Effect of the Nitrification Inhibitor Dicyandiamide (DCD) on Rumen Function

Researchers at Teagasc, Ireland, look at whether Nitrification Inhibitor Dicyandiamide (DCD) has any effect on rumen function.
calendar icon 20 May 2012
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Introduction

Urinary N has a high potential for leaching (Haynes and Williams, 1993) and urine patches account for approximately 25% of the paddock area over the year (Haynes and Williams, 1993). Hence, urinary N leaching can be a major issue. Moir et al. (2007) reported that dicyandiamide (DCD) reduced nitrate (NO3 -) leaching under urine patches by slowing the conversion of ammonium (NH3 -) to NO3 - in the soil, thereby increasing the quantity of available N in the soil. Dicyandiamide applied at a rate of 10 kg ha-1 can reduce NO3 - leaching by 45% and nitrous oxide (N2O) emissions by 70% under dairy cow urine (1000 kg N ha- 1) patches in Irish soils (Selbie et al., 2011). Therefore, N emissions from pastures can be significantly reduced by applying DCD to pastures. Recently there has been increasing interest in supplementing animals with nitrification inhibitors, so that the nitrification inhibitor is excreted with the urine and can work directly on the urine patch eliminating the requirement for broadcast application in the field. Ledgard et al. (2008) demonstrated that at least 86% of DCD infused into the rumen or abomasum of sheep was excreted in the urine. There is no published research on the effects that the infusion of DCD may have on the rumen function of dairy cows. Rumen parameters such as pH and volatile fatty acids (VFA) are an important factor in relation to animal health, performance and welfare (de Veth and Kolver, 2001). Therefore, the objective of this study was to investigate the effects on dairy cow rumen function of infusing the nitrification inhibitor dicyandiamide (DCD) into the rumen.

Materials and Methods

The experiment took place at the Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Co. Cork. A Latin square experimental design was used with 2 treatments and 2 periods. Eight nonlactating Holstein-Friesian dairy cows, fitted with ruminal cannulae, were housed in individual stalls. In each period, the animals were offered fresh cut perennial ryegrass pasture daily at a feeding rate of 2.5 times maintenance. Each period lasted 12 days. This composed of a 6-day acclimatization stage and a 6-day treatment and measurement stage. The two periods were separated by a 10-day washout cycle. The two treatments were: (1) Control (CON), 500 ml distilled water daily and (2) Dicyandiamide (DCD), 0.1 g DCD kg lwt-1 dissolved in 500 ml distilled water daily. The treatments were pulse-dosed into the rumen daily during the 6-day measurement stage with half the volume dosed in the morning and the remaining half in the afternoon. Rumen measurements took place on days 7, 8 and 11 of each period at 09:00 h and 15:00 h. At these times rumen samples were collected. The samples were strained through three layers of synthetic cheesecloth and frozen for subsequent analysis of lactic acid. The samples were frozen with 50% TCA for subsequent analysis of VFA and ammonia. The data were analysed as a 2x2 Latin square using the mixed procedure (PROC MIXED) of SAS with treatment, experimental period, square, cow and their interactions included in the model.

Results and Discussion

The infusion of DCD into the rumen of dairy cows had no effect on any of the rumen function parameters measured in this experiment as illustrated in Table 1. Rumen parameters examined in this experiment were within the normal range reported for dairy cows offered a pasture diet (Kolver and de Veth, 2002).

The Effect of DCD Compared to a Control Infusion of Distilled Water on Ammonia, Lactic Acid, Total VFA, Concentrations of Individual VFA and the Ratio of Ketogenic:Glucogenic VFA in Non-Lactating Dairy Cows Offered a Pasture Diet.

Item Con DCD s.e.m.a Sig
pH 5.96 5.93 0.06 NS
Ammonia (umol/L) 22.0 20.91 0.99 NS
L-lactic acid (mmol/L) 0.88 1.05 0.22 NS
D-lactic acid (mmol/L) 3.50 3.46 0.45 NS
Total VFA (mmol/l) 121.6 117.2 3.57 NS
Acetic acid (mmol/l) 76.4 73.7 2.33 NS
Propionic acid (mmol/l) 22.2 21.8 0.95 NS
Butyric acid (mmol/l) 16.9 15.9 0.45 NS
Iso acids (mmol/l) 4.35 4.1 0.15 NS
Other acids (mmol/l) 1.77 1.68 0.54 NS
Ketogenic:glucogenic 4.25 4.20 0.11 NS
VFA ratio b
a Standard error of mean
b (acetic + butyric) / propionic

Conclusion

The infusion of DCD into the rumen of non-lactating dairy cows is a novel concept to directly apply DCD to urine patches on a grazing sward. Dicyandiamide had no deleterious effect on the rumen function of nonlactating dairy cows as evidenced by no change to the rumen parameters.

Reference

de Veth, M.J. and Kolver, E.S. (2001) J. Dairy Sci. 84: 1449-1457.

Haynes, R.J. and Williams, P.H. (1993) Adv. Agron. 49:119-199.

Kolver, E.S. and de Veth, M.J. (2002.) Prediction of Ruminal pH from Pasture-Based Diets. J. Dairy Sci. 85: 1255-1266.

Ledgard, S.F., Menneer, J.C., Dexter, M.M., Kear, M.J., Lindsey, S., Peters, J.S. and Pacheco, D. (2008) Agri. Ecosyst. Environ. 125:148-158.

Moir, J.L., Cameron, K.C. and Di, H.J. (2007) Soil Use and Manage. 23:111-120.

Selbie, D.R., Lanigan, G., Di, H.J., Moir, J.L., Cameron, K.C. and Richards, K.G. (2011) Proc. Agric. Res. Forum, Tullamore, p2.

May 2012

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