Effects of feeding treatedlinseed based supplement on various reproductive parameters are presented in Table3.
Improvement in reproductive parameter was observed in experiment group withregard 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 observedin experimental group as compare to control group and also days to conceptionafter initiation of trial was also differ significantly (P<0.05) amongst the groups (126.25 v/s 29.53days). As compare to control, conceptionrate has improved over 57.
55 per cent in experiment group. Increased conception rate was also observed byAmbrose et al(2006) and Petit et al (2008) after feeding flaxseed todairy cows. Increasing the dietaryavailability of n-3 PUFA during the postpartum period improved pregnancy ratesin cattle (Armstrong etal.
, 1990; Burke et al., 1997;Petit et al., 2001; Ambrose et al.
, 2002). Ferguson et al. (1990) observed a 2.2-fold increasedodds of becoming pregnant at first and all AI in lactating cows fed 0.5 kg/d offat. Similarly, grazing cows supplemented with 0.
35 kg of FA after the firstpostpartum 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 secretionby bovine endometrial cells (cells of the uterus) under in vitro conditionsAs uterine tissue is a primarysource of the F series prostaglandins (e.g., PGF2?) during the early postpartumperiod. In a normal, cycling, non-inseminated cow, the lifespan of the corpusluteum (CL) is about 16 days. Approximately 12 d after oestrus, low amplitudepulses of PGF secretion begin in the uterus of both cyclic and pregnant cattle.
This initial increase in PGF is followed by highamplitude 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 highamplitude pulsatile release of PGF is suppressed, allowing the continuedmaintenance of CL and pregnancy establishment. The suppression of PGF dependson a timely “signal (Interferon-tau)” from the developing embryo.
Interferon-tau has been recently identifiedas the primary embryonic signal that leads to maternal recognition of pregnancy(Thatcher et al. 1997). Embryosstart secreting interferon-tau in small quantities as early as Day 10,with increasing secretion as the conceptus elongates. However, secretion ofinterferon-tau in quantities sufficient to prevent the pulsatile releaseof 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 theirpresence 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 areturn to estrus.
However, an alternate means of suppressing PGF secretion, atleast temporarily, would give slow-growing embryos an increased time-window to”catch-up” and “signal” their presence, vastly increasing their chance ofsurvival. Upon conception, PGF2a must be prevented from regressing the CL inorder to maintain pregnancy (e.g., prevent early embryonic death).