Abstract #M275

Section: Ruminant Nutrition
Session: Ruminant Nutrition I
Format: Poster
Day/Time: Monday 7:30 AM–9:30 AM
Location: Exhibit Hall B

# M275
Effect of feeding different levels of total undigested NDF and forage on production responses of lactating dairy cows.
P. Piantoni^*1, W. I. da Silva Filho¹, C. Canale¹, A. Zontini¹, G. F. Schroeder¹, ¹Cargill Animal Nutrition Innovation Campus, Elk River, MN.

Twenty-four Holstein cows were used in a replicated 4x4 Latin square design experiment with 28-d periods to evaluate the effects of different sources and levels of total undigested neutral-detergent fiber (uNDF; determined after 240 h of in vitro fermentation) on animal performance. Treatments, expressed as % of body weight, were: 1) 0.40% uNDF with 33% forage (high uNDF, low forage: HULF), 2) 0.40% uNDF with 38% forage (high uNDF, medium forage: HUMF), 3) 0.40% uNDF with 48% forage (high uNDF, high forage: HUHF), and 4) 0.30% uNDF with 38% forage (low uNDF, medium forage: LUMF). Linear and quadratic contrasts were used to evaluate the effect of increasing levels of dietary forage at a constant level of uNDF. In addition, a simple contrast was run between treatments HUMF and LUMF to evaluate the effect of 2 levels of uNDF at a similar forage level. There was a quadratic negative effect of increasing forage level on dry matter intake (DMI) and yields of milk, milk fat, and milk protein (Table 1). Feed efficiency (milk yield/DMI) increased as forage in the diet increased at the same level of uNDF. Forage level affected total-tract NDF digestibility (TTNDFD) quadratically: HUMF increased TTNDFD the most, followed by LFHI, and then HFLI. LUMF decreased DMI and increased TTNDFD compared with the HUMF, but did not affect milk yield, resulting in increased feed efficiency. Under the conditions of this study, level of forage was better related to changes in DMI and performance than total uNDF intake. Table 1. Effect of source of undigested uNDF on performance of dairy cows

Item	HULF	HUMF	HUHF	LUMF	SEM	P-value	Contrasts
Item	HULF	HUMF	HUHF	LUMF	SEM	P-value	Linear	Quadratic	HUMFvs. LUMF
DMI, kg/d	29.3	25.4	24.3	24.3	0.79	<0.01	<0.01	<0.01	<0.01
Milk yield, kg/d	35.2	31.9	32.4	32.5	2.06	<0.01	<0.01	<0.01	0.31
Milk fat yield, kg/d	1.34	1.21	1.2	1.22	0.07	<0.01	<0.01	0.04	0.71
Milk protein yield, kg/d	1.13	1.01	1.00	1.00	0.05	<0.01	<0.01	<0.01	0.98
Feed efficiency	1.26	1.32	1.38	1.40	0.06	<0.01	<0.01	0.84	0.04
TTNDFD, %	40.4	43.3	42.5	51.1	0.76	<0.01	0.03	0.02	<0.01

Key Words: indigestible NDF, control of intake, undigested NDF