Nutritional and physiological responses to dietary phosphorus levels and phytase in pullets and laying hens

The objective of this study was to determine the effects of dietary available phosphorus (P) levels and dietary phytase added into the very low-P diet on the performance, mineral balance, odor emission, and stress responses in growing pullets and laying hens during 13 to 32 wk of age. One hundred sixty-eight pullets (Hy-Line Brown) were randomly assigned into 1 of 4 dietary treatments with 7 replicates of 6 birds each. Experimental diets were formulated to contain 3 graded P levels at 0.25, 0.35, and 0.45% during 13 to 15 wk (phase 1), 0.25, 0.35, and 0.45% during 16 to 18 wk (phase 2), and 0.20, 0.30, and 0.40% during 19 to 32 wk (phase 3). In addition, dietary phytase (500 FTU/kg matrix values) was added into the very low-P diets (0.20% during 13-15 wk, 0.25% during 16-18 wk, and 0.20% during 19-32 wk) to meet the nutritional adequacy with standard P diets. In all phases, decreasing dietary P levels did not affect (P > 0.05) growth, laying performance, and egg qualities. Decreasing dietary P levels linearly increased the relative duodenal and oviduct weights (P < 0.05), and quadratically increased the relative ovary weight in pullets (P = 0.016). Dietary phytase lowered (P = 0.021) the relative duodenal weight compared with the very low-P diet. Tibia breaking strength and tibia Mg contents in pullets were linearly lowered (P < 0.05) as dietary P levels decreased. Dietary phytase tended to increase (P = 0.091) tibia breaking strength and significantly increased (P = 0.025) tibia Mg content compared with the very low-P diet. Dietary P levels and dietary phytase affected (P < 0.05) ileal crypt depth and ileal villus height: crypt depth ratio in pullets. Decreasing dietary P levels linearly decreased (P < 0.01) crude fat digestibility and P excretion in both pullets and laying hens. Dietary phytase reversed (P < 0.05) the very low-P diet-mediated decrease of crude fat digestibility in pullets and laying hens. Dietary P levels and dietary phytase affected (P < 0.05) odor emission including ammonia in pullets and total volatile fatty acids in laying hens. Finally, lowering dietary P levels increased (P < 0.01) yolk corticosterone concentrations and the increased corticosterone concentration by the very low-P diet was reversed by dietary phytase. Collectively, our study shows that decreasing dietary P levels induced nutritional and physiological responses in pullets and laying hens and these P-mediated negative effects were mitigated by dietary phytase.

Scenario analysis of phosphorus flow in food production and consumption system in the Mwanza region, Tanzania

Since the mineral, phosphorus (P), has dual properties of being limited resources for use, and being a pollutant for studying sustainable management of anthropogenic P flows in wetlands and soils, currently P receives the highest interests among researchers around the world. This study has successfully mapped P flows for a reference year (2017) and a future year (2030) using different scenarios of food production and consumption system (hereafter 'system') in the Mwanza region (Tanzania). The results showed that the total P input and output for 2017 alone were 9770 t and 7989 t, respectively. However, as high as 1781 tP accumulated in the system and the potentially recyclable P found, is yet to be recovered due to economic reasons and the lack of market. The main anthropogenic P input to the system occurred via imported feed, fertilizer, and crop food, accounting for about 99.72 % of the total input flow. The output was comprised of animal products exported with 3428 tP, and various P-contained wastes which were lost to water bodies with 4561tP. Analysis of the 2030 scenario showed that setting P management objectives from different perspectives such as the total P budget balance, potential recyclable P, and P emission, can help develop differentially preferred management strategies and measures in the Mwanza region. The combination of diet change, precision feeding, and integrated waste management practices presents the best prospects for decreasing P budget and losses, and the amount of P that can be potentially recovered from the system. We propose a package of integrated P management measures for the Mwanza region. Given the similarity of regional socio-economic development background around the Lake Victoria basin, the model can be used to guide the study of anthropogenic P flow analysis in other areas along the shore of Lake Victoria (Africa).

Digestibility of calcium in calcium-containing ingredients and requirements for digestible calcium by growing pigs

The concentration of Ca in plant feed ingredients is low compared with the requirement for pigs and most Ca in diets for pigs is provided by limestone and Ca phosphate. To determine digestibility values for Ca that are additive in mixed diets, the standardized total tract digestibility (STTD) of Ca needs to be calculated, and the STTD of Ca by growing pigs in most Ca-containing ingredients has been reported. Although Ca is an inexpensive nutrient compared with P and amino acids, excess Ca needs to be avoided because excess dietary Ca results in reduced P digestibility, reduced feed intake, and reduced growth performance of pigs. Recent data indicate that most diets produced for pigs in the United States and Europe contain ~0.20 percentage units more Ca than formulated, which likely is because of the use of limestone as a carrier in feed additives or as a flow agent in other ingredients. An excess of this magnitude without a corresponding excess of P will result in a reduction in daily gain of growing pigs by 50 to 100 g. Greater emphasis, therefore, needs to be placed on determining the concentration of Ca in diets for pigs. Microbial phytase increases the digestibility of both Ca and P and it is, therefore, important that the release of both Ca and P by phytase is considered in diet formulation. However, due to the relationship between Ca and P in postabsorptive metabolism, diets need to be formulated based on a ratio between digestible Ca and digestible P. To maximize average daily gain, this ratio needs to be less than 1.40:1.0 in diets for weanling pigs, and the ratio needs to be reduced as the body weight of pigs increases. In contrast, to maximize bone ash, the digestible Ca to digestible P ratio needs to increase from 1.67:1.0 in 11 to 25 kg pigs to 2.33:1.0 in finishing pigs. Gestating sows have reduced STTD and retention of Ca and P compared with growing pigs and formulation of diets for sows based on digestibility values obtained in growing pigs will result in inaccuracies in the provision of Ca and P. There is, however, a lack of data for the digestibility of Ca and P by gestating and lactating sows, and responses to microbial phytase by sows are not fully understood. There is, therefore, a need for research to generate more data in this area. In the present review, a summary of data for the digestibility of Ca in feed ingredients for pigs and estimates for the requirement for digestible Ca by growing and finishing pigs are provided.

Short communication: commercial diets for pigs in the United States contain more calcium than formulated

Data from Europe indicate that commercial diets for pigs and poultry contain significantly more Ca than formulated. Therefore, a survey of commercial pig diets used in the United States was conducted to test the hypothesis that the analyzed concentrations of total Ca and total P in commercial pig diets in the United States are not greater than formulated values. A total of 103 diet samples from the commercial swine industry in the United States were collected between 2019 and 2021. Diet samples were provided by feed mills, feed companies, or swine farms located in major swine-producing states in the United States including NC, TN, IA, IN, KS, MN, NE, and IL. Diets were formulated for nursery pigs, growing-finishing pigs, or sows. Each company provided formulated values for total Ca and P in all samples. Samples were sent to the University of Illinois where they were ground and analyzed for Ca and P by inductively coupled plasma-optical emission spectrometry. The formulated values for Ca and P were regressed against analyzed values, and the intercept was considered the estimated under- or over-supply of each mineral. Results indicated that there was an average of 0.19 percentage units more Ca (model; P < 0.001) in the diets than formulated, whereas, for total P, the average oversupply was only 0.06 percentage units (model; P < 0.001). In conclusion, diets used in the U.S. swine industry contain more total Ca than formulated, whereas total P is close to formulated values, which indicates that greater importance is given to P than to Ca in formulation. However, the current data indicate that more attention should be given to the actual concentration of Ca in all Ca-containing feed ingredients to avoid Ca oversupply and its detrimental effect on P digestibility and growth performance of pigs fed diets that do not contain excess P.

Addressing the contribution of agricultural systems to the phosphorus pollution challenge: a multi-dimensional perspective

The intensification of agricultural systems has increased the food production efficiency, increasing the productivity while the production costs are reduced. Although these factors are key to global food security in a context of continued human population growth, the use of intensive agricultural techniques results in different environmental issues. Mitigating these negative impacts is a requirement for adopting sustainable food production systems. Notably, nutrient pollution is one of the main environmental issues associated with both livestock and crop production. These activities result in different point and non-point source releases of phosphorus, which eventually reach surface and ground waterbodies. This might result in the accumulation of phosphorus over time, contributing to the eutrophication of water ecosystems, and the development of harmful algal bloom (HABs) episodes. The releases of nutrients from agricultural activities can be abated through different management strategies, including the implementation of nutrient recovery techniques at livestock facilities, embracing precision fertilization methods, and developing integrated crop-livestock systems for achieving circular food production systems. In this work, we describe opportunities for Process System Engineering (PSE) to address the development of phosphorus management techniques for mitigating phosphorus pollution from agricultural systems balancing trade-offs between recovery cost and environmental impact mitigation. These techniques integrate the spatial analysis of nutrient pollution from agriculture using geographical information systems (GIS) with the assessment and the selection of phosphorus management techniques combining techno-economic analysis (TEA) and environmental metrics through multi-criteria decision analysis (MCDA) frameworks, and use mathematical programming for the conceptual design of integrated crop-livestock systems.

Phosphorus nutrition of growing pigs

Phosphorus (P) is an essential nutrient for diverse biological processes, which aggregate to the animal's requirement for P, and nutritionists strive to meet this requirement accurately. The P demand for a growing pig comprises requirements for maintenance and tissue deposition. The P in feed ingredients, however, must be digested and absorbed before its ultimate partition between the 2 aforementioned requirement components. Phosphorus from various sources could behave differently during digestion and absorption, which results in their disparate bioavailability for pigs. The system of standardized total tract digestibility reflects true total tract digestibility of P and feed ingredient effects on specific endogenous P loss with relative ease of implementation, and this system guarantees satisfactory additivity in digestible P among the ingredients in a diet—the foundation for diet formulation. The basal endogenous P loss, which is much easier to measure than the specific endogenous P loss, is considered as part of the pig's maintenance requirement. With this arrangement, a digestibility framework is established both for measuring the P-providing capacity of various feed ingredients and for describing the pig's P requirement. This framework entails basic understanding of the function, digestion, absorption, excretion, and homeostasis of P as support pillars. Understanding the workings of this framework enables potential integration of factors such as environment conditions and disease status in future P requirement models. The current review discusses dietary sources, digestion, absorption, bioavailability and requirement of P for growing pigs to understand the status quo, revealing the points of consensus as well as those of debate, and to encourage further investigation to provide more clarity.

Opportunities to Harness High-Throughput and Novel Sensing Phenotypes to Improve Feed Efficiency in Dairy Cattle

Simple Summary

Sensors, routinely collected on-farm tests, and other repeatable, high-throughput measurements can provide novel phenotype information on a frequent basis. Information from these sensors and high-throughput measurements could be harnessed to monitor or predict individual dairy cow feed intake. Predictive algorithms would allow for genetic selection of animals that consume less feed while producing the same amount of milk. Improved monitoring of feed intake could reduce the cost of milk production, improve animal health, and reduce the environmental impact of the dairy industry. Moreover, data from these information sources could aid in animal management (e.g., precision feeding and health detection). In order to implement tools, the relationship of measurements with feed intake needs to be established and prediction equations developed. Lastly, consideration should be given to the frequency of data collection, the need for standardization of data and other potential limitations of tools in the prediction of feed intake. This review summarizes measurements of feed efficiency, factors that may impact the efficiency and feed consumption of an animal, tools that have been researched and new traits that could be utilized for the prediction of feed intake and efficiency, and prediction equations for feed intake and efficiency presented in the literature to date.

Abstract

Feed for dairy cattle has a major impact on profitability and the environmental impact of farms. Sustainable dairy production relies on continued improvement in feed efficiency as a way to reduce costs and nutrient loss from feed. Advances in breeding, feeding and management have led to the dilution of maintenance energy and thus more efficient dairy cattle. Still, many additional opportunities are available to improve individual animal feed efficiency. Sensing technologies such as wearable sensors, image-based and high-throughput phenotyping technologies (e.g., milk testing) are becoming more available on commercial farm. The application of these technologies as indicator traits for feed intake and efficiency related traits would be advantageous to provide additional information to predict and manage feed efficiency. This review focuses on precision livestock technologies and high-throughput phenotyping in use today as well as those that could be developed in the future as possible indicators of feed intake. Several technologies such as milk spectral data, activity, rumen measures, and image-based phenotypes have been associated with feed intake. Future applications will depend on the ability to repeatably measure and calibrate these data across locations, so that they can be integrated for use in predicting and managing feed intake and efficiency on farm.

Measuring pollutant emissions of cattle breeding and its spatial-temporal variation in China

The rapid development of animal husbandry has resulted in serious pollution issues in the livestock and poultry breeding industry, increasing the cost of environmental management. This issue is particularly prominent in China due to its rapid economic development, significant domestic consumption, and aggressive carbon neutrality targets. This study analyses pollution emissions and spatial-temporal variation in China's cattle breeding industry. Using an emission coefficient method and panel data of 31 Chinese provinces/municipalities between 2002 and 2017, we measure the total volume of pollutant emissions from China's cattle breeding industry and five major pollutants: chemical oxygen demand, total nitrogen, total phosphorus, copper, and zinc. We also analyse the dynamic variation of the spatial distribution. The results show that both the total emissions volume and emissions of the five major pollutants have decreased to different extents, among which chemical oxygen demand has decreased the fastest. Spatial divergence is strengthened as the heavy pollution areas have moved from the southeast to the northwest of the country. This study contributes to current research by its focus on the cattle breading industry and by our improvements to the pollutant emission measurement method.

Phosphorus feeding practices, barriers to and motivators for minimising phosphorus feeding to dairy cows in diverse dairy farming systems

Minimising phosphorus (P) feeding to dairy cows can reduce feed costs and minimise water pollution without impairing animal performance. This study aimed to determine current P feeding practices and identify the barriers to and motivators for minimising P feeding on dairy farms, using Great Britain (GB) dairy farming as an example of diverse systems. Farmers (n = 139) and feed advisers (n = 31) were involved simultaneously in independent questionnaire surveys on P feeding in dairy farms. Data on the herd size, milk yield and concentrate fed were analysed using ANOVA to investigate the effect of farm classification, region, and feed professional advice. Chi-square tests were used to investigate associations between farm characteristics and implemented P feeding and management practices. Most farmers (72%) did not know the P concentration in their lactating cow's diet and did not commonly adopt precision P feeding practices, indicating that cows might have been offered dietary P in excess of recommended P requirement. Farmers' tendency to feed P in excess of recommendations increased with herd size, but so did their awareness of P pollution issues and likeliness of testing manure P. However, 68% of farmers did not analyse manure P, indicating that mineral P fertiliser application rates were not adjusted accordingly, highlighting the risk of P being applied beyond crops' requirement. Almost all farmers (96%) were willing to lower dietary P concentration but the uncertainty of P availability in feed ingredients (30%) and concerns over reduced cow fertility (22%) were primary barriers. The willingness to reduce dietary P concentrations was driven by the prospect of reducing environmental damage (28%) and feed costs (27%) and advice from their feed professionals (25%). Most farmers (70%) relied on a feed professional, and these farmers had a higher tendency to analyse their forage P. However, farmers of pasture-based systems relied less on feed professionals. Both farmers (73%) and feed advisers (68%) were unsatisfied with the amount of training on P management available. Therefore, the training on P management needs to be more available and the influence that feed professionals have over P feeding should be better utilised. Study findings demonstrate the importance of considering type of dairy farming systems when developing precision P feeding strategies and highlight the increasing importance of feed professionals in minimising P feeding.

Trichostrongylus colubriformis affecting sheep phosphorus metabolism and precision feeding as a mitigating strategy

This review details the negative effects of Trichostrongylus colubriformis infection in sheep phosphorus metabolism and direct and indirect impacts from high excretion from susceptible animals, as well as the advantages offered by precision feeding as potential strategies to mitigate loss. In sheep infected with T. colubriformis there is a high reduction in P bioavailability, because of depression in the absorptive capacity of this mineral, affecting the absorption and recycling of P to the digestive tract, causing mineral deficiency. Therefore, precision feeding compiles animal genetics information, feeding type and grazing management to control animal feed intake and quantity and quality of manure produced. In this sense, the adoption of precision feeding can provide a better arrangement of the information, making sheep production more economically, socially and environmentally sustainable.

Effects of phytase supplementation on production performance, egg and bone quality, plasma biochemistry and mineral excretion of layers fed varying levels of phosphorus

Excessive fecal excretion of phosphorus (P) has increasingly become an environmental issue due to oversupply of P in layer rations, and thus it is imperative to minimize safety margins for P to ensure the sustainability of the egg industry. In this study, a 12-week feeding trial (22 to 34 weeks of age) was conducted to evaluate the effects of phytase supplementation on production performance, plasma biochemistry, egg and bone quality and P excretion of laying hens fed various levels of non-phytate P (NPP). Forty-eight Lohmann white laying hens were randomly allocated to one of six corn-soybean meal-oat-based diets: diets containing 2.0, 2.5 or 3.0 g/kg NPP without phytase, and diets containing 1.0, 1.5 or 2.0 g/kg NPP with phytase (1 000 U/kg diet) where phytase inclusion was expected to provide 1.0 g/kg NPP to laying hens, thus making the phytase-unsupplemented treatment served as a control for the phytase-supplemented treatment accordingly. Productive performance was recorded during the experimental period. Blood and egg samples were collected, and digestibility studies were conducted at weeks 6 and 12 of the experiment. Bone mineralization was evaluated at the end of the experiment. Egg weight and egg production, feed consumption, BW and feed conversion ratio of laying hens fed lower NPP diets supplemented with phytase were comparable to those of hens fed high NPP phytase-unsupplemented controls. Eggshell thickness, specific gravity, Haugh units, tibia bone mineral density, tibia ash percent, plasma P and other biochemical parameters were not significantly different among dietary treatments. Total P intake, excretion and retention were affected by diet (P < 0.001), but its deposition in eggs was not significantly different. Contrast analysis further showed that total P excretion of phytase present vs phytase absent was averagely reduced by 40.4 mg/hen per day (P < 0.01). Moreover, total P excretion was linearly (P < 0.01) reduced with lowering dietary NPP, and this relationship was similar regardless of whether phytase was supplemented or not. The results from this study indicated that NPP levels in laying hen diets could be reduced to 1.0 g/kg (excluding the portion of NPP released by phytase) with the inclusion of phytase, without negative effects on production performance and health of the hens, thereby diminishing P excretion into environment.

Impact of reduced dietary crude protein levels and phytase enzyme supplementation on growth response, slurry characteristics, and gas emissions of growing pigs

This experiment was carried out to evaluate the effect of reduced dietary crude protein (CP) levels supplemented with or without exogenous phytase on growing pigs. Six dietary treatments arranged in a 3 × 2 factorial arrangements of 3 CP levels (containing 14%, 16%, and 18% CP) supplemented each with or without 5,000 FTU/g phytase enzyme. Thirty growing pigs (average weight of 17.80 ± 0.10 kg) were allotted to the six dietary treatments in a complete randomized design. The final weight, daily weight gain, and feed conversion ratio (FCR) increased significantly with increasing CP levels. While, phytase supplementation improved (p = .044) FCR in pigs. Total solid and volatile solid content of the slurry were higher (p = .001) in pigs fed 14% and 16% CP diets supplemented with phytase when compared with other treatment groups. Concentration of methane gas emitted was lowest (p = .001) in the slurry of pigs fed 14% CP diet with or without phytase and those fed 16% CP diet with phytase supplementation. In conclusion, reduction in dietary CP levels resulted in reduced weight gain and poor FCR. While, reduced CP with phytase supplementation reduced concentration of methane gas emitted.

Phosphorus digestibility and metabolisable energy concentrations of contemporary wheat, barley, rye and triticale genotypes fed to growing pigs

This study was conducted to determine apparent total tract digestibility (ATTD) of phosphorus (P) and metabolisable energy (ME) concentrations for pigs of 32 different genotypes (n = 8 per grain species) of barley, rye, triticale and wheat. All genotypes were grown at the same location under the same field conditions and were fed to growing castrated crossbred pigs (initial body weight: 31.1 ± 6.95 kg) using a series of duplicate 3 × 3 Latin square designs. A basal ration, which was deficient in P, and 32 experimental rations containing 400 g/kg DM of the basal ration and 600 g/kg DM of the corresponding cereal grain were mixed. Pigs were kept in metabolism crates and the total collection method was used for separate faeces and urine collections with 7-d adaptation and 7-d collection periods. The mean ATTD of P was greater (p < 0.05) for wheat than for triticale, rye or barley (59.4%, 50.4%, 44.9% and 44.4%, respectively, for the mean of each grain species). Within-grain species differences (p < 0.05) among genotypes were obtained for ATTD of P of barley and triticale. The concentrations of ME of triticale and wheat were higher (p < 0.05) than that of barley and rye (16.1 and 16.2 vs. 14.9 and 14.8 MJ ME/kg DM, respectively). Differences in ME concentration among genotypes within a grain species (p < 0.05) were found for barley, triticale and wheat. No differences were found for rye. Compared to literature data the present study showed, in part, considerable differences in ATTD of P and ME concentration. These results should be taken into account for accurate pig ration formulation with regard to minimised P output and efficient use of ME. No significant relationships were detected between ATTD of P and phytic acid concentration or phytase activity in the grain genotypes in this study.

How do pigs deal with dietary phosphorus deficiency?

Feeding strategies for growing monogastric livestock (particularly pigs) must focus on maximising animal performance, while attempting to reduce environmental P load. Achieving these goals requires a comprehensive understanding of how different P feeding strategies affect animal responses and an ability to predict P retention. Although along with Ca, P is the most researched macromineral in pig nutrition, knowledge gaps still exist in relation to: (1) the effects of P feed content on feed intake (FI); (2) the impact of P intake on body composition; (3) the distribution of absorbed P to pools within the body. Here, we address these knowledge gaps by gathering empirical evidence on the effects of P-deficient feeds and by developing a predictive, mechanistic model of P utilisation and retention incorporating this evidence. Based on our statistical analyses of published literature data, we found: (1) no change in FI response in pigs given lower P feed contents; (2) the body ash–protein relationship to be dependent upon feed composition, with the isometric relationship only holding for pigs given balanced feeds and (3) the priority to be given towards P retention in soft tissue over P retention in bones. Subsequent results of the mechanistic model of P retention indicated that a potential reduction in P feeding recommendations could be possible without compromising average daily gain; however, such a reduction would impact P deposition in bones. Our study enhances our current knowledge of P utilisation and by extension excretion and could contribute towards developing more accurate P feeding guidelines.

The Effect of Diet Composition on the Digestibility and Fecal Excretion of Phosphorus in Horses: A Potential Risk of P Leaching?

Simple Summary

This study aimed to examine phosphorus utilization and excretion in feces when typical feeds and forage-based diets are fed. The hypothesis was that feeding regimes might influence phosphorus digestibility and excretion in feces, and therefore the environmental impact of horse husbandry. We also studied the nutrient digestibilities of the diets, as well as the proportion of the soluble fraction of P of the total phosphorus. Horse dung may pose a potential risk of P run-off into the environment if not properly managed. Supplementation with inorganic P should be controlled in the diets of mature horses in light work to decrease the excretion of P in feces.

Abstract

The main horse phosphorus excretion pathway is through the dung. Phosphorus originating from animal dung and manure has harmful environmental effects on waters. The number of horses has increased in many countries, and several studies have pointed that leaching of P from horse paddocks and pastures are hotspots for high P leaching losses. The hypothesis was that feeding regimes might influence phosphorus digestibility and excretion in feces, and therefore the environmental impact of horse husbandry. A digestibility experiment was conducted with six horses fed six forage-based diets to study phosphorus utilization and excretion in feces. The study method was a total collection of feces. The experimental design was arranged as an unbalanced 6 × 4 Latin Squares. Phosphorus intake increased with an increasing concentrate intake. All studied diets resulted in a positive P balance and, the P retention differed from zero in all except the only-hay diet, in which the intake was lower compared to the other diets. The digestibility of P varied from 2.7 to 11.1%, and supplementing forage-diets with concentrates slightly improved P digestibility (p = 0.024), as it also improved the digestibilities of crude protein (p = 0.002) and organic matter (p = 0.077). The horses excreted an average of 20.9 ± 1.4 g/d P in feces. Excretion was smallest (20.0 g) in horses on a hay-only diet (p = 0.021). The average daily phosphorus excretion resulted in 7.6 kg P per year. The soluble P part of the total P in feces accounted for about 88% of the P excreted in feces, and is vulnerable to runoff losses and may leach into waters. Thus, horse dung may pose a potential risk of P leaching into the environment if not properly managed, and is not less harmful to the environment than that from other farm animals. Supplementation with inorganic P should be controlled in the diets of mature horses in light work to decrease the excretion of P in feces.

Interactions between dietary calcium and phosphorus level, and vitamin D source on bone mineralization, performance, and intestinal morphology of coccidia-infected broilers1

Coccidiosis penalizes calcium (Ca), phosphorus (P), and fat-soluble vitamin status, as well as bone mineralization in broiler chickens. We hypothesized that dietary vitamin D (VitD) supplementation in the form of 25-hydroxycholecalciferol (OHD), compared to cholecalciferol (D3), would improve bone mineralization in broilers receiving marginally deficient Ca/P diets, with more pronounced effects during malabsorptive coccidiosis. In a 2 VitD source × 2 Ca/P levels × 2 levels of infection factorial experiment (n = 6 pens per treatment, 6 birds/pen), Ross 308 broilers were assigned to an Aviagen-specified diet supplemented with 4,000 IU/kg of either OHD or D3 between days 11 and 24 of age. The diet contained adequate (A; 8.7:4.4 g/kg) or marginally deficient (M; 6.1:3.1 g/kg) total Ca and available (av)P levels. At day 12 of age, birds were inoculated with water (C) or 7,000 Eimeria maxima oocysts (I). Pen performance was measured over 12 days post-infection (pi). One bird per pen was assessed for parameters of bone mineralization and intestinal histomorphometric features (day 6 and 12 pi), as well as E. maxima replication and gross lesions of the small intestine (day 6 pi). There was no interaction between infection status and Ca/avP level on bone mineralization. Bone breaking strength (BS), ash weight (AW), and ash percentage (AP) were highest in broilers fed the OHD-supplemented A diets irrespective of infection status. Eimeria maxima infection impaired (P < 0.05) ADG and FCR pi; Ca and P status at day 6 pi; OHD status, BS, AW, and AP at day 12 pi; and intestinal morphology at day 6 and 12 pi. A- compared to M-fed broilers had higher BS, AW, and AP at day 6 pi, and AW at day 12 pi. VitD source affected only OHD status, being higher (P < 0.001) for OHD- than D3-fed broilers at day 6 and 12 pi. In conclusion, offering OHD and adequate levels of Ca and P improved bone mineralization, with no effect on performance. Dietary D3 and OHD supplemented at 4,000 IU/kg had similar effects on coccidiosis-infected and uninfected broilers, which led to the rejection of our hypothesis.

Dietary Trace Mineral Level and Source Affect Fecal Bacterial Mineral Incorporation and Mineral Leaching Potential of Equine Feces

Minerals excreted in feces have the potential to leach or runoff to water-ways, negatively impacting water quality. This study examined the effect of dietary trace mineral levels, and their source, on the leaching potential of minerals from equine feces. Nine horses were used in a replicated 3 × 3 Latin Square, with three dietary treatments provided as pellets: no added trace minerals (CON), added inorganic trace minerals (ING), and added organic trace minerals (ORG). Supplemental trace minerals included Co, Cu, Mn, and Zn. Horses were allowed ad libitum access to forage and fed their treatment pellets for 16 days prior to fecal sample collection. Estimated dietary mineral intake exceeded requirements for supplemented minerals. Regardless of the source, adding dietary trace minerals increased the fecal leaching potential of Cu, Zn, and P (p < 0.05). More Co leached from ORG compared to ING, while Zn leached in greater amounts from ING compared to ORG (p < 0.05). Fecal bacterial Zn content was greater (p < 0.05) for ORG compared to ING. Negative correlations were observed between bacterial mineral content and leaching for several minerals. Supplementing trace minerals in forms that increase microbial incorporation may provide a strategy to control fecal mineral leaching.

Standardized total tract digestibility of calcium varies among sources of calcium carbonate, but not among sources of dicalcium phosphate, but microbial phytase increases calcium digestibility in calcium carbonate1

Two experiments were conducted to test the hypothesis that standardized total tract digestibility (STTD) of Ca and the response to microbial phytase is constant among different sources of Ca carbonate and that the STTD of Ca is constant among different sources of dicalcium phosphate (DCP) when fed to growing pigs. In Exp. 1, 80 pigs (initial BW: 19.0 ± 1.9 kg) were randomly allotted to 10 diets and 2 blocks with 4 pigs per diet in each block. Four sources of Ca carbonate were used, and each source was included in a diet without microbial phytase and a diet with microbial phytase (500 units/kg diet). Two Ca-free diets without or with microbial phytase were also formulated. Feed allowance was 2.7 times the maintenance energy requirement for ME and daily feed allotments were divided into 2 equal meals. The initial 4 d of each period were considered the adaptation period to the diets followed by 4 d of fecal collection using the marker-to-marker procedure. Pigs fed diets containing exogenous phytase had lower (P < 0.05) basal endogenous loss of Ca compared with pigs fed diets containing no phytase. There were no interactions between phytase and source of Ca carbonate. Values for STTD of Ca were greater (P < 0.05) for diets containing microbial phytase (77.3% to 85.4%) compared with diets without exogenous phytase (70.6% to 75.2%), and values for STTD of Ca differed (P < 0.05) among the 4 sources of Ca carbonate. In Exp. 2, 40 pigs (initial BW: 14.9 ± 1.3 kg) were allotted to a completely randomized design with 5 diets and 8 replicate pigs per diet. A basal diet in which all Ca was supplied by Ca carbonate was formulated. Three diets were formulated by adding 3 sources of DCP to the basal diet and a Ca-free diet was also used. Feeding and collection methods were as described for Exp. 1. Results indicated that values for STTD of Ca and ATTD of P were not different among diets, indicating that under the conditions of this experiment, the digestibility of Ca and P in DCP appears to be constant regardless of origin of DCP. In conclusion, use of microbial phytase reduces the basal endogenous loss of Ca and increases Ca digestibility in Ca carbonate. The STTD of Ca varies among sources of Ca carbonate, regardless of phytase inclusion, but that appears not to be the case for the STTD of Ca in different sources of DCP.

Addressing Imbalances in Phosphorus Accumulation in Canadian Agricultural Soils

Adequate phosphorus (P) is needed for crop production, but excessive P poses a potential risk to water quality. Results from the cumulative P balance calculations within the indicator of risk of water contamination by phosphorus (IROWC-P) developed in Canada were assessed to determine the spatial and temporal trends in P accumulation at a regional scale and to consider the implications of these trends. Regional cumulative P balances were calculated from census data as a proxy for soil test P (STP) values, including the contribution of fertilizer or manure P to these balances. Ideally, over time we would see a convergence of soil test values at the low end of the critical response range for crop growth, where agronomic and environmental considerations are balanced, but this does not appear to be the case for many regions in Canada. Nationally, about 61% of agricultural land was predicted to be low in STP, and over half of this land is failing to replace the P that is removed each year. While only about 10% of the agricultural land has accumulated significantly more P than is needed for crop growth, almost all of this land is continuing to accumulate P rather than drawing it down. Manure is the dominant P source for continuing accumulation in regions with high or very high estimated STP; reducing this input will be difficult because of the nature of manure and the investment in buildings and infrastructure tied to specific locations, but it is clear that current Canadian policies need strengthened.

Adsorption as a technology to achieve ultra-low concentrations of phosphate: Research gaps and economic analysis

Eutrophication and the resulting formation of harmful algal blooms (HAB) causes huge economic and environmental damages. Phosphorus (P) from sewage effluent and agricultural run-off has been identified as a major cause for eutrophication. Phosphorous concentrations greater than 100 μg P/L are usually considered high enough to cause eutrophication. The strictest regulations however aim to restrict the concentration below 10 μg P/L. Orthophosphate (or phosphate) is the bioavailable form of phosphorus. Adsorption is often suggested as technology to reduce phosphate to concentrations less than 100 and even 10 μg P/L with the advantages of a low-footprint, minimal waste generation and the option to recover the phosphate. Although many studies report on phosphate adsorption, there is insufficient information regarding parameters that are necessary to evaluate its application on a large scale. This review discusses the main parameters that affect the economics of phosphate adsorption and highlights the research gaps. A scenario and sensitivity analysis shows the importance of adsorbent regeneration and reuse. The cost of phosphate adsorption using reusable porous metal oxide is in the range of $ 100 to 200/Kg P for reducing the phosphate to ultra-low concentrations. Future research needs to focus on adsorption capacity at low phosphate concentrations, regeneration and reuse of both the adsorbent and the regeneration liquid.

Review: Environmental impact of livestock farming and Precision Livestock Farming as a mitigation strategy

This paper reviews the environmental impact of current livestock practices and discusses the advantages offered by Precision Livestock Farming (PLF), as a potential strategy to mitigate environmental risks. PLF is defined as: "the application of process engineering principles and techniques to livestock farming to automatically monitor, model and manage animal production". The primary goal of PLF is to make livestock farming more economically, socially and environmentally sustainable and this can be obtained through the observation, interpretation of behaviours and, if possible, individual control of animals. Furthermore, adopting PLF to support management strategies, may lead to the reduction of the environmental impact of farms. Currently, few studies reported PLF efficacy in reducing the environmental impact, however further studies are necessary to better analyze the actual potential of PLF as a mitigation strategy. Literature shows the potentiality of the application of PLF, as the introduction of PLF in farms can lead to a reduction of Greenhouse gases (GHG) and ammonia (NH3) emission in air, nitrates and antibiotics pollution in water bodies, phosphorus, antibiotics and heavy metals in the soil.

The effect of exogenous phytase supplementation on nutrient digestibility, ruminal fermentation and phosphorous bioavailability in Rambouillet sheep

BACKGROUND

The effect of phytase supplementation with respect to a high sorghum grain diet on sheep voluntary feed intake, apparent nutrient digestibility, ruminal fermentation, phosphorus (P) excretion and blood serum P concentration was evaluated.

RESULTS

Phytase supplementation significantly decreased fecal P excretion (P = 0.003), resulting in a 26% decrease in relation to the phytase free diet. Dry matter intake, nutrient digestibility, ruminal butyrate and serum P were not (P > 0.10) affected by the phytase level. Neutral detergent digestibility showed a tendency to increase linearly (P = 0.10) with increasing phytase levels. Ruminal pH was lower for phytase supplemented sheep, with a significant decrease (P = 0.007) at 9 h post feeding, whereas ruminal ammonia-N at 3 h post feeding was lower (P = 0.004) for the phytase treatment groups, resulting in a decreasing linear response (P = 0.001) with an increasing phytase dose. Duodenal pH was significantly reduced at 6 h post feeding. Propionate tended (P = 0.051) to be increased linearly as the phytase supplementation level increased.

CONCLUSION

Exogenous phytase supplementation of high sorghum grain diets significantly decreased fecal P excretion in Rambouillet rams. Phytase supplementation appears to affect neutral detergent fiber digestibility, duodenal and ruminal pH, ammonia and propionate. © 2018 Society of Chemical Industry.

Effects of sodium, 1,25-dihydroxyvitamin D3 and parathyroid hormone fragment on inorganic P absorption and Type IIb sodium-phosphate cotransporter expression in ligated duodenal loops of broilers

Three experiments were conducted with 22-day-old Arbor Acres male broilers to study the effects of Na+, 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] and parathyroid hormone fragment [PTH (1-34)] on inorganic P absorption and Type IIb sodium-phosphate cotransporter (NaP-IIb) mRNA and protein expression levels in ligated duodenal loops. The duodenal loops were perfused with solutions (pH = 6) containing zero, 50, or 150 mmol/L of Na+ as NaCl in Exp. 1, containing zero, 30, or 300 pmol/L of 1,25-(OH)2D3 in Exp. 2, or containing zero, 65, or 650 pmol/L of PTH (1-34) in Exp. 3, respectively. Compared with the control, additions of 50 and 150 mmol/L of Na+, 30 and 300 pmol/L of 1,25-(OH)2D3, or 65 and 650 pmol/L of PTH (1-34) to the perfusates promoted (P < 0.02) the P absorption percentages and rates, respectively. Additions of the above-mentioned concentrations of Na+ or 1,25-(OH)2D3 to the perfusates increased (P < 0.003) NaP-IIb mRNA level in the duodenum of broilers, and a similar trend (P = 0.08) was observed for PTH (1-34). The Na+, 1,25-(OH)2D3, and PTH (1-34) had no effects (P > 0.15) on NaP-IIb protein level in the duodenum of broilers. The results indicate that increased P absorption due to perfusions of Na+, 1,25-(OH)2D3 or PTH (1-34) might be attributed to enhanced NaP-IIb expression in the duodenum of broilers.

Effect of low levels of dietary available phosphorus on phosphorus utilization, bone mineralization, phosphorus transporter mRNA expression and performance in growing pigs

A study was conducted to examine the effects of different dietary levels of available phosphorus (aP) on P excretion, bone mineralization, performance and the mRNA expression of sodium-dependent P transporters in growing pigs. Sixty-day old growing pigs (n = 54) with an average initial BW of 19.50 ± 1.11 kg were randomly allocated to a control diet (C) containing 0.23% available phosphorus (aP), T1 containing 0.17% aP and T2 containing 0.11% aP. There were 6 pens per treatment with 3 pigs per pen. Body weight and feed intake were measured weekly. At the end of each week, one pig from each pen was housed in a metabolic crate for 24 h to collect fecal and urine samples and then sacrificed to obtain third metacarpal (MC3) bones and jejunal and kidney samples. Bones were scanned by Dual Energy X-ray Absorptiometry (DEXA). Fecal and urine samples were sub-sampled and analyzed for P content. The expression of P transporter mRNA in jejunum and kidney samples was measured using quantitative real-time polymerase chain reaction (qRT-PCR). Data were analyzed using GLM procedure of the Statistical Analysis System (SAS Institute version 9.2). Pigs fed the T2 diet had reduced (P < 0.05) average daily gain (ADG) and gain to feed (G:F) compared to those fed the C diet during week 2. Overall, ADG and G:F were also reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C and T1 diets. Bone mineral density (BMD) and bone mineral content (BMC) were reduced (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet throughout the experiment. At week 1, jejunal mRNA expression of Na (+)-dependent phosphate transporter 2 (SLC34A2) was increased (P < 0.01) in pigs fed the T2 diet compared to C diet. Renal mRNA expression of Na(+)-dependent phosphate transporter 1 (SLC34A1) and SLC34A3 were increased (P < 0.05) in pigs fed the T2 diet compared to those fed the C diet at week 2 and was accompanied by lower (P < 0.05) urinary P in pigs fed the T2 diet during week 2 and week 3. In conclusion, growing pigs are highly sensitive to low dietary P as shown by reduced ADG, bone mineralization and urinary P level, but moderate reduction in dietary P up to 0.17% aP in the diet has the potential to reduce environmental pollution by reducing P concentration in swine manure and without compromising performance.

Standardized total tract digestibility of phosphorus in various inorganic phosphates fed to growing pigs

An experiment was conducted to determine the standardized total tract digestibility (STTD) of phosphorus (P) in five sources of inorganic phosphate fed to growing pigs, including dicalcium phosphate (DCP), monodicalcium phosphate (MDCP), monocalcium phosphate (MCP), tricalcium phosphate (TCP) and monosodium phosphate (MSP, reagent grade). Six barrows (42.4 ± 1.1 kg) individually housed in metabolism crates were allotted to a 6 × 6 Latin square design with six dietary treatments and six periods. Each experimental period consisted of a 4 day adaptation period and a 5 day collection period. The five experimental diets contained 0.24 to 0.34% of P from each inorganic phosphate as a sole source of P. A P-free diet was also prepared to estimate the basal endogenous loss of P. The STTD of P in MSP (94.9%) was not different from the STTD of P in MCP (93.0%), but was greater (P < 0.05) than that in DCP, MDCP and TCP (87.0, 86.5 and 71.3%, respectively). In conclusion, digestibility of P in reagent-grade MSP was greater than that in feed-grade inorganic phosphates such as DCP, MDCP and TCP, and digestibility of P in DCP and MDCP was greater than that in the TCP.

Environmental Sustainability Analysis and Nutritional Strategies of Animal Production in China

Animal production in China has achieved considerable progress and contributes to 46% of the total agriculture output value of the country. However, this fast expansion of animal production has led to environmental pollution. In this article, we review the status of soil, water, and air pollution associated with animal production in China and analyze the main sources of the pollutants. The government has promulgated regulations and standards, and effective models and technologies have been developed to control pollution during the last 10 years. Because nutrition and feed strategies represent the most effective method of controlling environmental pollution at the source, this review focuses on nutritional technologies, including accurate feed formulation, rational use of additives, and proper processing of feeds. The advances of modern biotechnology and big data systems also provide more modern approaches to decreasing wastage release. These nutritional strategies are expected to promote sustainable development of animal production.

Vitamin D3 increased intestinal Na/Pi-IIb and CYP27B1 mRNA level in rats fed low-phosphorus diets

The objective of the study was to determine the role of vitamin D₃ (VD₃) in regulating adaptation and mechanism of rats to low-phosphorus (P) diets. Rats were assigned to 4 diets containing 0.2%, 0.4%, 0.6%, or 0.8% P consisting of 5 replicate cages with 6 rats per replicate cage and fed for 7 days. Four rats from each replicate cage were treated with ethane-1-hydroxy-1,1-diphosphonicacid, tetrasodium salt (EHDP) and 2 rats remained untreated. Twelve hours prior to preparation on d 7, two of the EHDP-treated rats received an intraperitoneal injection of VD₃ [1,25-(OH)₂D₃] at 600 ng per kg body weight, while two rats did not receive the injection. Rats that did not receive VD₃ injection had decreased (P < 0.001) P absorption, but injection of VD₃ resulted in increased (P < 0.001) absorption. The effect of VD₃ injection was greater (P < 0.001) for rats fed 0.2% P diet than rats fed 0.8% P diet in ileum. Sodium dependent phosphate cotransporter type Ⅱb (Na/Pi-II b) and 25-hydroxyvitamin D 1-α hydroxylase (CYP27B1) mRNA level showed the same trend with P absorption. Serum concentration of VD₃ and 1α-hydroxylase activity in rats fed 0.2% P diet were lower than those fed 0.8% P diet. The injection of VD₃ increased (P < 0.001) serum concentration of VD₃ and 1α-hydroxylase activity. Thus, VD₃ increased Na/Pi–IIb and CYP27B1 mRNA level and improved serum concentration of VD₃ and 1α-hydroxylase activity in rats fed low-P diets.

Toward improved phosphorus efficiency in monogastrics-interplay of serum, minerals, bone, and immune system after divergent dietary phosphorus supply in swine

Phosphorus (P) is of vital importance for many aspects of metabolism, including bone mineralization, blood buffering, and energy utilization. In order to identify molecular routes affecting intrinsic P utilization, we address processes covering P intake, uptake, metabolism, and excretion. In particular, the interrelation of bone tissue and immune features is of interest to approximate P intake to animal's physiology and health status. German Landrace piglets received different levels of digestible phosphorus: recommended, higher, or lower amounts. At multiple time points, relevant serum parameters were analyzed and radiologic studies on bone characteristics were performed. Peripheral blood mononuclear cells were collected to assess differential gene expression. Dietary differences were reflected by serum phosphorus, calcium, parathyroid hormone, and vitamin D. Bone reorganization was persistently affected as shown by microstructural parameters, cathepsin K levels, and transcripts associated with bone formation. Moreover, blood expression patterns revealed a link to immune response, highlighting bidirectional loops comprising bone formation and immune features, where the receptor-activator of NF-κB ligand/receptor-activator of NF-κB kinase system may play a prominent role. The modulated P supplementation provoked considerable organismal plasticity. Genes found to be differentially expressed due to variable P supply are involved in pathways relevant to P utilization and are potential candidate genes for improved P efficiency.

Smart livestock feeding strategies for harvesting triple gain – the desired outcomes in planet, people and profit dimensions: a developing country perspective

Of the total greenhouse gas emission from the livestock sector, 45% relates to feed production and processing. Enteric methane (35%), land-use change (9%) and manure nitrous oxide and manure methane together (9.5%) are the other sources of greenhouse gas emissions, which to a large extent depend on feed types. Inefficient use of feeds reduces profitability. Increasing future feed demand and food-feed-fuel competition have environmental and social impacts. The growth for demand in livestock products comes with social, economic and environmental challenges. This paper argues that the efficient utilisation of feed resources and application of appropriate feeding strategies are vital for strengthening the three conventional pillars of sustainability (environment, social and economic). Towards this end, it identifies and explores a series of promising innovations and practices in feed production and feeding including balanced and phased feeding; increase in the quality and level of use of forages in diets; reduction in use of grains; harvesting forages when nutrient availability per unit of land is maximum; targeted mineral feeding; reduction in feed losses; use of straw-based densified feed blocks; better recycling of human food wastes and human-inedible food components to feed; new business models for production and use of urea-ammoniated straws, urea-molasses blocks, forages and silages in smallholder farms; and use of underutilised locally available feed crops linked with strengthening of seed development and distribution infrastructure. The development of simple tools and on-site assays for correcting nutritional imbalances also offers interesting opportunities. Collection of data on feed availability at the national level, and generation of sound chemical composition and nutritional value data of feeds, are a prerequisite to innovate. The focus of the discussion will be on low-input livestock systems in developing world. A large number of livestock are found in such systems and small improvements can have high global impact. In addition to the technological aspects, policy and institutional building options required to realise large impact are also discussed.

Effects of protein source and nutrient density in the diets of male broilers from 8 to 21 days of age on their subsequent growth, blood constituents, and carcass compositions

The effects of protein source and amino acid (AA) and AME levels in the diets of male broilers from 8 to 21 d of age on subsequent growth and blood and carcass traits were investigated in the current study. Fourteen Ross × Ross 708 male broiler chicks were randomly allocated to each of 80 floor pens arranged in a randomized complete block design. Each diet contained 1 of 2 dietary protein sources (high inclusion of distillers dried grains with solubles or high inclusion of meat and bone meal), 1 of 2 AA densities (moderate or 10% higher), and 1 of 2 AME densities (2,998 or 3,100 kcal/kg). Experimental diets were fed from 8 to 21 d of age, and common diets from 1 to 7 and 21 to 55 d of age. The higher AME density in high inclusion of meat and bone meal diets increased serum triglyceride and cholesterol levels on d 20. The dietary inclusion of high inclusion of distillers dried grains with solubles or lower levels of AA increased high-density lipoprotein cholesterol on d 20. Feeding the high-AA-density diet decreased feed intake without affecting BW gain, which resulted in a lower feed conversion ratio (FCR). A high-AME-density diet lowered feed intake but increased BW gain, which resulted in a lower FCR from 8 to 21 d of age. Feed intake, BW gain, FCR from 21 to 54 d of age, and carcass weight on 42 and 55 d of age were not affected by treatments from 8 to 21 d of age. However, early dietary manipulation from 8 to 21 d of age affected fat and meat yield at 42 and 55 d of age. Moreover, a high-AME diet decreased feed cost per carcass weight gain from 8 to 55 d of age. In conclusion, high AA or AME densities during the grower phase, from d 8 to 21 of age, may improve growth during the grower feeding phase, but may also affect meat yield during the latter grow-out phases. Furthermore, high-AME diets from 8 to 21 d of age may save on feed costs for meat production.

Whole-farm budgets of phosphorus and potassium on dairy farms in Manitoba

Plaizier, J. C., Legesse, G., Ominski, K. H. and Flaten, D. 2014. Whole-farm budgets of phosphorus and potassium on dairy farms in Manitoba. Can. J. Anim. Sci. 94: 119–128. Whole-farm budgets of phosphorus (P) and potassium (K) were determined on 10 dairy farms in Manitoba between October 2010 and October 2011. These budgets were determined as the difference between total exports, including milk, animals, feed, and manure, and total imports, including feed, manure, animals, and inorganic fertilizer, for each farm. Farms differed in their feeding and manure management strategies. Two farms imported all their feed and exported all their manure. Other farms produced some of their feed and spread most of their manure on their farm. Whole-farm P and K budgets varied from −0.42 to 3.35 and from −1.31 to 11.27 g kg−1 milk sold among farms, respectively. Efficiencies of P and K utilization were calculated as the exports as a percentage of imports. The P efficiency averaged 48%, and ranged from 22.1 to 109% among farms. The K efficiency averaged 37%, and ranged from 10 to 98% among farms. In the fall of 2010 and 2011, 94 and 98%, of fields sampled had soil test P concentrations lower than the concentration above which further accumulation of P would be regulated (60 ppm). Of the farms that spread their own manure, the highest P and K efficiency were on a farm that exported a proportion of the produced forages and did not import any inorganic fertilizer. The lowest P and K efficiencies were on a farm that imported concentrate feeds, bedding straw and most forages, and had the smallest land base per milking cow to spread manure. Variations in P and K efficiencies demonstrate opportunities to enhance these efficiencies.

The Freundlich adsorption isotherm constants and prediction of phosphorus bioavailability as affected by different phosphorus sources in two Kansas soils

Phosphorus (P) adsorption onto soil constituents influences P bioavailability from both agronomic and environmental perspectives. In this study, the P availability from different P sources along with utility of Freundlich adsorption coefficients on the predictability of various crop growth parameters were assessed. Two soils were amended with 150mgPkg(-1) each from six different P sources comprised of manures from two types of ruminants animals, three types of monogastric animals, and inorganic P fertilizer. Corn (Zea mays) was grown and harvested seven times under greenhouse conditions to remove P from the P amended treatments. The application of all P sources reduced the value of Freundlich K and increased the value of Freundlich 1/n and equilibrium P concentration (EPC0) in both soils compared to the un-amended control before cropping. The swine (Sus scrofa) manure (HM) resulted in significant smaller values of Freundlich K and larger values of 1/n in the P deficient Eram-Lebo soil compared to other P sources while, the opposite was true for the turkey (Meleagris gallopava) litter (TL) in the Ulysses soil. The corn biomass, tissue P concentration and P uptake were significantly influenced by all P sources during the first harvest and the total P uptake during seven harvests in both soils compared to the control treatment. Both Freundlich coefficients had strong relationships with the aforementioned corn parameters in the P deficient Eram-Lebo soil while, strength of the association was weak or missing in the Ulysses soil which had optimum levels of antecedent P.

Models to quantify excretion of dry matter, nitrogen, phosphorus and carbon in growing pigs fed regional diets

Modern pig production contributes to many environmental problems that relate to manure, especially in areas with highly intensive production systems and in regions like Asia where the regulative control is not effective. Therefore, the objective of this study was to use three different pig diets varying in dietary protein, fibre and fat as representative for Danish (DK), Thai (TH) and Vietnamese (VN) pig production to develop and evaluate different approaches to predict/calculate excretion from growing pigs in comparison with the experimentally determined values.

Nine female growing pigs were used in a digestibility and balance experiment. Excretion of dry matter (DM), nitrogen (N), phosphorus (P) and carbon (C) of the experimental diets were determined.

Due to the highest dietary fibre content, VN had the lowest digestibility of N, P and C (73, 49, and 73%, respectively) compared with the DK and TH pig diets. From the known diet composition using standard table values on chemical and nutrient digestibly, high accuracy (bias) and low variation was found and the results could be used for prediction on chemical composition and excretion in faeces and urine in growing pigs. Calculation based on standard values regarding nutrient retention in the pig body as used in the Danish manure normative system (DMNS) showed likewise to be quite useful for quantifying the total excretion of N and P.

Overall, the results demonstrate that simple models that require cheap and normally available information on dietary nutrients can give useful information on nutrient excretion in growing pigs.

Seasonal exports of phosphorus from intensively fertilised nested grassland catchments

We carried out a one year (2002) study of phosphorus (P) loss from soil to water in three nested grassland catchments with known P input in chemical fertilizer and animal liquid slurry applications. Chemical fertilizer was applied to the grasslands between March and September and animal slurry was applied over the twelve months. The annual chemical P fertilizer applications for the 17 and 211 ha catchments were 16.4 and 23.7 kg P/ha respectively and the annual slurry applications were 10.7 and 14.0 kg P/ha, respectively. The annual total phosphorus (TP) export in stream-flow was 2.61, 2.48 and 1.61 kg P/ha for the 17, 211 and 1524 ha catchments, respectively, compared with a maximum permissible (by regulation) annual export of ca. 0.35 kg P/ha. The export rate (ratio of P export to P in land applications) was 9.6% and 6.6% from the 17 and 211 ha catchments, respectively. On average, 70% of stream flow and 85% of the P export occurred during the five wet months (October to February) indicating that when precipitation is much greater than evaporation, the hydrological conditions are most favourable for P export. However the soil quality and land use history may vary the results. Particulate P made up 22%, 43% and 37% of the TP export at the 17, 211 and 1524 ha catchment areas, respectively. As the chemical fertilizer was spread during the grass growth months (March to September), it has less immediate impact on stream water quality than the slurry applications. We also show that as the catchment scale increases, the P concentrations and P export decrease, confirming dilution due to increasing rural catchment size. In the longer term, the excess P from fertilizer maintains high soil P levels, an antecedent condition favourable to P loss from soil to water. This study confirms the significant negative water quality impact of excess P applications, particularly liquid animal slurry applications in wet winter months. The findings suggest that restricted P application in wet months can largely reduce the P losses from soil to water.

Invited review: Sustainability of the US dairy industry

The US dairy industry has realized tremendous improvements in efficiencies and milk production since the 1940s. During this time, farm and total cow numbers have decreased and average herd size has increased. This intensification, combined with the shift to a largely urban public, has resulted in increased scrutiny of the dairy industry by social and environmental movements and increased concern regarding the dairy industry's sustainability. In response to these concerns, a group of scientists specializing in animal welfare, nutrient management, greenhouse gas emissions, animal science, agronomy, agricultural engineering, microbiology, and economics undertook a critical review of the US dairy industry. Although the US dairy system was identified as having significant strengths, the consensus was that the current structure of the industry lacks the resilience to adapt to changing social and environmental landscapes. We identified several factors affecting the sustainability of the US dairy industry, including climate change, rapid scientific and technological innovation, globalization, integration of societal values, and multidisciplinary research initiatives. Specific challenges include the westward migration of milk production in the United States (which is at odds with projected reductions in precipitation and associated limitations in water availability for cattle and crops), and the growing divide between industry practices and public perceptions, resulting in less public trust. Addressing these issues will require improved alignment between industry practices and societal values, based upon leadership from within the industry and sustained engagement with other interested participants, including researchers, consumers, and the general public.

True digestible phosphorus requirement of 10- to 20-kg pigs

The objective of this study was to determine the true digestible P requirement of 10- to 20-kg pigs by broken-line regression analysis of growth performance using 6 levels of true total-tract digestible P. In Exp. 1, 48 barrows were used to determine the true total-tract digestibility (TTTD) of P in monocalcium phosphate using the regression method. The dietary treatments included a negative control (3.30 g/kg total P) and 7 additional dietary treatments with incremental addition of 0.74 g/kg P through monocalcium phosphate, resulting in a dietary range of 3.30 to 8.45 g/kg total P. Limestone was added accordingly to maintain a constant Ca to P ratio of 1.25:1 across all diets. A 5-d adjustment period preceded a 5-d total collection of feces. Ferric oxide was used to time the initiation and termination of fecal collection. In Exp. 2, 108 barrows and gilts were used in a 3-wk growth performance study. Monocalcium phosphate was added to a corn-soybean meal-based diet to set up 6 levels of TTTD-based digestible P, ranging from 1.55 to 4.21 g/kg at an increment of 0.53 g/kg digestible P. Limestone was added accordingly to maintain a constant Ca level across all diets. The results of Exp.1 showed dietary P intake, fecal P output, and digested P increased linearly (P < 0.001) with the increasing P level, whereas the apparent total-tract digestibility of P increased both linearly and quadratically (P < 0.01). The regression of daily digested P against daily P intake gave a TTTD of 67.5% for P in monocalcium phosphate. In Exp. 2, ADG increased linearly (P < 0.001) with the increasing P level in wk 1. In wk 2, wk 3, and the overall 3-wk duration, both linear and quadratic effects of P level (P < 0.05) were observed for ADG. Average daily feed intake increased with the addition of monocalcium phosphate linearly in wk 2 (P < 0.05) and during the overall period (P < 0.001) and both linearly (P < 0.001) and quadratically (P < 0.05) in wk 3. For any period, the G:F was improved in both a linear (P < 0.001) and quadratic (P < 0.05) fashion. The true digestible P requirement, defined as the breakpoint using G:F of the overall duration, was estimated to be 3.22, 2.81, and 3.45 g/kg of diet with dietary DM averaged at 887 g/kg for pigs of mixed sex, barrows, and gilts, respectively. Using ADG, the corresponding P requirement was 3.19, 3.40, and 2.97 g/kg of diet. In conclusion, the true digestible P requirement of pigs from 10 to 20 kg BW was determined to be 3.2 g/kg of diet.