For Review Only - University of Toronto T-Space · For Review Only 3 weight gain (Abudabos et al. 2013) and also has a negative effect on bird´s welfare (Meluzzi and Sirri 2009)

For Review O

nly

Effect of litter material and stocking density on bone and

tendon strength, and productive performance in broilers

Journal: Canadian Journal of Animal Science

Manuscript ID CJAS-2016-0246.R2

Manuscript Type: Article

Date Submitted by the Author: 11-May-2017

Complete List of Authors: Vargas-Galicia, Artemio; Colegio de Postgraduados, Husbandry Sosa-Montes, Eliseo; Universidad Autonoma Chapingo, Departamento de Enseñanza e Investigación en Zootecnia Rodríguez-Ortega, Leodan; Colegio de Postgraduados, Husbrandry Pro-Martinez, Arturo; Colegio de Postgraduados, Husbandry Ruiz-Feria, Ciro; Colegio de Postgraduados, Husbandry González-Cerón, Fernando; Universidad Autonoma de Chapingo Departamento de Ensenanza e Investigacion en Zootecnia Gallegos-Sánchez, Jaime; Colegio de Postgraduados, Husbandry Arreola-Enríquez, Jesús; Colegio de Postgraduados, Campus Campeche Bautista-Ortega, Jaime; Colegio de Postgraduados, Campus Campeche

Keywords: tezontle, tibia, tendon, Stocking density, productive performance

https://mc.manuscriptcentral.com/cjas-pubs

Canadian Journal of Animal Science

For Review O

nly

1

Effect of litter material and stocking density on bone and tendon strength, and productive

performance in broilers

Short title: Vargas-Galicia et al.- Litter material and stocking density

Artemio J. Vargas-Galicia1, Eliseo Sosa-Montes2, Leodan T. Rodríguez-Ortega1, Arturo Pro-Martinez1, Ciro A. Ruiz-Feria1, Fernando González-Cerón2, Jaime Gallegos-Sánchez1, Jesús

Arreola-Enríquez3 and Jaime Bautista-Ortega3.

1Colegio de Postgraduados, Campus Montecillo, Texcoco, Mexico State, Mex., 56230; 2Universidad Autónoma Chapingo, Chapingo, Mexico State, Mex., 56230; 3Colegio de Postgraduados, Campus Campeche, Champoton, Mex., 24450.

ABSTRACT

Litter material and stocking density were evaluated on welfare-related variables and productive

performance in broilers. Male chicks (n = 744, “Ross 308” strain) were raised on either tezontle

(TEZ) or wood shavings (WS) litter, with a stocking density of either 13 (LDe) or 18 (HDe)

birds m-2. Twenty-four birds per treatment were randomly selected to assess: tibia (TiBS) and

tendon breaking strength (TeBS) at d 45, and foot pad lesions (FPL) and valgus/varus angulation

(VAng) at d 25, 32 and 39 of age. The TiBS was higher in birds housed at LDe than in those

housed at HDe. Chickens on WS litter showed higher TeBS than those on TEZ litter. Birds in the

TEZ-LDe group had lower values of FPL and VAng at d 32 than birds in the other groups. Birds

in the WS-LDe group had less VAng at d 25 and 39 than birds in the other groups. Productive

performance was higher (P < 0.05) in birds housed at LDe than in those housed at HDe. In

conclusion, tezontle along with low stocking density reduced foot pad lesions, however, tezontle

negatively affected tendon breaking strength, whereas wood shavings litter improved tendon

breaking strength and valgus/varus angulation.

Key Words: tezontle, tibia, tendon, stocking density, productive performance.

Page 1 of 30



For Review O

nly

2

Effet du matériel de litière et densité de population sur la résistance des os et des tendons,

et performance productive dans les poulets de chair

RÉSUMÉ

Le matériel de litière et la densité de la population ont été évalués sur les variables liées au bien-

être et la performance productive dans les poulets de chair. Les poussins mâles (n = 744, souche

"Ross 308") ont été élevés sur une litière de Tezontle (TEZ) ou des copeaux de bois (WS), avec

une densité de population de 13 (LDe) ou 18 (HDe) oiseaux m-2. Vingt-quatre oiseaux par

traitement ont été choisis au hasard pour évaluer: le tibia (TiBS) et la force de rupture du tendon

(TeBS) à 45 j et les lésions des plantaires de pied (FPL) et l'angulation de valgus/varus (VAng) à

j 25, 32 et 39 de l'âge. Le TiBS était plus élevé chez les oiseaux hébergés chez LDe que chez

ceux hébergés chez HDe. Les poulets sur la litière WS ont montré des TeBS supérieurs à ceux de

la litière TEZ. Les oiseaux du groupe TEZ-LDe avaient des valeurs inférieures de FPL et VAng

à j 32 que les oiseaux dans les autres groupes. Les oiseaux du groupe WS-LDe avaient moins

VAng à j 25 et 39 que les oiseaux dans les autres groupes. La performance productive était plus

élevée (P<0,05) chez les oiseaux hébergés chez LDe que chez ceux hébergés chez HDe. En

conclusion, le tezontle avec une faible densité de la population a réduit les lésions des plantaires

de pied, cependant, le tezontle a affecté négativement la résistance à la rupture du tendon, alors

que la litière de copeaux de bois a amélioré la force de rupture du tendon et l'angulation de

valgus / varus.

Mots clés: tezontle, tibia, tendon, densité de la population, performance productive.

INTRODUCTION

One objective of the poultry industry is to maximize the amount of meat produced per square

metre of broiler house. However, increasing stocking density reduces feed intake and body

Page 2 of 30



For Review O

nly

3

weight gain (Abudabos et al. 2013) and also has a negative effect on bird´s welfare (Meluzzi and

Sirri 2009). High stocking density affects the broiler locomotion ability through a higher severity

of skeletal problems and a progressive decrease in walking ability (Mench 2004). High stocking

density reduces the breaking force of tibia (Škrbić et al. 2009) and tendon (Benevides et al.

2004). These problems have been related to 1) lack of physical activity due to reduced space at

high stocking densities and 2) unsynchronized development of muscular mass and skeletal

system (Škrbić et al. 2009). In this regard, Sorensen et al. (2000) reported that low stocking

density reduces the prevalence of leg weakness. High stocking density and age of birds are

associated with the incidence of foot pad lesions (Dawkins et al. 2004; Bessei 2006). Also, litter

with high moisture content exacerbates the incidence of foot pad lesions (Meluzzi et al. 2008;

Almeida-Paz et al. 2010). The type of litter material used by the poultry industry varies among

different regions due to availability and cost (Berg 2004). Tezontle is a material widely used as

substrate in the production of vegetables in Mexico. Tezontle is a porous igneous rock with good

aeration properties and is a non-toxic material that could be used as an alternative litter substrate

(Trejo-Téllez et al. 2013). Murillo et al. (1967) showed that tezontle retains less moisture as

compared to other materials used as litter material for broilers. We hypothesized that the

combination of tezontle as litter material and a low stocking density (13 birds m-2, 30.0 kg BW

m-2 of floor space) would improve the tibia and tendon strength, and the overall wellbeing of

broiler chickens, without compromising the productive performance and carcass yield. Because

tezontle is a material that retains little moisture, it would reduce damage associated with leg

problems. Thus, the objective of this study was to evaluate the effects of litter material and

stocking density, and its interaction, on tibia and tendon breaking strength, bone ash, Ca and P

content, welfare variables (latency to lie down, gait score or walking ability, foot pad lesions and

Page 3 of 30



For Review O

nly

4

valgus/varus angulation), productive performance and carcass yield in broilers. Litter moisture

was also evaluated because of its role in the incidence of leg problems in broilers.

MATERIALS AND METHODS

This study was conducted at the experimental broiler house at Colegio de Postgraduados,

Campus Montecillo, Mexico State, Mexico, located at an altitude of 2278 m (Vázquez-García

and Pérez-Padilla, 2000). Seven hundred and forty-four 1-d-old male broiler chicks (Ross 308)

were raised either on tezontle (TEZ, volcanic rock) or wood shavings (WS) litter, with a stocking

density of either 13 (LDe; 39 birds per pen) or 18 birds m-2 (HDe; 54 birds per pen),

corresponding to 30.0 or 42.0 kg BW m-2 of floor space, based on a predicted final BW of 2.2 kg,

according to the following equation: birds per pen = final stocking density (kg of BW m-2) × pen

area (m2) / predicted final BW (kg). The pen area was 2.79 m2 (excluding feeder and drinker

space). Four replicates per treatment were used. The feeding program was divided in three

phases: starting diet (1-21 d) containing: 3025 kcal of metabolizable energy (ME) kg-1, 22%

crude protein (CP), 1.05% Ca and 0.50% available P; growing diet (22-35 d) containing: 3150

kcal ME kg-1, 21% CP, 0.90% Ca and 0.45% available P; and a finishing diet (36-45 d)

containing: 3200 kcal ME kg-1, 19% CP, 0.85% Ca and 0.42% available P. Diets were

formulated to meet or exceed the nutritional recommendations of the Ross 308 broiler line

(Aviagen 2009). A 23 h light, 1 h dark (23L:1D) schedule was used until d 14. From d 15 to the

end the trial a 12L:12D lighting program was used. All birds received water ad libitum and feed

was restricted by 12 h d-1 (2000 to 0800 h) from the third week onwards, to prevent the ascites

syndrome. Bell drinkers (111 cm in circumference; 2.8 and 2.0 cm per bird for LDe and HDe,

respectively) and hanging feeders (121 cm in circumference; 6.2 and 4.5 cm per bird for LDe and

HDe, respectively) were used. The available feeding and drinking space per bird between LDe

Page 4 of 30



For Review O

nly

5

and HDe groups was different; however, it was enough to allow the access of the birds, and was

maintained during the entire experimental period.

At the beginning of the experiment, room temperature was maintained at 33°C and then it was

reduced 2°C wk-1 until 21°C at 45 d of age. Chickens were housed under a natural ventilation

system during the last three weeks of the experiment. The particle size of tezontle ranged from 2

to 5 mm and that of wood shavings was 20 mm. Both types of litter had a thickness of 3 cm. This

study was conducted according to the Guide for Care and Use of Experimental Animals

approved by the General Academic Council of the Colegio de Postgraduados.

Tibia breaking strength (TiBS), Calcium (Ca), Phosphorus (P) and Ash contents

Twenty-four birds per treatment (6 birds per replicate) were randomly selected and humanely

killed with an electric stunning knife (model VS-200, input power 120 V-1 A, output power 50

V-0.1 A, Midwest Processing Systems, Minneapolis, MN, USA) at d 45 according to the

Mexican Official Norm (NOM-033-SAG/ZOO-2014) to assess slaughter weight, carcass yield

and non-deboned drumsticks weight, and tibia and tendon breaking strength. Right tibias were

collected and subjected to breaking strength tests using a Vernier Force Plate (Vernier Software

& Technology, Beaverton, USA). Tibia was placed on an adjustable three-point loading system,

with a distance between bone supports of 60 mm, and a vertical force was applied at the

midpoint by a 2.54 cm fulcrum. The breaking force was reported in newtons (N). Ash, Ca and P

contents of bone were determined according to the methodology described by the Association of

Official Analytical Chemists (AOAC 1990).

Tendon breaking strength (TeBS)

Calcaneus tendons were carefully dissected from the left leg at d 45 (6 birds per replicate), the

proximal and distal portions of each tendon were submerged in liquid nitrogen, fastened with

Page 5 of 30



For Review O

nly

6

sandpaper and attached to the mounting brackets of the Vernier Force Plate. The breaking

strength was recorded as the force in N required to break the tendon.

Latency to lie down (LTL)

Twenty-four birds per treatment were randomly selected to assess latency to lie down, gait score,

foot pad lesions, and valgus/varus angulation at 25, 32 and 39 d of age.

Birds were subjected to the LTL test, as described by Berg and Sanotra (2003). This test is based

on the fact that bodily contact with water is a novel and aversive experience for broilers. Birds

were tested individually, without visual contact with other birds (24 birds per treatment). Each

bird was placed into a plastic container, previously filled with 3 cm of water at 32°C. The time

until each bird sits down was recorded, according to the principle that the better leg health a bird

has, the longer it will stand up to avoid body contact with the water. If the bird was still standing

after 600 s, the test was interrupted.

Gait score (GS) or walking ability

Gait score was evaluated according to the methodology described by Kestin et al. (1992) and

later modified by Garner et al. (2002). Two observers, simultaneously and individually, scored

each bird; if the evaluators did not reach consensus, they had to reevaluate the bird. Six score

categories were used: 0, a bird with a fluid locomotion and a furled paw when it is raised; 1, the

bird is unsteady, or wobbles when it walks; 2, the leg producing the gait defect can be identified

within 20 s of observation; 3, although the bird will move away from the observer when

approached, it will not run, and squats within 15 s or less; 4, the bird remains squatting when

approached, nudged or touched for 5 s and; 5, a bird in complete lameness that cannot walk or

stand.

Foot pad lesions (FPL)

Page 6 of 30



For Review O

nly

7

Twenty-four birds per treatment were selected to assess foot pad lesions according to the

methodology described by Su et al. (1999). It is based on a combined score for both paws from 0

to 3, in which: 0, no sign of damage; 1, small scab < 5% pad area; 2, large scab < 25% pad area

and; 3, severe burn, large scab-filled ulcers, > 25% pad area and inflammation.

Valgus/varus angulation (VAng)

Valgus/varus angulation was evaluated according to the methodology described by Leterrier and

Nys (1992). Depending on the angle size of tibia-metatarsus, 4 scores were defined: 0, normal

chicken; 1, chicken with little angulation (tibia-metatarsus angle between 10 and 25°); 2, bird

with obvious angulation (angle between 25 and 45°) and; 3, severe angulation (angle greater than

45°).

Litter moisture

At d 25, 32 and 39 samples from 6 different sites (full depth of litter at the 4 corners and 2

central samples, excluding the litter near the drinker) were collected and homogeinized to make a

pooled sample per each pen. Litter dry matter was measured in duplicate 100 g sub-samples of

each pooled sample according to AOAC (1990) methods.

Productive performance and Carcass yield

Feed consumption, body weight gain and feed conversion were recorded weekly from d 1 until d

42. Twenty-four birds per treatment were randomly selected to assess slaughter weight, carcass

yield and non-deboned drumsticks weight at d 45. Feed, but not water, was withdrawn 8 h before

slaughter. Birds were not transported because they were killed at the same research facility.

Broilers were slaughtered by hand cutting the carotid artery and jugular veins of the neck after

5 s of electrical stunning (model VS-200, input power 120 V-1 A, output power 50 V-0.1 A,

Midwest Processing Systems, Minneapolis, MN, USA).

Page 7 of 30



For Review O

nly

8

Statistical analyses

Data of TiBS, TeBS, ash, Ca, P, slaughter weight, non-deboned drumsticks weight and carcass

yield were analyzed under a completely randomized experimental design in a 2 × 2 factorial

arrangement (litter material and stocking density) using the MIXED procedure of SAS (SAS

Institute Inc. 2011). Data of FPL, GS and VAng variables were analyzed with a completely

randomized factorial 2 × 2 × 3 (litter material, stocking density and age) arrangement using the

GLIMMIX and the PROC FREC procedures of SAS for non-parametric data. LTL was analyzed

as a 2 × 2 × 3 factorial arrangement (litter material, stocking density and age) using the MIXED

procedure. For statistical analysis of TiBS, TeBS, ash, Ca, P, slaughter weight, carcass yield,

non-deboned drumsticks weight, LTL, GS, FPL and VAng, subsamples were randomly chosen

from each pen (6 chickens), and each chicken was considered as the observational unit. Litter

moisture, feed intake, body weight gain and feed conversion were analyzed as repeated measures

using the MIXED procedure of SAS; pen was considered the experimental unit. Statistical

difference was set at P < 0.05, and means were separated using the Tukey test. For continuous

variables, the results are presented as mean ± standard error and categorical data are expressed as

frecuencies.

RESULTS

Tibia breaking strength (TiBS)

The TiBS was not affected by litter material (P > 0.05). However, birds raised at LDe showed

significantly higher (P < 0.05) TiBS than those housed at HDe (Figure 1). No interaction

between litter material × stocking density was found (P > 0.05).

Tendon breaking strength (TeBS)

Page 8 of 30



For Review O

nly

9

Litter material × stocking density interaction was not statistically significant and TeBS was not

affected by stocking density (P > 0.05). However, chickens raised on WS litter showed

significantly (P < 0.05) higher TeBS than birds raised on TEZ litter (Figure 2).

Ca, P and Ash contents

Neither main effects nor interactions were significant (P > 0.05) for Ca, P or ash contents (Figure

3).

Latency to lie down (LTL)

Latency to lie down was affected by neither litter material nor stocking density (P > 0.05).

However, LTL was negatively affected by age (P ˂ 0.05); 39 d-old birds took significantly (P ˂

0.05) less time to lie down than 25 and 32 d-old birds (Figure 4). The interaction effects were not

significant (P > 0.05).

Gait score (GS) or walking ability

Gait score was not affected by litter material or stocking density (P > 0.05). Walking ability

decreased significantly with age (P ˂ 0.001). Chickens with scores 4 or 5 were not observed in

this experiment (Table 1). No interactions were found on GS (P > 0.05).

Foot pad lesions (FPL)

The FPL variable was not affected by stocking density or litter material. However, age (P <

0.001) and the litter material × stocking density × age interaction was significant (P < 0.003,

Table 2). At d 25, the TEZ-LDe group had a higher proportion of healthy birds (0 score)

compared with the other treatment groups.

Valgus/varus angulation (VAng)

There was not effect of litter material, stocking density or age on VAng (Table 3), but the

interaction litter material × stocking density × age was significant (P < 0.05). Birds in the WS-

Page 9 of 30



For Review O

nly

10

LDe group had less damage at d 25 and d 39 than birds from the other groups. At d 32 the birds

from the TEZ-LDe group had less angulation than birds in the other treatment groups (Table 3).

Litter moisture

The tezontle litter had lower moisture content (P < 0.05) than WS litter in the three days of

sampling (d 25, 32 and 39). Likewise, lower moisture content (P < 0.05) was observed in the

litters with LDe than in those with HDe at d 25 and 32 (Table 4). Litter material × stocking

density interaction was not significant (P > 0.05).

Productive performance and Carcass yield

Feed intake and body weight gain were higher (P < 0.05) in birds raised at LDe than in birds

raised at HDe, except for week 1 when there were not significant differences. No differences

were observed (P > 0.05) for feed conversion during the experimental period (Table 5).

Cumulative feed intake and body weight gain were higher (P < 0.05) in birds at LDe than in

birds raised at HDe. Cumulative feed conversion was not different between LDe-birds and HDe-

birds (Table 6). Slaughter weight was higher (P < 0.05) in birds raised at LDe than in birds raised

at HDe; similarly, carcass weight was higher (P < 0.05) in birds raised at LDe than in birds

raised at HDe (Table 7). No significant difference was observed on non-deboned drumsticks

weight between stocking densities. Litter material did not affect the productive performance or

the carcass yield. No interactions were detected on productive performance or carcass yield

variables (Table 7).

DISCUSSION

It has been reported that high stocking density reduces bird´s welfare (Meluzzi and Sirri 2009)

and increases litter moisture, which in turn causes a high incidence of foot pad lesions (Dozier et

al. 2006) and reduces walking ability (Venalainen et al. 2006). We hypothesized that the use of

Page 10 of 30



For Review O

nly

11

tezontle as litter material in combination with a low stocking density (13 birds m-2, 30.0 kg BW

m-2 of floor space) would improve tibia and tendon integrity as well as the overall wellbeing of

the chickens without compromising productive performance and carcass yield. In this study,

chickens raised at LDe had higher TiBS than those raised at HDe. Škrbić et al. (2009) reported

that the TiBS was higher in broilers raised at low stocking density (12 birds m-2) than in birds

raised at a high stocking density (16 birds m-2). Likewise, Buijs et al. (2012) mentioned that an

increase in stocking density decreased shear strength of the tibia. Our results could be due to

wider spaces for physical activity when broilers are reared at a low stocking density, which

favors tibia strength (Bradshaw et al. 2002). The bone ash, Ca and P were not affected by litter

material or stocking density. Tablante et al. (2003) also reported that bone ash content of birds

was not affected by stocking densities of 10, 15 or 20 birds m-2 at 45 d of age. Baitshotlhi et al.

(2014) reported that stocking densities of 10, 13, 16, and 19 birds m-2 (0 to 6 weeks of age) had

no significant effect on ash, Ca and P contents of bone.

Chickens raised on WS litter had stronger tendons than chickens raised on TEZ litter. These

results show that litter material may adversely affect tendon integrity, and this can be due to leg

instability of birds raised on TEZ litter. It is also probable that chickens reared on WS litter had

higher physical activity than chickens reared on TEZ litter, which detrimentally affect tendon

strength due to stress imposed by particle size of TEZ that may be result in lameness. Nakagaki

et al. (2007) reported that physical exercise improves the structure and mechanical properties of

the tendon. Therefore, the results of this study suggest that physical exercise improves the tibia

and tendon strength in broilers raised on WS litter and LDe. In this study, TEZ litter and LDe

showed lower moisture content than WS litter and HDe. These results are explained by the low

moisture retention of TEZ due to its good aeration property, and the low stocking density used in

Page 11 of 30



For Review O

nly

12

this study. The incidence of foot pad lesions is influenced by stocking density and physical

characteristics of the litter material (Dawkins et al. 2004, Almeida-Paz et al. 2010). The birds

from the TEZ-LDe treatment had lower values for FPL than birds from the other treatments.

Although FPL increased with the age of birds, as expected, it was observed that TEZ-LDe

reduced the incidence of these injuries. This finding can be due to the fact that TEZ litter and

LDe showed low moisture content. Buijs et al. (2009) reported that foot pad lesions are more

serious as the stocking density increases. The results of this study indicate that tezontle retains

less moisture, so that this substrate contributes to a reduction of FPL, and improves the GS of

broilers. Our findings are consistent with those reported by Bessei (2006) that litter moisture

increases with stocking density, which in turn adversely affects the broiler´s welfare, and by

Almeida-Paz et al. (2010) that high moisture litter increases the incidence and severity of foot

pad lesions.

Gait score was not affected by litter material or stocking density (P > 0.05); however, a trend of

improvement in the TEZ-LDe group was observed. The GS was improved in birds reared at

LDe, which may be due to the low incidence of FPL observed in the TEZ-LDe treatment. Nääs

et al. (2009) reported that the decline in walking ability leads to hock burns because the chickens

spend more time lying on a poor-quality litter. The LTL variable was not affected by litter

material or stocking density; however, it was negatively affected by age. This can be explained

because body weight increases with age, and birds with lameness problems cannot bear their

body weight when subjected to the latency to lie test (Weeks et al. 2002).

The cortical bones of fast growing chickens are highly porous, which may lead to leg deformities

(Shim et al. 2012) such as valgus/varus angulation. In this study, birds in the WS-LDe group had

less angulation scores at d 25 and d 39 than birds in the other groups. Similarly, at d 32 the birds

Page 12 of 30



For Review O

nly

13

from the TEZ-LDe group showed less VAng than birds in the other groups. The incidence of

valgus/varus angulation decreases in birds that are more active (Bradshaw et al. 2002) due to a

wider space when reared at a low stocking density.

Regarding production variables, it has been reported that a high stocking density increases the

net profit of broilers production, although the individual weight gain is negatively affected

(Bessei 2004). Feed intake and body weigth gain were lower in birds housed at HDe than in birds

housed at LDe throughout the growing period, except for week 1. This can be attributed to the

fact that birds had less space to walk towards feeders due to the HDe effect. Bessei (2006)

reported that feed intake and body weight gain are reduced by heat stress rather than physical

restriction of the available space, because the transfer of heat from the litter surface to the

environment is inhibited by the birds due to high stocking density. The high litter temperature

results from the high moisture content that increases the microbial activity which in turn leads to

thermal discomfort of the birds (Bessei 2006, Meluzzi and Sirri 2009). In this study, no

differences were observed for feed conversion between stocking densities. These results agree

with those reported by Dozier et al. (2005) and Abudabos et al. (2013), showing that stocking

density did not affect feed conversion. Valdivié and Dieppa (2002) reported that high densities

increase facilities-use efficiency, as was observed in the HDe group where more meat (BW kg m-

2) was produced. Slaughter and carcass weight of chickens reared at LDe were higher than those

of chickens reared at HDe. Dozier et al. (2006) reported that carcass weight decreases linearly as

stocking density increases. For non-deboned drumsticks weight, no differences were found

among treatments, probably because a greater amount of muscle was deposited in the breast. In

conclusion, the use of tezontle along with a low stocking density reduced foot pad lesions and

litter moisture without compromising productive performance and carcass yield. However,

Page 13 of 30



For Review O

nly

14

tezontle negatively affected tendon resistance, whereas wood shavings litter improved tendon

breaking strength and valgus/varus angulation.

ACKNOWLEDGMENTS

This work was supported by the TAMU-Conacyt collaborative research grant program (grant

2011-029 awarded to Ruiz-Feria and Pro-Martinez). Vargas-Galicia is a master’s degree student

at Colegio de Postgraduados.

REFERENCES

Abudabos, A. M., Samara, E. M., Hussein, E. O. S., Al-Ghadi, M. Q. and Al-Atiyat R. M. 2013. Impacts of stocking density on the performance and welfare of broiler chickens. Italian J. Anim. Sci. 12: 66-71.

Almeida-Paz, I. C. L., García, R. G., Bernardi, R., Nääs, I. A., Caldara, F. R., Freitas, L. W., Seno, L. O., Ferreira, V. M. O. S., Pereira, D. F. and Cavichiolo, F. 2010. Selecting appropriate bedding to reduce locomotion problems in broilers. Braz. J. Poult. Sci. 12 (3): 189-195.

Association of Official Analytical Chemists. 1990. Official methods of analysis. 15th ed. AOAC, Arlington, VA.

Aviagen. 2009. Ross Broiler Management Manual. Aviagen Ltd., Midlothian, UK.

Baitshotlhi, J. C., Moreki, J. C., Tsopito C. M. and Nsoso, S. J. 2014. Influence of stocking density on bone development in family chickens reared up to 18 weeks of age under intensive system. Int. J. Poult. Sci. 13 (11): 652-656.

Benevides, G. P., Pimentel, E. R., Toyama, M. H., Novello, J. C., Marangoni, S. and Gomes, L. 2004. Biochemical and biomechanical analysis of tendons of caged and penned chickens. Connect. Tissue Res. 45: 206-215.

Berg, C. C. 2004. Pododermatitis and hock burn in broiler chickens. Pages 37-49 in Weeks, C. A. and Butterworth, A. (Eds.) Measuring and Auditing Broiler Welfare. CAB International. Wallingford, UK.

Berg, C. and Sanotra, G. S. 2003. Can a modified latency-to-lie test be used to validate gait-scoring results in commercial broiler flocks? Anim. Welf. 12: 655-659.

Bessei, W. 2004. Stocking density. Pages 133-143 in Weeks, C. A. and Butterworth, A. (Eds) Measuring and Auditing Broiler Welfare. CABI Publishing, Wallingford, UK.

Page 14 of 30



For Review O

nly

15

Bessei, W. 2006. Welfare of broilers: a review. World’s Poult. Sci. J. 62: 455-466.

Bradshaw, R. H., Kirkden, R. D. and Broom, D. M. 2002. A review of the aetiology and pathology of leg weakness in broilers in relation to welfare. Avian Poult. Biol. Rev. 13 (2): 45-103.

Buijs, S., Keeling, L., Rettenbacher, S., Van Poucke, E. and Tuyttens, F. A. M. 2009. Stocking density effects on broiler welfare: Identifying sensitive ranges for different indicators. Poult. Sci. 88: 1536-1543.

Buijs, S., Van Poucke, E., Van Dongen, S., Lens, L., Baert, J. and Tuyttens, F. A. M. 2012. The influence of stocking density on broiler chicken bone quality and fluctuating asymmetry. Poult. Sci. 91: 1759-1767.

Dawkins, M. S., Donnelly, A. and Jones, T. A. 2004. Chicken welfare is influenced more by housing conditions than by stocking density. Nature. 427: 342-344.

Dozier, W. A., Thaxton, J. P., Purswell, J. L., Olanrewaju, H. A., Branton S. L. and Roush, W. B. 2006. Stocking density effects on male broilers grown to 1.8 kilograms of body weight. Poult. Sci. 85: 344-351.

Dozier, W. A., Thaxton, J. P., Branton, S. L., Morgan, G. W., Miles, D. M., Roush, W. B., Lott, B. D. and Vizzier-Thaxton, Y. 2005. Stocking density effects on growth performance and processing yields of heavy broilers. Poult. Sci. 84: 1332-1338.

Garner, J. P., Falcone, C., Wakenel, P., Martin, M. and Mench, J. A. 2002. Reliability and validity of a modified gait scoring system and its use assessing tibial dyschondroplasia in broilers. Br. Poult. Sci. 43: 355-363.

Kestin, S. C., Knowles, T. G., Tinch, A. E. and Gregory, N. G. 1992. Prevalence of leg weakness in broiler chickens and its relationship with genotype. Vet. Rec. 131: 190-194.

Leterrier, C. and Nys, Y. 1992. Clinical and anatomical differences in varus and valgus deformities of chick limbs suggest different aetio‐pathogenesis. Avian Pathol. 21: 429-442.

Meluzzi, A. and Sirri, F. 2009. Welfare of broiler chickens. Ital. J. Anim. Sci. 8 (Suppl. 1): 161-173.

Meluzzi, A., Fabbri, C., Folegatti, E. and Sirri, F. 2008. Survey of chicken rearing conditions in Italy: effects of litter quality and stocking density on productivity, foot dermatitis and carcase injuries. Br. Poult. Sci. 49 (3): 257-264.

Mench, J. 2004. Lameness. Pages 3-17 in Weeks, C. A. and Butterworth, A. (Eds) Measuring and Auditing Broiler Welfare. CAB International. Wallingford, UK.

Page 15 of 30



For Review O

nly

16

Murillo, S. B., Cuca, M. G. and Aguilera, A. A. 1967. Empleo de tezontle (Espuma volcánica) como material de cama para aves. Rev. Mex. Cienc. Pecu. 10: 9-13.

Nääs, I. A., Almeida-Paz, I. C. L., Baracho, M. S., Menezes, A. G., Bueno, L. G. F., Almeida, I. C. L. and Moura, J. D. 2009. Impact of lameness on broiler well-being. J. Appl. Poult. Res. 18: 432-439.

Nakagaki, W. R., Biancalana, A., Benevides, G. P. and Gomes, L. 2007. Biomechanical and biochemical properties of chicken calcaneal tendon under effect of age and nonforced active exercise. Connec. Tissue Res. 48: 219-228.

Norma Oficial Mexicana. NOM-033-SAG/ZOO-2014. Métodos para dar muerte a los animales domésticos y silvestres. Diario Oficial de la Federación. 26 de Agosto de 2015. México.

SAS Institute, Inc. 2011. SAS User's Guide: Statistics version. SAS Institute, Inc. Cary, NC. 959 pp.

Shim, M. Y., Karnuah, A. B., Anthony, N. B., Pesti, G. M. and Aggrey, S. E. 2012. The effects of broiler chicken growth rate on valgus, varus, and tibial dyschondroplasia. Poult. Sci. 91: 62-65.

Škrbić, Z., Pavlovski, Z., Vitorović, D., Lukić, M. and Petrićević, V. 2009. The effects of stocking density and light program on tibia quality of broilers of different genotype. Arch. Zoot. 12 (3): 56-63.

Sorensen, P., Su, G. and Kestin, S. C. 2000. Effects of age and stocking density on leg weakness in broiler chickens. Poult. Sci. 79: 864-870.

Su, G., Sorensen, P. and Kestin, S. C. 1999. Meal feeding is more effective than early feed restriction at reducing the prevalence of leg weakness in broiler chickens. Poult. Sci. 78: 949-955.

Tablante, N. L., Estevez, I. and Russek-Cohen, E. 2003. Effect of perches and stocking density on tibial dyschondroplasia and bone mineralization as measured by bone ash in broiler chickens. J. Appl. Poult. Res. 12: 53-59.

Trejo-Téllez, L. I., Ramírez-Martínez, M., Gómez-Merino, F. C., García-Albarado, J. C., Baca-Castillo, G. A. and Tejeda-Sartorius, O. 2013. Evaluación física y química de tezontle y su uso en la producción de tulipán. Rev. Mex. Cienc. Agríc. 5: 863-876.

Valdivié, M., y Dieppa, O. 2002. Densidad de pollos de ceba. Porciones comestibles/m2. Revista Cubana de Ciencia Agrícola. 36 (2): 137-140.

Page 16 of 30



For Review O

nly

17

Vázquez-García, J. C. y Pérez-Padilla, R. 2000. Valores gasométricos estimados para las principales poblaciones y sitios a mayor altitud en México. Rev. Inst. Nal. Enf. Resp. Mex. 13: 6-13.

Venalainen, E., Valaja, J. and Jalava, T. 2006. Effects of dietary metabolisable energy, calcium and phosphorus on bone mineralisation, leg weakness and performance of broiler chickens. Br. Poult. Sci. 47: 301-310.

Weeks, C. A., Knowles, T. G., Gordon, R. G., Kerr, A. E., Peyton, S. T. and Tilbrook, N. T. 2002. New method for objectively assessing lameness in broiler chickens. Vet. Rec. 151: 762-764.

Page 17 of 30



For Review O

nly

18

ABBREVIATIONS

TEZ, Tezontle

WS, Wood shavings

LDe, Low density stocking, 13 birds m-2 (30.0 kg BW m-2 of floor space)

HDe, High density stocking, 18 birds m-2 (42.0 kg BW m-2 of floor space)

TiBS, Tibia breaking strength, N

TeBS, Tendon breaking strength, N

LTL, Latency to lie down, s

GS, Gait score, %

FPL, Foot pad lesions, %

VAng, Valgus/varus angulation, %

N, Newtons

A, Amperes

V, Volts

Page 18 of 30



For Review O

nly

19

Figure captions

Figure 1. Tibia breaking strength of broilers raised on either volcanic rock (tezontle, TEZ) or

wood shavings (WS) litter, with a stocking density of either 13 (LDe) or 18 birds m-2 (HDe)

corresponding to 30.0 or 42.0 kg of predicted final BW m-2 of floor space, respectively. a,

bDifferent letters on each bar (mean ± standard error of 48 observations), either within litter

material or stocking density indicate significant differences (P < 0.05).

Figure 2. Tendon breaking strength of broilers raised on either volcanic rock (tezontle, TEZ) or

wood shavings (WS) litter, with a stocking density of either 13 (LDe) or 18 birds m-2 (HDe)

corresponding to 30.0 or 42.0 kg of predicted final BW m-2 of floor space, respectively. a,

bDifferent letters on each bar (mean ± standard error of 48 observations), either within litter

material or stocking density indicate significant differences (P < 0.05).

Figure 3. Ash, calcium and phosphorus contents in bone of broilers raised on either volcanic

rock (tezontle, TEZ) or wood shavings (WS) litter, with a stocking density of either 13 (LDe) or

18 birds m-2 (HDe) corresponding to 30.0 or 42.0 kg of predicted final BW m-2 of floor space,

respectively. No statistical differences were observed (P > 0.05), either within litter material or

stocking density. Each bar represents the mean ± standard error of 48 observations.

Figure 4. Latency to lie down (LTL) of broilers assessed at different ages. a, bDifferent letters on

each bar indicate significant differences (P < 0.05). Each bar represents the mean ± standard

error of 96 observations (24 birds per treatment). Neither litter material nor stocking density or

its interaction affected LTL (P > 0.05).

Page 19 of 30



For Review Only

1

Figure 1.

220

230

240

250

260

270

280

290

TEZ WS LDe HDe

Litter material Stocking density

Tib

ia break

ing stren

gth

(N)

a

b

Page 20 of 30



For Review Only

1

Figure 2.

60

80

100

120

140

160

180

200

TEZ WS LDe HDe


Tendon breaking strength (N)

a

b

Page 21 of 30



For Review Only

1

Figure 3.

0

5

10

15

20

25

30

35

40

45

TEZ WS LDe HDe


Ash, Calcium and Phosporus (g 100 g

-1)

Ash Calcium Posphorus

Page 22 of 30



For Review Only

1

Figure 4.

100

150

200

250

300

350

400

450

500

550

600

25 32 39

Latency to lie down (s)

Age (d)

a a

b

Page 23 of 30



For Review O

nly

Table 1. Frequency (%) of gait scores at different ages of broilers raised on either tezontle

or wood shavings litter, with a stocking density of either 13 or 18 birds m-2

.

aTEZ-LDe, tezontle-13 birds m

-2 (30.0 kg of predicted final BW m

-2 of floor space);

bTEZ-

HDe, tezontle-18 birds m-2

(42.0 kg of predicted final BW m-2

of floor space); cWS-LDe,

wood shavings-13 birds m-2

; dWS-HDe, wood shavings-18 birds m

-2. P values: litter

material = 0.580; stocking density = 0.159; and age ˂ 0.001. All interactions were not

significant (P > 0.05). Briefly, a score of 0 denotes a bird with fluid locomotion and a

furled paw when it is raised and a score of 5 denotes a bird in complete lameness that

cannot walk or stand [Kestin et al. (1992) modified by Garner et al. (2002)].

Gait scores

Treatment 0 1 2 3 4 5 aTEZ-LDe 51.38 13.88 29.16 5.55 0.00 0.00

bTEZ-HDe 25.00 31.94 33.33 9.72 0.00 0.00

cWS-LDe 33.33 34.72 27.78 4.17 0.00 0.00

dWS-HDe 40.27 27.77 26.38 5.55 0.00 0.00

Age (d)

25

77.08 22.92 0.00 0.00 0.00 0.00

32 32.29 36.46 30.21 1.04 0.00 0.00

39 3.13 21.88 57.29 17.71 0.00 0.00

Page 24 of 30



For Review O

nly

1

Table 2. Frequency (%) of foot pad lesion scores at different ages of broilers raised on either

tezontle or wood shavings litter, with a stocking density of either 13 or 18 birds m-2

.



-2 of floor space);

bTEZ-HDe,

tezontle-18 birds m-2


of floor space); cWS-LDe, wood

shavings-13 birds m-2


-2. P values: litter material = 0.792;

stocking density = 0.100; age ˂ 0.001; and litter material × stocking density × age = 0.003.

Double interactions were not significant (P > 0.05). Foot pad lesions are based on a combined

score for both paws from 0 to 3, in which: 0, no sign of damage; 1, small scab < 5% pad area; 2,

large scab < 25% pad area and; 3, severe burn, large scab-filled ulcers, > 25% pad area and

inflammation (Su et al. 1999).

Foot pad lesion scores

Treatment 0 1 2 3

25 d of age aTEZ-LDe 25.00 70.83 4.16 0.00

bTEZ-HDe 0.00 54.16 45.83 0.00

cWS-LDe 0.00 58.33 41.66 0.00

dWS-HDe 12.50 75.00 12.50 0.00

32 d of age

TEZ-LDe 0.00 70.83 29.16 0.00

TEZ-HDe 0.00 0.00 66.66 33.33

WS-LDe 0.00 8.33 70.83 20.83

WS-HDe 4.16 50.00 45.83 0.00

39 d of age

TEZ-LDe 0.00 33.33 58.33 8.33

TEZ-HDe 0.00 4.16 66.66 29.17

WS-LDe 0.00 25.00 58.33 16.66

WS-HDe 0.00 29.16 62.50 8.33

Page 25 of 30



For Review O

nly

1

Table 3. Frequency (%) of leg angulation scores at different ages of broilers raised on either

tezontle or wood shavings litter, with a stocking density of either 13 or 18 birds m-2

.

Angulation scores

Treatment 0 1 2 3

25 d of age aTEZ-LDe 62.50 37.50 0.00 0.00

bTEZ-HDe 62.50 37.50 0.00 0.00

cWS-LDe 83.33 16.66 0.00 0.00

dWS-HDe 70.83 29.16 0.00 0.00

32 d of age

TEZ-LDe 58.33 41.66 0.00 0.00

TEZ-HDe 29.17 54.16 16.66 0.00

WS-LDe 41.66 29.17 29.16 0.00

WS-HDe 41.66 58.33 0.00 0.00

39 d of age

TEZ-LDe 25.00 58.33 16.66 0.00

TEZ-HDe 16.66 58.33 25.00 0.00

WS-LDe 33.33 62.50 4.16 0.00

WS-HDe 20.83 62.50 16.66 0.00



-2 of floor space);

bTEZ-HDe,

tezontle-18 birds m-2


of floor space); cWS-LDe, wood

shavings-13 birds m-2


-2. P values: litter material = 0.600;

stocking density = 0.374; age ˂ 0.001; and litter material × stocking density × age = 0.046.

Double interactions were not significant (P > 0.05). Valgus/varus angulation was evaluated

according to the methodology described by Leterrier and Nys (1992): 4 scores were defined: 0,

normal chicken; 1, chicken with little angulation (tibia-metatarsus angle between 10 and 25°); 2,

bird with obvious angulation (angle between 25 and 45°) and 3, severe angulation (angle greater

than 45°).

Page 26 of 30



For Review O

nly

1

Table 4. Moisture content (g 100 g-1

) of litter material at three different ages of broilers raised on

either tezontle or wood shavings litter, with a stocking density of either 13 or 18 birds m-2

.

Note: Means between litter materials or stocking densities not sharing a lowercase italic letter

differ significantly at the P < 0.05 level. aLitter material: TEZ, tezontle; WS, wood shavings.

bStocking density: LDe, 13 birds m


-2 of floor space); HDe, 18

birds m-2


of floor space). P values: litter material ˂ 0.001;

stocking density = 0.014; and age ˂ 0.001. All interactions were not significant (P > 0.05).

cSEM, standard error of mean.

Litter materiala Stocking density

b

Age (d) TEZ WS LDe HDe SEMc

25 18.17b 46.92a 26.60b 38.47a 2.97

32 30.71b 47.56a 35.64b 42.69a 2.94

39 31.75b 47.25a 37.18a 41.97a 2.97

Page 27 of 30



For Review Only

1

Table 5. Productive performance of broilers raised on either tezontle or wood shavings litter, with a stocking density of either 13 or 18

birds m-2

.

Item

Week

P value

1 2 3 4 5 6 SEMc

Litter

material

Stocking

density Age

Feed intake (g/bird/wk)

LDea 173a 302a 604a 809a 1255a 1265a

18 0.093 ˂ 0.001 ˂ 0.001 HDe

b 152a 255b 525b 754b 1133b 1212b

BW gain (g/bird/wk)

LDe 132a 191a 401a 470a 641a 684a 12 0.070 ˂ 0.001 ˂ 0.001

HDe 122a 164b 360b 440b 591b 629b

Feed conversion (g/g)

LDe 1.31 1.58 1.50 1.72 1.96 1.85 0.04 0.983 0.090 ˂ 0.001

HDe 1.24 1.55 1.45 1.71 1.92 1.93

Note: Means within the same column not sharing a lowercase italic letter differ significantly at the P < 0.05 level.

aLDe, 13 birds m


-2 of floor space).

bHDe, 18 birds m


-2 of floor space).

cSEM, standard error of mean. All interactions were not significant (P > 0.05).

Page 28 of 30



For Review O

nly

1

Table 6. Cumulative productive performance (during 6 wk) of broilers raised on either tezontle

or wood shavings litter, with a stocking density of either 13 or 18 birds m-2.

Note: Means between stocking densities not sharing a lowercase italic letter differ significantly

at the P < 0.05 level.

aLDe, 13 birds m


-2 of floor space).

bHDe, 18 birds m


-2 of floor space).


Stocking density P value

Item LDea HDe

b

SEM

c

Litter

material

Stocking

density

Litter material ×

stocking density

Feed intake (g/bird) 4409a 4029b 38 0.108 <0.001 0.309

BW gain (g/bird) 2520a 2273b 41 0.714 0.001 0.716

Feed conversión (g/g) 1.75 1.78 0.03 0.465 0.538 0.286

Page 29 of 30



For Review Only

1

Table 7. Slaughter performance (at 45 d of age) of broilers raised on either tezontle or wood shavings litter, with a stocking density of

either 13 or 18 birds m-2.

Note: Means between stocking densities not sharing a lowercase italic letter differ significantly at the P < 0.05 level.

aLDe, 13 birds m


-2 of floor space).

bHDe, 18 birds m


-2 of floor space).


Stocking density P value

Item LDea HDe

b

SEM

c

Litter

material

Stocking

density

Litter material ×

stocking density

Slaughter weight (g/bird) 2773a 2554b 32 0.419 0.004 0.335

Carcass yield (g/bird) 2216a 2002b 31 0.853 0.004 0.529

Non-deboned drumsticks weight (g) 382 367 8 0.374 0.123 0.507

Page 30 of 30



Documents

For Review Only - University of Toronto T-Space · For Review Only 3 weight gain (Abudabos et al. 2013) and also has a negative effect on bird´s welfare (Meluzzi and Sirri 2009)