The objective of this study was to evaluate recovery site of mobile nylon bags for measuring ileal digestibility of ruminally undegraded starch in dairy cows. Eight feed samples of untreated and ...treated concentrates were examined. Three lactating cows equipped with rumen fistula and duodenal and ileal cannulas were used in the experiment. The mobile nylon bags containing intact feeds or residues after a 12-h ruminal incubation were pretreated using a 2-step procedure to simulate abomasal digestion before insertion through the duodenal cannula. To assess the effect of hindgut fermentation on starch digestibility, approximately half of the bags were collected from the ileum and half from the feces. The results indicate that feed samples should be preincubated in rumen before insertion into duodenum, and that samples with relatively high fractions of rumen-undigestible starch should be collected from the ileum instead of from feces.
Effects of plant-bound condensed tannin (CT)-containing sainfoin vs. CT-free alfalfa (or low-CT alfalfa-sainfoin mixture), plant stage of maturity, and their interaction on enteric methane (CH4) ...emissions, diet digestibility, and N excretion were studied, using 8 ruminally cannulated beef heifers in 2 sequential short-term experiments (Exp. 1 and 2). In Exp. 1, first growth legumes were harvested daily and offered fresh to heifers. Heifers were assigned to 100% sainfoin or 80% alfalfa:20% sainfoin (as-fed basis). Responses were measured at early (late vegetative to early bud; stage 2 to 3) and late (early flower; stage 5) stage of maturity. In Exp. 2, the same legumes were harvested from second growth (late bud; stage 4) and offered to heifers as hay; 100% sainfoin or 100% alfalfa. In both experiments, heifers were fed once daily at 1× maintenance. When fed as fresh forage (Exp. 1), sainfoin, compared with the alfalfa-sainfoin blend, had greater digestibility of OM (74.7 vs. 70.9%; P = 0.02), yet tended to have lower CP digestibility (73.2 vs. 77.1%; P = 0.059). There was no difference between fresh legumes for CH4 emissions 25.9 g/kg DMI ± 4.02 SE; 8.5% of gross energy intake (GEI) ± 1.26 SE; or 36.8 g/kg digested OM ± 1.75 SE. The fresh legumes were more digestible at early, rather than at late, maturity and, consequently, enteric CH4 (27.4 vs. 24.4 g/kg DMI; P < 0.004; 8.9 vs. 8.1% GEI; P < 0.008) was greater at early, rather than at later, growth. When fed as hay (Exp. 2), sainfoin, compared with alfalfa, had greater digestibility of OM (60.5 vs. 50.3%; P = 0.007), lower digestibility of CP (64.2 vs. 68.8%; P = 0.004), yet there was no difference between the legume hays for CH4 emissions (22.4 g/kg DMI ± 1.29 SD and 7.1% GEI ± 0.40 SD). However, on the basis of OM digested, CH4 emissions were lower for sainfoin than alfalfa hay (44.3 vs. 59.0 g/kg; P = 0.008). Percentage of total N excretion in urine was less for sainfoin compared with alfalfa, both for fresh legumes in Exp. 1 (74 vs. 78%; P = 0.017) or hay in Exp. 2 (64 vs. 72%; P < 0.001), and increasing maturity lowered urinary N excretion. In conclusion, feeding CT-containing sainfoin partially shifted N excretion from urine to feces, but it had little impact on enteric CH4 emissions from beef cattle fed at maintenance as compared with feeding either 80% alfalfa:20% sainfoin (fresh forages) or 100% alfalfa (hay). Feeding fresh legumes harvested between the late vegetative to early bud stage, compared with harvested at the early flower stage, increased N excreted in urine as well as enteric CH4 emissions from beef cattle fed at maintenance.
Abstract
The objective of this study was to determine the impact of ruminal pH on methane (CH4) emission from beef cattle. Ruminal pH and CH4 data were generated in 2 experiments using 16 beef ...heifers offered high-forage (55% barley silage) or high-grain (92% concentrate; DM basis) diets. Both experiments were designed as a replicated 4 × 4 Latin square with 4 periods and 4 dietary treatments. Methane was measured over 4 consecutive days using open-circuit respiratory chambers with each chamber housing 2 heifers. The ruminal pH of individual heifers was measured using indwelling pH loggers. The mean ruminal pH and CH4 emission (g/h) of 2 heifers in every chamber were summarized in 30-min blocks. Even though rumen methanogens have been described to be inhibited by a pH < 6.0 in vitro, in vivo CH4-production rates (g/h) did not decrease when ruminal pH declined to threshold levels for subacute (5.2 ≤ pH < 5.5) or acute ruminal acidosis (pH < 5.2; P > 0.05). Daily mean CH4 emission (g/d) and ruminal pH were only mildly correlated (r2 = 0.27; P < 0.05), suggesting that additional factors, such as increased propionate formation or passage rate, account for the lower CH4 emissions from cattle fed high-grain as compared to high-forage diets. Lowering ruminal pH alone is, therefore, not an effective CH4-mitigation strategy. Mechanisms permitting methanogens to survive episodes of low-ruminal pH might include changes in community structure toward more pH-tolerant strains or sequestration into microenvironments within biofilms or protozoa where methanogens are protected from low pH.
Objectives We hypothesized an impaired renal endocrine and natriuretic response to volume expansion (VE) in humans with pre-clinical systolic dysfunction (PSD) and pre-clinical diastolic dysfunction ...(PDD). We further hypothesized that exogenous B-type natriuretic peptide (BNP) could rescue an impaired natriuretic response in PSD and PDD. Background Recent reports suggest that in early systolic heart failure (HF), there is an impaired natriuretic response to acute VE. Methods PSD was defined as left ventricular ejection fraction <40% without HF symptoms. PDD was defined as ejection fraction >50%, moderate to severe diastolic dysfunction by Doppler criteria, and no HF symptoms. A double-blinded, placebo-controlled, crossover study was employed to determine the renal response to VE (0.25 ml/kg/min of normal saline for 60 min) in the presence and absence of exogenous BNP. Twenty healthy control subjects, 20 PSD subjects, and 18 PDD subjects participated. Results In healthy control subjects, urinary cyclic guanosine monophosphate (cGMP) and natriuresis increased after VE. In contrast, among PSD and PDD subjects, there was a paradoxical decrease in urinary cGMP and attenuated natriuresis. Pre-treatment with subcutaneous BNP resulted in similar increases in both urinary cGMP and natriuresis among healthy normal, PSD, and PDD subjects. Conclusions In PSD and PDD, there is impaired renal cGMP activation, which contributes to impaired natriuresis in response to VE. Impaired activation of urinary cGMP and reduced natriuresis may contribute to volume overload and the progression of HF among PSD and PDD subjects. Importantly, the impaired renal excretory response to VE is rescued by exogenous BNP in PSD and PDD.
Sixteen strains of propionibacteria were inoculated into in vitro ruminal incubations to evaluate their potential to reduce methane (CH₄) production from concentrate and forage diets. ...Propionibacterium freudenreichii T114, Propionibacterium thoenii T159, and Propionibacterium thoenii ATCC 4874 lowered (p < 0.05) CH₄ production from both substrates compared to control. Compared to control, Propionibacterium jensenii T1, Propionibacterium freudenreichii T31, and Propionibacterium freudenreichii T54 lowered (p < 0.05) CH₄ production only with corn. Propionibacterium propionicus T83 caused higher (p < 0.05) propionate percentage and lower (p < 0.05) acetate:propionate than the control with corn; however, this did not result in a decline in CH₄ production. Results demonstrate that some strains of propionibacteria have the potential to lower CH₄ production from mixed ruminal cultures and that this reduction is not always associated with an increase in propionate production.
The main objective of this study was to investigate the effect of excess cobalt (Co) on gene expression of stearoyl‐CoA desaturase (SCD), fatty acid synthase (FASN), diacylglycerol acyltransferase 1 ...(DGAT1) and diacylglycerol acyltransferase 2 (DGAT2) of lactating dairy cows in relation to milk fatty acid profile. Seven multiparous cows of the Norwegian Red cattle breed (NRF) had their basal diet supplemented with 1.4 g Co as a 24 g/l solution of Co‐acetate per os twice daily for 7 days followed by a 9‐day depuration period. Udder biopsies were performed prior to the treatment period, after 1 week of treatment and immediately after the depuration period. Excess Co reduced the proportion of all cis‐9 monounsaturated fatty acids and increased the proportion of 18:0 in milk. However, gene expression levels of SCD, DGAT1, DGAT2 and FASN were not significantly altered. Our results indicate that the effect of Co on milk fatty acid profile is mediated at the post‐transcriptional level by reduced activity of SCD in the mammary gland. Potential mechanisms explaining how Co might reduce stearoyl‐CoA desaturation are discussed.
The objective of this study was to determine whether intravenous infusion of Co affects levels of fatty acid desaturation products in bovine milk. Six cows were assigned to two replicated 3 x 3 Latin ...squares with 14-day periods. Treatment occurred on days 1 to 5 and depuration occurred on days 6-14. Two treatments were tested, the first consisting of per os supplementation of 3.5 g Co daily in the form of Co acetate and the second consisting of intravenous injection of 175 mg Co daily in the form of Co acetate diluted in saline solution. The third treatment was a control. Both Co treatments decreased cis-9 18:1 levels from approximately 18 to 14 g/100 g fatty acids, and increased 18:0 levels from 11 to 17 g/100 g fatty acids in milk fat (p < 0.001). The proportions of cis-9 10:1, cis-9 12:1, cis-9 14:1, cis-9 16:1 and cis-9 17:1 decreased (p < 0.001), whereas 17:0 and trans-11 18:1 increased (p < 0.001). In blood plasma, levels of cis (6,9,12) 18:3 (p < 0.001) and cis (8,11,14,17) 20:4 (p = 0.008) decreased after both the Co treatments. It is concluded that intravenous supply of Co reduces levels of fatty acid desaturation products in both bovine milk and blood.
The objectives of this study were to examine the impact of corn- or wheat-based dried distillers grains with solubles (CDDGS or WDDGS) on enteric methane (CH4) emissions from growing beef cattle and ...determine if the oil in CDDGS was responsible for any response observed. Effects of CDDGS or WDDGS on total N excretion and partitioning between urine and fecal N were also examined in this replicated 4 x 4 Latin square using 16 ruminally cannulated crossbreed heifers (388.5 ± 34.9 kg of initial BW). The control diet contained (DM basis) 55% whole crop barley silage, 35% barley grain, 5% canola meal, and 5% vitamin and mineral supplement. Three dried distillers grains with solubles (DDGS) diets were formulated by replacing barley grain and canola meal (40% of dietary DM) with CDDGS, WDDGS, or WDDGS plus corn oil (WDDGS+oil). For WDDGS+oil, corn oil was added to WDDGS (4.11% fat DM basis) to achieve the same fat level as in CDDGS (9.95% fat DM basis). All total mixed diets were fed once daily ad libitum. Total collection of urine and feces was conducted between d 11 and 14. Enteric CH^sub 4^ was measured between d 18 and 21 using 4 environmental chambers (2 animals fed the same diet per chamber). Methane emissions per kilogram of DM intake (DMI) and as percent of GE intake (GEI) among heifers fed WDDGS (23.9 g/kg DMI and 7.3% of GEI) and the control (25.3 g/kg DMI and 7.8% of GEI) were similar (P = 0.21 and P = 0.19) whereas heifers fed CDDGS (21.5 g/kg DMI and 6.6% of GEI) and WDDGS+oil (21.1 g/kg DMI and 6.3% of GEI) produced less (P < 0.05) CH^ sub 4^. Total N excretion (g/d) differed (P < 0.001) among treatments with WDDGS resulting in the greatest total N excretion (303 g/d) followed by WDDGS+oil (259 g/d), CDDGS (206 g/d), and the control diet (170 g/d), respectively. Compared with the control diet, heifers offered WDDGS, CDDGS, and WDDGS+oil excreted less fecal N (P < 0.001) but more (P < 0.001) urinary N. Results suggest that highfat CDDGS or WDDGS+oil can mitigate enteric CH^sub 4^ emissions in growing beef cattle. However, to completely assess the impact of DDGS on greenhouse gas emissions of growing feedlot cattle, the potential contribution of increased N excretion to heightened NH^sub 3^ and nitrous oxide emissions requires consideration. PUBLICATION ABSTRACT
Globally, methane emissions account for 40–45% of greenhouse gas emissions from ruminant livestock, with over 90% of these emissions arising from enteric fermentation. Consequently, enteric CH₄ ...emissions are by far the single most important emission source that can be targeted for mitigation within the ruminant production cycle. This review aims to update nutritional and management abatement strategies for enteric methane emissions. Each ruminant production system is unique, and therefore a holistic, life cycle assessment should be considered when determining the potential value of any abatement strategy. It is important to bear in mind that any abatement strategy will only be adopted if it passes regulatory requirements and if there is an economic incentive for its implementation.
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