A herbal feed additive reduces the urea content in milk of dairy cows

Digestion of fibers and transformation of plant protein into microbial protein is the main nutritive source for dairy cows. The aim of this study was to determine if a herbal feed additive (HFA) containing mainly Urtica dioica L. (herba), Silybum marianum (L.) Gaert. (fructus), Artemisia absinthium L. (herba) and Achillea millefolium L. (herba) can improve the digestive functions of the foregut of dairy cows.

A stratified (farm, age, calving date) randomized placebo (PL) controlled field study was conducted including 106 cows from eleven German and Swiss farms (6 – 12 per farm). From 14 days before calculated calving date until sampling day (mean 206 (+/-40) day of lactation) 100 g HFA or 100 g green meal as control (PL) were fed daily to each cow.

Within each farm, faeces samples were collected on the same date and under same feeding condition, connected to a milk recording day. To evaluate different particle contents of the total faeces dry matter (SF: smaller particle fractions: 0.315 mm – 2 mm; LF: larger particle fractions: > 2 mm) a wet fractionation was conducted. Milk recording data include the contents of fat (%), protein (%), urea (mg/dl), and quantity of milk (kg). A mixed model (ANOVA) was applied whereby the feeding group (HFA and PL) was defined as a fixed factor, the farm as random effect, and the individually differing concentrate levels as a covariate (level of significance p < 0.05; trend p < 0.15).

In the mixed model, cows receiving HFA showed significantly lower milk urea content, and a trend towards a lower LF than cows receiving PL (Tab. 1). Milk urea represents the liver detoxified rumen ammonium, based on microbial degraded feed protein which is not metabolized to microbial protein due to a lack of microbial available energy. An improved rumination (leading to lower LF, connected to a better microbial energy supply) could be possibly due to bitter substances of Artemisia absinthium L. and Achillea millefolium L., but needs further confirmation.

Tab. 1: Influence of a Herbal Feed Additive (HFA) on faeces (faecal particle fractions (g/100gr faeces dry matter): SF – smaller particle fractions: 0.315 mm – 2 mm; LF – larger particle fractions: > 2 mm) and milk [quantity (kg) and contents of fat (%), protein (%) and urea (mg/dL)] parameters compared to a Placebo (PL); Significance (p-value) and standard error (S.E.)

Faeces and milk parameter	Other factors	Feed additive		p-value
		HFA (SE)	PL (SE)
Faeces dry matter	farm			0.02
	concentrates			0.38
		13.1 (0.2)	13.0 (0.2)	0.76
SF	farm			0.014
	concentrates			0.44
		29.0 (0.7)	28.5 (0.6)	0.47
LF	farm			< 0.001
	concentrates			0.21
		7.8 (0.6)	8.8 (0.6)	0.13
Milk kg	farm			< 0.001
	concentrates			< 0.001
		23.4 (1.0)	23.7 (1.1)	0.96
Fat	farm			0.006
	concentrates			0.83
		4.4 (0.1)	4.3 (0.1)	0.71
Protein	farm			< 0.001
	concentrates			0.16
		3.5 (0.1)	3.5 (0.1)	0.86
urea	farm			< 0.001
	concentrates			0.95
		19.0 (1.0)	21.0 (1.0)	0.03