title: Impacts of calcium addition and different oil types and levels on in vitro rumen fermentation and digestibility.
abstract: This in vitro study was designed to investigate the effects of calcium addition to substrates differing in source and level of oil on fermentation, gas production, and digestibility parameters. Substrates were made from basal mixtures containing three levels of calcium salt (0, 1, and 2% CaCl2) to contain three levels (3, 6, and 9%) of two types (sunflower and soy) of oil. After collecting from two Holstein bulls and mixing with buffer, rumen fluid was used to incubate the resulting 18 mixtures in duplicate. Ionizable calcium, pH and NH3-N concentration were measured during incubation. Gas production was measured at 6, 12, 24, and 48 h after incubation. Kinetics parameters of gas production and in vitro dry matter digestibility (IVDMD) were calculated from regression coefficients of an exponential equation and a linear equation, respectively. Data were analysed using 3-way ANOVA with repeated measure option in which the parameter time was a subplot. Oil type did not affect pH and ionizable calcium concentration. There were linear increases and decreases in pH and ionizable calcium concentration in response to increasing oil and calcium levels, respectively. However, with increasing oil levels there were no interactions between calcium addition and oil level on pH and ionizable calcium concentration. None of the treatments affected NH3-N concentration. The amount of gas produced from substrates containing sunflower oil was greater than soy oil (41.7 vs. 40.5 ml). Cumulative gas production and amount of gas production from insoluble but slowly fermentable portion of the supplemental mixtures linearly decreased and linearly increased as oil and calcium levels increased in the substrates, respectively. However, interactions of calcium addition and oil level on gas production and kinetics of gas production were lacking. Oil type did not affect IVDMD. Despite lacking main effects, interaction of calcium addition and oil level indicated that increasing calcium level alleviated depression in IVDMD resulting from increasing oil level. In conclusion, increasing oil level depressed, whereas calcium addition stimulated ruminal fermentation. Improvement in IVDMD may partially support that calcium addition alleviates the adverse effects of oil and that more calcium is needed when diets are supplemented with increasing amounts of oil.
authors.affiliation: Department of Animal Nutrition and Nutritional Disorders, Faculty of Veterinary Medicine, Selpuk University, Konya, Turkey. ngulsen@selcuk.edu.tr
authors.forename: Nurettin
authors.initials: N
authors.lastname: Gülşen
authors.forename: Huzur Derya
authors.initials: HD
authors.lastname: Umucalilar
authors.forename: Fatma
authors.initials: F
authors.lastname: Inal
authors.forename: Armagan
authors.initials: A
authors.lastname: Hayirli
mesh_terms: D000704:Analysis of Variance; D000821:Animal Feed; D000818:Animals; D002136:Calcium, Dietary / Q000494:pharmacology*; D002417:Cattle / Q000378:metabolism*; D004063:Digestion / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009566:Nitrates / Q000032:analysis; D010938:Plant Oils / Q000494:pharmacology*; D011897:Random Allocation; D012417:Rumen / Q000378:metabolism*; D013024:Soybean Oil / Q000494:pharmacology*; D000074242:Sunflower Oil
chemical_list: D002136:Calcium, Dietary; D005232:Fatty Acids, Volatile; D009566:Nitrates; D010938:Plant Oils; D000074242:Sunflower Oil; D013024:Soybean Oil; C006568:ammonium nitrate