scholarly journals The impact of “super-dosing” phytase in pig diets on growth performance during the nursery and grow-out periods1

2018 ◽  
Vol 3 (1) ◽  
pp. 419-428 ◽  
Author(s):  
Cassie L Holloway ◽  
R Dean Boyd ◽  
Dean Koehler ◽  
Stacie A Gould ◽  
Qingyun Li ◽  
...  

Abstract Previous research indicates that “super-dosing” phytase may improve pig growth performance by improved nutrient use, although the benefits appear to be more consistent in nursery than in grow-out pigs. Therefore, two experiments were conducted to determine if performance could be improved by feeding phytase at super-dosed levels, and whether this response would be different if energy and amino acid (AA) were limiting. Experiment 1 involved 440 weaned pigs (6.27 ± 0.01 kg) in a factorial arrangement of treatments comparing the main effects of diet (positive control [PC] balanced for all nutrients vs. a negative control [NC]: 10% lower standardized ileal digestible (SID) lysine with relative reduction of all other essential AA and 1% reduced fat) and phytase levels (0 vs. 2,500 FTU Quantum Blue 5G phytase/kg). Pigs were assigned to pen according to a randomized complete block design based on body weight (BW). Feed and water were provided ad libitum across four dietary phases: 3 × 1 wk plus 1 × 2 wk. The average daily gain (ADG) and gain to feed ratio (G:F) were improved in the PC relative to the NC (P < 0.05) indicating success in formulating a diet limiting in energy and/or AA. Phytase improved ADG and G:F, regardless of diet composition (P < 0.05). Thus, super-dosing phytase improved nursery pig growth performance, irrespective of diet nutrient adequacy or deficit. Experiment 2 involved 2,200 growing pigs (36.6 ± 0.30 kg) allotted to five treatments: a balanced PC (250 FTU Quantum Blue 5G phytase/kg), an NC (PC with 15% less SID lysine and 1.5% lower net energy [NE]), and three super-dosing phytase treatments applied to the NC totaling 1,000, 1,750, and 2,500 FTU phytase/kg. Feed and water were available ad libitum. At trial completion (approximately 122 kg), the PC pigs were heavier and more efficient than the NC pigs (P < 0.05) indicating success in formulating an NC treatment. Super-dosing phytase had no effect on whole body ADG or average daily feed intake (P > 0.10) but tended to improve G:F and feed energy efficiency (P < 0.10). Super-dosing phytase improved carcass-based feed and feed energy efficiency (P < 0.05) and tended to improve ADG (P < 0.10). Supplying phytase at “super-dosed” levels—above that required to meet the phosphorus requirement—improved growth performance in nursery pigs (6 to 22 kg BW) and provided smaller benefits in grow-finish pigs (37 to 122 kg BW). The improvement during the nursery period was independent of energy and AA levels in the diet.

2021 ◽  
Vol 100 (1) ◽  
Author(s):  
Olufemi Oluwaseun Babatunde ◽  
Olayiwola Adeola

Abstract Two experiments were carried out to determine a time-series effect of phytase on phosphorus (P) utilization in growing and finishing pigs using growth performance, apparent total tract digestibility (ATTD) of nutrients, P excretion, and plasma concentrations of minerals as the response criteria for evaluation. In both experiments, treatments were arranged as a 3 × 4 factorial in a randomized complete block design with 3 corn–soybean meal-based diets including a P-adequate positive control (PC), a low-P negative control (NC; no inorganic P), and NC supplemented with phytase at 1,000 FYT/kg (NC + 1,000); and 4 sampling time points at days 7, 14, 21, and 28 in experiment 1, and days 14, 26, 42, and 55 in experiment 2. In both trials, 96 growing pigs with average body weight (BW) of 19.8 ± 1.16 and 49.8 ± 3.21 kg, respectively, were allocated to the 3 diets with 8 replicates pens (4 barrows and 4 gilts) and 4 pigs per pen. In experiment 1, pigs fed the PC had higher (P < 0.01) BW, average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F) when compared with pigs fed the NC. There was an interaction (P < 0.01) between time and diet on the BW and ADG of pigs while a linear and quadratic increase (P < 0.01) was observed with the ADFI and G:F, respectively, over time. Phytase supplementation improved (P < 0.01) all growth performance responses. Pigs fed the PC had greater (P < 0.01) ATTD of P and Ca than pigs fed the NC. There was no interaction effect on the ATTD of nutrients. Phytase addition improved the ATTD of P and Ca over pigs fed the NC. There was an interaction (P < 0.01) between diet and time on the total and water-soluble P (WSP) excreted. There was a quadratic decrease (P < 0.01) in plasma concentration of Ca in pigs over time. In experiment 2, there was a quadratic increase (P < 0.01) in BW, ADG, and G:F of pigs over time. Similarly, the inclusion of phytase improved (P < 0.05) all growth performance parameters except ADFI. A linear increase (P < 0.05) in the ATTD of DM, P, and Ca occurred over time. Phytase inclusion improved (P < 0.01) the ATTD of P and Ca. Plasma concentrations of P were improved by phytase addition. Phytase supplementation of the NC reduced WSP excretion by 45%, 32%, and 35% over the growing, finishing, and entire grow-finish period, respectively. In conclusion, phytase improves the utilization of P in growing and finishing pigs; however, the magnitude of effect on responses may vary over time.


2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 149-150
Author(s):  
Sydney M Bowman ◽  
Steven T Quantz ◽  
Tom Rehberger ◽  
Kellen Habib ◽  
Kristen Smith ◽  
...  

Abstract Lactobacillus and Bacillus probiotics may serve as an alternative to antibiotics in milk replacer for pre-ruminant calves by altering gastrointestinal microflora to prevent the proliferation of harmful bacteria. However, there are limited studies evaluating their impact on calf growth and efficiency. The objective of this trial was to discover the impact of probiotic-containing milk replacer on pre-ruminating calf growth performance. A total of 44 pre-ruminant calves (50% Angus/50% Holstein, average weight 39.3 kg + 7.5 kg) were fed milk replacer with either no probiotic or 1.25x10^9 colony forming units/head/day of a probiotic blending containing Lactobacillus and two different Bacillus species (Church & Dwight Animal Nutrition (Princeton, NJ). Calves were blocked by age and randomly assigned within block to one of two treatments in a randomized complete block design. Calf was the experimental unit, with 22 calves per treatment. Calf weight and hip height was measured on d 0 and 30 to calculate average daily gain (ADG) and average growth per day. Calves were offered 1.36 kg milk replacer [15% dry matter (DM)] twice daily and up to 0.5 kg starter feed (88% DM) once daily. Refusals were recorded to calculate average daily intake and gain to feed ratio (G:F). Initial weight differed (P = 0.020) between treatments, and was therefore used as a covariate in all response criteria. Calves fed milk replacer with probiotic had greater (P < 0.05) ADG (0.53 vs. 0.42 kg/d, respectively) and G:F (0.50 vs. 0.41, respectively) than those fed the control. There was no evidence (P >0.05) that probiotic inclusion impacted hip height on d 30 or daily intake. In summary, Lactobacillus and Bacillus probiotic inclusion in milk replacer improved calf growth performance without impacting intake. Subsequent research is warranted to elucidate mode of action and evaluate impact relative to an antibiotic-containing positive control.


2021 ◽  
Vol 99 (10) ◽  
Author(s):  
Agbee L Kpogo ◽  
Jismol Jose ◽  
Josiane C Panisson ◽  
Atta K Agyekum ◽  
Bernardo Z Predicala ◽  
...  

Abstract The objective of this project was to determine the impact of feeding growing pigs with high wheat millrun diets supplemented with a multi-carbohydrase enzyme (amylase, cellulase, glucanase, xylanase, and invertase activities) on nutrient digestibility, growth performance, and greenhouse gas (GHG) output (carbon dioxide, CO2; nitrous oxide, N2O; methane, CH4). Three experiments were conducted utilizing six treatments arranged as a 3 × 2 factorial (0%, 15%, or 30% wheat millrun; with or without enzyme) for the digestibility experiment or as a 2 × 2 factorial (0% or 30% wheat millrun; with or without enzyme) for the performance and GHG experiments. The digestibility, performance, and GHG experiments utilized 48 individually housed pigs, 180 pigs housed 5 per pen, or 96 pigs housed 6 per chamber, respectively. Increasing wheat millrun up to 30% in the diet of growing pigs resulted in decreased energy, nitrogen (N) and phosphorus (P) apparent total tract digestibility and net energy content (P < 0.01). Overall, average daily gain (ADG) and gain to feed ratio were reduced in pigs fed wheat millrun (P < 0.05). Enzyme supplementation had minimal effects on the digestibility or performance parameters measured. Feeding diets with 30% millrun did not affect GHG output (CH4: 4.7 and 4.9; N2O: 0.45 and 0.42; CO2: 1,610 and 1,711 mg/s without or with millrun inclusion, respectively; P > 0.78). Enzyme supplementation had no effect on GHG emissions (CH4: 4.5 and 5.1; N2O: 0.46 and 0.42; CO2: 1,808 and 1,513 mg/s without or with enzymes, respectively; P > 0.51). Overall, the carbohydrase enzyme had minimal effects on parameters measured, regardless of wheat millrun inclusion (P > 0.10). Although energy, N and P digestibility, and ADG were reduced, the inclusion of up to 30% wheat millrun in the diet has no effect on GHG emissions from growing pigs (P > 0.10).


2019 ◽  
Vol 97 (Supplement_2) ◽  
pp. 65-66
Author(s):  
Woong B Kwon ◽  
Kevin J Touchette ◽  
Aude Simongiovanni ◽  
Kostas Syriopoulos ◽  
Anna Wessels ◽  
...  

Abstract The hypothesis that excess dietary Leu affects growth performance and metabolism of branched-chain amino acids (BCAA) in growing pigs was tested. Forty barrows (30.0 ± 2.7 kg) were placed in metabolism crates and randomly allotted to 5 diets that contained 100, 150, 200, 250, or 300% of the requirement for standardized ileal digestible Leu. Initial and final body weight of pigs and daily feed provisions were recorded. Urine and fecal samples were collected for 5 d to measure N balance and biological value of diets. At the conclusion of the experiment, blood, brain, liver, and muscle samples were collected and average daily gain (ADG), average daily feed intake (ADFI), and gain to feed ratio (G:F) were calculated. Orthogonal polynomial contrasts were used to determine linear and quadratic effects of increasing Leu in the diets. Results indicated that ADG, ADFI, and G:F decreased (linear, P < 0.05) as dietary Leu increased (Table 1). A trend (linear, P = 0.082) for decreased N retention and decreased (linear, P < 0.05) biological value of protein was also observed. Plasma urea N increased (linear, P < 0.05) and a quadratic reduction (P < 0.05) in plasma serotonin and a linear reduction (P < 0.05) in cerebral serotonin were observed with increasing dietary Leu. Concentrations of BCAA in liver increased (linear, P < 0.001), concentrations of BCAA in muscle decreased (linear, P < 0.05), concentration of α-keto-isovalerate was reduced (linear and quadratic, P < 0.001) in liver, muscle, and serum, and α-keto-β-methylvalerate was reduced (linear and quadratic, P < 0.001) in muscle and serum, whereas α-keto-isocaproate increased (linear, P < 0.05) in liver and muscle, and in serum (linear and quadratic, P < 0.001) with increasing dietary Leu. In conclusion, excess dietary Leu reduced growth performance and cerebral serotonin and tended to reduce protein synthesis.


2020 ◽  
Vol 4 (3) ◽  
Author(s):  
Zachary K Smith ◽  
Kip Karges ◽  
Angel Aguilar

Abstract The objective of this experiment was to evaluate the influence of an active live yeast direct-fed microbial (DFM) product on receiving and backgrounding period growth performance and efficiency of dietary net energy (NE) utilization in low health risk beef steers. Maine-Anjou × Angus steers (n = 199; body weight [BW] = 252 ± 32.1 kg) were received from two sources at the Ruminant Nutrition Center in Brookings, SD, in November 2019 and used in a 77-d feedlot receiving and backgrounding experiment. Steers were provided access to long-stem hay and ad libitum water upon arrival. Steers were weighed, vaccinated for respiratory pathogens (source 2 only): infectious bovine rhinotracheitis, bovine viral diarrhea types 1 and 2, parainfluenza-3 virus, and bovine respiratory syncytial virus (Bovi-Shield Gold 5, Zoetis, Parsippany, NJ) vaccinated for clostridial species (Ultrabac 7/Somubac, Zoetis) and pour-on moxidectin (Cydectin, Bayer, Shawnee Mission, KS). Steers (n = 176 steers; initial unshrunk BW = 235 ± 27.6 kg) were allotted to pens (n = 20 pens; 10 pens per treatment; eight or nine steers per pen). Diets were based upon corn silage, dry-rolled corn, and dried distillers grains; dietary treatments were 1) no DFM (CON) and 2) DFM (Levucell SC, Advantage Titan, CNCM l-1077), fed at 10 g/steer/d providing 8 × 109 CFU of active live yeast to each steer daily (DFM). Initial BW was the average of day −1 and day 1 BW (n = 176 steers; initial BW = 253 ± 27.6 kg). On day 21, steers received a 200-mg progesterone and 20-mg estradiol benzoate implant. Data were analyzed from day 1 to 47 (receiving period), day 48 to 77, and from day 1 to 77 as a randomized complete block design; pen served as the experimental unit for all analyses. On day 47 of the experiment, DFM had greater BW (P = 0.01) by 0.9% and average daily gain (ADG; P = 0.01) by 4.2% and gain-to-feed ratio (G:F) tended (P = 0.13) to be 2.8% greater. Day 77 BW did not differ (P = 0.60), cumulative (days 1–77): ADG (P = 0.47), dry matter intake (P = 0.66), and G:F (P = 0.56) were similar. Yeast inclusion had no appreciable influence on performance-based dietary NE utilization or the ratio of observed/expected dietary NE (P ≥ 0.59). In low health risk steers, DFM improved performance during the feedlot receiving period. However, no improvements for DFM were detected for cumulative performance from day 1 to 77. The confirmation of yeast counts indicated the CFU to be above the expected level at the start of the trial but was found below expected level at the end of the trial. This may explain differences during the initial 47 d compared to cumulative growth performance results.


2020 ◽  
Vol 98 (1) ◽  
Author(s):  
M Shamimul Hasan ◽  
Mark A Crenshaw ◽  
Shengfa F Liao

Abstract Lysine is the first limiting amino acid (AA) in typical swine diets. Our previous research showed that dietary lysine restriction compromised the growth performance of late-stage finishing pigs, which was associated with the changes in plasma concentrations of nutrient metabolites and hormone insulin-like growth factor 1 (IGF-1). This study was conducted to investigate how dietary lysine restriction affects the plasma concentrations of selected metabolites and three anabolic hormones in growing pigs. Twelve individually penned young barrows (Yorkshire × Landrace; 22.6 ± 2.04 kg) were randomly assigned to two dietary treatments (n = 6). Two corn and soybean meal based diets were formulated to contain 0.65% and 0.98% standardized ileal digestible lysine as a lysine-deficient (LDD) and a lysine-adequate (LAD) diets, respectively. During the 8-week feeding trial, pigs had ad libitum access to water and their respective diets, and the growth performance parameters including average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F) were determined. At the end of the trial, jugular vein blood was collected for plasma preparation. The plasma concentrations of free AA and six metabolites were analyzed with the established chemical methods, and the hormone concentrations were analyzed with the commercial ELISA kits. Data were analyzed with Student’s t-test. The ADG of LDD pigs was lower (P &lt; 0.01) than that of LAD pigs, and so was the G:F (P &lt; 0.05) since there was no difference in the ADFI between the two groups of pigs. In terms of free AA, the plasma concentrations of lysine, methionine, leucine, and tyrosine were lower (P &lt; 0.05), while that of β-alanine was higher (P &lt; 0.01), in the LDD pigs. The total plasma protein concentration was lower (P &lt; 0.02) in the LDD pigs, whereas no differences were observed for the other metabolites between the two groups. No differences were observed in the plasma concentrations of growth hormone (GF), insulin, and IGF-1 between the two groups as well. These results indicate that the lack of lysine as a protein building block must be the primary reason for a reduced body protein synthesis and, consequently, the compromised G:F ratio and ADG. The changes in the plasma concentrations of total protein and four AA suggest that the compromised growth performance might be associated with some cell signaling and metabolic pathways that may not involve the GH/IGF-1 axis.


2020 ◽  
Vol 60 (4) ◽  
pp. 535
Author(s):  
F. A. S. Silva ◽  
S. C. Valadares Filho ◽  
L. A. Godoi ◽  
B. C. Silva ◽  
M. V. C. Pacheco ◽  
...  

Restricted-feeding may be a useful management tool available to reduce environmental impact in feedlots. Therefore, the objectives of the present study were to determine the effects of the duration of restricted-feeding on nitrogen (N) and phosphorus (P) excretion, growth performance and carcass characteristics of finishing steers. Twenty-five Holstein × Zebu steers (average initial bodyweight (BW) = 319 ± 16.2 kg; age = 19 ± 1 months) were used. Five steers were slaughtered to provide baseline empty BW (EBW) and empty body composition at Day 0. The remaining steers were randomly allotted to four groups of five steers, which were restricted to 85% ad libitum feed intake for either 0 (R0), 28 (R28), 42 (R42) or 84 (R84) days of an 84-day finishing period. All steers were fed a diet of 40% corn silage and 60% concentrate (DM basis) for 84 days. Total excretion of faeces and urine were collected during two periods: Days 25 to 27 (period 1) and Days 73 to 75 (period 2). The DM intake, average daily gain (ADG) and gain-to-feed ratio (G:F) were evaluated in three blocks, Days 0 to 28, Days 28 to 42 and Days 42 to 84. As expected, DM, N and P intakes were greater (P &lt; 0.05) for R0 steers than R28, R42 and R84 steers when steers in R28, R42 and R84 treatments were restricted. When transitioned to ad libitum feeding, R28 and R42 steers had similar (P &gt; 0.05) DM, N and P intakes compared with R0 steers. Faecal N and urinary P excretions did not differ (P ≥ 0.40) among restricted and ad libitum-fed steers in either period evaluated. However, greater (P &lt; 0.05) faecal P excretions were observed in steers fed ad libitum intake in period 2 (R0). Phosphorus retention in period 2, and whole-body N retention were greatest (P &lt; 0.05) in steers fed R28 and least (P &lt; 0.05) in steers fed R84, steers fed R0 and steers fed R42 were intermediate and not different (P &gt; 0.05). Final BW, overall ADG, G:F and carcass characteristics were not affected (P ≥ 0.11) by treatments. Restricted-feeding Holstein × Zebu steers to 85% of ad libitum intake for 84 days in the feedlot reduced DM intake and P excretion, without impairing steer growth performance or carcass characteristics. Nevertheless, it is important to highlight that the small sample size was one limitation of this present experiment.


2021 ◽  
Vol 99 (Supplement_1) ◽  
pp. 198-199
Author(s):  
Hansol Kim ◽  
Eunjeong Jang ◽  
Sang Yun Ji ◽  
Beob Gyun G Kim

Abstract Sufficient supply of dietary phosphorus (P) is critical for maximizing muscle and bone growth of pigs. The objective was to compare standardized total tract digestible (STTD) P requirements of growing pigs determined in the experiments and those estimated using modeling approach. Fifty-two experiments in the literature that empirically determined P requirements of pigs were employed. The basis for the determination of P requirements were growth performance (average daily gain or gain to feed ratio; n = 34) and bone development (n = 23). Based on the STTD P in the feed ingredients provided in NRC (2012) and ingredient composition used in the experiments, P requirements presented as total P, available P, and true total tract digestible P were converted to STTD P requirements. To obtain STTD P requirements (g/d) suggested by NRC (2012) for grow-finishing pigs (body weight &gt; 20 kg), mean body weight and sex indicated in the experiments were input into the NRC model. The statistical model for comparing the empirical data and the NRC requirements included the basis for determining P requirements in the experiments as a fixed variable and body weight as a random variable. To quantify the deviations between NRC STTD P requirement estimates and empirically determined STTD P requirements, mean percentage difference was calculated. The STTD P requirements empirically determined based on growth performance were greater than the NRC STTD P requirement estimates (5.89 vs. 4.61 g/d, SEM = 0.27; P &lt; 0.001). Moreover, the bone development-based STTD P requirements were greater than the NRC STTD P requirement estimates (6.63 vs. 4.46 g/d, SEM = 0.42; P &lt; 0.001). In conclusion, the standardized total tract digestible P requirements suggested by the NRC are less than the experimentally determined requirements.


2020 ◽  
Vol 4 (2) ◽  
pp. 694-707
Author(s):  
Henrique S Cemin ◽  
Mike D Tokach ◽  
Steve S Dritz ◽  
Jason C Woodworth ◽  
Joel M DeRouchey ◽  
...  

Abstract Four experiments were conducted to determine the effects of increasing soybean meal (SBM) level in diets with or without 25% distillers dried grains with solubles (DDGS) on growth performance of nursery pigs raised in university or commercial facilities. Treatments were arranged in a 2 × 3 factorial with main effects of SBM (27.5%, 32.5%, or 37.5% of the diet) and DDGS (0% or 25% of the diet). A total of 296, 2,502, 4,118, and 711 pigs with initial body weight (BW) of 10.6, 11.7, 12.5, and 12.3 kg were used in Exp. 1, 2, 3, and 4, respectively. There were 10, 16, 13, and 12 replicates per treatment in Exp. 1, 2, 3, and 4, respectively. After weaning, pigs were fed common diets for approximately 21 d. Then, pens of pigs were assigned to treatments in a randomized complete block design with BW as the blocking factor and experimental diets were fed for 21 d. Pigs were weighed and feed disappearance measured to calculate average daily gain (ADG), average daily feed intake (ADFI), gain-to-feed ratio (G:F), and caloric efficiency (CE). Data were analyzed using the GLIMMIX procedure of SAS with block as a random effect and treatment as a fixed effect. Single degree-of-freedom contrasts were constructed to test the linear and quadratic effects of increasing SBM and their interactions with DDGS. Pigs used in all experiments did not undergo major health challenges during the experimental period and due to the low number of mortality and cull events, statistical analysis was not performed on these variables. The average cull rate was 0.7%, 0.5%, 0.2%, and 0%, and the mortality rate was 0.7%, 0.3%, 0.4%, and 0% in Exp. 1–4, respectively. There were interactions (P ≤ 0.039) between SBM and DDGS for G:F and CE in Exp. 2 and for ADG and ADFI in Exp. 3. These were mostly driven by increasing SBM negatively affecting performance in a greater magnitude when diets contained DDGS compared to diets without DDGS. The main effects of DDGS and SBM were more consistently observed across experiments. Pigs fed diets with 25% DDGS had decreased (P ≤ 0.001) ADG and ADFI in all experiments, as well as poorer (P ≤ 0.028) G:F and CE except for Exp. 3. Feeding increasing amounts of SBM generally did not result in any major impact in ADG but consistently improved (linear, P ≤ 0.078) G:F and CE across experiments.


2020 ◽  
Vol 98 (10) ◽  
Author(s):  
Spenser L Becker ◽  
Stacie A Gould ◽  
Amy L Petry ◽  
Leah M Kellesvig ◽  
John F Patience

Abstract The objective of this experiment was to evaluate the growth performance and bone mineral content (BMC) of nursery pigs in response to increasing total calcium (Ca) to available phosphorus (aP) ratios in diets containing phytase (250 FTU/kg; Natuphos E, BASF, Florham Park, NJ). A total of 480 nursery pigs (body weight (BW) = 5.7 ± 0.6 kg) with 10 pigs per pen and 7 pens per treatment (6 pens fed 2.75:1 diet) were allotted to seven treatments consisting of increasing ratios of calcium to available phosphorus (Ca:aP): 1.25, 1.50, 1.75, 2.00, 2.25, 2.50, and 2.75. From day −7 to 0, pigs were fed a common diet. They were then fed the treatment diets during two experimental phases from day 1 to 14 and 15 to 28, respectively. Available P was formulated to 0.33% and 0.27% (approximately 90% of requirement) in dietary phases 1 and 2, respectively. BW, average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F) were determined. BMC of the femur was measured on day 28 on one pig per pen using dual x-ray absorptiometry. Data were analyzed as a linear mixed model using PROC MIXED (SAS, 9.3). Orthogonal polynomial contrasts were used to determine the linear and quadratic effects of increasing the Ca:aP. Over the 28-d experimental period, increasing Ca:aP resulted in a linear decrease in ADG (353, 338, 328, 304, 317, 291, and 280 g/d; P &lt; 0.01), ADFI (539, 528, 528, 500, 533, 512, and 489 g/d; P &lt; 0.05), and G:F (0.68, 0.66, 0.64, 0.62, 0.61, 0.59, and 0.58; P &lt; 0.01). Increasing Ca:aP also resulted in decreased BW on days 14 and 28 (P &lt; 0.01). The BMC of the femur decreased with increasing Ca:aP (6.2, 6.3, 5.7, 5.9, 5.5, 5.6, and 5.3 g; P &lt; 0.05). Regression analysis explained the impact of Ca:aP as follows on ADG (ADG [g/d] = 339 − 36x; r2 = 0.81), G:F (G:F = 0.61 – 0.03x; r2 = 0.72), and BMC (BMC [g] = 6.4 – 0.27x; r2 = 0.43), where x is the Ca:aP. In conclusion, all outcomes indicated that any level of calcium above the minimum used in this experiment impaired growth performance and skeletal development. Further research using even lower levels of dietary Ca is warranted.


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