S. R. Miraei Ashtiani, P. Zamani, A. Nikkhah, M. Moradi Shahrbabak, A. Naserian, F. Akbari,
Volume 9, Issue 4 (winter 2006)
Abstract
Improvement of feed efficiency in dairy farming economically has a great importance. In this study, the genetic parameters of net energy efficiency and its relationships with milk yield, 3.2% fat corrected milk, body weight, gross income and income over feed costs were investigated, by the 2589 monthly records collected from the 723 lactating cows in the 3 herds. The different requirements of energy were estimated, by the National Research Council (NRC) models. A general linear model was employed for determining significant factors affecting each trait. The genetic parameters were estimated by a multivariate analysis with the derivative free approach of restricted maximum likelihood algorithm. The animal models contained the fixed effects of herd-year-season, parity number and stage of lactation, the regression coefficients of each trait on the dietary levels of rumen undegradable protein and metabolizable energy, and the random effects of animal additive genetic, permanent environment and residuals. The heritability of milk yield, 3.2 percent fat corrected milk, body weight, net energy efficiency, gross income and income over feed cost, were estimates 0.31, 0.32, 0.30, 0.34, 0.24 and 0.29 respectively. The results of this study indicated that the direct selection for net energy efficiency might genetically improve the feed efficiency. It also seems that the selection for fat corrected milk may be effective for the indirect improvement of feed efficiency and economic performance of dairy cows.
A Bohloli, A Naserian, R Valizadeh, F Eftekhari,
Volume 13, Issue 47 (4-2009)
Abstract
Eight multiparous Holstein dairy cows with 634±44 BW, 57±6 DIM, and 46.7±3.1 kg daily milk yield were assigned to a duplicated 4×4 Latin square design for 21-day periods (adaptation, 14d sample collection, 7d). The treatment diets were: 1) no pistachio by-product (control), 2) 5% of pistachio by-product, 3) 10% pistachio by-product and 4) 15% pistachio by-product. Corn silage in control diet was replaced with pistachio by-product. The blood metabolites (2h after feeding), DMI, daily milk yield and milk compositions were not affected by the treatment diets. The economically corrected milk (ECM) and fat corrected milk (FCM) were decreased linearly by increasing pistachio by-product in the diet (P<0.1). By increasing the by-product level in the diet, digestibility of DM, OM, NDF and ADF were decreased linearly (P<0.05). Daily rumination and chewing activity alone or per DMI, NDFI or ADFI were linearly decreased when the by-product level increased in the diet (P<0.1). The results showed that the pistachio by-product does not seem to be suitable for complete replacing of the roughages in the diet and it can be used as a part of forage in the diet up to 10% of DMI.
M. Naserian, A. Masjedi,
Volume 21, Issue 4 (Winter 2018)
Abstract
River bend due to particular pattern, called 'Vortex Flow,' has greater erosion than straight path. Occurrence of scour around bridge abutment on curved paths is one of the main reasons for destruction of bridges. Riprap is one of the methods to control the scouring around the bridge abutment. The purpose of this study was to assess stability of the riprap around the bridge abutment at 180 degree river bend. In order to study stability of riprap around the bridge abutment, experiments were done in a laboratory flume made of Plexiglas under 180 degree bend, 2.8 m in central radius, 0.6 m in width and R/B=4.67. In this research, several experiments were done by placing a bridge abutment with vertical winged wall made of Plexiglas surrounded by a series of riprap. Experiments were done by three different types of riprap with different density 1.7, 2.1 and 2.42, four different diameters 4.76, 9.52, 12.7 and 19.1 mm and four rates of discharge under pure water condition. In each experiment, flow depth was measured in terms of moving threshold and failure threshold and then the formulas were calculated by using data obtained. The results showed that the relative diameter of riprap increased with increasing Froude number in terms of moving threshold and failure threshold. Finally, the suitable formula to estimate diameter of riprap around the bridge abutment at 180 degree bend were presented in terms of moving threshold and failure threshold.
