فهرست مطالب فرزاد عبدالله زاده

This study was conducted to investigate the effects of replacement of soybean meal with canola meal and corn processing on productive performance of Holstein dairy cows. Twelve Holstein cows (milk yield= 46±3 kg/d) were assigned to a replicated 4×4 Latin square design with a 2×2 factorial arrangement of treatments. Factor 1 was corn processing method, ground corn or steam flaked corn, and factor 2 was two ratio canola meal to soybean meal (50:50 or 100:0). No significant interactions of main treatment effects occurred for lactation performance data. Dry matter intake and milk production was not affected by replacement of soybean meal with canola meal. Milk compounds concentration was not affected by this replacement. Substitution of hundred percent of soybean meal with canola meal in the diet decreased the apparent digestibility of the dry matter. Feed intake was decrease when the cows received steam flaked corn compared with those receiving ground corn. Milk fat content decreased but milk protein content increased in cows fed steam flaked compared with those fed ground corn. Although these results showed no interaction effects of replacement of soybean meal with canola meal and corn processing method on performance, higher canola meal ratio and steam flaked corn improved feed efficiency and has a positive effect on the metabolism of nitrogen and energy, so recommended to fed in high-yielding cows under the conditions of this experiment.

Previous studies comparing the effects of soybean meal versus canola meal have shown that canola meal improvement DMI, nitrogen (N) utilization and performance when fed to lactating dairy cows. Considering the high price of soybean meal compared to canola meal and the limited studies conducted to investigate the effect of different levels of replacement, the objectives of the present study were to evaluate the effects of replacing soybean meal with canola meal at different levels on performance, rumen and blood parameters in early lactation Holstein cows.

To evaluate the effects of replacing soybean meal with canola meal at different levels on performance, ruminal and blood parameters, twelve multiparous Holstein cows in early lactation were used in a replicated 4×4 Latin square design with 4 treatments. Treatments including different levels of replacement of soybean meal with canola meal in the diet were: 1) Soybean meal as the main source of dietary protein (0% of canola meal), 2) Replacing 50% soybean meal with canola meal in diet and 3) Canola meal as the main source of dietary protein (0% of soybean meal). Feed intake and milk production were recorded for each cow during the last 6 days of the period. Rumen samples were taken from cows on the last day of each experimental period to measure the concentrations of volatile fatty acids and ammonia nitrogen. Blood samples were also taken at the end of each experimental period to determine plasma concentrations of glucose, triglycerides, non-esterified fatty acids, beta-hydroxybutyrate, total protein, albumin, globulin and blood urea nitrogen.

Dry matter was not affected by treatments. Milk production was significantly higher in cows fed diets containing canola meal than in cows fed diet containing 100% soybean meal. The use of different levels of canola meal in the diet caused a significant reduction in the MUN concentration. The other milk compounds concentration were not affected by experimental treatments. The use of combination of soybean meal and canola meal in the diet together increased the apparent digestibility of the dry matter. The apparent digestibility of the protein was increased by feeding canola meal compared to soybean meal. Ruminal pH and ruminal volatile fatty acids concentration were not significantly affected by experimental diets. Except for albumin, none of the blood parameters were affected by the experimental treatments. Concentration of plasma albumin was greater in cows fed diet containing 100% canola meal compared to cows fed two other diets.

In conclusion, the results of this study indicate that replacing sobean meal with canola meal at 50% and 100% level in early lactating cows improved milk production, efficiency of intake nitrogen and apparent digestibility of dry matter and protein.