90 million motile sperm cells) at one, two and three week intervals over twelve weeks
| Livestock Research for Rural Development 31 (6) 2019 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
The frequency of insemination in hens affects the costs associated with artificial insemination in poultry. A reduced frequency implies a larger insemination interval and therefore a reduction in costs. The objective of the study was therefore to assess the effect of insemination intervals on fertility, embryo mortality, hatch parameters and poult quality in turkeys. Sixteen locally - adapted toms and seventy-two turkey hens of thirteen and eleven months old respectively were used for the study. Hens were divided into three treatment groups of six replicates with four hens per replicate in a completely randomized design. Semen was pooled from the toms. Each of the hens was inseminated with 0.02ml of the pooled semen ((~90x106 motile sperm cells) at weekly, fortnight and three weeks intervals over 12 weeks. Fertility, embryo mortality, hatch parameters and poult quality were assessed.
Over a period of 12 weeks, hens inseminated with 0.02ml undiluted semen (containing approximately 90 million motile sperm cells) at intervals of one or two weeks had similar mean fertility, which was higher than when inseminated at three-week intervals. Embryo viability and poult quality were similar for insemination intervals of one, two and three weeks.
Keywords: artificial insemination, poult quality, sperm quality
The labour cost associated with artificial insemination (AI) forms a large proportion of the additional cost incurred in the adoption of the technology when compared to natural mating. The frequency of inseminating the hens is a determinant of the overall cost expended on labour and this frequency is based on the insemination intervals. With larger insemination intervals, frequency of insemination is reduced and so is the stress that may be placed on birds and ultimately, the cost of producing day old poults. However, when larger intervals are considered, it implies a longer stay of fertilising sperm cells in the oviduct and this may have a detrimental effect on fertility, embryo mortality or poult quality (Lodge et al 1971; Bramwell 2002).
An important factor that determines insemination interval is the sperm storage potential of the hen which varies with species. Turkeys are known to have a higher capacity to store sperm cells than chickens (Sasanami et al 2013). This can be attributed the higher number of sperm storage tubules they possess (Bakst et al 2010). For this reason, when insemination schedules are drawn, intervals for turkeys may be wider than that of chickens. Several reports of insemination intervals varying from 3 days to 14 days have been suggested for turkeys based on the undiluted semen dosage or number of sperm cells inseminated (Sexton 1976; Ogasawara 1981; Bramwell 2012).
Liu et al (2008) suggested that the efficient duration of fertile period is a good measure of the sperm storage potential of a hen. This period can be likened to the period of maximum fertility without repeated inseminations. Adebisi and Ewuola (Unpublished data) observed that locally adapted turkeys in Nigeria, maintained maximum fertility of over 90% for three weeks after insemination with varied doses of undiluted semen making it an efficient duration of fertile period. They suggested 0.02mL undiluted semen (containing approximately 80 million motile sperm cells) was as an economic dose that will also ensure maximum embryo viability at this period. This therefore creates a possibility of having inseminations at intervals of up to three weeks. Bakst (1988) reported a maximum fertility of over 90% up to 5 weeks post insemination, but embryo mortality or hatchability was not reported.
The objective of this study was therefore to investigate the effect of insemination intervals of one, two and three weeks on fertility, embryo mortality, hatch parameters and poult quality of the locally adapted turkey in Nigeria.
The research was carried out at the Teaching and Research Farm and the Animal Physiology Laboratory, Department of Animal Science, of the University of Ibadan, Ibadan, Nigeria.
White-feathered locally adapted turkeys (Meleagris gallopavo) were used for the study; sixteen turkey toms of 13 months old and seventy-two hens of 11 months old. Hens were divided into three treatment groups of six replicates with four hens per replicate in a completely randomized design. Hens were inseminated with semen harvested and pooled from the toms. Insemination intervals formed basis for treatment groups. Hens in group one were inseminated on weekly intervals, while those in groups two and three were inseminated at two and three week intervals, respectively. A basal insemination dose of two successive days were given to all hens across the groups at the commencement of inseminations for the study, after which a schedule was drawn for single day inseminations at specified intervals over 12 weeks. Thus, hens in group 1 were inseminated eleven more times at weekly intervals, those in group 2 were inseminated five more times at fortnight intervals while hens in group 3 were inseminated three more times at an insemination interval of 3 weeks.
Semen was collected from individual tom through the abdominal massage technique (Burrows and Quinn 1937). Semen showing poor quality as indicated by colour and viscosity, and that contaminated with faecal matter was discarded. After pooling the semen, it was gently mixed and a portion evaluated for sperm motility, sperm concentration and sperm liveability as described by Ewuola and Egbunike (2010). The number of motile sperm cells was estimated as the product of sperm motility and sperm concentration per mL of semen. The process of insemination was done as described by Burrows and Quinn (1939). It involved the oviduct eversion and then, deposition of semen into the oviduct. The semen dose for insemination was 0.02mL undiluted semen. Semen was deposited into the everted oviduct through the vaginal orifice at a depth of about 2.5cm using a graduated tuberculin syringe with a glass tube attached to its edge with a rubber tube. The period of semen collection and insemination of all the hens was within 40 to 50 minutes and it was done after 5pm to minimise the presence of an egg in the oviduct at the time of insemination.
The experimental units in this study were the replicates (of hens) per treatment. This is because it was the hens that received the insemination at varied intervals which is the treatment. The eggs of these hens were then used to assess fertility and other parameters measured. Eggs were collected daily from each treatment group, marked and stored on paper trays with broad end up at a temperature of 24 °C to 26°C and relative humidity of 70% – 85%. They were set for incubation weekly, after seven days of collection and storage. Eggs were placed randomly on setting trays prior to incubation. Candling of incubated eggs was done on day 25 of incubation. All candling clears were removed while those with evidence of developing embryo were transferred to the hatching unit to complete 28 days of incubation. At day 28, all hatched poults were counted and unhatched eggs, removed. The candling clears and unhatched eggs were broken–out to separate infertile eggs from those fertile but with dead embryos.
After break-out of the eggs, they were examined and the number of infertile eggs per treatment was noted. Infertile eggs were those eggs which upon break-out, were devoid of any form of embryonic mass. Eggs that had a form of embryonic mass upon break-out were categorised as fertile eggs with embryo mortality. Those fertile but with embryonic deaths were classified as early (deaths occurring at the first week of incubation), mid, at the second and third weeks while late was at the fourth week (last week) of incubation (Fairchild et al 2002). Eggs with embryo mortality at piping stage were also classified as late embryo deaths. All hatched poults and embryo deaths were counted together and regarded as the total number of fertile eggs. Percentage fertility was calculated by expressing the total fertile eggs as a percentage of all eggs set. Hatch of set eggs was total hatched poults expressed as a percentage of set eggs, while hatch of fertile eggs (or hatchability) was total hatched poults expressed as a percentage of fertile eggs. Embryo mortality at each stage was expressed as a percentage of fertile eggs.
On day 25 of incubation after candling, each hatching basket was divided into three compartments for the three treatments. Candled eggs were placed in the hatching baskets according to treatments before placement in the hatching unit. On day 28, hatched poults from each treatment group were classified as first grade and second grade based on physical parameters. A poult was classified as first grade if on observation was dry, free of deformities or lesions and if the navel was closed or opened to a maximum of 2mm (Reijrink et al 2010) and in addition to that, it must be agile. Poult agility or activity was measured by placing it on its back. The poult is expected to get up to its feet in less than 3 seconds to be rated as agile (Tona et al 2003; Schulte-Drüggelte 2016). Others were dead poults, those with various forms of physical deformities, wet down feathers, poor agility, opened navel of greater than 2mm diameter and poor gait. They were considered as 2 nd grade poults. The percentage of first grade poults was calculated by expressing the number of first grade poults as a percentage of total poults hatched.
Data were collected weekly on fertility, embryo mortality at each stage, hatch parameters and first grade poults. Analysis of variance was done on data using general linear model of SAS (2003) and means were separated using Duncan’s multiple range test. The significance was set at p<0.05.The fertility trend over time was presented using descriptive statistics.
The quality parameters of pooled semen inseminated over twelve 12 weeks are presented in Table 1. Spermatozoa concentration ranged from 4.2x10 9 to 6.7x109 sperm cells/mL, progressive motility was 85% to 95%, while liveability ranged from 88.7% to 99.3%. The mean values for the three semen quality parameters were 5.22x109cells/mL, 88.3% and 95.4%, respectively. This implied that the number of motile sperm cells in every 0.02mL of undiluted semen inseminated at each week was approximately 90x106 motile sperm cells.
The weekly fertility trend of turkey hens inseminated at 1, 2 and 3 weeks intervals over twelve weeks is presented in Figure 1 while Figure 2 represents the mean fertility for the insemination intervals over the twelve weeks. Hens inseminated weekly and fortnightly had similar trends over the 12-week period. Fertility was constantly above 80% for both treatment groups except for a slight drop at weeks 8 and 9. Eggs from hens inseminated at 3 weeks intervals had a fertility trend similar to the first 2 groups within the first 5 weeks, after which it dropped below 80%. The lowered fertility observed from 5 weeks in groups inseminated at 3 weeks interval in this study implied that a 3-week priming dose of semen over time could not sustain fertility comparable to 1 and 2 weeks intervals beyond 5 weeks. This lowered fertility over time may not be a case of oviductal sperm age, but of sperm depletion in the storage tubules over time.
|
Table 1. Characteristics of weekly pooled turkey semen inseminated over twelve weeks |
|||
|
Insemination
|
Spermatozoa |
Progressive |
Spermatozoa |
|
1 (Day 1 and 2) |
5.13 |
87.5 |
98.4 |
|
2 |
6.27 |
90.0 |
95.1 |
|
3 |
4.23 |
85.0 |
96.1 |
|
4 |
4.35 |
* |
90.9 |
|
5 |
5.11 |
85.0 |
96.8 |
|
6 |
5.25 |
* |
95.1 |
|
7 |
4.65 |
95.0 |
88.7 |
|
8 |
4.77 |
* |
92.5 |
|
9 |
6.68 |
85.0 |
97.6 |
|
10 |
4.51 |
90.0 |
98.6 |
|
11 |
6.16 |
85.0 |
95.1 |
|
12 |
5.54 |
95.0 |
99.3 |
|
Mean values |
5.22±0.80 |
88.61±4.17 |
95.35±3.24 |
|
Range |
4.23 – 6.68 |
85.0 – 95.0 |
88.7 – 99.3 |
|
Week 1 (Day 1 and 2) represents the mean values of
quality of pooled semen inseminated on each |
|||
|
| Figure 1.
Weekly fertility trend of turkey hens inseminated with 0.02mL undiluted
semen (containing approximately 90 million motile sperm cells) at one, two and three week intervals over twelve weeks |
 |
| Figure 2.
Mean egg fertility of turkey hens
inseminated with 0.02ml undiluted semen(containing
approximately 90 million motile sperm cells) at one, two and three-week intervals over twelve weeks. a,b – different letters indicate means significantly differ at p<0.05 |
It is noteworthy, that at the commencement of the study, insemination was done for two successive days to ensure filling of the SST, but subsequently, it was done on a single day at the specified interval for the group. Brillard and Bakst (1990) suggested that the maximum storage capacity of spermatozoa in the sperm storage tubules in turkeys is reached within two days of insemination. This may therefore suggest that over time, the single day priming dose may not have sufficed to make up for the sperm depleted over the preceding three weeks to ensure an optimal fertility level beyond 77.4% for hens inseminated at three weeks interval. Hence, another two succeeding days of priming dose may be required to refill sperm storage tubules to maximum capacity after every 4 to 5 weeks to sustain optimal fertility of above 80% for three weeks insemination interval.
The mean values of fertility, embryo mortality and hatch parameters of eggs from turkey hens inseminated with 0.02mL undiluted semen is presented in Table 2. Fertility and hatch of set eggs were significantly (p˂0.05) higher in hens inseminated weekly and at two weeks intervals (84.5% and 84.8% respectively) compared to three weeks intervals (77.4%). Hatch of fertile eggs was not significantly (p˃0.05) different among the groups and so were the values for early, mid and late embryo mortalities as well as the first grade poults.
The significantly lowered fertility observed in 3 weeks insemination intervals was probably due to the lowered fertility observed with the group over time as explained for Figure 1. The hatch of set eggs having a similar pattern as the fertility with a significantly lowered value for the groups inseminated at 3 weeks interval is expected since the hatch of fertile eggs did not differ significantly among the groups.
|
Table 2.
Egg fertility, embryo viability and hatch parameters of
turkey hens inseminated with 0.02ml undiluted |
||||
|
Parameters assessed (%) |
Insemination interval, weeks |
p |
||
|
One (n=466) |
Two (n=545) |
Three (n=514) |
||
|
Fertility |
84.5±2.5a |
84.8±1.3a |
77.4±2.2b |
0.016 |
|
Early Embryo Mortality |
6.2±1.2 |
4.7±1.0 |
5.3±1.1 |
0.983 |
|
Mid embryo mortality |
0.5±0.4 |
0.0±0.0 |
0.4±0.3 |
0.364 |
|
Late embryo mortality |
6.8±1.1 |
9.7±1.2 |
9.2±1.8 |
0.490 |
|
Hatch of fertile eggs |
82.8±2.5 |
85.6±1.4 |
83.7±2.3 |
0.641 |
|
Hatch of set eggs |
73.1±2.6a |
72.8±1.7a |
66.3±2.5b |
0.041 |
|
First grade poults |
84.8±1.5 |
83.2±1.8 |
84.2±2.3 |
0.834 |
|
a,b Means with different superscripts within a row significantly differ at p<0.05; n = number of eggs set |
||||
Bramwell (2002) reported that when stale sperms (i.e. cells that have resided in the oviduct for extended period) fertilise an egg, there may be increased occurrence of early embryo mortality or poor chick quality. This period was reported as 12 days in broiler breeders (Bramwell, 2002). Lodge et al (1971) also associated fertilisation by aged oviductal spermatozoa with embryo mortality in chickens. For turkeys, findings from this study show that embryo viability may not be compromised if sperm cell of up to 3 weeks oviductal age (as with insemination interval of 3 weeks) fertilises an egg. The poult quality was not affected too. First grade poults recorded for all the treatment groups was above 80% of the total poults hatched which implies that irrespective of the insemination intervals examined, the poult quality was not compromised or adversely affected even up to three weeks insemination intervals. This probably will reduce the fear of farmers in increasing the length of the insemination intervals of their turkeys which will safe cost, time, labour, reduce stress and increase their profit margin.
The Tertiary Education Trust Fund (TETFUND) is well appreciated for providing Institutional based Research grant in carrying out this research in the University of Ibadan.
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Received 20 February 2019; Accepted 4 May 2019; Published 4 June 2019