Effects of particle size reduction of meadow hay on feed intake, performance, and apparent total tract nutrient digestibility in dairy cows

ABSTRACT

Forage-based diets are encouraged in organic dairy cattle production as this can increase the net human food supply, but their voluminous nature can limit dry matter intake (DMI) and performance. This study investigates the effects of a substantial particle size reduction of hay on dairy cows’ feed intake, performance, and body characteristics, as well as on apparent total tract digestibility (ATTD). Eighteen lactating Holstein cows were allocated to two balanced feeding groups. The control group received long stem hay with a conventional particle size (CON), the experimental group received chopped hay (RED). Both groups were supplemented with concentrates (3.6 kg/d, DM basis). After 14 adaptation days, data were collected for 20 consecutive days. A covariate period of 21 days preceded the experimental feeding period. Particles retained on the 19-, 8- and 4-mm screens and on the pan of the Penn State Particle Separator accounted for 21%, 20%, 20% and 39% of the RED hay. CON hay consisted of 72% large particles, followed by 8%, 7% and 13% retained on the other screens. Average DMI levels of cows in the CON group reached 20.8 kg/d, with a nonsignificant increase (+1.05 kg/d) in the RED group (p = 0.28). Intakes of both NFC (+0.65 kg/d, p = 0.01) and CP (+0.28 kg/d, p = 0.05) were significantly greater in the RED group, resulting in a slightly increased milk yield (+0.8 kg energy corrected milk/d) (p = 0.45), likely because the ATTD decreased significantly when feeding RED hay. No impact was observed on energy balance (103.7 vs 103.9%, p = 0.95), feed conversion efficiency (kg ECM/kg DMI), or N use efficiency. Overall, the results indicate increases in intake of NFC and CP in the RED group when feeding a hay-based (>83%, DM basis) diet, but also a decrease in nutrient digestibility, likely due to increased passage rate, potentially because of the high fraction of hay particles < 4 mm. In conclusion, hay-based rations with a lower proportion of fine particles should be tested to exploit the potential of particle size reduction in terms of improving hay use efficiency.

KEYWORDS:

• Forage-based feeding
• hay particle size reduction
• apparent total tract digestibility
• milk performance

Acknowledgments

The authors are grateful to the Austrian Federal Ministry for Agriculture, Forestry, Regions and Water Management [project number 101663], the Provincial Government of Salzburg, Austria, Raiffeisenverband Salzburg, Austria, the ARGE Heumilch, Innsbruck, Austria, and the “Ja! Natürlich” brand of the REWE group, Wiener Neudorf, Austria, for funding this experiment. Additionally, we are grateful to the Secondary School for Agriculture, Environmental and Resource Management HBLA Ursprung, Elixhausen, Austria, for housing the experiment; to the farm staff, Florian Gollhofer and especially Franz Griessner for their dedication and help with the experiment. We would also like to thank Anita Dockner, Dr. Manfred Hollmann, Sabine Leiner and Suchitra Sharma, BSc. (Institute of Animal Nutrition and Functional Plant Compounds at the University of Veterinary Medicine Vienna, Austria) for performing chemical analyses. Our thanks also go to Kathleen Knaus for editing assistance.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the Bundesministerium für Land- und Forstwirtschaft, Regionen und Wasserwirtschaft, Austria Provincial Government of Salzburg, Austria “Ja! Natürlich” brand of the REWE group, Wiener Neudorf, Austria ARGE Heumilch, Innsbruck, Austria Raiffeisenverband Salzburg, Austria .