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Cost-effective feeding strategy for cattle: increasing dietary urea in combination with Silvafeed® Bypro

Published on: 6/26/2017
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The optimisation of the use of nitrogen (N) in ruminants diet can be highly valuable in terms of profitability and sustainability of any farm. In this study it has been assessed the use of economical source of nitrogen in combination with natural plant extracts, mainly tannins, which can influence protein metabolism in the rumen.

Ruminants can make use of certain non-protein nitrogen (or NPN) compounds, some of which are naturally present in the feed. To better grasp what is happening in the rumen, microorganisms can rapidly degrade NPN into ammonia, after which, the latter can be combined with products of carbohydrate metabolism and converted into microbial proteins. Furthermore, vegetable proteins in feed supplements can be costly and are often highly degradable in the rumen. For example, approximately 70% of proteins from soybean meal are degraded. This means that they are transformed into microbial proteins similar to those originating from NPN. This is the reason behind the increasing interest in the use of cost-effective sources of NPN to supply nitrogen in the rumen and replace part of the dietary true proteins. Among the various sources of NPN for ruminant feeding, urea is the most popular and competitive, due to its lower price per unit of N and freight cost. A good utilisation of urea is usually observed with diets high in digestible energy, such as the typical diets formulated for the high-producing cattle. Yet urea should be included at an adequate level and thoroughly mixed in the feed to avoid excessive production of ammonia, which could, in turn, lead to environmental pollution and animal toxicity. Consequently, the inclusion of urea does not usually exceed 1% of the ingested dry matter (Zinn et al, 2003).

Silvafeed® ByPro is a natural feed additive especially developed for ruminants, obtained from a selection of tannin-rich plants. Tannins are well-known plant polyphenols characterised by the ability to chelate the proteins and form insoluble precipitates. Therefore Silvafeed® ByPro can reduce the degradability of plant proteins in the rumen and increase the quantity of metabolisable proteins available in the intestine. In addition, it is likely that Silvafeed® ByPro will reduce urease activity in the rumen, thus potentially regulating urea fermentation potential. Therefore, the trial goal was to evaluate the possibility of increasing urea levels by adding Silvafeed® ByPro in the cattle diet, without impairing animal performance in terms of body weight and feed intake.

Thirty-six Holstein steers (average initial weight=286.7 kg) were allocated into 12 pens and given one of the three experimental diets ad libitum for 85 days (3 treatments with 4 replications or pen). Diets were formulated to be isoenergetic and isonitrogenous, but with increasing level of urea (1%=control, 1.5% and 2%) as shown in Table 1. Silvafeed® ByPro was included at 0.2% in all the diets. The measured parameters were daily feed intake (pen-basis), body weight gain, and calculated feed conversion ratios.

Table 1: Experimental feed diet composition

Feed ingredients

Treatment 1

(urea=1%)

Treatment 2

(urea=1.5%)

Treatment 3

(urea=2%)

Silvafeed® Bypro

2.0 kg

2.0 kg

2.0 kg

Dry corn

715 kg

765 kg

820 kg

Wheat bran

123 kg

100 kg

75 kg

Soybean

65 kg

35 kg

-

Chopped pasture

60 kg

60 kg

60 kg

Seashell in powder (Calcium Carbonate)

20 kg

18 kg

18 kg

Urea

10 kg

15 kg

20 kg

Salt

4.5 kg

4.5 kg

4.5 kg

Mix of micronutrients free of monensin

0.5 kg

0.5 kg

0.5 kg

The average daily feed intake was found close between treatments with 1% and 1.5% of urea (arithmetic means=9.48 and 10 kg of dry matter, respectively), and numerically lower for the treatment with 2% urea (7.93 kg of dry matter) (Figure 1).

The average weight gain was significantly higher in treatment with 1.5% urea (corresponding to 1.67 kg/steer/day) in comparison to treatment with 1% urea (1.52 kg/steer/day) and 2% urea (1.27 kg/steer/day) (Figure 2).

Furthermore, the average feed conversion ratio was lower in treatment with 1.5% urea (6.0) when compared with treatment 1% urea (6.23) and treatment 2% urea (6.25).

In conclusion, increasing the level of urea from 1% to 1.5% in the diet of ruminants is a feasible strategy to reduce feeding cost, thanks to the addition of Silvafeed® ByPro dosed at 2kg/ton. In fact, the encouraging results suggest favourable animal responses in terms of feed intake, body weight gain and feed conversion rate. Moreover, the inclusion of urea at 2% does not substantially impair feed conversion ratio, but seems to be an upper threshold as clear trends for lower feed intake and weight gain can be observed with this specific treatment dose.

References
Zinn R.A., Barrajas R., Montano M., and Ware R.A., 2003. Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley-based finishing diets. J. Anim. Sci. 81:2383–2389.

 
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