فهرست مطالب دکتر حسین امیدی میرزایی

The current study was conducted to evaluate the interaction between different levels of protein and feed structure on performance in calves. Accordingly, a total number of 48 Holstein calves (A mixture of both sexes) were randomly assigned to 4 dietary treatments with 12 replicate pens, based on a factorial design. Dietary treatments consisted of 1) ground starter with % 18 CP, 2) ground starter with % 22 CP, 3) texture starter with % 18 CP and 4) texture starter with % 22 CP. In this study, digestibility of nutrients, rumen and blood parameters of suckling calves were measured. The interaction between the main effects for the amount of beta-hydroxybutyrate in the blood on the 70th day of the experiment was significant (p < 0.05). In this way, flour feed with 18% protein had the lowest amount of beta-hydroxybutyrate. The interaction between the main effects for other blood parameters was not significant (p < 0.05). The interaction between the main effects for ruminal parameters and digestibility was not affected by the form and protein level of the initial feed (p < 0.05). In general, there was no significant difference between the textured feed and coarse grinding, and the protein level of 18 and 22% was not observed in the tested groups.

The present study was conducted to evaluate the interactions between forage source (alfalfa hay vs. wheat straw) and particle size (fine vs. large) on growth performance, starter intake and ruminal fermentation of Holstein dairy calves. For this purpose, 48 Holstein dairy calves in a completely randomized block design (6 males and 6 females for each treatment) with 2 × 2 factorial arrangements were allocated to experimental diets including: 1) alfalfa hay with fine particle size, 2) alfalfa hay with long particle size, 3) wheat straw with fine particle size, and 4) wheat straw with long particle size. Calves entered the trial on d 4 and the trial lasted on d 70 of the age. Results showed that there was no interaction between forage source and particle size on growth performance, starter intake and feed efficiency of Holstein dairy calves during the all three periods. Skeletal growth characteristics were not affected by experimental diets. Results indicate that ruminal pH, total volatile fatty acids, acetate, propionate, butyrate and valerate molar proportions were similar across treatments. In general, our findings indicate that the different source and particle size of forage had similar effects on performance, skeletal growth and ruminal fermentation in the Holstein dairy calves.

The future of any dairy farm depends on the success of the female calf rearing. In recent years, new aspects the use of forage in the starter feed has been discussed. Studies have reported that a starter without forage leads to the development of abnormally shaped villi in the calf's rumen, which will negatively affect rumen growth and development. However, today there are different opinions about the use of forages in the starter feed for dairy calves so that some researchers believe that the presence of forages in the starter feed reduces the performance of dairy calves. In this study, the effect of 15% alfalfa forage level in the ground starter diet on functional responses and skeletal growth traits of dairy calves fed a step-down milk feeding procedure was investigated.

The experiment was designed and conducted in a completely randomized design using 30 Holstein female calves (15 calves per treatment). Experimental treatments were as follows: 1- ground starter diet without forage (control) 2- ground starter diet consisted of 15% alfalfa hay. The milk feeding pattern was the same for both treatments and was a step-down procedure as 2 times per day(6 liters to 30 days, 4 liters to 45 days, and 2 liters to 56 days). All calves were weaned on day 56 of the experiment and keep until day 70 in the experiment. Feed intake and weight gain were measured and recorded weekly. Skeletal growth traits were measured on days 1, 56, and 70 of the experiment. Rumen fluid was measured on day 60 of the experiment. Statistical analysis was performed using the Mixed procedure as repeated measures for 3 periods (before weaning, after weaning, and the whole period).

The results of this study showed that adding 15% alfalfa hay to the starter feed did not have a significant effect on the mean daily weight gain, feed efficiency, and skeletal growth traits of dairy calves. Calves that received the forage treatment had higher starter feed intake in the post-weaning period than the starter diet without forage (P <0.05). Acetate concentration was higher for 15% forage and propionate concentration was higher for the control treatment (P <0.05). Rumen pH also tended to increase in calves consuming forage.

Feeding 15% of alfalfa forage mixed with the ground starter feed improved their feed intake after weaning. These results indicate that the use of alfalfa forage in the ground starter diet reduces the stress of weaning and improves rumen development.

This study was conducted to investigate the effects of supplementing dairy cows diet with various levels of commercial chestnut condensed tannins (CT) supplement (Silvafeed), on in vitro gas production (GP) and fermentation parameters, nutrients digestibility and activity of rumen microbial enzymes in vitro using rumen liquor of cow. Dietary treatments were control diet (without CT) and supplementing control diet with CT at the levels of 0.45, 0.90 and 1.35 g per kg dietary dry matter (DM). Inclusion levels of dietary tannins were based on recommendation of manufacturer. Results showed that GP at all of incubation times, potential (b) and rate (c) of GP were not affected by experimental treatments (P>0.05). Except for ammonia nitrogen concentration and microbial protein production which were decreased and increased with increasing rate of CT in the diet respectively (P<0.05), while the other fermentation parameters were unchanged by incubation of experimental diets (P>0.05). Activity of fibrolytic enzymes such a carboxymethyl cellulase, microcrystalline cellulase and filter paper-degrading activity were not affected by supplementing diet with CT (P>0.05), while rumen protease activity was decreased linearly with enhancing level of CT in the diet (P<0.05). In conclusion, the results of present study revealed that adding condensed tannins to dairy cows diet up to 1.35 g/kg dietary DM improved nitrogen metabolism in the rumen, and this could reduce the requirements for dietary rumen undegradable protein.

The aim of this study was to consider reproductive performance parameters and blood progesterone concentration changes in high-producing dairy cows (39±2 kg per day) after artificial insemination, in summer and winter. 270 heads of Holstein dairy cattle were choose in three big dairy farms, and blood samples were collected at days seven, ten and fourteen after artificial insemination. Temperature-humidity index was calculated according to one proposed formula (Dikmen and Hansen, 2009). The results showed that the maximum temperature–humidity index(THI) was 77.35 and 57.47 in summer and winter respectively. Pregnancy rates in cows inseminated during the winter months was significantly higher (p