Abstract
Simple SummaryNowadays the need to optimize and maximize the productivity of dairy sheep leads farmers to plan lambing in specific periods in order to avoid economic loss due to nonproductive animals. The goal is to diagnose pregnancy at early gestation in order to minimize the costs of unproductive animals and to properly formulate rations for the energy requirements of gestating or lactating animals at the same time. Moreover, early pregnancy diagnosis, as well as the possibility of distinguishing between single and multiple gestations, enables farmers to plan the management of lambing well in advance thus minimizing manpower requirements. This study showed, for the first time, the plasmatic profile of PAG (pregnancy-associated glycoproteins) in Sarda and Lacaune ewes during gestation and the postpartum period using two different radioimmune assay (RIA) systems, thus enhancing our knowledge regarding PAG concentrations in domestic ruminants. Moreover, it showed that for both breeds these RIA systems are capable of distinguishing pregnant from nonpregnant ewes starting from day 18 of gestation. Furthermore, the rapid disappearance of PAG concentration following lambing did not require the use of a cut-off limit in postpartum animals as a means for detecting a new pregnancy.This study was carried out to determine ovine pregnancy-associated glycoprotein (oPAG) levels in the plasma of Sarda and Lacaune ewes throughout gestation and in the first month postpartum, using two heterologous radioimmunoassays (RIA-706 and RIA-srPool) and to study the correlations between PAG levels and fetal gender and number. On Day 18 of pregnancy, PAG concentrations were detected in 90.1% and 80.8% of Sarda pregnant ewes with RIA-706 and RIA-srPool, respectively; and in 90% and in 75% of Lacaune pregnant ewes with RIA-706 and RIA-srPool, respectively. From Day 30, PAG concentrations were detected in all pregnant ewes by using both RIA methods. In the postpartum period, the PAG concentrations in Sarda ewes decreased rapidly reaching minimal levels (<1 ng/mL) on day 28 using both RIA-706 and RIA-srPool. In Lacaune ewes, PAG-706 levels were higher than PAG-srPool from parturition until the last day of observation (Day 28 postpartum). It was also observed that mean concentrations were higher in multiple than in single pregnancies in Sarda and Lacaune ewes. Moreover, due to the rapid disappearance of PAG concentration following lambing, a cut-off limit in postpartum animals was not required as a means for detecting a new pregnancy.
Highlights
Nowadays the need to optimize and maximize the productivity of dairy sheep leads farmers to plan lambing in specific periods in order to avoid economic loss due to nonproductive animals.The goal is to diagnose pregnancy at early gestation in order to minimize the fodder wasted on unproductive animals and to properly formulate rations for the energy requirements of gestating or lactating animals at the same time
Over the past 30 years, techniques such as radioimmunoassay (RIA) for pregnancy detection have been developed using pregnancy-associated glycoproteins (PAGs) which are glycoproteins belonging to the aspartic proteinase family and are synthesized in the ruminant trophectoderm [1]
Thereafter there was a significant rise, which peaked at parturition. This is a similar trend to that described by Gajewski et al [46] for Berrichon ewes, by Ledezma-Torres et al [14] for various sheep breeds and by Ranilla et al [11,24] for Churra sheep, yet this trend was not observed for Merinos ewes whose
Summary
Nowadays the need to optimize and maximize the productivity of dairy sheep leads farmers to plan lambing in specific periods in order to avoid economic loss due to nonproductive animals.The goal is to diagnose pregnancy at early gestation in order to minimize the fodder wasted on unproductive animals and to properly formulate rations for the energy requirements of gestating or lactating animals at the same time. Nowadays the need to optimize and maximize the productivity of dairy sheep leads farmers to plan lambing in specific periods in order to avoid economic loss due to nonproductive animals. Early pregnancy diagnosis, as well as the possibility of distinguishing between single and multiple gestations, enables farmers to plan the management of lambing well in advance minimizing manpower requirements. In this regard, over the past 30 years, techniques such as radioimmunoassay (RIA) for pregnancy detection have been developed using pregnancy-associated glycoproteins (PAGs) which are glycoproteins belonging to the aspartic proteinase family and are synthesized in the ruminant trophectoderm [1]. 11 cDNA coding for distinct PAGs (ovPAG-1 to ovPAG-11) were identified at different gestational periods, confirming the multiplicity and temporal expression of PAG molecules in ruminant placenta [1,6,7,8,9,10]
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