Predictions of total fatty acid (FA) and individual FA content of feeds are necessary for formulating diets based on essential FA requirements of dairy cows. Equations to predict total FA content from crude fat (EE) for different classes of feeds were developed using data from commercial laboratories. The FA composition of total FA for each feed was taken from the CNCPS library. Feed ingredients were grouped into 8 classes. All models were linear and fitted without an intercept. The data for forages were weighted using the inverse of the standard error. Regression coefficients for prediction of total FA from EE, and the mean FA composition are shown in Table 1. Estimates of FA content and composition of feed ingredients are useful to formulate diets for dairy cows when animal feed analysis laboratories are not available. Table 1. Fatty acid (FA) and FA composition (% of total FA) in different classes of feeds

Item	Animal protein	Plant protein	Energy sources	Grainforage crops	By-productsfeeds	Forages1	Oil seeds	Oil
Feed ingredients, n	14	28	35	15	43	57	11	11
Observations, n	6579	18263	181611	1142016	49068	405624	5426	NR3
Regression coefficients2
Slope	0.7310	0.8476	0.7990	0.6100	0.8665	0.5678	0.9286	0.8831
SE	0.0374	0.0235	0.0238	0.0393	0.0178	0.0166	0.0268	0.0021
FA composition
C12:0	0.24	4.70	0.05	0.61	0.76	6.11	0.18	0.08
C14:0	4.86	0.58	1.15	0.74	0.94	0.68	0.42	0.84
C16:0	27.22	15.26	16.74	19.01	20.29	19.53	17.26	7.83
C16:1	6.61	0.59	0.19	0.45	0.28	1.87	0.42	1.14
C18:0	12.31	3.63	2.15	2.38	3.51	2.93	3.60	3.51
C18:1 cis-9	25.52	20.18	20.28	16.32	17.12	2.60	22.90	43.03
C18:1 trans	1.56	0.55	NR3	0.01	1.88	0.42	0.04	2.17
C18:2 cis-9, cis-12	6.71	48.83	54.65	42.29	49.10	19.14	50.36	24.54
C18:3 cis-9, cis-12, cis-15	0.57	9.44	3.53	13.56	6.44	40.55	3.97	10.45
Others	13.85	1.23	0.81	4.68	2.07	6.55	0.96	6.42

¹Forage grasses and legumes. ²Regression coefficients to estimate FA in feeds: FA (% of DM) = crude fat (% of DM) × slope. ³Not reported.