J APPL POULT RES 2007. 16:226-233
© 2007 Poultry Science Association
Effect of Gender on Factors Affecting Excreta Dry Matter Content of Broiler Chickens
N. Ziaei*,1,
J. H. Guy*,
S. A. Edwards*,
P. J. Blanchard
,
J. Ward and
D. Feuerstein
* School of Agriculture, Food and Rural Development, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; Frank Wright Ltd, Ashbourne, Derbyshire, DE6 1HA, UK; and BASF AG, E-MEE/AA—Rheincenter, 67056 Ludwigshafen, Germany
Correspondence: 1 Corresponding author: Nemat.Ziaei{at}ncl.ac.uk
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SUMMARY
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The purpose of this experiment was to investigate the factors affecting water intake in modern genetic lines of broilers that might contribute to problems of wet litter. A total of 128 Ross 308 one-day-old chicks (equal numbers of males and females) were fed commercial grower and finisher rations ad libitum from 10 to 39 d of age, containing 0.2% Ti2O3 as an inert marker. Birds were housed in groups of 4 in metabolism cages. Body weight and feed consumption were recorded weekly from d 10, and water intake was recorded daily. Excreta from each cage were collected daily and, at the end of each week, the DM content of a sample of pooled excreta from each cage was measured. The results showed that male broilers consumed more water (P < 0.001) and produced excreta that had a lower mean DM content (P < 0.05) compared with females. Males grew significantly faster (P < 0.05) compared with females. There was a significant correlation between feed intake, and hence the intake of N and the major minerals, and water intake (r = 0.623, P = 0.001). Despite a higher apparent retention of DM, CP, and feed efficiency in favor of males, variation among cages was high, and differences between gender were not statistically significant. Water intake tended to be correlated to mean live weight gain of the cage (r = 0.301, P = 0.06), and when live weight gain was used as a covariate in the analysis, the gender difference in water intake was no longer significant. In conclusion, it appears that the higher water intake and lower excreta DM content for males is related to their higher feed and water intake. Mineral excretion was similar for males and females; however, males retained significantly more P compared with females. Male broilers had greater tibia bone size and strength parameters, which indicate higher bone mineral deposition compared with females.
Key Words: broiler • welfare • excreta dry matter content • gender
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DESCRIPTION OF PROBLEM
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Wet litter is an industry problem for broiler chickens that may lead to disease and increased carcass downgrading [1]. As the moisture content of the litter increases, ammonia production increases, which affects the defenses of the respiratory system and increases the likelihood of airborne Escherichia coli organisms causing airsacculitis and pneumonia [2]. There can also be severe adverse effects on bird welfare if the litter stays wet for too long. Broilers that sit on wet litter are much more prone to developing contact dermatitis, leading to hock burn and, in severe cases, breast blisters, which results in downgrading in the processing plant [2]. Because water intake of the birds contributes to the problem of wet litter, an understanding of the factors affecting water intake in modern genetic lines is needed. Water is not often thought of as a nutrient, but it is vital for both welfare and efficient production. Its functions include regulation of body temperature and nutrient transport, and it is essential to numerous chemical reactions in the body. However, excessive water intake in broiler chickens can result in the production of excreta with low DM content, which can lead to problems of wet litter in commercial floor rearing systems [3].
There are many factors that affect water intake in broilers, such as ambient temperature, feed intake, dietary composition, form of the feed, CP content, mineral metabolism, and genetic factors [4]. In older studies, gender has been shown to have an influence on water intake from immediately after hatching [5], but there are few data on water intake of modern genetic lines. If male broilers drink more water, this may be linked to gender differences in aspects of nutrition and physiology. Protein nutrition will have an effect on water intake and excretion; water retention will depend on protein deposition, whereas excretion of protein, which is excess to the requirements of a bird, will need extra water. Mineral nutrition will also have an effect on water intake and excretion; excretion of excess minerals will require extra water, whereas deposition in the skeleton will reduce mineral excretion. There have also been concerns about the degree of lameness shown among commercial broilers, so differences in inherent bone strength of males and females in modern commercial lines are of interest. The objective of this experiment, therefore, was to quantify the effect of gender in a widely used modern commercial broiler line on water and feed intake, excreta DM content, protein digestibility, tibia bone strength parameters, and utilization of P, Ca, and K.
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MATERIALS AND METHODS
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The experiment was a randomized complete block design and was carried out at Cockle Park Farm, Newcastle University. A total of 128 Ross 308 [6] one-day-old chicks were used in this experiment, with equal numbers of males and females, to give 16 replicate cages of 4 birds for each gender. Replicates were arranged according to the spatial location of each block of 8 cages within the room. Birds were fed typical UK commercial grower and finisher diets ad libitum from 8 to 39 d of age. The diets were wheat-based and contained 0.2% Ti2O3 as an inert marker. The starter and finisher diets, respectively, were composed of 23.01 and 20.50% protein, 12.8 and 13.3 MJ of ME, 0.95 and 0.90% Ca, and 0.72 and 0.72% P.
Management
To allow for some selection after the adaptation period, initially 160 chicks (80 male and 80 female) were reared in single-sex floor pens, bedded with wood shavings, and fed a commercial starter diet (crumb) for 7 d. On d 8, chicks were randomly allocated in same-sex groups of 4 to metabolism cages (floor area of 3,000 cm2) at a space allowance/bird of 750 cm2, which is within industry recommendations for the United Kingdom. Ambient temperature was 29°C on d 1, gradually decreased to 21°C by d 27, and was then maintained at this level until d 39. All cages were inspected at least once a day, and any mortality was recorded. Water and feed were available ad libitum from 2 separate troughs at the front of the cage, each 23 cm wide and providing 5.75 and 11.5 cm per bird, respectively, when in groups of 4 initially or of 2 after group reduction on d 21.
Data Recording
Body weight of individual birds was recorded at weekly intervals from d 10 to 39. Records of weekly feed consumption and daily water intake for each cage were taken during the experiment. Every day, a known volume of water was placed in each water trough, and the volume of water remaining the following morning was measured as refusal. Water intakes were subsequently adjusted according to measured daily evaporative losses from similar troughs at appropriate locations within the building. Excreta from each cage were collected daily and stored in a sealed container in a refrigerator. At the end of each week, the DM content of a mixed sample of excreta from each cage was measured (drying at 104°C for 24 h), and the remainder was stored at –20°C for subsequent chemical analysis. At 21 d of age, 2 birds per cage and at the end of the experiment (d 39), the 2 remaining birds were dispatched by dislocation of the neck and dissected to yield digesta samples and tibia bones. The ileum was located, defined as extending from Meckel’s diverticulum to the ileocecal junction, and the distal 40 mm was tied off and excised. This segment was bisected transversely, and its contents were gently squeezed out into a plastic cup. A digesta sample from the rectum was also obtained to determine the apparent digestibility of CP [7]. Apparent ileal digestibility and total tract (measured in rectal digesta samples) metabolizability coefficients of CP were estimated by using 0.2% Ti2O3 as a marker [8]. The following formula was used to calculate the coefficient, where AD = apparent digestibility and metabolizability of CP:
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Feed conversion ratio (FCR) was calculated for each cage using records of feed intake and weight gain per cage. Levels of Ca and P of both diets and rectal and ileal digesta were determined to allow calculation of digestibility and metabolizability coefficients of these minerals. Mineral and N retentions were calculated by subtracting mineral and N excretion from the intake. Because water content of the body in broilers is 65% [9], retained water was estimated by multiplying BW gain by 0.65. Also, the ratio of water to feed intake per cage (water:feed ratio) was calculated using mean water and feed intake values. Bone strength of individual tibia bones was measured using a 3-point bend test on a texture analyzer [10]. The flexural stiffness (EI) of individual bones was calculated using the formula EI = A x (S3)/48 x C, where A = force at yield (N); S = span (mm); and C = deformation at yield (mm). The maximum and minimum diameter, thickness, top thickness, and bottom thickness for each tibia were measured.
Statistical Analysis
At the end of the experiment, data were analyzed by Minitab 13 [11] using ANOVA to assess the effects of gender and replicate on water intake, feed consumption, excreta DM content, BW gain, protein and mineral digestibility, and bone strength. The statistical model used for the analysis of dependent variables was:
where Yijk = the individual observation; µ = the experimental mean; Gi = the gender effect; Rj = the replicate effect; and eijk = the random error. Correlation values were calculated between various parameters using mean cage data.
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RESULTS AND DISCUSSION
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The effects of gender on water intake, excreta DM content, and rectal and ileal digesta are shown in Table 1
. There was a significant effect of gender on water intake (P < 0.001) and excreta DM content (P < 0.05), with male chicks consuming more water (on average, 11.0 mL more per d) and producing excreta with a lower DM content (on average, 2.2 percentage points) compared with females. There was no significant effect of gender on DM content of ileal or rectal digesta.
In this experiment, water was provided in troughs, whereas in commercial practice, broilers would typically be offered water through nipple drinkers. Reports by Bray and Lynn [12] have shown that the use of small cup or nipple drinkers can decrease water wastage compared with traditional bell drinkers. However, average water intake in the current experiment was within the range of typical water consumption for this genotype [6]. Therefore, although the use of troughs resulted in an increase in water intake compared with nipple drinkers, the results can nevertheless be used as a means of providing further data on water intake differences between genders. These differences are likely to be maintained in a commercial setting using nipple drinkers.
To explore the possibility that differences in water intake between males and females were simply a reflection of a difference in BW, BW was used as a covariate in the ANOVA model to assess the effect of gender on water intake. Using BW as a covariate showed that water intake was not significantly different between males and females. However, differences between genders have been noted in sexually immature birds. Thus, Marks [5] reported that male broilers consumed more water than females and also demonstrated that the divergence in water intake between genders started immediately after hatching. Divergence in BW also begins at this time and is the most likely explanation for observed differences in both feed and water intake between the sexes.
The gender effects on BW, BW gain, retained water, feed consumption, FCR, water:feed ratio, digestibility of DM and CP for rectal and ileal digesta at d 39, and N intake and excretion are presented in Table 2. The effect of gender on BW gain was significant, with females having lower weight gain than males during both grower (P < 0.05) and finisher periods (P < 0.001). The level of retained water in the body for males was, therefore, significantly higher compared with that of the females during both grower (P < 0.05) and finisher (P < 0.001) periods. There were no significant effects of gender on feed consumption or water:feed ratio. However, there was a significant effect (P < 0.05) of gender on FCR, with males having an improved FCR compared with that of females during the finisher and overall period of the experiment (Table 2). There was a significant correlation between feed intake, and hence the intake of N and the major minerals, and water intake (r = 0.623, P = 0.001). Although males had a higher apparent metabolizability of DM and CP in rectal samples compared with females, variation among cages was high, and it was not statistically significant. Gender had no significant effect on ileal digestibility of DM or CP (Table 2). Water intake was significantly correlated to mean live weight gain of the cage (r = 0.444, P = 0.011), and when live weight gain was used as a covariate in the analysis, the gender difference in water intake was no longer significant.
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Table 2. Effect of gender on aspects of growth performance, feed and water intake, digestibility, and N balance (d 39)
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Marks [5] reported that the male:female water intake ratios indicated that males consumed more water than females immediately following hatch and maintained constant rather than increasing ratios over a 12-d period. Data also indicated that both feed intake and feed efficiency are involved in the early BW divergence between males and females. In the present study, the effect of gender on BW gain was also significant (P < 0.001), with females having lower weight gain during the 39-d trial period than males. Recent studies [13, 14] confirm these results, that BW gain of male broilers is significantly higher than that of females and these differences increase with age. It has been reported that BW gain, feed intake, and carcass weight are improved in males compared with female broilers, but females have better feed conversion and livability [15].
In the present study, there were no significant effects of gender on feed consumption or water:feed ratio (Table 2
). However, males had a significantly (P < 0.05) improved FCR compared with that of females. This agrees with Marks [5], who found that feed efficiency and water:feed ratios were higher for males than females, with the magnitude of the difference greater immediately posthatch.
In the current study, there was a significant correlation between apparent digestibility of CP of rectal digesta and rectal DM. Males had a higher N intake and retention (72.3 vs. 69.4%, Table 2) compared with that of females; however, females tended to excrete more N than males, which might have been expected to give wetter excreta. Scott and Hall [16] reported that N retention in male broilers was from 77.6 to 89.9% for wheat-based diets. In the present study, gender had no significant effect on ileal digestibility of CP. Ravindran et al. [17] reported that female broilers tended to have a higher ileal N digestibility than males. The influence of gender of broilers on energy utilization and apparent ileal digestibility of N was also investigated in a study by Ravindran et al. [17], who determined the AMEn using 3- and 6-wk-old broilers, whereas the apparent ileal digestibility was determined only with 6-wk-old birds. Gender of broilers had no effect on the AMEn values determined during wk 3. However, during wk 6, the AMEn values for male broilers were higher than those for the females. Higher N intake and retention for males was associated with higher water intake and retention compared with females, and there was also a significant correlation between N content of the body and water retention [17].
The retention of total P and Ca recorded for males in the current study was 52.9 and 49.6%, respectively (Table 3). These values are in agreement with those previously reported [18], that the retention of total P was 53.3% for the wheat-based diet containing 0.45% available P, and a report [19] that Ca retention was 47.6% for a diet containing 0.93% Ca. Research conducted to determine Ca availability in feedstuffs with broilers has shown that Ca retention follows a pattern similar to P retention [20]. In a study by Ravindran et al. [17], increasing the dietary P level increased ileal P digestibility in both males and females, but the improvements were greater in the females.
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Table 3. Effect of gender on tibia bone strength parameters on d 21 and 39 of mineral intake, excretion, retention, and digestibility at d 39
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The effect of gender on tibia bone strength parameters on d 21 and 39 and mineral intake, excretion, retention, and digestibility values are shown in Table 3.
Tibia from males had significantly greater maximum and minimum diameter, cortical thickness, top thickness, and bottom thickness on d 21 compared with those from females. Similar effects were observed in tibia bones at d 39, with males producing bones with significantly greater maximum and minimum diameter, peak force, and force at yield. The superior bone size and strength parameters of males suggests greater mineral retention in bone, which may explain the higher apparent total tract digestibility of P in males compared with that of females. This is in agreement with Kocamis et al. [21], who stated that males had greater bone length and moment of inertia than females for the tibia and the femur. Although fracture load was significantly affected by gender, when the fracture load was normalized with BW of the animal, treatment and gender effects were significant only for the femur [21]. They also found no significant effect of gender or treatment on stiffness, yield load, yield deflection, and ultimate deflection and elastic, plastic, and total work for the femur or the tibia. The results of the present experiment agree with those of McDonald et al. [22], who found that tibia from male birds had a higher breaking strength than those from females. In the current study, there was no significant effect of gender on mineral intake, excretion, and, therefore, retention, except for males having significantly (P < 0.05) higher P retention compared with that of females, or on the apparent metabolizability of K in rectal samples. Males retained significantly (P < 0.05) more P than females. There was a significant negative correlation between retention of K and excreta DM content (r = – 0.481, P = 0.005).
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CONCLUSIONS AND APPLICATIONS
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- It appears that the higher water intake and lower excreta DM content for males is related to their higher feed intake. Mineral excretion was similar for males and females; however, males retained significantly more P than females. Male broilers had higher tibia bone size and strength parameters, which indicates higher bone mineral deposition in males compared with females.
- The results suggest that to safeguard both welfare and performance of broilers, greater attention should be given to litter quality when male broilers are being grown separately.
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ACKNOWLEDGMENTS
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We thank the Ministry of Science, Research and Technology of Iran for funding the project and also James Wightman and Michael Hearn for their technical support in caring for the birds and assisting with data collection.
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REFERENCES AND NOTES
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- Bailey, M. 1999. The water requirements of poultry. Pages 321–335 in Recent Developments in Poultry Nutrition 2. Nottingham Univ. Press, UK.
- Marks, H. L. 1985. Sexual dimorphism in early feed and water intake of broilers. Poult. Sci. 64:425–428.[ISI][Medline]
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SUMMARY
DESCRIPTION OF PROBLEM
