Body Morphometry and Development of the Digestive System of Grey Partridge ( Perdix Perdix ) Depending on Age and Gender

I Professor, Department of Poultry Breeding, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Bydgoszcz, Poland II Doctor of Philosophy, Department of Poultry Breeding, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Bydgoszcz, Poland III Master of Science, Department of Poultry and Animal Production, Faculty of Agriculture, Sohag University, Sohag, Egypt IV Master of Science, Department of Poultry Breeding, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Bydgoszcz, Poland V Master of Science, Division of Animal Product Evaluation, Faculty of Animal Breeding and Biology, UTP University of Science and Technology, Bydgoszcz, Poland


INTRODUCTION
Grey partridge (Perdix perdix L.), also known as the Hungarian Partridge or English Partridge, is a bird in the family Phasianidae.This middle-sized bird has a head-to-tall length of about 30 cm, wingspan about 45 cm and body weight from 290 g to 475 g (Meriggi et al. 2007;Pis, 2012).
The growth traits of young partridges (up to 9 months of age) were investigated, among others, by Kobriger (1980), Liukkonen-Anttila et al. (1999), Pis (2012), Nowaczewski et al. (2014).Kobriger (1980) reported that until 17 weeks of age, grey partridges achieve the highest daily weight gains at 4 weeks (9.6 g/day), and the lowest at 16 weeks of growth (0.1 g/day).In a more recent study (Nowaczewski et al., 2014), the highest weight in grey partridge were recorded between 6 and 9 weeks of age.
The development of grey partridges is also reflected in the weight and dimensions of the internal organs.Putaala & Hissa (1995) showed that compared to wild grey partridges, captive grey partridges were significantly heavier, had shorter small intestines and caeca, as well as lower weight and proportion of the heart, gizzard and liver.

Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender
Grey partridges begun to be bred on farms after the population of this valuable game bird species rapidly declined in Poland and other European countries in the 1970s and 1980s (Panek, 2000).Despite the measures undertaken, the grey partridge population has declined in Poland in recent years, which is very unfavorable.In 2005 there were 347,000 partridges in Poland and in 2015 this number declined to 284,000 (Concise Statistical Yearbook of Poland, 2016).The lack of studies on most of the traits evaluated in this experiment in grey partridges (Perdix perdix) farmed in Poland was the motivation behind the present study.
The aim of the study was to determine the effect of grey partridge age and gender on body weight and dimensions, body conformation indices, length and diameter of intestine and intestinal segments, as well as the weight and proportion in the body of the main internal organs.

MATERIALS AND METHODS
The experiment was carried out at the Department of Poultry Breeding of the UTP University of Science and Technology in Bydgoszcz with approval of the Ethics Committee No. 27/2012.The subjects were 100 grey partridges (Perdix perdix L.).
During the first weeks of life, partridges were kept in an environmentally controlled confinement facility, and later in an outdoor aviary.From 1 to 16 weeks of age, birds were fed ad libitum with complete commercial diets for meat partridges.Partridges received a diet containing 26.0% CP and 12.1 MJ metabolizable energy (ME) until 2 weeks, a diet containing 22.0% CP and 11.9 MJ ME between 3 and 4 weeks, and a diet containing 17% CP and 11.9 MJ ME per kg between 5 and 16 weeks of age.From 17 to 36 weeks, the birds were kept in an aviary (~2.5 m 2 per bird) and fed with wheat grain, rapeseed grain, and coarsely ground maize grain.
At the end of 12 and 36 weeks, 10 males and 10 females (40 birds in total) with body weight similar for a given gender on each evaluation date, were selected for slaughter.Partridges were selected based on conformation and/or plumage traits.After slaughter, plucking and evisceration, the gender of the analyzed partridges was identified again based on the appearance of their reproductive organs.Birds were weighed individually on Precisa 5/12 electronic scales (Medicat) to the nearest 0.1 g, after which they were subjected to body measurements (40 birds).Birds were tape-measured with an accuracy of 1 mm for length of trunk with neck -body length (between the first cervical vertebra and posterior superior tuberosity of the ischium), length of trunk (between tuberosity of shoulder joint and posterior edge of the ischium), chest circumference (behind wings through anterior edge of the keel and middle thoracic vertebra), length of keel (from the anterior to the posterior edge of the keel), length of lower thigh (along the shin bone) and length of shank (between tarsal joint and posterior area of the fourth toe at its base).Body weight and body measurement values were used to calculate the body conformation indices of massiveness (percentage ratio of body weight in kg to trunk length in cm), compactness (percentage ratio of chest circumference to trunk length in cm) and long-leggedness (percentage ratio of shank length to body length in cm) (Kokoszyński et al., 2017).
After the measurements, birds were slaughtered, defeathered and eviscerated, and the digestive tract was separated.The length of small intestine, caeca and rectum was tape measured to the nearest 0.1 cm, and the diameter of these intestinal segments (initial, middle and final parts) was measured with electronic calipers to the nearest 0.001 mm.
In addition, after evisceration, the following parts were separated and weighed on a Medicat 160M scales to the nearest 0.001 g: gizzard (without gastric content), proventriculus (without gastric content), liver (without gallbladder), heart, and spleen.Thereafter, their percentage in preslaughter body weight was determined.
The numerical data were analyzed statistically by calculating arithmetic mean and standard deviation (mean±SD) for the analysed traits using SAS/STAT version 9.4.Significance of differences between the mean values of the age groups was determined using Tukey-test pair-wise comparison test.Differences were considered significant at p<0.05.

RESULTS AND DISCUSSION
At 12 weeks of age, male and female grey partridges had greater body weight compared to 36-week-old birds.With advancing age, the body dimensions increased except for the trunk length.On both evaluation dates, males were heavier and had greater body dimensions than females.Significant differences were only found for keel length in females (Table 1).In young grey partridges, Kobriger (1980) found higher body weight in 12-week-old birds (357 g), and Nowaczewski et al. (2014)  in grey partridges (12-week-old, male 295 g, female 282 g) than in our study.Compared to birds aged 36 weeks, higher body weight of grey partridges (383 g) was reported at 9 months by Putaala & Hissa (1995).The lower body weight of the birds analyzed at the age of 36 weeks was due to the introduction of restricted feeding (wheat grain, maize grain, rapeseed) from 17 weeks of age.This system of feeding is recommended when partridges are planned to be introduced to hunting grounds.Probably, increasing the aviary area to 2.5 m 2 per bird also had an effect on body weight.Liukkonen-Anttila et al. (1999) observed the body weight of grey partridges to decrease after 6 weeks of feeding sprouted (raw, dry) barley, oat grain and weed seeds (natural diet) compared to birds receiving a crumbled or pelleted commercial diet.
Age and gender had no significant effect (p>0.05) on the indices of massiveness, compactness and longleggedness.Older birds showed higher compactness, and lower massiveness and long-leggedness values.Higher values of the indices were calculated for males than females on both evaluation dates (Table 2).Analysis of the data in Table 3 shows that 36-weekold partridges had greater total length of intestine and its segments (small intestine, caeca, and rectum) compared to 12-week-old birds.The intestine to body length ratio was greater in older partridges.Statistically significant effects of age were found for total intestinal length in males and females, small intestine and rectum length in males, and caeca length and intestine to body length ratio in females.In a study by Liukkonen-Anttila et al. (1999), grey partridges at the age of approximately 9 months had shorter small intestine (40.8 cm or 42.6 cm) and caeca (19.1 cm), whereas Putaala & Hissa (1995) reported similar lengths of small intestine (56.6 or 62.1 cm) and caeca (26.2 cm or 30.0 cm) compared to our investigation.Kasperska et al. (2012) found increased lengths of the oesophagus Means of traits in rows within sexes, marked with different letters differ significantly (p<0.05).

Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender
and crop (p<0.05) and rectum as partridges became older and shorter lengths of small intestine and caeca in 52-week-old birds compared to 13-week-old birds.Kokoszyński et al. (2010) noted greater lengths of the small intestine, caeca and rectum in males that received, from 5 to 16 weeks of age, whole wheat grain (30%) and a pelleted diet (70%) compared to birds fed commercial diets alone.However, an inverse pattern was noted in females.
With the advancing age of partridges, the diameter of small intestine and caeca increased in males and females, and the rectum diameter increased in females.Significant differences were found for caeca diameter in females.At the age of 12 weeks, males had greater diameters of caeca and rectum than females, and at 36 weeks males showed smaller diameters of small intestine, caeca, and rectum compared to females (Table 4).At 36 weeks of age, males and females had lighter proventriculus, liver and spleen, and heavier gizzard and heart compared to birds of the same gender aged 12 weeks.Significant differences were observed for the weight of gizzard, proventriculus and spleen in females, and for the weight of gizzard, liver and spleen in males (Table 5).
The proportion of internal organs in the body of partridges changed with age (Table 6).With advancing age, the percentage of gizzard and heart increased, while spleen percentage decreased significantly (p<0.05) in males and females.Older birds were characterized by non-significantly lower proventriculus percentage (males and females), and lower liver percentage (males).In another experiment, Millan et al. (2001), based on analysis of the results of earlier studies, confirmed that farm-reared red-legged partridges (Alectoris rufa) have significantly lower proportions of liver, spleen and pancreas compared to wild partridges.This suggests a significant effect of rearing system (including diet composition) on the development of visceral organs, which was confirmed in our study.Yamak et al. (2016) found significantly (p<0.05)lower heart weight and higher liver weight in partridges (Alectoris chukar) kept in the free-range compared to the barn system between 14 and 18 weeks of age.Compared to females, males were characterized by significantly (p<0.01)higher weight of the heart, liver, gizzard, and edible inner organs.

CONCLUSIONS
In conclusion, the age and gender of birds had no significant effect on body weight and dimensions except for keel length in females.Thirty-six-week-old partridges (fed wheat grain, maize grain and rapeseed from 17 weeks of age) had significantly longer intestine, intestinal segments and the intestine to body length ratio compared to younger birds.Gizzard weight increased significantly with the age of females, and the lower body weight Body Morphometry and Development of the Digestive System of Grey Partridge (Perdix Perdix) Depending on Age and Gender

Table 1 -
Body weight and body dimensions of grey partridges of different ages.

Table 2 -
Body conformation indices of grey partridges of different ages.

Table 3 -
Length of intestine and its segments, and the intestine to body length ratio in grey partridges of different ages. a,b

Table 4 -
Diameter of intestinal segments in grey partridges of different ages.Means of traits in rows within sexes, marked with different letters differ significantly (p<0.05).

Table 5 -
Weight of internal organs in grey partridges of different ages.