Effects of maize silage particle size fed as TMR on feed intake, selective consumption and ruminal fermentation in high-yielding dairy cows.

Publication Type

Contribution to conference

Authors

Zebeli, Q., Tafaj, M. and Drochner, W.

Year of publication

2006

Published in

Proc. Soc. Nutr. Physiol.,

Editor

Holger Martens (Hrsg.)

Series/labeling

Berichte der Gesellschaft für Ernährungspyhsiologie

Page (from - to)

146

Conference location

Göttingen

Conference date

21.-23.03.2006

Keywords

cow, dairy cows, particle size, rumen fermentation, TMR-Fütterung

Introduction: Optimisation of particle size (PL) of total mixed rations (TMR) is an important feeding strategy for high-producing dairy cows, because it affects the physical effectiveness and uniformity of TMR, and hence the selective consumption and ruminal fermentation. The objective of this research was to investigate the effect of PL of maize silage (MS) on selective consumption and ruminal fermentation in dairy cows fed TMR ad libitum. Results: Reducing PL of MS in a TMR from 14 to 8.1 and 5.5 mm quadratically increased DMI, while feed selection (measured as difference between original TMR and refusals) significantly decreased (Table 1). Cows consumed more large particles and physical fibre when PL of MS was reduced. This was also reflected by the results of ruminal fermentation. Although, ruminal pH was unaffected by PL (P > 0.05), VFA, and especially propionate significantly increased when the coarsest PL (14 mm) was fed, while butyrate and acetate-to-propionate ratio declined. SRF showed higher fermentation intensity than FRL, which was also reflected by 0.4 to 0.8 lower pH-units. Methods: Four ruminally cannulated (Ø=100 mm) early-lactating Holstein cows (BW = 624 kg, DIM = 60 days and 38 kg of milk/d) were offered three diets, differing in the theoretical particle size (TPL: 14, 8.1 and 5.5mm) of MS (41.4% DM and 50.6% NDF) in a random block design. Feeds were offered ad lib as TMR (40% MS, 10% hay and a 50% wheat-barley-based concentrate mixture) (45% DM, 15% CP, 35% NDF) once daily at 0800 to allow about 10% refusals. Daily feed intake and refusals were electronically recorded. After an adaptation period of 11d, samples of TMR and refusals were daily taken and analysed for DM content, chemical composition and particle size distribution (PD) using Penn State Particle Separator, according to Kononoff et al. (2003). Differences between TMR and refusals, related to their chemical composition and PD, were used as an indicator of selective consumption. To inve