growth rate

The effect of chick initial body weight and dietary nutrients density on growth performance and immune response were investigated using 360 Ross 308 one-day-old straight run chicks (mixed sex) in a completely randomized design with 2×3 factorial arrangement of treatments, four replicates and 15 birds per replicate. The initial body weight of chicks was grouped as 42±1 g (standard weight); 38±1 g (light weight; 10% under standard weight); 46±1 g (heavy weight; 10% over standard weight) while the nutrients density of the diet was either 5% lower than the nutritional recommendation of Ross 308 (typical commercial diet in Iran), or as recommended by Ross 308 manual (high-density diet). Chickens fed the high-density diet had higher daily weight gain and lower conversion ratio than chickens fed the typical diets (P<0.05). The effect of dietary density and initial body weight of chicks on carcass components and weight of internal organs were not significant except for heart. Broilers fed the high-density diet and heavy weight had higher antibody titers to sheep red blood cell (P<0.05). Light chicks fed the high-density diets had greater total anti sheep red blood cell and immunoglobulin G titers than light chicks fed the typical diets (P<0.05). Results indicate that feeding light chicks with high-density diets increases their growth rate compared to the chicks with standard or heavy weights. Moreover, feeding diets with a high density of nutrients to light chicks can improve immune responses.

This study was performed to investigate the relationship between apparent digestibility of magnesium (Mg) with body weight, feed intake and phytase enzyme with 120 individual B-line Arian male broilers. Birds were assigned two standard diets and a diet supplemented with one gram of phytase (FTU / 500 kg). Daily feed intake, weekly weight gain, feed conversion ratio during rearing and Mg digestibility were measured at 28 to 30 days. Using Gompertz model, growth rate (c), initial weight (b) and maximum growth potential (m) were analyzed. Growth rate and maximum growth potential were higher in the group fed phytase enzyme (P <0.05). Weight gain and feed conversion ratio improved under the effect of phytase supplemented diets (P <0.05). Magnesium digestibility was higher in phytase enzyme diets than standard basal diets (P <0.05). The results showed that the modeled growth rate affected the Mg digestibility, so that birds with higher growth rate (faster growth potential) had more potential for Mg digestion (P<0.05). The relationship between Mg digestibility and body weight gain was positive and with increasing Mg digestion, weight gain improved (P<0.05). Birds with higher growth potential have the ability to digest more Mg, and this digestibility is increased by the use of the phytase enzyme. Therefore, in the breeding programs of Arian chickens, more attention can be paid to the relationship between the use of Mg and the growth rate parameter.

Growth, defined as changes of body weight over time, is an economically important trait in sheep that directly determines meat production.Increase in live weight or dimension against age has been described as growth. Changes in live weight or dimension for a period of time are explained by the growth curves. Animal breeders are interested in the genotypic and phenotypic relationships during all phases of growth. Knowledge of genotypic and phenotypic relationships among live weights, degree of maturity and growth rate during all phases of growth is necessary to formulate breeding programs to improve lifetime efficiency.  Growth models are mathematical functions which are applied for describing the growth pattern. Understanding, estimating, and capturing the defining characteristics of growth processes are key components of developmental research. The aim of the present study was to estimate the genetic parameters for growth traits in Zandi sheep, by determining the most appropriate animal models to be fitted. In addition, genetic, phenotypic and environmental correlations between traits were estimated.

The data used in this study were obtained from the Animal Breeding Center of Iran. The data were screened several times to remove the defective and out of range records. Growth curve parameters used in study were asymptomatic mature weight (A), Growth rate (B) and maturity rate (K). The procedure of SAS software was used for studying of fix effects. Based on body weight at different ages and using different initial values, each of the growth curve parameters was estimated using SAS software version 9.1 and NLIN procedure. Estimation of (co)variance components of growth curve parameters was conducted using Bayesian approach implemented in MTGSAM and Wombat software. The number of Gibbs sampling rounds used was 200,000 rounds.  Ten percent of these numbers (20,000 rounds) was burn-in. The convergence criterion for stopping repetitions in this analysis was also considered as 10 decimals (10-10). Sampling intervals of 200 and Gouss- Seidel 10000 repetitions were considered. In order to find the best model incorporating the constant and random effects affecting each of the parameters of the growth pattern, the following models, with and without regard to maternal effects including maternal additive genetic effects and permanent maternal environmental effects in the model (Meyer’s models) were tested.

 Environmental factors such as year of birth and sex of lamb showed significant influence on growth curve parameters (A, B and k) in Zandi sheep. Estimates of direct heritability is based on best models using REML and Bayesian methods for A, B and K were 0.064 and 0.14, 0.17and 0.16, 0.16and 0.18 respectively. Maternal heritability was in range of 0.006 - 0.08 and Proportion of environmental variance to phenotypic variance in range of 0.03 - 0.05 parameters growth curve. Among the growth curve parameters, only A and k have biological interpretation and therefore, relationship between them may provide necessary conclusions. Estimates of direct genetic correlation between growth curve parameters were 0.323, -0.429 and 0.803 between A-B, A-K and B-K, respectively. The positive and high genetic correlation between A and B parameters is evident as expected for common genetic and physiological mechanisms controlling these traits. Positive genetic correlation between these traits suggests that selection in one parameter of the growth curve would also improve the other parameter. Residual correlations between growth curve parameters varied form −0.296 (between A-K) to 0.732 (between B-K). Phenotypic correlations between growth curve parameters varied form −0.184 (between A-K) to 0.743 (between B-K). The phenotypic and genetic antagonism between A and k indicates that rapid reduction in growth rate after inflexion point results in lower mature weights. This finding would be helpful for improving selection by identifying the animal who reaches inflexion point earlier and attend higher mature weights later.

 Current genetic estimates for growth curve parameters in Zandi sheep could be applied in designing selection program in this breed. The low estimates of heritability for A, B and K parameters could be assigned to the high phenotypic variance arising from large environmental variation. This therefore implies that much of the improvement in these growth curve parameters could be obtained by improvement of environment rather than genetic selection. It is important to provide good environmental conditions along with optimal management strategies in the flock to achieve a desired shape of growth curve through changing the parameters of model.

The purpose of the present study was to estimation of (co)variance components and genetic parameters of the growth curve in crossbred population. For this purpose, body weight records were fitted through the Gompertz curve and curve parameters were estimated. The final weight (Wf), hatch weight (W0), mature rate index (K), age (ti) and weight (Wi) in inflection point and growth rate in different days for all of the birds were predicted by Gompertz model. The estimated of (co)variance and genetic parameters were performed using a multi-trait animal model through Gibbs sampling. Heritability of the growth cure parameters including final weight, hatch weight, mature index and weight and age in inflection point was 0.335, 0.269, 0.273, 0.291 and 0.397, respectively. Also, the heritability of growth rate traits from hatch to 45 days was estimated high and varied between 0.311 to 0.424. The genetic correlation between hatch weight with mature index and final weight was positive (0.14 and 0.24), but the genetic correlation between hatch weight with age and weight at inflection point was negative (-0.24 and -0.12). The genetic correlation of the mature index with hatch weight, mature weight, age and weight at inflection point was negative. Genetic correlation of the mature index with growth rate in the early ages of bird was positive and it was estimated medium and negative for late. The weight at inflection point had the positive genetic correlation with most of growth rate traits and the change trend from beginning to end of growth period was ascending.

Livestock husbandry in dry areas is facing scarcity and fluctuation of feed supply specially during dry seasons. At the same time use of halophytic plants such as Alhagi spp. could supply small ruminant requirements. The study was conducted to determine the effect of feeding diets containing Alhagi on the milk yield of Baloochi ewes and body weight gain of their lambs. Seventy-two adult Baloochi ewes (43.5±3.5 kg) in late gestation were randomly selected and distributed into three equal groups, 24 animals each. The selected ewes were fed with the dietary treatments for 2 month before the lambing date and continued until 60 days. The treatments include: 1) Alhagi 0%, wheat straw 65%, barley grain 20%; 2) Alhagi 40%, wheat straw 25%, barley grain 20%; 3) Alhagi 80%, barley grain 20%. Increasing Alhagi replacement in diet led to raise in lignin-cellulose materials. The dietary treatments had a significant effect on overall DMI of ewes (P<0.05). The ewes receiving diets without Alhagi (1338.25 gr) and containing 80% Alhagi (1323.50gr) had increased feed intake significantly (P<0.05) compared with animals fed with Alhagi 40 percent (1068.25gr). Also treatments had a significant effect (P<0.05) on DMI of ewes during the different physiological stages: late gestation and lactating. The ewes fed with Alhagi 80% showed higher milk production than those fed with 40% Alhaji foliage in diet. Means of daily milk production were 574.42, 499.01 and 642.99 g per ewe for the diets containing 0, 40 and 80 % Alhaji, respectively. The milk fat percent related to diet 0% Alhagi was higher than diet containing 80% Alhagi significantly (P<0.05) and milk protein percent was highest (P<0.05) for ewes fed with 0% Alhagi. Diets had no significant effect on milk lactose, SNF and TS percents. The treatments had no significant effect on birth weight. The highest weaning weight and growth rate of lambs was for ewes received diet 0% Alhagi and the lowest was for ewes fed diet 40% Alhagi (P<0.01). Feeding Alhagi browse with energy supplement to lactating Baloochi ewes did not present any significant problems on milk yield or growth rate of lambs and substituting Alhagi browse for cereal straw or alfalfa in diets of sheep and will reduce the cost of roughage component and also it will supply nutritive during periods with forage scarcity.

This experiment was conducted to investigate the effect of diet and fattening start weight on body growth in the different stages of the fattening periods and carcass compositions of Moghani male lambs. For this purpose, 36 heads of Moghani male lambs with three weights classes (Light, medium and heavy weight) were used with two diets (alfalfa to concentrate ratio of 70 to 30 (diet 1) and 30 to 70 (diet 2)) were fattening up to the time which their weights were 55 kg. The lambs were placed in individual cages for control the amount of feed daily intake and residual collected. The diets of high concentrate compared with diet of high forage were more favorable effect on body weight during the fattening at all stages and also daily weight gain (P<0.05). The significant difference was between heavy weight lambs (112 g/day) with light weight lambs (153 g/day) on daily weight gain (P<0.05). The diet had significant effect on carcass efficiency, hot and cold carcass weight, fat-tail weight and liver weight (P<0.05) and also percentage of fat-tail weight to carcass weight ratio (P<0.05). Negative correlation existed between fat-tail weight with different component of the carcass, especially with its valuable parts (leg, sirloin, breast and shoulder). Generally, high concentrate intake caused increase of fat-tail stores. Fattening with low weight increased daily weight gain, but in higher age was associated with fat stores in Moghani male lambs.

20 one-month-old Sanjabi suckling lambs (ten males and ten females with initial liveweight of 13.4 ± 1.3 and 11.6 ± 0.9, respectively) were used to assess the effect of ad libitum creep mixture on dry mater intake, live weight gain and carcass characteristics. The lambs were blocked within sex according to their live weight and randomly allocated to one of two treatments, control (free suckling and free choice of alfalfa) or supplementary (ad libitum creep mixtures with free suckling and free choice of alfalfa) in a 2 × 2 factorial arrangement. The study was continued for 100 days and at the end of the experimental period, all lambs were slaughtered to assess carcass characteristics. Average daily milk intake of males was higher than females (P< 0.01). Daily live weight gain (g/d) was significantly (P< 0.01) higher in males than females (240 vs. 163 g/d) and in the supplementary group than the control (259 vs. 145 g/d). Fat tissue in both male and female lambs in supplementary group was significantly (P< 0.01) more than that in the control. It could be concluded that the creep mixture diet improved growth rate and carcass characteristics and the fat content of the lambs.

Consuming toxins produced by algal species in running waters and freshwater bodies can have deleterious effects on fish and other aquatic organisms. These toxins are produced by harmful algal blooms (HAB) of cyanobacteria in water. These blooms can be caused by several factors including light, temperature, carbon dioxide, phosphorous and nitrogen. The effects of different concentrations of phosphorous on stimulating and inhibiting growth in cyanobacterial species Jaaginema sp. was studied in this paper. Pure cultures of Jaaginemasp. were cultured in two culture media (Z8 and BG11) using two different concentrations of phosphorous. Four replicates were run for each experimental group and one control group with normal concentration of phosphorous was also studied. Water temperature was 25 ± 1 °C and light intensity was 2200 lux. Observations were made once every 48 h. This species appeared yellow in the BG11 medium and green in the Z8 medium. Counting were made using a hemocytometer and the microscopic observations were made under a light microscope. Results obtained were analyzed using computer based software like SPSS and Excel. Growth rates in the cyanobacterium species were significantly higher in the treatment with phosphorous concentrations of two times the original concentration. Higher concentrations of phosphorous resulted in inhibiting growth in this species. It is evident from the results obtained that phosphorous can be considered a growth inhibiting factor for cyanobacteria and thus influence the occurrence of blooms and release of toxins into water bodies.