Symposium review: Comparisons of feed and milk nitrogen efficiency and carbon emissions in organic versus conventional dairy production systems

Abstract

Evaluation of feed efficiency (FE; calculated as energy-corrected milk yield/dry matter intake) and milk nitrogen efficiency (MNE; calculated as milk N yield/N intake) is needed to help farmers make decisions regarding the economic and environmental sustainability of dairy farms. Our primary objective was to compare FE and MNE data obtained from studies conducted with organic versus conventional dairy cows. Specifically, 3 data sets were constructed to meet this goal: (1) the organic Jersey data set (ORG-JE) built with studies (n = 11) done at the University of New Hampshire Burley-Demeritt Organic Dairy Research Farm (Lee, NH), (2) the conventional Jersey data set (CON-JE) constructed using 19 experiments reported in the literature, and (3) the organic non-Jersey-breed (mostly Holstein, Swedish Red, and Norwegian Red) data set (ORG-NJE) created with 11 published studies. Comparisons were made between ORG-JE and CON-JE and between ORG-JE and ORG-NJE. A second objective was to compare the enteric methane (CH 4 ) emission data set from studies using organic Jerseys (n = 5) with those using conventional Jerseys (n = 4). Cows used in the ORG-JE data set had lower FE (−16%) and MNE (−15.5%) than cows used in the CON-JE counterpart, possibly because dry matter intake increased by an average of 10.4% in organic cows. Feed efficiency and MNE computed from cows belonging to the ORG-NJE data set were intermediate between ORG-JE and CON-JE. Measured CH 4 intensity (g/kg of energy-corrected milk) from cows in the ORG-JE CH 4 data set increased by 71% compared with that from cows in the CON-JE CH 4 data set. Estimated FE and enteric CH 4 emissions revealed that Wisconsin organic dairies with the heaviest reliance on forage sources and longest grazing time during the summer were the least feed efficient and emitted the greatest amount of CH 4 per kilogram of energycorrected milk at the animal and whole-farm levels. Overall, the comparisons of FE, MNE, and enteric CH 4 emissions between organic and conventional dairies and within organic systems made in this symposium review should be interpreted cautiously because they are based on study means and small data sets. Research is needed to better characterize the performance, efficiency, profitability, and carbon emissions of forage-based organic dairies in the United States, including the fast-growing "grass-fed" segment, which relies exclusively on forage diets. The effect of large organic dairies on the economic and social sustainability of small and mid-size organic dairy operations nationwide also deserves further investigation.

Production performance, nutrient use efficiency, and predicted enteric methane emissions in dairy cows under confinement or grazing management system

“… Hardie et al (2014) demonstrated via a cluster analysis using 69 organic-certified dairy farms from Wisconsin that dairies feeding the least amount of concentrate and relying heavily on pasture had lower milk rolling herd average (mean = 3,632 kg/cow per year) and income over feed costs ($5.76/lactating cow per d) than those with greatest concentrate and least reliance on grazed herbage (mean = 6,878 kg/cow per year of milk rolling herd average and $10.2/lactating cow per d of income over feed costs). However, organic grassfed milk markets can potentially counteract production losses due to additional premiums paid to farmers ( Benbrook et al, 2018 ; Brito and Silva, 2020 ; Snider et al, 2021 )…”

“…Furthermore, consumers are willing to pay premiums for pasture-based milk and dairy products due to potential human-health benefits ( Benbrook et al, 2018 ; Stampa et al, 2020 ; Peira et al, 2020 ) and the perception that grazing is more environmentally friendly and welfare sounder than confinement ( Wong et al, 2010 ; Bir et al, 2020 ; Joubran et al, 2021 ). This opens opportunities to small dairies capitalize on organic certified and grassfed milk markets to remain economically viable ( Brito and Silva, 2020 ; Snider et al, 2021 ). However, only 10 to 15% of milk produced worldwide comes from grazing operations ( Shalloo et al, 2018 ) and, in Europe and Australia, inclusion of grazed herbage in dairy diets has been declining ( Hennessey et al, 2020 ; Joubran et al, 2021 ).…”

Performance and milk quality parameters of Jersey crossbreds in low-input dairy systems

“…Previous work has shown that Jersey cows, in organic systems, are less efficient than in conventional dairy systems by having 10.4% higher feed intakes, without a comparable increase in milk yield. However, these results were from a small meta-analysis dataset 38 . Although previous studies suggested Jersey genetics in organic and conventional low-input systems herds are likely to have lower milk output than HF cows 4 , this was not the case in the present study, where yield was not affected by crossbreeding.…”

Supplementation of Ascophyllum nodosum meal and monensin: Effects on diversity and relative abundance of ruminal bacterial taxa and the metabolism of iodine and arsenic in lactating dairy cows

“…Based on our previous research (Antaya et al, 2015(Antaya et al, , 2019, the concentration of I in ASCO meal averaged 774 mg/kg of DM. Using average values for DMI of 17.2 kg/d and BW of 427 kg in Jersey cows (Brito and Silva, 2020) and 5% inclusion of ASCO meal in diet DM (Belanche et al, 2016a;Zhou et al, 2018), intake of I would be 666 mg/d, which is about 10,000% greater than the 6.41 mg of I required daily by lactating cows (1.5 mg of I/100 kg of BW; NRC, 2001). Iodine toxicity (Olson et al, 1984) and enlargement of the thyroid gland (Ong et al, 2014) have been reported to occur with 500 mg/d of I intake and 7.5 to 12.5 mg of I intake/100 kg of BW in dairy cows, respectively.…”