Feed management practices to reduce manure phosphorus excretion in dairy cattle

Phosphorus (P) is an essential mineral that needs to be supplied in sufficient quantities for maintenance and growth and milk production in dairy cattle. However, over 60% of the P consumed can be excreted in faeces with a potential to cause environmental pollution. Concern over higher levels of P in intensively managed livestock systems has led to legislation such as the Water Framework Directive in the European Union. In this manuscript, several methods of reducing P pollution are discussed. A major source of environmental P pollution has been overfeeding P mainly due to addition of ‘safety margin’ over the animal’s requirement and concerns related to fertility. Matching the animal’s requirement and feeding in groups so that animals at the same physiological status are fed according to their requirement has a potential to reduce P excretion significantly. P can also be reduced by matching available P with the metabolizable energy content of the diet because more P can be incorporated into milk when P is utilized by rumen microbes, which are limited by energy. Plants contain phytate bound P that need to be broken up before they can be absorbed by the animal. Although ruminants can digest phytate, use of phytase enzyme could help either directly by acting on phytate P or improvement of feed digestibility. Pasture management can lead to improved nutrient cycling, particularly if the soil is deficient in P. However, overfertilizing pasture could result is higher runoff of dissolved reactive P. Management practices that leave adequate forage residue on the surface such as rotational grazing will improve infiltration and decrease runoff, reducing nutrient losses

Effects of diet and manure storage method on carbon and nitrogen dynamics during storage and plant nitrogen uptake

Altering dairy cattle diets to reduce both enteric methane (CH4) production and nitrogen (N) excretion are valuable tools for mitigating the environmental impact of dairy production. We examined the impact of altering diets on changes in physicochemical properties of manure during storage, short term plant N availability, and overall system N use efficiency. Manure collected from cattle fed diets with differing forage and crude protein (CP) content were stored via three methods (slurry, static pile, turned pile) for 29 weeks and sampled at week 0, 1, 2, 3, 4, 9, 14, 19, 24, and 29. Mass losses of total carbon (C) ranged from 28 to 50% and followed the trend static pile > slurry > turned pile (P < 0.01). Total N losses ranged from 20 to 47% with the slurry and static pile treatments having larger (but similar) losses than the turned pile treatment (P < 0.01). The soil 2-week plant available N was similar in the static pile and turned pile treatments and were 67% less than the slurry treatment. The short-term plant N use efficiency was similar for both the static pile and slurry treatments (22-24%), which were greater than that of the turned pile treatment (16%). Overall estimated system N use efficiencies were 5% greater for lower CP diets compared to high CP diets. While rapidly drying manure may conserve C and N, there may be a tradeoff with plant N utilization which could affect overall system efficiencies

Effect of dietary crude protein and forage contents on enteric methane emissions and nitrogen excretion from dairy cows simultaneously

The study aimed to examine, simultaneously, the effects of changing dietary forage and crude protein (CP) contents on methane (CH4) emissions and nitrogen (N) excretion from lactating dairy cows. Twelve post-peak lactating Holstein cows were randomly assigned to 4 treatments from a 2×2 factorial arrangement of two dietary forage levels [37.4% (LF) vs. 53.3% (HF) of DM] and two dietary CP levels [15.2% (LP) vs. 18.5% (HP) of DM] in a 4×4 Latin square design with four 18 d periods. Alfalfa hay was the sole source of dietary forage. Cows were fed and milked twice daily. During the first 14 d, cows were housed in a free-stall barn, where enteric CH4 emissions were measured using the GreenFeed system from d 8 to 14 in each period. Cows were then moved to metabolic cages, where total feces and urine output (kg/cow/d) were measured using total collection approach for 3 days. No dietary forage by CP interactions were detected for DMI, milk production, enteric CH4 emissions, or N excretions. Dry matter intake, milk production, and milk composition yield were increased by LF diet (P < 0.01). No difference was found between cows fed HP or LP diets, however, milk fat content increased in cows fed HP (P < 0.05). Enteric CH4 emissions, and CH4 per unit of DMI, ECM, total digested OM and NDF were not affected by dietary CP, but decreased by LF compared to HF (P < 0.01). Milk true protein N was not affected by dietary CP content but was higher for LF compared to HF. Greater dietary N was partitioned to true milk protein in cows fed LF compared to HF diet (P < 0.01). Urinary N excretion was greater in cows fed HP (P < 0.01), and lowest in cows fed LF diet (P < 0.01). Neither dietary CP nor forage content affected fecal N. Total N excretion (urinary plus fecal) did not differ between HP and LP, but tended to be lower in cows fed LF compared to HF diet (P = 0.09). Both milk urea N (P < 0.01) and blood urea N (P < 0.01) declined with decreasing dietary CP or forage contents. Based on purine derivative analysis, microbial protein synthesis in the rumen tended to be lower for high forage and low protein treatments (P < 0.09). Increasing dietary forage contents resulted in greater CH4 emission (g/kg of ECM) and manure N excretion (g/kg of ECM) intensities of lactating dairy cows. Cows receiving reduced CP diets had low manure N outputs and improved milk true protein production efficiencies, regardless of dietary forage content

Methane emissions from dairy lagoons in western U.S.

Methane (CH4) generation from dairy liquid storage systems is a major source of agricultural greenhouse gas emissions. However, there has been little on-farm research conducted to estimate these emissions and determine the factors that may affect these emissions. Six lagoons in south-central Idaho were monitored for one year, with CH4 emissions estimated by inverse dispersion modelling. Lagoon characteristics thought to contribute to CH4 emissions were also monitored over this time period. Average emissions from the lagoons ranged from 30 to 126 kg/ha/d or 22 to 517 kg/d. While there was a general trend for greater emissions during the summer, when temperatures were greater, events such as pumping, rainfall, freeze/thaw of lagoon surfaces, and wind events significantly increased CH4 emissions irrespective of temperature. Lagoon physicochemical characteristics such as total solids, chemical oxygen demand, and volatile solids were highly correlated with emission. Methane prediction models were developed using volatile solids, wind speed, air temperature and pH as independent variables. The USEPA methodology for estimating CH4 emissions from manure storage was used for comparison of on-farm CH4 emissions from one of the lagoon systems. The USEPA method underestimated CH4 emissions by 48%. An alternative methodology, using volatile solids degradation factor, provided a more accurate estimate of annual emissions from the lagoon system and may hold promise for applicability across a range of dairy lagoon systems in the U.S

Ammonia emissions from dairy lagoons in the western U.S.

Ammonia (NH3) emissions from dairy liquid storage systems can be a source of reactive nitrogen (N) released to the environment with a potential to adversely affect sensitive ecosystems and human health. However, there has been little on-farm research conducted to estimate these emissions and determine the factors that may affect these emissions. Six lagoons in south-central Idaho were monitored for one year, with NH3 emissions estimated by inverse dispersion modeling. Lagoon characteristics thought to contribute to NH3 emissions were also monitored over this time period. Average daily emissions from the lagoons ranged from 5.7 to 45 kg NH3 /ha or 5.7 to 96 kg NH3. There was a general trend for greater emissions during the summer, when temperatures were greater, in addition high wind events and agitation of the lagoons created temporary increases in NH3 emissions irrespective of temperature. Lagoon physicochemical characteristics such as total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN) were highly correlated with emission. Ammonia emission prediction models were developed using TKN, TAN, wind speed, air temperature and pH as independent variables. An on farm N balance suggests that lagoon NH3-N losses represented 9% of total N lost from the facility, 65% of the total lagoon N and 5% of dairy herd N intake. A process based model estimated similar values for N excretion and NH3-N loss from the lagoon. On-farm work is necessary to better refine both process based models and emission factor estimates in order to more accurately account for NH3 emissions from lagoons on dairies in the western US

Rumen microbial degradation of bromoform from red seaweed (Asparagopsis taxiformis) and the impact on rumen fermentation and methanogenic archaea

Background The red macroalgae Asparagopsis is an effective methanogenesis inhibitor due to the presence of halogenated methane (CH4) analogues, primarily bromoform (CHBr3). This study aimed to investigate the degradation process of CHBr3 from A. taxiformis in the rumen and whether this process is diet-dependent. An in vitro batch culture system was used according to a 2 × 2 factorial design, assessing two A. taxiformis inclusion rates [0 (CTL) and 2% DM diet (AT)] and two diets [high-concentrate (HC) and high-forage diet (HF)]. Incubations lasted for 72 h and samples of headspace and fermentation liquid were taken at 0, 0.5, 1, 3, 6, 8, 12, 16, 24, 48 and 72 h to assess the pattern of degradation of CHBr3 into dibromomethane (CH2Br2) and fermentation parameters. Additionally, an in vitro experiment with pure cultures of seven methanogens strains (Methanobrevibacter smithii, Methanobrevibacter ruminantium, Methanosphaera stadtmanae, Methanosarcina barkeri, Methanobrevibacter millerae, Methanothermobacter wolfei and Methanobacterium mobile) was conducted to test the effects of increasing concentrations of CHBr3 (0.4, 2, 10 and 50 µmol/L). Results The addition of AT significantly decreased CH4 production (P = 0.002) and the acetate:propionate ratio (P = 0.003) during a 72-h incubation. The concentrations of CHBr3 showed a rapid decrease with nearly 90% degraded within the first 3 h of incubation. On the contrary, CH2Br2 concentration quickly increased during the first 6 h and then gradually decreased towards the end of the incubation. Neither CHBr3 degradation nor CH2Br2 synthesis were affected by the type of diet used as substrate, suggesting that the fermentation rate is not a driving factor involved in CHBr3 degradation. The in vitro culture of methanogens showed a dose-response effect of CHBr3 by inhibiting the growth of M. smithii, M. ruminantium, M. stadtmanae, M. barkeri, M. millerae, M. wolfei, and M. mobile. Conclusions The present work demonstrated that CHBr3 from A. taxiformis is quickly degraded to CH2Br2 in the rumen and that the fermentation rate promoted by different diets is not a driving factor involved in CHBr3 degradation

Impacts of dietary forage and crude protein levels on the shedding of Escherichia coli O157:H7 and Listeria in dairy cattle feces

Shedding of Escherichia coli O157:H7 and Listeria monocytogenes in ruminant manure is well reported. However, the influence of dietary manipulation on the shedding of the pathogens is not well understood. This study was conducted to improve the understanding of the relationship between dietary feed composition and pathogen shedding in dairy feces, particularly E. coli O157:H7 and L. monocytogenes. Twelve cows were randomly assigned to a 2 × 2 factorial arrangement of 2 dietary forage levels: low forage (37.4% of dry matter [DM]) vs. high forage (HF, 53.3% of DM) and two dietary crude protein (CP) levels: low protein (LP, 15.2% of DM) vs. high protein (HP, 18.5% of DM) in a 4 × 4 replicated Latin square design with four periods each including 15 d adaptation and 3 d sample collection. In CP treatments, significantly low concentrations of L. monocytogenes were observed from cows fed the HP (0.9-1.6 log10 cfu/g) compared to the LP diet (1.3–2.1 log10 cfu/g). Significant interaction effect was observed between dietary forage and crude protein on the presence of E. coli O157:H7 (P < 0.05) but not on L. monocytogenes. On average, the highest E. coli O157:H7 concentration (6.5 log10 cfu/g of feces) was observed from the HF and HP diet and the lowest concentration was 6.2 log10cfu/g from the HF and LP diet. The average L. monocytogenes shedding was within the range of 1.8 to 2.4 log 10cfu/g among the treatments. The study showed that diet has an influence on the shedding of pathogenic bacteria in dairy excreta