مجله تولیدات دامی
سال بیست و پنجم شماره 1 (بهار 1402)

The present study was conducted in order to select effective markers in breed discrimination and compare the performance of SNP marker selection methods with the data of 304 animals from 14 different breeds that were genotyped using the Illumina SNP50K marker panel. Knowledge of genetic structure are very important for better understanding of genetic changes in genomic studies. The information content of each marker is used as an index for selecting markers in reducing the size of marker panels. To estimate the information content of each marker, the following selection methods were used: Fst (pairwise & global), Theta, Delta, D, Gst, G'st, G"st and Principal Component Analysis. In this study, the logarithm of the likelihood ratio was used to select markers. According to the results, all selection methods for identifying markers had similar performance. The number of common markers between the methods was at least 42 markers and at most 499 SNP markers. In general, the F_ST statistical method required a smaller number of markers to achieve a successful assignment. G'st and G"st statistics showed poor performance with more than 350 markers to achieve 95% correct assignment. It should be noted that with only the top 60 selected markers, it is possible to achieve a success rate of more than 70%. According to the results, Wright's paired Fst had better performance than other SNP selection methods. The obtained results lead to the creation of exclusive panels to identify various breeds, which have great economic importance.

The objective of this study was to evaluate the effect of feeding two oral Ca boluses at calving and 12 h later on feed intake, milk yield, body weight (BW) changes, blood calcium and some reproductive parameters of high producing dairy cows during summer season. Twenty-four Holstein cows with average parity of 2.8 ± 0.8 were selected and randomly assigned to one of two treatments including control or the group receiving slow-release oral Ca bolus at calving and 12 h post-calving. Row milk yield was greater in cows receiving Ca boluses compared to control treatments during 21 days of lactation (P = 0.02). The milk fat (P = 0.01) and solid non-fat percentage (P = 0.05) were greater in cows that received calcium bolus compared to control treatment. In addition, energy-corrected and fat-corrected milk yields increased in cows received Ca bolus (P = 0.03). Plasma glucose and serum calcium concentration as well as BW change were not affected by experimental treatments. The pregnancy per artificial insemination, days to first insemination and open days were not significantly different between the experimental treatments (P >0.05). The results showed that using oral calcium bolus at calving and 12 hours after calving improved milk production and composition, but had no effect on serum Ca, BW change during first 21 days of lactation, and reproduction parameters.

In order to investigate the effect of licorice extract (LE) on growth performance, fermentation parameters, and rumen protozoan population in fattening lambs, 28 male lambs weighing 36.45 ± 1.75 kg in a completely randomized design with four treatments and seven replicates were used. Experimental treatmeشnts included: control, basic diet without licorice extract, and treatments one to three included basic diet plus five, 10 and 25 mg of LE per kilogram of DM. The ratio of forage to concentrate was 30:70, which was given to the animals as per their appetite. Adding 25 mg of the extract to the diet increased the daily gain and improved the feed conversion ratio (P<0.05). The pH of rumen fluid and gas production increased at the level of 25 mg of extract (P<0.05). Methane production was not affected by adding LE to the diet. The changes in metabolizable energy, degraded organic matter and concentration of volatile fatty acids in diets containing 5 and 25 mg of LE were more than other groups (P<0.05). The total population of protozoa as well as the number of Entodinia decreased by feeding diets containing LE (P<0.05) but the number of Isotrichida increased, significantly. Based on the results of this research, adding 25 mg/kg of licorice extract to the diet improves the rumen metabolism and the performance of fattening lambs, but it had no effect on the amount of energy loss in the form of methane.

In the current study, the effect of source and level of copper in the diet on production and health of dairy cows using 105 multiparous pregnant Holstein cows from -21 until +15 days relative to calving in randomized complete block design with 3 treatments and 35 replications were investigated. The experimental treatments include: 1) diet containing copper at the NRC recommended levels from copper sulfate source (NRC-S), 2) diet containing copper at twice the NRC recommended levels from copper glycinate source (2NRC-Gly) and 3) diet containing copper at twice the NRC recommended levels from copper sulfate source (2NRC-S). Milk yield and composition were not affected by experimental treatments, but treatment by time interaction showed that cows fed by 2NRC-Gly had more milk than NRC-S group (P<0.05) at 60, 90,120 DIM and cow in 2NRC-Gly produced more milk at 90 and 120 days in milk compared to NRC-S (P<0.05). The somatic cells count for 2NRC-Gly cows was lower compared to NRC-S cows (P 0.05). The incidence of subclinical mastitis at 15 DIM in 2NRC-Gly was lower compared to the other two treatments (P = 0.05). No difference in body weight and body condition score changes were observed across treatments. Blood metabolites and liver enzymes were not affected by adding different Cu sources, but serum albumin postpartum was increased in 2NRC-Gly group relative to the other two groups (P 0.05). Based on the results, adding copper especially by copper glycinate source at twice the NRC recommended levels led to an increase in the serum albumin concentration, a decrease in milk somatic cells count and lower incidence of subclinical mastitis, which could indicate an improvement in health of cows during transition period.

The present experiment was performed to study the effect of slow-release urea on performance traits and some blood parameters of replacement ewe lambs during its replacement with cotton seed meal. The livestock included 16 heads of Afshari replacement ewe lambs. Treatments include: Control containing cottonseed meal, treatment 1 contains 4 grams of slow-release urea in the daily diet (equivalent to 4.45% of dietary crude protein), treatment 2 contains 8 grams of slow-release urea in the daily diet (equal to 8.8% of dietary crude protein), treatment 3 contains 12 grams of slow-release urea in the daily diet (equal to 13.3% of dietary crude protein). The experimental duration included two weeks of acclimatization and forty days of fattening. The studied traits included functional traits and blood parameters. Functional traits included final body weight, feed intake, added daily gain and feed conversion ratio. Blood parameters included total serum protein, glucose, urea, AST, ALT, cholesterol, triglycerides, estrogen, albumin and LDL. The results showed that there was no significant difference between the four treatments in blood parameters. There was no significant difference in final body weight, feed intake, added daily gain and feed conversion ratio between the treatments. Based on the results, it is possible to use up to 12 grams of slow-release urea daily in the diet of ewe lambs without a negative effect on performance.

The aim of the present study was to evaluate the effect of fodder beet on performance, carcass traits and blood parameters of fattening male lambs. 32 fattening male lambs with an initial weight of 28.05 ± 0.25 kg by using a completely randomized block design with four treatments and four blocks for 84 days were fed with experimental diets including control (zero), 10, 20 and 30% fodder beet with the ratio 60% of the concentrate and 40% of the fodder as total mixed ration twice a day. During the experiment period, there was no significant difference in the weight of the lambs among the control group and the groups in which different levels of fodder beet were used in their diets. There was no significant difference in average daily gain among all groups except for the lambs fed with 20% fodder beet diet. In the group that received 30% fodder beet, the feed intake (DM/d) was the lowest compared to other groups (P<0.05). No significant difference in the feed conversion ratio among the experimental groups was observed. There was no difference in slaughter weight, empty-body weight, hot and cold carcass weight, carcass traits and carcass dressing percentage of lambs among different groups (P>0.05). The experimental treatments had no effect on the biochemical characteristics of lambs blood, but fodder beet intake increased blood hemoglobin (P<0.05). Based on the results, fodder beet up to 30% could be used in fattening lamb diets without negative effect on performance, carcass characteristics and blood parameters.

The effect of different levels of Oji plant powder on performance, nutrient digestibility, rumination behavior, blood and rumen parameters of Dalagh ewes, using 18 ewes with an average weight of 38±3.5 kg in a completely randomized design with three treatments and six Repetition was investigated. The treatments included 1- control (without Oji powder), 2- 25 gr of Oji powder per day and 3- 50 gr of Oji powder per day. Different levels of Oji powder in ewes had no effect on the weight at the end of the period, daily weight gain, cholesterol, glucose, total protein, albumin, globulin and blood albumin/globulin ratio. Feeding ewes with different levels of Oji powder decreased the apparent digestibility of dry matter, increased nutritional consumption behavior and rumination activity, and increased blood urea and triglyceride levels(P<0.05). Feeding ewes with different levels of Oji powder caused a significant decrease in protozoan population three hours after feeding and an increase in rumen pH three hours after morning feeding(P<0.05). Ruminal ammonia concentration in ewes that received 50 gr of Oji powder per day was higher than other treatments(P<0.05). According to the results of this research, adding the powder of Oji plant up to the level of 50 gr per day to the ration of Dalagh ewes does not have a significant effect on the functional traits of the animal, and it also shows a positive effect on the protozoan population and rumen pH.

The present study was conducted in order to determine yield and the nutritive value of Napier grass at different growth stages as a new forage source in Iran. For this purpose, Napier grass was harvested at three stages of vegetative growth (65, 85 and 115 days after planting, respectively). Chemical composition, rumen fermentation parameters, yield and some morphological traits were investigated. At the final growth stage, dry matter (DM) yield and height of Napier grass was 26.8 tons per hectare and 257 cm, respectively. With increasing age of the plant, a decrease in crude protein and an increase in lignin of cell wall was observed (P < 0.05). Crude protein and neutral detergent fiber content of the grass at this stage were 88 and 63 g/kg DM, respectively. Changes in chemical compositions during growth stages were more pronounced in the stem than in the leaf. During the growth period, the decrease in digestibility of leave and stem led to a decrease in dry matter and organic matter digestibility of Napier grass from 782 to 649 and from 814 to 747 g/kg DM, respectively (P < 0.05). The amount of gas production potential decreased with increasing plant age (P < 0.05). Fermentation rate and lag time were similar in plant harvested at the three stages of growth. The results of the present study showed that Napier grass with high yield of digestible organic matter and high nutritive value can be considered as a valuable source of forage in the country.

This study was conducted to investigate the effects of mixer added fat, crude protein and conditioning temperature on the pellet durability index, and electrical energy consumption during feed production using computational modeling tools. A total of 192 broiler feed samples with different levels of mixer added fat and crude protein in feed components and different conditioning temperatures to determine the pellet durability index, modified pellet durability index and electrical energy consumption during feed production were used. Multiple linear regression and artificial neural network were used to analyze data. Both models had the ability to predict the value of the pellet durability index, modified pellet durability index and the electrical energy consumption during feed production; but the prediction accuracy of the artificial neural network model was higher than that of the multiple linear regression model for all three outputs. Optimization was done using the artificial neural network model, and in these calculations, in order to achieve the highest possible level of pellet physical quality and the lowest possible level of electrical energy consumption, the crude protein amount was 20-20.5% and the conditioning temperature was predicted to be 85 C. However, the amount of fat was predicted to be 1% for the highest amount of pellet physical quality and 4% for the lowest amount of electrical energy consumption during production. In practical conditions, this model can help in more accurate prediction of electricity consumption and the quality of produced feed in order to achieve the optimal situation in feed production factories.

An experiment was conducted to determine the effects of autolyzed yeast with enzyme supplementation and barley particle size on energy and protein efficiency ratio, immune system and ileal digestibility with 400 one-day-old Ross 308 broiler chickens from both sexes in completely randomized design with factorial arrangement 2×4 with 8 treatments, 5 replicates from 1 to 35 days of age. The experimental treatments included type of additive (without additive, enzyme, autolyzed yeast and autolyzed yeast with enzyme) and barley particle size (fine (2 mm) and coarse (8 mm)). Supplementation of autolyzed yeast and enzyme improved FCR compared to the treatment without additives (P>0.05). Autolyzed yeast with coarse barley particles increased the European efficiency factor, energy and protein efficiency ratio compared to other treatments (P>0.05). Supplementation of enzyme led to a decrease in abdominal fat percentage compared to other treatments (P<0.05). Autolyzed yeast with enzyme increased the length and dry matter percentage of the tibia compared to the treatment without additives (P<0.05). Addition of autolyzed yeast with enzyme improved the response immune system compared to other treatments (P<0.05). Supplementation of autolyzed yeast with enzyme improved the ileal digestibility compared to other treatments (P<0.05). Addition autolyzed yeast alone and with enzyme decreased litter pH compared to the treatment receiving enzyme alone and the treatment without additive (P<0.05). As summary, autolyzed yeast with enzyme can be used to improve the performance of broiler chickens fed diets containing barley.