Precision feeding and management of growing-finishing pigs typically require mathematical models to forecast individual pig performance from past data. The current approaches, namely double ...exponential smoothing (DES) and dynamic linear regression are likely to have some limitations in their applicability since they: (1) assume that responses can be forecasted linearly, which only holds in the short-term, and (2) often take insufficient account of uncertainty and correlations in the estimated traits. We developed and evaluated alternative approaches to forecasting individual growth or intake responses based on nonlinear models (allometric, monomolecular, rational) and Bayesian methodology to fit models to the data and generate probabilistic forecasts. We applied these approaches to individual data from two distinct pig populations, to parameterise the models (fitting based on a training dataset) and forecast performance (forecast horizons: 1–30 d tested on a validation dataset). We found that good fitting did not guarantee accurate forecasting, which is quantitatively relevant in the medium-to-long term. Forecasts from nonlinear models were more accurate compared to those from benchmark linear models, with the allometric model being more accurate for most pigs across considered forecast horizons. While DES was the best model at fitting, it was also the least accurate at forecasting for all forecast horizons. These results enhance the understanding of how underlying biological growth responses could be approximated using straightforward mathematical relationships. The approach could be utilised to formulate optimised feeding strategies and inform management decisions, including pen allocation or end-weight prediction.
•Nonlinear and linear predictive models of individual pig growth or intake were tested.•Bayesian forecasting offered key advantages relative to previous estimation methods.•Good fit of a model to the early data does not guarantee accurate forecasts.•Nonlinear model forecasts (1–30 d ahead) were the most accurate (≈0.5–8.0%).•Allometric models can be useful tools for forecasting pig growth responses.
A systematic review and meta-analysis was conducted to investigate the role of Eimeria species, dose and inoculation time, on performance and infection outcomes of different broiler strains infected ...for different study durations. The meta-analysis addressed E. acervulina, E. maxima, E. tenella, and mixed species infections, and involved data from 72 peer-reviewed articles, corresponding to 521 treatments performed on 20,756 broilers. A secondary objective was to investigate the effects of synthetic anticoccidials, ionophores, and vaccination against Eimeria on the above outcomes. Performance during infection was scaled (%) to that of the uninfected birds. Infection reduced scaled ADFI and ADG (P < 0.001) and increased feed conversion ratio (FCR; P < 0.05); there was a significant interaction between dose and species on scaled ADFI and ADG, suggesting that different species affected these variables to different extents (P < 0.001). There was a tendency for an interaction between dose and broiler strain on scaled ADFI (P = 0.079), and a significant interaction between these variables on scaled ADG (P < 0.01). A tendency for an interaction between oocyst dose and Eimeria species (P = 0.067) on maximum number of oocysts excreted was observed. Lesion scores were significantly affected by dose, species, and their interaction (P < 0.05), the latter caused by an increase in the lesion scores during E. maxima and E. tenella infections. Control methods significantly affected scaled ADG and FCR (P < 0.05) and there was an interaction between dose and control methods on ADFI (P < 0.001). Synthetic anticoccidial use improved scaled ADG (P < 0.01), whereas ionophores improved FCR compared with untreated birds (P < 0.01). An interaction between dose and control method on scaled ADFI was caused by the higher ADFI of vaccinated compared to untreated birds, as dose increased. There was a significant effect of control methods on lesion scores (P < 0.01). All findings advance our understanding of the factors that influence the impact of coccidiosis and its controls in broilers.
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.
Ca digestibility and utilisation in growing pigs are not well understood, and are usually neglected in diet formulation. This has implications not only for the accurate determination of its ...requirements but also for its interactions with other nutrients. A systematic review and meta-analysis (meta-regression) of published trials was carried out to quantify factors affecting Ca absorption and utilisation, and to derive an estimate of Ca endogenous excretion. The analysis was carried out on the data from forty studies, corresponding to 201 treatments performed on 1204 pigs. The results indicated that although Ca absorption and retention (g/kg of body weight per d) increased with increasing Ca intake (P<0·001), non-phytate-P intake (P<0·001) and exogenous phytase supplementation (P<0·001), these values decreased with increasing phytate-P intake (P<0·05). Interactions between exogenous phytase and Ca intake, indicating reduced efficacy of this enzyme (P<0·001), and between phytate-P intake and exogenous phytase, counteracting the direct negative effect of phytate-P (P<0·05) on Ca absorption and retention, were also detected. There were no effects of animal-related characteristics, such as pig genotype in Ca absorption and retention. The large amount of variance explained in Ca absorption (90 %) and retention (91 %) supported our choice of independent variables. Endogenous Ca losses obtained via linear regression were 239 mg/kg of DM intake (95 % CI 114, 364). These outcomes advance the current understanding of Ca digestibility and utilisation, and should contribute towards establishing requirements for digestible Ca. Consequently, pig diets will be more correctly formulated if digestible Ca values are used in estimating requirements for Ca.
Recent technological advances make it possible to deliver feeding strategies that can be tailored to the needs of individual pigs in order to optimise the allocation of nutrient resources and ...contribute toward reducing excess nutrient excretion. However, these efforts are currently hampered by the challenges associated with: (1) estimation of unobserved traits from the available data on bodyweight and feed consumption; and (2) characterisation of the distributions and correlations of these unobserved traits to generate accurate estimates of individual level variation among pigs. Here, alternative quantitative approaches to these challenges, based on the principles of inverse modelling and separately inferring individual level distributions within a Bayesian context were developed and incorporated in a proposed precision feeding modelling framework. The objectives were to: (i) determine the average and distribution of individual traits characterising growth potential and body composition in an empirical population of growing-finishing barrows and gilts; (ii) simulate the growth and excretion of nitrogen and phosphorus of the average pig offered either a commercial two-phase feeding plan, or a precision feeding plan with daily adjustments; and (iii) simulate the growth and excretion of nitrogen and phosphorus across the pig population under two scenarios: a two-phase feeding plan formulated to meet the nutrient requirements of the average pig or a precision feeding plan with daily adjustments for each and every animal in the population. The distributions of mature bodyweight and ratio of lipid to protein weights at maturity had median (IQR) values of 203 (47.8) kg and 2.23 (0.814) kg/kg, respectively; these estimates were obtained without any prior assumptions concerning correlations between the traits. Overall, it was found that a proposed precision feeding strategy could result in considerable reductions in excretion of nitrogen and phosphorus (average pig: 8.07 and 9.17% reduction, respectively; heterogenous pig population: 22.5 and 22.9% reduction, respectively) during the growing-finishing period from 35 to 120 kg bodyweight. This precision feeding modelling framework is anticipated to be a starting point toward more accurate estimation of individual level nutrient requirements, with the general aim of improving the economic and environmental sustainability of future pig production systems.
Abstract
The development of dietary recommendations based on digestible Ca values is an essential step to optimize pig performance and feed conversion because the present guidelines, expressed on ...total dietary Ca, are inadequate, as they ignore endogenous losses and the digestion process. A systematic review and meta-analysis of digestibility trials were performed to quantify factors affecting Ca absorption and retention, and to estimate endogenous Ca losses. Forty studies, corresponding to 201 dietary treatments performed on 1,204 growing pigs, were selected. Data analysis was performed in R using weighted linear mixed effects regression. The results indicated that while Ca absorption and retention (g/kg of BW/day) increased with increasing Ca (P < 0.001), with non-phytate-P (P < 0.001) and with exogenous phytase intakes (P < 0.001), these responses decreased with increasing phytate-P intake (P < 0.05). Interactions were detected between exogenous phytase and Ca intake (P < 0.001), indicating reduced efficacy of this enzyme, and between phytate-P intake and exogenous phytase (P < 0.05), indicating reversing of the direct negative effect of phytate-P on Ca absorption and retention. Based on the recommended Ca and P intake for a 25 kg pig, an exogenous phytase supplementation of 1,000 FTU/day could potentially improve Ca digestibility by 20–25%. There were no effects of animal characteristics (e.g. ‘genotype’) on Ca absorption and retention. The large amount of variance explained in Ca absorption (90%) and retention (91%) supported our a priori choice of independent variables. Estimated endogenous Ca losses were 239 mg/kg of DM (95% CI 114, 364). When scaled by bodyweight, the endogenous Ca excretion on Ca-and-P-free diets was 20.5 mg/kg of BW/day (95% CI 5.46, 36.5). These outcomes should contribute to a reassessment of Ca requirements, which should lead to a more accurate formulation of pig diets.
Abstract
Key underlying assumptions of current pig growth models, developed in the context of nutritionally balanced feeds, may be invalid for pigs given inadequate dietary phosphorous (P). To ...account for pig performance on feeds of different P content, a dynamic, mechanistic growth model was developed where ingested P is allocated to either soft tissue or skeletal tissue. The following issues needed to be addressed: 1) potential impact of different dietary P concentrations on feed intake; 2) estimation of the whole-body protein (Pr):P relationship; 3) allocation of ingested P into different body tissues. Statistical analyses of the published literature data, utilising meta-regression indicated the following answers: 1) there was no compensatory feed consumption in pigs fed P-deficient diets (p > 0.05); 2) the whole-body Pr:P relationship was feed-dependent, i.e., body P was directly proportional to body Pr in pigs fed P-adequate diets but lower in pigs fed P-deficient diets; 3) P retention in the soft tissue was prioritised over P deposition in bone when the dietary P was low (p < 0.001). A growth model incorporating mechanisms based on the above data analyses suggests that pigs given P-limiting feeds attempt to maintain the same level of lean tissue retention attained with a P-balanced diet, but at the expense of reduced skeletal deposition. Specifically, bone P growth was reduced in relation to a balanced-diet for moderately-P-deficient diets, and static for severely-P-deficient diets. The overall average daily gain remained largely unaffected for moderately-P-deficient pigs. The present in-silico framework of P kinetics could be utilised to study the consequences of different P feeding strategies on animal growth and body composition, and to verify whether further reduction in dietary P requirements could be achieved with no loss in animal performance.
The development of dietary recommendations based on digestible Ca values is an essential step to optimize pig performance and feed conversion because the present guidelines, expressed on total ...dietary Ca, are inadequate, as they ignore endogenous losses and the digestion process. A systematic review and meta-analysis of digestibility trials were performed to quantify factors affecting Ca absorption and retention, and to estimate endogenous Ca losses. Forty studies, corresponding to 201 dietary treatments performed on 1,204 growing pigs, were selected. Data analysis was performed in R using weighted linear mixed effects regression. The results indicated that while Ca absorption and retention (g/kg of BW/day) increased with increasing Ca (P < 0.001), with non-phytate-P (P < 0.001) and with exogenous phytase intakes (P < 0.001), these responses decreased with increasing phytate-P intake (P < 0.05). Interactions were detected between exogenous phytase and Ca intake (P < 0.001), indicating reduced efficacy of this enzyme, and between phytate-P intake and exogenous phytase (P < 0.05), indicating reversing of the direct negative effect of phytate-P on Ca absorption and retention. Based on the recommended Ca and P intake for a 25 kg pig, an exogenous phytase supplementation of 1,000 FTU/day could potentially improve Ca digestibility by 20-25%. There were no effects of animal characteristics (e.g. 'genotype') on Ca absorption and retention. The large amount of variance explained in Ca absorption (90%) and retention (91%) supported our a priori choice of independent variables. Estimated endogenous Ca losses were 239 mg/kg of DM (95% CI 114, 364). When scaled by bodyweight, the endogenous Ca excretion on Ca-and-P-free diets was 20.5 mg/kg of BW/day (95% CI 5.46, 36.5). These outcomes should contribute to a reassessment of Ca requirements, which should lead to a more accurate formulation of pig diets.
Low-x QCD from CMS Misiura, Maciej; the CMS Collaboration
arXiv.org,
10/2013
Paper, Journal Article
Odprti dostop
In this paper, selected CMS measurements sensitive to low-x QCD are presented: inclusive cross-sections for forward-central jets production at \sqrt{s}=7 TeV, inclusive cross-sections for forward ...jets production at 7 TeV and 8 TeV, inclusive to exclusive dijets production cross-sections ratios and correlations of Mueller-Navelet dijets at 7 TeV. Results for data are compared to predictions of theoretical models.
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