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Synchronization of estrus in beef cows and heifers with prostaglandin F2α and estradiol benzoate
THERIOGENOLOGY
SYNCHRONIZATION OF ESTRUS IN BEEF C O W S A N D H E I F E R S PROSTAGLANDIN F 2 a AND ESTRADIOL B ~ Z O A T E
WI%~H
M. E. Davis, T. ~. Turner, J. T. T. Forry, S. L. Boyles- and G. R. Wilson Animal Science Department The Ohio State University, Columbus, OH 43210 and Ohio Agricultural Research and Development Center, Wooster, OH 44691 Received for publication: Accepted:
March 5, 2986 July 6, 1987
ABSTRAC~ An experiment was conducted to study an estrous synchronization regimen that involved the use of prostaglandin Fo, (PGFo~) alone or in combination with estradiol benzoate (EB) and a p p o i n t ~ n t b r ~ d i n g . Fifty-three registered Angus yearling heifers and 167 registered Angus cows (3 to 9 yr of age) were given two injections of PGF~ ii d apart Forty-eight hours after the second in3ectlon of PGF~ , a random sample conslstlng of 117 cows and heifers was injected with EB inZ~esame seed oil. All females in the herd were artificially inseminated 80 h after the second injection of P G F g . Nearly equal percentages (25.1 vs 25.6%; P = 0.93) of treated ( ~ ) and control (no EB) females conceived at the appointment breeding. Use of EB tended to reduce (P = 0.06) natural service conception rate (83.4 vs 93.1% for EB and control groups, respectively). Estrous synchronization treatment did not affect interval from Day 1 of the breeding season to calving. Key words:
beef cattle, synchronization of estrus, prostaglandin F2~ , estradiol benzoate.
Acknowledgments Salaries and research support provided by state and federal funds appropriated to the Ohio Agr. Res. and Dev. Center, The Ohio State Univ. Journal Article No. 97-85. The authors wish to thank Mr. C. B. Boyles and Mr. J. D. Wells for their excellent technical assistance. S e ~ n was donated by Select Sires, Inc., Plain City, OH. Professional inseminators were provided by Central Ohio Breeders Assoc., Col~nbus, OH. Prostaglandin F2~(iutalyse) was donated by The Upjohn Co., iKalamazoo, MI. Present address: Anita. Sci. Dept., Kansas State Univ., Manhattan, KS 66506.
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275
THERIOGENOLOGY
INTRODUCTION Although the percentage of cattle bred by artificial insemination (AI) has increased substantially in the past 25 yr, factors exist that limit its use in beef cattle populations. Labor efficiency of an AI program is low because the producer must detect estrus and separate cows to be bred from the remainder of the c o w h e r d . In addition, if the producer relies on the services of a professional inseminator, the cost of summoning the inseminator to breed a few cows each day may be prohibitive. A further problem is the phenomenon of "silent heat" which may result in some cows not being detected in estrus during the AI breeding season. These problems have led to the development of various estrous synchronization products and programs. One such program involves breeding by "appointment" in which females are inseminated following a fixed time interval after adqlinistration of an estrous synchronization product. This procedure has the advantage of eliminating the need for estrous detection. Two inseminations at 72 and 90 h (i) or one insemination at 80 h (2) after prostaglandin F~ (PGF~) injection have been used successfully. Varying results h ~ e b e ~ obtained when estradiol benzoate (EB) is used in conjunction with PGF~ in an • L attempt to synchronize estrus (3-6). The objectlve of the pre~ent experiment was to evaluate the effectiveness of appointment breeding when PGF2~ alone or PGF2a and EB combined are used to synchronize estrus. MATERIALS AND METHODS Source of Data An estrous synchronization experiment was conducted at the Eastern Ohio Resource Development Center, Belle Valley, OH, in 1980. The experiment included data on 53 registered Angus yearling heifers and 167 registered Angus cows. Heifers were not observed for signs of puberty. However, average age of heifers at insemination was 442 d (range = 399 to 472 d). Therefore, it is assumed that nearly all, if not all, heifers were pubertal at the time of insemination. One-hundred-fifty-eight of 167 cows calved during the 1980 calving season and were lactating during the synchronization trial. Average length of the interval from calving to insemination was 69 d (range = 27 to 93 d). Measures of condition were not obtained prior to the beginning of the experiment. However, the cows appeared to be of sufficient condition to allow for successful breeding. Age of cows at breeding ranged from 3 to 9 yr (mean = 5.3 yr) with no 2-yr-olds included in the study. Fall weights taken on October 16, 1980, ranged from 318 to 404 kg (mean = 354.1 kg) for heifers and from 386 to 617 kg (mean = 468.6 kg) for cows. Cows and heifers were not palpated to determine the presence of a corpus luteum. Feeding Regimen Cows were maintained on a year-round pasture regimen and were fed 4.5 to 5.5 kg of supplemental hay/head/d during the winter months. Pasture and hay consisted of 85% Kentucky 31 Tall Fescue (IFN 1-09-187) and 15% native grasses. Heifers born primarily from April through May, 1979, received 1.4 kg/head/d of grain diet (Table I) from October 16, 1979, through March 4, 1980; 2.7 kg/ head/d from March 5 through May 30; and 1.4 kg/head/d from May 31 through June 30. No 2-yr-old cows were involved in the experiment.
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Three-year-olds were fed grain at the rate of 2.3 kg/head/d from March 4 through May 15, 1980. Water, salt and minerals were provided free-choice to all females. Table i.
Composition of experimental diet a
Ingredient
Corn, ground ear (IFN 4-28-238) Soybean meal (IFN 5-04-604) Dehydrated alfalfa (IFN 1-00-124) Salt, trace mineralized c Dicalcium phosphate (IFN 6-01-080)
%b
68.28 20.00 i0.00 1.00 0.50
a
The diet also contained 6.8 IU vitamin A/kg. Dry matter basis. c Contained 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% Co and 0.007% I. b
Estrus
Synchronization Treatments
Two 5 ml injections of PGF^ (equivalent to 25 mg of dinoprost • a . z ~ . . tromethamine ) were glven ii d apart. All cows and helfers in the herd received the first injection of P G F ^ on June 12 and the second injection on June 23, 1980. Estradiol benzoate (EB) in sesame seed oil, which was obtained from a local pharmacy, was injected into the round muscle of cows and heifers 48 h after the second injection of PGF2~ (June 25). A l-ml injection containing 500 ~g of EB was given to every other female that passed through the working chute. Eighty hours after the second injection of PGF2~ (June 26), all females in the herd were artificially inseminated by one-of six professional inseminators from the Central Ohio Breeders Association, Coltm~us. Frozen semen from five AI sires was used. Insem/_nators, AI sires and ages of dam were equally represented across the treated (EB) and control (no EB) groups. Cows and heifers were placed with one of five natural service sires beginning 15 d after the AI date. Natural service continued for approximately 6 wk. Conception rates were based upon actual calving data (number of cows calving/number cows bred). Statistical Analysis Dependent variables, conception rate at "appointment" breeding, AI conception rate, natural service conception rate, conception rate for the entire breeding season and number of days from Day 1 of the breeding season (June 26, 1980) to calving, were analyzed using the General Linear Models procedure (GIIM) found in the Statistical Analysis System (7). Treatment, a
Lutalyse, The Upjohn Co., Kalamazoo, MI.
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THERIOGENOLOGY
sire, age of dam at breeding and inseminator were included in the model for all traits except natural service conception. Inseminator was not involved in determining natural service conception. All two-way interactions involving treatment plus a covariate for weight of dam following the breeding season were included in the model. The covariate was found to be nonsignificant (P > 0.i0) in all cases and therefore was deleted from the model. Nonsignificant (P > 0.20) interactions also were deleted. Dams 5 yr old and older were considered to be mature dams and were grouped into one subclass. In the analysis of conception rate for the entire breeding season, the natural service sire was considered to be the sire if a female failed to conceive. RESULTS AND DISCUSSION Control females and females treated with estradiol benzoate (EB) had similar (P = 0.93) AI conception rates (Table 2). The effect of intra-uterine infusions of PGF_ and subsequent injection of EB on AI conceptlon rates in lactatlng ~ e f cows has been previously evaluated (4). It was found that first service conception rates among cows observed in estrus were 61% for cows receiving PGFo~ alone and 73% for those receiving PGF_ plus EB (P > 0 05) T~eatment with EB did not slgnlflcantly increase the percentage of cows In estrus durlng the AI season but did reduce variation in interval to onset of estrus. Other workers have also reported an increase in conception rates (36 vs 51%; P > 0.05) when cows were treated with PGFu rather than with PGFA2~ alone and . . . EB plus . inseminated followlng estrus ~ ) . The efflcacy of one or two i.m. injections of PGF^~, with or without subsequent injection of EB 48 h after PGFin3ectlon, for synchronization of estrus in beef cows and heifers w ~ h palpable corpora lutea has also been examined (6). These authors reported that EB resulted in a shorter and less variable interval to estrus but that it did not alter conception or pregnancy rates. A second injection of PGF 12 d after the first gave no advantage in synchronization of estrus (6)~~ Others have observed a reduction in conception rates (20.5 vs 31.8%) of nonlactating Bos Indicus cows that received EB 28 h after a second PGF^ injection (5). Insemination occurred 74 h after the second injection o ~ PGF . In a study involving dairy heifers (9), treatment with EB did not affe2~ct the percentage of animals exhibiting estrus within 96 h after treatment (86.7 vs 84.3%) or conceiving when bred 12 h after estrus (54.7 vs 57.5%). A greater proportion of heifers inseminated at 80 h conceived when treated with EB (52.9 vs 39.0%). Conception rates due to breeding at 72 h were low and were not improved by treatment with EB (29.7 vs 38.7%). In our study, control cows tended to have higher (P = 0.06) conception rates during the natural service period, although conception rates for the entire breeding season did not differ (P = 0.56) between treated and control cows (Table 2). •
.
.
z ~
"
"
.
.
Sire and age of dam at breeding did not significantly affect AI, natural service or overall conception rates (Table 2). A significant treatment by age of dam interaction existed for natural service conception, however (Table
3).
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Table 2.
Least-squares means and standard errors for factors affecting • a AI conception, natural service conception and overall conceptlon
AI conception N %
P = 0.93b
Treatment Control EBc Sire
i00 117
d
25.6 ± 4.9 25.1 ± 4.6
Overall conception N %
P = 0.06 74 86
93.1 ± 3.8 83.4 ± 3.4
P = 0.56 98 114
P = 0.70 20 41 60 61 763 25 28 38 39 63 85 105 167
27 32 53 53 52
Age at breeding 1 3 4 5+e
1 2 3 4 5 6
27.6 20.5 23.1 32.8 23.0
± ± ± ± ±
52 30 38 97
32.6 30.4 16.3 22.3
± ± ± +
8.6 7.9 6.5 6.5 6.6
7.5 8.9 8.0 4.8
8 5 13 15 15 28 17 21 18 17 21 33 1 P = 0.28 40 18 30 72
89.7 80.0 88.9 94.4
± 4.5 ± 6.7 +- 5.3 ± 3.4
43.3 34.3 29.2 20.8 25.1 0.0
± 9.5 ± 5.7 ± 9.2 +- 8.6 ± 8.7 ± 9.1
98.4 101.4 100.2 99.9 100.4 88.8 I00.3 95.6 99.8 84.6 95.2 90.9 96.8
± 8.5 ± 10.6 -+ 6.7 ± 6.1 + 6.2 ± 6.0 ± 8.1 ± 7.9 ± 6.7 + 7.1 + 6.1 ± 8.1 ± 23.9
P = 0.88 49 29 38 96
97.2 93.8 95.9 98.4
± ± ± ±
8.5 6.6 5.7 4.2
p = 0.81
P = 0.03 23 74 26 32 33 29
97.2 ± 3.2 95.4 ± 3.2 P = 0.69
P = 0.37
Inseminator
a b c d e
Natural service conception N %
23 73 26 30 32 28
100.4 93.4 98.7 96.5 95.0 93.9
_+ + ± -+ + +
6.4 5.0 6.3 6.8 6.5 7.8
Conception due to AI or natural service. Level of significance. Estradiolbenzoate. Sire was not included in the model used to analyze natural service conception due to confounding with age of dam at breeding. Includes cows 5 yr old and older.
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Table 3.
Least-squares means and standard errors for treatment by age of dam subclasses for natural service conception a
Treatment
Control
Age of dam
N
Conception percentage
1 3 4 5+
21 8 12 33
95.2 I00.0 83.3 93.9
± ± ± ±
6.2 i0.0 8.2 4.9
1 3 4 5+
19 i0 18 39
84.2 60.0 94.4 94.9
± _+ ± ±
6.5 9.0 6.7 4.5
a
b
Level of significance for treatment by age of dam interaction = 0.02. Estradiol benzoate.
Three-year-old cows had the highest natural service conception percentage among control cows but the lowest conception percentage due to natural service among cows receiving EB. Treatment with EB appeared to hinder natural service conception in the 3-yr-olds and to some extent in the yearling heifers. The apparent hindrance to natural service conception, but not to AI conception in these age groups may have been due to the low conception rates during the AI period (i.e., differences in AI conception rates between the age groups may not have been demonstrated due to the i o w A I conception rates). Inseminator had a significant effect on AI conception rates with least-squares means ranging from 0.0 ± 9.1 to 43.3 ± 9.5% (Table 2), thus emphasizing the importance of skilled inseminators in a successful AI program. Results of previous estrous synchronization trials have also demonstrated the necessity for using quality semen and competent inseminators in an AI program (6, 9). Average interval from D a y 1 of the breeding season to calving did not differ (P = 0.51) between control cows and cows receiving EB (Table 4). Among cows that calved, treated and control cows conceived equally early in the breeding season. The first calf in both the treated and control groups was born on March 29, 1981. The last calf in the control group was born on June i, while the last calf in the treated group was born on June 4. Therefore, the length of the calving season was 65 and 68 d in the control and treated groups, respectively. Use of EB did not appreciably change the length of the calving season or the distribution of calving dates. The effect of sire on interval from Day 1 of the breeding season to calving was highly significant with most of the differences existing between AI and natural service sires. Age of dam at breeding (P = 0.31) and inseminator (P = 0.45) did not affect interval to calving (Table 4).
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Table 4.
Least-squares means and standard errors for factors affecting interval from Day 1 of breeding season to calving
Item
N
Treatment
~
trol
Interval, d
P = 0.51 a 94 97
Sire c
300.3 ± 301.2 ±
1.4 1.4
P < 0.01
20 41 60 61 763 25 28 38 39 63 85 105 167
8 5 13 15 14 25 17 20 18 15 20 30 1
Age at breeding 1 3 ~+d
282.9 280.1 279.8 283.7 283.4 306.8 303.4 305.6 320.9 308.8 305.8 312.1 336.5
P = 0.31 48 26 35 92
297.6 302.2 303.3 299.8
Inseminator 1 2 3 4 5 6
± 3.6 ± 4.5 ± 2.8 ± 2.6 ± 2.7 ± 2.6 ± 3.5 ± 3.4 ± 2.9 ± 3.1 ± 2.6 ± 3.5 ± i0.i
± ± ± ±
3.6 2.8 2.4 1.8
= 0.45 23 67 25 29 31 26
295.4 298.5 300.0 302.6 303.0 305.0
+ + ± ± ± ±
2.7 2.2 2.7 2.9 2.8 3.3
a
Level of significance. Estradiol benzoate. c Sires 20, 41, 60, 61 and 763 were AI sires; the remainder were natural service sires. d Included cows 5 yr old and older. b
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Two injections of PGFg_ given Ii d apart did not yield acceptable conception rates when bree~ng was by appointment 80 h after the second injection. Estradiol benzoate administered 48 h after the second injection of PGF. did not improve conception percentage at the appointment breedi~ and tended to reduce natural service conception rates. Use of EB did not alter interval from beginning of the breeding season to calving.
REFERENCES
282
i.
Lauderdale, J.W., Seguin, B.E., Stellflug, J.N., Chenault, J.R., Thatcher, W.W., Vincent, C.K. and Loyancano, A.F. Fertility of cattle following PGF2~ injection. J. Anim. Sci. 38:964-967 (1974).
2.
Hafs, H.D., Manns, J.G. and Wood, P.D.P. Fertility of heifers and suckled cows inseminated at predetermined intervals after treatment with prostaglandin F2 . J. Agr. Sci. (Camb.) 91:479-482 (1978).
3
Nancarrow, C.D. and Radford, H.M. Use of oestradiol benzoate to improve synchronization of estrus in cattle. J. Reprod. Fertil. 43:404 abstr. (1975).
4.
Welch, J.A., Hackett, A.J., Cunningham, C.J., Heishman, J.O., Ford, S.P., Nadaraja, R., Hansel, W. and Inskeep, E.K. O~ntrol of estrus in lactating beef cows with prostaglandin F~ and estradiol benzoate. J. Anita. Sci. 41:1686-1692 (1975#.~
5.
Holness, D.H. and Hurrell, A.D. Fertility in cows after synchronisation of oestrus with prostaglandin F~ and oestradiol benzoate. S. Afr. J. Anim. Sci. 7:27-28 (1977).~
6.
Peters, J°B., Welch, J.A., Lauderdale, J.W. and Inskeep, E.K. Synchronization of estrus in beef cattle with PGF^ and estradiol benzoate. J. Anim. Sci. 45:230-235 (19~%.
7.
SAS User's Guide. Cary, NC, 1979.
8.
Inskeep, E.K., Welch, J.A., McClung, M.R., Linger, E.A. and Heishman, J.O. Control of estrus by PGF, and estradiol benzoate. J. Anim. Sci. 40:187 abstr. (~75).
9.
Dailey, R.A., James, R.E., Inskeep, E.K. and Washburn, S.P. Synchronization of estrus in dairy heifers with prostaglandin F2e with or without estradiol benzoate. J. Dairy Sci. 66:881-886 (1983).
Statistical Analysis System Institute, Inc.,
SEPTEMBER 1987 VOL. 28 NO. 3
SYNCHRONIZATION OF ESTRUS IN BEEF C O W S A N D H E I F E R S PROSTAGLANDIN F 2 a AND ESTRADIOL B ~ Z O A T E
WI%~H
M. E. Davis, T. ~. Turner, J. T. T. Forry, S. L. Boyles- and G. R. Wilson Animal Science Department The Ohio State University, Columbus, OH 43210 and Ohio Agricultural Research and Development Center, Wooster, OH 44691 Received for publication: Accepted:
March 5, 2986 July 6, 1987
ABSTRAC~ An experiment was conducted to study an estrous synchronization regimen that involved the use of prostaglandin Fo, (PGFo~) alone or in combination with estradiol benzoate (EB) and a p p o i n t ~ n t b r ~ d i n g . Fifty-three registered Angus yearling heifers and 167 registered Angus cows (3 to 9 yr of age) were given two injections of PGF~ ii d apart Forty-eight hours after the second in3ectlon of PGF~ , a random sample conslstlng of 117 cows and heifers was injected with EB inZ~esame seed oil. All females in the herd were artificially inseminated 80 h after the second injection of P G F g . Nearly equal percentages (25.1 vs 25.6%; P = 0.93) of treated ( ~ ) and control (no EB) females conceived at the appointment breeding. Use of EB tended to reduce (P = 0.06) natural service conception rate (83.4 vs 93.1% for EB and control groups, respectively). Estrous synchronization treatment did not affect interval from Day 1 of the breeding season to calving. Key words:
beef cattle, synchronization of estrus, prostaglandin F2~ , estradiol benzoate.
Acknowledgments Salaries and research support provided by state and federal funds appropriated to the Ohio Agr. Res. and Dev. Center, The Ohio State Univ. Journal Article No. 97-85. The authors wish to thank Mr. C. B. Boyles and Mr. J. D. Wells for their excellent technical assistance. S e ~ n was donated by Select Sires, Inc., Plain City, OH. Professional inseminators were provided by Central Ohio Breeders Assoc., Col~nbus, OH. Prostaglandin F2~(iutalyse) was donated by The Upjohn Co., iKalamazoo, MI. Present address: Anita. Sci. Dept., Kansas State Univ., Manhattan, KS 66506.
SEPTEMBER 1987 VOL. 28 NO. 3
275
THERIOGENOLOGY
INTRODUCTION Although the percentage of cattle bred by artificial insemination (AI) has increased substantially in the past 25 yr, factors exist that limit its use in beef cattle populations. Labor efficiency of an AI program is low because the producer must detect estrus and separate cows to be bred from the remainder of the c o w h e r d . In addition, if the producer relies on the services of a professional inseminator, the cost of summoning the inseminator to breed a few cows each day may be prohibitive. A further problem is the phenomenon of "silent heat" which may result in some cows not being detected in estrus during the AI breeding season. These problems have led to the development of various estrous synchronization products and programs. One such program involves breeding by "appointment" in which females are inseminated following a fixed time interval after adqlinistration of an estrous synchronization product. This procedure has the advantage of eliminating the need for estrous detection. Two inseminations at 72 and 90 h (i) or one insemination at 80 h (2) after prostaglandin F~ (PGF~) injection have been used successfully. Varying results h ~ e b e ~ obtained when estradiol benzoate (EB) is used in conjunction with PGF~ in an • L attempt to synchronize estrus (3-6). The objectlve of the pre~ent experiment was to evaluate the effectiveness of appointment breeding when PGF2~ alone or PGF2a and EB combined are used to synchronize estrus. MATERIALS AND METHODS Source of Data An estrous synchronization experiment was conducted at the Eastern Ohio Resource Development Center, Belle Valley, OH, in 1980. The experiment included data on 53 registered Angus yearling heifers and 167 registered Angus cows. Heifers were not observed for signs of puberty. However, average age of heifers at insemination was 442 d (range = 399 to 472 d). Therefore, it is assumed that nearly all, if not all, heifers were pubertal at the time of insemination. One-hundred-fifty-eight of 167 cows calved during the 1980 calving season and were lactating during the synchronization trial. Average length of the interval from calving to insemination was 69 d (range = 27 to 93 d). Measures of condition were not obtained prior to the beginning of the experiment. However, the cows appeared to be of sufficient condition to allow for successful breeding. Age of cows at breeding ranged from 3 to 9 yr (mean = 5.3 yr) with no 2-yr-olds included in the study. Fall weights taken on October 16, 1980, ranged from 318 to 404 kg (mean = 354.1 kg) for heifers and from 386 to 617 kg (mean = 468.6 kg) for cows. Cows and heifers were not palpated to determine the presence of a corpus luteum. Feeding Regimen Cows were maintained on a year-round pasture regimen and were fed 4.5 to 5.5 kg of supplemental hay/head/d during the winter months. Pasture and hay consisted of 85% Kentucky 31 Tall Fescue (IFN 1-09-187) and 15% native grasses. Heifers born primarily from April through May, 1979, received 1.4 kg/head/d of grain diet (Table I) from October 16, 1979, through March 4, 1980; 2.7 kg/ head/d from March 5 through May 30; and 1.4 kg/head/d from May 31 through June 30. No 2-yr-old cows were involved in the experiment.
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Three-year-olds were fed grain at the rate of 2.3 kg/head/d from March 4 through May 15, 1980. Water, salt and minerals were provided free-choice to all females. Table i.
Composition of experimental diet a
Ingredient
Corn, ground ear (IFN 4-28-238) Soybean meal (IFN 5-04-604) Dehydrated alfalfa (IFN 1-00-124) Salt, trace mineralized c Dicalcium phosphate (IFN 6-01-080)
%b
68.28 20.00 i0.00 1.00 0.50
a
The diet also contained 6.8 IU vitamin A/kg. Dry matter basis. c Contained 0.35% Zn, 0.28% Mn, 0.175% Fe, 0.035% Cu, 0.007% Co and 0.007% I. b
Estrus
Synchronization Treatments
Two 5 ml injections of PGF^ (equivalent to 25 mg of dinoprost • a . z ~ . . tromethamine ) were glven ii d apart. All cows and helfers in the herd received the first injection of P G F ^ on June 12 and the second injection on June 23, 1980. Estradiol benzoate (EB) in sesame seed oil, which was obtained from a local pharmacy, was injected into the round muscle of cows and heifers 48 h after the second injection of PGF2~ (June 25). A l-ml injection containing 500 ~g of EB was given to every other female that passed through the working chute. Eighty hours after the second injection of PGF2~ (June 26), all females in the herd were artificially inseminated by one-of six professional inseminators from the Central Ohio Breeders Association, Coltm~us. Frozen semen from five AI sires was used. Insem/_nators, AI sires and ages of dam were equally represented across the treated (EB) and control (no EB) groups. Cows and heifers were placed with one of five natural service sires beginning 15 d after the AI date. Natural service continued for approximately 6 wk. Conception rates were based upon actual calving data (number of cows calving/number cows bred). Statistical Analysis Dependent variables, conception rate at "appointment" breeding, AI conception rate, natural service conception rate, conception rate for the entire breeding season and number of days from Day 1 of the breeding season (June 26, 1980) to calving, were analyzed using the General Linear Models procedure (GIIM) found in the Statistical Analysis System (7). Treatment, a
Lutalyse, The Upjohn Co., Kalamazoo, MI.
SEPTEMBER 1987 VOL. 28 NO. 3
277
THERIOGENOLOGY
sire, age of dam at breeding and inseminator were included in the model for all traits except natural service conception. Inseminator was not involved in determining natural service conception. All two-way interactions involving treatment plus a covariate for weight of dam following the breeding season were included in the model. The covariate was found to be nonsignificant (P > 0.i0) in all cases and therefore was deleted from the model. Nonsignificant (P > 0.20) interactions also were deleted. Dams 5 yr old and older were considered to be mature dams and were grouped into one subclass. In the analysis of conception rate for the entire breeding season, the natural service sire was considered to be the sire if a female failed to conceive. RESULTS AND DISCUSSION Control females and females treated with estradiol benzoate (EB) had similar (P = 0.93) AI conception rates (Table 2). The effect of intra-uterine infusions of PGF_ and subsequent injection of EB on AI conceptlon rates in lactatlng ~ e f cows has been previously evaluated (4). It was found that first service conception rates among cows observed in estrus were 61% for cows receiving PGFo~ alone and 73% for those receiving PGF_ plus EB (P > 0 05) T~eatment with EB did not slgnlflcantly increase the percentage of cows In estrus durlng the AI season but did reduce variation in interval to onset of estrus. Other workers have also reported an increase in conception rates (36 vs 51%; P > 0.05) when cows were treated with PGFu rather than with PGFA2~ alone and . . . EB plus . inseminated followlng estrus ~ ) . The efflcacy of one or two i.m. injections of PGF^~, with or without subsequent injection of EB 48 h after PGFin3ectlon, for synchronization of estrus in beef cows and heifers w ~ h palpable corpora lutea has also been examined (6). These authors reported that EB resulted in a shorter and less variable interval to estrus but that it did not alter conception or pregnancy rates. A second injection of PGF 12 d after the first gave no advantage in synchronization of estrus (6)~~ Others have observed a reduction in conception rates (20.5 vs 31.8%) of nonlactating Bos Indicus cows that received EB 28 h after a second PGF^ injection (5). Insemination occurred 74 h after the second injection o ~ PGF . In a study involving dairy heifers (9), treatment with EB did not affe2~ct the percentage of animals exhibiting estrus within 96 h after treatment (86.7 vs 84.3%) or conceiving when bred 12 h after estrus (54.7 vs 57.5%). A greater proportion of heifers inseminated at 80 h conceived when treated with EB (52.9 vs 39.0%). Conception rates due to breeding at 72 h were low and were not improved by treatment with EB (29.7 vs 38.7%). In our study, control cows tended to have higher (P = 0.06) conception rates during the natural service period, although conception rates for the entire breeding season did not differ (P = 0.56) between treated and control cows (Table 2). •
.
.
z ~
"
"
.
.
Sire and age of dam at breeding did not significantly affect AI, natural service or overall conception rates (Table 2). A significant treatment by age of dam interaction existed for natural service conception, however (Table
3).
278
SEPTEMBER 1987 VOL. 28 NO. 3
THERIOGENOLOGY
Table 2.
Least-squares means and standard errors for factors affecting • a AI conception, natural service conception and overall conceptlon
AI conception N %
P = 0.93b
Treatment Control EBc Sire
i00 117
d
25.6 ± 4.9 25.1 ± 4.6
Overall conception N %
P = 0.06 74 86
93.1 ± 3.8 83.4 ± 3.4
P = 0.56 98 114
P = 0.70 20 41 60 61 763 25 28 38 39 63 85 105 167
27 32 53 53 52
Age at breeding 1 3 4 5+e
1 2 3 4 5 6
27.6 20.5 23.1 32.8 23.0
± ± ± ± ±
52 30 38 97
32.6 30.4 16.3 22.3
± ± ± +
8.6 7.9 6.5 6.5 6.6
7.5 8.9 8.0 4.8
8 5 13 15 15 28 17 21 18 17 21 33 1 P = 0.28 40 18 30 72
89.7 80.0 88.9 94.4
± 4.5 ± 6.7 +- 5.3 ± 3.4
43.3 34.3 29.2 20.8 25.1 0.0
± 9.5 ± 5.7 ± 9.2 +- 8.6 ± 8.7 ± 9.1
98.4 101.4 100.2 99.9 100.4 88.8 I00.3 95.6 99.8 84.6 95.2 90.9 96.8
± 8.5 ± 10.6 -+ 6.7 ± 6.1 + 6.2 ± 6.0 ± 8.1 ± 7.9 ± 6.7 + 7.1 + 6.1 ± 8.1 ± 23.9
P = 0.88 49 29 38 96
97.2 93.8 95.9 98.4
± ± ± ±
8.5 6.6 5.7 4.2
p = 0.81
P = 0.03 23 74 26 32 33 29
97.2 ± 3.2 95.4 ± 3.2 P = 0.69
P = 0.37
Inseminator
a b c d e
Natural service conception N %
23 73 26 30 32 28
100.4 93.4 98.7 96.5 95.0 93.9
_+ + ± -+ + +
6.4 5.0 6.3 6.8 6.5 7.8
Conception due to AI or natural service. Level of significance. Estradiolbenzoate. Sire was not included in the model used to analyze natural service conception due to confounding with age of dam at breeding. Includes cows 5 yr old and older.
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THERIOGENOLOGY
Table 3.
Least-squares means and standard errors for treatment by age of dam subclasses for natural service conception a
Treatment
Control
Age of dam
N
Conception percentage
1 3 4 5+
21 8 12 33
95.2 I00.0 83.3 93.9
± ± ± ±
6.2 i0.0 8.2 4.9
1 3 4 5+
19 i0 18 39
84.2 60.0 94.4 94.9
± _+ ± ±
6.5 9.0 6.7 4.5
a
b
Level of significance for treatment by age of dam interaction = 0.02. Estradiol benzoate.
Three-year-old cows had the highest natural service conception percentage among control cows but the lowest conception percentage due to natural service among cows receiving EB. Treatment with EB appeared to hinder natural service conception in the 3-yr-olds and to some extent in the yearling heifers. The apparent hindrance to natural service conception, but not to AI conception in these age groups may have been due to the low conception rates during the AI period (i.e., differences in AI conception rates between the age groups may not have been demonstrated due to the i o w A I conception rates). Inseminator had a significant effect on AI conception rates with least-squares means ranging from 0.0 ± 9.1 to 43.3 ± 9.5% (Table 2), thus emphasizing the importance of skilled inseminators in a successful AI program. Results of previous estrous synchronization trials have also demonstrated the necessity for using quality semen and competent inseminators in an AI program (6, 9). Average interval from D a y 1 of the breeding season to calving did not differ (P = 0.51) between control cows and cows receiving EB (Table 4). Among cows that calved, treated and control cows conceived equally early in the breeding season. The first calf in both the treated and control groups was born on March 29, 1981. The last calf in the control group was born on June i, while the last calf in the treated group was born on June 4. Therefore, the length of the calving season was 65 and 68 d in the control and treated groups, respectively. Use of EB did not appreciably change the length of the calving season or the distribution of calving dates. The effect of sire on interval from Day 1 of the breeding season to calving was highly significant with most of the differences existing between AI and natural service sires. Age of dam at breeding (P = 0.31) and inseminator (P = 0.45) did not affect interval to calving (Table 4).
280
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THERIOGENOLOGY
Table 4.
Least-squares means and standard errors for factors affecting interval from Day 1 of breeding season to calving
Item
N
Treatment
~
trol
Interval, d
P = 0.51 a 94 97
Sire c
300.3 ± 301.2 ±
1.4 1.4
P < 0.01
20 41 60 61 763 25 28 38 39 63 85 105 167
8 5 13 15 14 25 17 20 18 15 20 30 1
Age at breeding 1 3 ~+d
282.9 280.1 279.8 283.7 283.4 306.8 303.4 305.6 320.9 308.8 305.8 312.1 336.5
P = 0.31 48 26 35 92
297.6 302.2 303.3 299.8
Inseminator 1 2 3 4 5 6
± 3.6 ± 4.5 ± 2.8 ± 2.6 ± 2.7 ± 2.6 ± 3.5 ± 3.4 ± 2.9 ± 3.1 ± 2.6 ± 3.5 ± i0.i
± ± ± ±
3.6 2.8 2.4 1.8
= 0.45 23 67 25 29 31 26
295.4 298.5 300.0 302.6 303.0 305.0
+ + ± ± ± ±
2.7 2.2 2.7 2.9 2.8 3.3
a
Level of significance. Estradiol benzoate. c Sires 20, 41, 60, 61 and 763 were AI sires; the remainder were natural service sires. d Included cows 5 yr old and older. b
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THERIOGENOLOGY
Two injections of PGFg_ given Ii d apart did not yield acceptable conception rates when bree~ng was by appointment 80 h after the second injection. Estradiol benzoate administered 48 h after the second injection of PGF. did not improve conception percentage at the appointment breedi~ and tended to reduce natural service conception rates. Use of EB did not alter interval from beginning of the breeding season to calving.
REFERENCES
282
i.
Lauderdale, J.W., Seguin, B.E., Stellflug, J.N., Chenault, J.R., Thatcher, W.W., Vincent, C.K. and Loyancano, A.F. Fertility of cattle following PGF2~ injection. J. Anim. Sci. 38:964-967 (1974).
2.
Hafs, H.D., Manns, J.G. and Wood, P.D.P. Fertility of heifers and suckled cows inseminated at predetermined intervals after treatment with prostaglandin F2 . J. Agr. Sci. (Camb.) 91:479-482 (1978).
3
Nancarrow, C.D. and Radford, H.M. Use of oestradiol benzoate to improve synchronization of estrus in cattle. J. Reprod. Fertil. 43:404 abstr. (1975).
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Welch, J.A., Hackett, A.J., Cunningham, C.J., Heishman, J.O., Ford, S.P., Nadaraja, R., Hansel, W. and Inskeep, E.K. O~ntrol of estrus in lactating beef cows with prostaglandin F~ and estradiol benzoate. J. Anita. Sci. 41:1686-1692 (1975#.~
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Holness, D.H. and Hurrell, A.D. Fertility in cows after synchronisation of oestrus with prostaglandin F~ and oestradiol benzoate. S. Afr. J. Anim. Sci. 7:27-28 (1977).~
6.
Peters, J°B., Welch, J.A., Lauderdale, J.W. and Inskeep, E.K. Synchronization of estrus in beef cattle with PGF^ and estradiol benzoate. J. Anim. Sci. 45:230-235 (19~%.
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SAS User's Guide. Cary, NC, 1979.
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Inskeep, E.K., Welch, J.A., McClung, M.R., Linger, E.A. and Heishman, J.O. Control of estrus by PGF, and estradiol benzoate. J. Anim. Sci. 40:187 abstr. (~75).
9.
Dailey, R.A., James, R.E., Inskeep, E.K. and Washburn, S.P. Synchronization of estrus in dairy heifers with prostaglandin F2e with or without estradiol benzoate. J. Dairy Sci. 66:881-886 (1983).
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