An experiment was conducted at the piggery unit of the Department of Animal Science Farm, University of Nigeria, to evaluate the effect of dietary combination of alpha-tocopherol and ascorbic acid on the reproductive performance of gilts in the humid tropical zone of Nigeria.
Sixteen(16) twenty weeks old gilts were selected for this trial. The gilts were randomly assigned to four dietary treatments. Each treatment was replicated twice with two gilts per replicate making up four gilts per treatment.
One experimental ration containing 15% CP and 2,500Kcal/kgME was used but different levels of vitamins E and C for each treatment were added to the feed at the time of feeding. The gilts were placed on the gestation/lactation diet immediately after selection and were allowed to attain their second estrus before mating took place. The body weights of the gilts were recorded before mating following the manifestation of second estrus and date of mating recorded. Gilts were fed 2.0kg of the 15% CP diet each day when pregnancy was confirmed. Weekly body weights of the gilts were subsequently taken throughout the gestation period. At farrowing, their ration was increased to 2.6kg per pig per day until piglets were weaned at the age of 8 weeks. The birth weights of the piglets were recorded within 24 hours of parturition and subsequently, piglets’ weekly body weights were recorded until weaning. Similarly, the body weights of the lactating sows were taken weekly to monitor their body weight changes during lactation. All the data were processed and analyzed in accordance with 2x2 factorial arrangements in a completely randomized design (CRD). The result of the experiment showed that average litter size values of 7.00±0.58, 8.00±0.41, 8.00±0.00 and 7.00±1.00 for T1, T2, T3 andT4, respectively and the corresponding birth weight mean values of 0.97±0.08kg, 1.05±0.11kg, 1.19±0.00kg and 1.24±0.03kg were not significantly different (P>0.05) among the treatments. Significantly lower (P<0.05) pre-weaning body weight gain (g/day/piglet) was observed for piglets on T1 with mean value of 126.25±5.62 compared to piglets on T2, T3 and T4 with respective values of 150.77±5.00, 150.51±1.59 and 164.12±7.23. A range of 22.07±3.45% to 25.10±0.10% pre-weaning mortality was observed across treatments. Piglets on T1 had the least weaning weight of 7.25±0.28kg which differed significantly (P<0.05) from piglets on T2, T3 and T4 with weaning weight values of 8.42±0.24kg, 8.62±0.08kg and 8.71±0.60kg, respectively. The highest (P<0.05) gestation weight gain of 44.33±4.48kg was observed in gilts on T1.
This study finally suggested that dietary supplementation with vitamins E and C at 250 mg vitamin C alone, 120 IU vitamin E alone and 120 IU vitamin E/250 mg vitamin C combination during gestation of gilts and their lactation will effectively enhance litter size and lactation performance.
Key words: alpha-tocopherol, ascorbic acid, reproduction, gilts.
Site-specific information on the exact levels of vitamin E supplementation to gilts to optimize their reproductive ability and subsequently the body development of the piglets are lacking in most parts of the world particularly in the developing nations like ours. Most estimates on vitamin E supplementation are based on the minimum level required to overcome deficiency symptoms and not necessarily to promote productivity.
The fundamental role of vitamin E in optimizing fecundity rates and litter size in gilts/sows is demonstrated by the fact that maximal early growth and general wellbeing of the piglets depend among other factors on correct vitamin E supplementation to dam’s pre and post coitus.
Vitamin E is a critically important nutrient for all confinement-reared swine especially for the fact that it is not synthesized in the body of pigs. Thus, all swine require dietary sources to meet metabolic needs.
If gilt’s tissue tocopherol must be mobilized, the source of vitamin E for reproducing gilts/sows, nursing pigs and weaned piglets should be the diet (Nwangwu, 2012).
Pigs, however, can synthesize vitamin C in their body and do not require it in the diet. But according to Mc Dowell, (1989), it is possible that the endogenous synthesis of vitamin C in the pigs is inadequate to maximize vitamin C’s contribution to oxidative stability in some situations. The synthesis of vitamin C by pigs is insufficient under stressful conditions such as high environmental temperature, high humidity and diseases.
After fortifying some diets with vitamins E and C, an increased litter size at birth was generally demonstrated, litter birth weight increased, pre-weaning mortality reduced, pre-weaning growth rate increased and weaning weight increased accordingly (Nwangwu, 2012).
Vitamins C and E have been demonstrated by Gey (1998) to work together in preventing oxidative insult caused by biological free radicals such that vitamin E is the major chain-breaking antioxidant in lipid phase such as cellular membranes while the oxidizing free radical chain reactions are terminated in aqueous compartment of the animal body with vitamin C as the terminal reductant. Vitamin C has also been found to rejuvenate vitamin E in the animal body.
Objective of the Study: To evaluate the effect of dietary combination of alpha-tocopherol and ascorbic acid on the reproductive performance of gilts based on the following parameters:- conception rate, gestation length, litter size, piglet’s birth weight, pre-weaning piglet mortality, pre-weaning growth rate of piglets, weaning weight of piglets, litter size at weaning, gestation weight gain of gilts and lactation weight loss of sows.
Materials and method
The study was carried out at the piggery unit of the Department of Animal Science farm, University of Nigeria, Nsukka. The study lasted for 168 days. A total of sixteen(16) twenty-week old Large White x Landrace cross-bred gilts with an average weight of 65kg were used to investigate the effect of different levels of dietary supplementation of vitamins E and C on the reproductive performance of gilts. The gilts were housed in an open sided fly-proof pens measuring 3.2 x 2.7m with concrete feeding troughs and drinkers. They were randomly assigned to four treatments namely, T1, T2, T3 and T4. There were two replicates per treatment with two gilts per replicate making a total of four (4) gilts per treatment. A week to the arrival of the animals, the pens were cleaned, washed and subsequently disinfected to reduce the risk of disease transmission. The animals on arrival were dewormed and placed immediately on gestation/lactation diet. One experimental ration containing 15% CP and 2500kcal/kgME was used for the 16 gilts but different levels of vitamins E and C for each treatment were added to the feed at the time of feeding. The gilts were ear-notched for easy identification and having been placed on the gestation/lactation diet after arrival were allowed to attain their second estrus before mating took place. The body weights of the gilts were recorded before mating following the attainment of second estrus and the date of mating recorded. When pregnancy was confirmed by gilts not showing signs of estrus 21 days after mating, gilts were fed 2.0kg of 15%CP each day (Table 1 and 2) throughout gestation. Weekly body weights of the gilts were subsequently taken throughout the gestation period. Following farrowing, their ration was increased to 2.6kg per sow per day during lactation till weaning. The birth weights of the piglets were recorded within 24 hours of parturition. Thereafter, piglets’ body weights were recorded every week till weaning at 8 weeks of age. Similarly, the body weights of the lactating sows were taken weekly to monitor their body weight changes during lactation. Routine management procedures were observed such as injection of iron dextran at two days of parturition to prevent piglet anaemia and a follow-up with antibiotics treatment when deemed necessary.
The percentage and proximate composition of the experimental diet are presented in tables 1 and 2, respectively.
Table 1: Percentage Composition of the Gestation/Lactation Diet
Table 2: Proximate Composition of Gestation/Lactation Diet
Results and Discussion:
Table 3: Effect of dietary supplementation with levels of vitamins E and C on the reproductive performance of gilts.
The results of this study showed no interaction (P>0.05) effects of the two vitamins on any of the reproductive parameters. However, gilts on vitamins E and C supplemented diets were better in performance in pre-weaning mortality of piglets, pre-weaning growth rate of piglets, weaning weight of piglets and litter size at weaning than gilts on the control diet that had no vitamins supplementation.
From the results of this study, conception rate of 100% was achieved only by gilts on 250 mg vitamin C, followed by gilts on control diet (0 IU vitamin E, 0 mg vitamin C) with conception rate of 75%. Gilts on a combination of 120 IU vitamin E and 250 mg vitamin C and those on 120 IU vitamin E alone had 50% conception rate each. From this result, it could be inferred that supplementing breeding gilts with 250 mg vitamin C was the best level capable of facilitating all the processes involved in fertilization of the ova and subsequent implantation of the fetuses. However, the fact that gilts on the control diet without supplementation had better conception rate than the gilts on a combination of 120 IU vitamin E and 250 mg vitamin C and 120 IU vitamin E alone shows that conception rate in the pig could be independent of vitamins E and C supplementation if other nutrients capable of facilitating the processes of fertilization are made available in the diet. When subjected to less than optimal nutrition, gilts and sows exhibit reduction in fertility (Booth, 1990). Following mating, the optimal development of embryos is dependent upon the presence of nutritional and growth factors in uterine secretion (Solymosi and Hom, 1994). The uterine medium must provide both the right amount and the balance of nutrients. Robinson (1990) and Ashworth (1994) reported that extremes in the level of feeding and in the supply of specific dietary nutrients such as vitamins, minerals and proteins impact negatively on embryo survival, but moderate supply of these nutrients is what ensures proper uterine development. Effective breeding carried out at the correct timing during the oestrous period will also result in high conception rate which will help to improve the number of piglets born per litter (Davidson, 1948).
No significant effects of vitamins E and C (0>0.05) were recorded between the gilts in the various dietary treatments for gestation length. The overall mean gestation length observed in this study was 115.85±0.4 days. This conforms with values reported in the literature (Williamson and Payne,1978; Davidson and Coey 1966; Machebe, 2009). The non-significant difference (P>0.05) in gestation length observed in the study is expected because gestation length is determined genetically and does not vary widely within species (Day, 1972). Gestation length in animal species is fixed and only varies within a very narrow range within each species except under very severe stress (Heap et al., 1973). Temperature has been observed by Omtveldt et al. (1971) to be one of the factors that could cause slight variation in gestation length of animal species. Gestation period may be slightly shortened in hotter environment (Omtveldt et al., 1971). Other causes of variation in gestation length of animals are litter size and weight of the fetuses (Sorenson et al., 2002), age of the dam, breed and sex of the fetuses (Edwards et al., 1968).
The effects of dietary supplementation of vitamins E and C were not significant between the gilts in the four dietary treatments for average litter size. Litter size represents an important index in assessing a sow’s reproductive performance and it is an important trait in pig genetic improvement program (Rothschild and Bidavel, 1998). Herbert (1998) indicated that litter size was not only affected by diets but also depends on ovulation rate. Ovulation rate on the other hand is a measure of ovarian activity which is hormonally controlled. Litter size is basically determined by ovulation rate and embryo mortality (Blasco et al., 1995) and these processes take place mainly at the early stage of gestation. Increase in fetal survival largely accounts for increase in litter size of animals (Belstra, 2003). The litter size at parturition is a critical factor for the overall herd productivity (Dagorn et al., 1998) The overall mean litter size of 7.55±0.28 observed in this study is within the range of 1 to 12 piglets reported by Oseni (2005) in Nigeria and also conforms with average litter sizes of 7.45 and 8.1 reported by Adebambo (1986) and Rekwot et al. (2001), respectively. In temperate regions, the values obtained by Mahan (1994) were 11.85, 11.97 and 12.27 while those obtained by Yen and Pond (1981) were 9.8, 8.8 and 8.0.
The average birth weight of piglets from gilts in the four dietary treatments were not influenced by dietary supplementation of vitamins E and C. Mahan (1994), had observed that vitamin E supplementation had no effect on the birth weight of piglets. And Yen and Pond (1981) observed that vitamin C was ineffective in supporting number of piglets born per litter, live piglets and average piglet weight at birth for both sow and gilts. Birth weight is an important trait that influences piglet quality and survival. The overall piglet birth weight of 1.09kg reported in this study is within the range of values in the literature for pigs in the tropics (Adebambo, 1986; Ehiobu et al.,2000; Machebe, 2009) as compared to the values of 1.49, 1.48, 1.45 and 1.43 reported in the temperate regions by Yen and Pond (1981) and also the values of 1.68, 1.51 and 1.46 reported by Mahan (1994).
Piglets from gilts on the vitamins E and C supplemented diets performed significantly better than those on the control diet in terms of pre-weaning mortality. Gilts on 250 mg vitamin C, 120 IU vitamin E and a combination of 120 IU vitamin E and 250 mg vitamin C had similar pre-weaning piglet mortality mean values (P>0.05) which were however significantly lower (P<0.05) than the value for piglets on the control diet. Pre-weaning piglet mortality has been known to serve as a disease indicator as well as an indicator for adverse environmental conditions with a very negative implication on pre and post-weaning growth. Out of the major causes of pre-weaning piglet mortality which Mavromichalis (2010) highlighted as genetic disposition, faulty facilities, diseases, malnutrition, lack of specialized management and light-weight piglets that weigh below 1.0kg, outbreak of disease appeared to be the major cause of pre-weaning mortality of piglets in this study. It was observed that only the piglets of the gilts on vitamins E and C supplemented diets recovered speedily with reduced mortality. The piglets whose dams were on the control diet (i.e. no supplementation of vitamin E and C) could not recover as quickly thereby leading to high mortality in that treatment. The result of this study showed clearly the effects of antioxidant and immuno-modulatory properties of vitamins E and C on the piglets whose dams were on vitamins E and C dietary treatments as shown by their enhanced immune status. Gino (2008) stated that antioxidants provided through dietary supplementation can effectively contribute toward disease control in animals by boosting their natural immune defense mechanism.
For pre-weaning growth rate of piglets, weaning weight of piglets and litter size at weaning, these parameters followed the same trend observed in pre-weaning piglet mortality. The non significant difference (P>0.05) observed among the piglets from dams whose diets were supplemented with vitamins and the significant difference between these vitamins based groups and the control diet based groups on these parameters were not unexpected. This is in view of the fact that those piglets from gilts on different levels of dietary vitamin supplementation were able to have adequate transfer of these vitamins from the dams during gestation (pre-natal period) and subsequently during lactation (post-natal period). Thus, their antioxidant defense and immune status were boosted against any form of infection or stress that would lower their performances. This might explain why the vitamins E and C dietary supplemented piglets excelled in growth parameters more than the piglets on the control diet. Mahan (1991) noted that the tocopherol levels in sow diet appeared to have a large influence on the alpha-tocopherol status of piglets and feeding diets adequate in alpha-tocopherol to sows during gestation and lactation prevents problems for the piglets during pre- and post-weaning periods. Therefore, if sows are not provided with adequate vitamins E, C or both, smaller litter size, sow agalactia and piglet mortality during the first week of life might be exacerbated. Also, if sow’s tissue tocopherol and ascorbic acid must be mobilized, the main source of vitamins E and C for reproducing sows, nursing pig, pre-weaning and weaned piglets should be the diet (Gey, 1998).
The average gestation body weight gain of gilts in the four dietary treatments was not affected by vitamins E and C supplementation. The mean gestation body weight gain of 45.96±3.18kg obtained in this study was in line with that reported by Mahan (1994). However, it is higher than 25.30±3.08kg reported by Machebe (2009) and a little lower than 57.7±3.25kg reported by Ji et al.(2005). Variations in gestation body weight gain may be due to differences in plane of nutrition of the dams, ambient temperature, age and body condition at breeding (Verstegen et al., 1973; Noblet and Dividchi 1981 and Trottier and Johnson 2001). The high gestation weight gain observed in this study showed that gilts were nutritionally and physiologically able to support the dynamic changes occurring during gestation as reported by Ji et al. (2005). Higher gestation weight gain may also be a reflection of the number of fetuses being carried by the dams since weight gain of pregnant animals is the sum of compositional gain in various maternal tissues ( Ji et al. 2005).
Gilts on 120 IU dietary vitamin E supplementation recorded a higher lactation body weight loss (40.10kg) than those on a combination of 120 IU vitamin E and 250 mg vitamin C (24.50kg), 0 IU vitamin E and 250 mg vitamin C (28.53kg) and 0 vitamin E and C supplementation (25.83kg). These variations in bodyweight loss during lactation could be attributed to an over reliance of the gilts on 120 IU vitamin E supplementation in meeting the lactation needs of their offspring from their body reserves. It was observed during the study that the gilts on 120 IU vitamin E dietary supplementation gained much weight during gestation thereby looking fatter than the other gilts in other dietary treatments. It is possible that greater catabolism of body tissues as a result of increased suckling by the piglets would have contributed also to the high lactation weight loss of the gilts on 120 IU vitamin E supplementation. For instance, Reese et al. (1984) reported that reliance on body reserve by fat sows to meet lactation needs of their piglet brings about a greater loss of body fat resulting in a higher lactation weight loss due to mobilization of muscle tissues. Also Revell et al. (1998) reported that excessive maternal fat gain during gestation decreases voluntary feed intake of the gilts during lactation thus leading to mobilization of existing reserves during the period.
Based on the results of this study, the gilts and their progenies fed diets supplemented with varying levels of vitamins E and C and their combination at higher than the recommended levels were superior in terms of pre-weaning piglet mortality, pre-weaning piglet growth rate, weaning weight of piglets and litter size at weaning than when fed diets unsupplemented with the vitamins. This work, therefore, upholds that vitamins E and C act synergistically and that the combined effects of the two antioxidants are additive and immuno-modulatory. Based on the result of this study, therefore, vitamins E and C and their combination have been shown to improve health and reproductive aspects of pig production. The health outcome of morbidity was taken care of, while the reproductive outcomes of pre-weaning piglet mortality, pre-weaning piglet growth rate, weaning weight of piglets and litter size at weaning were all improved by supplementing pig’s diets with these vitamins and their combinations. It is therefore recommended that the gestation and lactation diets for pigs should be supplemented with at least 250 mg vitamin C, 120 IU vitamin E or a mixture of 120 IU and 250 mg of vitamins E and C to improve reproduction in gilts. In the overall, pig farmers will be able to improve both health and reproductive performance of their herd through the above mentioned recommendations.