Effect of feeding rolled flaxseed on milk fatty acid ...

Effect of feeding rolled flaxseed on milk fatty acid profiles and reproductive performance of dairy cows N. R. Bork, J. W. Schroeder, G. P. Lardy, K. A. Vonnahme, M. L. Bauer, D. S. Buchanan, R. D. Shaver and P. M. Fricke J ANIM SCI 2010, 88:3739-3748. doi: 10.2527/jas.2010-2841 originally published online July 9, 2010

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Effect of feeding rolled flaxseed on milk fatty acid profiles and reproductive performance of dairy cows1 N. R. Bork,* J. W. Schroeder,*2 G. P. Lardy,* K. A. Vonnahme,* M. L. Bauer,* D. S. Buchanan,* R. D. Shaver,† and P. M. Fricke† *Department of Animal Sciences, North Dakota State University, Fargo 58108; and †Department of Dairy Science, University of Wisconsin, Madison 53706

ABSTRACT: The objectives were to study the effects of feeding rolled flaxseed (FLX) to early-lactation dairy cows on milk yield, milk components, and milk fatty acid profiles as well as on measures of cow reproduction. Lactating Holstein cows, on 3 commercial dairies, were fed either an early-lactation ration (CON) or a ration that was similar in protein, energy, and fat content but that included FLX (0.85 kg of DM/ cow per day). Within each dairy, cows were allocated alternately to breeding pens upon leaving the fresh pen (approximately 10 ± 5 d postpartum). Pens (n = 4 to 5 pens/dairy) were randomized to treatment (n = 2 to 3 pens/treatment per dairy). Pen (CON, n = 6; FLX, n = 7) was considered the experimental unit and data were analyzed as a split plot with pen as the whole-plot

error term. Cows fed FLX had greater (P ≤ 0.06) proportions of cis-9, trans-11 C18:2, C18:3n-3, and C20:0 fatty acids in milk fat and a lesser (P = 0.03) proportion of C20:3n-6 fatty acid when compared with cows fed the CON diet. Treatment did not affect (P ≥ 0.24) milk yield, milk protein, protein yield, milk fat, or milk fat yield. No interactions (P ≥ 0.52) were found between treatment and season of the year or parity, or between treatment and days open, pregnancies per AI at first or second service, or pregnancy loss. In conclusion, feeding FLX at 0.85 kg/cow per day (DM basis) altered the fatty acid profile of milk, but milk yield, milk composition, and reproductive performance of dairy cows were not affected.

Key words: dairy cow, fertility, flaxseed, α-linolenic acid ©2010 American Society of Animal Science. All rights reserved.

INTRODUCTION Flaxseed has an increased concentration of n-3 fatty acids [FA; C18:3n-3, 53% of total FA (Chow, 1992)] and when fed to early-lactation dairy cows, it may improve reproductive performance and thereby improve dairy enterprise profitability (De Vries, 2006). Data report-

1 The authors thank the owners and staff of Minglewood Dairy (Deer Park, WI), County Line Dairy (Edgerton, MN), and Winding Meadows Dairy (Rock Valley, IA) for the use of their cows and facilities for this study and the consulting nutritionists from each dairy for their assistance in ration formulation. We further express gratitude to S. J. Bertics (University of Wisconsin–Madison) for conducting the laboratory analyses of milk fatty acid profiles and to Kim Koch (Northern Crops Institute, Fargo, ND) for his technical assistance in flaxseed processing and handling. In addition, we thank the North Dakota Oilseed Council (Bismarck) for funding this project and Farmers Elevator (Grace City, ND) for cooperation in the procurement and transportation logistics of the flaxseed used in this research. 2 Corresponding author: [email protected] Received January 19, 2010. Accepted July 7, 2010.

J. Anim. Sci. 2010. 88:3739–3748 doi:10.2527/jas.2010-2841

ing increased reproductive performance from feeding flaxseed to dairy cows are equivocal. Feeding flaxseed or linseed oil influenced several reproductive variables, including improved embryo quality (Thangavelu et al., 2007), decreased pregnancy loss (Ambrose et al., 2006), reduced plasma PGF2α (Petit et al., 2002), and increased serum progesterone concentration (Lessard et al., 2003). By contrast, others (Petit and Twagiramungu, 2006; Fuentes et al., 2008; Petit et al., 2008) reported no improvement in conception rate when feeding flaxseed in various forms (extruded, rolled, and whole) to dairy cows compared with control diets containing no flaxseed. The inconsistent outcomes, insufficient animal numbers to assess reproductive performance, and limited replication of results have led researchers to question whether feeding flaxseed sources to dairy cows would improve reproduction. In a dairy production setting, the objectives were to study the effects of feeding rolled flaxseed [FLX (Linum usitatissimum L.)] to early-lactation dairy cows on milk yield, milk components, and milk FA profiles as well as effects on cow reproductive variables. We hypothesized that adding FLX to the diets of early-

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Table 1. Ingredients and composition of treatment diets1 fed to early-lactation Holstein cows on commercial dairy A CON Item, % of DM

FLX

Primiparous

Multiparous

Primiparous

Multiparous

59.8 40.2 — 0.79 0.48 3.6 17.4 20.5 33.1 1.0 0.4

59.8 40.2 — 0.79 0.48 3.4 17.5 21.2 33.7 1.0 0.5

61.0 39.0 3.26 0.16 0.55 4.3 17.8 20.4 34.0 0.9 0.5

61.0 39.0 3.49 0.16 0.55 3.8 18.1 19.6 32.7 0.9 0.5

2

Forage Concentrate3 Major fat-contributing ingredient Flaxseed Tallow Rumen-inert fat4 Analyzed composition Ether extract CP ADF NDF Ca P

1 Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. Analysis from composited diet samples for each pen (n = 4). 2 Forage includes corn silage, alfalfa haylage, and dry beet pulp. 3 Concentrate includes corn, roasted soybeans, sodium bicarbonate, extruded soybeans, dry distillers grains, calcium carbonate, blood meal, urea, salt, magnesium oxide, dicalcium, magnesium sulfate, and OmniGen-AF (Prince Agri Products Inc., Quincy, IL). 4 Energy Booster 100 (Vita Plus Corp., Madison, WI).

lactation dairy cattle would improve measures of reproductive performance, maintain milk production and its components, and change the FA profile of milk fat to include a greater proportion of n-3 FA.

MATERIALS AND METHODS The North Dakota State University Animal Care and Use Committee approved all animal care procedures.

Experimental Design The experimental design was a randomized complete block design with 2 treatments based on dietary inclusion of flaxseed. The experiment was conducted at 3 commercial dairies (blocking factor): dairy A, Deer Park, WI (August 2006 to December 2007); dairy B, Edgerton, MN (December 2006 to May 2008); and dairy C, Rock Valley, IA (June 2007 to September 2008). Cows and dairies were naïve to flaxseed. Cows were fed their respective treatment diets after leaving the fresh pen. Treatments consisted of either the existing postfresh diet of the dairy (CON; n = 6 pens; n = 641 cows) or a similar diet reformulated using FLX (n = 7 pens; n = 843 cows). For the FLX treatment, FLX replaced a portion of fat sources (dairy A, tallow; dairy B, whole cottonseed and grease; dairy C, animal fat) in the CON diet. The FLX diet was similar in protein, energy, and fat content. Ultimately, FLX diets were formulated to contain 3.35% flaxseed, such that intake of 0.85 kg/cow per day (DM basis) would be achieved when cows reached a DMI plateau of 25.4 kg/d. Formulation and composition of treatment diets for each dairy are shown in Tables 1, 2, and 3.

At dairies A and B, cows were assigned randomly to breeding pens (n = 4 pens/dairy) within parity (primiparous and multiparous; 2 pens/parity) approximately 5 to 15 d postpartum, and pens were assigned randomly to treatments within parity. For dairies A and B, there were 297 and 150 primiparous cows and 440 and 181 multiparous cows, respectively. At dairy C, cows (128 primiparous and 241 multiparous) were not segregated by parity and were assigned randomly to breeding pens (n = 5), and pens were assigned randomly to treatments (n = 2 for CON and 3 for FLX) approximately 5 to 15 d postpartum.

Dairy Reproductive Management Programs Selection of participating cooperators was based on the use of the following criteria for reproductive management. Dairies used an ovulation synchronization protocol to ensure cows enrolled in the experiment received a first postpartum timed AI within 250 d of calving. Dairies conducted weekly pregnancy examinations to ensure pregnancy diagnosis occurred by 45 d after AI. Dairies performed a pregnancy reconfirmation within the following 8 wk for cows diagnosed as pregnant at their first pregnancy examination so that pregnancy losses occurring between pregnancy examinations could be evaluated. Dairies maintained a computerized record-keeping system from which reproductive variables from individual cows could be extracted from archived data. Dairies used a combination of Presynch and Ovsynch programs (Moreira et al., 2001; Navanukraw et al., 2004), with varying degrees and methods of estrous detection to inseminate cows. Within each dairy, cows


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Table 2. Ingredients and composition of treatment diets fed to early-lactation Holstein cows on commercial dairy B CON Item, % of DM 2

Forage Concentrate3 Major fat-contributing ingredient Flaxseed Cottonseed Rumen-inert fat4 Choice white grease Analyzed composition Ether extract CP ADF NDF Ca P

FLX

Primiparous

Multiparous

Primiparous

Multiparous

46.5 53.5 — 4.03 0.71 0.16 3.6 16.9 18.7 35.9 1.1 0.4

46.5 53.5 — 4.03 0.71 0.16 4.3 15.5 18.7 35.4 1.3 0.4

47.5 52.5 3.35 — 0.30 — 5.0 16.0 19.1 35.2 1.0 0.4

47.5 52.5 3.35 — 0.30 — 4.0 16.6 18.6 35.0 1.0 0.4

1 Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. Analysis from monthly composited diet samples for each pen (n = 4). 2 Forage includes corn silage, haylage, and dry alfalfa hay. 3 Concentrate includes ground corn, corn gluten meal, rolled corn, soybean meal, soyhulls, canola meal, blood meal, urea, magnesium oxide, salt, sesquicarbonate, vitamin E, Omnigen-AF (Prince Agri Products Inc., Quincy, IL), UltraMet (Vita Plus Corp., Madison, WI), Vi-COR Amax Yeast (ViCOR Varied Industries Corp., Mason City, IA), Sel-Plex (Alltech, Nicholasville, KY), monensin (Elanco Animal Health, Greenfield, IN), and Zinpro Availa-4 (Eden Prairie, MN). 4 Energy Booster 100 (Vita Plus Corp.).

within breeding pens that were assigned to treatments were subjected to the same reproductive management protocol. A brief description of the reproductive management program for each dairy was as follows.

Table 3. Ingredients and composition of treatment diets1 fed to early-lactation Holstein cows on commercial dairy C Item, % of DM 2

Forage Concentrate3 Major fat-contributing ingredient Flaxseed Cottonseed Animal fat Analyzed composition, % of DM Ether extract CP ADF NDF Ca P 1

CON

FLX

50.2 49.8 — 8.56 0.92 4.7 16.6 21.8 36.2 0.99 0.44

49.5 50.5 3.31 8.56 — 4.5 16.6 24.0 38.8 1.06 0.45

Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. Analysis from monthly composited diet samples for each pen (n = 5). 2 Forage includes corn silage and alfalfa haylage. 3 Concentrate includes ground corn, soybean meal, soyhulls, meat and bone meal, blood meal, magnesium oxide, salt, sodium bicarbonate, vitamin E, limestone, water, potassium and magnesium sulfate, biotin, vitamin and mineral pack, Soy Best (West Point, NE), Omnigen-AF (Prince Agri Products Inc., Quincy, IL), DV-Yeast XP (Diamond V Mills Inc., Cedar Rapids, IA), and Mepron (Evonik Degussa Corporation, Kennesaw, GA).

Dairy A. Cows received the first PGF2α injection of Presynch from 53 to 59 d in milk (DIM). Multiparous cows with milk production less than 45 kg/d determined to be in estrus based on a pedometry system (DeLaval, Tumba, Sweden) were inseminated after the first PGF2α injection of Presynch, whereas multiparous cows with milk production equal to or greater than 45 kg/d continued the protocol. Cows not detected in estrus received a second injection of PGF2α 14 d later, and multiparous and primiparous cows with milk production less than 41 kg/d and determined by the pedometry system to be in estrus were inseminated after the second PGF2α injection of Presynch, whereas primiparous cows with milk production equal to or greater than 41 kg/d continued the protocol. Primiparous cows with milk production equal to or greater than 41 kg/d and multiparous cows not detected in estrus after PGF2α injections of Presynch received timed AI after submission to an Ovsynch protocol (Pursley et al., 1995) initiated 14 d after the second PGF2α injection of Presynch. Second AI and greater were managed using detection of estrous behavior and submission of cows to an Ovsynch protocol after a nonpregnant diagnosis. All pregnancy examinations were performed by the herd veterinarian using transrectal palpation from 35 to 41 d after AI, with pregnancy reconfirmations performed from 70 to 76 d after AI. Dairy B. Cows received the first PGF2α injection of Presynch from 36 to 41 DIM followed by the second PGF2α injection of Presynch 14 d later. Cows were observed visually for estrous behavior by dairy employees throughout the day and were inseminated if detected


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in estrus after the second PGF2α injection of Presynch. Cows not detected in estrus after the second PGF2α injection of Presynch received timed AI after submission to an Ovsynch protocol (Pursley et al., 1995) initiated 14 d after the second PGF2α injection of Presynch. Second and greater AI was managed using detection of estrous behavior and submission of cows to an Ovsynch protocol after a nonpregnant diagnosis. The herd veterinarian performed all pregnancy examinations. An initial pregnancy examination was performed using transrectal ultrasonography from 35 to 41 d after AI, with pregnancy reconfirmations performed using transrectal palpation from 84 to 90 d after AI. Dairy C. Cows received the first PGF2α injection of Presynch from 30 to 36 DIM and the second PGF2α injection of Presynch 14 d later. Any cows detected in estrus were inseminated after the second PGF2α injection of Presynch; however, a rigorous estrous detection program was not used. Cows not detected in estrus after the second PGF2α injection of Presynch received timed AI after submission to an Ovsynch protocol (Pursley et al., 1995) initiated 12 d after the second PGF2α injection of Presynch. Second AI and greater were managed using an Ovsynch protocol for resynchronization initiated 32 d after a previous timed AI, as described by Sterry et al. (2006). All pregnancy examinations were performed by the herd veterinarian using transrectal ultrasonography from 32 to 38 d after AI with pregnancy reconfirmations performed using transrectal ultrasonography from 60 to 66 d after AI. Pregnancies per AI (P/AI) were calculated as the number of pregnant cows divided by the total number of cows that were evaluated. Pregnancy loss was calculated as the number of cows diagnosed as pregnant at the first pregnancy exam that were diagnosed as not pregnant at the pregnancy reconfirmation on each farm.

Sample Collection Each month, basal feed ingredients, diet samples, and copies of herd management records were collected from each dairy. In addition, a composite sample of milk was collected for each treatment pen per dairy during the afternoon milking. Dairies milked 3 times a day. Stringsampling kits (Dairy Herd Improvement Association, Clovis, CA) were used to sample milk via direct insertion into the milk pipeline. The result was a composite of 13 mo of milk samples representing each treatment pen for each dairy. These samples were placed on dry ice immediately after collection and stored at −20°C until analyzed for FA profiles at the Dairy Science Nutrition Laboratory at the University of Wisconsin–Madison. Data regarding milk production and milk composition for individual cows from each dairy were derived from the monthly Dairy Herd Improvement Association reports from each herd. Milk samples were analyzed for fat, protein, lactose, solids-not-fat, and milk urea N by

AgSource Milk Analysis Laboratory (Menomonie, WI) with a near-infrared analyzer (FT6000, Foss Electric, Hillerød, Denmark). Diet and basal feed components were collected monthly, with representative grab samples placed in plastic bags and stored at −20°C until the conclusion of each on-farm experiment, when laboratory analyses were performed.

Laboratory Analyses Diet samples from individual pens were composited on a monthly basis, which resulted in 4, 4, and 5 composite pen samples per month, respectively. Individual feedstuff samples were collected monthly and composited within dairy (minimum of 12 samples) and dried at 55°C in a forced-air oven (model SB-350, The Grieve Corporation, Round Lake, IL) for 48 h for DM determination. Dried samples were ground in a Wiley mill (Thomas Scientific, Swedesboro, NJ) to pass through a 2-mm screen. Basal feed ingredients and diet samples were analyzed for DM, ash, CP, fat, Ca, and P (procedures 930.15, 942.05, 988.05, 945.16, 968.08, and 965.17, respectively; AOAC, 1997). Acid detergent fiber and NDF were analyzed using a fiber analysis unit (Ankom Technology, Fairport, NY) with the reagents described in Goering and Van Soest (1970). A temperature-stable α-amylase (Validase HT 340L, Valley Research, South Bend, IN) was used for NDF analyses (Jeraci et al., 1988). Tabular results were derived from treatment diet composite sample analyses.

FA Analyses Composited diet samples were prepared for FA analysis via direct transesterification (Whitney et al., 2000) using methanolic HCl (Kucuk et al., 2001). Separation of FA methyl esters was achieved by GLC (model CP3800, Varian Inc., Palo Alto, CA) with a 100-m capillary column (SP-2560, Supelco, Bellefonte, PA) and H2 carrier gas at 1.0 mL/min. Oven temperature was maintained at 120°C for 2 min and increased to 210°C at 6°C/min. Oven temperature was then increased to 250°C at 5°C/min. Injector temperature was 260°C and flame-ionization detector temperature was 300°C. Identification of peaks was accomplished using purified standards (Sigma-Aldrich, St. Louis, MO; Nu-Chek Prep, Elysian, MN; Matreya, Pleasant Gap, PA). Fatty acids that were not identified were recorded and combined with C22:0, C22:1, and C22:0 and reported as “other.” Milk fat cake was isolated according to the method of Chouinard et al. (1999). Milk (30 mL) was centrifuged at 17,800 × g for 30 min at 8°C, followed by removal of the fat cake (Hara and Radin, 1978). For lipid extraction, 300 mg of fat cake was weighed in glass tubes (16 × 125 mm, Teflon-lined, screw-capped). Eighteen milliliters of hexane:isopropanol (3:2, vol/vol) per gram of fat was added, and contents were vortexed for 1 min


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Table 4. Fatty acid composition of treatment diets (CON and FLX) fed to early-lactation Holstein cows on 3 commercial dairies Dairy A Primiparous Item, g/100 g of fatty acid

Dairy B Multiparous

Primiparous

Multiparous

Dairy C2

CON

FLX

CON

FLX

CON

FLX

CON

FLX

CON

FLX

0.4 21.1 9.4 17.6 35.5 10.2 5.8 32.0 17.9 45.7 63.5 9.0

0.5 17.5 7.6 19.2 30.5 20.8 3.9 25.9 19.2 51.3 70.5 7.0

— 21.1 8.0 17.5 40.4 11.4 1.6 29.1 17.5 51.8 69.3 5.4

— 17.4 6.1 18.4 36.2 20.6 1.3 23.5 18.4 56.8 75.3 5.9

1.2 23.2 8.1 16.1 39.0 8.3 4.2 33.4 16.5 47.3 63.8 7.6

0.8 18.9 7.0 16.8 35.7 18.4 2.3 27.1 16.8 54.1 70.9 10.3

1.3 23.8 9.0 16.2 38.9 8.1 2.7 34.3 16.7 47.0 63.7 6.8

1.0 19.1 9.4 16.1 29.8 15.8 8.8 30.7 16.6 45.6 62.2 8.1

0.8 21.5 4.8 19.1 38.1 7.7 8.0 27.9 19.8 45.8 65.6 10.4

0.6 19.0 3.2 17.7 41.2 15.0 3.4 23.6 17.9 56.2 74.1 9.2

3

Fatty acid C14:0 C16:0 C18:0 Cis-9 C18:1 Cis-6 C18:2 C18:3n-3 Other SFA MUFA PUFA Total UFA4 Total fatty acids, g/100 g of DM 1

Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. Fatty acids not determined by peak identification using standards and fatty acids that represented, on average, less than 0.5% of total fatty acids were grouped and reported as other fatty acids. 3 Dairy C did not segregate cows by parity within treatment pens. 4 Total unsaturated fatty acids. 2

and allowed to sit for 10 min. Twelve milliliters of sodium sulfate per gram of fat was added and contents were vortexed for 1 min. The top hexane layer was removed and dried under N gas to produce the butter oil. A butterfat standard was methylated with each set of samples to determine the response factors for calculating relative percentages of FA within each sample. Fat (50 mg) was dissolved in hexane (2 mL) and methyl acetate (40 µL). Forty microliters of methylation solution (1.75 mL of anhydrous methanol + 0.4 mL of 5.4 M sodium methylate) was added, and contents were vortexed for 1 min and allowed to cool for 10 min. Oxalic acid (60 µL) was added to terminate the reaction, and then centrifuged for 5 min at 2,000 × g at 5°C. The top hexane layer was removed and placed in a gas chromatography vial. Fatty acids were analyzed by GLC (Chouinard et al., 1999).

August, and September through November. Pen nested within farm and treatment was a random effect and was used as the error term for treatment. Cows of different parities were not separated at dairy C. Initially, data for reproductive variables from dairies A and B were analyzed with parity included in the model. The result was nonsignificant (P > 0.55) for parity or interactions with parity. Therefore, all further analyses were conducted using data from all 3 dairy farms without parity in the model. Milk production, milk composition, and milk FA data were composites from cows within a pen; thus, pen was used as the experimental unit. Cow reproductive variables were obtained on individual cows so that cow was the sampling unit and pen was the experimental unit (St-Pierre, 2007). This method of analysis enables both the number of pens and the number of cows per pen to contribute to statistical power.

Statistical Analyses Cows that calved after initiation of the experiment and serviced cows that entered the experiment 45 d before the conclusion of the experiment were included in the analysis. The overall analysis included 1,484 cows. The number of cows that were recorded in each treatment pen varied because of inherent differences unique to each dairy farm for pen size and cows removed for management reasons. Data were analyzed using generalized least squares (PROC MIXED, SAS Inst. Inc., Cary, NC). The statistical model included dairy farm, treatment, the farm × treatment interaction, and season nested within farm. Season was defined as 4 quarterly periods of December through February, March through May, June through

RESULTS AND DISCUSSION Diets Diets were formulated to be as similar in CP and energy among dairies as possible. Within each dairy, cooperators attempted to minimize ingredient variation. Formulated CP ranged from 16.9 to 18.5%, and fat ranged from 5.0 to 6.0% (DM basis). Analyzed dietary CP ranged from 15.5 to 18.1%, and fat ranged from 3.4 to 5.0% (DM basis; Tables 1, 2, and 3). Forage:concentrate ratios ranged from 47.5:52.5 to 61.0:39.0. Fatty acid profiles for each dietary treatment are shown in Table 4. In general, C18:3n-3 was increased 2-fold for FLX diets compared with CON diets (6.77 vs. 12.37 g of C18:3n-3/100 g of FA, respectively).


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Table 5. Milk yield and milk composition (95% confidence interval) of early-lactation Holstein cows fed treatment1 diets with (FLX) or without (CON) rolled flaxseed on 3 commercial dairies Item No. of cows No. of pens Milk yield, kg/d Milk fat, % Milk fat yield, kg/d Milk protein, % Milk protein yield, kg/d

CON

FLX

SEM2

P-value

905 6 38.3 (32.8 to 43.7) 3.40 (3.24 to 3.57) 1.31 (1.07 to 1.55) 2.78 (2.68 to 2.87) 1.06 (0.89 to 1.24)

1,108 7 39.4 (34.3 to 44.4) 3.42 (3.27 to 3.57) 1.36 (1.13 to 1.25) 2.85 (2.76 to 2.93) 1.12 (0.96 to 1.29)

— — 2.5 0.08 0.11 0.04 0.08

— — 0.75 0.87 0.76 0.24 0.61

1 Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. 2 SEM for n = 6; n = 6 for CON, n = 7 for FLX.

Milk Components and Milk Production The average DIM for CON and FLX cows was not different (P > 0.95; 146 and 148 ± 21 d, respectively). Treatment did not affect peak milk, milk yield, milk fat concentration, milk fat yield, milk protein concentration, or milk protein yield for cows fed FLX vs. CON diets (P ≥ 0.24; Table 5). Most studies that have investigated feeding flaxseed to lactating dairy cows have reported no differences in milk yield (Petit, 2003; Gonthier et al., 2005; Fuentes et al., 2008). In lactating cows fed perennial ryegrass silage (Petit et al., 2001), milk production decreased for cows fed whole flaxseed treated with formaldehyde (18.6 kg/d; 10% ether extract, DM basis) when compared with cows supplemented with a combination of bypass supplemental fat and linseed meal (19.8 kg/d; 9.3% ether extract, DM basis). Petit (2002) reported that milk fat percentage was less for cows fed flaxseed (10%, DM basis) compared with cows that received Ca salts of palm oil; however, yield of 4% fat-corrected milk was not different. Fuentes et al. (2008) also reported a reduced milk fat percentage from lactating cows fed extruded flaxseed (5.5%, DM basis) compared with extruded soybeans. These authors attributed this effect to the dietary source of fat. Milk fat depression can occur if fat supplementation increases the synthesis of certain trans FA such as trans-10 C18:1 or trans-10, cis-12 C18:2 in ruminal fluid (Bauman and Griinari, 2003). However, in the present study, milk fat percentage was not different between treatments. The major factors contributing to the variation in milk protein are likely the method by which flaxseed was processed and the amount of flaxseed fed. Milk protein was reported to increase when flaxseed was fed whole compared with when it was treated with formaldehyde (Petit et al., 2001). Milk protein was not altered when flaxseed was fed in total mixed diets containing whole vs. rolled flaxseed (Khorasani and Kennelly, 1994). Moreover, Ward et al. (2002) reported a decrease in milk protein percentage and milk yield when feeding ground flaxseed compared with a control diet of similar

energy and CP on a DM basis, with no supplemental fat added.

Milk FA Profiles Milk FA profiles of composite milk samples are shown in Table 6. The proportion of C16:0 in composite milk samples was less for FLX cows (P = 0.03; Table 6) compared with CON cows. Our results are in agreement with those of Khorasani and Kennelly (1994), who reported a decrease in C16:0 FA in milk from cows fed either whole or rolled flaxseed. We also found an increase in the proportions of cis-9, trans-11 C18:2 (P = 0.04), C18:3n-3 (P = 0.06), and C20:0 (P = 0.01) FA and a decrease in C20:3n-6 FA (P = 0.03) in composite milk samples when FLX was fed. Our results agree with those of Petit et al. (2004), who found that C18:3 in milk was greatest for cows fed diets based on whole flaxseed (9.7% of dietary DM) when compared with cows consuming diets with Ca salts of palm oil, whole sunflower seed, or no fat supplement. Cows fed diets with flaxseed had an increased proportion of long-chain, C18:2, and C18:3n-3 FA in milk (Ambrose et al., 2006). Feeding flaxseed increased trans FA, which are intermediates in the ruminal biohydrogenation of SFA. The increase in C18:3n-3 in the composite milk samples in the present study is indicative of unsaturated linolenic acid escaping biohydrogenation in the rumen, thereby increasing n-3 FA in the composite milk samples. These results indicate that feeding diets formulated to provide 0.85 kg of DM/cow per day of FLX to dairy cows was sufficient to increase C18:3n-3 FA in milk. We further noted a decrease in medium-chain FA (P = 0.05) and an increase in long-chain FA (P = 0.08) for cows fed FLX. Total n-3 FA were increased (P = 0.07) and the n-6:n-3 ratio was decreased (P = 0.01) when FLX was included in the diet.

Reproductive Variables The effects of early-lactation cow diets with 0.85 kg of FLX/cow per day (DM basis) on reproductive vari-


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Table 6. Composite milk fat fatty acid composition of early-lactation Holstein cows fed treatment1 diets with (FLX) or without (CON) rolled flaxseed on 3 commercial dairies Item, % of total fatty acids

CON

FLX

SEM2

P-value

Fatty acid C4:0 C5:0 Unidentified C4 to C63 C6:0 C7:0 C8:0 C9:0 Unidentified C6 to C103 C10:0 C10:1n-1 C11:0 C12:0 C13:0 iso C14:0 C14:0 C14:1n-9 cis Unidentified C10 to C143 C15:0 iso C15:0 anteiso C15:0 C15:1 C16:0 iso C16:0 C16:1n-9 cis C16:2n-4 C17:0 iso C17:0 anteiso C17:0 C17:1 Unidentified C14 to C183 C18:0 C18:1 C18:2n-6 cis C18:2n-6 trans Trans-10, cis-12 C18:24 Cis-9, trans-11 C18:24 C18:3n-3 C18:3n-6 C19:0 C20:1 C20:0 C20:2 C20:3n-3 C20:3n-6 C20:3n-9 C20:4 C20:5 C21:0 C22:0 C22:1 C23:0 C24:0 Unidentified C18 to C243 Short-chain fatty acids5 Medium-chain fatty acids6 Long-chain fatty acids7 SFA MUFA PUFA Total n-3 Total n-6 Total n-9

5.39 0.04 0.15 2.61 0.03 1.40 0.04 0.02 2.90 0.27 0.06 3.33 0.10 0.08 10.37 0.92 0.28 0.95 0.09 0.27 0.02 28.30 0.19 1.37 0.03 0.45 0.20 0.33 0.15 1.02 10.88 22.05 2.21 0.06 0.06 0.39 0.52 0.05 1.59 0.01 0.06 0.02 0.02 0.11 0.02 0.09 0.08 0.02 0.05 0.02 0.01 0.01 0.33 16.09 43.80 38.35 69.79 24.81 3.67 0.55 3.01 22.10

5.23 0.04 0.16 2.60 0.03 1.40 0.04 0.03 2.90 0.27 0.06 3.31 0.10 0.09 10.35 0.93 0.30 0.93 0.09 0.26 0.03 27.02 0.17 1.30 0.03 0.43 0.20 0.29 0.14 0.87 11.31 22.22 2.17 0.10 0.06 0.41 0.69 0.05 2.49 0.01 0.07 0.02 0.02 0.09 0.02 0.08 0.07 0.02 0.05 0.02 0.02 0.02 0.47 15.86 42.36 39.91 69.46 24.91 3.83 0.71 3.11 22.28

0.09 0.01 0.01 0.03 0.01 0.02 0.01 0.01 0.08 0.01 0.01 0.09 0.01 0.01 0.12 0.03 0.04 0.01 0.01 0.01 0.01 0.37 0.01 0.04 0.01 0.01 0.02 0.02 0.01 0.19 0.19 0.87 0.07 0.03 0.01 0.01 0.06 0.01 0.80 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.04 0.23 0.46 0.58 0.88 0.86 0.14 0.05 0.12 0.87

0.23 0.96 0.66 0.73 0.64 0.91 0.75 0.60 0.93 0.99 0.73 0.90 0.49 0.38 0.87 0.92 0.71 0.37 0.96 0.45 0.51 0.03 0.21 0.18 0.79 0.17 0.91 0.27 0.44 0.56 0.13 0.88 0.60 0.33 0.77 0.04 0.06 0.93 0.42 0.12 0.01 0.66 0.70 0.03 0.83 0.94 0.75 0.45 0.88 0.72 0.40 0.70 0.03 0.50 0.05 0.08 0.78 0.93 0.42 0.07 0.55 0.88 Continued


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Table 6 (Continued). Composite milk fat fatty acid composition of early-lactation Holstein cows fed treatment1 diets with (FLX) or without (CON) rolled flaxseed on 3 commercial dairies Item, % of total fatty acids

CON

FLX

SEM2

P-value

5.95 0.44

4.63 0.47

0.31 0.01

0.01 0.09

n-6:n-3 Total CLA

1 Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. 2 SEM for n = 6; n = 6 for CON, n = 7 for FLX. 3 Fatty acids not determined by peak identification using standards were combined by chain length and reported as unidentified. 4 CLA. 5 Short-chain fatty acids (C4 through C12). 6 Medium-chain fatty acids (C13 through C17). 7 Long-chain fatty acids (≥C18).

ables are presented in Table 7. Treatment did not affect any of the reproductive variables measured, including days to first postpartum AI (P = 0.86), P/AI after first service (P = 0.86), days to second postpartum AI (P = 0.52), P/AI after second service (P = 0.55), combined P/AI after first and second service (P = 0.98), days open (P = 0.69), or pregnancy loss (P = 0.93). Collectively, the data reported thus far regarding the benefits to reproductive performance from feeding flaxseed to dairy cows are equivocal. For example, feeding flaxseed or linseed oil has been reported to affect several reproductive variables for dairy cows, including increased embryo quality (Thangavelu et al., 2007), decreased pregnancy loss (Ambrose et al., 2006), increased conception rate (Petit et al., 2001; Ambrose et al., 2006), increased follicular (Ambrose et al., 2006; Bilby et al., 2006) and corpus luteum (Petit and Twagiramungu, 2006) growth, reduced PGF2α synthesis (Petit et al., 2002), and increased serum progesterone (Lessard et al., 2003). By contrast, Ambrose et al.

(2006; no flaxseed vs. rolled flaxseed), Petit and Twagiramungu (2006; whole flaxseed vs. Ca salts of palm FA or micronized soybeans), Fuentes et al. (2008; extruded soybeans vs. extruded flaxseed), and Petit et al. (2008; whole flaxseed vs. Ca salts of palm FA) reported no improvements in conception rate when feeding extruded, rolled, and whole flaxseed to lactating dairy cows. Essential FA are classified as essential because cows are unable to synthesize them de novo; therefore, they must be obtained through the diet (Cook, 1996). A primary biological function of EFA is as a precursor to PG synthesis, and PGF2α is the luteolytic hormone in cattle. Alpha-linolenic acid (C18:3n-3) is the principal n-3 FA present in flaxseed (Chow, 1992) and is converted into eicosapentaenoic acid (C20:5n-3), and subsequently into docosahexaenoic acid (C22:6n-3; Cook, 1996). Fish oils, typically greater in concentrations of eicosapentaenoic acid and docosahexaenoic acid, reduced PGF2α secretion and improved conception rates when fed to dairy cattle (Mattos et al., 2000, 2004). Ambrose et al. (2006)

Table 7. Reproductive outcomes (95% confidence interval) of early-lactation Holstein cows fed treatment1 diets with (FLX) or without (CON) rolled flaxseed on 3 commercial dairies FLX

SEM2

P-value

3 6 635

3 7 849

68.3 (66.6 to 70.0) 84.0 (71.9 to 96.1) 33.3 (26.7 to 40.0) 29.3 (15.5 to 38.4) 47.5 (39.9 to 57.2) 133.6 (124.1 to 143.1) 4.0 (0.8 to 7.2)

68.4 (66.9 to 69.9) 79.3 (68.1 to 90.5) 34.0 (27.9 to 40.1) 26.1 (12.6 to 34.9) 47.5 (40.2 to 56.2) 131.5 (122.6 to 140.1) 3.9 (0.6 to 7.3)

— — — 0.7 5.1 2.8 3.9 3.5 4.0 1.6

— — — 0.86 0.52 0.86 0.55 0.98 0.69 0.93

Item No. of dairies No. of pens No. of cows Days to service First AI Second AI Pregnancies per AI,3 % First service Second service First and second service Days open Pregnancy loss,4 %

CON

1 Treatment: CON = control diet, no supplemental flaxseed; FLX = diet supplemented with rolled flaxseed at 0.85 kg of DM/cow per day. 2 SEM for n = 6; n = 6 for CON, n = 7 for FLX. 3 Percentage of pregnancies achieved per AI based on data for 1,484 cows. 4 Pregnancy loss from confirmed pregnancy to the pregnancy reconfirmation for cows diagnosed as pregnant for first and second AI services.


Fertility in dairy cows

reported a decrease in early embryonic loss (from 24 to 32 d after AI) for cows fed flaxseed and speculated this may have occurred through an attenuation of PGF2α secretion around the time of maternal recognition of pregnancy or through other embryotrophic mechanisms. Despite these and other findings, we were unable to detect an effect of feeding flaxseed on any of the reproductive variables measured in the present study, including conception rate and pregnancy loss.

Conclusion Milk from cows fed FLX diets on 3 commercial dairies had greater proportions of cis-9, trans-11 C18:2, C18:3n-6, and C20:0 FA in the milk fat and a lesser proportion of C16:0 compared with milk from cows fed CON diets. Replacing a portion of the diet with FLX did not alter milk yield, milk protein percentage, milk protein yield, milk fat percentage, and milk fat yield. Despite the modest increase in n-3 FA in composite milk samples, we detected no effect of feeding FLX on any of the reproductive variables evaluated in this experiment. We conclude that feeding 0.85 kg of FLX daily (DM basis) alters the FA profile of milk while maintaining milk yield and milk composition in an applied dairy setting. However, reformulation of diets to include 0.85 kg of FLX fed daily (DM basis) does not appear to affect the reproductive variables in lactating dairy cows that were measured in this study.

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