ABSTRACT
This study was conducted to investigate the effect of dietary selenium (se) supplementation on the reproductive performance of sows, preweaning growth performance of their piglets, haematological and antioxidant status of pigs. Twelve (12) crossbred sows (Landrace × Large White) aged 1-2 years with an average body weight (BW) of 56.1 ± 5kg were randomly allotted to four treatment groups of three sows per treatment in a completely randomised design (CRD). The treatment groups comprised T0 (no Se supplementation), and T1, T2, T3 administered with 0.30 mg/Kg selenium‐methionine during second trimester of gestation, third trimester of gestation and lactation respectively. Selenium supplementation significantly (P<0.05) improved reproductive efficiency as measured by larger litter size (T0; 5.67 ± 0.33, T1; 6.00 ± 92.47, T2; 7.66 ± 1.20, T3; 8.33 ± 8.33) reduced mortality,( T0; 2.33 ± 0.33%, T1; 1.00 ±
0.49%, T2; 0.66 ± 0.33%, T3; 0.47 ± 3.05%), and increased litter weight at weaning (T0; 5.07 ±
5.92 kg, T1; 5.79 ± 0.02kg, T2; 5.76 ± 2.64kg, T3; 5.93 ± 1.85kg), in the Selenium treated groups
when compared to the control group. Haematological parameters were not significant (P>0.05) among treatments during the second trimester of gestation. However, Se supplementation significantly (P<0.05) increased Pack Cell Volume (PCV) (T0; 32.50 ±
0.25%, T1; 38.50 ± 0.08%, T2; 37.00 ± 1.00%, T3; 34.50 ± 0.50%) and Red Blood Cell (RBC) (T0;
131.50 ± 28.5, T1; 185.0 ± 35.0, T2; 177.5 ± 32.5, T3; 210.0 ± 20.0) during the third trimester and Red Blood Cell (RBC) (T0; 108.0 ± 2.00, T1; 165.0± 15.0, T2; 175.0 ± 5.00, T3; 165.0± 5.00) and White Blood Cell (WBC) (T0; 22.07±0.44, T1; 11.20±0.80, T2; 9.00± 1.00, T3; 10.00±3.60) during lactation. All Se supplemented groups showed significantly increased plasma Selenium concentration in all stages compared with the control. Dietary selenium supplementation significantly increased plasma Glutathione –S- Reductase, Glutathione peroxidase (GSH-Px) activity during lactation (T3) and significantly (P<0.05) decreased plasma Malondialdehyde (MDA) (T0; 3.76 ± 1.74, T1; 0.12 ± 0.03, T2; 0.11±0.35, T3; 4.36 ± 0.62), (T0; 7.26 ± 0.08, T1; 3.60 ±
0.22, T2; 3.70 ± 0.27, T3; 2.27 ± 0.11),content in the third tremester of gestation and Lactation
respectively. Superoxide Dismutase (SOD) and catalase activity in all treatment groups was significantly (P<0.05) different compared to the control. From these results, it was concluded that dietary selenium supplementation increased reproductive efficiency and enhanced haematological and serum anti-oxidant enzyme activities of pigs especially during gestation and lactation.
CHAPTER ONE
1.0 INTRODUCTION
Food security refers to the availability of food and one’s access to it and it exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food to meet their dietary needs and food preferences for an active and healthy life (WHO, 1996). As human population continues to grow, with the greatest growth expected in countries that are already suffering from chronic hunger and malnutrition, there will be need to ensure food safety for all and especially the more susceptible sector of human population (Adeola and Olukori, 2009). It is a well known fact that the growth rate of human population far exceeds that of animal protein supply and this great disparity creates a problem for food security. Consequently, the demand for animal protein exceeds the supply (Ikani and Dewfang, 2004).
The present average daily protein intake among Nigerians is 45.5g per head per day as against the FAO’s recommended minimum intake of 62g per head per day (FAO, 1996). Similarly, the International Conference on Nutrition (ICN) reported that low income rural and semi urban adult dweller in Nigeria consumed less than 60% of their caloric need (which is
2400Kcal/head/day) and less than 40% of their protein needs (ICN, 1992). It seems apparent that animal protein intake of average Nigerian has not yet improved over the years irrespective of government policies towards achieving food security in Nigeria. This therefore suggests more radical approach to the problem.
Pig production which is recently on the increase is part of the efforts and one of the fastest means of bridging the prevailing animal protein deficiency gap which has developed over the years due to increasing population (Serres, 1992). Eusebio, (1980) described the pig as one of the most prolific and fast growing livestock that can convert food waste to valuable product. Their annual growth rate (3.8%) is higher than that of the human population (2.3-
2.8%) (Shaib et al., 1997). Pigs excel other animals, such as cattle, sheep and goats in converting feed to flesh (Ikani and Defwang, 1995). Pigs have unique potentials as possible solutions to Nigerian meat supply situation because of their high fertility rate, short generation interval, high litter size and growth rate, high efficient carcass yield and easy adaptation to environmental conditions (Balogun, 1981, Adekunle, 1995, Ugwu et al., 1997). Despite these attributes, productivity of pigs in Nigeria has been low due to the problems of poor nutrition caused by inadequate, excess or imbalanced nutrient intake, high cost of feedstuff, poor health and management and the effect of the changing climatic conditions alongside its heavy thermal load on the animals which adversely have affected the various stages of the reproductive event (Machebe et al., 2009). These events include delayed puberty, reduced ovulation and lower conception rates, high embryonic and foetal losses, excessively long post-partum anoestrus, poor lactation, high prenatal mortality and poor neonatal performance etc. (Martin, 2012)
Trace minerals/ micronutrients like Zinc, Selenium, Vitamin A, Vitamin E, Copper and Molybdenum have been known to reduce or ameliorate these reproductive challenges in animals. For instance, Vitamin E functions as an intra-cellular antioxidant scavenging for free reactive oxygen and lipid hydroperoxides, and converting them to non-reactive forms, thus maintaining the integrity of membrane phospholipids against oxidative damage and peroxidation (Surai, 1999). Vitamin A is known to reduce delayed puberty, low conception rate, high embryonic mortality and improve libido (Allan et at., 1999, Smith and Somade,
1994). Zinc on the other hand reduces impaired spermatogenesis and aid development of secondary sex organs in males, improves fertility and litter size in multiparous species (Underwood and Suttle 2003). Copper is involved in steriodogenesis and prostaglandins secretion which in turn improves fertility, prevents delayed/depressed oestrus, and abortion/foetal resorption (Smith and Akinbamijo 2000).
Selenium (Se) is an essential element playing an important role in animal reproduction (Surai, 2002). It can be found in the body parts as a part of at least 25 selenoproteins. These selenoproteins are considered to be involved in the regulation of various physiological functions including anti-oxidant protection, regulation of gene expression, thyroid metabolism, immune response, reduction of inflammation and maintenance of sperm structure integrity (Surai, 2002, Arthur and Geoffrey 2003 and Schomburg et al., 2004). There are two main sources of selenium in the diet: organic selenium (mainly selenomethionine) and inorganic selenium (selenite and selenate). Surai (2002) indicated that the organic form of selenium provides more selenium reserves in the body and a more efficient transfer to the egg in poultry and milk in lactating animals.
Feeding selenium to male farm animals have shown that selenium seems to be essential for normal spermatozoa development but little attention has been devoted to female reproductive performance.
1.1 Objectives of the study
The broad objective of this study was to evaluate the effect of dietary selenium supplementation on the reproductive performance of sows.
1.1.2 Specific Objectives
1. To determine the effect of dietary selenium supplementation on the reproductive performance of sows.
2. To determine the effect of selenium supplementation on pre-weaning growth performance of piglets.
3. To evaluate the effect of dietary selenium supplementation on the haematological and oxidative enzyme status of sows.
1.2 Justification of the Study
Pigs have unique potentials as possible solutions to Nigerian meat supply situation because of some attributes like their high fertility rate, short generation interval, high litter size and growth rate, high efficient carcass yield etc. (Balogun, 1981, Adekule, 1995, Ugwu et al., 1997). Despite these attributes, productivity of pigs in Nigeria has been low due to the problems of poor nutrition, poor health and management. The effect of the changing climatic conditions also imposes heavy thermal load on the animals with the pregnant and lactating animals at the greatest risk of being negatively affected because of their high performance level (growth of pregnancy and lactation) (Hahn, 1995).
Regarding selenium and female fertility only sparse information exists and little attention has been devoted to female reproductive performance, and the data are insufficient for drawing appropriate conclusion on its importance.
It therefore becomes justifiable to design a study to determine the impact and the best stage of gestation (second or third trimester) or during lactation for dietary selenium supplementation that will improve the reproductive performance of sows and growth of their piglets without any negative or detrimental effect on the physiology of the animals.
It is believed that the findings of this research if made available to farmers will help farmers appropriate decision on the effectiveness or otherwise of selenium inclusion as dietary supplement in pig diet to improve the reproductive potentials of the animals especially in the tropics where climatic and other environmental variables (nutrition, disease) have hindered pig productivity. It is expected that on adoption of the finding of this research by farmers, pig productivity will improve leading to an adequate supply of animal protein to consumers. It will also lead to the sustainability of food security situation in Nigeria and other developing economies of the world.
This material content is developed to serve as a GUIDE for students to conduct academic research
EFFECTS OF DIETARY SELENIUM SUPPLEMENTATION ON REPRODUCTIVE PERFORMANCE OF SOWS
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