Abstract

This study evaluated the effects of gradual replacement of a mixture of late-cut grass silage (LS) and barley with early-cut grass silage (ES) on milk production, CH4 emissions, and N utilization in Swedish Red cows. Two grass silages were prepared from the same primary growth of timothy grass sward but harvested 2 wk apart [11.0 and 9.7 MJ of metabolizable energy/kg of dry matter (DM)]. Four diets, fed as a total mixed ration, were formulated to meet the metabolizable energy and protein requirements of 35 kg of energy-corrected milk (ECM) by gradually replacing a mixture of LS and barley with ES (0, 33, 67, and 100% of the forage component of the diet), whereas the proportion of barley decreased from 47.2 to 26.6% of diet DM. Expeller canola meal was used as a protein supplement. Sixteen Swedish Red cows were used in 4 replicated 4 x 4 Latin squares. Cows were offered diets ad libitum and milked twice daily. Each period of 28 d comprised 14 d of diet adaptation followed by 14 d of data collection. Intake and milk yield were recorded daily, and milk samples were collected on d 19 to 21 and d 26 to 28 of each period. Diet digestibility was determined by grab sampling using indigestible neutral detergent fiber as an internal marker. Gas emissions were measured using the Green Feed system (C-Lock Inc., Rapid City, SD). Dry matter intake (DMI) linearly decreased from 22.6 to 19.3 kg/d as the proportion of ES increased in the diet. The ECM yield did not differ among treatments, but milk protein yield decreased with increasing proportion of ES in the diet. Because of reduced DMI with increasing ES, feed efficiency (ECM/DMI) improved with an increased proportion of ES in the diet. Nitrogen efficiency (milk N/N intake) did not change despite a linear increase in milk urea N concentration from 9.7 (LS alone) to 11.9 mg/dL (ES alone) with graded replacement of LS and barley by ES in the diet. Lower DMI responses in ES diets were partly compensated for by increased organic matter digestibility (656 g/kg of DM for LS alone; 715 g/kg of DM for ES alone) related to improved forage digestibility at early harvesting. Total CH4 emissions and CH4 intensity (CH4/ECM) were not influenced by diet, but CH4 yield (CH4/DMI) increased linearly from 19.5 to 23.0 g/kg of DMI with greater inclusion of ES in the diet. In conclusion, replacing LS and barley with ES improved the conversion of feed to milk without increasing CH4 emissions or compromising N efficiency.

Keywords

concentrate; feed efficiency; grass silage; methane

Published in

Journal of Dairy Science
2017, Volume: 100, number: 7, pages: 5228-5240

SLU Authors

• Hernando Cabezas Garcia, Edward

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

• Krizsan, Sophie Julie

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

• Huhtanen, Pekka

  • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Animal and Dairy Science


Publication identifier

DOI: https://doi.org/10.3168/jds.2016-12444

Permanent link to this page (URI)

https://res.slu.se/id/publ/82987