Effects of increasing dietary arginine supply during the three first weeks after weaning on pig growth performance, plasma amino acid concentrations, and health status

A total of 425 weaned pigs (Exp. 1: 225 pigs [5.8 ± 0.9 kg]; Exp. 2: 200 pigs [6.1 ± 1.2 kg]) were used to determine the optimal dietary standardized ileal digestible (SID) arginine (Arg) level in early nursery diets based on growth and health responses. The basal diet in Exp.1 was formulated to meet SID Arg recommendation (0.66%; NRC, 2012) and in Exp. 2, SID Arg was set to simulate current industry practices for feeding nursery pigs (1.15 %). Basal diets were supplemented with 0.3%, 0.6%, 0.9%, and 1.2% of l-arginine to provide five levels of dietary SID Arg. Experimental diets were fed during phases I (days 0 to 7) and II (days 8 to 21) with common diets until market. Feed disappearance and body weight (BW) were measured on days 7, 14, 21, and 43. Final BW was recorded at first removal of pigs for market. Pen fecal score was assigned daily from days 0 to 21. Plasma immunoglobulin A (IgA) was determined on days 0, 7, and 14 and amino acids (AAs) concentration and plasma urea nitrogen (PUN) on days 0 and 14. Orthogonal polynomial contrasts were used to determine the linear and quadratic effects of dietary Arg. Optimal SID Arg was determined by fitting the data with piecewise regression, using growth performance as the primary response variable. In Exp. 1, dietary Arg linearly increased (P < 0.1) BW, average daily gain (ADG), and gain to feed ratio (G:F) ratio on day 21, as well as reduced (χ2 = 0.004) the percentage of pigs that lost weight (PLW) in week 1 by 29%. Dietary Arg resulted in linear improvement (P = 0.082) of ADG for the overall nursery period and quadratic improvement (P < 0.1) of final BW at marketing. In Exp. 2, dietary Arg linearly increased (P < 0.05) ADG and average daily feed intake (ADFI) in week 1, BW and ADFI (P < 0.1) on day 14, as well as reduced (χ2 ≤ 0.001) PLW in week 1. From days 0 to 21, G:F was improved quadratically (P < 0.1). Dietary Arg linearly increased (P < 0.1) ADG and BW on day 43. Dietary Arg supplementation decreased the incidence (χ2 < 0.05) of soft and watery feces during the first weeks after weaning and lower concentration of plasma IgA on days 7 and 14. Dietary Arg linearly and/or quadratically influenced plasma AA concentrations (P < 0.05), including an increase in Arg, Leu, Phe, Val, citrulline, ornithine, and PUN concentrations. Overall, weaned pigs exhibit optimal nursery growth performance and health when provided with dietary SID Arg ranging from 1.5% to 1.9%. This dietary range contributes to a reduction in the occurrence of fall-back pigs and improvements in final BW at marketing.

The Linear-Logistic Model: A Novel Paradigm for Estimating Dietary Amino Acid Requirements

This study aimed to determine whether current methods for estimating AA requirements for animal health and welfare are sufficient. An exploratory data analysis (EDA) was conducted, which involved a review of assumptions underlying AA requirements research, a data mining approach to identify animal responses to dietary AA levels exceeding those for maximum protein retention, and a literature review to assess the physiological relevance of the linear-logistic model developed through the data mining approach. The results showed that AA dietary levels above those for maximum growth resulted in improvements in key physiological responses, and the linear-logistic model depicted the AA level at which growth and protein retention rates were maximized, along with key metabolic functions related to milk yield, litter size, immune response, intestinal permeability, and plasma AA concentrations. The results suggest that current methods based solely on growth and protein retention measurements are insufficient for optimizing key physiological responses associated with health, survival, and reproduction. The linear-logistic model could be used to estimate AA doses that optimize these responses and, potentially, survival rates.

118 Awardee Talk: An Empirical Model of Essential Amino Acid Requirements in the Pregnant Sow

Amino acid (AA) requirements are generally considered to be the minimum needed for maximum growth or protein synthesis; however, multiple studies have shown that AA intakes above these requirements improve various body functions such as immune response, gut health, and reproduction. The objective of the current modeling approach was to estimate AA intake in gestation that considered protein synthesis as well as sow reproductive performance and offspring development, potentially increasing piglet growth and survivability. A literature review was conducted to identify studies evaluating the effects of sow AA intake during gestation on protein synthesis, sow body weight, litter size, average piglet birth weight and suckling piglet growth rate. Data from 26 empirical studies from 1989 to 2021 were selected for model development and estimation of arginine, leucine, lysine, methionine, threonine, and valine requirements. To check model accuracy and performance, a validation analysis was conducted by contrasting the model predicted lysine requirements with data from 17 published studies not used in the development of the model. The estimated lysine requirement was approximately 40% greater than the minimum lysine intake required for maximum protein synthesis. Similarly, the ratios of arginine, leucine, methionine, and valine to lysine were on average 1.60, 2.47, 0.41, and 0.79, respectively, which are 6 to 300% greater than, and the ratio of threonine to lysine was similar to, current recommendations. The validation analysis showed that the estimated lysine requirement resulted in the greatest litter size and birth weight. In addition, when compared with lysine intakes that met current recommendations, lysine intake at the estimated requirement improved colostrum and milk quality, stillborn rate, proportion of low birth weight, suckling piglet growth rate, and sow blood urea, among other metabolic variables. In conclusion, at the estimated requirements sow reproductive performance as well as piglet survivability and growth rate are improved.

151 A Web Application to Establish Customized Feeding Program and Nutrient Specifications for Highly Prolific Sows

A web application was developed to provide a dynamic feeding program for PIC maternal dam lines during gilt development, gestation, peri-partum, lactation and wean-to-service interval (WSI). These recommendations for each production phase are based on peer-reviewed large-scale commercial research. The tool was developed using the Shiny package of R and includes CSS themes, html widgets, and JavaScript actions. Inputs, include pigs weaned per sow per year (PWSY), farrowing rate (FR), total born (TB), replacement rate, the existing feeding program of the breeding herd and the diet energy and standardized ileal digestible (SID) lysine (Lys) levels. Outputs include the feeding program, nutrient specifications and estimates of economic opportunity and performance improvement. The feeding program is based on user-defined energy and SID Lys levels for the gestation and lactation diets and the PIC nutrient recommendations for the breeding herd. Correspondingly, recommended specifications of other nutrients in the diets are provided and calculated based on the recommended feeding program. The tool provides economic and productivity opportunity analysis by comparing the PIC recommendations and the current user feeding programs. Improvement in PWSY is driven by the energy intake impact on caliper score during breeding and farrowing and consequently to FR and TB. This web application can be used by nutritionists and production managers to compare their current feeding practices to PIC recommendations for highly prolific sows. This will aid in their decision-making process regarding nutrition and feeding programs considering productivity and profitability outcomes.

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122 A Mechanistic Model of Growth and Amino Acid Deposition in the Pregnant Sow: Model Development, Evaluation, and Application

A mechanistic model was developed with the objective to characterize weight gain and essential amino acid (EAA) deposition in the different tissue pools that make up the pregnant sow: placenta, allantoic fluid, amniotic fluid, fetus, uterus, mammary gland, and maternal body were considered. The data used in this modelling approach were obtained from published scientific articles reporting weights, crude protein (CP), and EAA composition in the previously mentioned tissues; studies reporting not less than 5 datapoints across gestation were considered. A total of 12 scientific articles published between 1977 and 2020 were selected for the development of the model and the model was validated using 11 separate scientific papers. The model consists of three connected sub-models: protein deposition (Pd) model, weight gain model, and EAA deposition model. Weight gain, Pd, and EAA deposition curves were developed with nonparametric statistics using splines regression. The validation of the model showed a strong agreement between observed and predicted growth (r2 = 0.92, root mean square error = 3%). The proposed model also offered descriptive insights into the weight gain and Pd during gestation. The model suggests that the definition of time-dependent Pd is more accurately described as an increase in fluid deposition during mid-gestation coinciding with a reduction in Pd. In addition, due to differences in CP composition between pregnancy-related tissues and maternal body, Pd by itself may not be the best measurement criteria for the estimation of EAA requirement in pregnant sows. The proposed model also captures the negative maternal Pd that occurs in late gestation and indicates that litter size influences maternal tissue mobilization more than parity. The model predicts that the EAA requirements in early and mid-gestation are 75, 55 and 50% lower for primiparous sows than parity 2, 3 and 4+ sows, respectively, which suggest the potential benefits of parity segregated feeding.

Efficiency of standardized ileal digestible lysine utilization for whole body protein deposition in pregnant gilts and sows during early-, mid-, and late-gestation

The efficiency of SID Lys utilization (kSID Lys) in gilts and sows during early (days 48 to 52), mid (days 75 to 79), and late gestation (days 103 to 107) was investigated using 88 pregnant females (PIC 1050; 27 gilts, 27 parity 1 sows, 34 parity 2+ sows; 192.96 ± 22.84 kg at days 42 ±1 of gestation) and whole body nitrogen (N) retention balance studies. Females were assigned to 1 of 4 SID Lys levels ranging from 40% to 70% of the daily SID Lys requirements above maintenance for a parity 1 sow according to the NRC (2012) gestating sow model in each gestation period. Experimental diets were isocaloric (3,335 kcal ME/kg) and isoproteic (11.75 % CP) and dietary indispensable AA were set to meet or exceed 100% of AA:Lys ratios. The slope of the linear response to graded SID Lys intake was defined as kSID Lys. With the aim of increasing the accuracy of kSID Lys estimates, gilt data from the current study was combined with gilt data from a previous study conducted at the same facility using 4 SID Lys levels ranging from 60% to 90% of the daily SID Lys requirements above maintenance for gilts according to the NRC (2012) gestating sow model. Whole body Lys retention of the combined gilt data set was assessed with different broken-line and nonlinear models. The kSID Lys was 0.65, 0.38, and 0.52 for early-, mid-, and late-gestation, respectively, in gilts. A linear response to graded SID Lys intake was found in late gestation only in parity 1 and 2+ sows; kSID Lys was determined as 0.44 and 0.52 in late gestation for parity 1 and parity 2+ sows, respectively. There were no differences in kSID Lys in late gestation between parities. For the combined gilt data, the model of best performance (reduced error and greater goodness of fit) was the Hoerl model. Maximum kSID Lys (i.e., g SID Lys retention/g SID Lys intake) in gilts was 0.67, 0.54, and 0.53 in early, mid, and late gestation predicted at 7.2, 9.1, and 13.5 g of SID Lys intake/d, respectively, based on the Hoerl model. Maximum SID Lys retention in gilts was similarly predicted at 8.5, 10.5, and 20.9 g of SID Lys intake per day in early, mid, and late gestation and resultant kSID Lys of 0.61, 0.51, and 0.44, respectively. The findings of this study demonstrate that kSID Lys varies by stage of gestation and SID Lys intake level and that, at least in gilts, a dynamic kSID adjusted for daily intake more adequately reflects biological response and hence allows more precise feeding of pregnant females.

203 Efficiency of SID lysine utilization and maximum SID lysine retention for gilts in early, mid and late gestation

Efficiency of amino acid (AA) use is presumed constant across gestation but may not reflect changes in metabolic demand during gestation nor consider changes in efficiency depending on level of AA intake. Two experiments were conducted to determine efficiency of SID Lys utilization in gilts during early (d 48-52), mid (d 75-79) and late gestation (d 103-107). Each experiment provided 4 isocaloric (3,335 kcal ME/kg) and isoproteic (11.75 % CP) diets containing 4 SID Lys levels (Table 1). Diets were randomly assigned to 45 gilts (PIC 1050, 158.0 ± 8.0 kg at d 39.4 ± 1 of gestation) in Exp. 1 and 27 gilts (PIC 1050, 169.0 ± 7.5 kg at d 41 ± 1 of gestation) in Exp. 2. Dietary indispensable AA were set to meet or exceed 100% of AA:Lys ratios in both experiments. The SID Lys retention was estimated from whole body nitrogen (N) retention balance studies in each period (7 d diet adaptation, 5 d total urine collection and grab fecal sampling) according to the NRC (2012) equations. The relationship between SID Lys intake and SID Lys retention was determined by nonlinear regression models using the CurveExpert Professional software. According to the Hoerl regression model: E(y)=exp(β 0+β 1X)[Xβ2] best-fitting line, maximum efficiency of SID Lys utilization (i.e. g SID Lys retention/g SID Lys intake) was 65%, 57%, and 53% in early, mid and late gestation and occurred at 6.6, 8 and 12 g of SID Lys intake/d, respectively. Maximum SID Lys retention occurred at 8.1 and 9.8 g of SID Lys intake/d for early and mid-gestation. The SID Lys retention did not reach a maximum value in late gestation. These results suggest that efficiency of SID Lys utilization is not constant across gestation and that maximal efficiency occurs at intake below current recommendations.

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373 Efficiency of standardized ileal digestible lysine utilization for whole body protein retention in pregnant gilts and sows during early and mid gestation

NRC (2012) gestating sow model assumes the efficiency of AA use is constant across gestation, which may not reflect changes in metabolic demand during gestation. Efficiency of utilization is determined as the slope of the response to graded levels of test AA. Previous work reported a lack of response to graded Lys [60–90% of NRC (2012) predicted requirement] in early and mid gestation. Therefore, a study was conducted to determine efficiency of SID Lys utilization for whole body protein retention in gilts and sows during early (d 48–52) and mid (d 75–79) gestation. Four isocaloric (3,373 kcal ME/kg) and isoproteic (12.75 % CP) diets containing 40, 50, 60, and 70% of NRC (2012) model-predicted daily SID Lys requirement (10.1 and 9.3 g/d in early and mid gestation, respectively) were randomly assigned to 50 females (PIC 1050; 12 gilts, 21 Parity 1, 17 Parity 2). Dietary indispensable AA contents were set to meet 100–200% of AA:Lys ratios. Whole body nitrogen (N) retention was based on N-balance studies in early and mid gestation (7-d diet adaptation and 5 d total urine collection and grab fecal sampling). Lysine efficiency was determined by simple linear regression using PROC GLM procedure of SAS. Reproductive performance data were analyzed using PROC MIXED procedure of SAS. Reproductive performance of sows (birth weight, born alive, stillborn, and mummies) was not different by parity or diet. Whole body N and SID Lys retention increased linearly (P < 0.0001) with increasing SID Lys intake in early and mid gestation. Efficiency of Lys utilization in early gestation was 0.60, 0.46, and 0.50, and in mid gestation 0.58, 0.44, and 0.48 for gilts, parity 1, and parity 2 sows, respectively. Parity may play a greater role in efficiency of AA use than stage of gestation.