Effect of Coconut Oil and Lauric Acid on Omasal Nutrient Flow and Microbial Protein Synthesis in Dairy Cows

Abstract Text: Ruminal protozoa (RP) contribute to ruminal bacterial turnover. Previously, feeding lauric acid (LA; C12:0), sharply decreased RP. However, despite reducing RP, LA reduced DMI and milk yield. In this trial, we tested coconut oil (CO), which contains about 50% LA, as a practical defaunating agent and assessed its effects on nutrient and microbial omasal flow. Six cows fitted with ruminal cannulae were blocked by DIM into 2 blocks of 3 cows and randomly assigned within blocks to 3 dietary treatments in a 3X3 replicated Latin square with 21 days of adaptation and 7 days of sampling. The basal diet contained (DM basis) 50% alfalfa silage, 10% corn silage, and 40% concentrate (corn, molasses, and soybean), 16% CP and 29% NDF. Diets A and C provided the same amount of fat: A) 3% Megalac and C) 3% CO. Diets B and C provided the same amount of LA (287g/d). Data were analyzed using the mixed procedure in SAS. Results are reported in the table. DMI was similar among treatments; however, diet B increased NDF flow at the omasal canal and decreased ruminal NDF apparently digestibility. There were trends for reduced DM flow at the omasal canal, ruminal N digestibility and RDP supply, and increased RUP omasal flow, when diet B was fed.

Keywords: Coconut oil, Omasal flow, Protozoa

Table: Ruminal metabolism and omasal flows

Item	Control	LA	CO	SEM	P-value
DM intake, kg/d	22.8	22.4	23.0	1.0	0.14
DM flow, kg/d	14.1	13.6	14.2	0.7	0.06
DM apparently digested in the rumen, kg/d	8.68	8.77	8.76	0.82	0.21
NDF flow, kg/d	4.61b	4.82a	4.64ab	0.19	0.05
NDF apparently digested in the rumen, kg/d	1.87a	1.61b	1.89a	0.16	< 0.01
Total NAN1 flow, g/d	523	522	525	25	0.19
N truly digested in the rumen, g/d	414	404	423	23	0.07
RDP supply, kg/d	2.52	2.46	2.58	0.15	0.09
RUP flow kg/d	1.15	1.17	1.13	0.06	0.08
NMNAN1 flow, g/d	173	176	169	15	0.16
FAB-NAN1 flow, g/d	152	149	155	10	0.13
PAB-NAN1 flow, g/d	198	196	201	16	0.16
Total microbial NAN flow, g/d	350	345	356	19	0.12
Microbial efficiency, g of NAN/kg of OMTDR1	26.0	25.7	26.1	0.7	0.12

^a-bWithin the same row with different superscripts differ (P < 0.05).

¹NAN = non-ammonia N; NMNAN = nonmicrobial NAN; FAB- and PAB-NAN = fluid- and particle-associated bacterial NAN; OMTDR = OM truly digested in the rumen.