Dual-energy X-ray absorptiometry: an effective approach for predicting broiler chicken body composition

Two trials were carried out to develop and validate linear regression equations for body composition prediction using Dual-energy X-ray absorptiometry (DEXA). In Trial 1, 300 Cobb500 male chickens raised from 1 to 42 d of age were scanned in DEXA to estimate total weight, fat mass, soft lean tissue (SLT) mass, bone mineral content (BMC), and fat percentage. DEXA estimates were compared to body ash, crude fat, SLT (sum of protein and water) and scale body weight. The dataset was split, with 70% used for prediction equations development and 30% for testing, and the 5k-fold cross-validation analysis was used to optimize the equations. The R2, mean absolute error (MAE), and root-mean-squared error (RMSE) were used as precision and accuracy indicators. A negative correlation (ρ = -0.27) was observed for ash content, while no correlation was observed for protein content (P > 0.05). Predictive linear equations were developed to assess broiler weight (R2 = 0.999, MAE = 25.12, RMSE = 38.99), fat mass (R2 = 0.981, MAE = 13.87, RMSE = 21.28), ash mass (R2 = 0.956, MAE = 3.98, RMSE = 5.61), SLT mass (R2 = 0.997, MAE = 35.73, RMSE = 52.45), water mass (R2 = 0.997, MAE = 29.56, RMSE = 43.94), protein mass (R2 = 0.989, MAE = 12.94, RMSE = 19.05), fat content (R2 = 0.855, MAE = 0.81, RMSE = 1.05), SLT content (R2 = 0.658, MAE = 1.01, RMSE = 1.28), and water content (R2 = 0.678, MAE = 0.99, RMSE = 1.27). All equations passed the test. In Trial 2, 395 Cobb500 male chickens were raised from 1 to 42 d of age and used for validation of prediction equations. The equations developed for weight, fat mass, ash mass, SLT mass, water mass, and protein mass were validated. In conclusion, DEXA was found to be an effective approach for measuring the body composition of broilers when using predictive equations validated in this study for estimate calibration.

Assessment of digestible lysine requirements in lipopolysaccharide-challenged pigs

To evaluate the effect of an E. coli lipopolysaccharide (LPS) challenge on the digestible lysine (Lys) requirement for growing pigs, a nitrogen (N) balance assay was performed. Seventy-two castrated male pigs [19 ± 1.49 kg body weight (BW)] were allocated in a 2 x 6 factorial design composed of two immune activation states (control and LPS-challenged) and 6 dietary treatments with N levels of 0.94, 1.69, 2.09, 3.04, 3.23 and 3.97% N, as fed, where Lys was limiting, with six replicates and one pig per unit. The challenge consisted of an initial LPS dose of 30 μg/kg BW via intramuscular (IM) injection and a subsequent dose of 33.6 μg/kg BW after 48 h. The experimental period lasted 11 days and was composed of a 7-day adaptation and a subsequent 4-day sampling period in which N intake (NI), N excretion (NEX) and N deposition (ND) were evaluated. Inflammatory mediators and rectal temperature were assessed during the 4-day collection period. A 3-way interaction (N levels × LPS challenge × time, P < 0.05) for IgG was observed. Additionally, 2-way interactions (challenge × time, P < 0.05) were verified for IgA, ceruloplasmin, transferrin, haptoglobin, α-1-acid glycoprotein, total protein, and rectal temperature; and (N levels × time, P < 0.05) for transferrin, albumin, haptoglobin, total protein and rectal temperature. LPS-challenged pigs showed lower (P < 0.05) feed intake. A 2-way interaction (N levels × LPS challenge, P < 0.05) was observed for NI, NEX and ND, with a clear dose-response (P < 0.05). LPS-challenged pigs showed lower NI and ND at 2.09% N and 1.69 to 3.97% N (P < 0.05), respectively, and higher NEX at 3.23% N (P < 0.05). The parameters obtained by a nonlinear model (N maintenance requirement, NMR and theoretical maximum N deposition, NDmaxT) were 152.9 and 197.1 mg/BWkg  0.75/d for NMR, and 3,524.7 and 2,077.8 mg/BWkg  0.75/d for NDmaxT, for control and LPS-challenged pigs, respectively. The estimated digestible Lys requirements were 1,994.83 and 949.16 mg/BWkg  0.75/d for control and LPS-challenged pigs, respectively. The daily digestible Lys intakes required to achieve 0.68 and 0.54 times the NRmaxT value were 18.12 and 8.62 g/d, respectively, and the optimal dietary digestible Lys concentration may change depending on the feed intake levels. Based on the derived model parameters obtained in the N balance trial with lower cost and time, it was possible to differentiate the digestible Lys requirement for swine under challenging conditions.

20 Assessment of lysine requirement in lipopolysaccharide-challenged pigs

This study was conducted to investigate the effect of immune challenge (IC) on digestible lysine (Lys) requirement of growing pigs using the Goettingen approach. Twenty-four 19kg-pigs were used in three nitrogen balance (NB) trials. The trials were performed in a complete randomized block design, with six nitrogen levels (NL), two sanitary status (control and IC) and two individual replicates per treatment (6 x 2 x 6). Dietary NL concentration ranged from 1.06 to 4.48 % in DM, being Lys limiting in all the levels assessed. For two consecutive days, Escherichia coli lipopolyssacharide (LPS) was intramuscular injected in challenged pigs at 30 and 34μg/kg. Data were fitted to nonlinear models to estimate nitrogen requirement for maintenance (NMR) and the maximum nitrogen deposition (NDmaxT). Both information were associated with the maximum nitrogen retention (NRmaxT), Lys efficiency (bc-1) and nitrogen retention (NR) to determine Lys requirements as follows: Lys = (lnNRmaxT-ln(NRmaxT-NR))/(16×bc−1). The NRM of pigs from control group was estimated in 152mg of N/kg of BW0,75/day, whereas LPS-challenged pigs had such requirements estimated in 197 N/kg of BW0,75/day. NDmaxT was estimated in 3525 and 2078mg of N/kg BW0,75/day in for pigs form control and LPS-challenged group, respectively. Requirements for Lys were estimated based on 68% and 54% of NDmaxT, being such percentage based on the mean value of ND for each group. Pigs from control group had the requirements for Lys estimated in 1.42 and 1.58%, based on a feed intake of 1000 and 900g/day, respectively, whereas Lys requirements of LPS-challenged pigs were estimated in 0.76 and 0.84%, based 893 and 803g/day of feed intake, respectively. Compared with control, LPS group exhibited a reduction of approximately 11% in feed intake. The model enables to estimate Lys requirement, taking into account protein deposition potential, feed intake, and immune challenge.

19 Assessment of Nitrogen Intake, Excretion and Deposition in lipopolysaccharide-Challenged Pigs

This study was conducted to assess the effect of E. Coli lipopolyssacharide challenge (IC) on Nitrogen Balance (NB) in growing pigs (19 kg). Three NB trials were performed in a complete RBD, with six nitrogen levels (NL), two sanitary status (control and IC) and two individual replicates per treatment (6 x 2 x 6). Pigs were intramuscular injected with 30 and 34 μg LPS/kg for two consecutive days. Dietary NL ranged from 1.06 to 4.48 % (dry matter), with lysine being limiting in all diets. NB trials lasted 11 days in which feces and urine were collected at the last four days to determine N intake (NI), N excretion (NEX) and N deposition (ND). Data were analyzed as two-way ANOVA and polynomial contrasts were used. Body weight were unaffected by the factors under study (P &gt;0,05). LPS-challenged pigs had a lower (P&lt; 0,05) feed intake compared with control group (372,98 vs. 417,82). Interaction between NL and IC were observed (P&lt; 0,05) for NI, NEX and ND. NL linearly increased NI, NEX and ND, with different equations for both groups (P&lt; 0,05): ND = 127,86 + 246,95 NL in control group whereas ND = 150,66 + 155,4 in LPS group. LPS-challenged pigs fed the three highest NL exhibited a decrease in NI compared with control group (P&lt; 0,05). From NL2 to NL6, ND was also impaired in LPS-challenged pigs compared with control. Nitrogen excretion was higher in LPS-challenged pigs fed the two highest NL compared with pigs from control group (P&lt; 0,05). In conclusion, LPS challenge impairs nitrogen retention in growing pigs by 37%. These outcomes can be used further for modelling procedures to estimate lysine requirements of pigs in different sanitary status.

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In-depth pedigree analysis in a large Brazilian Nellore herd

A large herd of Nellore cattle was evaluated using in-depth pedigree analyses. Taking into account the incomplete pedigree due to the use of multiple young sires for mating, the average inbreeding coefficient was calculated as 1.73% for the last generation, which was higher than the regular inbreeding coefficient (0.25%). The effective population size was estimated to be 114, 245, and 101 for the time periods 1995-1999, 1999-2003, and 2003-2007, respectively. Parameters based on the probability of gene origin were used to describe the genetic diversity over time in the herd. The effective number of founders, ancestors, and founder genomes decreased over time, showing an overall loss of genetic diversity. In the last five-year period (2003-2007), based on available pedigree information, one prominent ancestor contributed 10.6% to the gene pool of the herd, and 30% of this pool was contributed by 31 ancestors. The analysis of inbreeding under random mating indicated that the mating strategies used in the herd are slowing down inbreeding rates. However, it is advisable to continue monitoring the inbreeding rates and genetic diversity in this herd in the future.