Journal of Applied Animal Research ISSN: (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/taar20 Effect of body weight on uniformity, livability, and skeletal development and strength of broiler breeder females X. Asensio, J. Piedrafita, A. Puente & A. C. Barroeta To cite this article: X. Asensio, J. Piedrafita, A. Puente & A. C. Barroeta (2020) Effect of body weight on uniformity, livability, and skeletal development and strength of broiler breeder females, Journal of Applied Animal Research, 48:1, 320-325, DOI: 10.1080/09712119.2020.1789647 To link to this article: https://doi.org/10.1080/09712119.2020.1789647 © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group Published online: 09 Jul 2020. Submit your article to this journal Article views: 1568 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at https://www.tandfonline.com/action/journalInformation?journalCode=taar20 JOURNAL OF APPLIED ANIMAL RESEARCH 2020, VOL. 48, NO. 1, 320–325 https://doi.org/10.1080/09712119.2020.1789647 BROILER BREEDER BODY WEIGHT AND SKELETAL DEVELOPMENT Effect of body weight on uniformity, livability, and skeletal development and strength of broiler breeder females X. Asensioa,b, J. Piedrafitac, A. Puenteb and A. C. Barroetaa a Animal Nutrition and Welfare Service (SNIBA), Department of Animal and Food Science, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain; bAviagen S.A.U., Palau-Solità i Plegamans, Spain; cDepartment of Animal and Food Science, Facultat de Veterinària, Universitat Autònoma de Barcelona, Barcelona, Spain ABSTRACT ARTICLE HISTORY An experiment was conducted with broiler breeder females (up to 30 wks of age) to study the effect of Received 19 December 2019 body weight (BW) at 5 wks on BW uniformity, livability, and skeletal development and strength. At 5 wks Accepted 23 June 2020 of age, 160 females were randomly selected within a flock of 1,988, and they were reared without KEYWORDS grading. Among these 160 females, the 40 with the lowest BW (Light Non-Graded, LNG) and the 40 with Broiler breeders; uniformity; the highest BW (Heavy Non-Graded, HNG) were studied. LNG females, compared to HNG, had a higher grading; skeletal BW coefficient of variation (CV) from 10 to 25 wks (P ≤ 0.05). At 25 wks, mortality of the LNG females development and strength was higher (20.0% vs. 2.5%, P = 0.027); they had shorter tibias (P ≤ 0.05), and a tendency to lower-tibia breaking strength (P = 0.085) and elastic modulus (P = 0.072). At 5 wks, their alkaline phosphatase was lower (2781 UI vs. 3839 UI, P = 0.023), and taking together 5 and 10 wks their osteocalcin was also lower (976 ng vs. 1239 ng, P = 0.029). Results indicate that without grading in rearing, light females had lower BW uniformity, lower livability, shorter and less resistant tibias than heavy females. Introduction bone strength, which enables the skeleton to withstand gravity and additional loading. Correct management of broiler breeders is essential to prevent Alkaline phosphatase (ALP) and osteocalcin (OC), which are having uneven flocks, where larger or aggressive females are serological markers of bone formation (Seibel 2005), might likely to out-compete smaller or timid pullets, resulting in provide direct insight into skeletal development, particularly unequal access to feed and increasing flock body weight (BW) bone growth. These markers are currently used in humans to variation (Zuidhof et al. 2015). Grading is a management tool evaluate bone metabolism, and provide a real-time assessment used in broiler breeder rearing farms, with the purpose of of bone formation, resorption and turnover. Ekmay et al. (2012) increasing BW uniformity. The flock is divided into pens (normally used ALP serological levels to assess broiler breeder growth and 2 or 3) of females with different average BWs (physiological bone mineral deposition during transition into sexual maturity; state), so that each pen can be managed in a way that will nevertheless, these two serological markers have not been used result in bringing the whole flock back to the standard BW to date in broiler breeder females to assess their development. profile and in good, whole flock uniformity at the point of laying. ALP is a ubiquitous enzyme attached on the outer cell surface Uniform flocks are easier to manage, since the birds will (Stinson and Hamilton 1994). The precise function of the respond similarly to management factors such as light stimu- enzyme is as yet unknown, but it obviously plays an important lation and increasing of the feed ration (Ross Parent Stock Man- role in osteoid formation and mineralization (Harris 1990). OC is agement Handbook. Aviagen 2013b). However, low uniformity considered a specific marker of osteoblast function (Brown et al. may result in broiler breeder pullets being under the advised 1984). It is estimated that, directly after its release from the standard BW, not having received the nutrients required, thus osteoblast, the largest part of the newly synthesized protein is leading to the poor body and skeletal development, which incorporated into the extracellular bone matrix, but a smaller might cause leg health issues. fraction is released into the blood circulation where it can be Bone measurements, such as bone breaking strength (BS) detected by immunoassays (Bouillon et al. 1992; Monaghan and elastic modulus (EM), have been used as indicators of et al. 1993; Parviainen et al. 1994; Chen et al. 1996). bone status in several studies (Rath et al. 2000; Lewis et al. As was explained before, broiler breeder flocks under the 2009; Shastak et al. 2012; Shim et al. 2012). Bone strength is standard BW and with low uniformity might lead to poor skel- determined not only by the volume of bone tissue and the etal development and leg health issues, which cause economic micro-architectural organization, but also by the degree of min- losses to breeder producers. Therefore, it is important to evalu- eralization of the bone matrix (Boivin and Meunier 2002). Nutri- ate bone development and strength in the rearing period to tional deficiencies may affect bone mineralization and, in turn, prevent these issues. CONTACT X. Asensio xasensio@aviagen.com Animal Nutrition and Welfare Service (SNIBA), Department of Animal and Food Science, Facultat de Veterinària, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain; Aviagen S.A.U., Palau-Solità i Plegamans, 08184, Spain © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distri- bution, and reproduction in any medium, provided the original work is properly cited. JOURNAL OF APPLIED ANIMAL RESEARCH 321 The aim of this study is to evaluate whether 5-wk-old broiler heaviest females (over the standard BW at 5 wks) and that breeder females with a lower BW than standard and never was named Heavy Non-Graded (HNG). graded in rearing are affected in their BW uniformity, livability, The females of the flock (1828, 1988 birds minus 160) were and skeletal development and strength. Likewise, the useful- graded-divided depending on their BW (Graded Flock). At 5, ness of two different serological markers is proposed to 12 and 18 wks, they were weighed individually, and each time assess the skeletal development throughout the initial phase they were divided into three different BW pens: light (20%), of the broiler breeders in the rearing period. medium (70%) and heavy (10%) females. The pens were managed during the rearing period to bring them back to the standard BW profile, and in good, whole flock uniformity at Materials and methods the point of laying. The 160 Non-Graded females always stayed together and mixed in the Graded Flock (inside the Birds and facility pen of the medium BW), with the aim of studying the birds of All of the animal experimentation procedures used in the exper- the experimental groups (LNG and HNG) in commercial con- iment were approved by the animal Ethics Committee of the ditions, but without any grading. Universitat Autònoma de Barcelona (UAB; Barcelona, Spain) and were in compliance with the European Union guidelines Feeding program, diets and feed intake for the care and use of animals in research (European Parlia- ment 2010). Feed was produced in a feed mill of CAG (Tarragona, Spain). The A total of 1,988 Ross 308 broiler-breeder female chicks were different diets were formulated according to Ross 308 Parent placed in an all-in all-out commercial farm during a period from Stock Nutrition Specifications (Aviagen 2013a). A five-diet- 0 to 30 wks of age. A vaccination programme adapted to the phase feeding programme was followed: starter I (from 0 to epidemiology of the farm area was followed throughout the 3 wks of age), starter II (from 4 to 6 wks), grower (from 7 to rearing period. Management applied was according to the 15 wks), pre-breeder (from 16 to 24 wks) and breeder (from guidelines of the Ross Parent Stock Management Handbook 25 to 30 wks). Feed form presentation was crumble. The ingre- (Aviagen 2013b). dients and nutrient composition are shown in Table 1. Until 21 wks of age, pen dimensions were 48.50 m long by Feed was provided ad libitum during the first 2 wks in order 6.5 m wide, 315.25 m2 in total, with 6.30 females/m2. Feed to ensure a correct initial development. From this point on, in space was 0.87 females per pan hole and drinking space was order to follow the standard BW profile, the total daily feed dis- 5.58 females per nipple. At 21 wks old, the females could use tributed was weekly calculated by multiplying all of the females the whole house and mixed with the males (ratio 10/1). From present at the moment by the daily metabolizable energy this moment, stock density was 5.30 females/m2, feed space (AMEn) allowance per bird and divided by the AMEn of the was 0.74 females per pan hole and drinking space was 4.74 diet. The average BWs of the three different BW pens of the females per nipple. Throughout the whole trial, feed and Graded Flock were taken into account to decide the daily drinker space was sufficient for all the birds to reach feed and AMEn allowance per bird in each pen. Both the standard BW water at the same time. Wood shavings were utilized as litter profile and daily AMEn allowance per female were based on material, and litter was topped up weekly to keep it dry. Ross 308 Parent Stock Performance Objectives (Aviagen 2012). The house was environmentally controlled and the tempera- ture set-point was modified depending on the birds’ age, starting Collected data, sampling and analytical determinations with 32°C at one day old, and decreasing on a regular basis until 20°C at 27 d old; this set-point was kept until the end of the trial. Feed. Experimental feed samples were collected from the The lighting programme was 23 h of light during the first 4 d and, different diets supplied during the rearing and production then, gradually reduced to 8 h until 14 d; from 2 to 20 wks the periods of the trial. These samples were ground and stored at birds had 8 h of light, and later on light was increased 1 h per 5°C until their analyses. Diet proximate analyses were per- wk until 14 h (26 wks). Light intensity was 100–80 lux the first formed according to the method of the Association of Official wk, 20 lux from 2 to 20 wks and 60 lux from then on. Manage- Agricultural Chemists (AOAC) International (2005): dry matter ment data such as light programme, light intensity and environ- (Method 934.01), crude protein (Method 968.06), crude fibre mental temperature were weekly recorded. (Method 962.09), crude fat (Method 2003.05) and ash content (Method 942.05). All analyses were carried out by the Servei de Nutrició i Benestar Animal (SNiBA) laboratory of the UAB. Body Weight, Uniformity and Mortality. The Graded Flock Trial description was monitored weekly by sampling BW and calculating the From a flock of 1,988 Ross 308 broiler breeder females, 160 birds BW coefficient of variation (CV). The females were randomly were randomly selected at 5 wks of age; they were individually caught (minimum 2% of the flock) by using catching frames, identified and never graded-divided during the rearing period, and all birds rounded up were weighed in order to eliminate depending on their BW. Within this group of Non-Graded any selective bias. All 160 Non-Graded females were individu- females, two experimental groups of weight were created: the ally weighed every 5 wks, starting when they were 5 wks old first quarter, which included the 40 lightest females (below and finishing at 30 wks old, and their BW CV calculated. the standard BW at 5 wks) and that was named Light Non- Tibia Parameters. To perform post-mortem analyses, 3 Graded (LNG), and the fourth quarter, which included the 40 females from the LNG and 3 females from the HNG were 322 X. ASENSIO ET AL. Table 1. Ingredients (%), metabolizable energy and nutritional composition of the US) (force resolution 0.001 N and distance resolution experimental diets. 0.001 mm). These two studies were carried out by IRTA (Institut Pre- de Recerca i Tecnologia Agroalimentaria, Girona, Spain). Starter I Starter II Grower breeder Breeder I 0 to 3 4 to 7 to 16 to 25 to Serological Markers. To determine ALP levels, the 14 light- wks 6 wks 15 wks 24 wks 30 wks est females of the LNG and the 14 heaviest females of the Wheat 35.2 36.2 27.7 33.1 30.8 HNG were blood-sampled at 5 and 10 wks of age. For OC deter- Soybean meal 25.6 17.8 - 6.2 15.8 mination, blood samples coming from the same females were Corn 24.5 31.6 30.0 35.0 38.0 Sunflower 28– 5.00 6.00 15.76 10.50 4.10 used, but only those of the 10 lightest birds of the LNG and 30% those of the 10 heaviest birds of the HNG were used. Wheat bran 3.00 1.23 19.70 7.00 – Blood samples were spun at 1107 g for 20 min to obtain the Dicalcium 2.33 2.23 1.87 1.53 1.70 phosphate serum, which was stored at −20°C until the moment to be pro- Rapeseed meal – 2.00 1.57 3.00 – cessed. To test ALP, a colorimetric method based on the cataly- Soybean oil 2.00 1.00 1.20 0.77 2.00 tic transformation of p-nitrophenylphosphate as substrate Limestone 0.97 0.90 0.90 1.87 6.57 Premix 1 0.30 0.30 0.30 0.30 0.30 (International Federation of Chemical Chemistry (IFCC) Sodium 0.27 0.24 0.22 0.20 0.18 method) on the Beckman Coulter AU analyser (Beckman bicarbonate Coulter, Inc.; Brea, CA 92821, US) was used. In the case of OC, Salt 0.23 0.23 0.21 0.23 0.24 L-lysine sulfate 0.23 – 0.26 0.12 0.03 the Rat-MIDTM Osteocalcin EIA (ELISA) (Immunodiagnostic 54.6% Systems Holdings Plc; Didcot Way, NE35 9PD; UK) was the test Methionine 0.20 0.10 0.11 0.10 0.14 performed. ALP and OC analyses were carried out by the Choline Cl-60% 0.10 0.10 0.10 0.07 0.07 Calcium pidolate 0.05 0.03 0.03 – – Servei de Bioquímica Clínica Veterinària (SBCV) of the UAB. Threonine 0.05 0.03 0.04 0.01 0.04 AMEn, Kcal/Kg 2810 2801 2550 2701 2800 Dry matter %2 89.0 88.6 88.6 88.7 89.4 Statistical analysis 2 Crude Protein % 20.7 16.9 13.3 14.4 14.8 dig Lys % 0.95 0.67 0.50 0.52 0.58 All statistical analyses were performed with the R® statistical dig Met % 0.47 0.35 0.32 0.32 0.35 software (version 3.5.1, R Core Team 2018). A one-way ANOVA dig M + C % 0.74 0.60 0.53 0.54 0.56 dig Thre % 0.64 0.54 0.39 0.42 0.47 was applied to analyse body weight data within each week. dig Trp % 0.20 0.17 0.13 0.14 0.14 The model was yij = µ + EGi + eij, where yij corresponds to Crude Fibre % 4.17 4.48 7.99 5.99 3.46 weight of the bird, EGi is the experimental group (Light Non- Crude Fat %2 4.06 3.05 3.98 3.02 4.13 Ash % 2 5.87 5.68 5.30 5.92 10.21 Graded and Heavy Non-Graded), and eij is the error term. Coeffi- Ca % 1.06 1.00 0.91 1.19 2.99 cients of variation were compared using the asymptotic test of dig P % 0.48 0.46 0.42 0.36 0.36 Feltz and Miller (1996) implemented in the R package cvequality 1 Premix provided per kilogram of diet: vitamin A (retinyl acetate), 10000 UI; (Version 0.1.3; Marwick and Krishnamoorthy 2019). Accumu- vitamin D3 (cholecalciferol), 1500 UI; 25-hydroxycholecalciferol, 0.0375 mg; vitamin E (DL-α-tocopheryl acetate), 100 UI; vitamin K3, 10.00 mg; Vitamin B1- lated mortality was analysed by contrasting the number of (thiamin), 7.00 mg; vitamin B2 (riboflavin), 20.00 mg; vitamin B5 (pantotfemaleic initial birds with the accumulated mortality through a Chi- acid), 27.22 mg; vitamin B6 (pyridoxine hydrochloride), 10.00 mg; vitamin B12 square Test for Count Data in the two experimental groups: (cyanocobalamin), 0.07 mg; vitamin B3 (nicotinic acid), 87.09 mg; vitamin B9 (folic acid), 5.00 mg; vitamin B7 (biotin), 0.60 mg; vitamin C (ascorbyl phosphate), Light Non-Graded and Heavy Non-Graded. Tibia length, Break- 150 mg; iodine, 2.00 mg; Mn (manganous oxide), 80.00 mg; Mn (manganese ing strength and Elastic modulus variables were analysed chelate), 40.00 mg; Cu (cupric sulfate), 6.00 mg; Cu (copper chelate), 10.00 mg; using a factorial design according to the following model: yijk Zn (zinc oxide), 60 mg; Zn (zinc chelate), 40.00 mg; Se (sodium selenite), 0.20 mg; Se (selenium organic form), 0.20 mg; Fe (ferrous carbonate), 65.00 mg. = µ + EGi + Wkj + EG*Wkij + eijk, where yijk was the observation 2 Analyzed values. for each of the 3 variables, EGi was the experimental group (Light Non-Graded and Heavy Non-Graded), Wkj was the week effect (5, 10, 15, 20, 25, 30), EG*Wkij was the interaction euthanized every 5 wks (starting at 5 wks and finishing at effect between experimental group and week, and eijk was 30 wks of age). the error. A mixed model was used to analyse Alkaline Phospha- Right legs were used to dissect tibias, which were utilized to tase and Osteocalcin serological levels: yijkl = µ + EGi + Wkj + determine tibia length (TL), tibia breaking strength (BS) EG*Wkij + Bl + eijk, where yijkl were the observations, EGi was as (maximum load endurance) and elastic modulus (EM). TL was before, Wkj had 2 week levels (5, 10), EG*Wkij was the inter- measured every 5 wks by using a caliper (0.03-mm precision action effect, Bl was the random effect of the bird, and eijkl and 0.01-mm resolution). BS and EM were determined at 15, was the error term. Means were compared through a Tukey 25 and 30 wks of age. The BS value is the load required to test. In all cases, P-values lower than 0.05 were considered to reach the point where the bone is no longer resilient and be significant. reflects the rigidity of the bone as a whole. The EM value is the slope of the linear region of the stress vs. strain-curve and Results and discussion reflects the intrinsic stiffness or rigidity and material properties of the bone (Turner and Burr 1993). Evolution of BW of the LNG and HNG from 5 to 30 wks is shown To measure BS and EM, the method of the 3-point flexural in Table 2. BW of the LNG was lower and significantly different bending test was carried out (Fleming et al. 1998). Measure- from that of the HNG until 25 wks of age. However, at 30 wks of ments were made by using a MTS Alliance RT/5 material age, BWs of the LNG and the HNG females were similar (LNG: testing system (MTS Systems Corp.; Eden Prairie, MN 55344, 3944 and HNG: 3995 g, P = 0.571). Light Non-Graded females JOURNAL OF APPLIED ANIMAL RESEARCH 323 Table 2. Body weight (g) of the Light Non-Graded (LNG) and Heavy Non-Graded Table 4. Accumulated mortality (%) of the Light Non-Graded (LNG) and Heavy (HNG) broiler breeder females. Non-Graded (HNG) broiler breeder females. Body weight (g) Accumulated mortality (%) Age (wks) LNG 1 HNG 2 SEM (n = 40) P-value Age (wks) LNG1 HNG2 P-value 5 587 831 6.2 <0.001 5 0 0 0 10 829 1184 16.9 <0.001 10 7.5 0 0.089 15 1346 1762 24.6 <0.001 15 12.5 0 0.030 20 2035 2438 42.3 <0.001 20 15.0 0 0.018 25 3292 3543 48.0 <0.01 25 20.0 2.5 0.027 30 3944 3995 59.8 0.571 30 22.5 7.5 0.115 Note: Non-Graded: 160 females randomly selected at 5 wks of age within the 1988 Note: Non Graded: 160 females randomly selected at 5 wks of age within the 1988 broiler breeder females kept in a standard breeder farm. broiler breeder females kept in a standard breeder farm. 1 1 The 40 lightest birds, below the standard body weight at 5 wks, of the Non- The 40 lightest birds, below the standard body weight at 5 wks, of the Non- Graded. Graded. 2 2 The 40 heaviest birds, over the standard body weight at 5 wks, of the Non- The 40 heaviest birds, over the standard body weight at 5 wks, of the Non- Graded. Graded. were under the standard BW profile (based on Ross 308 Parent (2015), who studied the effect of broiler breeder feeding man- Stock Performance Objectives; Aviagen, 2012), from 5 to 25 wks agement practices, and they reported that the grading treat- of age, whereas HNG were over the standard all throughout the ment resulted in the highest flock BW uniformity. trial; these results are not shown. Similar results were found in The present study shows that grading in rearing is essential to Renema et al.’s (1999) study; they reported that in feed intake obtain a correct uniformity, and that in the absence of grading, controlled broiler breeders, the 20% difference between the the lack of uniformity of the Non-Graded females comes from standard and low or high bird BW at 21 wks declined at the LNG; in fact, the HNG kept a correct BW CV (lower than sexual maturity to 5% and 4% for the low and high bird BW, 10%) throughout the trial. After 25 wks of age, the BW CV of respectively. In the present study, after 21 wks, feed allocation the LNG females decreased to a correct value (under 10%) and, was the same for all of the females, whereas the birds of the at 30 wks, their BW CV was similar to the HNG. These similar mentioned study (Renema et al. 1999) were fed at the level BW CVs and BWs of the LNG and HNG females at 30 wks might that maintained constant rates of gain in each body-size group. be explained by more feed availability, more feed space and a Evolution of BW CV of the Graded Flock, Non-Graded, LNG longer clean-up time in the production period; hence, the light and HNG females from 5 to 30 wks of age is shown in birds would be able to obtain more feed. Table 3. From 10 to 25 wks, the BW CV of the LNG females Accumulated mortality (%) of the LNG and HNG is shown in was higher and significantly different from that of the HNG. Table 4. Regarding LNG females, during the period from 5 to During this period, the BW CV of the LNG females was over 15 wks of age, they had their highest mortality (1.25%/wk); 10% (with a maximum of 12.9% at 10 wks), whereas that of after this, between 15 and 20 wks, their mortality decreased the HNG was under 10% throughout all the trial. At 30 wks, to 0.5%/wk. HNG females had no mortality at all from 5 to the BW CVs of the LNG and HNG females were similar and 20 wks. At 25 wks, the accumulated mortality of LNG was both, under 10%. According to Uniformity of Female Broiler 17.5% higher than that of HNG (20.0% vs. 2.5%, P = 0.027). At Breeders (Aviagen 2016), 10% should be the maximum value 30 wks, the LNG females had a higher accumulated mortality obtained if management is correct. (22.5%) than did those of the HNG (7.5%). From 5 to 20 wks of age, the BW CV of Non-Graded females The LNG females had their highest mortality between 5 and was higher and significantly different from that of the Graded 15 wks, when the weekly feed increase was lower; their lowest Flock. During this period, the BW CV of the Non-Graded mortality was between 15 and 20 wks, when feed availability females was over 10% (with a maximum of 15.5% at 10 wks), was higher, since this is the period of feed stimulation. whereas that of the Graded Flock was under 10% throughout However, from 5 to 20 wks of age the HNG females had no mor- all the trial, and specifically at 20 wks it was 6.5%. A similar tality at all, and were not affected by the period of a lower result, 6.2% at 22 wks of age, was obtained by Zuidhof et al. weekly feed increase. Table 3. Body weight coefficient of variation (%) of the Graded Flock and Non-Graded broiler breeder females, and of the Light Non-Graded (LNG) and Heavy Non-Graded (HNG) broiler breeder females. Coefficient of variation (%) Age (wks) Graded Flock1 n Non-Graded 2 n P-value LNG3 n HNG4 n P-value 5 8.2 40 13.3 160 <0.01 6.2 40 4.9 40 0.129 10 8.4 40 15.5 155 <0.001 12.9 37 8.1 40 <0.01 15 7.0 40 12.3 150 <0.001 11.8 35 7.0 40 <0.01 20 6.5 40 13.0 149 <0.001 12.5 34 8.6 40 0.029 25 7.0 40 8.1 143 0.286 11.0 32 6.7 39 <0.01 30 7.3 40 6.0 137 0.123 7.5 31 7.2 37 0.806 1 1828 broiler breeder females kept in a standard breeder farm (the initial 1988 minus the 160 females of the Non-Graded). 2 160 females randomly selected at 5 wks of age within the 1988 broiler breeder females. 3 The 40 lightest birds, below the standard body weight at 5 wks, of the Non-Graded. 4 The 40 heaviest birds, over the standard body weight at 5 wks, of the Non-Graded. 324 X. ASENSIO ET AL. Table 5. Tibia length, breaking strength and elastic modulus data according to Table 6. Alkaline Phosphatase and Osteocalcin serological levels according to broiler breeder body weight at 5 wks (LNG: Light Non-Graded and HNG: Heavy broiler breeder body weight at 5 wks (LNG: Light Non-Graded and HNG: Heavy Non-Graded) and weeks of age. Non-Graded) and weeks of age. Effects TL3 (mm) BS4 (kgf/mm2) EM5 (Kgf/mm) Effects ALP3 (UI) OC4 (ng/ml) Body weight Body weight LNG1 108 64.3 61.5 LNG1 2290 976 HNG2 120 71.4 68.9 HNG2 2949 1238 n 18 9 9 n 28 20 SEM 1.0 2.6 2.58 SEM 108.6 56.6 Age (wks) Age (wks) 5 86c 5 3374 1189 10 102b 10 1944 1025 15 120a 38.9b 37.9b n 28 20 20 126a SEM 108.6 56.6 25 125a 80.3a 75.6a Body weight/Age (wks) 30 126a 80.1a 78.2a LNG/5 2781b 1032 n 6 6 6 LNG/10 1798c 920 a SEM 1.8 3.2 3.16 HNG/5 3839 1346 P-value HNG/10 2059 bc 1130 Body weight <0.001 0.085 0.072 n 14 10 Age (wks) <0.001 <0.001 <0.001 SEM 153.6 79.6 Interaction 0.281 0.905 0.438 P-value Note: Non-Graded: 160 females randomly selected at 5 wks of age within the 1988 Body weight 0.032 0.029 broiler breeder females kept in a standard breeder farm. Age (wks) <0.001 0.050 a-c Means within a column and within a source with no common superscript differ Interaction 0.023 0.527 significantly. Note: Non-Graded: 160 females randomly selected at 5 wks of age within the 1988 1 The 40 lightest birds, below the standard body weight at 5 wks, of the Non- broiler breeder females kept in a standard breeder farm. a–c Graded. Means within a column and within a source with no common superscript differ 2 The 40 heaviest birds, over the standard body weight at 5 wks, of the Non-Graded significantly. 3 1 Tibia length. The 40 lightest birds, below the standard body weight at 5 wks, of the Non- 4 Breaking strength (maximum load endurance). Graded. 5 2 Elastic modulus (rigidity of the bone). The 40 heaviest birds, over the standard body weight at 5 wks, of the Non- Graded. 3 Alkaline Phosphatase. 4 Osteocalcin. In field conditions, results of this study indicate that livability of the LNG females (compared to the HNG) was lower, as the LNG probably consumed below their requirements. tibias and poorer bone mineralization than will the heavy Evolution of TL, BS and EM, according to BW at 5 wks (LNG ones. To recover bone development of the light females (to and HNG) and age (wk), is presented in Table 5. According to obtain compensatory growth) it might be necessary to grade BW, the LNG females had shorter tibias, as compared to the them early in rearing, since TL reaches its maximum at 15 wks HNG (108 mm vs. 120 mm, P < 0.001). Taking age into account of age and tibia BS and EM between 15 and 25 wks of age. (wk), TL increased between 5 and 15 wks, with weekly differ- This is in line with the statement that 90% of the skeleton of ences being significant. Within the period from 15 to 30 wks the broiler breeders is already developed at 11–13 wks (Ross of age, TL was not significantly different. This study shows Parent Stock Management Handbook. Aviagen 2013b). that the LNG females had shorter tibias than did the HNG, Evolution of ALP and OC serological levels of the LNG and which confirms that in the rearing period BW and skeletal HNG are presented in Table 6. An interaction BW/age (wk) growth are related, as has been observed by other authors shows that at 5 wks of age the LNG females had a significantly (Robinson et al. 2007). lower ALP level than did the HNG (2781 UI vs. 3839 UI, P = Regarding BW, BS results of the LNG tibias show a statistical 0.023), however no differences were observed at 10 wks. Like- tendency to support less weight before breaking, as compared wise, ALP levels of both LNG and HNG were significantly to the HNG tibias (64.3 and 71.4 kgf/mm2, P = 0.085). According higher at 5 wks, as compared to 10 wks of age (LNG: 2781 UI to age (wk), tibia BS at 15 wks was lower than at 25 and 30 wks vs. 1798 UI; HNG: 3839 UI vs. 2059 UI; P = 0.023). Regarding of age (38.9 vs. 80.3 and 80.1 kgf/mm2; P < 0.001). OC serological levels, related to BW at 5 wks, the LNG had a In the case of EM, and also regarding BW, results of the LNG lower OC level than did the HNG (976 ng/ml vs. 1238 ng/ml, tibias also show a statistical tendency to be intrinsically less rigid P = 0.029). If age (wk) is taken into account, results show a ten- or more elastic, when compared to the HNG tibias (61.5 and dency of a higher OC level at 5 wks than at 10 wks of age 68.9 kgf/mm; P = 0.072). According to age (wk), EM at 15 wks (1189 ng/ml vs.1025 ng/ml, P = 0.050). was lower than at 25 and 30 wks of age (37.9 vs. 75.6 and There are no studies which have used ALP or OC to assess skel- 78.2 kgf/mm; P < 0.001). etal growth in broiler breeders in rearing. However, in chickens, Therefore, BS and EM results show that tibias of the LNG elevated ALP activity has been predominantly related to females have lower load endurance and are more elastic than increased osteoblastic activity and used as a marker for evaluat- are the HNG, thus they are more vulnerable. This could be ing skeletal health and bone disease, such as skeletal growth, related to a bone with lower EM being less mineralized, as rickets, fracture repair and osteomyelitis (Lumeij and Westerhof may also be expected of a rachitic bone (Turner and Burr 1993). 1987). In the present study, regarding skeletal or bone growth, After these results, it might be concluded that the light it may be concluded that at 5 wks of age the LNG females had females in breeder rearing farms will always have shorter lower ALP serological levels than did the HNG, and taking into JOURNAL OF APPLIED ANIMAL RESEARCH 325 account 5 and 10 wks together, the LNG females had also lower Bouillon R, Vanderschueren D, Van Herck E, Nielsen HK, Bex M, Heyns W, Van OC levels, which also suggests that there is a relation between Baelen H. 1992. Homologous radioimmunoassay of human osteocalcin. Clin Chem. 38:2055–2060. BW and bone development. Therefore, these two serological Brown JP, Delmas PD, Malaval L, Edouard C, Chapuy MC, Meunier PJ. 1984. markers may be useful as additional information of BW and uni- Serum bone Gla-protein: a specific marker for bone formation in postme- formity, in order to assess if bone development is correct during nopausal osteoporosis. The Lancet. 323:1091–1093. the first 10 wks of the rearing period of the broiler breeders. Chen J-T, Hosoda K, Hasumi K, Ogata E, Shiraki M. 1996. Serum N-terminal Nevertheless, serological levels of ALP and OC are directly osteocalcin is a good indicator for estimating responders to hormone replacement therapy in postmenopausal women. J Bone Miner Res. related to skeletal or bone development, whereas BW is only 11:1784–1792. an indicator and does not directly relate to skeletal development. Ekmay RD, Salas C, England J, Cerrate S, Coon CN. 2012. The effects of pullet ALP and OC serological levels decrease significantly from 5 to body weight, dietary nonpyhtate phosphorus intake, and breeder 10 wks of age, which might confirm that when the females reach feeding regimen on production performance, chick quality, and bone 10 wks of age the rate of skeletal growth has already become remodeling in broiler breeders. Poult Sci. 91:948–964. European Parliament. 2010. Directive 2010/63/EU of the European reduced, and which is in turn related to this study result of TL Parliament and of the Council of 22 September 2010 on the protection ceasing to increase at 15 wks. From a management point of of animals used for scientific purposes. view, lower ALP and OC serological levels at 10 wks of age Feltz CJ, Miller GE. 1996. An asymptotic test for the equality of coefficients of suggest that at this age their skeletal development has already variation from k populations. Stat Med. 15(6):647–658. become reduced and, therefore, it is worth grading the Fleming RH, McCormack HA, McTeir L, Whitehead CC. 1998. Medullary bone and humeral breaking strength in laying hens. Res Vet Sci. 64:63–67. females early in rearing in order to recover the skeletal frame Harris H. 1990. The human alkaline phosphatases: what we know and what size of the light birds before their development starts to reduce. we don’t know. Clin Chim Acta. 186:133–150. 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