The objective of this experiment was to investigate the effect of level of dietary concentrate on rumen fermentation, digestibility, and N losses in lactating dairy cows. The experiment was a replicated 3x3 Latin square design with 6 cows and 16-d adaptation periods. Ruminal contents were exchanged between cows at the beginning of each adaptation period. Data for 2 of the diets tested in this experiment are presented here. The diets contained (dry matter basis): 52% (LowC; control) and 72% (HighC) concentrate feeds. Crude protein contents of the diets were 16.5 and 16.4%, respectively. The HighC diet decreased ruminal pH and ammonia concentration and increased propionate concentration compared with LowC. Acetate:propionate ratio was greater for LowC than for HighC. Rumen methane production and microbial protein synthesis were unaffected by diet. Dry matter intake was similar among diets, but milk yield was increased by HighC compared with LowC (36.0 and 33.2 kg/d, respectively). Milk fat percentage and yield and total-tract apparent NDF digestibility were decreased by HighC compared with LowC. More ruminal ammonia N was transferred into milk protein with HighC than with LowC. Urinary N excretion, plasma urea N, and milk urea N concentration were not affected by diet. The ammonia emitting potential of manure was similar between LowC and HighC diets. Increased concentrate proportion in the diet of dairy cows resulted in reduced ruminal ammonia concentration and enhanced ammonia utilization for milk protein synthesis. These effects, however, did not result in reduced urinary N losses and only marginally improved milk N efficiency. Increasing dietary concentrate was not a successful strategy to mitigate enteric methane production and ammonia emissions from manure.

This experiment (replicated 3 x 3 Latin square design) was conducted to investigate the effects of lauric acid (LA) or coconut oil (CO) on ruminal fermentation, nutrient digestibility, ammonia losses from manure, and milk fatty acid (FA) composition in lactating cows. Treatments consisted of intraruminal doses of 240 g of stearic acid/d (SA; control), 240 g of LA/d, or 530 g of CO/d administered once daily, before feeding. Between periods, cows were inoculated with ruminal contents from donor cows and allowed a 7-d recovery period. Treatment did not affect dry matter intake, milk yield, or milk composition. Ruminal pH was slightly increased by CO compared with the other treatments, whereas LA and CO decreased ruminal ammonia concentration compared with SA. Both LA and CO decreased protozoal counts by 80% or more compared with SA. Methane production rate in the rumen was reduced by CO compared with LA and SA, with no differences between LA and SA. Treatments had no effect on total tract apparent dry matter, organic matter, N, and neutral detergent fiber digestibility coefficients or on cumulative (15 d) in vitro ammonia losses from manure. Compared with SA, LA and CO increased milk fat 12:0, cis-9 12:1, and trans-9 12:1 content and decreased 6:0, 8:0, 10:0, cis-9 10:1, 16:0, 18:0, cis 18:1, total 18:2, 18:3 n-3 and total polyunsaturated FA concentrations. Administration of LA and 14:0 (as CO) in the rumen were apparently transferred into milk fat with a mean efficiency of 18 and 15%, respectively. In conclusion, current data confirmed that LA and CO exhibit strong antiprotozoal activity when dosed intraruminally, an effect that is accompanied by decreases in ammonia concentration and, for CO, lowered methane production. Administration of LA and CO in the rumen also altered milk FA composition.

Ammonia is an important air and water pollutant, but the spatial variation in its concentrations presents technical difficulties in accurate determination of ammonia emissions from animal feeding operations. The objectives of this study were to investigate the relationship between ammonia volatilization and delta15N of dairy manure and the feasibility of estimating ammonia losses from a dairy facility using chemical markers. In Exp. 1, the N/P ratio in manure decreased by 30% in 14 d as cumulative ammonia losses increased exponentially. Delta 15N of manure increased throughout the course of the experiment and delta15N of emitted ammonia increased (p<0.001) quadratically from -31 per thousand to -15 per thousand. The relationship between cumulative ammonia losses and delta15N of manure was highly significant (p<0.001; r2=0.76). In Exp. 2, using a mass balance approach, approximately half of the N excreted by dairy cows (Bos taurus) could not be accounted for in 24 h. Using N/P and N/K ratios in fresh and 24-h manure, an estimated 0.55 and 0.34 (respectively) of the N excreted with feces and urine could not be accounted for. This study demonstrated that chemical markers (P, K) can be successfully used to estimate ammonia losses from cattle manure. The relationship between manure delta15N and cumulative ammonia loss may also be useful for estimating ammonia losses. Although promising, the latter approach needs to be further studied and verified in various experimental conditions and in the field.

This experiment investigated the effect of dietary crude protein (CP) and ruminally degraded protein (RDP) levels on rumen fermentation, digestibility, ammonia emission from manure, and performance of lactating dairy cows. The experiment was a replicated 3 x 3 Latin square design with 6 cows. Three diets varying in CP concentration were tested (CP, % of dry matter): 15.4 (high CP, control), 13.4 (medium CP), and 12.9% (low CP). These diets provided metabolizable protein balances of 323, -44, and 40 g/d and RDP balances of 162, -326, and -636 g/d (high, medium, and low, respectively). Both the medium and low CP diets decreased ruminal pH compared with high CP, most likely because of the higher nonfiber carbohydrate concentration in the former diets. Ruminal ammonia pool size (rumen ammonia N was labeled with (15)N) and the concentration of total free amino acids were greater for the high CP diet than for the RDP-deficient diets. Apparent total-tract nutrient digestibilities were not affected by treatment. Both the medium and low CP diets resulted in lower absolute and relative excretion of urinary N compared with the high CP diet, as a proportion of N intake. Excretion of fecal N and milk yield and composition were not affected by diet. Milk N efficiency (milk N / N intake) and the cumulative secretion of ammonia-(15)N in milk protein were greater for the RDP-deficient diets, and milk urea N concentration was greater for the high CP diet. Both medium and low CP diets decreased the irreversible loss of ruminal ammonia N compared with the high CP diet. The rate and cumulative ammonia emissions from manure were lower for the medium and low CP diets compared with the high CP diet. Overall, this study demonstrated that dairy diets with reduced CP and RDP concentrations will produce manure with lower ammonia-emitting potential without affecting cow performance, if metabolizable protein requirements are met.

Z. 2003. Effect of dietary sunflower oil and vitamin E on beef cattle performance, carcass characteristics and meat quality. Can. J. Anim. Sci. 83: 53-66. In the present study, we tested the hypothesis that feeding sunflower oil (SFO) containing about 70% linoleic acid would increase conjugated linoleic acids (CLA) content of beef and that the increased CLA levels would improve meat shelf life. Two feeding trials were conducted to determine the effect of SFO supplementation on beef production, carcass characteristics and meat quality parameters. In addition, the visual aspects of beef quality in retail display as influenced by dietary vitamin E were compared with that of the increased CLA derived from dietary SFO. In exp. 1, 72 finishing steers (465 ± 9 kg) were individually fed one of four dietary treatments: an unsupplemented control finishing diet, the control diet supplemented with 6% SFO, 500 IU head -1 d -1 vitamin E or a combination of 6% SFO and 500 IU head -1 d -1 vitamin E for 95 d. Data from in vitro gas production from the diets indicated that oil inclusion reduced rate and lag time prior to initiation of gas production. Dry matter intake (DMI) declined (P < 0.05) due to dietary treatments without affecting average daily gain or feed conversion efficiency. Meat from steers fed all supplements was less red, more discolored and less acceptable after 2 d storage in a display case. In exp. 2, 40 steers (412.5 ± 11 kg), in individual pens, were used in a second completely randomized design experiment to evaluate the effect of supplementation of steam-rolled barley based finishing diets with 0, (CON) 3 or 6% SFO or 500 IU head -1 d -1 vitamin E on performance, carcass, meat characteristics, and fatty acid composition of beef. No difference (P > 0.05) in final liveweight, DMI, average daily weight gain (ADG) and feed efficiency (FE) of steers fed diets was found. Carcass grade fat was higher (P < 0.05) in steers fed the 6% SFO diet than the other diets. Retail acceptance score of meat obtained from steers fed 6% SFO was higher than from steers fed other diets (P < 0.05). In both experiments, the fatty acid composition of the meat indicated that C 16:0 and C 16:1 fatty acid levels were lower (P < 0.05) while C 18:2 was higher (P < 0.05) in longissimus muscle of steers fed 6% SFO than the other diets. CLA content in fat from longissimus muscle was higher in steers fed the 6% SFO than control diets (3.5 vs. 3.0 mg g -1 in exp. 1 and 3.5 vs. 2.0 mg g -1 in exp. 2; P < 0.05). Hence supplementing feedlot diets with SFO for up to 108 d can increase CLA composition of beef. Positional distribution of fatty acids indicated that the majority of the CLA was in the sn-2 position of the triacyglycerol molecule.Key words: Beef cattle, conjugated linoleic acid, fatty acids, meat quality, sunflower oil, vitamin E Mir, P. S., McAllister, T. A., Zaman, S., Morgan Jones, S. D., He, M. L., Aalhus, J. L., Jeremiah, L. E., Goonewardene, L. A., Weselake, R. J. et Mir, Z. 2003. Incidence de l'huile de tournesol et de la vitamine ...

BACKGROUND: The objective of this study was to investigate the effect of polysaccharide-degrading enzymes (a cellulase and a xylanase) alone or in a combination with a bacterial inoculant on fermentation parameters and in vitro degradability and gas production of low-dry matter (DM) alfalfa silage. First cut alfalfa (Medicago sativa L.), harvested at about 5% bloom stage [260 g kg −1 dry matter (DM)] was ensiled in laboratory-scale silos without preservatives or preserved with formic acid, a cellulase (Cell), a xylanase, a cellulose/xylanase enzyme combination (Cell/Xyl), a lactic acid bacteria-based inoculant (Inoc), and a mix of Inoc and Cell (Inoc/Cell). Triplicate silos were opened on days 1, 3, 7, 15 and 60.

The effect of type of grain (corn vs. barley) and amylopectin content of barley grain (normal vs. waxy) on ruminal fermentation, digestibility, and utilization of ruminal ammonia nitrogen for milk protein synthesis was studied in a replicated 3 x 3 Latin square design trial with 6 lactating dairy cows. The experimental treatments were (proportion of dietary dry matter): CORN, 40% corn grain, NBAR, 30% normal Baronesse barley:10% corn grain, and WBAR, 30% high-amylopectin (waxy) Baronesse barley:10% corn grain. All grains were steam-rolled and fed as part of a total mixed ration. The NBAR and WBAR diets resulted in increased ruminal ammonia concentrations compared with CORN (8.2, 7.4, and 5.6 mM, respectively), but other ruminal fermentation parameters were not affected. Ruminal digestibility of dietary nutrients and microbial protein synthesis in the rumen were also not affected by diet. Corn grain had greater in situ effective ruminal dry matter degradability (62.8%) than the barley grains (58.2 and 50.7%, respectively), and degradability of the normal barley starch was greater than that of the waxy barley (69.3 and 58.9%, respectively). A greater percentage of relative starch crystallinity was observed for the waxy compared with the normal barley grain. Total tract apparent digestibility of dry matter and organic matter were decreased by WBAR compared with CORN and NBAR. Total tract starch digestibility was greater and milk urea nitrogen content was lower for CORN compared with the 2 barley diets. In this study, the extent of processing of the grain component of the diet was most likely the factor that determined the diet responses. Minimal processing of barley grain (processing indexes of 79.2 to 87.9%) reduced its total tract digestibility of starch compared with steam-rolled corn (processing index of 58.8%). As a result of the increased ammonia concentration and reduced degradability of barley dry matter in the rumen, the utilization of ruminal ammonia nitrogen for microbial protein synthesis was decreased with the barley diets compared with the corn-based diet. In this study, waxy Baronesse barley was less degradable in the rumen and the total digestive tract than its normal counterpart. The most likely reasons for these effects were the differences in starch characteristics and chemical composition, and perhaps the different response to processing between the 2 barleys.

No abstract