by Chelsey Saevre, Cow/Calf Field Technical Support and Mike Jarosz, Technical Services
Reproductive performance is the largest determinant of income in a cow/calf enterprise. Maternal nutrition plays a critical role in reproductive physiology, including hormonal production, oocyte quality, fertilization and embryonic development. Proper body condition score at calving has been shown to influence pregnancy rates and postpartum interval. Improper dietary energy intake and poor body condition can negatively affect reproductive function (Funston, 2014).
Supplemental fat has been used to increase the energy density of the diet to overcome poor energy content of available feedstuffs. With forage based diets, it is recommended to include supplemental fat at ≤2% dry matter intake to maximize the energy component of fat without jeopardizing fiber digestion. It would also appear that a positive response to fat supplementation likely occurs if cows are in thin condition. Whereas, there is limited benefit of fat supplementation in females of adequate condition (Funston, 2014).
Aside from energy contribution, fat may play a positive role on reproduction by impacting specific tissues responsible for maintaining pregnancy. The target tissue and reproductive response appears to be dependent upon the fatty acid profile of the fat source (Funston 2014). Fats containing elevated levels of especially omega-3 fatty acids such as flaxseed or fish oil and to a lesser extent fats with omega-6 fatty acids (i.e. oils from soybeans, sunflower seeds, corn germ, safflower seeds, etc.) may have the greatest chance for a positive impact on reproduction. Silvestre, et al., 2011 fed various ratios of omega-6 to omega-3 fatty acids to dairy cows pre-calving through 160 days post calving. They found the best reproductive response by feeding increasing levels of omega-3, or lowering the omega-6 to 3 ratio. The response was primarily a decrease in early embryonic death the first 60 days of gestation. Studies suggest feeding cattle diets rich in omega-3 and omega-6 fatty acids improve circulating reproductive hormone concentrations, creating a heathy uterine environment for embryonic survival (Petit et al., 2002).
The form at which the fats are fed can also play a role in potential reproductive benefits. Santos et al., 2013 estimates up to 80% of poly unsaturated fats are bio-hydrogenated or altered by the rumen microorganisms, which changes the specific fatty acids absorbed into the blood to be metabolized. Glasser et al., 2008 fed rolled linseed versus linseed oil to dairy cows and found less bio-hydrogenated fatty acids in the rumen when fed the rolled linseed versus the oil. Suggesting the rolled linseed was more protected from rumen microorganisms likely getting more of the intact fatty acids absorbed with a greater chance to influence hormone production, etc. Calcium salts of fatty acids are even more rumen protected suggesting they have even a greater chance to get the fatty acids absorbed intact.
Timing of fat supplementation is also important, several studies have demonstrated improvements in reproductive performance with fat supplementation during late pregnancy. Hess et al. (2005) summarized research on supplementing fat 60 days prior to calving improved ovarian follicular growth and key reproductive hormones. Additionally, there was a 6.4% improvement in pregnancy rate.
Supplementing fat postpartum appears to be of limited benefit (Funston, 2004). Beef cows supplemented with fat after calving exhibited increased ovarian follicular growth and development as well as enhanced luteal activity. However, fat supplementation did not improve postpartum interval or conception rates.
Data would suggest that strategically providing a level of rumen protected fat to deliver approximately 0.25-0.33 lb/hd/d of omega-3 rich fat or approximately twice as much omega-3 rich unprotected oil to thin beef cows 30 days prior to calving through breeding may elicit a positive reproductive response. Otherwise, a practical fat supplementation strategy may be to provide additional fat during late gestation until the beginning of breeding. Keeping in mind the feed costs and the importance of maintaining or improving reproductive efficiency as a key to producer profitability.
Funston, R.N. 2004. Fat supplementation and reproduction in beef females. J. Anim. Sci. 82(E. Suppl.):E154-E161.
Funston, R.N. 2014. Importance of early conception and factors influencing it. The State of Beef Conference Proceedings.
Glasser, M., M. Doreau, S. Laverroux, J. Normand, and G. Chesneau. 2008. Effect of Linseed Fed as Rolled Seeds, Extruded Seeds or Oil on Fatty Acid Rumen Metabolism and Intestinal Digestibility in Cows.
Hess, B.W., S. L. Lake, E. J. Scholljegerdes, T. R. Weston, V. Nayigihugu, J. D. C. Molle, and G. E. Moss. 2005. Nutritional controls of beef cow reproduction. J. Anim. Sci. 83(E. Suppl.):E90–E106
Santos, J.E, L.F. Greco, M. Garcia, W.W. Thatcher, and C. R. Staples. 2013. The Role of Specific Fatty Acids on Dairy Cattle Performance and Fertility. 24th Annual Ruminant Nutrition Symposium.
Silvestre., F. T., T.S. Carvlho., N. Francisco, JE. Santos, C.R. Staples, T.C. Jenkins, W.W. Thatcher. 2011. Effects of differential supplementation of fatty acids during the peripartum and breeding periods of Holstein cows: I. Uterine and metabolic responses, reproduction, and lactation. J. Dairy Sci. Jan;94(1)189-204.