Enteric methane emission and lactational performance of dairy cows fed 3-nitrooxypropanol
Open Access
- Author:
- Melgar Moreno, Audino
- Graduate Program:
- Animal Science
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 06, 2020
- Committee Members:
- Alexander N. Hristov, Dissertation Advisor/Co-Advisor
Alexander N. Hristov, Committee Chair/Co-Chair
Tara L. Felix, Committee Member
Troy L.Ott, Committee Member
Kenneth J. Davis, Outside Member
Terry D Etherton, Program Head/Chair - Keywords:
- enteric methane
3-nitrooxypropanol
dairy cattle
dry matter intake
lactation performance
reproduction - Abstract:
- The overall objective of this dissertation was to examine enteric methane emission and lactational performance of dairy cows fed 3-nitrooxypropanol (3-NOP), a recently developed enteric methane inhibitor under investigation. To accomplish this objective, four experiments were conducted including 3-NOP with the diet. Two long-term experiments examined the effect of 3-NOP on intake and lactational performance of dairy cows, one during early-lactation and the other one during mid-lactation. Two other experiments tested graded levels of 3-NOP, one examined dose-response on enteric gas emission and the other one evaluated short-term dry matter intake of a diet containing increasing levels of 3-NOP. The first experiment examined the effects of 3-NOP on enteric methane emission, rumen fermentation, lactational performance, sensory properties of milk, and the resumption of ovarian cyclicity in early-lactation dairy cows. Cows entered the experiment three days after calving and were assigned to one of two diets, a control diet (no 3-NOP) or a diet containing 3-NOP at 60 mg/kg feed dry matter for 15 consecutive wks. Enteric gas emission measured with the GreenFeed system indicated that compared with control, 3-NOP supplementation decreased absolute methane emission by 26%, with no negative effects on intake, improved feed efficiency, and did not affect lactational performance or onset of ovarian cyclicity during early-lactation. Concentrations of de novo synthesized short-chain fatty acids and milk urea nitrogen in milk were increased by 3-NOP, but treatment had no other effects on milk components. Milk sensory acceptance panel and cheddar cheese acceptance test evaluation showed that inclusion of 3-NOP triggered no perceptible changes in milk and cheddar cheese sensory properties. The second experiment examined the dose-response effect of 3-NOP on enteric methane emission and milk composition in dairy cows during mid- to late-lactation. Cows were assigned to one of seven treatments [control (no 3-NOP) and 40, 60, 80, 100, 150, and 200 mg 3-NOP/kg feed dry matter]. Enteric gas emission was measured using the GreenFeed system and milk samples were analyzed for milk composition. Compared to control, inclusion dose of 3-NOP decreased daily enteric methane emission from 22 to 40%, with an average reduction of 31%. Maximum mitigation effect was achieved with the three highest 3-NOP doses. The reduction effect was similar among 100, 150, and 200 mg/kg. Dose of 3-NOP did not affect dry matter intake and milk yield; inclusion dose increased milk fat concentration (mainly de novo synthesized short-chain fatty acids in milk) and yield, tended to increase milk urea nitrogen but had no other effects on milk components. The third experiment examined the effect of increasing levels of 3-NOP on short-term dry matter intake in lactating dairy cows. Cows were fed a control diet (no 3-NOP) and a diet containing increasing levels of 3-NOP, included at 30, 60, 90, or 120 mg/kg dry matter. Compared to control, dry matter intake of diet was increased by 3-NOP inclusion rates of 30, 60, and 90 mg/kg feed DM. Compared with the lower 3-NOP doses, dry matter intake was decreased at 120 mg/kg but was similar to the control, suggesting that 3-NOP does not have a negative effect on dry matter intake in lactating dairy cows. A fourth experiment examined the effect of 3-NOP on enteric methane emission and lactational performance of mid-lactation dairy cows. Cows were fed a control diet or a diet containing 60 mg 3-NOP/kg feed dry matter for 15 consecutive weeks. Cows were housed in a free-stall barn equipped with Calan Broadbend Feeding System to monitor individual intake and three GreenFeed units for continuous enteric gas emission measurement. Compared with the control, cows fed 3-NOP had decreased methane daily emission by 26% with no effects on dry matter intake, cow body weight, body weight change, or lactational performance. The mitigation effect of 3-NOP on enteric methane was greatest immediately after feeding and least before feeding. 3-nitrooxypropanol increased milk fat concentration (mainly de novo synthesized short-chain fatty acids), increased milk fat yield, increased milk urea nitrogen and had no other effects on milk components. Within a wide range of 3-NOP inclusion (30 to 120 mg/kg feed DM), 3-NOP appeared not to affect DMI in lactating dairy cows. During early lactation, 3-NOP supplementation did not affect resumption of ovarian cyclicity. Inclusion of 3-NOP did not appear to affect milk and cheese sensory properties. Overall results from these four experiments suggest that the investigational methane inhibitor 3-NOP is a promising feed additive for reducing enteric methane emission with no negative effects on dry matter intake, while maintaining lactational performance in dairy cows and potentially increasing milk fat yield.