مجله پژوهش در نشخوار کنندگان
سال پنجم شماره 1 (بهار 1396)

Heat-stressed dairy cows are bioenergetically similar to early-lactation cows in that dietary energy may be insufficient to support maximum milk and production of milk components. Milk yield of heat-stressed dairy cows is usually decreased during the summer; therefore, increasing performance of cows is of particular interest. Fat supplementation is a common practice for increasing energy density in diets fed to high-producing dairy cows without sacrificing fiber content. In a very limited research studies, the use of Casalts of unsaturated fatty acids vs. saturated palm fatty acids has been investigated in the diet of heat-stressed dairy cows. Also, it has been shown that response to fat supplement can be related to production level. Hence, the object of this experiment was to investigate the effect of production level, source of fat supplement, and their interaction on milk yield and milk composition, nutrient digestibility, and blood biochemical parameters of heat-stressed primiparous Holstein cows.
Fifty-six primiparous Holstein cows were used in two separated group pens. Animals were blocked into two groups of high- (13474.7 kg) and medium-yielding (10438.1 kg) cows according to milk production and received one of two experimental diets containing either high palmitic acid palm fat or Ca-salts of unsaturated fatty acids both at 2.8 percentage of dietary dry matter. Temperature-humidity index and milk yield were recorded daily, and milk composition, nutrient digestibility, blood parameters, and complete blood count were measured every two weeks.
The average maximum temperature-humidity index was 75.50 over the experimental period that indicates cows experienced a mild to medium degree of heat stress. Main treatment effects interacted for raw milk yield (P = 0.03), 3.5% fat-corrected milk yield (P = 0.02), and milk fat yield (P = 0.02). Production performance and milk fat yield was greater for high-yielding cows fed palm fat relative to high-yielding cows fed Ca-salts of fatty acids, whereas source of fat supplement did not affect milk yield and milk fat yield in medium-yielding cows. Source of fat supplement did not affect nutrient digestibility. Irrespective of production level, concentration of blood cholesterol was greater for cows fed palm fat relative to cows fed Ca-salts of fatty acids. Also, concentrations of tri-glyceride, high density lipoproteins, very low density lipoproteins, and blood urea nitrogen tended to increase in cows fed palm fat. Source of fat supplement did not affect blood cells count (white blood cells, red blood cells, and platelets) and differential white cell count.
Source of fat supplement did not affect production performance of heat-stressed medium-yielding cows but palm fat supplement increased milk and milk fat production in high-yielding cows.

In recent years, determination of the effects of probiotics on health and animal performance, due to concerns about antibiotics and growth stimulants in animal feed is considered. Therefore, effects of two kinds of probiotics, as a supplement to milk, on performance, ruminal and blood parameters in Holstein male calves was investigated.
Twenty-four newborn male Holstein calves were assigned to four experimental treatments in a completely randomized design for 75 days. Treatments were included as: 1) feeding milk without any additive (control group) 2) feeding milk with 2 gr Protexin probiotic/day, 3) feeding milk with 2 gr probiotic (containing Saccharomyces cerevisiae)/day and 4) feeding milk with 1 gr Protexin 1 gr Saccharomyces cerevisiae yeast/day. Feeding the colostrum was performed immediately after birth for three days. Water and calf starter were offered ad libitum. Ruminal fluid and blood samples were collected on days 30, 60 and 75. Feed intake and calves weight were measured daily and weekly respectively. Intakes of starter and weight gain were recorded daily
Feed intake, daily weight gain, feed conversion ratio, digestibility coefficients of nutrients, the concentration of volatile fatty acids, ruminal pH and growth parameters were affected by treatments (P In this experiment, ruminal fluid pH showed a higher stability in group that received the mixture of probiotics. Also, health status, body weight gain, digestibility coefficients of nutrients, blood and ruminal parameters were more favorable in this group. In total, consumption of two probiotics had positive effects on blood and ruminal parameters.

The aim of this study was to investigate the parameters related to replacement percentage and revenue obtained by maintenance of dairy cows through production system optimization. The optimum replacement decisions are known as one of the factors affecting the profitability of livestock which are directly affected by fluctuations in milk prices, the price of carcass and replacement costs. When the current value of future cash flows of cows and alternatives are calculated, the optimal decision is to maintain the animal which its current value is higher which represent the additional benefit from maintenance time till replacement optimum time. It takes almost two production years till an alternative cow return its production and breeding costs and increase revenue and profit. Long life reduces replacement costs in cattle. Furthermore, it increases the generation refresh interval, shifts the cattle age toward older cows, and consequently the cattle average production will be increased due to increasing cows with higher lactation periods.
In this study, using MATLAB programming language, a number of programs designed to simulate cattle bio-economic system then the revenues and costs were estimated in the system. In order to calculate the optimum life of the herd and the rate of replacement, possible dynamic programming method was used, as well. Dairy cow defined by state variables including lactation period, milk production capacity and different scenarios in late pregnancy. At each stage, dairy cows classified by condition variables including three production levels (low, Medium and high production) and reproductive performance in four levels with calving interval of 494, 454, 414 and 534 days. To evaluate the effect of changes in input values on model response, sensitivity test was used.
The results showed that by increasing the price of heifers, fewer cows were removed and optimal cattle life was increased and the replacement rate decreased. Milk price reduction resulted in increased cattle optimum life and less cow removal which was associated with low rates of replacement. By increasing the discount factor (discount rate reduction) the percentage of removed cows was raised and optimum life was decreased, in contrast, the replacement rate was increased. Model results in the uncertainty state of production system showed that each parameter that causes increasing the replacement percentage, resulted in the reduction of average revenue from RPO animal maintenance. Results showed that increase in the heifer price and feed average cost, on the contrary, the reduction in cattle average production, removed cow price, calf and milk price, the optimum life increased and the number of removed cows reduced. Therefore, the maintenance value of cows in the cattle were higher than the state of which the heifer price and feed costs were low and cattle average production, calf price, milk price and removed cow price were high.
Two major factors affecting the culling rate were average herd production and the cost of replacement heifers. Fluctuation in the cost of feeding and calves did not affected cow-culling rate, significantly. Optimal replacement policies mainly depend on breeding or purchasing costs of alternative heifers rather than residual costs of the cow (removed cow price). The high rate of heifer replacement causes that the ranchman to be deprived of one of the most important revenue sources (the sale of surplus heifers). Then, by increasing the rate of replacement in cattle, cattle average age will be reduced and most of the cows will be culled before reaching their maximum production capacity. Therefore, on condition that replacement of cows take place, not only no revenue will be obtained but also rearing cost will be added since calving.

Genetic improvement of dairy cattle has been successful during the second half of the 20th century, using pedigree and performance data. Genomic selection can improve the rate of this progress by reducing generation interval and increasing the accuracy of estimated breeding values at birth. There are many issues about using genomic evaluation. In the current study, some strategies were compared to inspect the effects of using superior animals as training set on the accuracy of genomic selection for high and low heritability traits.
For each individual, three chromosomes each with 1000 equally-spaced SNPs (each 0.1 cM one SNP) were simulated. For 50 generations, random mating was done to create enough linkage disequilibrium. In generation 51, the population size was expanded to 4000 individuals. There was this population size, until generation 55. In these generations, 5% of superior bulls and 80% of superior cows from each generation were used as the parents of the next generation. Animals in generation 55 (generation five) were validation group and animals in generations 51-54 (generations one to four) were training set. In strategy one (or first strategy), superior and inferior animals, in strategy two (or two strategy), superior animals and in strategy three (or two strategy), a random sample of the population were used as the training group. This research was done for traits with low (0.1) and high (0.5) heritabilities.
The results showed that the accuracy of genomic evaluation in strategy one was better than strategy two and strategy three. When the ratio and the number of animals in the training set were increased, the difference between the three strategies tended to decrease. For example, for traits with heritability of 10%, using 20% of animals from generations one to four, resulted in 29% difference between strategy one and two; in the same situation, using 40% of animals resulted in 14% difference between these strategies. The accuracy of genomic evaluation for the traits with high heritability of all strategies was higher and the difference between strategies was lower for these traits. For example, when 40% of animals of generations one to four were considered as training set, the difference between strategy 1 and 2, for trait with heritability of 0.1 was 14% and for trait with heritability of 0.5 was 4%.
Using only superior animals in the training group could decrease the accuracy of genomic evaluation. This effect was lower for high heritable traits. Using more animals would alleviate this effect by increasing total genetic variation explained by markers.

Chromium (Cr) plays an important role in ruminant’s metabolism. Situations such as accelerating growth, stress and low bioavailability of Cr in feedstuffs, result in depletion of chromium stores of body, therefore, metabolic disorders and growth retardation occurs. In addition, L-carnitine (LC), a compound of lysine and methionine, is involved in many metabolic processes. It affects energy production and performance by influencing lipid metabolism. Using Cr and LC together, a positive interaction has been reported on lipids and carbohydrates metabolism in some species. Therefore, the aim of this study was to evaluate the effect of organic chromium in form of chromium methionine (Cr-Met) and L-carnitine as a dietary supplement for feedlot lambs on growth performance, glucose metabolism and some blood parameters.
Material and This experiment was performed for 60 days with twentyfour 3-4 month-old male lambs in a completely randomized design (CRD) with four treatments of six lambs each. The treatments were included: 1- control (basal diet) 2- treatment of chromium (Cr) (500 µg Cr per lamb per day) 3- treatment of L-carnitine (LC) (500 mg L-carnitine per lamb per day) 4- treatment of chromium and L-carnitine (Cr × LC) (500 µg Cr and 500 mg of LC per lamb per day). Supplements were added to the basal diet as topdress. At the end of experiment, feed intake, average daily gain (ADG) and feed conversion ratio (FCR) were calculated. In order to evaluate blood metabolites and rumen liquid parameters, blood and rumen liquid samples were taken at the end of experiment. Four lambs randomly were selected from each groups for intravenous glucose tolerance test (IVGTT). For this purpose, 0.5 ml/Kg BW dextrose (50%) was infused and blood samples were taken at 5, 10, 20, 30, 40, 60, 80, 100 and 120 min after glucose infusion, Then glucose clearance rate (CR), half-life (t1/2) and area under curve (AUC) was calculated.
Feed intake, ADG and FCR and also rumen volatile fatty acids and ammonium was not different between treatments (P>0.05). Interactions of chromium and L-carnitine for performance parameters and also rumen volatile fatty acids and ammonium were not significant (P>0.05). High density lipoproteins (HDL) in treatments two and four was significantly higher in compared to treatments three and one (P0.05). Activity of alanine aminotransferase (ALT) was lower in treatments three and four than treatments one and two (P0.05). Area under curve was lower in treatment three in compared to treatment one and four (P0.05).
Results of this experiments showed that, adding chromium and Lcarnitine to feedlot lambs diet (the concentrations used in this study) did not impact fattening performance, but resulted in an increase in HDL and improvement of glucose metabolism.

Future of dairy herds greatly depends on a standard and suitable calf rearing. Improving health and welfare parameters of calves will be resulted in rearing potent heifers in milk production and calving. Moreover, it is better to approach a maximum efficiency of calf rearing with hazardless methods and minimum side effects. Considering antibiotics resistance and growth hormones remnants in animal bodies, prebiotics are fascinating alternatives to be evaluated.
Twenty-four female Holstein calves, aging 18±3 days and body weight of 36±4 kg, were randomly assigned to groups including milk without additive, milk plus 3.5 g/day inulin and milk plus 7 g/day inulin so as to evaluation effect of using inulin as a prebiotic on growth performance, blood parameters and colonic microbial population of suckling calves. Experiment was carried out in a one-week adaptation followed by a six weeks measuring and recording period. Claves were weaned when they consumed 900 grams of starter (dry matter). Dry matter intake and feces score monitoring were recorded daily, and calves were weighed weekly. Feces sampling and blood sampling were done in (third and sixth) and (second, fourth and sixth) weeks of experiment, respectively.
There were no significant differences among groups in dry matter intake, average daily gain and feed conversion rate. Adding inulin prebiotic had no significant effect on blood parameters, although cholesterol and triglyceride concentration showed a trend toward reduction in groups receiving inulin. Feces pH and lactobacillus and coliform bacteria count did not differ among treatments.
Results of present study showed that supplemented milk with inulin oligosaccharide for six weeks had no significant effect on grows performance, dry matter intake, feed conversion rate, lactobacillus and coliform bacteria count, feces pH and blood parameters of Holstein suckling calves.

It has been demonstrated that in acidosis condition due to transferring some metabolites from the rumen to blood, total metabolism could be changed. But relative change in blood metabolites and their relationship with behavior and performance of animal are not clear. The study investigated the relationship of the change in blood metabolites and the occurrence of acidosis to find easy to measure indicators.
Nine multiparous cows (650±56 kg BW; mean±SD) averaging 102±13 days in milk and producing 54±6 kg/d were randomly assigned to a triplicate 3 × 3 Latin square. During each 21-d period, cows were offered one of three total mixed rations that varied in diet fermentability. The three levels of diet fermentability were achieved by increasing the proportion of pellets containing ground wheat and barley in the dietary DM from 11.7%, to 23.3% and 35.0% by replacing ground corn grain. Each period had 14 d of adaptation and 7 d of sampling. Rumen pH and VFA profiles, feed intake, sorting index, chewing activity, milk production and efficiency, and blood metabolites (measured before and 4 h after morning feeding) were measured. The significant correlation between the blood metabolite and aforementioned variable were considered.
The result of this study showed the concentration of serum amyloid A measured 4 h after morning feeding was correlated with rumen pH (r=-0.45) and total VFA concentrations (r=0.51). Also, the concentration of aspartate amino transferase in the blood measured before morning feeding was significantly correlated with the proportion of rumen VFA. The metabolite along with alkaline phosphatase that measured 4 h after morning feeding were correlated with most variables of chewing activities (0.38≤r≤0.57), milk fat production (-0.61≤r≤-0.44) and feed efficiency (r=0.43). The concentration of cholesterol measured at 4 h post feeding was strongly correlated with most indicators of feed intake, milk production and its efficiency (0.57≤r≤0.77). Also, the concentration of glucose in the blood measured 4 h after morning feeding was correlated with feed intake at early time after morning feeding (r=-0.55). Moreover, the concentration of antioxidant in the blood measured before morning feeding was related to protein percentage (r=-0.55), milk production (r=0.57) and its efficiency (r=0.44). There were no clear relationships between blood metabolites and sorting index.
Overall, according to results it could be concluded that blood metabolites had a strong relationship with indicators of rumen acidosis and the concentration of alkaline phosphatase and aspartate amino transferase were a good indicators for predicting acidosis and relative consequences.

Corn steep liquor (CSL) contains high amount of protein (42% DM basis) which is high in soluble protein ratio. This feedstuff is derived from the corn processing and has contain relatively high concentration of soluble protein. Despite previous studies evaluated the inclusion of CSL as protein source in diets, but synchronized inclusion of this feedstuff with different energy sources (starch) need more research. The effects of synchronization of CSL with different starch containing sources (barley, corn and wheat) on performance, blood metabolites and ruminal enzymes in Farahani fattening lambs was evaluated.
Eighteen Farahani lambs averaging BW 32 ± 3 kg (SD) were allocated in three different experimental treatments (6 lambs/each) in completely randomized design in a 9 weeks fattening trial. The basal diet has contained similar amount of CSL (10% DM basis) and different starch source was offered in different experimental treatments as follow; 1) barley grain (BG); 2) corn grain (CG); and 3) wheat grain (WG). Other dietary ingredients were constant among treatments.
The results showed that the feed intake (P = 0.01) as well as daily gain (P = 0.05) differed among treatments with the greatest amounts of both intake and gain for corn grain fed lambs. Conversely wheat grain fed lambs showed the lowest intake and gain in the current study. The feed conversion ratio was constant among treatments. The corn fed lambs had the greatest ruminating time in the current study. The CG fed lambs had tended to have greater glucose (P = 0.09), however lower BHBA (P = 0.03) concentration in blood. Feeding barley grain with CS resulted the greatest urea nitrogen concentration in blood (P = 0.01). The rumen pH was reduced in barley fed lambs and the greatest ruminal pH value was obtained in lambs fed corn grain. No one of the measured ruminal fluid enzymes (CMCase, MCCas) were differed among treatments.
In conclusion, results revealed that inclusion of CSL as high soluble protein source is more efficient if synchronized with corn grain in comparison with barley or wheat grains in fattening lamb production.

Understanding and description of degradation mechanism in digestive ecosystem of horse especially posterior part of gastrointestinal tract (GIT) is of great importance in proper nourishment. Despite its importance in host nutritional status, fermentation in posterior part of GIT is not completely understood and studies on contribution of posterior microbial population in nitrogen and energy requirements were rarely investigated. The literature is rather unanimous on ecology and microbial diversity in GIT of horses that based on microbial culture. Most of the time, the microbial culture is timeconsuming and difficult to implement and may include some part of microbial diversity. However, modern molecular methods like real-time PCR are independent tool of microbial culture which specifies varieties of bacterial species and total bacterial count with high accuracy and sensitivity. The aim of current study was to investigate the effect of dietary fiber and starch level and processing type on relative changes of microbial population in GIT.
In order to do this experiment, eight 6-12 years old Turkmen male horse with body weight of 270-300 kg were used. The rations were placed in two meals in the morning and evening and water was freely available to them. Two base rations containing high fiber and high starch were used for horses. Treatments included: 1) high fiber diet with steam flake barley (A), 2) high fiber diet with pelleted barley (B), 3) high starch diet with steam flake barley (C) and 4) high starch diet with pelleted barley (D). The experiment was conducted in a changeover design with four treatments and four periods, each period including 14 days of adaptation to the new diet and 7 days of sampling. Samples from feces of horses were collected on the last day of each period and stored in a freezer at -80 °C until the microbial population was determined. DNA extraction was done by phenol-chloroform method. In order to clone the genes, after extraction of their sequence from the NCBI database for each gene, a pair of primers (lead and follower primers) was designed using the AllelID software. Finally, the relative quantity of bacteria and protozoa was determined using a polymerase chain reaction method in real time.
Protozoa population in the diet containing high starch and flaked barley was higher than other diets and had a significant difference. The high starch diet containing pelleted barley and the high fiber diet containing flaked barley were 54 and 106 times higher than the high fiber diet and pelleted barley, respectively. The relative populations of Streptococcus bovis showed a significant increase in the high starch diets and flaked barley compared to other diets. In this experiment, the high fiber diet, with flaked barley increased the Ruminococcus flavefaciens 1400000 times relative to the high starch and flaked barley diet. The difference between high-fiber diet with pelleted barley and high-starch diet with flaked barley was also significant, and the concentration of Ruminococcus flavefaciens in a highfiber diet with pelleted barley was 6000 times of high starch diet and flaked barley. The highest concentrations of Fibrobacter succinogen observed in the high fiber with pelleted barley diet, that were 33800 times compared to high starch diets and flaked barley. In the next stage, there were high dietary fiber and pelleted barley, high-starch diet and flaked barley that were 1690 and 1470 times higher than high starch diet and flaked barley, but these two diets did not differ significantly in terms of concentration of Fibrobacter succinogen.
The results of this study showed that the use of diet high in starch and flaked barley increases the relative population of Streptococcus bovis and protozoan populations.