Nathalie Quiniou

Effect of energy intake on the performance of different types of pig from 45 to 100 kg body weight. 1. Protein and lipid deposition

Between 45 and 100 kg body weight, Large White castrated males (cLW), and crossbred Pietrain × Large White castrated males fcPP×) and boars (bPP×) were either given food ad libitum in experiment 1 or allocated to four energy levels (0·70, 0·80, 0·90, 1·00 ad libitum) in experiment 2. Daily protein and amino acid supplies were calculated to be non-limiting for growth. Protein (PD) and lipid (LD) deposition rates were measured according to the comparative slaughter technique over the whole experimental period (experiments 1 and 2) and according to the nitrogen and energy balance technique at four stages of growth: 48, 64, 79 and 94 kg mean body weight (experiment 2). Average daily gain increased linearly with metabolizable energy (ME) intake, the slope of the relationship being significantly different between types of pig (from −28 to +36 g per additional MJ ME). Daily PD increased with ME intake above maintenance (MEp) according to a linear-plateau relationship in the three types of pig: the slope was significantly affected by type of pig (from +3·4 to 6·0 g per extra MJ MEp) but not by stage of growth. Daily LD increased linearly with MEp intake; neither the type of pig nor the stage of growth affected its slope (+13-5 g per extra MJ MEp). The LD/PD ratio in the extra body-weight gain associated with increased energy intake was affected only by the type of pig.

Effect of dietary crude protein level on protein and energy balances in growing pigs: comparison of two measurement methods

Abstract The effect of dietary crude protein level (17.7: L or 24.3%: H), on nitrogen (N) and energy utilization between 20 and 50 kg body weight, was studied in six groups of two littermate pigs fed close to their ad lib. level. Nitrogen (collection of excreta) and energy (indirect calorimetry) retentions were estimated by continuous balance; results were compared to those obtained on the same pigs by the comparative slaughter technique. Initial body composition of each group of experimental pigs was estimated from other two littermates slaughtered at the beginning of the experiment. Gaseous N, methane losses and N and energy in digesta were also measured. The L pigs retained more energy as fat (7.96 vs 4.94 MJ/d), and less energy as protein (3.19 vs 4.02 MJ/d) than H pigs. The balance technique overestimated the energy retention (+4.4%) and nitrogen retention (+2.5%) as estimated by the comparative slaughter technique. The discrepancy for N doubles when evaporation N losses were not taken into account. The higher discrepancy in energy retention measurement could be related to the accuracy in estimation of the initial body energy content, or with the underestimation of heat production by the equation of Brouwer (1965).

Modelling heat production and energy balance in group-housed growing pigs exposed to low or high ambient temperatures

The effects of ambient temperature (T; 12-29 degrees C), body weight (BW; 30-90 kg) and metabolisable energy intake (ME) on components of energy balance were studied in seven groups of Piétrain x Large White barrows kept in a respiratory chamber. In Expt 1 (groups 1, 2 and 3), T varied in a cyclic way from 22 degrees C to 12 degrees C and then from 12 degrees C to 22 degrees C with three or four consecutive days at each of 22, 19, 16, 14 and 12 degrees C. Similarly, in Expt 2 (groups 4, 5 and 6), T varied from 19 to 29 degrees C and then from 29 to 19 degrees C with three or four consecutive days at each of 19, 22, 25, 27 and 29 degrees C. In both experiments, pigs were offered feed ad libitum. In Expt 3, pigs (group 7) were exposed to the thermic conditions of Expt 1 but their feed allowance was adjusted on a BW basis to the ad libitum intake recorded at 19 and 22 degrees C in Expt 1. Groups 1, 2, 4, 5 and 7 were used over two successive cycles with initial average BW of 37 kg at cycle 1 (four pigs per group) and 63 kg at cycle 2 (three pigs per group). Groups 3 and 6 were studied at an intermediary stage of growth; their initial BW was 45 kg. The O2 and CO2 concentrations, physical activity and feed intake were continuously and simultaneously measured and used to calculate total heat production (HP; HPtot), HP due to physical activity (HPact), activity-free HP (HP0), and thermic effect of feed. HP was modelled as a non-linear function with T, BW and ME as predictors. Results indicate that all components of HP were proportional to BW(0.60). Physical activity was minimal between 19 and 27 degrees C (8 % ME). The estimated lower critical temperature was 24 degrees C. Between 24 and 12 degrees C, total thermic effect of feed decreased from 31 to 16 % ME, but the short-term thermic effect of feed (5.1 % ME) remained constant. Equations for prediction of HPtot, HPact and HP0 according to BW, T and ME are proposed and evaluated according to literature values; values for the feed cost of thermoregulation in pigs are proposed.

Effect of energy intake on the performance of different types of pig from 45 to 100 kg body weight. 2. Tissue gain

The effect of energy supply on physical composition of body weight gain between 45 and 100 kg was studied in Large White castrated males (cLW), crossbred Pietrain × Large White castrated males (cPPX) and boars (bPPX). The pigs were either given food ad libitum and kept in individual pens in experiment 1, or allocated to four energy levels (0·70, 0·80, 0·90, and 1·00 ad libitum ) and kept in metabolism cages in experiment 2. Daily protein supplies were calculated to be the same at the four energy levels within each type of pig and non-limiting for growth. Five additional animals for each type of pig were slaughtered at 45 kg. Daily tissue gain was measured according to the comparative slaughter technique. The daily lean gain increased with metabolizable energy (ME) intake according to a linear-plateau relationship whereas the daily fat gain increased linearly. The type of pig significantly affected the slope of the relationship between lean gain and ME intake (from 15 to 22 g per extra MJ ME) but not the slope of the relationship between fat gain and ME intake (10 g per extra MJ ME on average). Increased energy intake was associated with increased fatness of body-weight gain, which was higher in cLW and cPP× than in bPP×.

Modelling the relation between energy intake and protein and lipid deposition in growing pigs.

When modelling the effect of a changing nutrient supply to growing animals, it is important to distinguish the individual response curve of an animal from the change in this response that may occur during growth. A data analysis model is proposed where, for an individual animal, the relation between protein deposition (PD) and metabolizable energy (ME) intake above maintenance (MEp) is curvilinear, so that PD intersects the origin and reaches its maximum at the maximum protein deposition rate (PDmax). An increase of MEp beyond that required to attain PDmax would not change PD. The MEp not used for protein synthesis can be used for lipid deposition (LD). The relation between PD and LD on the one hand and ME on the other hand can then be described as a function of the maintenance energy requirement (MEm), PDmax, the level of ME required to attain PDmax (F; as a multiple of MEm) and the energetic efficiencies of PD (k p ) and LD (k f ). Of these statistics, only k p and k f were assumed to be independent of body weight (BW), age or genotype. Variation in PDmax was described as a Gompertz function (of age) whereas variation in F was assumed a linear function of BW. Maintenance energy requirement was expressed as a power function of BW. To evaluate the model, 145 nitrogen and energy (indirect calorimetry) balances were obtained from three types of pigs (Large White castrated males (cLW) and Pietrain × Large White castrated males (cPP × ) and males (bPP × )) ranging in BW between 45 and 100 kg and housed under thermoneutral conditions. Animals were allotted to one of four energy levels ranging from 0·70 to 1·00 of ad libitum intake. The MEm was not different between genotypes (849 kJ/kg BW 0·60 ) whereas the k p and k f were 0·56 and 0·75, respectively. For castrated animals on ad libitum intake, PDmax started limiting PD at approximately 130 days of age (78 and 86 kg BW for cLW and cPP × , respectively). Before this age and for bPP × , PD was limited by MEp. In bPP × , the difference between PD and PDmax was small (less than proportionately 0·05). The F did not change with BW for bPP × (2·85 × MEm) whereas for the other genotypes, it decreased linearly from 4·47 at 45 kg to 2·00 at 100 kg of BW. Due to its nature, the model allows estimation of PDmax even when energy is restricting PD.

Influence of high ambient temperatures on food intake and feeding behaviour of multiparous lactating sows

Forty multiparous Large White sows were used to investigate the effects of five ambient temperature levels (18, 22, 25, 27, and 29°C) and two dietary protein contents on their feeding behaviour during lactation. At each temperature treatment, ambient temperature was kept constant over the 21-day lactation period. Dietary protein content was either 140 or 170 g/kg with essential amino acids levels calculated to he non-limiting. Photoperiod was fixed to 14 h of artificial light. The animals were given food ad libitum between the 7th and the 19th day of lactation. Feeding behaviour was not influenced by diet composition. Over the 13 days under ad libitum feeding conditions, voluntary food intake decreased from 7·80 to 3·50 kg/day between 18 and 29°C, which was achieved through a decreased daily number of meals at the highest temperature (6·8 to 4·5 at 18 and 29°C, respectively). No significant difference among temperatures was observed on meal size, even if the highest (1372 g) and the lowest (883 g) values were obtained at 18 and 29°C, respectively. Rate of food intake was not influenced by temperature and averaged 133 g/min; consequently, decreased voluntary food intake under heat exposure resulted in reduced ingestion time (61 and 29 min/day at 18 and 29°C, respectively). Hourly food intake peaked at the beginning and the end of the light period. It resulted in a mainly diurnal partition of food intake. This partition was significantly affected by temperature as proportionately 0·87 and 0·91 of total food intake occurred during the day at 27 and 29°C, respectively, v. 0·81 on average between 18 and 25°C. Number of meals was lower during the night (1·1 v. 5·2 during the day on average); it decreased with increased temperature both during the day and the night. Meal size was lower during the night (938 v. 1080 g during the day on average). The ratio between water and food intake was significantly higher at 29°C (8·1 v. 4·2 l/kg on average between 18 and 27°C). Standing activity averaged 124 min/day with no significant difference between temperatures.

Effect of diurnally fluctuating high ambient temperatures on performance and feeding behaviour of multiparous lactating sows.

Forty-two multiparous Large White sows were used to investigate the effect of diurnally fluctuating temperature (T) on lactation performance and feeding behaviour. The animals were allocated to one of the four thermic treatments: constant T at 25°C (25C) and 29°C (29C) or equal-mean diurnal cyclic T varying from 21 to 29°C (25V) and from 25 to 33°C (29V). Photoperiod was fixed to 14 h of light. The sows were given food ad libitum between the 7th and the 19th day post partům. Lactation performance was measured for all sows whereas the feeding behaviour was recorded only on 28 sows. The ad libitum food intake was comparable at 25C and 25V (6•31 kg/day) as were milk production and body reserves mobilization. In contrast, food intake at 29V was higher than at 29C (4•53 v. 3•48 kg/day) with no difference in milk production between the two treatments. The increased daily food intake at 29V resulted from higher intakes over the coolest periods of the day and especially during the dark period. Neither meal size nor daily number of meals were significantly affected by T. Feeding behaviour was mainly diurnal but with differences between treatments: 0•90 of total food intake at 29C v. 0•78 at the other three T It appears that the effects of diurnally fluctuating T on lactation performance of sows depend on the mean level of T

Accounting for variability among individual pigs in deterministic growth models.

Inclusion of variation in deterministic nutritional models for growth by repeating simulations using different sets of parameters has been performed in literature without or with only hypothetic consideration of the covariance structure among parameters. However, a description of the structure of links among parameters describing individuals is required to generate realistic sets of parameters. In this study, the mean and covariance structure of model parameters describing feed intake and growth were analyzed from 10 batches of crossbred gilts and barrows. Data were obtained from different crossbreeds, originating from Large White × Landrace sows and nine sire lines. Pigs were group-housed (12 pigs/pen) and performance testing was carried out from 70 days of age to ∼110 kg BW. Daily feed intake (DFI) was recorded using automatic feeding stations and BW was measured at least every 3 weeks. A growth model was used to characterize individual pigs based on the observed DFI and BW. In this model, a Gompertz function was used to describe protein deposition and the resulting BW gain. A gamma function (expressing DFI as multiples of maintenance) was used to express the relationship between DFI and BW. Each pig was characterized through a set of five parameters: BW₇₀ (BW at 70 days of age), B(Gompertz) (a precocity parameter) PDm (mean protein deposition rate) and DFI₅₀ and DFI₁₀₀ (DFI at 50 and 100 kg BW, respectively). The data set included profiles for 1288 pigs for which no eating or growth disorders were observed (e.g. because of disease). All parameters were affected by sex (except for BW₇₀) and batch, but not by the crossbreed (except for PDm). An interaction between sex and crossbreed was observed for PDm (P < 0.01) and DFI₁₀₀ (P = 0.05). Different covariance matrices were computed according to the batch, sex, crossbreed, or their combinations, and the similarity of matrices was evaluated using the Flury hierarchy. As covariance matrices were all different, the unit of covariance (subpopulation) corresponded to the combination of batch, sex and crossbreed. Two generic covariance matrices were compared afterwards, with (median matrix) or without (raw matrix) taking into account the size of subpopulations. The most accurate estimation of observed covariance was obtained with the median covariance matrix. The median covariance matrix can be used, in combination with average parameters obtained on-farm, to generate virtual populations of pigs that account for a realistic description of mean performances and their variability.

Comparison of in vivo and in silico growth performance and variability in pigs when applying a feeding strategy designed by simulation to control the variability of slaughter weight

Variability in bodyweight (BW) among pigs complicates the management of feeding strategies and slaughter. Including variability among individuals in modelling approaches can help to design feeding strategies to control performance level, but also its variability. The InraPorc model was used to perform simulations on 10 batches of 84 crossbred pigs each to characterise the effect of feeding strategies differing in amino acid supply or feed allowance on the mean and variation in growth rate. Results suggested that a feed restriction reduces the coefficient of variation of BW at first departure for slaughter (BW1) by 34%. Growth performance obtained from an in silico simulation using ad libitum and restricted feeding plans was compared with results obtained in an in vivo experiment on a batch of 168 pigs. Pigs were offered feed ad libitum or were restricted (increase in feed allowance by 27 g/day up to a maximum of 2.4 and 2.7 kg/day for gilts and barrows, respectively). A two-phase feeding strategy was applied, with 0.9 and 0.7 g of digestible lysine per MJ of net energy (NE) in diets provided before or after 65 kg BW, respectively. Actual growth was similar to that obtained by simulation. Coefficient of variation of BW1 was similar in vivo and in silico for the ad libitum feeding strategy but was underestimated by 1 percentage point in silico for the restriction strategy. This study confirms the relevance of using simulations performed to predict the level and variability in performance of group housed pigs.

A herd modelling approach to determine the economically and environmentally most interesting dietary amino acid level during the fattening period

For a sustainable pork production, emission of pollutants from pig farms has to be reduced as much as possible whilst economical results have to be maximised. To evaluate different feeding strategies in terms of economic performance and environmental impact (through nitrogen excretion), we simulated herd performance using the prediction model InraPorc. A population of 1000 virtual pigs was generated. Performance of these pigs was simulated using different feeding strategies varying in digestible lysine to NE ratio in the diet (85 to 115% of the mean population requirement) and number of diets used (i.e. a 1-phase feeding strategy, a 2-phase strategy or a continuous multiphase strategy where the lysine/NE ratio was changed daily according to requirement). Diets were formulated on a least-cost basis using two contexts of ingredient prices: September 2007 (P1) or March 2009 (P2). Simulations were ended at a mean population body weight of 112 kg. Average daily gain increased while feed-to-gain ratio and duration of growth decreased with increasing lysine content. Maximum performance was achieved for a supply between 105 and 115% of the mean population requirement for lysine/NE. Increasing the lysine/NE ratio from 85 to 100% for the 1-phase strategy and to 105% for multiphase strategies reduced total feed cost in both economic contexts. The financial return (carcass payment minus feed and labour costs) increased with increasing lysine/ NE ratio and was maximal with the multiphase strategy and a lysine/NE ratio corresponding to 110% of the mean population requirement. When using a lysine/NE ratio greater than the mean population requirement, multiphase feeding strategies reduced nitrogen excretion by 3 to 16% compared with 1-phase strategy. The relationship between financial return and nitrogen excretion depended on the feeding strategy. Using multiphase strategies allows to better match the nutrient supply to the requirement. Based on feed cost alone, it allows optimizing economic return while reducing nitrogen excretion. Apart from the interest of including the variation between animals, stochastic simulation modelling can be helpful in multiple criteria evaluation of feeding practices.