Effects by Ambrose et al (2006) and Petit

Effects of feeding treated
linseed based supplement on various reproductive parameters are presented in Table
3. Improvement in reproductive parameter was observed in experiment group with
regard to confirmation of pregnancy on account of protected omega fatty acid,
as only 20% cows become pregnant in control as compare to 78% in experiment. Significant
(P<0.05) reduction in artificial insemination per conception (AI/conception) was observed in experimental group as compare to control group and also days to conception after initiation of trial was also differ significantly (P<0.05) amongst the groups (126.25 v/s 29.53 days).  As compare to control, conception rate has improved over 57.55 per cent in experiment group.  Increased conception rate was also observed by Ambrose et al (2006) and Petit et al (2008) after feeding flaxseed to dairy cows.  Increasing the dietary availability of n-3 PUFA during the postpartum period improved pregnancy rates in cattle (Armstrong et al., 1990; Burke et al., 1997; Petit et al., 2001; Ambrose et al., 2002). Ferguson et al. (1990) observed a 2.2-fold increased odds of becoming pregnant at first and all AI in lactating cows fed 0.5 kg/d of fat. Similarly, grazing cows supplemented with 0.35 kg of FA after the first postpartum AI had greater pregnancy than unsupplmeneted controls (McNamara et al., 2003). Thatcher et al. (2001) provided evidence that EPA, DHA and ?-linolenic acid can reduce PGF secretion by bovine endometrial cells (cells of the uterus) under in vitro conditions As uterine tissue is a primary source of the F series prostaglandins (e.g., PGF2?) during the early postpartum period. In a normal, cycling, non-inseminated cow, the lifespan of the corpus luteum (CL) is about 16 days. Approximately 12 d after oestrus, low amplitude pulses of PGF secretion begin in the uterus of both cyclic and pregnant cattle. This initial increase in PGF is followed by high amplitude pulses of PGF-release by the uterus of cyclic (non-pregnant) animals, leading to regression of the CL. In the event of a pregnancy, the high amplitude pulsatile release of PGF is suppressed, allowing the continued maintenance of CL and pregnancy establishment. The suppression of PGF depends on a timely "signal (Interferon-tau)" from the developing embryo. Interferon-tau has been recently identified as the primary embryonic signal that leads to maternal recognition of pregnancy (Thatcher et al. 1997).  Embryos start secreting interferon-tau in small quantities as early as Day 10, with increasing secretion as the conceptus elongates. However, secretion of interferon-tau in quantities sufficient to prevent the pulsatile release of PGF secretion may not happen until the embryo acquires a filamentous form (that is, beyond Day 13). Because all embryos do not develop at the same rate, it is very likely that before slow-growing embryos get a chance to signal their presence through expression of interferon-tau in sufficient quantities, the high amplitude pulses of PGF may set-in, leading to regression of the CL, resulting in low plasma progesterone concentrations, pregnancy loss, and a return to estrus. However, an alternate means of suppressing PGF secretion, at least temporarily, would give slow-growing embryos an increased time-window to "catch-up" and "signal" their presence, vastly increasing their chance of survival. Upon conception, PGF2a must be prevented from regressing the CL in order to maintain pregnancy (e.g., prevent early embryonic death).