الفهرس 
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Abstract
The current trial investigated the impact of different dietary omega- 6/ omega -3 fatty acids ratios on the productive and reproductive performance of Barki sheep.
Sixty non-pregnant multi-parous Barki ewes with an average age (2-3 years) and an average weight (34.54 kg) as well as twelve Barki rams with an average weight (77.63 kg) were used in this experiment. Animals were healthy. Animals were randomly allotted into 4 equal groups (15 ewes and 3 ram /group). Four experimental diets were formulated during the different stages of sheep reproductive cycle (flushing, early and late pregnancy, and lactation). Animals were allotted into 4 different groups receiving 4 different ratios of omega- 6/ omega- 3 fatty acid (high ratio (5.5:1), medium ratio (4.7:1), low ratio (3.2:1) and very low ratio (1.7:1).
The obtained results are summarized in the following:
• Feeding of rams on different omega-6/omega-3 ratios containing diets did not exhibit considerable impact on the average sperm motility (either mass or individual) and sperm viability (dead or live sperms) (P > 0.05), however these parameters were insignificantly enhanced in the MR and LR- fed rams. The semen volume responded differently as it revealed significant increase (P < 0.05) in the MR relative to the other groups.
• The testosterone hormone concentration was non-significantly increased (P > 0.05) with rams fed on HR and VLR at the commencement of experiment, after 2 weeks and at completion of experiment, while rams fed on LR non-significantly increased (P > 0.05) testosterone level after 1 month. The average testosterone hormone levels were non-significantly increased (P > 0.05) with lowering the omega-6/omega-3 ratios in diet.
• Lowering n-6/n-3 ratio in diet led to a significant increase (P< 0.05) in serum total cholesterol and triglyceride with the highest concentrations in rams fed on VLR. Moreover, feeding on VLR triggered significant elevation (P< 0.05) in the highest concentration on rams fed on LDL and VLDL meanwhile MR fed rams showed the highest CHO/HDL ratio (P< 0.05) compared to the other ratios. Serum NEFA showed no difference among the different experimental ratios (P> 0.05).
• The body weight changes had no difference between different ewe’s groups fed on various n- 6/ n- 3 ratios and the different dietary omega- 6/ omega- 3 ratio had no significant (P≥0.05) effect on dry matter (DM), crude protein, ether extract, ADF and NDF intakes of Barki ewes during flushing and lactation periods.
• The medium or low n- 6/ n- 3 ratios of Barki ewes diet (4.7:1 and 3.2:1 respectively) during flushing period increased pregnancy percentage. The proportion of male: female lambs was non-significantly (P≥0.05) higher (1:0.63) of Barki ewes fed on high n- 6/ n- 3 ratio compared to medium, low and very low ratios (1:2.2, 1:2.2 5 and 1:1 respectively). The medium n- 6/ n- 3 ratio (4.7:1) fed Barki ewes had the highest lambing rate (114.3%), followed by ewes group (109.1%) fed on diet contain very low n- 6/ n- 3 ratio (1.7:1) and the lowest rate (100%) produced by ewes fed on diet contain low n- 6/ n- 3 ratio (3.2:1).
• The serum estrogen concentration of Barki ewes fed different dietary n-6/n-3 ratios had non-significant (P≥0.05) different at the start of flushing period. On the other hand, lowering n-6/n-3 ratio from HR to VLR significantly (P˂0.05) increased serum estrogen level of Barki ewes at the end of flushing, early pregnancy, late pregnancy and during lactation periods and the estrogen increase was in parallel with n-6/n-3 ratio reduction.
• The serum progesterone levels had no significant (P≥0.05) difference between different Barki ewe’s groups at the start of flushing period, while increased (P˂0.05) at the end of flushing period in Barki ewes group fed on ration containing medium, low or very low n-6/n-3 ratios compared to ewes group fed high n-6/n-3 ratio containing ration.
• The serum total lipids concentration of Barki ewes fed medium and low n- 6/ n- 3 ratios showed non-significant (P≥0.05) increased during flushing, early pregnancy, late pregnancy, and lactation periods compared to ewes fed on ration contain high or very low n- 6/ n- 3 ratios. The different n-6/n-3 ratios in Barki ewe’s rations had no significant (P≥0.05) effect on serum triglycerides, CHO, HDL, LDL and VLDL concentrations at the start of flushing period. On the other hand, serum triglycerides concentration significantly (P˂0.05) increased at the end of flushing, early pregnancy, late pregnancy, and lactation periods of Barki ewes fed on medium, low or very low n-6/n-3 ratios containing ration compared to ewes fed on ration contain high n-6/n-3 ratio.
• Barki ewes fed on rations contain medium, low or very low n- 6/n- 3 ratios showed non-significant (P≥0.05) increase in serum cholesterol concentration at the end of flushing, late pregnancy and lactation periods, while significantly (P˂0.05) increased during early pregnancy period compared to ewes fed on ration contain high n-6/n-3 ratio. Moreover, ewes fed on rations contain medium, low or very low n- 6/n- 3 ratios showed significant (P˂0.05) increase in serum HDL and LDL concentration during both early and late pregnancy periods compared to ewes fed on ration contain high n-6/n-3 ratio.
• The different dietary n- 6/ n- 3 ratios had no significant (P≥0.05) effect on serum glucose concentration of Barki ewes at the start of flushing period. Moreover, it was found that medium and low n- 6/ n- 3 ratios non significantly (P≥0.05) increased glucose concentration during end of flushing, early pregnancy, late pregnancy and lactation periods by about (3.8%, 16.9%, 29.8% and 2.8%) and (4.9%, 3.4%, 17.7% and 1.0%) respectively, while very low n-6/n-3 ratio non significantly (P≥0.05) increased glucose concentration during end of flushing, early pregnancy and late pregnancy periods compared to high n- 6/ n- 3 ratio.
• The different dietary n-6/n-3 ratios of Barki ewe’s rations had no significant (P≥0.05) effect on serum NEFA concentration at the start of flushing period and during late pregnancy period. On the other hand, medium, low and very low n-6/n-3 ratios reduced serum NEFA concentration at the end of flushing period and during early pregnancy or lactation periods compared to Barki ewes group fed on high n-6/n-3 ratio containing rations.
• The reduction of n- 6/n- 3 ratio from high (5.5:1) ratio to medium (4.7:1), low (3.2:1) or very low (1.7:1) ratios of Barki ewes ration increased phagocytic activity by about 7.1%, 11.3% and 6.1% respectively, while hand no significant effect on phagocytic index. Reduction of n- 6/n- 3 ratio did not increase RBCs but decreased WBCs of Barki ewes and significantly (P˂ 0.05) reduced WBCs while, increased eosinophil% and had no significant (P≥0.05) effect on neutrophil %, lymphocyte % and monocyte %.
• The different n-6/n-3 ratios in Barki ewe’s diets had no significant (P≥0.05) effect on RBCs, Hb %, PCV %, MCV %, MCH % and MCHC %.
• The rumen pH ranged between 5.54 (low ratio group) and 6.02 (very low ratio) during flushing period and between 5.36 (medium ratio group) and 5.61 (high ratio group) during pregnancy period while, between 5.1 and 5.2 during lactating period. It was found that different n- 6/ n- 3 ratios had no significant (P≥0.05) effect on ruminal pH during flushing and lactating periods. However, during flushing period very low n- 6 / n- 3 ratio fed group tended to have a slightly higher rumen pH value than that of the other groups.
• All reproductive periods dietary n-6/n-3 ratios had no significant (P≥0.05) effect ruminal ammonia concentration, production of ruminal total volatile fatty acids (TVFA) and acetic acid %. of Barki ewes.
• The dietary n- 6/ n- 3 ratios had no significant effect on colostrum protein%, lactose% and solids-not fat%, while density% increased with lowering n- 6/ n- 3 ratios. Moreover, colostrum fat% decreased with n- 6/ n- 3 ratio reduction from high ratio (5.5:1) to medium ratio (4.7:1) or to low ratio (3.2:1).
• The milk fat% generally decreased with decreasing dietary n- 6/ n- 3 ratios except with ewes fed on low ratio (3.2:1) increased milk fat% and milk protein% non-significantly (P≥0.05) decreased with decreasing n- 6/ n- 3 ratios from 5.5:1 to 1.7:1. The hypercholesterolemic saturated fatty acids (sum of C12:0, C14:0 and C16:0) reduced in Barki ewes milk of the current study with decreased dietary n-6: n-3 ratios.
• Decreasing n- 6/ n- 3 ratios from 5.5:1 to 1.7:1 of lactating Barki ewes diet reduced total SFA, while increased total MUFA PUFA. Barki ewes feeding on diets contain medium, low or very low n- 6: n- 3 ratios (respectively) increased C18:1n9c fatty acid in milk by about 3.2%, 15% and 19.9% respectively and increased C18:3n3 fatty acid in Barki ewes milk by about 13.5%, 34.2% and 46.5% respectively compared to fatty acids content in milk produced by ewes fed on high n-6: n-3 ratio (5.5:1) containing diet.
• Feeding Barki ewes on rations with medium, low or very low n- 6/ n- 3 ratios non-significantly increased lamb birth weight by about 2.6%, 6.1% and 6.6% respectively compared to lamb birth weight from ewes fed on high n-6/n-3 ratio containing rations.
• Lambs born from ewes fed on rations contain medium (4.7:1), low (3.2:1) or very low (1.7:1) n- 6/ n- 3 ratios during gestation period showed non-significant (P≥0.05) increase in serum glucose concentration by about 5.2%, 0.5% and 3.7% respectively, while showed non-significant (P≥0.05) reduction in NEFA serum concentration by about 10.3%, 9.3% and 6.4% respectively compared to lambs born from ewes fed on ration contain high (5.5:1) n- 6/ n- 3 ratio.
• Lambs born from ewes fed on rations contain medium (4.7:1), low (3.2:1) or very low (1.7:1) n- 6/ n- 3 ratios during gestation period showed significant (P ˂ 0.05) decrease in serum total protein concentration by about 1.02%, 0.5% and 1.02% respectively, while showed non-significant (P≥0.05) reduction in serum albumin concentration by about 17.18%, 17.42% and 10.02% respectively compared to lambs born from ewes fed on ration contain high (5.5:1) n- 6/ n- 3 ratio, so improved serum globulin concentration.