Turkey Hen Age, Fertility and Sperm Penetration of the Inner Perivitelline Layer Affects Embryonic Mortality
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2001-08-31
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When examining hatchability of eggs, the two main factors that contribute are fertility and embryonic mortality (EM). A common commercial observation across different turkey lines was that early embryonic mortality (EEM) appeared to be greater in young hens than in older hens. One point that complicates this issue is the ability to discriminate between EEM and infertile eggs. Therefore, there has always been a question about the accuracy of the reported number of infertile eggs. A study was designed to examine the hatch residue from turkey flocks of the same strain at two different ages. One flock was in its first two weeks of egg production and the second flock had been in production for at least 12 weeks. Six hatches with approximately 56,000 eggs total for all hatches combined were examined by macroscopic breakout. There were no differences in fertility or hatchability between the two different hen ages. EEM was greater in younger hens than in older hens. EM occurring during the last week of incubation was greater in older hens than in younger hens. A significant negative correlation was found between fertility and EEM in young hens suggesting that practices that could improve fertility may also minimize EEM. The difference between the two hen ages provided a model to further examine embryonic mortality in turkeys. Preliminary results from commercial resources indicated lower EM after hens were inseminated with higher numbers of sperm cells. It was hypothesized that sperm binding might differ between hen ages and that increasing the number of sperm in the insemination might compensate for lower binding. A study was designed to examine the sperm penetration (SP) of hens at two stages of egg production: the beginning of egg production and wk 12 of egg production. Using both in vivo and in vitro SP assays, the results indicated a larger number of SP holes in the perivitelline layer of the young hens when compared to older hens. The similarity between the in vivo and in vitro assays indicated a sperm binding effect independent of oviduct influences such as sperm storage and release rate. Another study was conducted to examine the female influence on SP and EEM in turkeys. Eggs from females of two different lines were examined at the two different ages examined in the previous studies. Females were mated to a single sire for the duration of the study to examine IPVL SP in the absence of sperm competition among different males. Eggs were used for either in vivo SP analysis or incubated for fertility, hatchability and EM data. Hens inseminated by a singe sire performed differently between the two age periods as demonstrated by a hen by period interaction. The response was inconsistent whereas some hens had increased SP holes, some decreased and some did not change between the two different age periods. Hens in the upper (HI) and lower (LO) third of the flock population based on SP holes were pooled in analyzing sperm hole effects on embryo viability. No differences in fertility or wk 1 mortality were detected between HI and LO hens. However, HI hens had higher hatchability and lower wk 4 EM compared to LO hens. In conclusion, the results of the current study demonstrated a significant female effect on SP. Furthermore, this effect appears to be due to unknown differences in IPVL properties as well as differences due to sperm storage and release rate from the sperm storage tubules. More research is needed to understand how the number of sperm cells relates to both early and late EM. These studies indicate that neither a high nor a low SP number, but that an intermediate number might result in optimal embryo survival.
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PhD
Discipline
Physiology
