uterine endometrial tissues were obtained by biopsy using a biopsy instrument 
 ( fujihira , tokyo , japan ) under caudal epidural anesthesia with 3 ml of 2% lidocaine 
 ( 2% xylocaine , fujisawa pharmaceutical , osaka , japan ) as described previously . the uterine endometrial tissue of the 
 intercaruncle region ( about 0.1 g ) was obtained from the middle section of 3 sections 
 of the uterine horns , which were equally divided on the longitudinal axis . the 
 tissues were weighed , frozen in liquid nitrogen and stored at 80 c. uterine endometrial tissue was processed by the method described previously   with a modification to increase the ratio of 
 tissue ( g ) to extraction solution ( ml ) from 1:5 to 1:15 . the egf concentrations in uterine extracts were determined by 
 a double - antibody sandwich eia using 96-well microtiter plates . anti - human egf mouse monoclonal antibody ( r & d systems , 
 minneapolis , mn , usa ) was used for solid - phase antibody , and anti - human egf rabbit 
 antiserum ( biogenesis , poole , uk ) was used for detection with anti - rabbit igg goat 
 antibody ( seikagaku , tokyo , japan ) labeled with peroxidase . the intra- and interassay cvs at 50 pg / well were 4.2 and 5.3% , 
 respectively . study 1 : clinically healthy , sexually mature , cyclic holstein heifers between 13 and 
 16 months of age that were housed in 4 commercial dairy farms were used to determine 
 a normal range of the endometrial egf concentrations . heifers were observed for 
 estrus ( day 0 ) twice daily , and endometrial tissues were obtained for egf assays by 
 biopsy on days 3 , 7 and 14 of the same estrous cycle . the normal ranges ( means  2 
 sd ) of endometrial egf concentrations on the 3 days were calculated using egf 
 concentrations of 84 fertile heifers that became pregnant by the artificial 
 insemination ( ai ) during the next 2 estrous cycles . repeat breeder holstein heifers were examined for endometrial egf concentrations on 
 days 3 , 7 and 14 to determine the incidence of alterations in the endometrial egf 
 profile . heifers that were clinically normal but had failed to conceive after 3 or 
 more ais without any abnormality in the cyclicity and in the genital organs according 
 to routine examinations by field practitioners were recruited for the study . all 
 animals were then examined by one of the authors for regularity of the estrous cycle , 
 time of ovulation ( < 48 h after onset of estrus ) , subclinical inflammation of the 
 uterus by cytology or histology and oviductal patency . fifty - three heifers at 18 to 
 26 months of age without any sign of abnormality by the examinations were used as 
 repeat breeders in the present study . an endometrial egf profile was judged as being 
 altered when egf concentrations on any of the 3 days were out of the normal 
 range . study 2 : sixty - four holstein and 56 japanese black heifers housed in 4 and 2 farms , 
 respectively , were recruited for the study 2 to examine the effects of parity and 
 type of cattle ( dairy and beef ) on the endometrial egf profile . the heifers had their 
 endometrial egf concentrations examined on day 3 and were subjected to ai at estrus 
 up to 2 times . the same animals were again examined for endometrial egf 
 concentrations on day 3 of the first estrous cycle , beginning after 60 days 
 postpartum , and then subjected to ais . measurement of the egf concentrations on day 3 
 was repeated until the third postpartum period ( i.e. , 4 times including the first 
 examination in heifers ) . animals were excluded from the study in any parity in which 
 they failed to conceive after the second ai after biopsy of the endometrial tissues 
 for egf assay . animals were also excluded from the study when they failed to show an 
 estrus by 90 days postpartum . the proportions of dairy and beef cattle remaining in 
 the study were compared by fisher s exact test . the effects of parity and type of 
 cattle were analyzed using 2-way anova with repeated measurement followed by 
 scheffe s test as a post hoc test . uterine endometrial tissues were obtained by biopsy using a biopsy instrument 
 ( fujihira , tokyo , japan ) under caudal epidural anesthesia with 3 ml of 2% lidocaine 
 ( 2% xylocaine , fujisawa pharmaceutical , osaka , japan ) as described previously . the uterine endometrial tissue of the 
 intercaruncle region ( about 0.1 g ) was obtained from the middle section of 3 sections 
 of the uterine horns , which were equally divided on the longitudinal axis . uterine endometrial tissue was processed by the method described previously   with a modification to increase the ratio of 
 tissue ( g ) to extraction solution ( ml ) from 1:5 to 1:15 . the egf concentrations in uterine extracts were determined by 
 a double - antibody sandwich eia using 96-well microtiter plates . anti - human egf mouse monoclonal antibody ( r & d systems , 
 minneapolis , mn , usa ) was used for solid - phase antibody , and anti - human egf rabbit 
 antiserum ( biogenesis , poole , uk ) was used for detection with anti - rabbit igg goat 
 antibody ( seikagaku , tokyo , japan ) labeled with peroxidase . the intra- and interassay cvs at 50 pg / well were 4.2 and 5.3% , 
 respectively . study 1 : clinically healthy , sexually mature , cyclic holstein heifers between 13 and 
 16 months of age that were housed in 4 commercial dairy farms were used to determine 
 a normal range of the endometrial egf concentrations . heifers were observed for 
 estrus ( day 0 ) twice daily , and endometrial tissues were obtained for egf assays by 
 biopsy on days 3 , 7 and 14 of the same estrous cycle . the normal ranges ( means  2 
 sd ) of endometrial egf concentrations on the 3 days were calculated using egf 
 concentrations of 84 fertile heifers that became pregnant by the artificial 
 insemination ( ai ) during the next 2 estrous cycles . repeat breeder holstein heifers were examined for endometrial egf concentrations on 
 days 3 , 7 and 14 to determine the incidence of alterations in the endometrial egf 
 profile . heifers that were clinically normal but had failed to conceive after 3 or 
 more ais without any abnormality in the cyclicity and in the genital organs according 
 to routine examinations by field practitioners were recruited for the study . all 
 animals were then examined by one of the authors for regularity of the estrous cycle , 
 time of ovulation ( < 48 h after onset of estrus ) , subclinical inflammation of the 
 uterus by cytology or histology and oviductal patency . fifty - three heifers at 18 to 
 26 months of age without any sign of abnormality by the examinations were used as 
 repeat breeders in the present study . an endometrial egf profile was judged as being 
 altered when egf concentrations on any of the 3 days were out of the normal 
 range . study 2 : sixty - four holstein and 56 japanese black heifers housed in 4 and 2 farms , 
 respectively , were recruited for the study 2 to examine the effects of parity and 
 type of cattle ( dairy and beef ) on the endometrial egf profile . the heifers had their 
 endometrial egf concentrations examined on day 3 and were subjected to ai at estrus 
 up to 2 times . the same animals were again examined for endometrial egf 
 concentrations on day 3 of the first estrous cycle , beginning after 60 days 
 postpartum , and then subjected to ais . measurement of the egf concentrations on day 3 
 was repeated until the third postpartum period ( i.e. , 4 times including the first 
 examination in heifers ) . animals were excluded from the study in any parity in which 
 they failed to conceive after the second ai after biopsy of the endometrial tissues 
 for egf assay . animals were also excluded from the study when they failed to show an 
 estrus by 90 days postpartum . the proportions of dairy and beef cattle remaining in 
 the study were compared by fisher s exact test . the effects of parity and type of 
 cattle were analyzed using 2-way anova with repeated measurement followed by 
 scheffe s test as a post hoc test . the endometrial egf concentrations of fertile and repeat breeder holstein heifers and 
 the calculated normal ranges are shown in table 
 1table 1 . endometrial egf concentrations ( ng / g of tissue weight ) in fertile and 
 repeat breeder holstein heifersgroup(n)days of the estrous cycle3714fertile * ( range)(84)11.5  2.6 ( 3.817.6)2.1  0.4 ( 1.33.0)12.5  2.8 ( 1.419.7)repeat breeders ( range)(53)11.3  2.1 ( 1.79.7)2.8  1.1 ( 1.32.7)13.1  2.4 ( 0.812.4)values are means  sd . * a normal range was determined by using endometrial 
 egf concentrations from 84 fertile holstein heifers that conceived within 2 
 ais after biopsy of the endometrial tissues . calculated normal ranges ( means 
  2  sd ) were 6.316.7 , 1.32.9 and 6.918.1 ng / g tissue weight on days 3 , 7 
 and 14 of the estrous cycle , respectively . five out of 53 repeat breeder 
 cows ( 9.4% ) showing egf concentrations lower than the normal range on days 3 
 and 14 were judged to have an altered egf profile .. endometrial egf concentrations were similar between fertile and repeat 
 breeder heifers on all 3 days of the estrous cycle . five ( 9.4% ) repeat breeder 
 heifers showed an altered egf profile with low egf concentrations on days 3 and 
 14 . values are means  sd . * a normal range was determined by using endometrial 
 egf concentrations from 84 fertile holstein heifers that conceived within 2 
 ais after biopsy of the endometrial tissues . calculated normal ranges ( means 
  2  sd ) were 6.316.7 , 1.32.9 and 6.918.1 ng / g tissue weight on days 3 , 7 
 and 14 of the estrous cycle , respectively . five out of 53 repeat breeder 
 cows ( 9.4% ) showing egf concentrations lower than the normal range on days 3 
 and 14 were judged to have an altered egf profile . twenty - eight ( 43.8% ) out of 64 holstein cattle and 47 ( 83.9% ) out of 56 japanese 
 black cattle remained in the study ; they became pregnant with up to 2 ais at 4 
 consecutive parities ( table 2table 2 . endometrial egf concentrations ( ng / g of tissue weight ) on day 3 at 
 different parities in holstein and japanese black cattlebreed(n)parity0123holstein(28)13.0  3.412.4  3.39.0  2.07.5  2.0japanese black(47)13.5  2.114.2  2.813.7  2.011.8 values with different letters within 
 the same type of cattle differ significantly ( p<0.05 ) . values with different letters within the same parity differ significantly 
 ( p<0.05 ) . ) . the proportion of animals remaining at the end of the study was 
 greater in japanese black than holstein cattle ( p<0.01 ) . in holstein cattle , 27 
 ( 42.2% ) and 9 ( 14.1% ) cattle were withdrawn by not conceiving with 2 ais and by being 
 culled for reasons other than fertility , respectively ( table 3table 3 . numbers of holstein cattle withdrawn in study 2 and reasons for 
 withdrawalparity0123remaining in the study at 
 indicated parity*61 ( 95.3)50 ( 78.1)35 ( 54.7)28 ( 43.8)withdrawn from the study at 
 indicated parity3 ( 4.7)11 ( 18.0)15 ( 30.0)7 ( 20.0)not conceived by the second ai3 ( 4.7)7 ( 11.5)11 ( 22.0)6 ( 17.1)mastitis0 ( 0)2 ( 3.3)2 ( 4.0)1 ( 2.9)accidents0 ( 0)2 ( 3.3)1 ( 2.0)0 ( 0)displacement of abomasum0 ( 0)0 ( 0)1 ( 2.0)0 ( 0 ) * percentage based on 64 virgin holstein heifers recruited for the study . 
  percentage based on the number of animals recruited for the 
 nulliparous heifers and based on the number of animals remaining in the 
 study at the previous parity for the primiparous and multiparous cows . one cow each was culled due to accidents at the second and 
 third parturitions . one cow at the first parity was culled due to hip 
 dislocation . ) . endometrial egf concentrations of animals that failed to conceive 
 with 2 ais from the nulliparous period to the third postpartum period were 7.8  1.4 , 
 6.2  1.9 , 5.6  1.9 and 4.8  1.7 ng / g tissue weight , respectively , and were lower 
 than those of the fertile population at comparable parities ( table 2 ) . in japanese black cattle , 2 , 1 , 3 and 3 cattle 
 were excluded from the study at each parity : from the nulliparous period to the third 
 postpartum period . all cattle , except for 2 cows that were culled due to accidents at 
 the first and third parturition , were excluded based on not conceiving with 2 
 ais . values with different letters within 
 the same type of cattle differ significantly ( p<0.05 ) . * percentage based on 64 virgin holstein heifers recruited for the study . 
  percentage based on the number of animals recruited for the 
 nulliparous heifers and based on the number of animals remaining in the 
 study at the previous parity for the primiparous and multiparous cows . one cow each was culled due to accidents at the second and 
 third parturitions . data from animals remaining at the end of the study were used to determine the 
 effects of parity and breed ( type ) of cattle on the egf profile in the fertile 
 population . all animals remaining at the end of the study had peak egf concentrations 
 on day 3 within the normal range at all parities . endometrial egf concentrations were 
 similar in holstein and japanese black heifers ( table 2 ) . however , the effect of parity on egf concentrations on day 3 was 
 different between holstein and japanese black cattle ( p<0.01 ) . in japanese black 
 cattle , egf concentrations remained high throughout the study period , while in 
 holstein cattle , egf concentrations decreased after the second calving . consequently , 
 the egf concentrations of holstein cattle were similar to those of japanese black 
 cattle in the nulliparous period and the first postpartum period and became lower 
 than those of japanese black in the second and third postpartum periods . accordingly , 
 the proportions of animals having egf concentrations at different levels were similar 
 between holstein and japanese black heifers ( fig . 1 . proportion of cattle with different levels of peak egf concentrations on 
 day 3 in the endometrium at each parity in fertile holstein ( left ) and 
 japanese black ( right ) cattle . ) . however , the proportion changed in holstein cows and became different from 
 that of japanese black cattle after the first parturition . proportion of cattle with different levels of peak egf concentrations on 
 day 3 in the endometrium at each parity in fertile holstein ( left ) and 
 japanese black ( right ) cattle . the endometrial egf concentrations of fertile and repeat breeder holstein heifers and 
 the calculated normal ranges are shown in table 
 1table 1 . endometrial egf concentrations ( ng / g of tissue weight ) in fertile and 
 repeat breeder holstein heifersgroup(n)days of the estrous cycle3714fertile * ( range)(84)11.5  2.6 ( 3.817.6)2.1  0.4 ( 1.33.0)12.5  2.8 ( 1.419.7)repeat breeders ( range)(53)11.3  2.1 ( 1.79.7)2.8  1.1 ( 1.32.7)13.1  2.4 ( 0.812.4)values are means  sd . * a normal range was determined by using endometrial 
 egf concentrations from 84 fertile holstein heifers that conceived within 2 
 ais after biopsy of the endometrial tissues . calculated normal ranges ( means 
  2  sd ) were 6.316.7 , 1.32.9 and 6.918.1 ng / g tissue weight on days 3 , 7 
 and 14 of the estrous cycle , respectively . five out of 53 repeat breeder 
 cows ( 9.4% ) showing egf concentrations lower than the normal range on days 3 
 and 14 were judged to have an altered egf profile .. endometrial egf concentrations were similar between fertile and repeat 
 breeder heifers on all 3 days of the estrous cycle . five ( 9.4% ) repeat breeder 
 heifers showed an altered egf profile with low egf concentrations on days 3 and 
 14 . values are means  sd . * a normal range was determined by using endometrial 
 egf concentrations from 84 fertile holstein heifers that conceived within 2 
 ais after biopsy of the endometrial tissues . calculated normal ranges ( means 
  2  sd ) were 6.316.7 , 1.32.9 and 6.918.1 ng / g tissue weight on days 3 , 7 
 and 14 of the estrous cycle , respectively . five out of 53 repeat breeder 
 cows ( 9.4% ) showing egf concentrations lower than the normal range on days 3 
 and 14 were judged to have an altered egf profile . twenty - eight ( 43.8% ) out of 64 holstein cattle and 47 ( 83.9% ) out of 56 japanese 
 black cattle remained in the study ; they became pregnant with up to 2 ais at 4 
 consecutive parities ( table 2table 2 . endometrial egf concentrations ( ng / g of tissue weight ) on day 3 at 
 different parities in holstein and japanese black cattlebreed(n)parity0123holstein(28)13.0  3.412.4  3.39.0  2.07.5  2.0japanese black(47)13.5  2.114.2  2.813.7  2.011.8 values with different letters within 
 the same type of cattle differ significantly ( p<0.05 ) . values with different letters within the same parity differ significantly 
 ( p<0.05 ) . ) . the proportion of animals remaining at the end of the study was 
 greater in japanese black than holstein cattle ( p<0.01 ) . in holstein cattle , 27 
 ( 42.2% ) and 9 ( 14.1% ) cattle were withdrawn by not conceiving with 2 ais and by being 
 culled for reasons other than fertility , respectively ( table 3table 3 . numbers of holstein cattle withdrawn in study 2 and reasons for 
 withdrawalparity0123remaining in the study at 
 indicated parity*61 ( 95.3)50 ( 78.1)35 ( 54.7)28 ( 43.8)withdrawn from the study at 
 indicated parity3 ( 4.7)11 ( 18.0)15 ( 30.0)7 ( 20.0)not conceived by the second ai3 ( 4.7)7 ( 11.5)11 ( 22.0)6 ( 17.1)mastitis0 ( 0)2 ( 3.3)2 ( 4.0)1 ( 2.9)accidents0 ( 0)2 ( 3.3)1 ( 2.0)0 ( 0)displacement of abomasum0 ( 0)0 ( 0)1 ( 2.0)0 ( 0 ) * percentage based on 64 virgin holstein heifers recruited for the study . 
  percentage based on the number of animals recruited for the 
 nulliparous heifers and based on the number of animals remaining in the 
 study at the previous parity for the primiparous and multiparous cows . 
  one cow each was culled due to accidents at the second and 
 third parturitions . one cow at the first parity was culled due to hip 
 dislocation . ) . endometrial egf concentrations of animals that failed to conceive 
 with 2 ais from the nulliparous period to the third postpartum period were 7.8  1.4 , 
 6.2  1.9 , 5.6  1.9 and 4.8  1.7 ng / g tissue weight , respectively , and were lower 
 than those of the fertile population at comparable parities ( table 2 ) . in japanese black cattle , 2 , 1 , 3 and 3 cattle 
 were excluded from the study at each parity : from the nulliparous period to the third 
 postpartum period . all cattle , except for 2 cows that were culled due to accidents at 
 the first and third parturition , were excluded based on not conceiving with 2 
 ais . values with different letters within 
 the same type of cattle differ significantly ( p<0.05 ) . percentage based on the number of animals recruited for the 
 nulliparous heifers and based on the number of animals remaining in the 
 study at the previous parity for the primiparous and multiparous cows . one cow each was culled due to accidents at the second and 
 third parturitions . data from animals remaining at the end of the study were used to determine the 
 effects of parity and breed ( type ) of cattle on the egf profile in the fertile 
 population . all animals remaining at the end of the study had peak egf concentrations 
 on day 3 within the normal range at all parities . endometrial egf concentrations were 
 similar in holstein and japanese black heifers ( table 2 ) . however , the effect of parity on egf concentrations on day 3 was 
 different between holstein and japanese black cattle ( p<0.01 ) . in japanese black 
 cattle , egf concentrations remained high throughout the study period , while in 
 holstein cattle , egf concentrations decreased after the second calving . consequently , 
 the egf concentrations of holstein cattle were similar to those of japanese black 
 cattle in the nulliparous period and the first postpartum period and became lower 
 than those of japanese black in the second and third postpartum periods . accordingly , 
 the proportions of animals having egf concentrations at different levels were similar 
 between holstein and japanese black heifers ( fig . proportion of cattle with different levels of peak egf concentrations on 
 day 3 in the endometrium at each parity in fertile holstein ( left ) and 
 japanese black ( right ) cattle . ) . however , the proportion changed in holstein cows and became different from 
 that of japanese black cattle after the first parturition .   proportion of cattle with different levels of peak egf concentrations on 
 day 3 in the endometrium at each parity in fertile holstein ( left ) and 
 japanese black ( right ) cattle . alterations in the endometrial egf profile are found in about 70% of multiparous repeat 
 breeder holstein cows , and these abnormalities 
 have been linked to reduced fertility in lactating multiparous holstein repeat breeder 
 and apparently normal cows . however , the 
 incidence of the altered egf profile in repeat breeder holstein heifers , which was 
 determined based on the egf concentrations on day 3 in the present study , was about 10% . this low incidence of the altered egf profile in repeat breeder holstein heifers 
 suggests that alterations in the endometrial egf profile may be less important as a 
 cause of reduced fertility in repeat breeder holstein heifers . this may also partially 
 explain a lower incidence of repeat breeding in heifers than lactating multiparous 
 holstein cows . the present study also demonstrated a clear difference between holstein ( dairy ) and 
 japanese black ( beef ) cattle in the effect of parity on the endometrial egf profile . the 
 egf concentrations on day 3 of the first estrous cycle starting after 60 days postpartum 
 were consistently high up to the third postpartum period in japanese black cattle , while 
 the peaks decreased in holstein cattle after the second parturition . the present study 
 was carefully designed to select fertile animals by using animals that conceived by the 
 first and second ai after biopsy of the endometrium at the every parity . this design 
 largely reduced the number of animals , especially in dairy cattle , but allowed us to 
 conclude that , even in the fertile population , peak concentrations of endometrial egf 
 decreased at the time when lactating holstein cows were subjected to ai for the first 
 time after parturition . lactating dairy cows with an advanced parity may take a longer 
 period to return the peak egf concentrations to the levels found in heifers than dairy 
 cows with lower numbers of parities and beef cows with similar parities . alternatively , 
 some physiological changes associated with high levels of lactation and repeated 
 parturition may prevent the peak egf concentrations from making a full recovery . it is 
 of interest to examine how and when the peak egf concentrations are restored after 
 parturition to the levels found in heifers in lactating dairy cows . a low incidence of alterations in the egf profile in repeat breeder holstein ( dairy ) 
 heifers and japanese black ( beef ) cows may give us insights into the etiology of the 
 alteration in the endometrial egf profile . a number of studies of repeat breeder cows 
 have shown endocrine disorders in the periovulatory and metestrus periods . some of these changes are also found in 
 high - producing cows and have been linked to reduced fertility . in the periovulatory period , a slow rise and low peak of plasma 
 estradiol concentrations and a delayed lh surge have been found in repeat breeder [ 12 , 13 ] and 
 high - producing cows [ 12 , 13 ] . in metestrus , a slow rise and low plasma progesterone level 
 have also been described in repeat breeders [ 12 , 
 14 , 15 ] . in high - producing cows , disorders in the ovarian steroid hormone 
 environment during the periovulatory period have been attributed to increased clearance 
 of steroid hormones from the circulation , due to an increased blood flow to the liver 
 resulting from high food intake for high levels of milk production . these changes in the ovarian steroid 
 environment during the periovulatory period may cause a loss or decrease in the egf peak 
 levels in lactating dairy cattle because synthesis of egf is regulated by estrogen and 
 progesterone in the endometrium . treatment with a high dose of 
 estradiol benzoate ( 5 mg ) with an intravaginal progesterone device normalized egf 
 profiles and restored fertility in lactating repeat breeder holstein cows . plasma progesterone concentrations on day 5 , but 
 not at peaks , correlated with peak egf concentrations on days 3 and 14 . these findings have been interpreted to mean that 
 insufficient stimulation of the uterine endometrium by estrogen and progesterone at 
 estrus and metestrus , respectively , may be primary causes of alterations in the egf 
 profile . however , some of these changes in endocrine disorders have also been found in repeat 
 breeder heifers . the degree and/or incidence 
 of the alteration in the steroid hormone environment in lactating cows may be greater 
 than those in heifers , or loss of the egf peak may require some factors or physiological 
 changes that are associated with high levels of lactation and parturition , in addition 
 to disorders in the ovarian steroid hormone environment . in study 2 , this study 
 design was employed after our experience in the diagnosis of the endometrial egf 
 profiles in more than 1000 cows [ 5,6,7 , 10 ] by measuring egf concentrations on days 3 , 7 and 
 14 of the estrous cycle . in fertile cattle , endometrial egf concentrations show 2 peaks , 
 on days 24 and days 1314 , with low concentrations of egf around day 7 . alterations of 
 the endometrial egf profile in lactating repeat breeder holstein cows can be 
 characterized by the absence of the 2 peaks in the egf concentrations . few cows show an alteration in egf concentrations 
 around day 7 , at which point the endometrial egf concentrations show a basal level . importantly , cows losing the first peak on days 24 also lose the second peak on days 
 1314 . about 85 and 10% of cows having low egf peaks on day 3 have the egf 
 concentrations below or slightly above ( within 0.5 ng / g tissue weight ) , respectively , 
 the lower limit of the normal range on day 14 ( 4.9 ng / g tissue weight ) . accordingly , egf concentrations on day 3 have 
 been shown to be a good marker of fertility after embryo transfer in beef and dairy 
 cows . in our previous study , a total of 437 
 cows were examined for endometrial egf concentrations on day 3 and were transferred an 
 embryo on day 7 of the same cycle . recipient cows having egf concentrations within a 
 normal range on day 3 had a greater conception rate ( 76.9% ) than those with low egf 
 concentrations ( 33.3% ) . thus , a single examination of endometrial egf concentrations on 
 day 3 could be used in place of a complete examination of the egf profile , with 
 concentrations determined on days 3 , 7 and 14 . this finding may provide a great 
 advantage when one wants to use the measurement of endometrial egf concentrations as a 
 tool to diagnose repeat breeder cows under field conditions because repeated biopsy is 
 time- and labor - intensive for practitioners .
abstract a high incidence ( about 70% ) of alteration in endometrial epidermal growth factor 
 ( egf ) profile , i.e. , loss of 2 peaks on days 24 and 1314 , has been linked to a 
 reduced fertility in multiparous repeat breeder holstein cows . however , the egf 
 profile in holstein heifers and other breeds ( types ) of cattle has not been 
 investigated . in study 1 
 , egf concentrations were determined using endometrial 
 tissues obtained by biopsy on days 3 , 7 and 14 from 84 fertile holstein heifers to 
 obtain a normal range and 53 repeat breeder holstein heifers to estimate incidence of 
 alterations in the egf profile . in repeat breeder heifers , 
 egf concentrations were 
 similar to fertile controls on 3 days and five animals ( 9.4% ) had an altered egf 
 profile with egf concentrations below the normal range on days 3 and 14 . in study 2 , 
 egf concentrations on day 3 were repeatedly examined from the nulliparous period to 
 the third postpartum period in 28 holstein ( dairy ) and 47 japanese black ( beef ) 
 cattle . 
 the effect of parity on egf concentrations on day 3 was different between 
 holstein and japanese black cattle . 
 in japanese black cows , the egf concentrations 
 were consistently high throughout the study period , while in holstein cows , the egf 
 concentrations decreased after the second calving . in conclusion , unlike multiparous 
 repeat breeder holstein cows , an altered egf profile may not be a major cause of 
 repeat breeding in holstein heifers , and the peak egf concentrations around day 3 may 
 decrease even in fertile populations of multiparous dairy cows , but not in beef 
 cows .