|Lekatz, Leslie - NDSU|
|Vonnahme, Kimberly - NDSU|
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 20, 2008
Publication Date: July 24, 2008
Citation: Scholljegerdes, E.J., Lekatz, L.A., Vonnahme, K.A. 2008. Effects of short-term oilseed supplementation on plasma fatty acid composition in lactating beef cows. Meeting Proceedings. Western Section American Society of Animal Science meetings, Laramie, WY, June 24-27, 2008. Proc. West. Sect. Amer. Soc. Anim. Sci. 59:308-313. Interpretive Summary: Feeding fat has been shown to improve reproductive parameters in beef cattle as well as increase the energy density of the diet. Key fatty acids from certain fat sources, such as linoleic and linolenic acid have also been reported to influence conception rates in cattle. Therefore our objectives were to evaluate the efficacy of a short-term increase in dietary energy and essential fatty acids around the time of AI until maternal recognition of pregnancy on plasma fatty acid concentrations over time in lactating beef cows grazing summer range. Twenty-four Angus cows were randomly allotted to one of three treatments being 1) grazing only and no supplement (CON); 2) grazing plus supplemental whole soybeans high in linoleic acid (WSB); or 3) grazing plus supplemental whole flaxseed high in linolenic acid (FLX). Supplementation started on the first day of estrus synchronization using a controlled intrauterine releasing device (CIDR®) plus timed AI and continued until maternal recognition of pregnancy for a total of 28 days of supplementation. Blood samples were collected every three days. Feeding whole soybeans and flaxseed increased plasma total fatty acid concentrations. However, there appeared to be a distinct lag phase regarding the amount of time it took for cattle fed flaxseed to exhibit higher levels of plasma fatty acids. Therefore, using whole soybeans during a short feeding period may improve reproductive success more so than whole flaxseed. Nevertheless, feeding either whole soybeans or whole flaxseed starting at the beginning of estrous synchronization will increase the supply of key fatty acids known to influence reproduction and improve animal energy status. Further investigation into the impact of these two oilseeds on reproductive success and hormone production is warranted.
Technical Abstract: Twenty-four three-year old Angus cows (512.2 ± 21.6 kg) and six ruminally cannulated beef heifers (523.1 ± 16.9 kg) were used to determine the impact of feeding oilseeds starting at the beginning of estrus synchronization until maternal recognition of pregnancy on plasma fatty acid composition. Starting approximately 60 d postpartum cows were synchronized with the Select Synch + CIDR® & timed AI protocol. The day CIDR® was inserted; cattle were randomly assigned to one of three treatments being grazing only (CON) or a supplement containing whole soybeans (WSB); or whole flaxseed (FLX). Supplements were formulated to provide similar quantities of N, TDN, and lipid. Cattle continued to receive these diets for 28 d. Blood was collected every three days until the end of the supplementation period and again on d 96 and 117. All cattle grazed a common pasture and supplemented cattle were individually fed their respective supplements once daily. Ruminally cannulated heifers were used to evaluate the impact our supplements had on forage intake, which was reduced (P = 0.05) with oilseed supplementation. Feeding oilseeds increased total fatty acid intake (P < 0.001) across treatments with WSB having greater (P < 0.001) 18:2n-6 intake than either CON or FLX. Likewise, cattle fed FLX had greater (P < 0.001) 18:3n-3 intake than either CON or WSB. There was a treatment × time interaction (P = 0.05) for all fatty acids identified except for 20:5n-3 (P = 0.99). Within 3 d after the start of supplementation, plasma concentrations of 18:2n-6 increased (P < 0.001) for cattle fed WSB compared to CON or FLX, whereas flax-fed cattle did not exhibit an increase (P = 0.02) until d 18 over that of CON. Whereas, plasma concentrations for 18:3n-3 was greater (P < 0.013) for FLX than both CON and WSB by d 18. Feeding flaxseed tended to (P = 0.065) increase and increased (P = 0.007) plasma concentrations of 20:4n-6 by d 18 over CON and WSB, respectively. Feeding oilseeds during the time of estrus synchronization will not only increase the energy density of the diet but will provide key fatty acids around the time of maternal recognition of pregnancy.