- 1. Fatty acids formulation: changes in nutritionists approach, questions to be answered
The aspects abovementioned are quite well-known by nutritionist, and do not constitute major concerns for them. On the contrary, nowadays lipids are not only perceived as providers of energy but also functional components of the diets with physiological and economic implications.
Due to this, nutritionists have started to consider formulating for specific fatty acids and their ratios (similarly to amino acids), as they have important implications in many aspects, such as the overall digestibility of the diet, rumen health, feed efficiency and other of increasing interest such as immunity and reproductive performance. However, there are no still recommendations for fatty acids in dairy.
On the one hand, palmitic acid has been proposed as interesting tool to increase milk fat%, and much of research has been carried out during the last years. On the other hand, unsaturated fatty acids are also on the spotlight, as improvers of milk fat composition (in the search for human health) and fertility rates. Also, their effects on immunity modulation is considered (although this point is nowadays more on the academic side).
Despite the increase in scientific knowledge regarding fatty acids along the past years (both saturated and unsaturated ones), a summary of such research must be carried out and conveyed to practitioners in a shorter and simpler manner that provides with the key useful information. In this sense, the present article is aimed at filling in these gaps of knowledge and help nutritionist in their daily job.
- 2. Omega-3 & Omega-6: functional fatty acids with effects on reproduction & immunity
Traditionally, the effects of lipids on reproduction were approached due to the energy provided by them (Energy Balance and body score). However, authors have demonstrated that fatty acids also play a role in physiological/metabolic pathways.
In this sense, Mattos et al. (2000) suggested that the positive effect of fat on fertility may not be due to improvement in energy balance of the cows but rather to the specific effect of some dietary fatty acids on the physiology of the hypothalamus hypophysis-ovary axis and even the uterus.
Dirandeh et al. (2012): studies have generally indicated that the PUFA of the omega-6 (linoleic acid) and omega-3 [a-linolenic acid; eicosapentaenoic (EPA), C20:5 omega-3; docosahexaenoic (DHA), C22:6 omega-3] families are the most beneficial to improving reproduction in cows.
N-3 families have generally shown to have an important effect on reproductive performance, which is due to the effect of Omega in the reduction of PGF2α concentrations. Because of the known luteolytic properties of PGF2α, a reduction in endometrial PGF2α secretion would favour the establishment and maintenance of pregnancy (Hallé et al., 2015). Thus, feeding supplements high in omega-3 (n-3) FA (e.g., linolenic acid, C18:3n-3) during the breeding season and early gestation has been reported to reduce uterine PGF2a production and improve embryo quality and pregnancy maintenance. Pregnancy rates may be increased by enhanced progesterone production and decreased embryo mortality (Santos et al., 2008; Silvestre et al., 2011; Hess et al., 2005).
2.1. Omega-6/Omega-3 ratio
Many nutritionists shifted their approach to a fatty-acids focused one. This makes that some of them are worried about n-6/n-3 ratio. In this sense, it is worthy to consider the values used by Kim et al. (2015): n-6/n-3 FA ratios of 2.07, 5.18 and 7.37. These authors assessed the effects of dietary n-6/n-3 fatty acid ratio on nutrient digestibility, blood metabolites and FA profile of Hanwoo heifers. In terms of digestibility and effects on rumen, they found that in vivo digestibility was not affected (P > 0.05) by dietary n-6/n-3 FA ratio, while in vitro dry matter digestibility and concentrations of total volatile fatty acids and propionate decreased (P < 0.05) linearly with increasing n-6/n-3 FA ratio. Regarding blood metabolites, they found that plasma insulin and progesterone increased linearly (P < 0.05), but linolenic acid and total n-3 FA decreased linearly (P < 0.05) with increasing n-6/n-3 ratio. Thus, the authors concluded that increasing the dietary n-6/n-3 FA ratio can increase the n-6/n-3 FA ratio in plasma and ruminal fluid as well as plasma progesterone secretion, which is related to fertility.
Hallé et al. (2015) also studied the effects of different n-6:n-3 ratios (4, 15 and 25), this time on gene expression and PG secretion in bovine different endometrial cells at the time of peri-implantation. The ratio 4 in combination with lignan enterolactone (ENL) resulted in the greatest reduction in PGF2α concentrations. Due to the known luteolytic properties of PGF2α, a reduction in endometrial PGF2α secretion would favour the establishment and maintenance of pregnancy.
The same year, Greco et al. (2015) evaluated the effects of altering the ratio between n-6 and n-3 fatty acids (FA) in the diet and the intake of these FA by 6-10 days in milk lactating dairy cows on lactation performance and inflammatory acute phase responses to a challenge with lipopolysaccharide (LPS). Diets were supplemented with a mixture of Ca salts of fish, safflower, and palm oils to create 3 different ratios of n-6 to n-3 FA (3.9, 4.9, or 5.9). Summary of results:
- DMI: Reducing the ratio of n-6 to n-3 FA increased dry matter intake (24.7, 24.6, and 26.1 (for 5.9, 4.9, and 3.9, respectively), with concurrent increases in milk production results:
- yields of 3.5% fat-corrected milk: 43.4, 45.4, and 48.0 kg/d
- milk fat: 1.53, 1.60, and 1.71 kg/d
- milk true protein: 1.24, 1.28, and 1.32 kg/d
- milk lactose: 2.12, 2.19, and 2.29 kg/d
- LPS challenge / Immunity:
- concentrations of IL-6 in plasma increased as the ratio of n-6 to n-3 FA increased (112.5, 353.4, and 365.1 pg/mL (for 3.9, 4.9, and 5.9, respectively)
- Haptoglobin concentration was greatest at 24 h after LPS challenge for cows fed 5.9
- body temperature and somatic cell count: were greater for cows fed 4.9 compared with those fed 3.9 or 5.9 (41.3, 40.8, and 40.8; 4.33, 3.68, and 3.58 × 106/mL), for R5, R4, and R6, respectively
- Phagocytosis and oxidative burst by neutrophils collected from circulation were unaffected by dietary treatment in the first 48 h after intramammary LPS infusion
These authors (Greco et al., 2015) concluded that supplying the same quantity of FA in the diet of early lactation dairy cows but altering the ratio of the polyunsaturated FA of the n-6 to n-3 families influenced lactation performance and inflammatory responses to an LPS challenge.
- 3. Conclusions and recommendations
Nowadays, it remains clear that nutrition has a transcendental effect on reproduction and immunity, in particular, essential fatty acids (Omega-3 and Omega-6). As a consequence, more novel are the approaches in which the functional effect of each fatty acid is already considered at the field level, and its perception is far from being mere contributors of energy (although they are also).
Of course, the supply of such fatty acids must be carried out at appropriate doses and ratios, as well as in the right period times (before/after parturition). In order to be precise, fatty acids protection level must be measured and ensured, due to ruminal biohydrogenation. Therefore, the development of protected Omega-3 and Omega-6 sources at the ruminal level are necessary to avoid reductions in food efficiency at the ruminal level and fat loss in milk. That is why NUTRION International, has a full range of this type of solutions, and is always willing to develop the solutions as our partners require.
This article was originally published in AFMA Matrix, July – Sept, Vol 27 No 3, pp. 21-23. Submitted by the author for its reproduction.
Article citation: A. J. Escribano. 2018. Omega fatty acids: Reproduction and immunity in dairy cows. AFMA Matrix, July – Sept, Vol 27 No 3, pp. 21-23