scholarly journals Bedding Application to Feedlot Steers: Influence on Growth Performance, Estimated Maintenance Coefficient, Carcass Characteristics, and Circulating Metabolites in Beef Steers

Animals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1766
Author(s):  
Dathan Thomas Smerchek ◽  
Zachary Kidd Smith
Keyword(s):  
Growth Performance ◽  
Serum Insulin ◽  
Block Design ◽  
Average Daily Gain ◽  
Beef Steers ◽  
Feedlot Steers ◽  
Maintenance Coefficient ◽  
Randomized Complete Block Design ◽  
Red Angus ◽  
Daily Gain

Two randomized complete block design experiments were conducted to evaluate the effect of bedding use in confined beef steers. Experiment 1 used Simmental × Angus steers (n = 240; initial body weight (BW) = 365 ± 22.5 kg). Experiment 2 used newly weaned Charolais × Red Angus steers (n = 162; initial BW = 278 ± 13.4 kg). Steers were allotted to one of two treatments: (1) no bedding (NO), or (2) 1.8 kg (Experiment 1) or 1.0 kg (Experiment 2) of wheat straw (as-is basis) bedding/steer·d−1 (BED). In Experiment 1, applying bedding improved (p ≤ 0.01) dry matter intake (DMI), kg of gain to kg of feed (G:F), and average daily gain (ADG). Bedding reduced (p = 0.01) the estimated maintenance coefficient (MQ). Dressing percentage, rib fat, marbling, and yield grade were increased (p ≤ 0.03) in NO. Bedding resulted in an increase (p = 0.01) in serum insulin-like growth factor I (IGF-I). In Experiment 2, a tendency (p = 0.06) for increased DMI for NO was noted. Bedding improved G:F (p = 0.01). MQ was elevated (p = 0.03) for NO and NO had an increase (p = 0.02) in serum concentration of urea-N (SUN). An increase (p = 0.01) in serum non-esterified fatty acid was noted for NO. These data indicate that bedding application should be considered to improve growth performance and feed efficiency by reducing maintenance energy requirements in beef steers during the feedlot receiving and finishing phase.

scholarly journals 450 Late-Breaking: Effects of bedding on feedlot receiving phase growth performance in beef steers during the winter in eastern South Dakota

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 141-142
Author(s):  
Dathan Smerchek ◽  
Zachary K Smith
Keyword(s):  
Metabolic Rate ◽  
South Dakota ◽  
Growth Performance ◽  
Block Design ◽  
Average Daily Gain ◽  
Experimental Unit ◽  
Beef Steers ◽  
Phase Growth ◽  
Randomized Complete Block Design ◽  
Daily Gain

Abstract Two-hundred and forty English × Continental beef steers (initial BW=365 kg [SD 22.5]) were used in a randomized complete block design to evaluate the effects of bedding application during a 36 d feedlot receiving phase on growth performance and efficiency during winter. Steers were allotted to 30 pens (n = 8 steers/pen) at the Ruminant Nutrition Center in Brookings, SD and pens were assigned to 1 of 2 treatments: 1) No bedding applied (NO) or 2) 1.8 kg (as-is basis) of wheat straw bedding/steer/d (BED). Due to the logistics of acquiring, weighing, and timely feeding of steers, the first 9 pen replicates began on test 14 d prior (begin: January 15, 2019 and end: February 20, 2019) to the last 6 pen replicates (begin: January 29, 2019 and end: March 6, 2019). Pen was the experimental unit; an α of 0.05 determined significance. Daily ambient temperature (n = 50) averaged -14.7°C [SD 5.63] and wind-chill (n = 50) averaged -17.7°C [SD 6.40]. Initial BW (365 vs. 365 ± 0.5 kg) and dry matter intake (8.19 vs. 8.22 ± 0.047 kg) did not differ (P ≥ 0.57) between NO and BED. End BW was greater for BED (P = 0.01; 419 vs. 402 ± 1.09 kg) compared to NO. Steers from BED had increased average daily gain (P = 0.01) by 48.0% and gain:feed (P = 0.01) by 49.2% over NO. Using tabular ingredient energy values and observed steer performance shrunk 4%, relative adjustments to metabolic rate were calculated. Estimated metabolic rate was elevated (P = 0.01) for NO (0.146 vs. 0.104 ± 0.0032 Mcal/BW0.75, kg). Bedding improves feedlot receiving phase growth and efficiency in eastern South Dakota during the winter. Under the environmental conditions of this experiment, steers have a 40.4% increased metabolic rate when bedding is not used and steers in bedded pens had a 35.1% increase in metabolic rate compared to (0.077 Mcal/BW0.75, kg).

scholarly journals Increasing hay inclusion in silage-based receiving diets and its effects on performance and energy utilization in newly weaned beef steers

2020 ◽  
Vol 4 (2) ◽  
pp. 848-853
Author(s):  
Dathan T Smerchek ◽  
Elizabeth M Buckhaus ◽  
Katie D Miller ◽  
Zachary K Smith
Keyword(s):  
Growth Performance ◽  
Block Design ◽  
Corn Silage ◽  
Energy Utilization ◽  
Experimental Unit ◽  
Net Energy ◽  
Beef Steers ◽  
Linear Effect ◽  
Randomized Complete Block Design ◽  
Red Angus

Abstract The influence of grass hay (GH) inclusion in replacement of corn silage in receiving diets on growth performance and dietary net energy (NE) utilization was evaluated in newly weaned beef steers (n = 162 Charolais-Red Angus cross steers; initial body weight [BW] = 278 ± 13.4 kg). Treatments were (DM basis): 1) 0% GH, 2) 10% GH, or 3) 20% GH inclusion in replacement of corn silage in receiving diets fed to newly weaned beef steers for 56 d. The study was conducted from October to December of 2019. Data were analyzed as randomized complete block design with pen serving as the experimental unit for all analyses. Increasing dietary inclusion of hay had no influence (P ≥ 0.11) on final BW, ADG, gain:feed or observed/expected dietary NEM and NEG, observed/expected dry matter intake (DMI), or observed/expected ADG. GH inclusion increased (linear effect, P = 0.01) DMI. Observed DMI for all treatments was approximately 15% to 17% less than anticipated based upon steer growth performance and tabular NE values. Evaluation of observed/expected ADG was 31% to 37% greater than expected for the steers in the present study. Particles less than 4 mm increased (linear effect, P = 0.01) and greater than 4 mm decreased (linear effect, P = 0.01) as GH replaced corn silage in the receiving diet. As the proportion of particles greater than 4 mm increased, cumulative ADG was decreased. These data indicate that GH should be considered in corn silage-based receiving diets to improve DMI. In high-risk calves, improved DMI could result in a lesser incidence of morbidity, although no morbidity was observed in any steers from the present study.

scholarly journals 162 Effects of bedding application on feedlot receiving phase growth performance and estimated maintenance requirement in newly weaned beef steers

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 128-129
Author(s):  
Dathan Smerchek ◽  
Zachary K Smith
Keyword(s):  
Body Weight ◽  
Growth Performance ◽  
Block Design ◽  
Average Daily Gain ◽  
Concrete Surface ◽  
Study Data ◽  
Experimental Unit ◽  
Beef Steers ◽  
Final Body Weight ◽  
Red Angus

Abstract The effect of bedding application on growth performance and estimated maintenance energy requirements during the feedlot receiving phase was evaluated in newly weaned beef steers (n = 162 Charolais-Red Angus cross steers; initial un-shrunk body weight [BW] = 278 ± 13.4 kg). Steers were housed in 18 concrete surface pens (n = 9 steers/pen) measuring 7.62 × 7.62 m at the Ruminant Nutrition Center in Brookings, SD. A corn silage based receiving diet was fed that contained approximately 1.74 Mcal/kg of NEm, approximately 1.12 Mcal/kg of NEg, and monensin sodium at 27.6 g/T. Pens were assigned to one of two treatments: 1) no bedding (NO), or 2) 1.0 kg (as-is basis) of wheat straw bedding/steer/d (BED). The study was conducted from October to December of 2019. Daily ambient temperature (n = 56) averaged -3.0°C [SD 5.5] and windchill averaged -5.1°C [SD 6.1] during the course of the study. Data were analyzed using the GLIMMIX procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) as a randomized complete block design with pen serving as the experimental unit. An α of 0.05 determined significance and tendencies were declared from 0.06 to 0.10. At study initiation, initial un-shrunk body weight did not differ (P = 0.69) between treatments. Bedding application did not influence (P ≥ 0.66) final body weight (shrunk 4%) or average daily gain. Dry matter intake tended to increase (P = 0.06) by 3.8% in NO compared to BED. Gain to feed was increased (P = 0.01) by 5.6% in BED compared to NO. Maintenance coefficient (MQ) was elevated (P = 0.03) 18.9% for NO compared to BED. These data indicate that bedding application improved feed efficiency and reduced estimated MQ in beef steers during the feedlot receiving phase.

PSVI-4 Effect of phytase on mineral digestibility and growth performance of pigs fed diets with pharmacological levels of Zn

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 400-401
Author(s):  
Charmaine D Espinosa ◽  
Deepak Velayudhan ◽  
Yueming Dersjant-Li ◽  
Janet Remus ◽  
Hans-Henrik H Stein
Keyword(s):  
Growth Performance ◽  
Block Design ◽  
Average Daily Gain ◽  
Positive Control ◽  
Negative Control ◽  
Metabolizable Energy ◽  
Randomized Complete Block Design ◽  
Quadratic Effects ◽  
Digestible Amino Acids ◽  
Daily Gain

Abstract An experiment was conducted to test the hypothesis that increasing levels of phytase increases mineral digestibility and growth performance of pigs fed diets with 3,000 mg/kg of Zn. A positive control (PC) diet that met nutrient requirements and a negative control (NC) diet that was deficient in total Ca (-0.16%), digestible P (-0.14%), metabolizable energy (-50 kcal/kg), and digestible amino acids (-0.02%) were formulated. Eight additional diets were formulated by adding 500, 1,000, 1,500, or 2,000 phytase units/kg of a novel bacterial 6-phytase (PhyG) or a commercial Buttiauxella phytase (PhyB) to the NC diet. A randomized complete block design with 400 weanling pigs (5.82 ± 0.70 kg), 10 diets, 4 pigs per pen, and 10 replicate pens per diet was used. Pigs were fed the experimental diets for 28 d. Fecal samples were collected from 1 pig per pen on d 26 to 28. Linear and quadratic effects of PhyG and PhyB were determined using polynomial contrast statements. Contrast statements were used to compare effects of PC diet with NC diet, and to compare effects of PhyG diets with PhyB diets. Overall, pigs fed the NC diet had reduced growth performance (P < 0.05) compared with pigs fed the NC diet (Table 1). Linear (P < 0.01) and quadratic (P < 0.05) increases in overall average daily gain and average daily feed intake of pigs were observed as dietary concentrations of PhyG or PhyB increased. Increasing levels of PhyG or PhyB linearly increased (P < 0.01) the apparent total tract digestibility (ATTD) of P and Ca. PhyG increased ATTD of P more (P < 0.05) than PhyB. In conclusion, both phytases are effective in increasing mineral digestibility and growth performance in pigs fed diets with pharmacological levels of Zn; however, PhyG improved P digestibility more than PhyB.

scholarly journals 198 Effects of different dietary standardized ileal digestible lysine specifications on growth performance of grow-finish pigs

2020 ◽  
Vol 98 (Supplement_3) ◽  
pp. 56-57
Author(s):  
Ning Lu ◽  
Carine Vier ◽  
Wayne Cast ◽  
Uislei Orlando ◽  
Dan Hamilton ◽  
...  
Keyword(s):  
Growth Performance ◽  
Feed Intake ◽  
Block Design ◽  
Average Daily Gain ◽  
Experimental Unit ◽  
Randomized Complete Block Design ◽  
Similar Growth ◽  
Daily Gain ◽  
Growth Trial ◽  
Standardized Ileal Digestible Lysine

Abstract The objective was to determine the effects of different standardized ileal digestible (SID) lysine (Lys) specifications on performance of grow-finish pigs. A total of 2,106 pigs (PIC 359×Camborough, initially 22.0±0.43 kg) were used in a 72-d growth trial with 27 pigs per pen and 13 pens per treatment in a randomized complete block design. Pigs were fed corn-soybean-meal-based diets in three phases from 22-41, 41-62, and 62-91 kg body weight (BW). Treatments consisted of low (L) or high (H) SID Lys in each phase: LLL (1.05, 0.88, and 0.73%); LLH (1.05, 0.88, and 0.82%); LHH (1.05, 0.99, and 0.82%); HLL (1.18, 0.88, and 0.73%); HHL (1.18, 0.99, and 0.73%); and HHH (1.18, 0.99, and 0.82%). Lysine curves from PIC2008 and PIC2016 nutrient specification manuals were used to estimate SID Lys levels for L or H diets, respectively. Data were analyzed using generalized linear mixed models with pen as the experimental unit. From 22-41 kg, feeding high Lys improved (P< 0.10) average daily gain (ADG), feed efficiency (G:F), and final BW compared to low Lys. From 22-62 kg, feeding HH Lys increased (P< 0.05) ADG compared feeding LL or HL Lys. Pigs fed HH Lys or LH Lys had improved (P< 0.05) G:F compared to those fed LL Lys. Pigs fed LH or HH Lys had greater (P< 0.05) final BW compared to pigs fed HL. Pigs fed HH Lys had greater (P< 0.05) feed intake compared to pigs fed HL. From 22-91 kg, there was no evidence for differences in ADG, feed intake, G:F, or final BW. In summary, pigs fed 1.18% SID Lys had improved ADG, G:F, and final BW compared to pigs fed 1.05% SID Lys from 22-41 kg. Feeding a range of Lys specifications resulted in similar growth performance from 22-91 kg.

scholarly journals PSX-36 Effect of forage neutral digestion fiber level for feedlot lambs: growth performance

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 451-451
Author(s):  
Josue Godinez ◽  
Alejandro Plascencia ◽  
Francisco Castrejón-Pineda ◽  
Juan Carlos Ramírez-Orejel ◽  
Luis Corona
Keyword(s):  
Growth Performance ◽  
Block Design ◽  
Average Daily Gain ◽  
Neutral Detergent Fiber ◽  
Energy Utilization ◽  
Net Energy ◽  
Finishing Diets ◽  
Feedlot Lambs ◽  
Sheep Production ◽  
Daily Gain

Abstract The main objective of sheep production in Mexico is the production of meat. The greater demand of sheep meat in relation to the offer generated an attractive market that favored the intensification of the fattening, to take advantage of the growth of lambs in its different stages, and reduce the days of fattening. Thirty-two lambs (28.50± 2.67 kg initial shrunk weight) were used in a 63-day feeding trial (4 pens per treatment, randomized complete block design) to evaluate neutral detergent fiber level (4, 8, 12, and 16% diet DM) on finishing-phase growth performance, dietary energetics and carcass traits. Dietary treatments consisted of a cracked corn-based diet in which the NDF concentration of diet was manipulated by replacing cracked corn grain by corn stubble. Dietary NDF level showed a quadratic response on average daily gain and gain efficiency, being those maximal at 8% NDF level. Lambs fed 8% NDF level tended (P = 0.07) to shown greater dry matter intake than others treatments. The ratio of observed-to-expected dietary net energy was 3% lower (0.97) for lambs fed 4% NDF, while the ratio of observed-to-expected dietary net energy for lambs that were fed with 8, 16 and 16% NDF were closely to 1.00. Hot carcass weight (HCW) and dressing percentage (DP) were maximal for the lambs fed 8% NDF level (quadratic effect, P ≤ 0.03); beyond this level, HCW and DP percentage decreased as NDF level increased. Using corn stubble as source of NDF in growing-finishing diets for lambs, the optimal NDF level was 8%. Fiber level below 8% decreases net energy utilization, and this may be cause by digestive disorders. Fiber levels upper 8% did not affect energy utilization; however, affect negatively average daily gain, feed efficiency and carcass characteristics by effect of high levels of fiber on energy dilution of diet.

scholarly journals Effects of increasing dietary level of a commercial liquid supplement on growth performance and carcass characteristics in feedlot steers

2018 ◽  
Vol 2 (2) ◽  
pp. 216-222
Author(s):  
Tara L Felix ◽  
Chloe J Long ◽  
Madeline R Stierwalt ◽  
Pedro H V Carvalho ◽  
Howard M Blalock
Keyword(s):  
Growth Performance ◽  
Block Design ◽  
Carcass Characteristics ◽  
Feedlot Cattle ◽  
Corn Silage ◽  
Distillers Grains ◽  
Dietary Level ◽  
Distillers Grains With Solubles ◽  
Feedlot Steers ◽  
Randomized Complete Block Design

Abstract Feeding cattle liquid supplements has become increasingly popular in the feedlot industry; however, optimal inclusion of liquid supplements in feedlot cattle diets is not known. The objectives of this study were to determine the optimal inclusion of liquid supplementation to maximize growth performance and improve carcass characteristics, as well as estimate the energy value of liquid supplementation when used as a direct corn replacement, for feedlot steers fed a concentrate-based diet. Two hundred and eighty steer calves were stratified by BW into light (BW = 208 ± 9 kg; n = 24) and heavy (BW = 275 ± 8 kg; n = 16) pens. Pens within BW block were randomly assigned to 1 of 4 supplements: 1) dry at 4.5% inclusion (0LIQ), 2) liquid (a proprietary blend from Quality Liquid Feeds; Dodgeville, WI) at 4.5% inclusion (4.5LIQ), 3) liquid at 9% inclusion (9LIQ), or 4) liquid at 13.5% inclusion (13.5LIQ). The remainder of the diet was 47.5% to 55.5% dry rolled corn, 20% corn silage, and 20% modified wet distillers grains with solubles (DM basis). Data were analyzed as a randomized complete block design and linear and quadratic were examined to determine effects of increasing dietary concentrations of liquid. Steers fed 4.5LIQ and 9LIQ had greater (quadratic; P ≤ 0.05) final BW, HCW, and NEm and NEg, and less DMI as a percent of BW compared to steers fed 13.5LIQ. Steers fed 0LIQ were intermediate and not different from other treatments. However, ADG and total BW gain did not differ (P ≥ 0.15) among treatments. Despite the lack of treatment effect on live measures of gain, feeding steers 4.5LIQ and 9LIQ resulted in greater carcass ADG (quadratic; P = 0.03), total carcass gain (quadratic; P = 0.04), and more efficient carcass gain (quadratic; P ≤ 0.01) compared to carcasses from steers fed 13.5LIQ. Feeding steers a liquid supplement at 9% of the diet, DM allowed for the greatest final BW and ADG in this study; however, there was no benefit of increasing liquid to 13.5%.

scholarly journals Nutrient Yield of Brown Hemp and Its Utilization as Protein Source in Concentrate on Brahman×Thai-Native Cattle Performances

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Supreena Srisaikham ◽  
◽  
Pipat Lounglawan ◽  
Keyword(s):  
Animal Feed ◽  
Block Design ◽  
Average Daily Gain ◽  
Nutrient Composition ◽  
Feed Resources ◽  
Significant Difference ◽  
Randomized Complete Block Design ◽  
Nutrient Yield ◽  
Native Cattle ◽  
Daily Gain

Two experiments were conducted to evaluate the effects of cutting ages and height on the nutrient composition and yield of brown hemp (BH) in concentrate diets on Brahman×Thai-Native cattle performances. The first experiment was to determine the effects of cutting ages (30, 40 and 50 days) and height (30, 40 and 50 cm) on the nutrient composition and yield of BH. The experiment was a 3×3 factorial arrangement in a randomized complete block design. This study clearly showed that cutting ages at 50 days had a greater effect on the nutrient composition and yield than at 30 and 40 days, but the cutting heights did not reveal any significant differences in yield. However, the BH cutting for animal feed before plowing, besides improving the soil for green manure, also benefited feed resources. The second experiment was to study the effects of BH meal (BHM) in concentrate on Brahman×Thai-Native cattle performances. Twelve cattle, averaging 252 ± 18 kg body weight and at ages of 16-18 months were stratified randomly and assigned to one of the three feeding treatments. Cattle were fed BHM in different ratios: the treatments were 0, 10, and 20% of BHM, respectively. There were no significant differences in the dry matter intake among the treatments of 0, 10 and 20% of BHM in concentrate rations. For average daily gain, the minimum response observed was a significant difference at the highest level of 20% of BHM. Therefore, 10% of BHM can be used in the concentrate rations for beef cattle.

scholarly journals Supplementation of grazing beef cattle with narasin

2020 ◽  
Vol 55 ◽  
Author(s):  
Luiz Guilherme Mezzena Gobato ◽  
Daniel Montanher Polizel ◽  
Marcos Vinícius de Castro Ferraz Júnior ◽  
Alexandre Arantes Miszura ◽  
José Paulo Roman Barroso ◽  
...  
Keyword(s):  
Body Weight ◽  
Block Design ◽  
Average Daily Gain ◽  
Initial Body Weight ◽  
Mineral Supplement ◽  
Protein Supplements ◽  
Randomized Complete Block Design ◽  
Daily Gain ◽  
Positive Effect ◽  
Supplement Intake

Abstract: The objective of this work was to evaluate the effect of narasin inclusion in mineral and protein supplements on the performance and supplement intake of grazing beef yearlings. One hundred and fifty Nellore yearlings with 17.0±0.06 months of age and 219.7±1.62 kg initial body weight (BW) were allocated into 30 experimental units (EUs), with five animals each. The EUs were assigned to 16 paddocks, which were continuously stocked for 28 days, followed by 28 days of rest. A randomized complete block design was used. The experiment lasted 140 days, divided into five periods of 28 days each. The assessed treatments were: control mineral supplement (CON); CON + 1,800 (N1800) or 2,750 (N2750) mg narasin per kilogram of supplement; and protein mineral supplement (PROT) or PROT + 360 mg narasin per kilogram of supplement (PROT 360). The inclusion of narasin in the mineral supplement increased average daily gain (ADG) in the first period and decreased supplement intake in the first, second, and third periods, when compared with the CON treatment. The ADG and supplement intake were similar between the N1800 and N2750 treatments. Narasin has a positive effect on ADG up to 28 days of supplementation and controls mineral supplement intake, without compromising this gain.

scholarly journals Calcium to phosphorus ratio requirement of 26- to 127-kg pigs fed diets with or without phytase1,2

2019 ◽  
Vol 97 (10) ◽  
pp. 4041-4052 ◽  
Author(s):  
Carine M Vier ◽  
Steve S Dritz ◽  
Mike D Tokach ◽  
Joel M DeRouchey ◽  
Robert D Goodband ◽  
...  
Keyword(s):  
Block Design ◽  
Average Daily Gain ◽  
Consistent Estimate ◽  
Ratio Requirement ◽  
Carcass Yield ◽  
Bone Ash ◽  
Randomized Complete Block Design ◽  
Daily Gain ◽  
Ca:P Ratio ◽  
The Ideal

Abstract Two experiments were conducted to determine the effects of calcium to phosphorus (Ca:P) ratio in diets adequate in standardized total tract digestible (STTD) P on performance of 26- to 127-kg pigs fed diets with or without phytase. Pens of pigs (n = 1,134 in Exp. 1 and n = 1,215 in Exp. 2, initially 26.3 and 25.3 kg) were blocked by body weight (BW) and allotted to treatments in a randomized complete block design. There were 27 pigs per pen with 7 and 9 replicates per treatment in Exp. 1 and Exp. 2, respectively. Treatments were formulated to contain 0.75:1, 1.00:1, 1.25:1, 1.50:1, 1.75:1, and 2.00:1 analyzed Ca:P ratios in Exp. 1, and 0.75:1, 1.00:1, 1.25:1, 1.50:1, and 2.00:1 analyzed Ca:P ratios in Exp. 2. These correspond to a range of 0.96:1 to 2.67:1 and 0.95:1 to 2.07:1 STTD Ca:STTD P ratios in Exp. 1 and Exp. 2, respectively. Experiment 2 diets contained 1,000 phytase units of Ronozyme HiPhos 2500 (DSM Nutritional Products, Inc., Parsippany, NJ) with release values of 0.132% STTD P, 0.144% total Ca, and 0.096% STTD Ca. Diets contained 122% of NRC (2012) STTD P estimates for the weight range across 4 phases. In Exp. 1, increasing Ca:P ratio increased (quadratic, P < 0.05) average daily gain (ADG) and average daily feed intake (ADFI). Feed efficiency (G:F) worsened (quadratic, P < 0.05) at the highest ratio. Hot carcass weight (HCW) and bone ash increased (quadratic, P < 0.05) while carcass yield decreased (linear, P < 0.10) with increasing Ca:P ratio. The maximum responses in ADG, HCW, and bone ash were estimated at 1.38:1, 1.25:1, and 1.93:1 analyzed Ca:P and at 1.82:1, 1.64:1, and 2.57:1 STTD Ca:STTD P, respectively. In Exp. 2, increasing Ca:P ratio increased (quadratic, P < 0.05) ADG and bone ash, and improved G:F (linear, P < 0.05). There was a quadratic increase (P < 0.05) in HCW and decrease in carcass yield (P < 0.10). The maximum responses in ADG, HCW, and bone ash were estimated at 1.63:1, 1.11:1 to 1.60:1, and 1.25:1 analyzed Ca:P and at 1.75:1, 1.28:1 to 1.71:1, and 1.40:1 STTD Ca:STTD P, respectively. Expressing ADG on a STTD Ca:STTD P basis provided a more consistent estimate of the ideal Ca:P ratio among the 2 studies than analyzed Ca to analyzed P ratio. A STTD Ca:STTD P ratio between 1.75:1 to 1.82:1 can be used for 26- to 127-kg pigs that are fed diets adequate in STTD P with or without added phytase to maximize growth rate without reducing bone ash.

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