Vitamin E Supplementation in Gilts
The Effect of Vitamin E Supplementation on Onset, Duration and Expression of the Oestrous Cycle in Gilts
INTRODUCTION
The prevailing problems created by the dread of the avian influenza (avian flu) have affected protein intake of Nigerians negatively. Before now, it was common practice for small holders or households to keep a few poultry at their backyards but because of misinformation and of course a dread over the possible consequences of the avian flu, there is an almost collapse of such enterprise thereby making poultry out of the reach of the poor. Pig production therefore becomes the most likely and quickest solution to the problem of inadequate supply of animal protein especially in the middle-belt and South-eastern areas of Nigeria where pork is not discriminated against.
The overall pig productivity in the farm depends on the reproductive performance of gilts, the attainment of puberty in gilts, the duration and expression of the oestrus cycle. Vitamin E as a pro-biotic is known to enhance the reproductive performance of sows (Mahan,1991;1994) and, thus eliminating the use of antibiotics (Berger, 2007) and growth promoters whose use in the livestock industry are currently been discriminated due to the problems of residue in meat. Vitamin E is a term that encompasses a group of potent, lipid-soluble, chain- breaking antioxidants. It is considered the first line of defence against lipid peroxidation, protecting cell membranes at an early stage of free radical attack through its free radical-scavenging activity (Bjorneboe et al., 1990).
Material and Method
Sixteen Large White x Landrace crossed gilts maintained on a palm kernel cake and wheat offal - based diets, with about 17.9 percent crude protein as found on Table 1. They were used to determine the effect of different levels (0, 7.5, 15 and 30 IU) of vitamin E supplementation on the onset of puberty, the duration and the degree of expression of the oestrous cycle in gilts. The pigs were housed in a tropical type, open-sided pig house roofed with asbestos roofing sheets. The open sides of the building were covered with expanded metal and iron net to screen out flies and other insects. Each pen measured 2m x 7m with a dwarf wall of 120 cm high separating one room from the other and had concrete floors. Each pen had a wallow, feed, and water troughs, all made of concrete, and a dunging area. Pens were cleaned daily before pigs were fed. Pigs were fed in the morning and in the evening. Water was provided both on the wallow and in the water trough for drinking ad libitum. There was daily monitoring of the gilts between 8.00-9.00 am until the first heat. The onset of oestrous was the first day of an observable oestrus. Daily records were taken on physical observable changes associated with oestrus in gilts over two cycles to study the effect of supplementation of vitamin E on the expression of oestrus in cycling gilts. These included redness of the vulva, vocalization and restlessness, length, width and swelling of the vulva. For the vocalization, restlessness and redness, a system of ranking was employed. The ranking ranged one to four (1 - 4), thus, four measured the highest effect while one measured the least effect. To ensure that the cycle was properly assessed, sows were allowed first to be on standing heat, the heat was allowed to go out in order words all swelling, redness, and other signs of heat were allowed to go back to normal. The beginning of the cycle, counted as day one falls within the period of metestrus. This cycle was then followed to the next cycle.
Table 1. Composition of experimental diets
| T I | T II | T III | T IV |
| 46 | 46 | 46 | 46 |
| 17 | 17 | 17 | 17 |
| 26 | 26 | 26 | 26 |
| 4 | 4 | 4 | 4 |
| 5 | 5 | 5 | 5 |
| 0.25 | 0.25 | 0.25 | 0.25 |
| 1 | 1 | 1 | 1 |
| Treatments IU/kg/day | |||
| T II | T III | TIV | |
| 188.5±3.84185.5±4.63172.5183.3±5.15Duration of the cycle (days) | 21±0.0021±0.021±00 | 21±0.0 |
T I - 0 IU vitamin E
T II - 7.5 IU vitamin E
T III - 15 IU vitamin E
T IV - 30 IU vitamin E
IU -International Units
Results of the effect of supplementation on the expression of oestrus are represented on Figures 1-7. Vocalization and restlessness of the sows, swelling and redness of the vulva are significantly different during the varying stages of the oestrous cycle (P<0.05).Vulval length and width however were not statistically different (P>0.05). Vocalisation was highest around oestrous between days 12 and 15. Redness of the vulva ranked highest on day 15 and was least on day 6. The sows were conspicuously restless on days 16 and 17 while they were not restless at days 4, 7, and 8 except of course at meal times. The swelling of the vulva was also most pronounced at day 15 and 16 while the swelling was also most pronounced at day 15 and 16 while the swelling was least at day 4. However following supplementation only the swelling was significantly different (p< 0.05) among sows.
There was no significant difference (P>0.05) between the groups in time of onset of oestrus during this study. Anderson, (1985) has described the onset of oestrous to be characterized by gradual changes in behavioural patterns (e.g. restlessness, mounting of other animals, lordosis response), vulva responses (e.g. swelling, pink red colouring) and occasionally a mucous discharge while Thompson (2004) defined first oestrus to encompass ovulation, corpus leteum formation and function of normal duration. Gilts may breed as young as six months of age but there is a considerable range in age at puberty from as early as 116 days to more than 250 days (Holness, 1972) while Thompson (2004) defined first oestrus to encompass ovulation, corpus leteum formation and function of normal duration.
Vitamin E did not influence the duration of the oestrous cycle in the gilts. The duration of oestrous cycle as observed in this study is within the values reported by Hafez (1987) and McDonald (1989). The oestrous cycle is about 21 days, and range from 17-25 days. Reactive oxygen species (ROS) have been shown to have a physiological and pathological role in the female reproductive tract as they are involved in the modulation of an entire spectrum of physiological reproductive functions such as oocyte maturation, ovarian steroidogenesis, ovulation, implantation, formation of blastocyst, luteolysis and luteal maintenance in pregnancy corpus luteum function and luteolysis (Agarwal and Allamaneni (2004).The observations of the present study can therefore be explained by the fact that there were no challenge in either of the experimental groups requiring the intervention of the antioxidant ability of vitamin E.
In pigs, colour and size changes in the vulva are typical signs of approaching heat, and hence a useful tool for pig breeders. Of all the indices measured to evaluate the involvement of vitamin E on the expression of oestrus, only the degree of swelling of the vulva was significantly (P<0.05) affected. In the supplemented sows, the degree of swelling was more highly pronounced than in the non-supplement group. The external genitalia of the female pig are composed of some connective and fatty tissues (Frandson,1974). The vulva has blood vessels, which are engorged around the heat period due to the influence of the high oestradiol levels, resulting in the swelling and changes in colouration. Expression of oestrus is known to be influenced by the levels of ovarian steroids and pituitary gonadotropins present in the sow’s system. From the later part of this study, it was observed that vitamin E supplementation elaborated more FSH and LH in the supplemented group (Akomas et al., unpublished data) and this may have influenced the proliferation of oestradiol, which eventually induced the characteristic responses of oestrus, including swelling.
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Authors: S.C. AKOMAS1, A.G. EZEKWE2, S. N. IBE3 and J.A IBEAWUCHI3.
1 Department Of Veterinary Physiology and Biochemistry, Michael Okpara University of Agriculture, Umudike.
2 Department of Animal Science, University of Nigeria, Nsukka.
3 Department of Animal Science, Michael Okpara University of Agriculture, Umudike.
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