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Late Evening Artificial Insemination of Turkey Hens1
Late Evening Artificial Insemination of Turkey Hens1 KARL E. NESTOR and PHILIP A. RENNER Department of Poultry Science, Ohio Agricultural Research and Development Center, Wooster, OH 44691 (Received for publication January 13, 1982)
1982 Poultry Science 61:2496-2499 INTRODUCTION Wyne et al. ( 1 9 5 9 ) , using t u r k e y hens provided all-night lights, f o u n d t h a t t h e fertility resulting from artificial insemination at 1 3 0 0 and at 1 6 0 0 hr was similar and higher t h a n t h a t o b t a i n e d w h e n hens were inseminated at 0 9 0 0 hr. Presence of a hard-shelled egg in t h e u t e r u s at t i m e of artificial insemination significantly reduced fertility o n l y for h e n s inseminated at 1 3 0 0 hr. Christensen and J o h n s t o n ( 1 9 7 5 ) reported t h a t fertility of hens given 14 hr of light from 0 5 0 0 t o 1 9 0 0 h r and artificially inseminated at 1 8 0 0 h r was significantly greater t h a n t h e fertility of similar h e n s inseminated a t 0 8 0 0 , 1000, 1 3 0 0 , and 1 5 0 0 h o u r s . However, t h e fertility levels of t h e latter g r o u p s w e r e very low, ranging from 33 and 60%. In a later s t u d y , Christensen and J o h n s t o n ( 1 9 7 7 ) f o u n d t h a t inseminating hens at 2 1 0 0 or 2 4 0 0 h r resulted in m u c h higher fertility t h a n inseminating at 1 3 0 0 , 1 5 0 0 , 1 7 0 0 , and 1 8 0 0 hr. Again, t h e level of fertility was relatively low for t h e groups of hens inseminated from 1 3 0 0 t o 1 8 0 0 h r with a range from 66 t o 8 0 % . T h e r e w a s n o significant difference in fertility between t h e 1 5 0 0 , 1 7 0 0 , and 1800-hr inseminations. These w o r k e r s suggested t h a t fertility was highest w h e n inseminations were p e r f o r m e d 8 t o 18 h r prior t o oviposition, whereas lowest
1 Approved for publication as Journal Article No. 7-82 of the Ohio Agricultural Research and Development Center, Wooster, OH 44691.
fertility resulted w h e n hens were inseminated during t h e last 7 hr of shell deposition or at t h e a p p r o x i m a t e t i m e of ovulation. T h e purpose of this e x p e r i m e n t was t o c o m p a r e t h e influence of t i m e of artificial insemination u n d e r c o n d i t i o n s w h e r e fertility w o u l d b e e x p e c t e d t o b e high o r low.
MATERIALS AND METHODS F o u r trials were c o n d u c t e d t o s t u d y t h e effect of artificially inseminating t u r k e y hens at 0 8 0 0 , 1 1 0 0 , and 2 2 0 0 hr on fertility. Hens in all trials were given 1 4 hr of light from 0 3 0 0 t o 1 7 0 0 hr. In t h e first t h r e e trials, t h e same group of 2 4 males (42 weeks of age at start of experi m e n t ) was used t o provide pooled semen samples for insemination. In Trial 4, a group of males of t h e same age and strain as t h e females was used. Semen was collected M o n d a y , Wednesday, and Friday during t h e weeks of insemination. All semen collected o n any one d a y was used t o inseminate t h e hens assigned t o a single t i m e of insemination (Table 1). T h e order of insemination was changed each week t o avoid any c o m p o u n d i n g of possible effects of frequency of semen collection o n t i m e of insemination. Trials 1 and 2 w e r e c o n d u c t e d c o n c u r r e n t l y , and as a result, t h e same semen samples were used for b o t h trials. T o remove any possible influence of differences in semen collectors and inseminators, t h e same t w o persons collected t h e semen and did t h e inseminating in all trials. T h e a m o u n t of semen inseminated per hen was
2496
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
ABSTRACT Turkey hens were artificially inseminated at three times (0800, 1100, or 2200 hr) under conditions where high or low fertility would be expected. Four trials were conducted and the same two persons collected semen and inseminated the hens in all trials. Each hen was inseminated with .025 cc undiluted semen. There was no significant difference in fertility when hens were inseminated at different times of the day in the first three trials. In a fourth trial, where high fertility was expected, hens inseminated at 0800 hr had lower fertility than those inseminated at 2200 hr. There was no significant difference between inseminating at 0800 or 1100 hr and 1100 or 2200 hr. The results of this study indicate that late evening insemination is not necessary for high fertility. (Key words: fertility, insemination time, turkeys, hatchability)
LATE EVENING INSEMINATION OF TURKEYS
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TABLE 1. Artificial insemination schedule for the four trials
Trial
Time of insemination
Weeks of study 1
2
W F M
3
4
5
6
7
8
9
10
11
12
13
14
(hr) 0800 1100 2200
M1 W F
2
0800 1100 1200
W F M
F M W
M W F
W F M
F M W
3
0800 1100 1200
M W F
W F M
F M W
M W F
W F M
4
0800 1100 1200
M W F
1
W F M
F M W
M W F
F M W
M W F
F M W
W F M
W F M
M W F W F M
M W F
F M W
W F M
M W F
W F M
M, Monday; W, Wednesday; and F, Friday.
.025 cc. In all cases, insemination was completed within 1 hr after collection of semen. Eggs were set weekly. Fertility was estimated by candling on the seventh day of incubation. All apparently infertile eggs were broken and examined macroscopically for the presence of embryonic development. Details of the individual trials follow: Trial 1. Medium weight hens from a randombred control population (McCartney, 1964) were inseminated when the first egg was laid by the flock and again 1 week later. Biweekly inseminations were used thereafter for a 13-week reproduction period beginning 2 days after the second insemination. Trial 2. A sample of hens housed in individual laying cages from four strains selected for adaptation to a cage environment (Bacon and Nestor, 1982) were assigned to each treatment. There was no interaction between strain and artificial insemination treatment; only the effects of time of insemination will be presented. Biweekly inseminations were used throughout the 14-week reproduction period, which began the 2nd day after the Friday insemination and after the hens were in production for 8 weeks. Fertility by candling was zero, because 7 weeks had elapsed following the last insemination. Trial 3. Hens from a strain selected for increased egg production (Nestor, 1971) were housed in floor pens and assigned to artificial insemination treatments after they had been in
production for 12 weeks. The hens were last inseminated 5 weeks prior to the start of the trial, and fertility levels, based on candling, were near zero. Biweekly inseminations were used throughout the 10-week study. Trial 4. This trial was similar to Trial 1 except the hens were from the same strains as those in Trial 2. The individually caged hens were inseminated for 13 weeks. There was no interaction of strains and artificial insemination treatments. Fertility levels for Trials 1 and 4 would be expected to be high, because the hens were just beginning to lay and 2 weekly inseminations preceded the collection of eggs. However, fertility levels in Trials 2 and 3 were expected to be relatively low, because hens used in these trials has been in production for 8 and 12 weeks, respectively. Data for all trials were analyzed on a hen basis utilizing Harvey's least squares and maximum likelihood computer program (Harvey, 1977). Percentages were converted to angles by the arscin J percentage (Snedecor, 1959) prior to analysis. RESULTS AND DISCUSSION
Time of insemination did not have a significant influence on fertility in Trials 1,2, and 3 (Table 2). In Trial 4, inseminating hens at 0800 hr resulted in lower fertility (P<,01) than inseminating at 2200 hr. There were no signifi-
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
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NESTOR AND RENNER
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TABLE 2. Effect of artificially inseminating turkey bens at 0800, 1100, or 2200 hr on fertility
Trial1
Level of fertility expected
0800 hr
1100 hr
2200 hr
0800 hr
1 2 3 4
High Low Low High
18 ( 788) 2 45(1666) 21 ( 926) 47(2453)
19 ( 793) 45 (1826) 23 ( 953) 47(2514)
18 ( 700) 42(1518) 24 ( 959) 47 (2407)
94.2 64.0 77.0 86.6
% Fertility (mean ± SE)
No. of hens
± 1.53 ± 3.6 3 ±4.63 ± 1.5*b
1100 hr
2200 hr
96.2 ±1.0 69.5 ± 4 . 0 72.3 ± 4 . 7 91.3 ± l . l b c
94.4 + 74.1 ± 84.4± 93.7 ±
2.0 3.7 3.8 l.QC
' ' c Means within rows not followed by same letters are significantly different (P<.01). 1
Trials 1 and 2 were conducted at the same time using the same semen samples; Trials 3 and 4 were run independently. Number in parentheses indicates total number of eggs set.
3
There were no significant differences between treatments.
cant differences in fertility between inseminating at 0800 hr versus 1100 or 1100 hr versus 2200 hr. Although the differences were not statistically significant, fertility following insemination at 2200 hr was numerically greater than that after inseminations at 0800 and 1100 hr when the level of fertility was low (Trials 2 and 3). Egg production was not significantly affected by time of insemination. The results presented in Table 2 do not agree with the results of Christensen and Johnston (1975, 1977) when differences in the two lighting regimens are taken into account. The hens were given 14 hr of light from 0300 to 1700 hr in the present experiment and 0500 to 1900 hr in the experiments of Christensen and Johnston (1975, 1977). Thus, oviposition time would be expected to be about 2 hr earlier on the average in the present experiment. Relative to stage of egg formation, our 0800, 1100, and 2200-hr inseminations would correspond to
TABLE 3. Effect of artificially inseminating turkey bens at 0800, 1100, or 2200 hr on hatch of fertile eggs 1
Trial
0800 hr
1100 hr
2200 hr
1 2 3 4
87.0 67.7 75.6 76.3
83.3 73.7 71.5 79.6
81.1 68.5 73.6 80.4
1.9 3.4 2.7 2.2
± 2.7 ± 1.8 + 2.8 ± 2.2
Time of insemination had no significant influence on hatch of fertile eggs (Table 3). These results are not in agreement with Christensen and Johnston (1978) who found that artificial insemination at 1300 hr reduced hatch of fertile eggs when compared with insemination at 1500, 1700, 1800, 2100, and 2400 hr. REFERENCES
% Hatch of fertile eggs (mean ± SE)
± ± ± ±
those at 1000, 1300, and 2400 hr, respectively, of Christensen and Johnston (1975, 1977). The most notable differences involve the comparisons of late evening insemination versus those earlier in the day and the 1000 hr (0800 hr) versus 1300 hr (1100 hr) inseminations. Christensen and Johnston (1975,1977) observed significant differences among these comparisons whereas we observed no consistent differences even when the level of fertility was intentionally reduced by less frequent inseminations later in the laying period. The reason for the relatively low fertility obtained in the experiments of Christensen and Johnston was not given. With the exception of the groups inseminated during late evening, the fertility was much lower than expected with weekly inseminations.
± ± ± ±
3.6 3.0 2.2 1.8
1 There were no significant differences among treatments in any trial.
Bacon, W. L., and K. E. Nestor, 1982. Intermittent lighting and incage broodiness treatment for turkey hens in cages. Poultry Sci. 61:785—789. Christensen, V. L., and N. P. Johnston, 1975. The effect of time of day of insemination and oviposition on the fertility of turkey hens. Poultry Sci. 54:1209-1214. Christensen, V. L., and N. P. Johnston, 1977. Effect of time of day of insemination and the position of the egg in the oviduct on the fertility of turkeys. Poultry Sci. 56:458-462. Christensen, V. L., and N. P. Johnston, 1978. Effect
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
2
LATE EVENING INSEMINATION OF TURKEYS of time of day of insemination and stage of egg formation at insemination on hatchability. Proc. 16th World's Poultry Congr., Brazil. Vol. II: 187-196. Harvey, W. R., 1977. User's guide for LSML76 mixed model least-squares and maximum likelihood computer program. Ohio State Univ., Columbus, OH. McCartney, M. G., 1964. A randombred control population of turkeys. Poultry Sci. 43:739—744.
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Nestor, K. E., 1971. Genetics of growth and reproduction in the turkey. 3. Further selection for increased egg production. Poultry Sci. 50:1672— 1682. Snedecor, G. W., 1959. Statistical Methods. Iowa State Coll. Press, Ames, IA. Wyne, J. W., R. D. Carter, M. G. McCartney, and V. D. Chamberlin, 1959. Relation of time of insemination to fertility in the turkey. Poultry Sci. 38:828-831.
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
1982 Poultry Science 61:2496-2499 INTRODUCTION Wyne et al. ( 1 9 5 9 ) , using t u r k e y hens provided all-night lights, f o u n d t h a t t h e fertility resulting from artificial insemination at 1 3 0 0 and at 1 6 0 0 hr was similar and higher t h a n t h a t o b t a i n e d w h e n hens were inseminated at 0 9 0 0 hr. Presence of a hard-shelled egg in t h e u t e r u s at t i m e of artificial insemination significantly reduced fertility o n l y for h e n s inseminated at 1 3 0 0 hr. Christensen and J o h n s t o n ( 1 9 7 5 ) reported t h a t fertility of hens given 14 hr of light from 0 5 0 0 t o 1 9 0 0 h r and artificially inseminated at 1 8 0 0 h r was significantly greater t h a n t h e fertility of similar h e n s inseminated a t 0 8 0 0 , 1000, 1 3 0 0 , and 1 5 0 0 h o u r s . However, t h e fertility levels of t h e latter g r o u p s w e r e very low, ranging from 33 and 60%. In a later s t u d y , Christensen and J o h n s t o n ( 1 9 7 7 ) f o u n d t h a t inseminating hens at 2 1 0 0 or 2 4 0 0 h r resulted in m u c h higher fertility t h a n inseminating at 1 3 0 0 , 1 5 0 0 , 1 7 0 0 , and 1 8 0 0 hr. Again, t h e level of fertility was relatively low for t h e groups of hens inseminated from 1 3 0 0 t o 1 8 0 0 h r with a range from 66 t o 8 0 % . T h e r e w a s n o significant difference in fertility between t h e 1 5 0 0 , 1 7 0 0 , and 1800-hr inseminations. These w o r k e r s suggested t h a t fertility was highest w h e n inseminations were p e r f o r m e d 8 t o 18 h r prior t o oviposition, whereas lowest
1 Approved for publication as Journal Article No. 7-82 of the Ohio Agricultural Research and Development Center, Wooster, OH 44691.
fertility resulted w h e n hens were inseminated during t h e last 7 hr of shell deposition or at t h e a p p r o x i m a t e t i m e of ovulation. T h e purpose of this e x p e r i m e n t was t o c o m p a r e t h e influence of t i m e of artificial insemination u n d e r c o n d i t i o n s w h e r e fertility w o u l d b e e x p e c t e d t o b e high o r low.
MATERIALS AND METHODS F o u r trials were c o n d u c t e d t o s t u d y t h e effect of artificially inseminating t u r k e y hens at 0 8 0 0 , 1 1 0 0 , and 2 2 0 0 hr on fertility. Hens in all trials were given 1 4 hr of light from 0 3 0 0 t o 1 7 0 0 hr. In t h e first t h r e e trials, t h e same group of 2 4 males (42 weeks of age at start of experi m e n t ) was used t o provide pooled semen samples for insemination. In Trial 4, a group of males of t h e same age and strain as t h e females was used. Semen was collected M o n d a y , Wednesday, and Friday during t h e weeks of insemination. All semen collected o n any one d a y was used t o inseminate t h e hens assigned t o a single t i m e of insemination (Table 1). T h e order of insemination was changed each week t o avoid any c o m p o u n d i n g of possible effects of frequency of semen collection o n t i m e of insemination. Trials 1 and 2 w e r e c o n d u c t e d c o n c u r r e n t l y , and as a result, t h e same semen samples were used for b o t h trials. T o remove any possible influence of differences in semen collectors and inseminators, t h e same t w o persons collected t h e semen and did t h e inseminating in all trials. T h e a m o u n t of semen inseminated per hen was
2496
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
ABSTRACT Turkey hens were artificially inseminated at three times (0800, 1100, or 2200 hr) under conditions where high or low fertility would be expected. Four trials were conducted and the same two persons collected semen and inseminated the hens in all trials. Each hen was inseminated with .025 cc undiluted semen. There was no significant difference in fertility when hens were inseminated at different times of the day in the first three trials. In a fourth trial, where high fertility was expected, hens inseminated at 0800 hr had lower fertility than those inseminated at 2200 hr. There was no significant difference between inseminating at 0800 or 1100 hr and 1100 or 2200 hr. The results of this study indicate that late evening insemination is not necessary for high fertility. (Key words: fertility, insemination time, turkeys, hatchability)
LATE EVENING INSEMINATION OF TURKEYS
2497
TABLE 1. Artificial insemination schedule for the four trials
Trial
Time of insemination
Weeks of study 1
2
W F M
3
4
5
6
7
8
9
10
11
12
13
14
(hr) 0800 1100 2200
M1 W F
2
0800 1100 1200
W F M
F M W
M W F
W F M
F M W
3
0800 1100 1200
M W F
W F M
F M W
M W F
W F M
4
0800 1100 1200
M W F
1
W F M
F M W
M W F
F M W
M W F
F M W
W F M
W F M
M W F W F M
M W F
F M W
W F M
M W F
W F M
M, Monday; W, Wednesday; and F, Friday.
.025 cc. In all cases, insemination was completed within 1 hr after collection of semen. Eggs were set weekly. Fertility was estimated by candling on the seventh day of incubation. All apparently infertile eggs were broken and examined macroscopically for the presence of embryonic development. Details of the individual trials follow: Trial 1. Medium weight hens from a randombred control population (McCartney, 1964) were inseminated when the first egg was laid by the flock and again 1 week later. Biweekly inseminations were used thereafter for a 13-week reproduction period beginning 2 days after the second insemination. Trial 2. A sample of hens housed in individual laying cages from four strains selected for adaptation to a cage environment (Bacon and Nestor, 1982) were assigned to each treatment. There was no interaction between strain and artificial insemination treatment; only the effects of time of insemination will be presented. Biweekly inseminations were used throughout the 14-week reproduction period, which began the 2nd day after the Friday insemination and after the hens were in production for 8 weeks. Fertility by candling was zero, because 7 weeks had elapsed following the last insemination. Trial 3. Hens from a strain selected for increased egg production (Nestor, 1971) were housed in floor pens and assigned to artificial insemination treatments after they had been in
production for 12 weeks. The hens were last inseminated 5 weeks prior to the start of the trial, and fertility levels, based on candling, were near zero. Biweekly inseminations were used throughout the 10-week study. Trial 4. This trial was similar to Trial 1 except the hens were from the same strains as those in Trial 2. The individually caged hens were inseminated for 13 weeks. There was no interaction of strains and artificial insemination treatments. Fertility levels for Trials 1 and 4 would be expected to be high, because the hens were just beginning to lay and 2 weekly inseminations preceded the collection of eggs. However, fertility levels in Trials 2 and 3 were expected to be relatively low, because hens used in these trials has been in production for 8 and 12 weeks, respectively. Data for all trials were analyzed on a hen basis utilizing Harvey's least squares and maximum likelihood computer program (Harvey, 1977). Percentages were converted to angles by the arscin J percentage (Snedecor, 1959) prior to analysis. RESULTS AND DISCUSSION
Time of insemination did not have a significant influence on fertility in Trials 1,2, and 3 (Table 2). In Trial 4, inseminating hens at 0800 hr resulted in lower fertility (P<,01) than inseminating at 2200 hr. There were no signifi-
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
1
NESTOR AND RENNER
2498
TABLE 2. Effect of artificially inseminating turkey bens at 0800, 1100, or 2200 hr on fertility
Trial1
Level of fertility expected
0800 hr
1100 hr
2200 hr
0800 hr
1 2 3 4
High Low Low High
18 ( 788) 2 45(1666) 21 ( 926) 47(2453)
19 ( 793) 45 (1826) 23 ( 953) 47(2514)
18 ( 700) 42(1518) 24 ( 959) 47 (2407)
94.2 64.0 77.0 86.6
% Fertility (mean ± SE)
No. of hens
± 1.53 ± 3.6 3 ±4.63 ± 1.5*b
1100 hr
2200 hr
96.2 ±1.0 69.5 ± 4 . 0 72.3 ± 4 . 7 91.3 ± l . l b c
94.4 + 74.1 ± 84.4± 93.7 ±
2.0 3.7 3.8 l.QC
' ' c Means within rows not followed by same letters are significantly different (P<.01). 1
Trials 1 and 2 were conducted at the same time using the same semen samples; Trials 3 and 4 were run independently. Number in parentheses indicates total number of eggs set.
3
There were no significant differences between treatments.
cant differences in fertility between inseminating at 0800 hr versus 1100 or 1100 hr versus 2200 hr. Although the differences were not statistically significant, fertility following insemination at 2200 hr was numerically greater than that after inseminations at 0800 and 1100 hr when the level of fertility was low (Trials 2 and 3). Egg production was not significantly affected by time of insemination. The results presented in Table 2 do not agree with the results of Christensen and Johnston (1975, 1977) when differences in the two lighting regimens are taken into account. The hens were given 14 hr of light from 0300 to 1700 hr in the present experiment and 0500 to 1900 hr in the experiments of Christensen and Johnston (1975, 1977). Thus, oviposition time would be expected to be about 2 hr earlier on the average in the present experiment. Relative to stage of egg formation, our 0800, 1100, and 2200-hr inseminations would correspond to
TABLE 3. Effect of artificially inseminating turkey bens at 0800, 1100, or 2200 hr on hatch of fertile eggs 1
Trial
0800 hr
1100 hr
2200 hr
1 2 3 4
87.0 67.7 75.6 76.3
83.3 73.7 71.5 79.6
81.1 68.5 73.6 80.4
1.9 3.4 2.7 2.2
± 2.7 ± 1.8 + 2.8 ± 2.2
Time of insemination had no significant influence on hatch of fertile eggs (Table 3). These results are not in agreement with Christensen and Johnston (1978) who found that artificial insemination at 1300 hr reduced hatch of fertile eggs when compared with insemination at 1500, 1700, 1800, 2100, and 2400 hr. REFERENCES
% Hatch of fertile eggs (mean ± SE)
± ± ± ±
those at 1000, 1300, and 2400 hr, respectively, of Christensen and Johnston (1975, 1977). The most notable differences involve the comparisons of late evening insemination versus those earlier in the day and the 1000 hr (0800 hr) versus 1300 hr (1100 hr) inseminations. Christensen and Johnston (1975,1977) observed significant differences among these comparisons whereas we observed no consistent differences even when the level of fertility was intentionally reduced by less frequent inseminations later in the laying period. The reason for the relatively low fertility obtained in the experiments of Christensen and Johnston was not given. With the exception of the groups inseminated during late evening, the fertility was much lower than expected with weekly inseminations.
± ± ± ±
3.6 3.0 2.2 1.8
1 There were no significant differences among treatments in any trial.
Bacon, W. L., and K. E. Nestor, 1982. Intermittent lighting and incage broodiness treatment for turkey hens in cages. Poultry Sci. 61:785—789. Christensen, V. L., and N. P. Johnston, 1975. The effect of time of day of insemination and oviposition on the fertility of turkey hens. Poultry Sci. 54:1209-1214. Christensen, V. L., and N. P. Johnston, 1977. Effect of time of day of insemination and the position of the egg in the oviduct on the fertility of turkeys. Poultry Sci. 56:458-462. Christensen, V. L., and N. P. Johnston, 1978. Effect
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015
2
LATE EVENING INSEMINATION OF TURKEYS of time of day of insemination and stage of egg formation at insemination on hatchability. Proc. 16th World's Poultry Congr., Brazil. Vol. II: 187-196. Harvey, W. R., 1977. User's guide for LSML76 mixed model least-squares and maximum likelihood computer program. Ohio State Univ., Columbus, OH. McCartney, M. G., 1964. A randombred control population of turkeys. Poultry Sci. 43:739—744.
2499
Nestor, K. E., 1971. Genetics of growth and reproduction in the turkey. 3. Further selection for increased egg production. Poultry Sci. 50:1672— 1682. Snedecor, G. W., 1959. Statistical Methods. Iowa State Coll. Press, Ames, IA. Wyne, J. W., R. D. Carter, M. G. McCartney, and V. D. Chamberlin, 1959. Relation of time of insemination to fertility in the turkey. Poultry Sci. 38:828-831.
Downloaded from http://ps.oxfordjournals.org/ at University of Michigan on April 17, 2015