A New Research: Feeding MegAnion Can Reduce Manure Ammonia Emission Without Affecting Lactation Performance for Dairy Cows
Feeding anionic supplement and a negative dietary cation-anion difference (DCAD) diet has been known to prevent milk fever in transition cows. There’s evidence that decreasing urine pH (such as by adding acid in urine) will reduce ammonia (NH3) emission from manure (Fangueiro et al., 2015), thus reducing the environmental impact of dairy farming while preserving the manure fertilizer value. However, there hasn’t been a formal study investigating whether feeding anionic supplement would result in lower NH3 emission, and more importantly, whether this would affect feed intake and lactation performance. A recent research (Zynda et al., 2021) presented at 2021 ADSA from Dr. Chanhee Lee group at the Ohio State University investigated the effect of reducing DCAD on lactation performance and nutrient digestibility of lactating cows and NH3 emissions from manure.
Experimental Design:
Twenty-seven mid-lactation Holstein cows received one of three different DCAD diets:
- HIGH, a diet with DCAD of 193 mEq/kg DM
- MED, a diet with DCAD 101 mEq/kg DM
- LOW, a diet with 1 mEq/kg DM
MegAnion replaced urea and some soybean meal in MED and LOW to lower DCAD.
The experiment lasted 7 weeks (1-week covariate followed by 6-week data collection). Spot urine and fecal samples were collected for manure incubation and NH3 emission measurement.
Key Findings:
Feed intake and milk production
Dry matter intake and milk yield were not altered by treatments (Table below). Normally, poor palatability of anionic salts has been a concern for causing decreased feed intake for animals. However, due to the special manufacturing process of MegAnion, dry matter intake (DMI) did not decrease as DCAD decreased from 193 to 1 mEq/kg DM in the current study. In another study (Caixeta et al., 2019), a numerical difference in DMI for transition cows fed MegAnion compared to a competitive product (12.2 vs. 11.0 kg/d, P = 0.17) was observed. The similar DMI may also explain the similar milk yield observed in all treatments.
Table: Effect of reducing DCAD on lactation performance and nutrient digestibility of lactating cows and NH3 emissions from manure
DCAD | SEM | P-value | ||||||
HIGH | MED | LOW | L | Q | ||||
DMI, kg/d | 23.3 | 23.1 | 22.4 | 0.65 | 0.24 | 0.71 | ||
Milk Yield, kg/d | 39.8 | 40.5 | 37.8 | 1.22 | 0.16 | 0.21 | ||
Digestibility, % | ||||||||
DM | 65.7 | 66.6 | 65.3 | 0.55 | 0.58 | 0.91 | ||
OM | 67.5 | 67.8 | 67.1 | 0.53 | 0.61 | 0.47 | ||
NDF | 37.7 | 40.6 | 37.8 | 1.72 | 0.98 | 0.20 | ||
CP | 68.3 | 66.0 | 66.0 | 0.87 | 0.06 | 0.31 | ||
NH3, mg/kg manure d-1 | 76.8 | 74.8 | 64.9 | 4.52 | 0.08 | 0.50 | ||
Cumulative NH3 mg/kg Manure | 461 | 449 | 390 | 29.1 | 0.08 | 0.50 | ||
Nutrient Digestibility
Total tract digestibility of DM, OM, and NDF did not differ among treatments, but total tract digestibility of CP tended to decrease linearly as DCAD decreased (Table above). Previous research has shown different effects of reducing DCAD on nutrient digestibility, and the authors for the current study speculated that the DCAD effects on diet digestibility is also dependent upon a basal diet composition. Potentially the tendency in lower CP digestibility in LOW diet in the current study was due to numerical differences in CP and N intake.
Ammonia Emission
Urine pH decreased from 8.26 for HIGH to 8.05 for MED and 6.38 and LOW, thus decreasing manure pH (7.57, 7.40, and 6.96 for HIGH, MED, and LOW, respectively). Both of daily NH3 emissions and cumulative NH3 emissions from incubated manures tended to decrease as DCAD decreased (76.8 to 64.9 mg/kg manure d– 1 and 461 to 390 mg/kg manure, respectively. Figure below).
Figure: Effect of reducing DCAD on NH3 emissions per kg manure during 6-d incubation
Summary
In short, this study found that lowering DCAD (but still positive) in diet has potential to reduce NH3 emission from manure of lactating cows without negatively affecting dietary fiber and organic matter total tract digestibility and milk yield. In addition, MegAnion has great palatability which was demonstrated in the excellent feed intake when supplemented in diet. Furthermore. this study explored and showcased the possibility of using anionic supplements to reduce NH3 emission and preserve fertilizer N value in manure without compromising milk yield, consequently contributing to a more environmentally sustainable dairy production.
Reference
Caixeta, L. S., W. J. Weber, D. M. Johnson, J. Faser, B. M. Visser, and B. A. Crooker. 2020. Effects of anionic supplement source in prepartum negative dietary cation-anion difference diets on serum calcium, feed intake, and lactational performance of multiparous dairy cows. J. Dairy Sci. 103:4302-4314.
Fangueiro, D., M. Hjorth, and F. Gioelli. 2015. Acidification of animal slurry – A Review. J. of Environ. Manage. 149:46-56
Fei Sun, PhD, PAS
Dairy Product Technical Manager, Origination LLC.
fsun@originationo2d.com
September 6, 2021
