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

Access to bedding and outdoor runs for growing-finishing pigs: is it possible to improve welfare without increasing environmental impacts?

Providing bedding or access to an outdoor run are husbandry aspects intended to improve pig welfare, which is currently financially supported through animal welfare schemes in several European countries. However, they may significantly affect the environment through changes in feed efficiency and manure management. Therefore, the aim of this paper was to compare farms differing in animal welfare relevant husbandry aspects regarding (1) the welfare of growing-finishing pigs and (2) environmental impact categories such as global warming (GW), acidification (AC), and freshwater (FE) and marine eutrophication (ME), by employing an attributional Life Cycle Assessment. We collected data on 50 farms with growing-finishing pigs in seven European countries. Ten animal-based welfare indicators were aggregated into three pig welfare indices using principal component analysis. Cluster analysis of farms based on husbandry aspects resulted in three clusters: NOBED (31 farms without bedding or outdoor run), BED (11 farms with bedding only) and BEDOUT (eight farms with bedding and outdoor run). Pigs on farms with bedding (BED and BEDOUT) manipulated enrichment more often (P < 0.001), pen fixtures less frequently (P = 0.003) and showed fewer oral stereotypies (P < 0.001) than pigs on NOBED farms. There were fewer pigs with a short(er) tail on farms with than without bedding (P < 0.001). Acidification of BEDOUT and BED farms was significantly higher (compared to NOBED farms P = 0.002) due to higher ammonia emissions related to farmyard manure. Also, BEDOUT farms had higher ME than NOBED farms (P = 0.035). There were no significant differences regarding GW and FE between husbandry clusters, due to the large variability within clusters regarding feed composition and conversion. Therefore, both husbandry aspects associated with improved animal welfare have a significant influence on some environmental impacts, such as acidification and marine eutrophication. Nevertheless, the large variation within clusters suggests that trade-offs may be minimised through e.g. AC and ME.

Genetic analyses of nutrient digestibility measured by fecal near-infrared spectroscopy in pigs

Improved nutrient digestibility is an important trait in genetic improvement in pigs due to global resource scarcity, increased human population and greenhouse gas emissions from pork production. Further, poor nutrient digestibility represents a direct nutrient loss, which affects the profit of the farmer. The aim of this study was to estimate genetic parameters for apparent total tract digestibility of nitrogen (ATTDn), crude fat (ATTDCfat), dry matter (ATTDdm), and organic matter (ATTDom) and to investigate their genetic relationship to other relevant production traits in pigs. Near-infrared spectroscopy was used for prediction of total nitrogen content and crude fat content in feces. The predicted content was used to estimate apparent total tract digestibility of the different nutrients by using an indicator method, where acid insoluble ash was used as an indigestible marker. Average ATTDdm, ATTDom, ATTDn, and ATTDCfat ranged from 61% to 75.3%. Moderate heritabilities was found for all digestibility traits and ranged from 0.15 to 0.22. The genetic correlations among the digestibility traits were high (>0.8), except for ATTDCfat, which had no significant genetic correlation to the other digestibility traits. Significant genetic correlations were found between ATTDn and feed consumption between 40 and 120 kg live weight (F40120) (-0.54 ± 0.11) and ATTDdm and F40120 (-0.35 ± 0.12) and ATTDom and F40120 (-0.28 ± 0.13). No significant genetic correlations were found between digestibility traits and loin depth at 100 kg, nor backfat thickness at 100 kg (BF), except between BF and ATTDn (-0.31 ± 0.14). These results suggested that selection for improved feed efficiency through reduced feed intake within a weight interval, also has led to improved ATTDdm, ATTDom, and ATTDn. Further, the digestibility traits are heritable, but mainly related to feed intake and general function of the intestines, as opposed to allocation of feed resources to different tissues in the body.

A Holistic Approach to Evaluating Linear and Non-Linear Mixed Models to Predict Phosphorus Retention in Growing and Finishing Pigs

Simple Summary

Phosphorus (P) is an essential mineral in the diets of pigs. The degree to which P is utilized has both economic and environmental consequences to the swine industry. Mathematical models can be used to describe the relationship between P intake and P retention. These models provide information regarding P utilization that can be used to formulate diets aimed at reducing P overfeeding, and therefore decrease P wastage. The objective of this study was to assess the ability of four non-linear models (monomolecular, Michaelis-Menten, Richards, and Morgan) and one simple linear model to describe the relationship between P intake and P retention in growing and finishing pigs. Through fitting these models to data from P balance studies, non-linear models which describe diminishing returns type behaviour, the monomolecular and the Michaelis-Menten models, were found to best describe the relationship between P intake and P retention in these categories of pig. The parameter of these models allows estimates of endogenous P losses, P requirement for maintenance and theoretical maximum P retention enabling the more efficient use of P in the swine industry.

Abstract

The ability of four non-linear mixed models and one linear mixed model to describe phosphorus (P) retention as a function of dietary P intake, expressed on an available P (avP) basis, was assessed in growing and finishing pigs. Of the four non-linear models, the monomolecular and Michaelis-Menten describe diminishing returns behaviour, while the Richards and Morgan describe sigmoidal behaviour with the ability to also describe diminishing returns. Using a meta-analysis approach, models were fitted to avP intake vs. P retention data from P balance studies. Pig bodyweights (BW) ranged from 43.5 to 133 kg, P intake ranged from 0.055 to 0.468 g kg⁻¹ BW^0.75 d⁻¹ for avP, and 0.151 to 0.806 g kg⁻¹ BW^0.75 d⁻¹ for total P, with P retention ranging from 0.026 to 0.329 g kg⁻¹ BW^0.75 d⁻¹. Models were evaluated using statistical measures of goodness-of-fit and inspection of residuals. The monomolecular and Michaelis-Menten best described the relationship between P retention and P intake. Endogenous P losses and P requirement for maintenance were found to be higher in finishing pigs compared to growing pigs as BW increased.

Pig Manure Management: A Methodology for Environmentally Friendly Decision-Making

The current trend towards larger pig farms increases their profitability but might harm animal welfare and the environment. More efficient pig manure management is a way to address this challenge. Available manure handling and utilisation systems may feature from 8 to 50% nutrient loss to the environment. Therefore, the proper choice of technological solutions is of high priority. In regard, the study developed a methodology including calculation, analysis and modelling techniques for the accurate accounting of manure amount, its fractions and their nitrogen and phosphorus content for different processing technologies with due regard to the limiting factors of the farm and the end-product consumer requirements. The methodology was applied to justify the best suitable processing technology for a large-scale pig farm in the Leningrad Region with 17,800 heads of pigs and 54,750 t of pig manure per year. The selected technology included manure separation into fractions, aeration and secondary sedimentation of the liquid fraction and passive composting of the solid fraction. It demonstrated the total amount of nitrogen (N) and phosphorus (P) in the end-products of 278.94 t per year, with the 26% total nutrients loss on all technological stages, and specific capital and operating costs of USD 55.5 per ton of manure produced. The methodology was tested by comparing the calculated data and the data from previous surveys of 15 pig farms in Russia. The differences between the values were found from 0.9 to 12.5% in mass; 2.8 to 13.9% in N content and 1.7 to 9.9% in P content. The developed methodology supports planning the production of the manure-based end-products in a given amount and with target nutrient content, depending on different processing technological solutions, achieving both economic and environmental goals.

Methodologies on estimating the energy requirements for maintenance and determining the net energy contents of feed ingredients in swine: a review of recent work

In the past two decades, a considerable amount of research has focused on the determination of the digestible (DE) and metabolizable energy (ME) contents of feed ingredients fed to swine. Compared with the DE and ME systems, the net energy (NE) system is assumed to be the most accurate estimate of the energy actually available to the animal. However, published data pertaining to the measured NE content of ingredients fed to growing pigs are limited. Therefore, the Feed Data Group at the Ministry of Agricultural Feed Industry Centre (MAFIC) located at China Agricultural University has evaluated the NE content of many ingredients using indirect calorimetry. The present review summarizes the NE research works conducted at MAFIC and compares these results with those from other research groups on methodological aspect. These research projects mainly focus on estimating the energy requirements for maintenance and its impact on the determination, prediction, and validation of the NE content of several ingredients fed to swine. The estimation of maintenance energy is affected by methodology, growth stage, and previous feeding level. The fasting heat production method and the curvilinear regression method were used in MAFIC to estimate the NE requirement for maintenance. The NE contents of different feedstuffs were determined using indirect calorimetry through standard experimental procedure in MAFIC. Previously generated NE equations can also be used to predict NE in situations where calorimeters are not available. Although popular, the caloric efficiency is not a generally accepted method to validate the energy content of individual feedstuffs. In the future, more accurate and dynamic NE prediction equations aiming at specific ingredients should be established, and more practical validation approaches need to be developed.

A historical perspective on soil organic carbon in Mediterranean cropland (Spain, 1900-2008)

Soil organic carbon (SOC) management is key for soil fertility and for mitigation and adaptation to climate change, particularly in desertification-prone areas such as Mediterranean croplands. Industrialization and global change processes affect SOC dynamics in multiple, often opposing, ways. Here we present a detailed SOC balance in Spanish cropland from 1900 to 2008, as a model of a Mediterranean, industrialized agriculture. Net Primary Productivity (NPP) and soil C inputs were estimated based on yield and management data. Changes in SOC stocks were modeled using HSOC, a simple model with one inert and two active C pools, which combines RothC model parameters with humification coefficients. Crop yields increased by 227% during the studied period, but total C exported from the agroecosystem only increased by 73%, total NPP by 30%, and soil C inputs by 20%. There was a continued decline in SOC during the 20th century, and cropland SOC levels in 2008 were 17% below their 1933 peak. SOC trends were driven by historical changes in land uses, management practices and climate. Cropland expansion was the main driver of SOC loss until mid-20th century, followed by the decline in soil C inputs during the fast agricultural industrialization starting in the 1950s, which reduced harvest indices and weed biomass production, particularly in woody cropping systems. C inputs started recovering in the 1980s, mainly through increasing crop residue return. The upward trend in SOC mineralization rates was an increasingly important driver of SOC losses, triggered by irrigation expansion, soil cover loss and climate change-driven temperature rise.

Prediction of fecal nitrogen and phosphorus excretion for Chinese Holstein lactating dairy cows

Mathematical models for predicting nitrogen and phosphorus excretion play a key role in manure application and environment monitoring. An analysis for prediction of fecal nitrogen (FN, g/d) and fecal phosphorus (FP, g/d) excretion for Chinese Holstein lactating dairy cows was conducted using a data set from 15 dairy farms in northern China. The whole independent-variable data set, obtained with questionnaires, consisted of 110 sets of average diet nutrient compositions, including DMI (kg/d), CP content (% DM), OM intake (OMI, kg/d), nitrogen intake (NI, g/d), and phosphorus intake (PI, g/d), and animal characteristics, including average days in milk (DIM, d), average milk yield (MY, kg/d), and average BW (kg). In addition, 110 fecal samples in total were collected to analyze FN and FP excretions, which were considered dependent variables of prediction equations. Correlations between diet and animal variables were examined, and several variable subpools were derived that were used to develop equations to predict FN and FP excretions by stepwise regression analysis. The results showed that among all variables, OMI was the best predictor for FN excretion (root-mean-square prediction error [RMSPE] = 9.58%, = 0.70), followed by NI (RMSPE = 10.19%, = 0.67). However, when both DMI and CP were used as independent variables, the equation showed more accurate prediction for FN excretion (RMSPE = 8.55%, = 0.77) in comparison with univariate prediction equations. Simultaneously, PI was the best predictor of FP excretion (RMSPE = 10.28%, = 0.67). Evaluation results using 3-fold cross validation and comparison with extant equations indicated that the proposed equations were accurate with low prediction errors, which could be recommended for use to estimate FN and FP excretions from Chinese Holstein lactating dairy cows.

Biogas production from vietnamese animal manure, plant residues and organic waste: influence of biomass composition on methane yield

Anaerobic digestion is an efficient and renewable energy technology that can produce biogas from a variety of biomasses such as animal manure, food waste and plant residues. In developing countries this technology is widely used for the production of biogas using local biomasses, but there is little information about the value of these biomasses for energy production. This study was therefore carried out with the objective of estimating the biogas production potential of typical Vietnamese biomasses such as animal manure, slaughterhouse waste and plant residues, and developing a model that relates methane (CH4) production to the chemical characteristics of the biomass. The biochemical methane potential (BMP) and biomass characteristics were measured. Results showed that piglet manure produced the highest CH4 yield of 443 normal litter (NL) CH4 kg(-1) volatile solids (VS) compared to 222 from cows, 177 from sows, 172 from rabbits, 169 from goats and 153 from buffaloes. Methane production from duckweed (Spirodela polyrrhiza) was higher than from lawn grass and water spinach at 340, 220, and 110.6 NL CH4 kg(-1) VS, respectively. The BMP experiment also demonstrated that the CH4 production was inhibited with chicken manure, slaughterhouse waste, cassava residue and shoe-making waste. Statistical analysis showed that lipid and lignin are the most significant predictors of BMP. The model was developed from knowledge that the BMP was related to biomass content of lipid, lignin and protein from manure and plant residues as a percentage of VS with coefficient of determination (R-square) at 0.95. This model was applied to calculate the CH4 yield for a household with 17 fattening pigs in the highlands and lowlands of northern Vietnam.