Location: Pasture Systems & Watershed Management Research
Project Number: 8070-21500-001-008-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Aug 31, 2028
Objective:
We learned that profitable strategies to maximize forage and pasture utilization are challenging to 75% of Northeastern organic dairy producers who participated in our focus groups and surveys. In addition, the growing season in the Northeast is relatively short and characterized by periods of low forage production during early spring, mid-summer, and late fall. Therefore, opportunities exist to fill these gaps in forage productivity by growing nutritive, high yielding annual crops to extend the grazing season. However, there is limited information regarding which annual forages or crop rotations should be used for optimizing milk production and farm profitability in the Northeast US. Brassicas (Brassicas spp.), which include species such as turnip, radish, rapeseed, kale, and canola have emerged as promising annual crops for fall grazing because of their high nutritive value and digestibility and decreased enteric methane emissions, thereby improving dietary energy utilization and production of milk and milk components. Furthermore, with the rapidly growing consumers’ demand for “grass-fed” milk and dairy products, together with reduced feed costs associated with grazing, producers can capitalize on forage-based systems to realize profits and remain economically viable.
Approach:
Objective 1: Quantify animal performance, health markers, and energy utilization efficiency in dairy cows grazing brassicas.
Two grazing experiments (Years 1-2) will be conducted at the Cooperators' Organic Dairy Research Farm (Lee, NH). Twenty mid-lactation organic certified Jersey cows will be assigned to 1 of 2 treatments as follows: (1) 100% total mixed ration (TMR; control: n = 10 cows) or (2) 50% TMR + 50% brassica (n = 10 cows). Cows assigned to the brassica treatment [radish (Year 1) and turnips (Year 2)] will be fed TMR during the day and grazed overnight. Grazing will initiate 45 days after planting (early July) in 2 grazing rotations of 4 weeks each. Each study will be set up as a randomized complete block design with a 2-week covariate period (baseline) followed by an 8-week data collection over 2 growing seasons. Cows will be milked twice daily, with milk production recorded throughout the length of the studies. The TMR will be fed after each milking, with individual feed intake measured using Calan doors. Feed samples will be shipped to commercial laboratories for nutrient profile and glucosinolate analyses. Milk samples will be collected during 4 consecutive milkings (covariate; weeks 4 and 8) and analyzed for fat, protein, lactose, and milk urea-N. Body weight and body condition score will be recorded during the last 3 days of the covariate period and weeks 4 and 8. Fecal and urinary samples will be taken twice daily (a.m. and p.m.) during 5 consecutive days (weeks 4 and 8) for determination of nutrient digestibility and excretion of N, respectively. Gaseous emissions (methane, carbon dioxide, hydrogen, and oxygen) will be measured using 2 portable, automated head chambers (GreenFeed system) throughout the 10-week studies, with data used for estimation of energy utilization. Blood samples will be collected (covariate; weeks 4 and 8) and analyzed for whole-blood hematological parameters.
Objective 2: Quantify fermentation characteristics and glucosinolates in silages made from brassicas.
We will quantify productivity, nutritive value, and glucosinolate concentrations of radish, canola, turnip, rape, and kale grown in monocultures and mixtures by establishing experiments using 4 rates of fertilization with calcium sulfate at the Cooperators' Kingman Farm (Madbury, NH). Previous research showed that glucosinolates may be modulated by sulfur supply and evidence suggests that competition and other biotic stresses may further affect glucosinolate levels. Experiments will be established at 2 time points to target 2 planting/forage availability windows (summer planting for fall availability and fall planting for spring/summer availability). Monocultures and mixtures will be also ensiled using mini-silos to capitalize on high sugar content and low buffering capacity of brassicas, which favor rapid and extensive acidification during fermentation. Although ensiling has been shown to affect glucosinolates, little is known on how and why this happens during ensilage. Thus, we will evaluate the effects of extensive curing (50% dry matter) and fermentation period on glucosinolates content of ensiled brassicas.