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ARS Home » Northeast Area » University Park, Pennsylvania » Pasture Systems & Watershed Management Research » Research » Publications at this Location » Publication #336415
Title: Production performance and milk fatty acids profile in grazing dairy cows offered ground corn or liquid molasses as the sole supplemental nonstructural carbohydrate source

Author
item REIS, SIMONE - University Of New Hampshire
item Soder, Kathy
item CHOUINARD, P. YVAN - Laval University
item ROSS, SHARA - University Of New Hampshire
item RUBANO, MELISSA - Consultant
item Casler, Michael
item BRITO, ANDRE - University Of New Hampshire

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2017
Publication Date: 9/10/2017
Citation: Reis, S.F., Soder, K.J., Chouinard, P., Ross, S., Rubano, M.D., Casler, M.D., Brito, A.F. 2017. Production performance and milk fatty acids profile in grazing dairy cows offered ground corn or liquid molasses as the sole supplemental nonstructural carbohydrate source. Journal of Dairy Science. 100:8146-8160. https://doi.org/10.3168/jds.2017-12618.
DOI: https://doi.org/10.3168/jds.2017-12618

Interpretive Summary: Grazing dairy farms are interested in replacing corn supplement with molasses to decrease feed costs and meet the goals of specialty milk markets such as organic or grassfed milk. We investigated the effects of supplementing grazing, lactating dairy cows with either corn meal or liquid molasses on milk yield and milk composition, milk fatty acid profile, and nitrogen use efficiency. Based on results of the current experiment, molasses can replace corn meal on an equivalent basis without negatively affecting milk yield and composition, while slightly improving N efficiency and beneficial fatty acids found in milk.

Technical Abstract: The objective of this study was to compare the effects of corn meal or liquid molasses fed as the sole supplemental nonstructural carbohydrate source on milk yield and composition, milk fatty acids, and N use efficiency in grazing dairy cows. Ten multiparous organically-certified Jersey cows averaging (mean ± SD) 21.3 ± 4.1 kg of milk/d, 65 ± 57 days in milk, and 415 ± 25 kg of body weight, and 10 primiparous organically-certified Jersey cows averaging 12.8 ± 5 kg of milk/d, 177 ± 33 days in milk, and 346 ± 19 kg of body weight were used. Cows were paired (n = 10 pairs) with each pair balanced for parity, days in milk, and milk yield. Pairs were then randomly assigned to 1 of 2 dietary treatments: mixed-mostly legume grass baleage plus corn meal (B+CM) or baleage plus liquid molasses (B+LM) fed at 12% of total dry matter intake (DMI). The study was conducted from June to September with data and samples collection conducted on weeks 3, 7, 12, and 15. Milk samples for fatty acid (FA) profile were collected on week 2, 4, 6, 8, 9, 11, and 13. Data were analyzed using the MIXED procedure of SAS for a completely randomized design with repeated measures over time. Significant treatment × week interactions were observed for supplement DMI, milk urea N (MUN), urinary excretion of uric acid, and milk FA including 18:0, cis-9, trans-11 18:2, and polyunsaturated FA. Week effects were observed for plasma urea N (PUN), milk concentration of fat, true protein, and total solids, most saturated FA, and all unsaturated FA. Milk yield, concentration and yield of milk components, and plasma concentrations of essential AA were not affected by supplementation. The MUN (weeks 7 and 15) and PUN decreased with feeding B+LM, suggesting improved N use efficiency due to better timing between the release of ruminally fermentable energy from liquid molasses and rumen-degradable protein from herbage compared with corn meal. Supplement DMI was greatest in cows fed B+LM in weeks 7, 12, and 15, thus supporting the MUN and PUN responses. Feeding B+CM increased milk monounsaturated FA, while feeding B+LM increased S n-3 FA and decreased the n-6 to n-3 ratio and trans-10 18:1. Decreased trans-10 18:1suggests that liquid molasses was detrimental to the biohydrogenation pathways associated with milk fat depression. It can be concluded that liquid molasses can entirely replace corn meal without negatively affecting milk yield and composition, while decreasing MUN, PUN, and milk trans-10 18:1.