Abstract #M378

Section: Ruminant Nutrition
Session: Ruminant Nutrition: Dairy I
Format: Poster
Day/Time: Monday 7:30 AM–9:30 AM
Location: Gatlin Ballroom

# M378
Milk odd- and branched-chain fatty acid profile is affected by lactation stage in dairy cows.
Eric Baumann^*1, P. Yvan Chouinard¹, Yolaine Lebeuf¹, Rachel Gervais¹, ¹Université Laval, Quebec, QC, Canada.

The odd- and branched-chain fatty acid (OBCFA) profile of milk fat has emerged as an interesting, non-invasive tool for evaluating rumen fermentation. These fatty acids are synthesized by different rumen microbial populations, absorbed in the intestine, and taken up by the mammary gland to be incorporated in milk fat. It is well known that milk fat composition is influenced by stage of lactation; proportion of short chains (de novo synthesis) being low initially and increasing with days in milk. However, literature is scarce about the specific effects of stage of lactation on milk OBCFA concentrations. Seven Holstein dairy cows were followed during the experiment. Five data collection and sampling periods were conducted on d 60 to 70, d 120 to 130, d 210 to 220, and d 300 to 310 of a lactation, and on d 5 to 15 of the subsequent lactation. During that period, cows were fed total mixed rations based on grass/legume and corn silages, cracked corn, soybean meal, and corn gluten meal, and formulated to meet their energy and nutrient requirements according to NRC (2001). The results indicate that stage of lactation do affect expression of various milk OBCFA; these effects would need to be considered in the development of models aiming to predict rumen parameters based on milk OBCFA. Table 1. Milk fat concentrations (mg/g) of individual OBCFA

	5-15 DIM	60-70 DIM	120-130 DIM	210-220 DIM	300-310 DIM	P-value
Fatty acid
11:0	0.20^c	0.46^bc	0.49^b	0.86^a	0.69^ab	<0.01
13:0	0.41^d	0.93^c	0.99^bc	1.38^a	1.20^ab	<0.01
15:0	5.47^d	9.86^c	11.17^b	12.50^a	12.32^ab	<0.01
17:0	3.79^a	2.41^b	2.31^bc	2.07^c	2.22^bc	<0.01
c9 17:1	1.85^a	0.85^b	0.76^b	0.77^b	0.79^b	<0.01
Odd	12.04^d	14.77^c	16.05^b	17.90^a	17.52^a	<0.01
ai 13:0	0.15	0.21	0.22	0.16	0.24	0.60
ai 15:0	2.20^b	4.74^a	5.22^a	4.88^a	4.85^a	<0.01
ai 17:0	4.26^a	3.99^ab	4.10^a	3.60^b	3.67^ab	<0.01
Anteiso	6.60^b	8.94^a	9.54^a	8.65^a	8.79^a	<0.01
i 14:0	0.62^b	1.54^a	1.82^a	1.45^a	1.66^a	<0.01
i 16:0	2.06^c	3.42^ab	3.92^a	2.98^b	3.28^ab	<0.01
i 18:0	3.29^c	5.25^ab	5.99^a	4.64^b	5.17^ab	<0.01
Even iso	3.29^c	5.25^ab	5.99^a	4.64^b	5.17^ab	<0.01
i 13:0	0.24^b	0.33^a	0.39^a	0.34^a	0.35^a	<0.01
i 15:0	5.01^c	10.03^b	12.12^a	10.60^a	10.76^a	<0.01
i 17:0	3.32^a	2.88^b	3.03^ab	2.74^b	2.70^b	<0.01
Odd iso	8.57^c	13.24^b	15.54^a	13.68^ab	13.80^ab	<0.01

Key Words: milk fat synthesis, odd- and branched-chain fatty acids, stage of lactation