24 International Dairy Topics • Volume 16 Number 3

The intensive genetic selection for milkyield in past decades has led todecreased immunity, fertility and

longevity in the Holstein breed. Manycountries have improved their geneticevaluations of other traits than only milkproduction, and increased the weight ofhealth and fertility traits in the selectionprocess.

by Dr Hassan Taweel, Global BusinessDevelopment Manager Ruminants,

Nutriad, Belgium.www.nutriad.com

Despite this, poor health (hoof and udder),immunity and reproductive performanceare still among the most common causesfor replacing dairy cows. Modern high producing dairy cows suffer

severe negative energy balance during thefirst eight weeks after calving, which leadsto poor immunity and reproductionperformance. Also, poor hoof health andheat stress are implicated in reducingimmunity, fertility and reproductiveperformance in dairy cows.

The transition period

Many studies indicate that the immunesystem is not functioning at an optimallevel during the transition period (mainly

due to hormonal and metabolic changesbut also due to negative energy balance).Some studies showed that high producingdairy cows experience a decreasedmitogen-induced proliferation oflymphocytes and a decreased antibodyresponse. Other studies confirmed that during the

transition period cows experience adecreased chemotaxis and moleculeadhesion by neutrophils in addition to adecreased capacity of neutrophils to killpathogens.Fat has been used as an energy source to

increase energy density in rations,especially for early lactating cows.

However, fat (dependent on its type andcomposition) has also been found toinfluence rumen function, fibre digestion,intake and metabolic, hormonal andimmunological reactions. In recent years, polyunsaturated fatty

acids (PUFA) especially omega-6 (linoleicacid) and omega-3 (alfa linolenic acid) fattyacids have received attention because theyare classified as essential fatty acids (EFA)for dairy cows. Furthermore, there is emerging evidence

that PUFA may play a role in cow immunityand reproduction and hence improvefertility and longevity and reduce cullingand replacement rate.

Feeding essential fattyacids improves immunityand fertility in dairy cows

International Dairy Topics • Volume 16 Number 3 25

A number of studies have reportedenhanced reproductive performance indairy cows following dietarysupplementation with sources of omega-3FA. Several hypotheses about the mechanisms

through which dietary PUFA could enhancereproduction performance in dairy cattlehave been proposed.One of these hypotheses is that omega 3

FA influences steroidogenesis (i.e.progesterone) and alters the productionand release of prostaglandin F2α (PF2α)which causes regression of the corpusluteum (CL), improving conception andreducing embryo loss and detachment.Recent studies also concluded that feedingessential FA can modulate innate andadaptive cellular immunity, affectphagocytic activity and capacity ofleukocytes, and trigger a proinflammatoryresponse in high producing dairy cows.Some PUFA, such as linolenic acid (omega-

3) is a proven inhibitor of PGF2α secretionfrom the uterus, thereby reducing PGF2αconcentration and decreasing thesensitivity of the CL to PGF2α. This helpsprolong the life and functionality of the CLand allows it to increase progesterone (P4)concentrations. Higher pre-breeding concentrations of P4

have a positive impact on conception rates.Other PUFA such as linoleic acids (omega-6)are used preferentially bypolymorphonuclear leukocytes (PMN)which play a primary role immediatelypostpartum for the breakdown offoetal/maternal attachment, allowingfoetal membranes to be shed and expelled.This response is important to the timely

recovery of the uterus after calving. In afew studies involving large numbers ofcows, the overall pregnancy rate was higherand the number of services per conceptionwas lower (1.62 vs. 2.4) in cows fed highomega 3 rations compared to cows fed thecontrol diets. In many small reproductivephysiology studies using a hormonalexperimental protocol, cows fed omega-3

high rations had significantly lower plasmaPGF metabolites than the control cowsindicating a suppression of uterine PGF2α�release.A more recent study showed that

linolenic acid (omega-3) can reduce PGF2α�secretion by bovine endometrial cells underin-vitro conditions. In a Canadian animalexperiment with dairy cows, feedingformaldehyde treated or intact linseed(supplying omega-3 FA) from a few weeksafter calving improved conception rate,pregnancy rate to first AI and overallcumulative pregnancy rate. From the above it can be seen that

different PUFA are involved in thestimulation and/or inhibition of manyreproductive hormones and, hence, it isimportant to know which PUFA tosupplement to the cow at which stage ofthe reproduction cycle.A higher omega-6 to omega-3 ratio during

late gestation and early postpartum willmost likely improve calving ease and uterusrecovery and health, whereas a higheromega-3 to omega-6 ratio just before andduring breeding (insemination period) willmost likely improve conception rate,embryo survival rate and hence pregnancyrate.

Rumen microbe activity

One complicating factor is the activity ofrumen microbes that extensivelyhydrogenate dietary PUFA into manyintermediates and saturated fatty acids,making it difficult to estimate the type andamount of omega-6 and omega-3 that willbe absorbed into the bloodstream and beavailable for metabolism.Therefore, protecting PUFA from rumen

bio-hydrogenation is necessary tosuccessfully utilise them in reproductionmanagement programs. Nutriad’s coatedlinseed oil (Nutri-Flax) and fish oil (Nutri-Omega-3 FA) are effective sources ofprotected (rumen by-pass) omega-3 FA thatcan be used to increase omega-3 FAconcentration in blood and modulatereproductive hormones to improvefollicular and oocyte development andimprovements in fertility. In conclusion, essential fatty acids, mainly

linoleic (omega-6) and linolenic (omega-3)acids have direct effects on reproductivehormones, immune function andphysiological processes. Clearly, they areimportant to uterine health, embryoviability and the immune system. Targeted supplementation of protected

PUFA to the dairy cow during differentphases of the production cycle mayimprove immunity and reproductionperformance in dairy cows.For these positive results to be achieved,

the PUFAs must be protected from rumenbio-hydrogenation to make sure that theywill be absorbedinto the bloodstreamintact. n