Effects of increasing dietary energy level using carbohydrate or fat supplementation on ovarian activity and some blood parameters in Ghezel ewes

Document Type : Research Paper

Authors

Abstract

Introduction: Excellent reproductive performance is paramount to profitable farm animal production systems. This is particularly true in strict seasonal reproductive systems where animals are expected to establish and maintain pregnancy within a short period of time. Low reproductive performance in seasonal breeders such as sheep and goat was considered as a main economic problem in modern and nomadic production systems. There are numerous research reports on the impact of nutrition on follicular population, folliculogenesis, and ovulation rate in sheep. Feeding is a low-cost system for managing reproduction and ovulation rates in arid and semi-arid regions (Martin et al. 2004). Animal energy balance and its secondary effect on metabolism through its influence on nutrient concentrations, hormones and various growth factors such as calcium, insulin, growth hormone and insulin-like growth factor may be the most important mechanism to justify the effect of energy on processes Reproduction affected the hypothalamic-pituitary-ovarian axis. Dietary energy in pre-conception period is an influential factor in reproductive activities. Also, there are reports about the positive effects of supplementing diets with polyunsaturated essential fatty acids on reproductive performance in farm animals. Fish oil contains EPA and DHA as omega-3 fatty acids and plays a major role in the production of eicosanoids. On the other hand, plant oils rich in omega-6 fatty acids such as linoleic acid have been reported to improve immune status of animals. The positive effects of fat and energy supplementation on the improvements of reproduction in dairy cows are well documented, but the specific effects of omega polyunsaturated fatty acids (n-3 and n-6) on reproductive success in small ruminants have not been examined in detail. While the link between n-3 fatty acids and reproductive markers such as (PGF2α) are well established, evidences for direct effects of high n-3 fatty acids supplementation on measurable reproductive outcomes in ruminants is limited. There is little information regarding the effect of dietary energy level and energy source on reproductive activity in Iranian fat-tailed lambs.This study was carried out to determine the effects of increasing dietary energy level by carbohydrate or fat supplementation using rumen-protected calcium salts of fish oil as omega-3 fatty acid sources or soybean oil as omega-6 fatty acids on ovarian activity and some blood parameters in Ghezel ewes.
Materials and methods: Twelve Ghezel ewes were assigned into four groups with three animals based on a  completely randomized design. Diets were formulated according to small ruminant’s nutrient requirement using Small ruminant nutrition system (SRNS, Texas A&M University, version 1.11.7154.28131). The control group received maintenance energy requirements. While the second experimental groups received a diet with  20% extra energy supplied by barley grain. Calcium salt of fatty acids rich in Omega-3 fatty acids (eicosapentaenoic and docosahexaenoic acid) and Omega-6 (linoleic acid) were partly replaced with barley grain in third and fourth experimental groups, respectively. The estrous cycle of the ewes was synchronized with two consecutive injections of prostaglandin. Ultrasound examination of the ovaries started after second PG injection and continued for three estrous cycles. Through the first cycle, all of the animals received the control diet. Experimental diets were fed through the second and third estrous cycles. The first cycle for each of the experimental groups was considered as the control for study the effects of different dietary treatments. Blood sampling was done on day 12 of the luteal phase of each experimental cycles, four hours after the morning meal and plasma and serum were analyzed for energy-related parameters such as glucose, triacylglycerol’s, insulin, non-esterified fatty acids, beta-hydroxybutyric acid as well as sex hormones.
Results and discussion: Plasma levels of glucose, triacylglycerol’s, non-esterified fatty acids, beta-hydroxybutyric acid, and serum levels of estrogen and progesterone were affected by energy levels in the diet. However, effects of energy source were also significant in the case of glucose, BHBA and hormones levels. Concentrations of glucose, triacylglycerol, HDL, total protein, albumin, urea VLDL, estrogen, and progesterone (p < 0.05) were affected by the experimental treatments and increased with increasing energy levels. The type of energy source (carbohydrate versus fat) showed a significant difference in concentrations of glucose, cholesterol, VLDL, globulin, estrogen, and progesterone (p < 0.05). The highest plasma glucose concentration was in the barley-receiving group. Increasing the dietary energy level resulted in improvement of various energy indices such as the concentration of non-esterified fatty acids and beta-hydroxybutyrate (p < 0.05). Triacylglycerol and HDL concentrations were not significantly different between ewes consuming different energy sources, but increased with increasing dietary energy levels. Supplementing the diet with protected poly-unsaturated fatty acids has resulted in higher plasma unsaturated fatty acids. In this case, energy levels, energy source, and lipid supplementation type exert significant effects. The use of linoleic acid supplementation in this study increased arachidonic acid concentration (P <0.05). Twenty-carbon unsaturated fatty acids are a direct precursor of a large group of active compounds called eicosanoids, including prostaglandins, thromboxanes, leukotrienes, and lipoxanes. Omega-6 fatty acid supplemented diet increased ovulatory follicle diameter in the third cycle of the experiment compared with control cycle. However, omega-3 supplementation decreased it. On the other hand, the follicular waves counts were not influenced.
Conclusion: Results showed that higher energy content or even the energy source could not significantly affect the various parameters of the estrous cycle such as follicular waves count, length of the estrous cycle, follicular diameter, and the number of ovulation in each cycle (P>0.05). Nevertheless, the change in energy level and the source had been exerted significant effects on plasma fatty acids profile and energy-related metabolites (p < 0.05). This study was performed in the reproductive season with the limited number of animals and it seems  that normal body condition of experimental animals, as well as long term dietary inclusion of high energy supplements, have potentials for affecting  the results. Further examination in reproductive and non-reproductive seasons with more replications and also, investigation of the effects of different energy sources and energy levels on reproductive performance could be suggested.

Bao B, Thomas MG, Griffith MK, Burghardt RC and Williams GL, 1995. Steroidogenic activity, insulin-like growth factor-I production, and proliferation of granulosa and theca cells obtained from dominant preovulatory and nonovulatory follicles during the bovine estrous cycle: effects of low-density and high-density lipoproteins. Biology of Reproduction 53: 1271-1279.
Bilby TR, Block J, Do Amaral BC, Sa Filho O, Silvestre FT, Hansen PJ and Thatcher WW, 2006. Effects of dietary unsaturated fatty acids on oocyte quality and follicular development in lactating dairy cows in summer. Journal of Dairy Science 89: 3891-3903.
Bilby TR, Sozzi A, Lopez MM, Silvestre FT, Ealy AD, Staples CR and Thatcher WW, 2006. Pregnancy, bovine somatotropin, and dietary n-3 fatty acids in lactating dairy cows: I. ovarian, conceptus, and growth hormone–insulin-like growth factor system responses. Journal of dairy science 89: 3360-3374.
Calder PC, Yaqoob P, Thies F, Wallace FA and Miles EA,. 2002. Fatty acids and lymphocyte functions. British Journal of Nutrition 87: 31-48.
Chilliard Y, Ferlay A, Mansbridge RM and Doreau M, 2000. Ruminant milk fat plasticity: nutritional control of saturated, polyunsaturated, Trans and conjugated fatty acids. EDP Sciences. In Annales de Zootechnie 49: 181-205.
Daghighkia H and Rahbar B, 2012. Effect of fat supplementation in flushing diets on reproductive performance, blood metabolites and hormones in Ghezel breed ewes. Animal Science Researches Journal (Agricultural Science). 22: 147-160.(in Persian).

Daghigh Kia H, Aslani Kordkandi Gh, Moghaddam Gh, Alijani S and Hosseinkhani A 2012. The effect of flaxseed and soybean on the diet of flushing of reproductive performance of Moghani sheep out of the breeding season. Journal of Animal Sciences Researches (Agricultural Science) 22: 51-63 (in Persian).

Evans AC, Mossa F, Fair T, Lonergan P, Butler ST, Zielak-Steciwko AE and Ireland JJ, 2011. Causes and consequences of the variation in the number of ovarian follicles in cattle. Society for Reproduction and Fertility Supplement 60: 421-429.
FASS, 2010. Guide for the Care and Use of Agricultural Animals in Research and Teaching, 3rd edition. Federation of Animal Science Societies. Champaign, IL, USA
Folch J, Lees M and Stanley GHS, 1957. A simplified method for the isolation and purification of total lipids from animal tissues. Journal of Biological Chemistry 226: 497-509.
Ginther OJ, Kastelic JP and Knopf L, 1989. Composition and characteristics of follicular waves during the bovine estrous cycle. Animal Reproduction Science 20: 187-200.
Grummer RR and Carroll DJ, 1991. Effects of dietary fat on metabolic disorders and reproductive performance of dairy cattle. Journal of Animal Science 69: 3838-3852.
Hagobian TA, Sharoff CG, Stephens BR, Wade GN, Silva JE, Chipkin SR and Braun B, 2009. Effects of exercise on energy-regulating hormones and appetite in men and women. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 296: 233-242.
Holman RT, 1960. The ratio of trienoic: tetraenoic acids in tissue lipids as a measure of essential fatty acid requirement. Journal of Nutrition 70: 405-410.
Howard HJ, Scott RG and Britt JH, 1990. Associations among progesterone, estradiol-17β, oxytocin and prostaglandin in cattle treated with hCG during diestrus to extend corpus luteum function. Prostaglandins 40: 51-70.
Ichihara KI and Fukubayashi Y, 2010. Preparation of fatty acid methyl esters for gas-liquid chromatography. Journal of Lipid Research 51: 635-640.
Iranian Ministry of Agriculture. Production year Book. IT and statistic center. Iranian ministry of agriculture. Tehran, I.R. Iran. 2014. Available at:
           https://www.maj. ir/Index.aspx?page_=form&lang=1&pageid=11583&tempname =amar& amp;sub=65&methodname=showmodulecontent. Accessed March 8, 2019.
Kaduce TL, Spector AA and Bar RS, 1982. Linoleic acid metabolism and prostaglandin production by cultured bovine pulmonary artery endothelial cells. Arteriosclerosis, Thrombosis and Vascular Biology 2: 380-389.
Kiyma Z, Alexander BM, Van Kirk EA, Murdoch WJ, Hallford DM and Moss GE, 2004. Effects of feed restriction on reproductive and metabolic hormones in ewes. Journal of Animal Science 82: 2548-2557.
Martin GB, Milton JTB, Davidson RH, Hunzicker GB, Lindsay DR and Blache D, 2004. Natural methods for increasing reproductive efficiency in small ruminants. Animal Reproduction Science 82: 231-245.
Mattos R, Staples CR, Arteche A, Wiltbank MC, Diaz FJ, Jenkins TC and Thatcher WW, 2004. The effects of feeding fish oil on uterine secretion of PGF 2α, milk composition, and metabolic status of periparturient Holstein cows. Journal of Dairy Science 87: 921-932.
National Research Council. 2007. Nutrient Requirements of Small Ruminants: Sheep, Goats, Cervids, and New World Camelids. Washington, DC: The National Academies Press. https://doi.org/10.17226/11654.
Needleman P, Jakschik BA, Morrison AR and Lefkowith JB, 1986. Arachidonic acid metabolism. Annual Review of Biochemistry 55: 69-102.
Parr RA, Davis IF, Miles MA and Squires TJ, 1993. Feed intake affects metabolic clearance rate of progesterone in sheep. Research in Veterinary Science 55: 306-310.
Rabiee AR and Lean IJ, 2000. Uptake of glucose and cholesterol by the ovary of sheep and cattle and the influence of arterial LH concentrations. Animal Reproduction Science 64: 199-209.
Sewell RF and McDowell LJ, 1966. Essential fatty acid requirement of young swine. Journal of Nutrition 89: 64-68.

SRNS. 2017. Small Ruminant Nutrition System. Texas A& M. Nutrition  models.

Thangavelu G, Colazo MG, Ambrose DJ, Oba M, Okine EK and Dyck MK, 2007. Diets enriched in unsaturated fatty acids enhance early embryonic development in lactating Holstein cows. Theriogenology 68: 949-957.
Viñoles C, Meikle A and Forsberg M, 2004. Accuracy of evaluation of ovarian structures by trans-rectal ultrasonography in ewes. Animal Reproduction Science 80: 69-79.
Viñoles C, Paganoni BL, McNatty KP, Heath DA, Thompson AN, Glover KMM and Martin GB, 2014. Follicle development, endocrine profiles and ovulation rate in adult Merino ewes: effects of early nutrition (pre-and post-natal) and supplementation with lupin grain. Reproduction 147: 101-110.
Zachut M, Arieli A, Lehrer H, Argov N and Moallem U, 2008. Dietary unsaturated fatty acids influence preovulatory follicle characteristics in dairy cows. Reproduction 135: 683-692.
Zieba DA, Murawski M, Schwarz T and Wierzchos E, 2002. Pattern of follicular development in high fecundity Olkuska ewes during the estrous cycle. Reproductive Biology 2: 39-58.