With the higher proportion of fibrous concentrates (80F), milk yield and the protein and lactose concentration were similar to values on 60F but fat concentration was lower, though not nearly so low as on 80S. Milk energy yield was reduced by the higher proportion of concentrates but was unaffected by type of carbohydrates. Live-weight changes were small.In both the sheep, consuming at maintenance, and the lactating cows consuming at about 3 times maintenance, digestibility of dry matter, organic matter and energy was higher with the higher concentrate diets but was unaffected by type of concentrate. The digestibility of fibre was greater with the fibrous concentrates but the effect of level of concentrate inclusion was inconsistent. Digestibility coefficients were consistently lower for the lactating cows than for the sheep.The proportion of acetic acid in the rumen volatile fatty acids in the cows was higher and the proportion of propionic acid was lower with the fibrous concentrates. The differences were much greater with the higher proportion of concentrates.During weeks 15-22 of lactation the cows were reallocated to concentrate treatments and given hay ad libitum. Hay intake was about 1 kg/day higher with the fibrous concentrates but the difference was not significant. Hay intake fell by about 0'6 kg/kg concentrate intake for both concentrate types. No significant differences in milk yield or composition were established, probably because of incomplete adaptation even after 8 weeks.

Four lactating Friesian cows with permanent cannulas in the rumen and proximal duodenum were given early (EC)-or late (LC)-cut grass silage ad fib., each with either 3 or 9 kg concentrate dry matter (DM)/d in a 4 x 4 Latin square design starting about 10 weeks after calving. Feed was offered twice daily a t 08.30 hours and 15.30 hours. Periods lasted 5 weeks and measurements were made in the last 15 d. The higher amount of concentrates increased total D M intake but reduced silage D M intake and the fractional rate of degradation of silage-fibre DM. Later cutting date of silage had no effect on D M intake or the fractional rate of degradation of silage-fibre DM but reduced potential degradability of silage fibre. Dilution rate of CoEDTA in rumen fluid was greater during the day (eating period) than during the night (resting period). Dilution rates measured at the duodenum were lower than those measured in the rumen, but neither was affected by diet. Silage-particle passage rates were measured by use of ytterbium-labelled silage fibre (Yb-fibre) and chromium-mordanted faecal particles (Cr-faeces) and samples were taken at the duodenum and in the faeces. Values for slower rate constant (k,) and transit time were higher and for faster rate constant (k,) were lower for Yb-fibre than for Cr-faeces, but differences in total mean retention time were inconsistent. Values for k , for both markers and k, for Yb-fibre only were similar at both sampling sites, but values for k, for Cr-faeces were lower in the faeces. No diet effects were established with Yb-fibre but, with Cr-faeces, k , was reduced by more concentrates and EC-silage. Daily mean weights of wet digesta, liquid, neutral-detergent fibre (NDF) and indigestible NDF in the rumen were greater with LC-silage but were unaffected by the amount of concentrates whereas weight of rumen D M was increased by the amount of concentrates only. Maximum rumen fill occurred at 18.00 hours with all diets. Particle-size distribution of rumen contents did not vary markedly during the day. Mean particle size was generally greater with LC-silage than EC-silage. Very small particles, passing through the 0.3 mm screen, constituted about half the rumen DM. It is concluded that rumen fill could have limited intake of LC-silage but not EC-silage. The reduced silage intake with greater concentrate intake was associated with a reduction in fibre degradation rate and an increase in rumen D M fill but no other consistent effects on weight or kinetics of rumen fractions were established. Digesta kinetics: Rumen fill : Voluntary intake Despite the increasing importance of grass silage in the diet of dairy cows in the UK, little is known about the factors limiting its intake (Gill et al. 1988); date of cutting of forage and fermentation during ensiling undoubtedly contribute. Increasing the amount of concentrates increases total feed intake but reduces silage intake, possibly by reducing rate of

Purpose: IL-13, RANTES (Regulated on Activation, Normal T cells Expressed and Secreted), and cysteinyl leukotrienes are asthma and atopy mediators. Two RANTES Ϫ403(G to A) and Ϫ28(C to G), an Ϫ1055 IL-13(C to T), and a Ϫ444(A to C) leukotriene C4 synthase (LTC4S) single nucleotide polymorphisms (SNPs) have been shown in Caucasians and Asians as asthma and atopy risk factors. We studied these SNPs in African Americans with asthma and/or atopy. Methods: We studied 61 patients with asthma and/or atopy and 129 to 157 newborn controls for the Ϫ403 RANTES, Ϫ28 RANTES, and Ϫ1055 IL-13 SNPs, as well as 47 patients and 60 newborn controls for the Ϫ444 LTC4S SNP. Results: The two groups did not significantly differ at the genotypes of the Ϫ403 and Ϫ28 RANTES SNP. On the other hand, the mutant TT genotype for the Ϫ1055 IL-13 SNP was detected in 19.7% of patients versus 12.7% in controls (P Ͻ 0.04, OR 2.9, 95% CI 1.0 -8.0), and the mutant T allele in 58.3% versus 36.6% in controls (P Ͻ 0.02, OR 2.4, 95% CI 1.1-5.2). In a similar fashion, for the Ϫ444 LTC4S SNP, the mutant AC genotype was detected in 19.1% versus 10.0% in controls (P Ͼ 0.28); mutant C allele had an OR of 2.1 (95% CI 0.7-6.3). Conclusion: African American asthmatics/atopics had higher frequency of the TT mutant gene for the Ϫ1055 IL-13 SNP and of its mutant T allele. Regarding the Ϫ444 LTC4S SNP, there was a definite difference, although not statistically significant, with an OR of 2.1 for the mutant AC genotype in patients. If these findings become reproduced by larger studies, it may suggest that IL-13 and LTC4S SNPs can be used as predictive markers for asthma/atopy in African Americans. Genet Med 2005:7(6):406 -410.

Seventy-six first-calf cows (heifers), 32 second-calf cows and 39 adult cows participated in a trial in which three diets composed of 60:40, 75:25, 90:10 proportions of compound to hay (hay dry-matter digestibility 0-6) were given for the first 36 weeks of lactation in amounts to provide daily an estimated 125, 156 MJ and ad libitum digestible energy (DE) for heifers, and 156, 187 MJ and ad libitum DE for the other parities. The ad libitum intakes were 150 and 200 MJ DE daily for heifers and for older cows respectively.Greater compound content of the diet and larger daily allowance of DE were associated with increased occurrence of mastitis and lameness but not digestive upsets. Dry-matter (D.M.) digestibility was increased with a greater proportion of compound in the diet but was not affected by the amount consumed or stage of lactation.Milk yield and live-weight change were increased linearly and additively by a greater intake of digestible dry matter and by a greater proportion of compound in the diet, throughout the lactation save for no effect of diet composition on live-weight change in early lactation. On equal feed intakes older cows gave more milk and lost more live weight than heifers in early lactation but not thereafter; responses to additional feed were equal for all parities studied.Milk fat concentration was reduced both by increased allowance and by the high compound diet. Milk solids-not-fat (SNF) concentration was not affected by the treatments. Yield of milk fat was not affected by amount eaten and was reduced by the 90:10 diet. Yields of SNF and milk energy were increased by amount eaten and by increased compound in the diet.Thirty-two primiparous cows continued on their experimental treatments without interruption to the end of the second lactation. In the second lactation the effects on yields of milk, milk energy, and SNF were magnified indicating a cumulative effect from lactation to lactation. Little cumulative effect was observed on either milk fat yield, or concentrations of fat and SNF in milk. More generous feeding was associated with reduced milk output/unit D.M. consumed in the first but not the second lactation. More generous feeding improved live-weight change less in the second than in the first lactation. No cumulative effects over two lactations were observed consequent upon variation in diet composition. INTRODUCTIONt a^e ' s u s u a^y achieved by increments of compound feeds/day, which simultaneously alters the diet Financial and physical constraints frequently composition); secondly the influence of parity of limit the size and scope of nutritional research on cow on performance; and thirdly the significance dairy cows, in the present context with regard to of the full lactation rather than a portion thereof input-output relationships, specifically plane of as the production period studied. Additionally, the nutrition. In consequence a large number of key rationing of cows according to individual current questionsremainunanswered.Amongstthesemaybe performance is being challe...