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Dairy cows contribute to climate change primarily through enteric methane (CH 4) emissions. Several mitigating strategies have been evaluated, including the inhibitor 3-nitrooxypropanol (3-NOP). Our objectives were to (1) evaluate the effect of feeding 3-NOP in dairy diets on lactation performance and income over feed costs (IOFC) per cow and per farm, and (2) discuss the potential implications for dairy producers. Data from 15 articles (16 experiments) met the selection criteria, with a total of 412 lactating cows used. The analysis calculated the mean difference data from the 3-NOP treatment mean minus the control treatment mean from that of the NOP-supplemented group. A mixed effects model was fitted to the data. The model included 3-NOP supplementation as fixed effect, and study as a random effect. The 3-NOP dose (mg/kg DM) was included as an explanatory variable. The presence of bias was evaluated by Egger's test, but no publication biases were observed for any of the responses of interest. Income over feed costs per cow per day was calculated based on statistically significant changes in feed consumption, milk yield, and values of milk fat and protein produced less costs for diets feeding 3-NOP. The effects of changes in IOFC were evaluated for herds with different numbers of milking cows (100, 250, and 1, 000 lactating cows). Dairy cows fed 3-NOP had 0. 5 kg/d lower DMI and a reduction in milk yield of 0. 7 kg/d compared with control cows. Milk fat and protein yields were unaffected for dairy cows supplemented with 3-NOP compared with control. Similarly, the ECM yield and feed efficiency were unaffected for dairy cows supplemented with 3-NOP compared with control. However, dose of 3-NOP was negatively associated with the 3-NOP effect size on these performance-related parameters. Feeding 3-NOP caused a reduction of 27. 9% for CH 4 production at an average 3-NOP dose of 80. 3 mg/kg DM. Given changes in DMI, milk yield, and milk fat and protein, supplementation of 3-NOP decreased mean IOFC by 0. 35 cow −1 /d −1 for a cow producing 39 kg/d. These effects on IOFC indicate that under present economic conditions, dairy farmers will need to be compensated by participation in carbon credits programs, provided other incentives for emissions reduction, or both. Reduction of methane emissions with 3-NOP supplementation requires compensation of −128, 320/yr for a dairy with 1, 000 milking cows. In addition, the breakeven compensation for use of 3-NOP varied from −0. 42 cow −1 /d −1 to −0. 21 cow −1 /d −1 based on feed and milk component values from 2014 to 2023. Future research is warranted to evaluate long-term effects of feeding 3-NOP on the productivity of dairy cows.
Pupo et al. (Tue,) studied this question.