Milk production, milk composition, blood composition, and conception rate of transition dairy cows fed different profiles of fatty acids

Abstract

A total of 153 lactating Holstein cows averaging 695 kg body weight (standard error = 11) were allotted 6 wk before the expected date of parturition to 51 groups of three cows blocked for similar calving dates to determine the effects of feeding different profiles of fatty acids from 6 wk before calving on feed intake, milk production and composition, conception rate, and embryo mortality in the subsequent lactation. Cows within each block were assigned to one of the three isoenergetic total mixed diets based on either whole flaxseed (FLA), Megalac® (MEG) or micronized soybeans (SOY). Diets were fed for ad libitum intake from 6 wk before calving to day 50 of pregnancy for pregnant cows, or 120 d postpartum for those not diagnosed pregnant after artificial insemination (AI). Diet had no effect on prepartum dry matter intake but postpartum intake was 9% higher for cows fed FLA than for those fed MEG or SOY. Milk production and fat concentration were similar among treatments. Conception rate at first AI was higher for cows fed FLA (54.3%) than for those fed SOY (26.9%). Conception rate at first AI was similar for cows fed FLA and MEG and it was similar for those fed MEG and SOY. Cows fed MEG tended to have higher embryo mortality than those fed FLA (41.7 vs. 10.5%, P = 0.06) and SOY (41.7 vs. 0%, P = 0.08) at first AI and there was no difference among treatments at second AI. Total embryo mortality was similar for cows fed FLA and SOY but cows fed MEG had higher total embryo mortality than those fed SOY (35.3 vs. 9.1%) and there was a trend (P = 0.07) when MEG was compared with FLA (35.3 vs. 9.5%). These data suggest that feeding flaxseed during the prepartum period has little effect on production in the subsequent lactation but could improve fertility of dairy cows. Key words: Dairy, flaxseed, milk production, reproduction, fatty acids