Submitted to: Journal Dairy Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 5/10/2011
Publication Date: 7/10/2011
Citation: Ross, S., Brito, A.F., Soder, K.J., Green, K., Green, A., Chouinard, Y. 2011. Effect of molasses or cornmeal on milk production and nitrogen utilization of grazing organic dairy cows. Journal Dairy Science. 94(1):317. Interpretive Summary: An interpretive summary is not required.
Technical Abstract: Pasture is rich in soluble nitrogen (N) which is rapidly converted to ammonia in the rumen reducing N utilization in lactating dairy cows. Sucrose is more quickly degraded in the rumen than starch, suggesting that feeding molasses (MOL) to balance the supplies of energy and rumen degradable protein (RDP) in the rumen can be strategically used to improve N utilization in grazing dairy cows. Twenty lactating organic Jersey cows were blocked by parity and milk production, and assigned randomly to one of two energy sources: 1) liquid MOL (12% diet dry matter (DM)) or 2) cornmeal (CM; 12% diet (DM)). MOL and CM averaged (% DM), respectively: 5.35% vs. 7.85% crude protein (CP), 68.9 vs. 0.12% starch, and 1.53 vs. 50.1% sucrose. Cows grazed from early June to mid-September for a total of approximately 110 days. The energy sources were top-dressed on a grass-legume baleage (18% diet (DM)) and fed individually twice daily using Calan doors. Cows were split into two grazing groups with pasture intake estimated by group using a calibrated rising plate meter to quantify pre- and post-grazing herbage biomass. Data was analyzed using the MIXED procedure of SAS for a completely randomized design with repeated measures over time. Intake of supplement (baleage plus MOL or CM) was significantly higher for cows fed MOL vs. CM possibly due to the enhanced palatability of MOL. Pasture and total dry matter intake (DMI) were numerically higher for cows fed MOL than those fed CM. Despite enhanced total DMI, no significant differences were observed for milk yield comparing these two energy sources. Likewise, yields and contents of milk components did not differ between MOL and CM. However, cows fed MOL had reduced milk urea nitrogen (MUN; P = 0.03) and plasma urea nitrogen (PUN; P less than 0.01) compared to those fed CM, which may be partially explained by the higher CP of CM vs. MOL. Compared to CM, MOL had no detrimental effect on animal performance and improved N utilization in organic dairy cows. Liquid MOL may be an alternative energy source for CM if economically competitive.