Date of Award
5-2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Animal and Veterinary Sciences
Committee Chair/Advisor
Ahmed Ali
Committee Member
Jeryl Jones
Committee Member
Mireille Arguelles-Ramos
Committee Member
William Bridges
Abstract
The objective of this dissertation was to evaluate the impact of environmental and nutritional enrichments on the behavior, bone health, and welfare of Hy-line brown and Hy-line W-36 laying hens. Laying hens are prone to experiencing a progressive increase in bone fragility due to the ongoing mobilization of calcium from the bones for eggshell formation. Over time, this increases their susceptibility for bone fracture, which is a welfare concern. Prior research suggests that exercise, especially during the developmental stage, can aid in minimizing bone fractures by strengthening muscles and increasing bone mass. Furthermore, nutrition plays an integral role in laying hen skeletal health. We investigated two interventions to prevent or reduce the negative effects observed on laying hen skeletal health: 1) environmental enrichment, which included the provision of multi-tier perches at various time points within the lifespan of laying hens and 2) nutritional enrichment, which involved supplementing the diet with boron. The first aim of this dissertation (described in Chapter 2) was to determine the effect of perch provision during the rearing phase on the activity and musculoskeletal health of pullets. Pullets (n=810) were either housed with or without multi-tier perches from 0 to 17 weeks of age (15 pens/treatment, 29 birds/pen). We expected pullets with perches to show improved musculoskeletal characteristics compared to pullets reared without perches. At 5, 11, and 17 weeks, birds were individually monitored for activity level over 3 consecutive days. At 11 and 17 weeks, 60 birds were euthanized for computed tomography (CT) scans to quantify tibiotarsal bone mineral density (BMD) and cross-sectional area (CSA). After CT scanning, birds were dissected for measurement of muscle size, tibiotarsal breaking strength, and tibiotarsal ash percentage. Novel markers of bone mineralization (bone-specific alkaline phosphatase [BALP] and pro-collagen type 1 n-terminal propeptide [P1NP]) were measured from serum samples of 60 birds/week. Results indicated that pullets reared with perches from 0-17 weeks of age exhibited increased levels of vertical activity, with no significant effect on overall activity level. Pullets with perches had greater total and cortical BMD at week 11, with increased cortical bone CSA and higher total and cortical BMD at week 17 compared to pullets without perches. At week 11, pullets with perches had heavier leg muscles, with heavier triceps, biceps, pectoralis major and minor, and leg muscles at week 17 than pullets without perches. At both weeks, pullets with perches had greater tibiotarsal breaking strengths, higher ash percentages, and greater concentrations of BALP and P1NP than pullets without perches. These results indicate that activity resulting from perching elicits a beneficial impact on measures of pullet musculoskeletal health at both 11 and 17 weeks of age.
The second objective (described in Chapter 3) was to determine whether there were enduring impacts of perch provision timing on the musculoskeletal health of laying hens. Pullets (n=812) were housed under different conditions (7 pens/treatment, 29 birds/pen) with either continuous access to multi-tier perches from 0 to 40 weeks of age (CP), no access to perches (NP), early access to perches during the rearing phase from 0 to 17 weeks of age (EP), or solely during the laying phase from 17 to 40 weeks of age (LP). We expected hens from the CP group to exhibit improved musculoskeletal health as a result of perch-related activity compared to hens from the NP group, with hens from the EP group having improved musculoskeletal health compared to hens from the LP group due to increased activity during the developmental stage. At weeks 24, 36, and 40 of age, birds were individually monitored for activity level over 3 consecutive days, and blood samples were collected from a separate set of 3 birds per pen to analyze serum concentrations of tartrate-resistant acid phosphatase 5b (TRACP-5b) and C-terminal telopeptide of type I collagen (CTX-I) as novel markers of bone demineralization. At 40 weeks of age, 3 birds per pen were euthanized for CT scans with further analysis including muscle weights, tibiotarsal breaking strength, and tibiotarsal ash percent. During week 24, hens from CP, EP, and LP pens had the highest overall activity compared to hens from NP pens, with no differences at week 36 or 40. During all weeks, hens from CP and LP pens had greater vertical and less horizontal activity compared to those from EP and NP pens. TRACP-5b and CTX-I concentrations did not differ at week 24 of age, with hens from CP pens having the lowest TRACP-5b and CTX-I concentrations compared to NP pens at 40 weeks of age. Total bone CSA did not differ between treatments, but CP had greater total BMD than NP with no differences between EP and LP pens. CP and LP hens had heavier biceps, pectoralis major, and leg muscle groups, as well as greater tibiotarsal breaking strengths than EP and NP pens. CP hens had higher tibiotarsal ash percentages compared to all other treatment groups. The results from this chapter indicate that the continuous provision of perches throughout the rearing and lay phase beneficially impacts activity level and measures of hen musculoskeletal health at 40 weeks of age, contributing to an overall improvement in laying hen welfare compared to no access to perches. Perch access during the early lay phase (17-40 weeks of age) had a positive impact on activity, muscle weight, and bone strength, but these benefits were not as great as those observed with continuous perch access. Perch access during the rearing phase (0-17 weeks of age) was associated with a decline in measures of bone demineralization, but did not have an overarching beneficial impact on other measures of hen musculoskeletal health or activity at 40 weeks of age, suggesting there was not a long-term benefit of perch access during the developmental stage.
The third objective (within Chapter 4) was to determine the influence of perch provision timing on laying hen behavior, specifically anxiety and fearfulness. While providing perches may enhance biological functioning and animal welfare, their effectiveness could be age-dependent. This chapter investigated the effects of early and late perch access on anxiety and fear in hens through attention bias (AB) and tonic immobility tests (TI). Pullets (n=728) were raised with or without multi-tier perches either continuously (CP; 0-37 weeks), during only the rearing phase (EP; 0-17 weeks), during only the laying phase (LP; 17-37 weeks), or not at all (NP; no perch access). We expected hens from the CP group to show responses consistent with reduced anxiety and fear compared to hens from the NP group, with intermediate responses from hens in the EP and LP groups. AB was conducted in weeks 21 and 37 (n=84 birds/week) and TI was performed in weeks 20, 25, and 37 (n=112/week). CP hens fed quicker in the AB test than EP, LP, and NP hens at weeks 21 and 37. CP and NP feeding latencies were stable, while EP and LP fed faster at week 37 compared to 21. CP had the shortest TI duration at week 20, while both CP and LP had the shortest TI durations in weeks 25 and 37. Hens from LP pens showed increased anxiety levels at week 21 of age, which they adapted to by week 37, indicating that adaptation to a new adult environment requires at least 16 weeks. Also, LP hens exhibited reduced fearfulness by 20 weeks of age compared to hens that lost their perch access (EP) or never had perch access (NP). At 25 and 37 weeks of age, LP hens showed similar fear levels as hens from CP pens, indicating that current perch access reduces fearfulness. Removing perches at 17 weeks of age (EP) increased fear at weeks 20 and 25 and anxiety at week 21, effects that disappeared by week 37 of age. Furthermore, birds from EP pens showed decreased anxiety at 37 weeks of age compared to NP birds, suggesting that perch access, even when removed at 17 weeks of age, is more beneficial to anxiousness at 37 weeks of age than not having access to perches at all. Our findings indicated that providing hens with multi-tier perches throughout their lifetime improved affective state by reducing anxiety and fearfulness, while no access to perches negatively impacted measures of emotion and affective state.
The last objective (described in Chapter 5) was to determine the effects of boron supplementation on pullet musculoskeletal health and performance parameters. Boron plays a role in the metabolism of calcium, which may help improve bone strength and prevent fracture. A total of 529 Hy-Line W-36 pullets were distributed across 24 pens and fed basal diets containing varying amounts of boron (C: (C: 0mg/kg; L: 50mg/kg; M: 100mg/kg; H: 150mg/kg) for 17 weeks. We expected pullets from the M group to show improved musculoskeletal health compared to the other treatment groups. Performance parameters (body weight, average daily weight gain/bird, and average daily feed intake/bird) were measured at weeks 4, 7, 10, 13, and 16, while all other measures were recorded at 11 and 17 weeks of age. Performance measures did not differ between treatment groups. Pectoralis major weights were higher in H pullets at 11 weeks of age, and we also observed higher pectoralis major, minor, and leg muscle weights in H pullets at 17 weeks of age. Pullets fed the H diet had larger cortical CSA than the other treatment groups at 11 weeks of age. At 17 weeks of age, both H and M groups had larger cortical CSA than L and C groups, but the M group had slightly smaller cortical CSA. Pullets fed the H diet had higher BMD values than other treatment groups at 11 weeks of age. At 17 weeks of age, pullets fed the H diet had the highest total BMD values compared to the other treatment groups, and cortical BMD increased with increasing boron inclusion. Pullets fed the H diet had the highest tibia ash percentages and concentrations of BALP and P1NP. Pullets fed the M and H diets had greater failure load and maximum bending moment than pullets fed the L or C diet at 11 weeks of age, with H pullets having greater stiffness values than other groups. At 17 weeks of age, pullets fed the H diet had greater failure load and maximum bending moment compared to all other treatment groups. Our results imply that providing boron within the diet at 150mg/kg improves musculoskeletal characteristics of Hy-Line W-36 pullets up to 17 weeks of age, without impacting performance parameters.
Recommended Citation
Anderson, Mallory, "Optimizing Laying Hen Behavior, Bone Health, and Welfare Through Environmental and Nutritional Enrichments" (2024). All Dissertations. 3595.
https://open.clemson.edu/all_dissertations/3595
Author ORCID Identifier
0000-0003-4030-3316