1604
STOCHASTIC ANALYSIS OF THE EFFECTS OF VARIATION IN CORN SILAGE COMPOSITION ON THE SUPPLY OF METABOLIZABLE ENERGY AND PROTEIN IN LACTATING DAIRY COWS
The UPENN Ration Balancer, based on CPMDairy and CNCPS 5.1 with modifications, was used to construct a stochastic model to evaluate the influence of variation in corn silage (CSG) composition on the supply of ME and MP and their allowable milk production. Proximate analysis of CSG samples (n=514) from 63 PA farms defined the mean and range in nutrient composition (CP, soluble protein (SP), NPN as a percent of SP, NDF, starch, sugars, water soluble fiber, silage acids, fat, and ash) and NDF degradation rate (Kd) for model inputs. A diet was formulated using mean CSG nutrient content and Kd to meet the ME and MP requirements for a cow (675 kg BW) producing 45.0 kg/d milk with 3.7% fat and 3.1% true protein and a DMI of 24.1 kg/d with the following ingredients (% DM): CSG (41.54), alfalfa haylage (6.22), grass silage (8.30), corn grain (21.98), soybean meal (12.64), Soy Pass (5.51), Energy Booster (0.62), blood meal (1.02), minerals and vitamins (2.12), and an amino acid supplement (0.06). The basal diet composition was as follows (% DM): CP 17.7, NDF 29.0, starch 30.1, sugars 3.4, water soluble fiber 5.3, silage acids 4.2, fat 3.9, and ash 6.5. The mean, SD and nutrient correlation matrix of CSG composition was used to construct an @Risk model (Palisade Corporation, NJ) to exam the influence of stochastic variation in nutrient composition of CSG on ME and MP supply. Five thousand simulations were run varying CSG composition and consequently TMR composition. The influence of CSG nutrient content variation on ME and MP allowable milk was as follows:
CSG Content Range in Allowable Milk, kg/d (in rank)
Nutrient (%DM) Mean Min. Max. ME MP
Lignin 3.0 1.9 5.9 Lignin 3.32 Lignin 2.61
NDF Kd, %/h 3.8 1.3 6.6 NDF kd 2.19 Starch 2.36
NDF 42.0 31.9 58.0 NDF 2.06 NDF 2.03
Starch 31.5 9.3 49.7 Starch 1.27 NDF Kd 1.37
Ash 3.7 1.6 8.8 Ash 1.07 SP 1.02
Fat 3.3 1.2 5.6 Fat 1.04 NPN, % SP 0.44
SP, 4.4 1.6 7.4 SP 0.52 CP 0.41
CP 7.7 5.4 10.9 CP 0.37 Fat 0.22
NPN, % SP 60.5 20.9 100.0 NPN, % CP 0.16 Ash 0.20
Lignin content of CSG had the major influence on both ME and MP supply followed by NDF kd and NDF and starch. Lignin and NDF digestion should be included in forage analysis of CSG.
Keywords: Corn Silage, Production, Nutrient Content