Monitoring of the effects of various spiking techniques in broiler breeder flocks by counting of IPVL holes of the eggs

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1 Monitoring of the effects of various spiking techniques in broiler breeder flocks by counting of IPVL holes of the eggs B.VÉGI*, ZS. SZİKE, J. BARNA Research Institute for Animal Breeding and Nutrition, 21 Gödöllı, Isaszegi u.., Hungary *Corresponding author: The effect of various mating strategies on the mating efficiency of two and three flocks of broiler breeder was analysed during the whole reproduction cycle by weekly monitoring using IPVL hole counting technique in 4 and 5, respectively. 6 eggs/week of 3 birds/flock were examined by the method of Wishart (1999). For statistical analysis t test and multiple variance analysis were used. In 4, in flock A the sexual ratio was kept at 1 male to 1 females during the whole cycle. In flock B according to the technological recommendations the number of males was decreased from 1:1 to,75:1 to the end of the cycle and according to the local practice at the age of 36 and 42 week there were % and 17 % spiking, respectively. The highest sperm transport was found between 31 and 34 weeks of age then it decreased at the 53 rd week to the starting values in both flocks. Interestingly, the effect of spiking in flock B could not improve the flock performance significantly, though the spikings slightly increased the sperm transport. In flock A (no spiking, no changes in male number) the curve of medians of the number of holes was similar to the curve of flock B. Due to the hardly believable results, in 5 the investigations were repeated by monitoring of three flocks: in flock C the sexual ratio was kept at 1 male to 1 females during the whole cycle similarly to the flock A in the previous year. In flock D and E there were 5 and 25 % spiking, respectively at the age of 42 weeks parallel with decreasing of male numbers to,75:1 male/female final ratio to the end of the cycle. According to the results neither the 25 nor the 5 % replacements of young cockerels resulted in increase in the sperm transport. The results of the repeated investigations indicate that the recommended widening in male/female ratio and the expensive and labour intensive spiking technique used in the broiler breeder s practice did not increase the mating efficiency. On the basis of this results it is presumed that for the shortened persistency of fertility in broiler breeder rather the females than the males are responsible, above the genetic, rearing and keeping technological reasons. To clarify the role of female/male sexes in these processes further investigations are planned. Keywords: broiler breeder, sperm transport, IPVL holes, spiking, mating efficiency Introduction The fast growth of human population demands more and more feed, thus animal protein worldwide. In the poultry province the broiler production plays major role (87 per cent), which means 25 per cent of the total meet production (Brillard, 1). The basic condition of the successful production is the best quality with the lowest charge. Today the fertility of broiler breeder flocks decreases in the second part of the cycle which threatens the economical production particularly in older flocks kept according to the officially recommended keeping technology (Essısy and Török 4. personal communication). This is fact and problem not only in Hungary but other parts of the world as well (McDaniel, 1986; Creel et al. 199;

2 Walsh and Brake, 1997). In order to avoid the fast decrease of fertility in the second half of the production cycle different spiking techniques are used in the practice with more or less results. The fertility of eggs above the environmental and rearing conditions is determined by the mating efficiency, that is quality of the sperm and the libido of the cockerels on the male s side, and the other, also very important trait is the sperm storing ability on the female s side. During mating a huge amount of spermatozoa get into the vagina however only 1-2 % of them get into the sperm storage tubules (SSTs) after a strict selection progresses and the rest of the spermatozoa get lost for the fertilization. (Okamura and Nishiyama, 1978., Bakst et al., 1994.). The stored spermatozoa are released by tubules periodically, approximately 3 per cent a day. The tubules must be refilled by natural mating or AI otherwise the spermatozoa don t reach the sufficient level, and the fertile cycle closes (for two weeks in fowl). The sperm storing capacity of fowls depends not only on the genetic background of the species but also on the age of the laying hens, that is, their stage in the reproduction cycle (Bakst et al., 1994). It is proven by several examinations that the emptying of the spermatozoa from the SSTs gets faster after the peak of production (Brillard, 1993). It means that for keeping up the fertility of eggs they need more and more spermatozoa from the middle of the reproduction period. However, according to the official recommendations in the second half of the cycle the number of males has to decrease due to various considerations such as decreasing of competitions for females, sparing of females, and/or forcing the males to move more frequently (Ross Breeders Limited, Newbridge, 1998). The most practical and efficient method for analysis of the fertility of unincubated eggs is the counting of holes of inner perivitelline layer (IPVL) around the germinal disc produced by penetrating spermatozoa, namely the sperm penetration assay (Wishart, 1999). The aim of the present study was to analyze the effect of various mating strategies on the sperm transport that is fertility in broiler breeder flocks during the whole reproduction cycle by weekly monitoring in two consecutive years. Materials and methods Animals Studies were carried out in 4 and 5 respectively, with Ross 38 broiler breeder stock, 3 bird/ flock. The animals were kept according to the standards for broiler breeder parents stocks. The different flocks (experimental groups) originated from the same parent stock kept in different poultry houses on the same farm. In 4, in flock A the sexual ratio was kept during the whole cycle at 1 male to 1 females. For replacement of the spilled cockerels (mortality, selections for any reasons) males at the same age were used. In flock B according to the technological recommendations the number of males was decreased from 1:1 to,75:1 to the end of the cycle and according to the local traditional practice at the age of 36 and 42 week there were % and 17 % spiking of young cockerels, respectively. In 5, in flock C the sexual ratio was kept at 1 male to 1 females during the whole cycle similarly to the flock A in the previous year. In flock D and E there were 5 and 25 % spiking of young cockerels, respectively at the age of 42 weeks parallel with decreasing of male numbers to,75:1 male/female final ratio. Sperm Penetration assay Samples of approximately 6 eggs were collected from each of 5 flocks of broiler breeders aged between 27 and 52 weeks. They were stored at 16 ºC for up to 1 week before assessment. Eggs were brought to room temperature, cracked open, and the separated yolk placed in 1 % NaCl solution. Prior the membrane preparation egg fertility was assessed by visual examination of the germinal disc at the animal pole of the egg (Kosin, 1945). The perivitelline layer from over the germinal disc was cut out and washed in 1 % NaCl. The yolk free piece of membrane was spread on a microscope slide. The IPVL-holes were viewed with the x4 objective using darkground optics and the total of IPVL-holes from over the germinal disc was counted manually (Wishart et al., 4).

3 Statistical analyses Holes data were integrated for calculation the under curve area using Microcal Origin Version 3.5. For the statistical analysis t-tests were used by Statgraphics program. Results and discussion Results in 4 The highest sperm transport was found between 31 and 34 weeks of age then it decreased at the 53 rd week to the starting values in both flocks. In flock A (no spiking, no changes in male number) the curve of medians of the number of holes was similar to the curve of flock B. Interestingly, the effect of spiking in flock B could not improve the flock performance significantly (p.5), though both spiking slightly increased the sperm transport (Figure 1). Flock A Flock B 1 spiking % spiking 17% Figure 1. Age related changes in median IPVL holes from samples of 6 eggs taken from flocks A and B in 4 According to the data the sperm transport was about 1 % higher in flock B from the beginning of the cycle and this preference was kept during the whole period (Figure 2). Explanation of this basic difference between the examined flocks can be a kind of poultry house effect since the data of birds came from two different poultry house of the same farm (similar rearing technology, environment, etc.). The fluctuation in sperm transport is steadier in flock A than in flock B, presumably because the number of males had not changed during the whole cycle in flock A. Remarkable result in flock B that the effect of % spiking in week 36 and 17 % spiking in week 42 manifested in a slight increase of sperm transport only 4-6 weeks later. Presumably, the creation of new harems takes such a long time. According to the under curve data in flock B the sperm transport after the 2 nd spiking was 6 % higher than in flock A of the same period. The slight increase in sperm transport was not significant in any cases of spiking. Consequently, the two consecutive 17 and % spiking rate did not seem to be enough for raising of sperm transport that is fertility in the second part of the production cycle. Due to the questionable results, in 5 the investigations were repeated with some modifications by monitoring of three flocks with various mating strategies.

4 Flock A Flock B Figure 2. Comparison of age related changes in medians of holes in the flock A and B Results in 5 Figure 3 shows that the sperm quantities were relatively low in all the three experimental flocks and a similarly slight increase in sperm transport was found in each group around the age of 45 week. Since the increase was equivalent in all flocks it could not been found that either the 25 or even the 5 % (!) replacements of young cockerels resulted in any extraordinary significant - increase in the sperm transport. Flock C Flock D spiking 5% Flock E spiking 25% age (week) Figure 3. Age related changes in median IPVL holes from samples of 6 eggs taken from flocks C, D and E in 5

5 In Figure 4 above the median values the fertility data are also shown. In 5, the highest median values were found at the age of 37 week at all flocks. Two weeks later all median values decreased, although the fertility values at the same week did not follow the tendency in every flock. In flock C the fertility rate increased despite the decreasing sperm transport. The reason for this may be the slowly but continuously increasing sperm quantity of the previous weeks which could slightly raise the fertility for more weeks. However, in the flock D and E the low or rather jumping sperm quantities of the pervious weeks were not enough for keeping the fertility at the same level (see Figure 3). The data support the idea that the number of IPVL holes of 1-1 weeks is not authentic for fertility prediction, therefore inference regarding to fertility persistency can be drown only by continuous monitoring of the eggs ,6 % * 92,9 % * 9,4 % * 88,6 % * 9,1 % * 88,6 % * C D E Flocks 37 weeks of age 39 weeks of age * percentage of fertility Figure 4. Medians of IPVL holes in the various flocks at the age of 37 and 39 week, in 5 In Figure 5 the data of those flocks can be seen which were treated in the same way that is no decrease in male number and no any replacements of cockerels in the two consecutive years. It can be shown unanimously the differences in sperm transport in the two years. The reason for this can be only the difference between the rearing circumstances since the birds of both groups came from the same breeds, were kept in the same house at the same farm, caring in the reproductive period by the same workers by the same ways in the two consecutive years. In 5, whereas the bodyweights of birds was below the requirements by the lighting program a delayed maturation was decided. Although at the beginning of the cycle the flock fertility was satisfactory despite the lower sperm transport, it decreased to a lower level to the second half of the cycle than in 4. Presumably the mentioned drawback from the beginning of the cycle could not be compensated by even the 5 % spiking in flock D (see Figure 3).

6 Flock A Flock C Figure 5. Comparison of the median changes of IPVL holes in flock A (4) and C (5) Conclusions From the results of the continuous examination of the 5 flocks from the same farm in two consecutive years can be drown several conclusions. The results of the repeated investigations indicate that the recommended widening in male/female ratio and the expensive and labour intensive spiking technique used in the broiler breeder s practice could not increase the mating efficiency, as it was found earlier also by Bramwell et al., (1996). The finding reported here support the ideas of previous authors that for the shortened persistency of fertility in broiler breeder rather the females than the males are responsible (Pierson et al., 1988; Fasenko et al., 1992; Brillard, 1993; Bramwell et al., 1996; Gumulka, and Kapkowska, 5), above the genetic, rearing and keeping technological reasons. To clarify the role of female/male sexes in these processes further precise investigations are necessary. It was proved that the circumstances of rearing, e.g. delayed maturation can cause a serious deterioration in the further reproduction performance of broiler breeders. For the practice it is a useful finding that for the prediction of fertility persistency the IPVL holes data of the first 6 week of the cycle can provide sufficient information. However, as it was mentioned earlier for the reliable prediction continuous egg examinations are necessary for this early period. The 2 year study justified that the practice of spiking is absolutely useless though it has been used recently on several broiler breeder farms. For practice it is suggested to consider of the elaboration of different mating strategies, such as keeping a narrower sexual ratio until the end of the production cycle. References BAKST, M.R., WISHART, G.J., BRILLARD, J.P. (1994): Oviducal sperm selection, transport, and storage in poultry. Poultry Science Reviews, 5: BRAMWELL, R. K., McDANIEL, C. D., WILSON, J. L., HOWARTH, B. (1996) Age effect of male and female broiler breeders on sperm penetration of the perivitelline layer overlying the germinal disc. Poultry Science 75: BRILLARD, J. P. (1) Future strategies for broiler breeders: an international perspective. World Poultry Science 57: BRILLARD, J.P. (1993): Sperm storage and transport following natural mating and artifical insemination. Poultry Science, 72:

7 CREEL, L. H., MAURICE, D., BRIDGES, W. C., GRIMES, L. W. (199) A model to describe and predict post-peak changes in broiler hatchability. Journal Application Poultry Science 7: FASENKO, G. M., HARDIN, R. T., ROBINSON, F. E. (1992) Relationship of hen age and sequence position with fertility, hatchability, viability, and preincubation embryonic development in broiler breeders. Poultry Science 71: GUMULKA, M., KAPKOWSKA, E. (5) Age effect of broiler breeders on fertility and sperm penetration of the perivitelline layer of the ovum. Animal Reproduction Science 9: KOSIN, I. I. (1945): The accuracy of the macroscopic method in identifying unincubated germ discs. Poultry Science, 24: McDANIEL, G. R. (1986) Sex separate feeding of broiler parent stock. Zootech. Int. 11: OKAMURA, F., NISHIYAMA, H. (1978): The passage of spermatozoa through the vitelline membrane in the domestic fowl, Gallus gallus. Cell Tissue Res. 188(3): é PIERSON, E. E., KRISTA, L. M., McDANIEL, G. R. (1988) Effect of age and physiological status on sperm storage 24 hours after artificial insemination in broiler breeder hens. British Poultry Science 29: TECHNOLOGICAL DESCRIPTION OF ROSS BREEDERS LIMITED (1998) WALSH, T.J., BRAKE, J. (1997): The effect of nutrient intake during rearing of broiler breeder females on subsequent fertility. Poultry Science, 76: WISHART, G. J., YOUNG, M., STAINES, H. J. (4) Weekly monitoring of broiler breeder flock mating efficiency by sperm transfer into eggs. British Poultry Science 45 (3): -3. WISHART, G.J. (1999): Avian sperm: egg interaction: mechanisms and practical application for analysis of fertility. Proc. of the International Congress on Bird Reproduction, Tours