Source: Dairy Research and Extension Consortium of Alberta
Why is this important?
Fatty acids can help improve energy balance and enhance reproduction
Due to their caloric density, dietary fats may reduce the harmful negative energy balance that commonly occurs at the beginning of lactation, improving reproductive performance. In addition, polyunsaturated long chain fatty acids like alpha-linolenic acid (ALA) seem to have a particularly beneficial effect on reproduction by reducing the synthesis of prostaglandin F2alpha and improving pregnancy rates.
What did we do?
Our study used 121 cows that were fed a total mixed ration containing either rolled flaxseed, which is high in ALA, or rolled sunflower seed, which is low in ALA to provide 750 g fat per day. Cows were on the diets from 28 days before to 32 days after breeding. After being synchronized for ovulation, cows were artificially inseminated. Blood progesterone was measured at 21 and 24 days after insemination to indirectly determine if they had conceived; pregnancy was confirmed by ultrasound 32 days after insemination. Cows that were not pregnant were re-inseminated 10 days later.
What did we find?
A flax-based ration may increase early embryo survival and reduce pregnancy losses Embryo survival in the fl ax-fed cows was higher in the first 24 days of pregnancy than in sunflower-fed cows (73 versus 48%). However, embryo survival between 24 and 32 days of gestation was about the same (67%) in both groups, indicating that the conception rate at 32 days in flax-fed cows (48 versus 32%) was due to differences during the early period of development. Pregnancy losses from conception to calving were lower in flax-fed cows than in sunflower-fed cows (10 versus 27%). See Figure 1.
Consequently, the flax-fed cows carried more calves to term than sunflower-fed cows. This may be because flax-fed cows ovulated larger follicles, which may have yielded more viable eggs than from smaller follicles of sunflower-fed cows.
It is important to note that cows were fed their respective rations for only about 4 weeks before and after artificial insemination. Therefore, flax supplementation for extended periods of time is probably not necessary to reap its benefits.
Ration affected milk composition and fatty acid concentration
Overall, milk yield or composition was not affected by the different rations. However, milk fat concentration (3.5 to 3.2%) and yield (1.3 to 1.1 kg/d) declined from week 0 to 4 after calving in cows fed sunflower seed. Both rations decreased medium chain fatty acids and increased long chain fatty acids in milk. In particular, flax-fed cows nearly tripled the amount of ALA in their milk, indicating that a substantial portion of the fatty acids in the flax ration escaped modifications in the rumen.
Flax in the ration did not decrease feed intake
Although the addition of fats in the ration can reduce dry matter intake, we found that intake was not affected by the inclusion of flaxseed. However, intake was slightly lower in cows fed sunflower seed. This difference did not affect body weight or body condition score, as both were relatively similar between the groups.
What does this mean?
The inclusion of flaxseed as a source of alphalinolenic acid in the rations of lactating dairy cows from 4 weeks before to 4 weeks after insemination increased early embryonic survival and reduce pregnancy losses.
• Feeding a flax-based ration for 4 weeks pre- and post-breeding can increase conception rates and reduce pregnancy losses in lactating dairy cows.
• Cows consuming a flax-based ration ovulated larger follicles, possibly yielding more eggs resulting in improved embryo survival.
• The economic benefits of this approach must be considered carefully because flaxseed could be expensive and relatively difficult to procure in local markets.
This research was supported by funds from Alberta Milk, Agriculture and Agri-Food Canada’s Matching Investment IniƟ aƟ ve, and Alberta Agriculture and Rural Development. The authors thank Pioneer Hi-Bred Limited, Schering Canada, and Vetoquinol Canada for product donaƟ ons. This research summary is based on a paper published in the Journal of Dairy Science (Ambrose et al. 2006. J Dairy Sci. 89: 3066-3074). For further informaƟ on please contact Dr. Divakar Ambrose at firstname.lastname@example.org