The use of P nowadays is raising environmental (eutrophication) and sustainability (limited resource) concerns in the swine industry, but initial trials have shown that similar growth performance can be achieved between pigs fed on a requirement basis and those fed using a P depletion-repletion strategy. To optimise the use of dietary P by pigs, three feeding strategies were studied according to a 3-phase feeding programme: (1) C-C-C providing 100% of the P and Ca requirements, (2) C-LNormal-C, providing 100% of the P and Ca requirements in phases 1 and 3 (C) with a depletion in phase 2 with 60% of the P requirements combined with a normal Ca:digP ratio of 2.6 (LNormal), and 3) C-LHigh-C, providing 100% of the P and Ca requirements in phases 1 and 3 (C) with a depletion in phase 2 with 60% of the P requirements combined with a high Ca:digP ratio of 3.3 (LHigh). Bone mineral content (BMC) and BW were measured at the beginning and end of each phase. BMC gain, average daily gain, average daily feed intake and feed efficiency were calculated for each phase. In phase 1, all pigs received the same diet. At the end of phase 2, the C-LNormal-C and C-LHigh-C groups had similar BMCs compared to the C-C-C group. Finally, at the end of phase 3, the BMC gain was numerically higher in the C-LNormal-C group than in the C-C-C group (25.4 vs 18.7 g/d, P = 0.10). Although depletion did not cause a decrease in BMC in the C-LNormal-C and CLHigh-C groups (versus C-C-C), it did result in better P use during repletion. These results demonstrate the value of a depletion-repletion strategy to reduce P intake and excretion without compromising the final performance. (c) 2024 Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Black soldier fly larvae (BSFL; Hermetia illucens) hold promise for converting biowaste into proteins and lipids for feed. Dietary starch is efficiently digested by the larvae and influences larval performance, but the mechanisms of starch digestion remain poorly understood. This study investigated changes in individual weight and amylase activity in BSFL after 4, 7 and 11 days of feeding for five substrates varying in starch content and type: chicken feed (CF), corn gluten feed (CGF), wheat bran (WB), wheat distillers grain (WDG) and discarded potatoes (DP). Substrate amylase activities were also measured with and without larvae (feeding and fermenting trays, respectively) over time in order to explore external digestion. Feed conversion ratio (FCR) and estimated digestibility (ED) of DM and starch were assessed at the end of the experiment. The ranking for best FCR was CF, WB, CGF, WDG and DP. In feeding trays, ED of DM was 69.8 +/- 1.8, 59.5 +/- 2.9, 58.6 +/- 0.7, 45.4 +/- 0.6 and 19.5 +/- 0.8% in CF, DP, WB, CGF and WDG, respectively. Estimated digestibility of starch reached 100% with WB and CGF, followed by CF (88.2 +/- 2.3%), DP (85. 2 +/- 1.2%) and WDG (43.1 +/- 1.0%). Larval amylase activity increased with growth for all substrates and dropped when approaching pupation. No relationship was found between larval amylase activity and substrate starch or other nutrient content, but a negative correlation was reported with the reducing sugar content of the larvae, suggesting glucose repression of amylase production. Amylase activity decreased with time in all feeding and fermenting substrates except WDG and DP. In vitro degradation assays indicated that BSFL amylase was nine times more efficient on raw corn or wheat starch than on raw potato starch, highlighting that starch structure is a major driver of digestibility. Western blot analysis revealed the presence of BSFL amylase in the feeding substrate, hinting at external digestion. Larval amylase was purified to identify its optimal pH (5.0-6.5) and temperature (70 degrees C). These results highlight that starch content is not a major driver of amylase activity in BSFL and suggest that other noninvestigated factors could have had a crucial impact on the activity of larval digestive enzymes, such as microbial community of the substrate and presence of amylase inhibitors. This study also provides insights into the evolution of BSFL digestive activity during their development and the occurrence of external digestion. (c) 2024 The Author(s). Published by Elsevier B.V. on behalf of The Animal Consortium. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

The aim of this study is built in two phases: to quantify the ability of novel milk metabolites to measure between-animal variability in response and recovery profiles to a short-term nutritional challenge, then to derive a resilience index from the relationship between these individual variations. At two different stages of lactation, sixteen lactating dairy goats were exposed to a 2-d underfeeding challenge. The first challenge was in late lactation, and the second was carried out on the same goats early in the following lactation. During the entire experiment period, samples were taken at each milking for milk metabolite measures. For each metabolite, the response profile of each goat was characterised using a piecewise model for describing the dynamic pattern of response and recovery profiles after the challenge relative to the start of the nutritional challenge. Cluster Analysis identified three types of response/recovery profiles per metabolite. Using cluster membership, multiple correspondence analyses (MCAs) were performed to further characterise response profile types across animals and metabolites. This MCA analysis identified three groups of animals. Further, discriminant path analysis was able to separate these groups of multivariate response/recovery profile type based on threshold levels of three milk metabolites: β-hydroxybutyrate, free glucose and uric acid. Further analyses were done to explore the possibility of developing an index of resilience from milk metabolite measures. Different types of performance response to short-term nutritional challenge can be distinguished using multivariate analyses of a panel of milk metabolites.

The ruminant requirements for essential fatty acids (EFAs), particularly linoleic acid (LA) and alpha-linolenic acid (ALA), have not been fully determined, although evidence suggests that an adequate supply of polyunsaturated fatty acids (FAs) could improve immunity and reproduction in transition cows. In previous studies, we predicted EFA intake for a group of cows based on animal characteristics and milk EFA secretions. However, to support precision livestock feeding, we need to match the nutrient requirements and intakes of each cow as closely as possible. Our group-level predictions may not be accurate enough to estimate the EFA intake of an individual cow, due to inter-individual variations in EFA digestion and metabolism related to differences in feed intake, intake patterns, and the composition and functioning of the rumen microbiota. To address this issue, here we set out to establish specific equations that predict EFA intake for an individual cow based on the difference (i.e. the residuals) between observed EFA intake and the predicted EFA intake based on our group-level equations. We studied a database of individual dairy cows (26 experiments; 503 datapoints from three research teams) and we predicted the residuals from (1) dietary and animal-related factors (i.e. full predictions) and (2) animal-related factors only (i.e. field predictions), which are considered more field-amenable. The variance of predicted LA and log ALA intake was explained to 68% by observed LA intake and 66% by observed log ALA intake, respectively. The residuals of LA intake were predicted by dietary ALA content, total FA intake, BW, milk yield and fat content in full predictions, and by BW, feeding level, milk yield and fat content, and sum of milk C4:0 to C14:0 FA in field predictions. The log residuals of ALA intake were predicted by dietary NDF and total FA contents, NDF intake, BW, milk protein, LA and ALA contents, and fat yield in full predictions, and by BW, DM intake, milk LA and ALA contents, and fat yield in field predictions. The field predictions showed a moderate loss of accuracy compared to full predictions based on RMSE of prediction (from 38 to 54 g/d for LA and from 0.090 to 0.12 log (g/d) for ALA). This work is the first to predict the EFA intake of an individual cow based on previously established group-level predictions of EFA intake adjusted for dietary and animal-related factors.

Black soldier fly larvae (BSFL) are highly efficient at converting organic substrates into insect biomass suitable for livestock nutrition. BSFL conversion efficiency depends on the nature of their feed, and formulation approaches use macronutrient contents to reach a targeted performance. However, digestibility varies between ingredients and BSFL digestibility data is lacking due to methods unsuitable for insects living in their feed. This study proposes to work under a range of larval densities to reach total ingestion of the feed, and defines Estimated Digestibility (ED) as the difference between distributed feed and frass macronutrient weight, divided by macronutrient weight in distributed feed. Using the same amount of chicken feed, same feeding time and 0 to 29 larvae/cm 2 , ED of dry mass (DM), starch, nitrogen, ether extract (EE), neutral detergent fibre, acid detergent fibre, acid detergent lignin, ash and energy were evaluated, along with survival rate, feed conversion ratio (FCR) and larval individual mass gain on a fresh and dry basis. ED of DM, starch, nitrogen, EE and energy increased with larval density following an asymptotic trend. ED of ash increased between 0 and 11.4 larvae/cm2 but decreased for higher densities. Using a logistic model, asymptotic ED of DM (80.3±1.3%), starch (99.0±2.3%), nitrogen (78.6±1.1%), EE (95.3±1.5%), ash (58.4±1.0%) and energy (80.6±1.2%) were determined. No effect of areal density on ED of fibre fractions was detected. Survival rate and individual mass gain peaked at densities below 5 larvae/cm 2 , FCR (dry to fresh) was improved with increasing density, while FCR (dry to dry) was optimised at 11.4 larvae/cm 2 . Asymptotic ED is a new indicator corresponding to the maximal fraction of macronutrients potentially digestible by BSFL. It should be used to develop a diet formulation approach based on digestible rather than crude macronutrient contents. Further studies should focus on evaluating asymptotic ED in different ingredients.

Linoleic acid (LA) and alpha-linolenic acid (ALA) are essential fatty acids found in variable quantities in ruminant feedstuffs. Revision of French feed unit systems in 2018 has proposed the reassessment of energy requirements through a between-experiment approach expressing metabolisable energy supply as a function of the energy expenditures for maintenance and production, with these expenditures that reflect homeorhetic regulations. Based on the same approach, LA and ALA intake can be related to animal characteristics (i.e., BW) reflecting maintenance expenditures and secretion characteristics (i.e., milk yield, milk fat content and contents of LA and ALA in milk fat). Therefore, the objective of this work was to analyse the between-experiment relationships between ingested, duodenal, or absorbed flows of LA and ALA, BW and milk LA and ALA secretion by meta-analysis in mid-lactation dairy cows. These relationships were analysed using LA and ALA subsets of 96 and 99 experiments, respectively. Between-experiment regressions of daily flows of ingested, duodenal or absorbed LA and ALA on BW and milk LA and ALA flows were studied, with statistical unit defined as the mean of within-experiment treatments. For LA, the BW-associated coefficient was 0.019 (±0.0034) g absorbed LA/d per kg BW and milk LA secretion-associated coefficient was 0.70 (±0.081) g absorbed LA/g of LA secreted into milk. For ALA, the BW-associated coefficient was 0.0058 (±0.00093) g absorbed ALA/d per kg BW and milk ALA secretion-associated coefficient was 0.57 (±0.097) g absorbed ALA/g of ALA secreted into milk. When coding the diets as either control or milk fat depression diets, the BW-associated coefficient for LA was 0.017 (±0.0032) g absorbed LA/d per kg BW for both diets. For milk fat depression diets, milk LA secretion-associated coefficient was 1.02 (±0.119) g absorbed LA/g of LA secreted into milk, whereas it was 0.70 (±0.075) g absorbed LA/g of LA secreted into milk for control diets. Significant BW and milk performance coefficients were obtained in all LA and ALA equations, allowing the calculation of ingested and intestinal flows of LA and ALA based on measured BW, milk fat yield and milk fat content of LA and ALA. The relationships between ingested and intestinal flows of LA and ALA, BW and milk performance obtained in the present work could be integrated into renewed feed unit systems for energy and protein in dairy cows.

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. A mechanistic physiologically-based toxicokinetic model of persistent organic pollutants transfer in growing cattle Sylvain Lerch, John Albechaalany, C. Driesen, Philippe Schmidely, Isabelle Ortigues Marty, Marcus Zennegg, Daniel Sauvant, Christelle Loncke

In animal sciences, the number of published meta-analyses is increasing at a rate of 15% per year. This current review focuses on the good practices and the potential pitfalls in the conduct of meta-analyses in animal sciences, nutrition in particular. Once the study objectives have been defined, several key phases must be considered when doing a meta-analysis. First, as a principle of traceability, criteria used to select or discard publications should be clearly stated in a way that one could reproduce the final selection of data. Then, the coding phase, aiming to isolate specific experimental factors for an accurate graphical and statistical interpretation of the database, is discussed. Following this step, the study of the levels of independence of factors and of the degree of data balance of the meta-design represents an essential phase to ensure the validity of statistical processing. The consideration of the study effect as fixed or random must next be considered. It appears based on several examples that this choice does not generally have any influence on the conclusions of a meta-analysis when the number of experiments is sufficient.

Dietary and ruminal factors modify the ruminal biohydrogenation (RBH) of polyunsaturated fatty acids (FA), with duodenal FA flows being quantitatively and qualitatively different from FA intake. Using a meta-analysis approach from a database on duodenal flows of FA in ruminants, this study aimed to determine predictive equations for duodenal and absorbed flows of saturated FA, C18:1, C18:2 and C18:3 isomers, odd- and branched-chain FA (OBCFA), C20:5n-3, C22:5n-3 and C22:6n-3 and to quantify the effects of dietary and digestive factors on those equations. The database was divided into four subsets: forage, seed, vegetable oils or animal fats (oil/fat), and fish products (fish) subsets. Models of duodenal and absorbed FA flows were obtained through variance–covariance analysis. Effects of potential interfering factors (conservation mode and botanical families of forages, lipid source, technological processing of lipid supplements, diet composition and animal characteristics) were analysed. We obtained 83 models for duodenal FA flows as a function of FA intake for saturated FA (C14:0, C16:0 and C18:0), C18:1, C18:2 and C18:3 isomers and seven other models for OBCFA. For the seed/oil/fat subset, intakes of total C18:3, C18:2 and starch content increased the duodenal t11-C18:1 flow with 0.08, 0.16 and 0.005 g/kg of dry matter intake (DMI), respectively, whereas intake level [(DMI×100)/BW] decreased it. The c9c12c15-C18:3 RBH was higher for oil/fat than seed (96.7% v. 94.8%) and a protective effect of Leguminosae v. Gramineae against RBH for that FA appeared in the forage subset. The duodenal C17:0 flow increased with starch content and decreased with ruminal pH, respectively, whereas duodenal iso-C16:0 flow decreased with dietary NDF content for the seed/oil/fat subset. The duodenal C20:5n-3, C22:5n-3 and C22:6n-3 flows depended on their respective intake and the inhibitory effect of C22:6n-3 on duodenal C18:0 flow was quantified. Thirteen models of absorbed FA flows were performed depending on their respective duodenal flows. This study determined the effects of different qualitative and quantitative dietary and digestive factors, allowing for improved predictions of duodenal and absorbed FA flows.

In animal sciences the number of published meta-analyses increases with a rate of 15% per year highlighting an actual success. This current review focuses on the good practices and traps in the conduct of meta-analyses in animal sciences, nutrition in particular. The implementation of a meta-analysis is done in several phases after the definition of the study objectives. Clearly described rules and principles of traceability should be applied as soon as the publications are collected and selected with a target of meta-analysis. Then, the coding phase is essential because it determines the quality of the graphical and statistical interpretations of the database. Following this step, the study of the levels of orthogonality of factors and of the degree of data balance of the meta-design represents an essential phase to ensure the validity of statistical processing. The issue of the choice between fixed or random effect to study and to control heterogeneity is also discussed. It appears on the basis of several examples that this choice does not generally have any influence on the conclusions of a meta-analysis when the number of experiments is sufficient. Finally, reflections are presented on the potential interest of meta-analyses in the context of systemic approaches as well as to improve mechanistic modelling work.

The objective of the study was to evaluate ruminal biohydrogenation (BH) and apparent transfer of long-chain (FA) from duodenum into milk in dairy goats fed Ca salts of palm oil (CaS, 45g/d) or lipid-encapsulated conjugated linoleic acids (LE-CLA, 45g/d providing 4.5g trans-10, cis-12 C18:2/d and 4.5g cis-9, trans-11 C18:2/d). Twelve lactating multiparous dairy Saanen or Alpine goats (65±3 days in milk) were randomly allocated to two experimental treatments (CaS vs LE-CLA) for a 3 wks experiment. The goats were fitted with a ruminal cannula and a T-type duodenal cannula for the measurement of duodenal flow by supplying 2.4g of Cr2O3/d through the rumen cannula during 3 wks: the first one was for reaching steady-state concentration of this marker in the digestive tract, the second wk was for measuring the daily flow of faecal chrome and nutrient faecal digestibility, and the third wk was for the duodenal sampling. LE-CLA did not affect intake, duodenal flow and apparent ruminal digestibility of DM, OM, NDF and starch. Compared to CaS, LE-CLA tended to decrease total digestibility of DM and NDF whereas total digestibility of starch was not affect by dietary treatments. The duodenal flow of FA was higher than FA intake in goats fed CaS or LE-CLA. LE-CLA increased the duodenal flows of C18:2 trans-10, cis-12, and C18:2 cis-9, trans-11, leading to a calculated 16% protection from BH for both FA. The LE-CLA treatment tended to decrease the duodenal flows of C18:2 cis-9, trans-12 and C18:2 trans-9, cis-12. The ruminal biohydrogenation of C18:1 cis-9, C18:2 cis-9, cis-12, and C18:3 cis-9, cis-12, cis-15 was not affected by the LE-CLA treatment. Average apparent transfer between the duodenum and milk fat was 22%, 44%, 36% and 22% for C18:2 trans-10, cis-12, C18:2 cis-9, trans-11+ C18:1 trans-11, C18:2 cis-9, cis-12 and C18:3 cis-9, cis-12, cis-15, respectively. Apparent transfer efficiency of long-chain FA was not affected by LE-CLA treatment.

The aim of this paper was to explore the variation between individuals in the response to and recovery from a nutritional challenge, the repeatability of responses between lactation stages, and the use of shape-clustering methods to classify similar individuals. Sixteen dairy goats were exposed to a 2-d nutritional challenge (underfeeding) at 2 different stages of lactation. Each challenge consisted of a 7-d control period with standard total mixed ration (TMR), 2d of straw-only feeding, and a 10-d recovery period on the TMR. All feeds were offered ad libitum, as was water. The first challenge was in late lactation on primiparous goats (mean days in milk=249), and the second challenge was carried out on the same goats early in the following lactation (mean days in milk=28). The main energetic response traits dry matter intake (DMI), milk yield, body weight, milk fat and protein contents, and plasma glucose, fatty acids (NEFA), β-hydroxybutyrate (BHB), urea, and insulin, were measured daily throughout. A clustering procedure linked to a piecewise mixed model was used to characterize different types of response. As expected, straw feeding caused a large decline in DMI and milk yield, and substantial increases in milk fat and milk protein composition, relative to the prechallenge period on the control TMR. For both DMI and milk yield, the slope of the response, and hence the size of the drop, was strongly related to the prechallenge values, indicating that these 2measures were tightly constrained by the challenge. Regression slopes between lactation stages for responses to the same nutritional challenge were significant for DMI, milk protein content, plasma BHB and urea, and body weight, indicating that within-animal responses in late and early lactation were repeatable. The clustering procedure generally performed well, classifying both scaling differences and differences in shape. The extent of reranking of cluster designations between late lactation and the following early lactation period was examined. For milk yield, DMI, body weight, and urea, relatively little reranking occurred; the numbers of goats not changing class number were 10, 12, 10, and 13, respectively. In contrast, for milk contents of fat and protein, and also for BHB, no clear association was found between late and early lactation class numbers. For NEFA and glucose, these comparisons were not relevant because either the vast majority of goats were in 1 cluster (NEFA) or because an outlier goat skewed the cluster designation (glucose in late lactation). For insulin, 9 out of 16 goats kept the same rank.

Reproductive success is a key component of lifetime efficiency - which is the ratio of energy in milk (MJ) to energy intake (MJ) over the lifespan, of cows. At the animal level, breeding and feeding management can substantially impact milk yield, body condition and energy balance of cows, which are known as major contributors to reproductive failure in dairy cattle. This study extended an existing lifetime performance model to incorporate the impacts that performance changes due to changing breeding and feeding strategies have on the probability of reproducing and thereby on the productive lifespan, and thus allow the prediction of a cow's lifetime efficiency. The model is dynamic and stochastic, with an individual cow being the unit modelled and one day being the unit of time. To evaluate the model, data from a French study including Holstein and Normande cows fed high-concentrate diets and data from a Scottish study including Holstein cows selected for high and average genetic merit for fat plus protein that were fed high- v. low-concentrate diets were used. Generally, the model consistently simulated productive and reproductive performance of various genotypes of cows across feeding systems. In the French data, the model adequately simulated the reproductive performance of Holsteins but significantly under-predicted that of Normande cows. In the Scottish data, conception to first service was comparably simulated, whereas interval traits were slightly under-predicted. Selection for greater milk production impaired the reproductive performance and lifespan but not lifetime efficiency. The definition of lifetime efficiency used in this model did not include associated costs or herd-level effects. Further works should include such economic indicators to allow more accurate simulation of lifetime profitability in different production scenarios.