The Texas A&M University System Agricultural Research and Extension Center at Amarillo Manure Concentration of N:P, Animal Performance, and Blood Urea Nitrogen Concentrations of Feedlot Steers Phase Fed Different Levels of Protein. L.W. Greene 1, 2 and J. T. Vasconcelos 1,3 1 Texas Agricultural Experiment Station - Amarillo 2 West Texas A&M University, Canyon 3 Texas A&M University

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Introduction Cattle are started on high concentrate finish diets at approximately 750 lbs and fed to an average weight of 1250 lbs. Early in the feeding period, cattle have a greater deposition of lean tissue and less deposition of fat compared to later in the feeding period. As animals mature through the feeding period, the composition of gain changes -- protein gain decreases and fat gain increases in relative proportion.

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Introduction The typical feedlot diet in the Southern Plains contains 13.0 to 13.5% Crude Protein (% N X 6.25)

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Days on Feed Crude protein excess or deficiency (g/d) during feeding period given a typical diet (adapted from Galyean) Days on Feed Average excess = 50 g/d

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Nitrogen retained, % of intake Collection Period %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo The typical feedlot diet in the Southern Plains contains approximately 0.33% P The typical feedlot steer requirement for P is likely < 0.18%. Introduction

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Phosphorus excess or deficiency (g/d) during feeding period given a typical diet (adapted from Galyean) Days on Feed Average excess 6.7 g/d

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Phosphorus retained, % of intake Collection Period %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo The typical feedlot diet does not contain supplemented P. The dietary P is supplied from the dietary ingredients. Introduction Dried distillers grains Cottonseed meal Alfalfa hay Sorghum silage Corn silage Corn grain Phosphorus, %Crude Protein, %Source

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Objective Determine the effects of phase- feeding of protein in finishing steers on –Steer performance –Blood urea nitrogen concentration –Manure N concentration –Manure P concentration –Carcass characteristics

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Methods One hundred eighty four steers Randomized block design (blocked by weight into heavy medium and light and by start date) 54 steers started on June 6, steers started on June 17, 2003 Steers were housed in 21 pens (7 pens/treatment)

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Methods Three dietary treatments 1. Control diet – 13% Crude protein diet fed continually throughout the feeding period % Crude protein – 13% Crude protein diet fed until cattle the average of the block reached 477 kg, then switched to an 11.5% crude protein diet % Crude protein – 13% Crude protein diet fed until cattle the average of the block reached 477 kg, then switched to no supplemental crude protein diet

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Methods The supplemental protein was supplied from equal amounts of nitrogen from urea and cottonseed meal

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Methods Ingredient composition of finishing diets (DM basis) Item13.0% CP11.5% CP10.0% CP Corn grain, Steam flaked, % Sorghum-sudan silage, %7.50 Molasses, cane, %4.00 Fat, %3.00 Limestone, %1.00 Mineral and vitamin premix, %5.00 Urea, % Cottonseed meal, %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Analyzed chemical composition of finishing diets. Item13.0% CP11.5% CP10.0% CP Crude protein, % NDF, % NE l, (Mcal/lb) NE m, (Mcal/lb) NE g, (Mcal/lb) Ca, % P, % Methods

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Average Daily Gain Beginning until diet change P-value =0.912

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Average Daily Gain Diet change until finish P-value =0.213

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Average Daily Gain Beginning until finish P-value =0.094

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Dry matter intake Beginning until diet change P-value =0.619

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Dry matter intake Diet change until finish P-value =0.008

The Texas A&M University System Agricultural Research and Extension Center at Amarillo kg/d Dry matter intake Beginning until finish P-value =0.056

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Kg gain/ Kg intake Gain efficiency Beginning until diet change P-value =0.832

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Gain efficiency Diet change until finish P-value =0.294 Kg gain/ Kg intake

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Gain efficiency Beginning until finish P-value =0.094 Kg gain/ Kg intake

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Plasma Urea Nitrogen (mg/dL) P-value = Day 0 P-value = Diet change P-value = Harvest

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Pen surface manure concentration Nitrogen P-value =0.600 %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Pen surface manure concentration Ammonia Nitrogen P-value =0.931 %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Pen surface manure concentration Organic Nitrogen P-value =0.549 %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Pen surface manure concentration Phosphorus P-value =0.642 %

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Pen surface manure concentration Nitrogen:Phosphorus P-value =0.038

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Fat thickness, cm P-value =0.227

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Longissimus area, cm 2 P-value =0.192

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Kidney, Pelvic and Heart Fat, % P-value =0.459

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Hot carcass wt, kg P-value =0.663

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Live weight, kg P-value =0.763

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Dressing percentage, % P-value =0.874

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Marbling score P-value =0.173

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Carcass Characteristics Yield grade P-value =0.174

The Texas A&M University System Agricultural Research and Extension Center at Amarillo Variation of crude protein in the experimental diet resulted in lower than expected crude protein intake. Reducing crude protein intake to 8.3% reduced feed intake and tended to reduce ADG when summarized across the entire feeding period. No differences were detected in manure nutrient concentrations but the N:P ratio was increased when the lower CP diet was fed. No differences were detected in USDA Carcass Characteristics. Summary