|ERICKSON, MARY GRACE - University Of Wisconsin|
|PIZARRO, DANTE - University Of Wisconsin|
|WATTIAUX, MICHAEL - University Of Wisconsin|
Submitted to: International Conference on Greenhouse Gasses and Animal Agriculture
Publication Type: Abstract Only
Publication Acceptance Date: 5/9/2022
Publication Date: N/A
Technical Abstract: Although ruminal production of greenhouse gases (GHG) has been well-studied in relation to carbohydrate nutrition, limited research has been carried out on the potential mediating effects of level of crude protein (CP) on ruminal carbohydrate fermentation and subsequent GHG emissions. Additionally, it is unclear how time-varying dietary composition affects GHG production. Our objective was to quantify the methane (CH4) and carbon dioxide (CO2) production of eight non-cannulated, mid- to late-lactation Holsteins during a 2x2 factorial study of CP level (LowCP, 14.5%; HighCP, 16.5%) and feeding pattern (OSC = CP oscillating at 48 hr interval, STAT = static). Cows were housed in tie stalls and fed total-mixed rations with a 60:40 forage-to-concentrate ratio. Diets were formulated by linearly exchanging soy hulls and ground corn with solvent soybean meal, maintaining a constant neutral detergent fiber (NDF):starch ratio (1.18) and constant ratio of rumen-degradable to crude protein (61%). Treatments (n = 4) were arranged in a replicated Latin Square design across four 28-d periods. Throughout the study, feed intake and milk production were recorded daily, with samples of orts and milk taken on day 24-28 of each period. From day 14-21 of each period, gas production was sampled 3x/day with a GreenFeed unit (C-Lock, Rapid City, SD). Cow*Period-level production and GHG data will be analyzed using a linear mixed model in R. Results will summarize lactation performance and estimate the effects of CP level and feeding pattern on GHG production (g/d, g/kg bodyweight (BW), g/kg metabolic BW), yield (g/kg dry matter intake, g/kg NDF intake, g/kg digested NDF), and intensity (g/kg milk yield, g/kg fat-protein-corrected milk yield). Raw treatment means for CH4 production (g/d): OSC = 478, STAT = 469; LowCP = 472, HighCP = 474. Raw treatment means for CO2 production (g/d): OSC = 15,212, STAT = 14,879; LowCP = 14,848, HighCP = 15,243.