Estimating The Dynamic Requirements Of Lysine In Individually-fed Growing-finishing Pigs

In industrial or semi-industrial swine production systems, feed cost might represent more than 60% of the overall production costs. For the growing-finishing pigs, the production objectives of modern animal production systems were, and maybe still are, the maximisation of production performance (i.e. growth rate, reproduction, etc.) at minimal cost. Nutrient requirements show large variation between pigs and actual group feeding systems are limited by the fact that pigs are fed with a unique feed during long periods, thus resulting in low nutrient efficiencies. This feeding system results in underfeeding of amino acids to some pigs, which decrease performance and overfeeding of amino acids to other pigs, which increase the nutrient excretion. Precision feeding is proposed as an essential approach to improve the utilization of dietary nutrients and thus reduce feeding costs and nutrient excretion. Precision feeding involves the use of feeding techniques that allow the right amount of feed with the right composition to be provided at the right time to each pig in the herd. Actual methods estimating nutrient requirements need however be calibrated for real-time individual feeding. Lysine (Lys) is proposed to be evaluated first because this amino acid is available in its purified form and is considered the first limiting amino acid in growing-finishing pigs. Therefor, the present studies focus on the research of Lys requirement.1. A meta-analysis was performed to identify the main factors influencing growing-finishing pig responses to increasing levels of dietary Lys and to evaluate the adequacy of the factorial method used to estimate the standardized ileal digestibility Lys (SIDLys) requirements (LysReqs). A database composed of information from 38 publications published between 1974 and 2008 including 78 experiments and totalizing 360 treatments dealing with 15356 pigs was completed. The results obtained as following:①Average daily feed intake (ADFI) increased with the standardized ileal digestible Lys to net energy (SIDLys:NE) dietary concentration when the SIDLys:NE was lower than 0.6 and 0.5 g/MJ thresholds for growing and finishing pigs, respectively. Above these thresholds, pigs seem to respond less in terms of ADFI to variations of SIDLys:NE dietary concentrations. In growing pigs, the increase of the estimated residual lysine intake (ResLys) across experiments with the increase of SIDLys:NE was curvilinear (α: P = 0.002; b1: P = 0.461; b2: P < 0.001). In the finishing pig group, the increase of ResLys with the increase of SIDLys:NE was linear (α: P < 0.001; b1: P < 0.001; b2: P = 0.207).②Average daily gain (ADG) and gain to feed (G:F) increased quadratically with dietary Lys content (ADG, P<0.001; G:F, P<0.001) in both periods. The finishing pigs showed higher maximal ADG (931 vs 759g/d) but required lower SIDLys:NE (1.104 vs 0.965 g/MJ). The opposite was observed for G:F where maximal response is higher for growing than for finishing pigs (0.49 vs 0.35 g/g). However, growing pigs need more SIDLys:NE compared to finishing pigs to reach the maximal G:F (1.176 vs 1.019 g/MJ). Barrows had higher ADG than gilts regardless of SIDLys:NE while the opposite was observed for G:F.③Estimated the factorial mothod build with the normally accepted parameters, the results showed the daily Lys requirement (g/d) estimated by the factorial method assuming assuming that Lys maintenance requirements were of 0.036xBW0.75, that 16% of the BW gain was protein, that 7 % of the body protein was Lys, and that the efficiency of SIDLys for retention was of 75 %, was underestimated for both growing and finihisng group. Average population values over growth intervals underestimate the population requirements and can not be used as the population representative to estimate the population requirements by the factorial method.2. Ten pigs (24.3±3.4kg) were surgically fitted with T-cannulas at the ileo-cecal junction; four experiment diets were evaluated in the study. The results showed the AID coefficient of four experiments were 90.38%、82.87%、84.41% and 76.13% and the corresponding dietary apparent ileal digestible (AID) Lys content was 1.22%、0.69%,0.43% and 0.25%. The analyzed values matched the calculated ones. So the analyzed values of dietarys nutrient contents were used in the further study.3. In the represent study, the growing-finishing pigs were fed precisely by using the new automatic and intelligent precision feeder (AIPF), which developed especially for this project. Individual daily AIDLys requirement (g/d) was estimated by the factorial method assuming that Lys maintenance requirements were of 0.036xBW0.75, that 16% of the BW gain was protein, that 7 % of the body protein was Lys, and that the efficiency of AIDLys for retention was of 72 %. The objective of this study was to estimate the dynamic evolution of Lys requirements at which 25-50 kg and 70-100 kg bodyweight pigs when fed individually, daily tailored diets. The obtained results as following:①In both groups, ADG and protein deposition (PD) increased linearly (P<0.001) when increasing Lys concentration from 60 to 110% requirements. In the first group, maximal ADG (1.0 kg/d) and PD (174 g/d) were however obtained in pigs fed at requirements (100%), and the ResLys was close to zero with 100% requirements. This indicated the proposed model used in this study estimating individual Lys requirements seems appropriate for pigs fed from 25 to 55 kg BW. In pigs fed from 70 kg BW, the ResLys was close to zero when fed at the 110% requirement, ADG and PD maximal values (ADG: 1.19 kg/d; PD: 185 g/d) were obtained in pigs fed at the maximal level. This indicates the porposed model seems to underestimate the Lys requirements of 70-100 kg BW group.②The calibrated results based on the actual animal peroformance data showed that the ratio of protein in BW gain and the efficiency of AIDLys for retention was different for different individual and different dietary lysine content in different growth period. The ratio of protein in BW gain (16%) and the efficiency of AIDLys for retention (72%) in the proposed model were underestimated in 25-55 kg groups, but were overestimated in 70-100 kg groups.4. Growing-finishing pigs were fed by traditionally three-phase feeding program and daily individual precision feeding program respecitively, evaluating the animal growth performance, analysising the feed cost and the excretion of N, P, and the obtained results as following:①Compare to the traditional three-phase feeding system, growing-finishing pigs fed with daily individual precision feeding program have Feeding 25-55 kg pigs with daily tailored diets reduced N and P intake respectively by 17% (P=0.013) and 9.7% (P=0.037), and the corresponding excretions were reduced respectively by 40.5% (P<0.001) and 31.2% (P<0.01). Feeding 70-100 kg pigs with daily tailored diets reduced N and P intake respectively by11.6% (P=0.002) and 7.9% (P=0.037), and the corresponding excretions were reduced respectively by 26.5% (P<0.001) and 14.2% (P=0.019).②Compare to the traditional three-phase feeding system, feeding 25-100 kg pigs with daily tailored diets can reduce per pig the amount of soybean 11.15 kg, 0.25 kg of phosphates. The feed cost reduce per pig $4.00 (equal about $25.00).