The aim of this study is to examine the effects of different levels of the feed supplement
In the study, 300 male day-old, Ross 308 broiler chicks were used.
Experiment groups were designed as follows: control; 0.1 %
It was observed that the use of
As a result, the use of yeast as feed supplements in broilers is considered to be an economic and convenient way of providing animal welfare and preventing commercial losses due to leg problems.
A common problem in the broiler chicken industry is leg problems. Excessive breast muscle accumulation combined with an inadequate skeletal development, gender, genetics, feeding, the composition of food, the incubation period, infectious diseases, environmental stress factors, maintenance and management factors affect the frequency and severity of leg problems (Bradshaw et al., 2002; Oviedo-Rondón et al., 2006a, b).
In genetically selected broiler chickens, the disproportionate increase in breast muscle (25–30 % of body weight) compared to other muscle leads to an unbalanced weight distribution on the femur and tibiotarsus physiologically (Havenstein et al., 2003, 2004, 2007; Oviedo-Rondón, 2007); depending on age, chickens become more passive (Kestin et al., 2001). These chickens also shorten the time they are active and consequently they place greater stress on the feet. Therefore, the femur, tibiotarsus and joints of these bones are exposed to more stress in wide breasted broilers than in the traditional line (Abourachid, 1993).
Leg abnormalities cause pain and discomfort for broilers (Danbury et al., 2000; Mcgeown et al., 1999), and severe lameness limits the broilers' access to feeders and water (Weeks et al., 2000; Knowles et al., 2008). Consequently, chickens can be exposed to hunger, thirst, and dehydration (Butterworth et al., 2002). In addition, weight loss and poor-quality products are an economic problem for the poultry industry (Yalcin et al., 1998; Kestin et al., 1999), and leg problems are a serious welfare problem for broiler chickens (European Commission, 2000).
Probiotics are generally used as an alternative additive for competition and
elimination of bacterial pathogens in the poultry industry (Barrow, 1992). As a
probiotic,
Calcitriol increases blood calcium (Ca) levels by promoting the absorption of dietary Ca from the gastrointestinal tract and increases renal tubular reabsorption of Ca, thus reducing the loss of Ca in the urine. Calcitriol also stimulates the release of Ca from bone. The observation that calcitriol stimulates the release of Ca from bone seems contradictory, given that sufficient levels of serum calcitriol generally prevent overall loss of Ca from bone. It is believed that the increased levels of serum Ca resulting from calcitriol-stimulated intestinal uptake causes bone to take up more Ca than it loses by hormonal stimulation of osteoclasts (Voet and Voet, 2004).
The aim of this study is to investigate the effects of different levels of
The experiment was carried out on broiler chicks (
Three hundred 1-day-old male chicks were randomly selected and distributed
into four groups with three replicates of 25-day-old chicks in each.
Thus, 75 chicks were placed in each experimental group. A basal diet was supplemented with
The experimental diets were chemically analyzed according to the methods of
the Association of Official Analytical Chemists (AOAC, 2000). The
metabolizable energy (ME) levels of the diets were estimated using the
equation of Carpenter and Clegg (Leeson and Summers, 2001): ME (kcal kg
The nutrient composition of the experimental diets.
The chicks were housed in an environmentally controlled poultry house with the floor covered with wood shavings and kept dry throughout the study. Feed and water were provided ad libitum. Feeding lasted 42 days. The animals were fed a commercial broiler starter diet (CP Inc. Com, Bursa, Turkey) for the first 20 days, a pelleted grower diet (CP Inc. Com, Bursa, Turkey) from 21 to 35 days of age and a finisher diet (CP Inc. Com, Bursa, Turkey) from 36 to 42 days of age. Ingredient and nutrient compositions of diets are shown in Table 1.
Broiler chickens were slaughtered at the age of 42 days. The left and right legs
were separated from the body at the level of junctura coxae. Soft tissues
around the bones were dissected and removed to obtain the tibiotarsus. After
the removal of the femur and tarsometatarsus, the remaining tibiotarsi were
maintained at
The right tibiotarsi were left at room temperature to defrost, and then the bones were stored at room temperature for 2 weeks until they were dry. After the drying process, the bones were weighed with Precisa XB4200C digital scales (Precisa Instruments Ltd., Switzerland) and the lengths were measured with a Mitutoyo CDN-20C digital caliper (Mitutoyo Corp., Kawasaki, Japan).
For strength evaluation, diaphyseal sections were taken from each
tibiotarsus with a thickness of 1 cm (Yildiz et al., 2009). Bone sections
were numbered and photographed with the help of a Canon EOS 600D camera (Canon Inc., Japan). Photographs were transferred to a computer, and
cortical areas of the diaphysis were measured with the ImageJ Image Processing
and Analysis Program (National Institutes of Health, Bethesda, Maryland,
USA) (Doube et al., 2010). To determine the maximum strength of the
tibiotarsus, a UTEST Model-7014 tension and compression machine (Utest Inc.,
Ankara, Turkey) with a 50 kN load cell were used with the aid of the Maxtest
software. The section of diaphysis was placed between the jaws of the tension
and compression machine. The section was subjected to a force at speed of
10 mm min
Tibiotarsi stored at
For the detection of TD, longitudinal sections were performed on the proximal
epiphysis and metaphysis of tibiotarsi, and the epiphyseal cartilage and
metaphysis were macroscopically examined. The severity of the TD lesion was
evaluated as 0,
Effects of
Different superscripts indicate statistical differences
(
Before performing strength tests, tibiotarsi from the right legs were photographed in lateral and craniocaudal positions and transferred to digital cassettes (Philips, Duodiagnost, the Netherlands) for radiographic evaluations. Cassettes were monitored using a computerized X-ray reading device (FCR CAPSULA XLII, Fujifilm, Japan), and then epiphyseal growth plates (Breugelmans et al., 2007) and deviations were evaluated.
Statistical analyses were performed with IBM SPSS (SPSS, Version 20.0;
Chicago, IL). Data were tested for normal distribution and variance
homogeneity assumptions. All the values were grouped and the means and
standard errors were calculated. Data are stated as mean
There was no statistically significant difference between the C and Y1 groups
and the Y2 and Y4 groups in terms of bone weight (
There was no statistically significant difference between the C and Y2 groups
and the Y1 and Y4 groups in terms of bone strength (
Effects of
Different superscripts indicate statistical differences (
The amount of bone ash was significantly increased in all the experimental
groups (Y1, Y2, Y4) compared to the C group (
At the end of the 42-day breeding period, broiler chickens were found to be
affected by TD by an average of 79.3 %. When the severity of TD cases
(0,
There was no statistical difference between the groups in lateral and caudal
deviation (
Effects of
The mean difference is significant at the 0.05 level.
In the present study, the optimum bone development was observed especially
in the Y2 group (
Plavnik and Scott (1980) reported that a 2.5 and 5 % yeast addition to the diet had definite improvements regarding the leg weakness of broilers. Arican (2012)
reported that yeast culture did not have a statistically significant effect on
bone strength in rabbits, but the group with 2 g kg
Akhavan-Salamat et al. (2011) reported that the yeast addition to the diet increased bone Ca levels in broiler chickens, which increased bone strength. In the present study, the high dose of yeast (Y4) caused a decrease in bone strength while increasing the amount of bone ash and minerals. It is based on the report by Rath et al. (1999) that the bone may become more fragile despite increased mineral content. It may be associated with an inadequate amount of collagen in the bone structure.
Although Ghasemi et al. (2006) and Yildiz et al. (2011) reported that there
is no statistical difference between groups in the amount of tibiotarsus ash
through addition of yeast to broiler chickens, Ghasemi et al. (2006) reported
that broiler chicks fed with yeast-supplemented feed had a marginally higher
tibiotarsus ash content compared to chicks fed without a yeast supplement. In the
present study, it was determined that the amount of bone ash was
significantly increased in all experimental groups (Y1, Y2 and Y4) when
compared to the C group (
Effects of
Akhavan-Salamat et al. (2011) reported that the addition of yeast to the
diet increased bone Ca levels in broiler chickens. Simons et al. (1990)
reported that the yeast was able to produce the phytase enzyme and that this
enzyme was necessary to obtain inorganic P from phytate. Phytase also
releases Ca from the insoluble salts of phytic acid and potentially makes
Ca available for absorption in birds (Qian et al., 1997). Ghasemi et al. (2006)
also observed that a linear increase in yeast in the feed increased Ca
retention. In the present study, there was a significant increase in bone Ca
in the Y4 group compared to the other groups (
Although Thayer and Jackson (1975) reported that the addition of live yeast
culture to the diet of chickens in the developmental period increased P
utilization, in the present study, it is determined that there was only a significant increase in bone P in the Y2 group (
Thorp and Maxwell (1993) reported that TD affects 1–40 % of broiler chickens in commercial establishments, and 20–60 % of these animals show subclinical lesions. Edwards (1989) reported that in experimental studies the incidence of TD could be up to 80–90 %. In the present study, 79.3 % of broiler chickens were observed to be affected by TD in postmortem evaluations made after 42 days of growing period.
It has been reported that calcitriol has the ability to upregulate its own receptor activity, which occurs at the mRNA level, and thus calcitriol can automatically induce its own receptor protein (Costa et al., 1985; Pike, 1991). It is also reported that yeast increases the production of calcitriol receptors (Mcdonnel et al., 1989). In the present study, it was determined that there was no significant difference between the groups in terms of the presence of the TD in the different doses, but, when the percentages of TD severity in the groups were examined numerically, it was observed that the TD severity decreased while the yeast concentration increased. Positive improvements in TD incidence may be associated with increased calcitriol receptor activity by yeast supplementation.
Onwurah et al. (2013) reported that 5 g kg
The epiphyseal growth plate is responsible for the longitudinal development
of the bone, and it is the basis for bone development (Hunziker, 1994; Price
et al., 1994). Kim et al. (2009) and Lee et al. (2011) reported that yeast
hydrolysate increased the proximal epiphyseal length of bone, accelerated its longitudinal extension and stimulated growth hormone secretion in young
rats. There is no study of the effect of the yeast on the epiphyseal growth
plate of broiler chickens. In the present study, the closure rates of
epiphyseal growth plates were statistically different between the C and Y2 groups
(
In conclusion, when
Data are available on request from the corresponding author.
The authors declare that they have no conflict of interest.
This work was supported by Uludag University Scientific Research Project Commission (KUAP (V)-2012/44). Edited by: Manfred Mielenz Reviewed by: two anonymous referees