高寒灌丛土壤温室气体释放对添加不同形态氮素的响应

为探索不同形态氮素输入对青藏高原高寒灌丛土壤CO₂、N₂O和CH₄排放的影响,采集青藏高原东部金露梅高寒灌丛土壤,设置1个对照(CK)和3个添加不同形态氮素的处理(NH₄Cl,NH₄NO₃,KNO₃),在实验室恒温15℃下进行培养,分析了土壤CO₂、N₂O和CH₄的释放量以及土壤NH₄⁺,NO₃^-和可溶性有机碳(DOC)含量。结果表明:1)所有氮素处理抑制了高寒灌丛土壤CO₂的排放,土壤CO₂排放量与DOC浓度呈显著正相关关系;2)所有氮素处理显著增加了土壤N₂O的排放,而且以添加NO₃^--N增加的N₂O最为显著;3)高寒灌丛土壤N₂O的产生过程以反硝化作用为主;4)添加不同形态氮素对高寒灌丛土壤CH₄吸收没有显著影响。5)不同形态氮素施入后,高寒灌丛土壤温室气体全球增温潜能(GWP)顺序:KNO₃>NH₄NO₃>NH₄Cl>CK。     

Comparison of ammonia and greenhouse gas emissions during the fattening of pigs, kept either on fully slatted floor or on deep litter

Five successive batches of fattening pigs were raised, each during a four month period, on a totally concrete slatted floor in one experimental room and on straw based deep litter in another. The rooms were automatically ventilated to maintain a constant ambient temperature. Available floor space was of 0.75 m² per pig kept on the slatted floor and 1.20 m² per pig kept on the deep litter. With this last system, about 46 kg of straw were supplied per pig throughout a fattening period. The slurry pit was emptied and the litter removed after each batch. Once a month, the emissions of ammonia (NH₃), nitrous oxide (N₂O), methane (CH₄), carbon dioxide (CO₂), and water vapour (H₂O) were measured continuously for 6 consecutive days by infra-red photoacoustic detection.The performance of the animals was not significantly different according to the floor type.Gaseous emissions from pigs raised on the slatted floor and on the deep litter were, respectively, 6.2 and 13.1 g per pig per day for NH₃, 0.54 and 1.11 g per pig per day for N₂O, 16.3 and 16.0 g per pig per day for CH₄, 1.74 and 1.97 kg per pig per day for CO₂ and 2.48 and 3.70 kg per pig per day for H₂O. Except for the CH₄ emissions, all the differences were significant (P < 0.001). Thus, pig fattening on deep litter releases nearly 20% more greenhouse gases than on slatted floor, with 2.64 and 2.24 kg of CO₂-equivalents, respectively (P < 0.001). Whatever the floor type, emissions increased from the beginning to the end of the fattening periods by about 5 times for NH₃, 4 times for N₂O, 3 times for CH₄ and 2 times for CO₂ and H₂O. Correlation coefficients between CO₂-emissions and H₂O, NH₃ and CH₄ emissions were, on average for both floor types, 0.82, 0.77 and 0.74, respectively.Although rearing pigs on straw generally has a good brand image for the consumer, this rearing system produces more pollutant gases than keeping pigs on slatted floors.     

Effects of a blend of garlic oil,nitrate and fumarate on in vitro ruminal fermentation and microbial population

Although garlic oil and nitrate can effectively suppress ruminal methane (CH₄) production in vitro, the application of these compounds is associated with suppressed total volatile fatty acid (VFA) concentration. On the other hand, the effectiveness of fumarate as a ruminal CH₄ mitigating agent is variable but its application increases total VFA concentration. We therefore hypothesized that the different characteristics of the compounds can compensate for the shortcomings of the other. The objective of this study was to develop an optimal blend of garlic oil, nitrate and fumarate that can suppress in vitro ruminal CH₄ without affecting total VFA concentration. Three ruminal in vitro fermentation experiments were carried out. The first one, a one factor at a time experiment was employed to investigate the effective concentration of each of the compounds on CH₄ and VFA production by ruminal bacteria. We then applied the fractional factorial design and response surface methodology in the second experiment to determine optimal concentrations of the compounds in the blend. The optimal blending of garlic oil, fumarate and nitrate was determined to be 50 mg/l, 15 mm and 20 mm , respectively. This simulated optimal blend was verified in a 48 h in vitro batch fermentation experiment. The blend achieved the intended goal of suppressing CH₄ whilst maintaining total VFA concentration. The blend and nitrate suppressed archaea populations (p < 0.001) but did not affect the total microbial population (p = 0.945). The observed results could be explained by additive effects of the agents making up the blend. Supplementing a high concentrate diet with the blend can significantly decrease ruminal CH₄ and maintain total VFAin vitro. These findings however, need to be verified in vivo using the optimized ratio of combining the three methane inhibitors as a guide.     

A simple novel measure of passive transfer of maternal immunoglobulin is predictive of preweaning mortality in piglets

Two factors that contribute to preweaning mortality in piglets are the initiation of lactation by sows and their ability to nurse their piglets. The objective of this study was to determine if the quantification of the transfer of immunoglobulins (Igs) from sow to piglet could act as a measure of these sow factors in terms of their influence on preweaning mortality. To measure passive transfer, a simple, rapid Ig immunocrit method was developed. For validation, the smallest piglets from 204 gilts were sacrificed on day 1 after birth and blood was collected.Piglet serum Ig concentrations were measured three ways: (1) by protein A sepharose precipitation, SDS–PAGE, and densitometry of the IgG heavy chain; (2) by precipitation of Ig with (NH₄)₂SO₄ followed by spectrophotometric measurement; and (3) by precipitation of Ig with (NH₄)₂SO₄ and measurement of the ratio of precipitate to sample volume using a hematocrit microcapillary (the Ig immunocrit method). Results from the (NH₄)₂SO₄ methods correlated (r = 0.86) with those obtained using SDS–PAGE. Day 1 weights and immunocrit ratios and preweaning survival data were then collected from every piglet from first (n = 90), and second (n = 145) parity sows. Bodyweight and immunocrit ratios accounted for 4.8% and 16.7% (P < 0.01) of the variation in preweaning mortality, respectively. Litter average immunocrit ratios were not correlated with preweaning mortality. In conclusion, the Ig immunocrit method is a simple, rapid measure of passive transfer from sow to piglet, and is useful in assessing the initiation of colostrum and the nursing ability of sows, and the effect of these events on preweaning piglet mortality.     

Water Absorption Capacity of Flax and Pine Horse Beddings and Gaseous Concentrations in Bedded Stalls

It can be a challenge to find suitable horse bedding materials that provide higher moisture absorption, better animal comfort, greater fertilizer values, and improved indoor environment. Our first objective was to determine the water absorption capacity (WAC) of two bedding materials, flax shive (FS) and pine wood shavings (PWS), commonly used by equine facilities. The second objective was to measure ammonia (NH₃), hydrogen sulfide (H₂S), and greenhouse gas (GHG) concentrations emitted from these bedded stall surfaces. In this study, the WAC of bedding materials were measured at 0.5, 1, 2, 3, 4, 6, 8, 12, and 24 hours in the laboratory. A total of eight horses were used for a 14-day study period. Of these, four horses (group-1) were bedded with FS and the other four (group-2) were bedded with PWS for week-1. In week-2, bedding materials were switched between the two groups. Ammonia and H₂S were measured in situ. For GHG measurement, air samples (methane [CH₄], carbon dioxide [CO₂], and nitrous oxide [N₂O]) were collected 152 mm above the bedded stall surface in Tedlar bags using a vacuum chamber and analyzed for GHG using a gas chromatograph. The WAC of FS was 56% greater than the PWS. There were no significant differences in NH₃, H₂S, CH₄, CO₂, and N₂O concentrations between the two bedding materials (P > .05). Nutrient contents between fresh and soiled bedded samples for each bedding type were different (P < .05). Measured nutrient contents between fresh FS and PWS and bedded FS and PWS bedding materials were similar (P > .05).     

Evaluation of a single‐flow continuous culture fermenter system for determination of ruminal fermentation and enteric methane production

A 4‐unit, single‐flow continuous culture fermenter system was developed to assess in vitro nutrient digestibility, volatile fatty acid (VFA) concentration and daily enteric methane (CH₄) production of ruminant diets. The objective was to develop a closed‐vessel system that maintained protozoal populations and provided accurate predictions of total CH₄ production. A diet of 50% orchardgrass (Dactylis glomerata L.) and 50% alfalfa (Medicago sativa L.) was fed during 4, 10‐day periods (7‐day adaptation and 3‐day collection). Fermenters were fed 82 g of dry matter (DM)/day in four equal feedings. pH and temperature were taken every 2 min, and CH₄ concentration was measured every 10 min. Samples for DM and protozoal counts were taken daily, and daily effluent samples were collected for determination of DM, VFA and NH₃‐N concentrations. There was no effect (p > 0.17) of adaptation versus collection days on vessel and effluent DM, temperature or pH. Initial protozoal counts decreased (p < 0.01), but recovered to initial counts by the collection period. Total VFA, acetate, propionate and isobutyrate concentrations did not differ (p ≥ 0.13) among periods or days of the collection period. There was no difference (p ≥ 0.37) among days or periods in total daily CH₄ production and CH₄ production per g of OM, NDF, digestible OM or digestible NDF fed. Data collected throughout 4 experimental periods demonstrated that the system was able to reach a steady state in fermentation well within the 7‐day adaptation period and even typically variable data (i.e., CH₄ production) were stable within and across periods. While further research is needed to determine the relationship between this system and in vivo data, this continuous culture fermenter system provides a valid comparison of in vitro ruminal fermentation and enteric CH₄ production of ruminant diets that can then be further validated with in vivo studies.     

The effects of dietary nitrate on plasma glucose and insulin sensitivity in sheep

Nitrate (NO₃^¯) is an effective non‐protein nitrogen source for gut microbes and reduces enteric methane (CH₄) production in ruminants. Nitrate is reduced to ammonia by rumen bacteria with nitrite (NO₂^¯) produced as an intermediate. The absorption of NO₂^¯ can cause methaemoglobinaemia in ruminants. Metabolism of NO₃^¯ and NO₂^¯ in blood and animal tissues forms nitric oxide (NO) which has profound physiological effects in ruminants and has been shown to increase glucose uptake and insulin secretion in rodents and humans. We hypothesized that absorption of small quantities of NO₂^¯ resulting from a low‐risk dose of dietary NO₃^¯ will increase insulin sensitivity (S_I) and glucose uptake in sheep. We evaluated the effect of feeding sheep with a diet supplemented with 18 g NO₃^¯/kg DM or urea (Ur) isonitrogenously to NO₃^¯, on insulin and glucose dynamics. A glucose tolerance test using an intravenous bolus of 1 ml/kg LW of 24% (w/v) glucose was conducted in twenty sheep, with 10 sheep receiving 1.8% supplementary NO₃^¯ and 10 receiving supplementary urea isonitrogenously to NO₃^¯. The MINMOD model used plasma glucose and insulin concentrations to estimate basal plasma insulin (I_b) and basal glucose concentration (G_b), insulin sensitivity (S_I), glucose effectiveness (S_G), acute insulin response (AIRg) and disposition index (DI). Nitrate supplementation had no effect on I_b (p > .05). The decrease in blood glucose occurred at the same rate in both dietary treatments (S_G; p = .60), and there was no effect of NO₃^¯ on either G_b, S_I, AIRg or DI. This experiment found that the insulin dynamics assessed using the MINMOD model were not affected by NO₃^¯ administered to fasted sheep at a low dose of 1.8% NO₃^¯ in the diet.     

Dynamics of the ruminal microbial ecosystem,and inhibition of methanogenesis and propiogenesis in response to nitrate feeding to Holstein calves

It is known that nitrate inhibits ruminal methanogenesis, mainly through competition with hydrogenotrophic methanogens for available hydrogen (H₂) and also through toxic effects on the methanogens. However, there is limited knowledge about its effects on the others members of ruminal microbiota and their metabolites. In this study, we investigated the effects of dietary nitrate inclusion on enteric methane (CH₄) emission, temporal changes in ruminal microbiota, and fermentation in Holstein calves. Eighteen animals were maintained in individual pens for 45 d. Animals were randomly allocated to either a control (CTR) or nitrate (NIT, containing 15 g of calcium nitrate/kg dry matter) diets. Methane emissions were estimated using the sulfur hexafluoride (SF₆) tracer method. Ruminal microbiota changes and ruminal fermentation were evaluated at 0, 4, and 8 h post-feeding. In this study, feed dry matter intake (DMI) did not differ between dietary treatments (P > 0.05). Diets containing NIT reduced CH₄ emissions by 27% (g/d) and yield by 21% (g/kg DMI) compared to the CTR (P < 0.05). The pH values and total volatile fatty acids (VFA) concentration did not differ between dietary treatments (P > 0.05) but differed with time, and post-feeding (P < 0.05). Increases in the concentrations of ruminal ammonia nitrogen (NH₃–N) and acetate were observed, whereas propionate decreased at 4 h post-feeding with the NIT diet (P < 0.05). Feeding the NIT diet reduced the populations of total bacteria, total methanogens, Ruminococcus albus and Ruminococcus flavefaciens, and the abundance of Succiniclasticum, Coprococcus, Treponema, Shuttlewortia, Succinivibrio, Sharpea, Pseudobutyrivibrio, and Selenomona (P < 0.05); whereas, the population of total fungi, protozoa, Fibrobacter succinogenes, Atopobium and Erysipelotrichaceae L7A_E11 increased (P < 0.05). In conclusion, feeding nitrate reduces enteric CH₄ emissions and the methanogens population, whereas it decreases the propionate concentration and the abundance of bacteria involved in the succinate and acrylate pathways. Despite the altered fermentation profile and ruminal microbiota, DMI was not influenced by dietary nitrate. These findings suggest that nitrate has a predominantly direct effect on the reduction of methanogenesis and propionate synthesis.     

Determination of GHG and ammonia emissions from stored dairy cattle slurry by using a floating dynamic chamber

We developed a system for measuring emissions from stored slurry by using a floating dynamic chamber. CH₄, CO₂, N₂O and NH₃ emitted from the storage tank of a dairy cattle farm in eastern Hokkaido were measured during summer 2008 (7/16–8/6), fall 2008 (10/2–10/26), spring 2009 (6/2–6/21) and winter 2009 (3/11). Average daily gas emission rates in summer, fall and spring were, respectively, 54.8, 54.2 and 34.3 g/m² for CH₄; 602, 274 and 254 g/m² for CO₂; 55.4, 68.2 and trace mg/m² for N₂O; and 0.55, 0.73 and 0.46 g/m² for NH₃. CH₄, CO₂ and NH₃ emission rates during the brief measurement period in winter were reduced to 1/4, 1/23 and 1/2, respectively, of summer emission rate levels. All gas emissions showed diurnal fluctuation and were greatest during the daytime, when the ambient temperature rose. CH₄, NH₃ and CO₂ emissions increased significantly during the daytime, and the daily emission (in grams) of each gas was positively correlated with maximum daily temperature. According to the combined spring, summer and fall measurements, the CH₄, N₂O and NH₃ annual emission factors were 1.42% (g CH₄/g volatile solids), 0.02% (g N₂O‐N/g total N) and 0.43% (g NH₃‐N/g total N), respectively.     

Influence of protein fermentation and carbohydrate source on in vitro methane production

Incubations were carried out with batch cultures of ruminal micro‐organisms from sheep to analyse the influence of the N source on in vitro CH₄ production. The two substrates were mixtures of maize starch and cellulose in proportions of 75:25 and 25:75 (STAR and CEL substrates, respectively), and the three nitrogen (N) sources were ammonia (NH₄Cl), casein (CA) and isolated soya bean protein (SP). Five isonitrogenous treatments were made by replacing non‐protein‐N (NPN) with CA or SP at levels of 0 (NPN), 50 (CA50 and SP50, respectively) and 100% (CA100 and SP100) of total N. All N treatments were applied at a rate of 35 mg of N/g of substrate organic matter and incubations lasted 16.5 h. With both proteins, N source × substrate interactions (p = 0.065 to 0.002) were detected for CH₄ production and CH₄/total VFA ratio. The increases in CH₄ production observed by replacing the NPN with protein‐N were higher (p < 0.05) for STAR than for CEL substrate, but the opposite was observed for the increases in volatile fatty acid (VFA) production. As a consequence, replacing the NPN by increased levels of CA or SP led to linear increases (p < 0.05) in CH₄/total VFA ratio with STAR, whereas CH₄/total VFA ratio tended (p < 0.10) to be decreased with CEL substrate. Increasing the amount of both proteins decreased linearly (p < 0.05) ammonia‐N concentrations, which may indicate an incorporation of amino acids and peptides into microbial protein without being first deaminated into ammonia‐N. In incubations with the tested N sources as the only substrate, the fermentation of 1 mg of CA or SP produced 1.24 and 0.60 μmol of CH₄ respectively. The results indicate the generation of CH₄ from protein fermentation, and that the response of CH₄ production to protein‐N supply may differ with the basal substrate.     

In vitro gas and methane production in rumen fluid from dairy cows fed grass silages differing in plant maturity,compared to in vivo data

The relationship between in vitro rumen CH₄ production of grass silages, using the gas production technique, and in vivo data obtained with the same cows and rations in respiration chambers was investigated. Silages were made from grass harvested in 2013 on May 6th, May 25th, July 1st and July 8th. The grass silages were used to formulate four different rations which were fed to 24 cows in early and late lactation, resulting in a slightly different dry matter intake (DMI; 16.5 kg/day vs. 15.4 kg/day). The experimental rations consisted of 70% grass silage, 10% maize silage, and 20% concentrates on a dry matter basis. Cows were adapted to the rations for 17 days before rumen fluid was collected via oesophageal tubing, and in vitro gas and CH₄ production were analysed. In vitro total gas and CH₄ production of the (ensiled) grass expressed as ml/g OM decreased with advancing maturity of the grass. The in vitro CH₄ production after 48 hr of incubation expressed in ml/g OM did not correlate with the in vivo CH₄ production expressed in g/kg organic matter intake or g/kg DMI (R² = .00–.18, p ≥ .287). The differences in CH₄ emission per unit of intake observed in vivo were rather small between the different rations, which also contributed to the observed poor relationship. Utilizing stepwise multiple regression improved the correlation only slightly. In vitro gas and CH₄ production varied based on whether donor cows were previously adapted to the respective ration or not, suggesting that careful adaption to the experimental diet should be envisaged in in vitro gas and CH₄ production experiments.     

Mitigation of nitrous oxide (N2O) emission from swine wastewater treatment in an aerobic bioreactor packed with carbon fibers

Mitigation of nitrous oxide (N₂O) emission from swine wastewater treatment was demonstrated in an aerobic bioreactor packed with carbon fibers (CF reactor). The CF reactor had a demonstrated advantage in mitigating N₂O emission and avoiding NOx (NO₃ + NO₂) accumulation. The N₂O emission factor was 0.0003 g N₂O‐N/gTN‐load in the CF bioreactor compared to 0.03 gN₂O‐N/gTN‐load in an activated sludge reactor (AS reactor). N₂O and CH₄ emissions from the CF reactor were 42 g‐CO₂ eq/m³/day, while those from the AS reactor were 725 g‐CO₂ eq/m³/day. The dissolved inorganic nitrogen (DIN) in the CF reactor removed an average of 156 mg/L of the NH₄‐N, and accumulated an average of 14 mg/L of the NO₃‐N. In contrast, the DIN in the AS reactor removed an average 144 mg/L of the NH₄‐N and accumulated an average 183 mg/L of the NO₃‐N. NO₂‐N was almost undetectable in both reactors.     

Effects of Lonicera japonica extract supplementation on in vitro ruminal fermentation,methane emission,and microbial population

Lonicera japonica (LJ; honeysuckle) is used in traditional folk medicine in Korea and is a rich source of ascorbic acid and phenolic components that are reported to have antioxidant and antibiotic properties. We performed an in vitro experiment to assess the effects of LJ extracts (LJE) on ruminal fermentation. Timothy hay (0.3 g dry matter [DM]) was incubated with buffer, ruminal fluid, and 0%, 3%, 5%, 7%, and 9% LJE. Batch culture fermentation was conducted separately for 12, 24, and 48 hr to determine gas production (GP), ruminal fermentation characteristics, and microbial population characteristics. The effects on GP were generally similar to those on DM degradability, with a linear decrease observed at 9% extract at 24 hr. NH₃‐N showed a linear increase with increasing extract concentrations at 12 hr, whereas a decrease was observed at 24 hr. Extract supplementation decreased methane (CH₄) production at 12, 24, and 48 hr. In addition, the abundance of fibrolytic bacteria and ciliate‐associated methanogen was reduced at all concentrations of extracts. These results indicate that LJE have the potential to serve as a ruminal fermentation modifier to suppress CH₄ production with minimal effects on nutrient digestion in the rumen.     

The effect of various anionic salts on ruminal pH and short-chain fatty acids in non-pregnant and non-lactating cows

AIM: To evaluate whether the different anionic salts used in the prevention of parturient paresis have an impact on the ruminal pH and the production of short-chain fatty acids (SCFA) in mature non-pregnant, non-lactating cows.

METHODS: Eleven Holstein-Friesian crossbred cows were administered 2,000 mEq of either one of three chloride salts, viz CaCl₂, MgCl₂, or NH₄Cl; four sulphate salts, viz CaSO₄, CaSO₄ with a grain size of 10 µm, MgSO₄, or (NH₄)₂SO₄; two combinations of anionic salts, viz CaCl₂+MgSO₄, or CaSO₄+NH₄Cl; NaCl; or water, via a ruminal cannula over a 14-day treatment period. The salts and controls were assigned in an 11 × 11 Latin square, and the cows were distributed randomly. Ruminal fluid was collected four times in each treatment period for monitoring the ruminal pH, and four times a day at Days 7 and 14 for monitoring any changes in the concentrations of SCFA.

RESULTS: Feeding anionic salts did not change the ruminal pH, total concentration of SCFA, or distribution pattern of the main SCFA acetic acid, propionic acid, butyric acid or valeric acid (p>0.05).

CONCLUSIONS AND CLINICAL RELEVANCE: Feeding anionic salts has no negative side effect on the ruminal pH and concentrations of SCFA in mature non-pregnant, non-lactating cattle. Impaired function of the rumen due to the feeding of anionic salts is not likely.     

氮对千日红试管苗生长和开花诱导的影响

本文以千日红组培苗为试验材料,研究培养基中氮形态及含量对千日红试管苗生长和开花诱导的影响。结果表明,1)相对于铵态氮(NH₄⁺),硝态氮(No₃^-)作为唯一氮源更有利于千日红试管苗生长和开花诱导,但千日红在NH₄⁺和NO₃^-同时存在的培养基中表现最佳。2)在20 mmol/LNH₄⁺(NO₃^-)和5 mg/L PP₃₃₃存在的条件下,试管苗生长基本随着培养基中NO₃^-(NH₄⁺)含量的增加而增加,并在含40 mmol/L NO₃^-+20 mmol/L NH₄⁺(即MS培养基中氮含量)的培养基中株高达到最大值5.91 cm;而叶片数和开花率则随着培养基中NH₄⁺和NO₃^-含量的增加呈现先增加后下降的趋势,并在20 mmol/L NO₃^-+5 mmol/LNH₄⁺培养基中达到最大值,分别为10.7片/株和38.89%。3)氮含量及形态配比结果表明,千日红试管苗开花率在培养基中氮总量为5 mmol/L、NO₃^-/NH₄⁺为4/1时达到最大值39.95%,而株高和叶片数在氮总量为35 mmol/L,NO₃^-/NH₄⁺为4/1时达到最大值8.52 cm和13.38片/株。千日红试管苗开花率与培养基中NO₃^-/NH₄⁺显著正相关,而与氮总量及株高之间显著负相关。此外,培养基中氮含量及形态配比还显著影响无菌苗根系生长。     

Comparison of two live Bacillus species as feed additives for improving in vitro fermentation of cereal straws

This study was performed in a 2 × 4 factorial arrangement to explore and compare the effects of inclusion of two live Bacillus additives (B. licheniformis and B. subtilis) at four doses (0, 0.25 × 10⁷, 0.50 × 10⁷ and 0.75 × 10⁷ colony‐forming units (cfu)) on in vitro gas production kinetics, fiber degradation, methane production and ruminal fermentation characteristics of maize stover and rice straw by mixed rumen microorganisms in dairy cows. The pH, concentrations of ammonia nitrogen (NH₃‐N) and isovalerate were increased (P < 0.05), while the methane (CH₄) production, ratio of acetate to propionate, and total volatile fatty acids (TVFA) concentration were decreased (P < 0.05) by the supplementation of B. licheniformis compared with that of B. subtilis. Adding B. licheniformis and B. subtilis raised (P < 0.05) or numerically raised the maximum gas production, while decreasing (P < 0.05) or numerically lowering pH and concentrations of most volatile fatty acids. The addition of B. licheniformis increased (P < 0.05) the NH₃‐N concentration but reduced CH₄ production and ratio of acetate to propionate (P < 0.05), while the NH₃‐N concentration was decreased (P < 0.05), and the CH₄ production and ratio of acetate to propionate were increased by that of B. subtilis compared to the control. Results obtained in this research suggest that B. licheniformis would be preferred as a live Bacillus additive in comparison with B. subtilis, and its optimal dose should be 0.25 × 10⁷ cfu/500 mg substrates.     

Recovery threshold of Toxocara canis eggs from soil

The purpose of this study was to evaluate the threshold of Toxocara canis eggs form soil samples through utilisation of a centrifuge-flotation technique (CFT). Aliquots of soil (1 g each) were artificially contaminated with known numbers of T. canis eggs (1, 10, 25, 50, 100, and 200 eggs). The threshold was evaluated based on a CFT using zinc sulphate (Zn₂SO₄) and sodium nitrate (Na₂NO₃) solutions at a specific gravity of 1.20. The number of eggs recovered was directly proportional to the number of eggs employed to seed the soil. Both solutions enabled full recovery of samples containing merely three eggs; only Zn₂SO₄ demonstrated efficiency in soil contaminated with a single egg. A recovery rate of 100% was obtained for all tests with samples containing 10 and 25 eggs for Zn₂SO₄ and Na₂NO₃, respectively_. There was no difference in the mean number of recovered eggs regarding either the efficacy of the solutions or the repetition of evaluations in the same trial (p > 0.05). Therefore, the CFT is efficient for the detection of Toxocara eggs, even in samples containing low egg numbers.     

Grazing behaviour,physical activity and metabolic profile of two Holstein strains in an organic grazing system

The challenge for sustainable organic dairy farming is identification of cows that are well adapted to forage‐based production systems. Therefore, the aim of this study was to compare the grazing behaviour, physical activity and metabolic profile of two different Holstein strains kept in an organic grazing system without concentrate supplementation. Twelve Swiss (H_CH; 566 kg body weight (BW) and 12 New Zealand Holstein‐Friesian (H_NZ; 530 kg BW) cows in mid‐lactation were kept in a rotational grazing system. After an adaptation period, the milk yield, nutrient intake, physical activity and grazing behaviour were recorded for each cow for 7 days. On three consecutive days, blood was sampled at 07:00, 12:00 and 17:00 h from each cow by jugular vein puncture. Data were analysed using linear mixed models. No differences were found in milk yield, but milk fat (3.69 vs. 4.05%, P = 0.05) and milk protein percentage (2.92 vs. 3.20%, P < 0.01) were lower in H_CH than in H_NZ cows. Herbage intake did not differ between strains, but organic matter digestibility was greater (P = 0.01) in H_CH compared to H_NZ cows. The H_CH cows spent less (P = 0.04) time ruminating (439 vs. 469 min/day) and had a lower (P = 0.02) number of ruminating boli when compared to the H_NZ cows. The time spent eating and physical activity did not differ between strains. Concentrations of IGF‐1 and T3 were lower (P ≤ 0.05) in H_CH than H_NZ cows. In conclusion, H_CH cows were not able to increase dry matter intake in order to express their full genetic potential for milk production when kept in an organic grazing system without concentrate supplementation. On the other hand, H_NZ cows seem to compensate for the reduced nutrient availability better than H_CH cows but could not use that advantage for increased production efficiency.     

Effects of illite supplementation on in vitro and in vivo rumen fermentation,microbial population and methane emission of Hanwoo steers fed high concentrate diets

This study was conducted to evaluate the effects of feeding supplemental illite to Hanwoo steers on methane (CH₄) emission and rumen fermentation parameters. An in vitro ruminal fermentation technique was conducted using a commercial concentrate as substrate and illite was added at different concentrations as treatments: 0%, 0.5%, 1.0%, and 2.0% illite. Total volatile fatty acids (VFA) were different (P < 0.05) at 24 h of incubation where the highest total VFA was observed at 1.0% of illite. Conversely, lowest CH₄ production (P < 0.01) was found at 1.0% of illite. In the in vivo experiment, two diets were provided, without illite and with addition of 1% illite. An automated head chamber (GreenFeed) system was used to measure enteric CH₄ production. Cattle received illite supplemented feed increased (P < 0.05) total VFA concentrations in the rumen compared with those fed control. Feeding illite numerically decreased CH₄ production (g/day) and yield (g/kg dry matter intake). Rumen microbial population analysis indicated that the population of total bacteria, protozoa and methanogens were lower (P < 0.05) for illite compared with the control. Accordingly, overall results suggested that feeding a diet supplemented with 1% illite can have positive effects on feed fermentation in the rumen and enteric CH₄ mitigation in beef cattle.     

Influence of Aguamiel (Agave atrovirens) as a Natural Feed Additive on Cecal Fermentation Kinetics of Some Forage Species in Horse Feeding

This study aimed to evaluate the effect of different dose levels of aguamiel (Agave atrovirens) on in vitro cecal gas, methane (CH₄), and carbon dioxide (CO₂) productions of five forage species (Avena sativa [hay]), Moringa oleifera, Caesalpinia coriacea, Salix babylonica, and Eichhornia crassipes using inocula from the horse. The forage samples were incubated with three doses of aguamiel: 0, 34, and 68 μg of aguamiel/g dry matter (DM) of substrate. Cecal inocula were collected from four adult female Criolla horses (3–4 years of age and weighing 300 ± 15.0 kg) grazed on native grasses for about 8 hours without supplementation. Forage type affected (P < .001) cecal asymptotic, rate and lag time of gas, CH₄ and CO₂ productions (mL/g DM), pH and DM degradability. Aguamiel dose had linear and quadratic effects (P < .05) on the asymptotic and rate of CH₄ productions and rate and lag time of CO₂ productions (mL/g DM). Forage type × aguamiel dose interactions were significant (P < .05) for asymptotic, rate and lag time of gas, and CH₄ and CO₂ productions (mL/g DM). Forage species effects were pronounced (P < .05) on CH₄ and CO₂ productions (mL/g incubated and degraded DM) and proportional CH₄ production at all hours of incubation, except for CO₂ production (mL/g incubated DM). Aguamiel dose affected (P < .05) CO₂ production (mL/g incubated DM) and proportional CO₂ production at the incubated hours. Forage type × aguamiel dose interactions were observed (P < .05) for CO₂ production (mL/g incubated DM) and proportional CO₂ production at the incubated hours but had no impact on CH₄ production. It is concluded that addition of aguamiel to five forage species affected fermentation kinetics of gas production resulting in different in vitro cecal gas, CH₄ and CO₂ productions from these substrates.