| Abstrakt: |
Introduction: During the transition period, defined in dairy cows and ewes as the three-week period before and three-week weeks after parturition, animals are more susceptible to metabolic disease. Negative energy balance in pregnant ewes during last of gestation could result in fatal pregnancy toxemia and affects ewe and lamb health (Reynolds et al. 2006). Fat supplementation of the diet is an efficient mean to increase energy concentration of diet and modify body weight, body condition score, milk yield, fat content and fatty acid composition in lactating ruminants (Chilliard et al. 2003). The number of studies on sheep milk as responded to added fat is rather limited compared to studies on cows and goats. Supplementing fat in dairy rations to increase energy density has been extensively evaluated in numerous studies over the last a few decades. However, it was evident that production responses to the supplemental fat varied considerably. Many factors might contribute to the various responses, with one of them being the different fat sources (Reynolds et al. 2006, Hervas et al. 2008). Rumen protected fat production is mainly in order to deal with negative effect of fat on fiber digestion, prohibiting biohydrogenation and increasing long chained fatty acids to small intestine. This method was provided some years ago and the major advantage of it is the neutral fatty calcium soap consumed in rumen and improves the level of essential fatty acids (Hess et al. 2008). In some studies, supplementing dairy ewes with a ruminally protected source of trans-10, cis-12 CLA has been associated with increases in milk and milk protein yields (Lock et al. 2006; Husveth et al. 2010; Sinclair et al. 2010). Much of the research attempted to obtain milk fat with healthier properties by increasing milk concentration of specific human health promoting fatty acids. Although mechanisms of action are unclear and its use in humans is controversial, CLA is still of particular interest because of its speculated role in preventing human health problems and increasing the nutritive and therapeutic value of milk (Sinclair et al. 2010). So, this study has also tried to investigate effects of different fat sources and CLA during late-pregnancy and early lactation on performance of Afshari ewes. Material and methods: Fifty Afshari ewes were assigned randomly to one of the five experimental diets with ten replicates in a completely randomized design. Treatments include: 1- control (without fat supplement), 2- 3% Protected fat powder of saturated fatty acids (palm oil), 3- 3% Ca salt of omega-6 fatty acids (soybean oil), 4- 3% Ca salt of omega-3 fatty acids (fish oil), 5- 2% Protected fat powder of saturated fatty acids (palm oil) and 1% CLA. Animals were in experiment 14 days before to 45 days after the parturition and keep individually. Ewes were fed ad libitum and had free access to fresh water. Daily dry matter intake (DMI) recorded and ewes were weighed and BCS was measured weekly. Milk yield were measured weekly. Blood samples were taken from the ewes on d -14, 1 (lambing) and 14. Results and discussion: There was no difference on ewe Initial weight, body weight changes in lambing, body weight after lambing, body weight 35 days post lambing and body weight changes during 35 days post lambing between ewes supplemented with different fat sources. There were no differences between diets for body condition score and body condition score changes. DMI before parturition significantly decreased by feeding Ca salt of different fat sources (P<0.01), but DMI after parturition increase in ewes fed Ca salt of fatty acids (P<0.01). Supplementation with Ca salt of omega-3 fatty acids (fish oil) and CLA increased milk yield (P<0.01). Protected fat powder of saturated fatty acids increased fat content of milk (P<0.05), but unsaturated fatty acids not affected milk fat concentration. Other composition of the milk and colostrum were not affected by the treatments. One week before lambing, plasma concentration of cholesterol was greater for Ca salt of omega-3 fatty acids (fish oil) ewes as compared with the control ewes (P<0.05). Plasma concentrations of glucose, protein, albumin and globulin not affected by treatments. Plasma concentration of cholesterol, 24 h after lambing, increased in Ca salt of omega-6 fatty acids diet and decreased in Ca salt of omega-3 fatty acids diet (P<0.05). The concentrations of cholesterol, glucose, protein, albumin, and globulin in blood plasma were not affected by feeding different fat sources during the two weeks after lambing. Conclusion: Supplementing Ca salts of fatty acids to the peripartum diets increased DMI after parturition and Ca salts of omega-3 fatty acids (fish oil) and CLA increased milk yield and improved Afshari ewes performance. [ABSTRACT FROM AUTHOR] |
