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Optimal insemination interval, semen dose and dilution for optimum fertility in chickens under humid tropical conditions
Animal Reproduction Science, 20 (1989) 179-185
179
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Optimal Insemination Interval, Semen Dose and Dilution for Optimum, Fertility in Chickens under Humid Tropical Conditions L. BRATTE' and S.N. IBE 2
Department of Animal Science, University o[ Nigeria, Nsukka (Nigeria) (Accepted 8 March 1989)
ABSTRACT Bratte, L. and Ibe, S.N., 1989. Optimal insemination interval, semen dose and dilution for optimum fertility in chickens under humid tropical conditions. Anim. Reprod. Sci., 20: 179-185. The effect of insemination interval, semen dose and dilution on fertility was investigated. Good fertility was obtained with twice-weekly insemination using 0.01 to 0.05 ml undiluted semen, 0.03 to 0.05 ml semen diluted 1:1 or 0.04 ml semen diluted 1:3, and also with weekly insemination using 0.04 ml undiluted semen. Fertility showed a downward linear trend with dilution and a curvilinear trend with dosage, for all frequencies.
INTRODUCTION
Factors affecting fertility have been reviewed by Lake (1983). Reports are, however, varied on the levels of some of these factors required for optimum fertility. For example, Resende et al. (1976) and McCartney (1976) obtained optimum fertility with twice-weekly insemination, whereas Giesen and Sexton (1982) and Ibe and Obi (1987) recommended weekly inseminations. Satisfactory fertility was obtained with 0.01 ml semen (Besulin, 1982), but higher doses have been recommended ( (Reddy, 1978; Lee et al., 1982 ). Although levels of semen dilution ranging from 1: 1 to 1 : 5 have been advocated (Koll, 1980; Huyghebaert et al., 1986), Sexton (1977) had observed that dilutions of up to 1 : 10 could produce high fertility provided the inseminated quantity contained at least 100 × 106 spermatozoa. The objective of this study is to contribute further knowledge regarding the semen dose, insemination interval and semen dilution for optimum fertility in ~Permanent address: Agric. Science Unit, Bendel State University, Abraka Campus, Bendel State (Nigeria) 2To whom all correspondence should be addressed.
0378-4320/89/$03.50
© 1989 Elsevier Science Publishers B.V.
180 chickens under humid tropical conditions, when other factors are assumed optimal. MATERIALSAND METHODS
Location This study was carried out at the University Poultry Farm at Nsukka, situated between longitude 07 ° 24'E and latitude 06 ° 57'N at an elevation of 400 m above sea level. The period of the experiment (March to May) was the early rainy season with an average ambient temperature of 26 °C and relative humidity of 64-70%. Experimental animals and semen collection One hundred and twenty commercial Harco pullets about 60 weeks old were randomly housed in cages, two birds per cage, in a 3 × 5 × 4 factorial arrangement with two birds in a cage constituting a unit. The experiment was repeated five times (see 'Egg collection and incubation'). The factor levels were: insemination frequency (twice weekly, weekly and biweekly), insemination dose (0.01, 0.02, 0.03, 0.04 and 0.05 ml), and dilution ( 1 : 0, 1:1, 1: 3 and 1: 5, semen to diluent). Semen was extracted by the massage technique from nine indigenous Nigerian cocks selected from a population maintained on the farm. Both pullets and cocks were fed commercial layer ration ad libitum and had continuous access to fresh clean water. Semen dilution and insemination Semen (an average of 0.34 ml per cock) was pooled and a portion was diluted to the required ratios with freshly prepared egg yolk-sodium citrate-glycine (ECG) diluent (Saha and Singh, 1958). The diluent was prepared by mixing 10 ml of a buffer containing 0.18 g sodium citrate dihydrate (Na2CsH6OT"2H20) and 0.20 g glycine in distilled water with an equal volume of raw chicken egg yolk. Pullets were inseminated between 13.00 and 15.00 h local time when the uteri of most of them were free of hard-shelled eggs. Inseminations were completed within 20 min from the time of semen collection. Semen quality tests Motility of spermatozoa in both undiluted and diluted samples was subjectively rated on a scale of 0 (no motility) to 100 (vigorous motility) on examination under a light microscope, both before and after insemination. Spermatozoa counting in all samples was done with an Albert Sass haemocytometer.
181 TABLE 1 Mean candle fertility1 in different frequency-dosage-dilution subclasses Dilution
Frequency 2
Dosage (ml) 0.01
0.02
0.03
0.04
0.05
1:0
TW W BW
73" (64) 69 (76) 50 (76)
73" (63) 51 (70) 74" (58)
78" (55) 67 (73) 61 (71)
81" (51) 79" (49) 64 (67)
84" (66) 51 (54) 42 (60)
1:1
TW W BW
65 (65) 5 (75) 55 (91)
35 (73) 35 (64) 58 (72)
80" (76) 42 (60) 33 (79)
79" (54) 61 (28) 48 (72)
82 a (52) 61 (56) 17 (77)
1:3
TW W BW
18 (52) 7 (67) 41 (73)
45 (76) 24 (69) 40 (48)
45 (74) 50 (44) 44 (54)
81 = (50) 31 (55) 35 (71)
28 (69) 18 (55) 27 (55)
1:5
TW W BW
29 (55) 30 (69) 9 (63)
19 (63) 22 (51) 6 (52)
33 (60) 23 (84) 0 (16)
41 (63) 26 (52) 2 (42)
49 (68) 3 (53) 1 (67)
1Entries are mean candle fertility (%) with total number of eggs set in each subclass in parentheses. 2TW = twice weekly; W = weekly; BW = biweekly. aValues are not statistically different.
90
80
75:
70 ¸
.~ 601
.~ 60
4.5
~ 50 _J
_.J
~.
.
TW~I~L W EEKLY
30.
~
30
15' 0 0
40
~ B I W E E K L Y I I I I I I
1
2
3
I
DILUTION
I
4
I
t
5
I
I
6
2
~ I I I I
1
TWICE
WEEKI
I I I I I I I
)0 0.01 0.02 0.03 0.04 0.05 0.06 DOSAGE [ml}
Fig. 1. Graphical representation of frequency X dilution interaction, indicating significant downward linear trend with increasing dilution. Fig. 2. Graphical representation of frequency-dosage interaction, indicating significant curvilinear trend over dosage levels.
182
Egg collection and incubation Egg collection was begun about 48 h after the first insemination, and once a day thereafter. Eggs were properly marked, stored at room temperature (about 23 ° C; no cold room facility was available), and set at 2-week intervals for 10 weeks. The five setting periods constituted the five repetitions of the experiment. Data and analysis Fertile eggs were determined by candling on the 9th day of incubation. Eggs containing embryos, alive or dead, were regarded as fertile. Candle fertility was computed as the ratio of the number of fertile eggs to the total number of eggs set, expressed as a percentage. Untransformed percentage data were analysed, since preliminary analysis did not indicate any need for a transformation. Data were subjected to a threefactor analysis of variance, with all possible interactions, using Harvey's (1985) Least Squares and Maximum Likelihood (LSMLMW) programme. Linear and quadratic response trends over levels of dilution and dosage were investigated using orthogonal polynomial contrasts and appropriate models were fitted. Correlation between sperm concentration and fertility was also determined. RESULTS
Table I shows that fertility ranging from 73 to 84% (not statistically different ) was obtained with twice-weekly insemination using all doses of undiluted semen, with 0.03 to 0.05 ml semen diluted 1 : 1, and with 0.04 ml semen diluted 1 : 3. Also with undiluted semen, fertility in the given range was obtained with 0.04 ml semen weekly and with 0.02 ml semen bi-weekly. Fertility showed a significant downward linear trend with increasing diluTABLE 2 Regression models of fertility on dilution a n d on dosage at different frequencies of i n s e m i n a t i o n Factor
Frequency 2
Model b
R 2 (%)
Dilution
TW W BW
Y = 7 6 . 4 - 9.1X Y-- 55.5 - 7.9X Y = 5 7 . 6 - 9.9X
96 85 91
Dosage
TW W BW
Y = 8 6 . 8 - 6 6 . 4 X + 29.1X 2 - 3.4X 3 Y = 3.9 + 2 4 7 4 . 9 X - 36714X 2 Y = 32.8 + 8 6 8 . 4 X - 21357X 2
99.9 78 82
"See Table 1 for abbreviations. b y__ fertility; X - - d i l u t i o n or dosage.
183
tion for all frequencies (Fig. 1 ), whereas the trend with dosage was essentially curvilinear (Fig. 2). Table 2 gives the appropriate prediction models for the trends in the figures. Fig. 1 and 2 also illustrate frequency × dilution and frequency X dosage interactions, respectively, which were significant. Mean sperm concentrations per ml in the 1: 0, 1 : 1, 1 : 3 and 1:5 dilutions were 3.695 × 109, 1.865 × 109, 0.91 × 109 and 0.565 × 109, respectively. A significant (P < 0.05) correlation of 0.55 between sperm concentration and fertility was obtained. Sperm motility in both undiluted and diluted samples decreased from 95% on collection to about 70% 20 min later. Slightly better motility was observed in diluted samples. DISCUSSION The high fertility obtained with twice-weekly insemination using 0.01 to 0.05 ml diluted semen, 0.03 to 0.05 ml semen diluted 1:1 or 0.04 ml semen diluted 1:3, and also with weekly insemination using 0.04 ml undiluted semen agrees with the observation by McCartney (1952) that there were no significant differences in fertility with undiluted semen doses ranging from 0.01 ml to 0.05 ml in turkeys. Also, Pingel and Henker (1976) did not find any difference in fertility with twice-weekly and weekly inseminations with 0.05 ml or 0.1 ml in White Leghorns. However, Resende et al. {1976) and McCartney (1976) obtained significantly higher fertility when inseminations were done twice a week than weekly in fowls and turkeys. Reasons for the generally high fertility obtained with the combinations of doses, frequencies and dilutions mentioned above are probably the high motility of spermatozoa in both undiluted and diluted samples and also the continuous availability of a large number of spermatozoa in the sperm host glands (SHG) in the infundibulum (I-SHG) and in the utero-vaginal junction (UVSHG) for continuous fertilization of ova. The total number of spermatozoa delivered in the hen's reproductive tract weekly when insemination was done twice weekly was 72.8×106 (with 0.04 ml semen diluted 1:3), 111.9×106, 149.2 × 10e and 186.5× 10 e (with 0.03, 0.04 and 0.05 ml, respectively semen diluted 1: 1 ), and from 73.9 × 106 to 369.5 × 10e {with 0.01 to 0.05 ml undiluted semen). With 0.04 ml semen weekly, the number of spermatozoa was 147.8 × l0 s. Sperm concentrations of 50 × 106 to 100 × l0 s have been found adequate for good fertility in chickens and turkeys (Kim et al., 1974; Sexton, 1977). There is indication that fertility declined with increasing dilution - the socalled 'dilution effect'. A similar downward linear trend in fertility was observed in chickens by Rowell and Cooper (1960). However, the diluent seemed effective in providing added nutrients and buffer required to maintain spermatozoa in vitro. Also, the observed curvilinear trend in fertility with dosage
184
supports the findings of II'inskii et al. (1975) in chickens and Giesen and Sexton (1982) in turkeys. It thus seems that there is a dose threshold below and above which fertility is expected to decline. In this study, the threshold is 0.04 ml (see Fig. 2). The results suggest that twice-weekly insemination with 0.04 ml semen diluted 1: 3 or weekly insemination with 0.04 ml undiluted semen would be most adequate for optimum fertility under the prevailing tropical conditions. However, some caution has to be exercised because of the small group size in this experiment. The validity of these results would rely, to some extent, on similar findings in temperate areas. ACKNOWLEDGEMENT
The second author is grateful to the University of Nigeria, Nsukka, for its Senate Research Grant No. 00506/83 which made this study possible.
REFERENCES Besulin, V., 1982. The intervalbetween artificialinsemination of turkey hens. Ptitsevodstvo, 2: 25-27 (in Russian). Giesen, A.F. and Sexton, T.J., 1982. Effects of storage vessel,frequency of insemination and insemination dose on the fertilityof turkey semen held 6 hr at 15 C. Poult. Sci.,61:1471 (abstr.). Harvey, W.R., 1985. Least Squares and M a x i m u m Likelihood Computer Programmes. The Ohio State University, Columbus, O H (mimeograph). Huyghebaert, G., Van Wambeke, F. and Groote, G., 1986. The effectof diluent, dilutionrate and the number of spermatozoa on fertilityand hatchability obtained with turkey semen held for two hours. Poult. Abstr., 12 (1), No. 139. Ibe, S.N. and Obi, J.C., 1987. Effect of dosage of undiluted semen and frequency of insemination of fertilityof chicken eggs. Proc. 11th Annu. Conf. Nigerian Soc. Anita. Prod. Ahmadu Bello University, Zaria. Irinskii,E.V., En Bon, T., Tolstov, V.A. and Strelkova, L.I.,1975. Artificialinsemination of caged hens. Anita. Breed. Abstr., 54(5), No. 2048. Kim, J.K., Shin, W.J., Suh, G.C. and Sul, D.S., 1974. Effect of dilutationrate of semen and insemination intervalon fertilityin the domestic fowl. Res. Rep., Office Rural Development, Suwon, Korea, pp. 77-81. Koll, H., 1980. Collection and examination of semen from Muscovy ducks (Cairina moschata) with particular consideration of the possibility of mating fattening hybrids with the 'Cherry Valley' strain by artificial insemination. Anita. Breed. Abstr., 48: 397. Lake, P.E., 1983. Factors affecting the fertility level in poultry with special reference to artificial insemination. World's Poult. Sci., 39: 106-117. Lee, J.K., Song, H.B. and Hong, R.C., 1982. A study on the optimum dose of semen in the artificial insemination of hens. Anita. Breed. Abstr., 50: 420. McCartney, M.G., 1952. The physiology of reproduction in turkeys. 3. Effect of frequency of mating and semen dosage on fertility and hatchability. Poult. Sci., 31: 878-881. McCartney, M.G., 1976. The effect of semen dosage and insemination frequency on the fertility of broiler breeder hens. Poult. Sci., 55" 669-671.
185 Pingel, H. and Henker, V., 1976. Rationalization of A.I. in hens. Anim. Breed. Abstr., 44(3), No. 2415. Reddy, R.P., 1978. Effect of insemination time, dilution rate and oviposition-insemination interval on fertility and hatchability in chickens. Poult. Sci., 57:1182 (abstr.). Resende, O. De A., Monteiro, J.M.L., Gomes, W.V., Dias, P.G De O. and Meneguelli, C.A., 1976. Effect of A.I. on laying performance, health and fertility of White Leghorn hens. Anim. Breed. Abstr., 44: 601. Rowetl, J.G. and Cooper, D.M., 1960. Some effects of diluting cock semen. Poult. Sci., 39: 13811389. Saha, S.K. and Singh, R.B., 1958. A comparison of egg yolk-sodium citrate, egg yolk-sodium citrate-glycine as semen diluters. J. Dairy Sci., 41: 1633-1635. Sexton, T.J., 1977. Relationship between number of sperm inseminated and fertility of hens at various stages of production. Poult. Sci., 56:1443-1446.
179
Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands
Optimal Insemination Interval, Semen Dose and Dilution for Optimum, Fertility in Chickens under Humid Tropical Conditions L. BRATTE' and S.N. IBE 2
Department of Animal Science, University o[ Nigeria, Nsukka (Nigeria) (Accepted 8 March 1989)
ABSTRACT Bratte, L. and Ibe, S.N., 1989. Optimal insemination interval, semen dose and dilution for optimum fertility in chickens under humid tropical conditions. Anim. Reprod. Sci., 20: 179-185. The effect of insemination interval, semen dose and dilution on fertility was investigated. Good fertility was obtained with twice-weekly insemination using 0.01 to 0.05 ml undiluted semen, 0.03 to 0.05 ml semen diluted 1:1 or 0.04 ml semen diluted 1:3, and also with weekly insemination using 0.04 ml undiluted semen. Fertility showed a downward linear trend with dilution and a curvilinear trend with dosage, for all frequencies.
INTRODUCTION
Factors affecting fertility have been reviewed by Lake (1983). Reports are, however, varied on the levels of some of these factors required for optimum fertility. For example, Resende et al. (1976) and McCartney (1976) obtained optimum fertility with twice-weekly insemination, whereas Giesen and Sexton (1982) and Ibe and Obi (1987) recommended weekly inseminations. Satisfactory fertility was obtained with 0.01 ml semen (Besulin, 1982), but higher doses have been recommended ( (Reddy, 1978; Lee et al., 1982 ). Although levels of semen dilution ranging from 1: 1 to 1 : 5 have been advocated (Koll, 1980; Huyghebaert et al., 1986), Sexton (1977) had observed that dilutions of up to 1 : 10 could produce high fertility provided the inseminated quantity contained at least 100 × 106 spermatozoa. The objective of this study is to contribute further knowledge regarding the semen dose, insemination interval and semen dilution for optimum fertility in ~Permanent address: Agric. Science Unit, Bendel State University, Abraka Campus, Bendel State (Nigeria) 2To whom all correspondence should be addressed.
0378-4320/89/$03.50
© 1989 Elsevier Science Publishers B.V.
180 chickens under humid tropical conditions, when other factors are assumed optimal. MATERIALSAND METHODS
Location This study was carried out at the University Poultry Farm at Nsukka, situated between longitude 07 ° 24'E and latitude 06 ° 57'N at an elevation of 400 m above sea level. The period of the experiment (March to May) was the early rainy season with an average ambient temperature of 26 °C and relative humidity of 64-70%. Experimental animals and semen collection One hundred and twenty commercial Harco pullets about 60 weeks old were randomly housed in cages, two birds per cage, in a 3 × 5 × 4 factorial arrangement with two birds in a cage constituting a unit. The experiment was repeated five times (see 'Egg collection and incubation'). The factor levels were: insemination frequency (twice weekly, weekly and biweekly), insemination dose (0.01, 0.02, 0.03, 0.04 and 0.05 ml), and dilution ( 1 : 0, 1:1, 1: 3 and 1: 5, semen to diluent). Semen was extracted by the massage technique from nine indigenous Nigerian cocks selected from a population maintained on the farm. Both pullets and cocks were fed commercial layer ration ad libitum and had continuous access to fresh clean water. Semen dilution and insemination Semen (an average of 0.34 ml per cock) was pooled and a portion was diluted to the required ratios with freshly prepared egg yolk-sodium citrate-glycine (ECG) diluent (Saha and Singh, 1958). The diluent was prepared by mixing 10 ml of a buffer containing 0.18 g sodium citrate dihydrate (Na2CsH6OT"2H20) and 0.20 g glycine in distilled water with an equal volume of raw chicken egg yolk. Pullets were inseminated between 13.00 and 15.00 h local time when the uteri of most of them were free of hard-shelled eggs. Inseminations were completed within 20 min from the time of semen collection. Semen quality tests Motility of spermatozoa in both undiluted and diluted samples was subjectively rated on a scale of 0 (no motility) to 100 (vigorous motility) on examination under a light microscope, both before and after insemination. Spermatozoa counting in all samples was done with an Albert Sass haemocytometer.
181 TABLE 1 Mean candle fertility1 in different frequency-dosage-dilution subclasses Dilution
Frequency 2
Dosage (ml) 0.01
0.02
0.03
0.04
0.05
1:0
TW W BW
73" (64) 69 (76) 50 (76)
73" (63) 51 (70) 74" (58)
78" (55) 67 (73) 61 (71)
81" (51) 79" (49) 64 (67)
84" (66) 51 (54) 42 (60)
1:1
TW W BW
65 (65) 5 (75) 55 (91)
35 (73) 35 (64) 58 (72)
80" (76) 42 (60) 33 (79)
79" (54) 61 (28) 48 (72)
82 a (52) 61 (56) 17 (77)
1:3
TW W BW
18 (52) 7 (67) 41 (73)
45 (76) 24 (69) 40 (48)
45 (74) 50 (44) 44 (54)
81 = (50) 31 (55) 35 (71)
28 (69) 18 (55) 27 (55)
1:5
TW W BW
29 (55) 30 (69) 9 (63)
19 (63) 22 (51) 6 (52)
33 (60) 23 (84) 0 (16)
41 (63) 26 (52) 2 (42)
49 (68) 3 (53) 1 (67)
1Entries are mean candle fertility (%) with total number of eggs set in each subclass in parentheses. 2TW = twice weekly; W = weekly; BW = biweekly. aValues are not statistically different.
90
80
75:
70 ¸
.~ 601
.~ 60
4.5
~ 50 _J
_.J
~.
.
TW~I~L W EEKLY
30.
~
30
15' 0 0
40
~ B I W E E K L Y I I I I I I
1
2
3
I
DILUTION
I
4
I
t
5
I
I
6
2
~ I I I I
1
TWICE
WEEKI
I I I I I I I
)0 0.01 0.02 0.03 0.04 0.05 0.06 DOSAGE [ml}
Fig. 1. Graphical representation of frequency X dilution interaction, indicating significant downward linear trend with increasing dilution. Fig. 2. Graphical representation of frequency-dosage interaction, indicating significant curvilinear trend over dosage levels.
182
Egg collection and incubation Egg collection was begun about 48 h after the first insemination, and once a day thereafter. Eggs were properly marked, stored at room temperature (about 23 ° C; no cold room facility was available), and set at 2-week intervals for 10 weeks. The five setting periods constituted the five repetitions of the experiment. Data and analysis Fertile eggs were determined by candling on the 9th day of incubation. Eggs containing embryos, alive or dead, were regarded as fertile. Candle fertility was computed as the ratio of the number of fertile eggs to the total number of eggs set, expressed as a percentage. Untransformed percentage data were analysed, since preliminary analysis did not indicate any need for a transformation. Data were subjected to a threefactor analysis of variance, with all possible interactions, using Harvey's (1985) Least Squares and Maximum Likelihood (LSMLMW) programme. Linear and quadratic response trends over levels of dilution and dosage were investigated using orthogonal polynomial contrasts and appropriate models were fitted. Correlation between sperm concentration and fertility was also determined. RESULTS
Table I shows that fertility ranging from 73 to 84% (not statistically different ) was obtained with twice-weekly insemination using all doses of undiluted semen, with 0.03 to 0.05 ml semen diluted 1 : 1, and with 0.04 ml semen diluted 1 : 3. Also with undiluted semen, fertility in the given range was obtained with 0.04 ml semen weekly and with 0.02 ml semen bi-weekly. Fertility showed a significant downward linear trend with increasing diluTABLE 2 Regression models of fertility on dilution a n d on dosage at different frequencies of i n s e m i n a t i o n Factor
Frequency 2
Model b
R 2 (%)
Dilution
TW W BW
Y = 7 6 . 4 - 9.1X Y-- 55.5 - 7.9X Y = 5 7 . 6 - 9.9X
96 85 91
Dosage
TW W BW
Y = 8 6 . 8 - 6 6 . 4 X + 29.1X 2 - 3.4X 3 Y = 3.9 + 2 4 7 4 . 9 X - 36714X 2 Y = 32.8 + 8 6 8 . 4 X - 21357X 2
99.9 78 82
"See Table 1 for abbreviations. b y__ fertility; X - - d i l u t i o n or dosage.
183
tion for all frequencies (Fig. 1 ), whereas the trend with dosage was essentially curvilinear (Fig. 2). Table 2 gives the appropriate prediction models for the trends in the figures. Fig. 1 and 2 also illustrate frequency × dilution and frequency X dosage interactions, respectively, which were significant. Mean sperm concentrations per ml in the 1: 0, 1 : 1, 1 : 3 and 1:5 dilutions were 3.695 × 109, 1.865 × 109, 0.91 × 109 and 0.565 × 109, respectively. A significant (P < 0.05) correlation of 0.55 between sperm concentration and fertility was obtained. Sperm motility in both undiluted and diluted samples decreased from 95% on collection to about 70% 20 min later. Slightly better motility was observed in diluted samples. DISCUSSION The high fertility obtained with twice-weekly insemination using 0.01 to 0.05 ml diluted semen, 0.03 to 0.05 ml semen diluted 1:1 or 0.04 ml semen diluted 1:3, and also with weekly insemination using 0.04 ml undiluted semen agrees with the observation by McCartney (1952) that there were no significant differences in fertility with undiluted semen doses ranging from 0.01 ml to 0.05 ml in turkeys. Also, Pingel and Henker (1976) did not find any difference in fertility with twice-weekly and weekly inseminations with 0.05 ml or 0.1 ml in White Leghorns. However, Resende et al. {1976) and McCartney (1976) obtained significantly higher fertility when inseminations were done twice a week than weekly in fowls and turkeys. Reasons for the generally high fertility obtained with the combinations of doses, frequencies and dilutions mentioned above are probably the high motility of spermatozoa in both undiluted and diluted samples and also the continuous availability of a large number of spermatozoa in the sperm host glands (SHG) in the infundibulum (I-SHG) and in the utero-vaginal junction (UVSHG) for continuous fertilization of ova. The total number of spermatozoa delivered in the hen's reproductive tract weekly when insemination was done twice weekly was 72.8×106 (with 0.04 ml semen diluted 1:3), 111.9×106, 149.2 × 10e and 186.5× 10 e (with 0.03, 0.04 and 0.05 ml, respectively semen diluted 1: 1 ), and from 73.9 × 106 to 369.5 × 10e {with 0.01 to 0.05 ml undiluted semen). With 0.04 ml semen weekly, the number of spermatozoa was 147.8 × l0 s. Sperm concentrations of 50 × 106 to 100 × l0 s have been found adequate for good fertility in chickens and turkeys (Kim et al., 1974; Sexton, 1977). There is indication that fertility declined with increasing dilution - the socalled 'dilution effect'. A similar downward linear trend in fertility was observed in chickens by Rowell and Cooper (1960). However, the diluent seemed effective in providing added nutrients and buffer required to maintain spermatozoa in vitro. Also, the observed curvilinear trend in fertility with dosage
184
supports the findings of II'inskii et al. (1975) in chickens and Giesen and Sexton (1982) in turkeys. It thus seems that there is a dose threshold below and above which fertility is expected to decline. In this study, the threshold is 0.04 ml (see Fig. 2). The results suggest that twice-weekly insemination with 0.04 ml semen diluted 1: 3 or weekly insemination with 0.04 ml undiluted semen would be most adequate for optimum fertility under the prevailing tropical conditions. However, some caution has to be exercised because of the small group size in this experiment. The validity of these results would rely, to some extent, on similar findings in temperate areas. ACKNOWLEDGEMENT
The second author is grateful to the University of Nigeria, Nsukka, for its Senate Research Grant No. 00506/83 which made this study possible.
REFERENCES Besulin, V., 1982. The intervalbetween artificialinsemination of turkey hens. Ptitsevodstvo, 2: 25-27 (in Russian). Giesen, A.F. and Sexton, T.J., 1982. Effects of storage vessel,frequency of insemination and insemination dose on the fertilityof turkey semen held 6 hr at 15 C. Poult. Sci.,61:1471 (abstr.). Harvey, W.R., 1985. Least Squares and M a x i m u m Likelihood Computer Programmes. The Ohio State University, Columbus, O H (mimeograph). Huyghebaert, G., Van Wambeke, F. and Groote, G., 1986. The effectof diluent, dilutionrate and the number of spermatozoa on fertilityand hatchability obtained with turkey semen held for two hours. Poult. Abstr., 12 (1), No. 139. Ibe, S.N. and Obi, J.C., 1987. Effect of dosage of undiluted semen and frequency of insemination of fertilityof chicken eggs. Proc. 11th Annu. Conf. Nigerian Soc. Anita. Prod. Ahmadu Bello University, Zaria. Irinskii,E.V., En Bon, T., Tolstov, V.A. and Strelkova, L.I.,1975. Artificialinsemination of caged hens. Anita. Breed. Abstr., 54(5), No. 2048. Kim, J.K., Shin, W.J., Suh, G.C. and Sul, D.S., 1974. Effect of dilutationrate of semen and insemination intervalon fertilityin the domestic fowl. Res. Rep., Office Rural Development, Suwon, Korea, pp. 77-81. Koll, H., 1980. Collection and examination of semen from Muscovy ducks (Cairina moschata) with particular consideration of the possibility of mating fattening hybrids with the 'Cherry Valley' strain by artificial insemination. Anita. Breed. Abstr., 48: 397. Lake, P.E., 1983. Factors affecting the fertility level in poultry with special reference to artificial insemination. World's Poult. Sci., 39: 106-117. Lee, J.K., Song, H.B. and Hong, R.C., 1982. A study on the optimum dose of semen in the artificial insemination of hens. Anita. Breed. Abstr., 50: 420. McCartney, M.G., 1952. The physiology of reproduction in turkeys. 3. Effect of frequency of mating and semen dosage on fertility and hatchability. Poult. Sci., 31: 878-881. McCartney, M.G., 1976. The effect of semen dosage and insemination frequency on the fertility of broiler breeder hens. Poult. Sci., 55" 669-671.
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