Mini Singh

Relationships between range access as monitored by radio frequency identification technology, fearfulness, and plumage damage in free-range laying hens

Severe feather-pecking (SFP), a particularly injurious behaviour in laying hens (Gallus gallus domesticus), is thought to be negatively correlated with range use in free-range systems. In turn, range use is thought to be inversely associated with fearfulness, where fearful birds may be less likely to venture outside. However, very few experiments have investigated the proposed association between range use and fearfulness. This experiment investigated associations between range use (time spent outside), fearfulness, plumage damage, and BW. Two pens of 50 ISA Brown laying hens (n=100) were fitted with radio frequency identification (RFID) transponders (contained within silicone leg rings) at 26 weeks of age. Data were then collected over 13 days. A total of 95% of birds accessed the outdoor run more than once per day. Birds spent an average duration of 6.1 h outside each day over 11 visits per bird per day (51.5 min per visit). The top 15 and bottom 15 range users (n=30), as determined by the total time spent on the range over 13 days, were selected for study. These birds were tonic immobility (TI) tested at the end of the trial and were feather-scored and weighed after TI testing. Birds with longer TI durations spent less time outside (P=0.01). Plumage damage was not associated with range use (P=0.68). The small group sizes used in this experiment may have been conducive to the high numbers of birds utilising the outdoor range area. The RFID technology collected a large amount of data on range access in the tagged birds, and provides a potential means for quantitatively assessing range access in laying hens. The present findings indicate a negative association between fearfulness and range use. However, the proposed negative association between plumage damage and range use was not supported. The relationships between range use, fearfulness, and SFP warrant further research.

Range use and pasture consumption in free-range poultry production

The recent increase in free-range meat and egg production and consumption has led to extensive investigation in this area and has revealed that the level of animal performance achieved in such systems is low compared with that achieved in conventional production systems. In Australia, this difference has been attributed either to the absence of in- feed antibiotics or to range access, which may result in exposure to detrimental climatic conditions, predators, disease, welfare challenges and nutrient dilution. Moreover, although poultry in free-range systems have ready access to outside runs, not all birds utilise them optimally. Pasture consumption results in dilution of energy and protein intake and may cause impaction and dietary electrolyte imbalance. This paper provides an overview of these issues to provide a conceptual framework for further study in this area.

Effects of exogenous xylanase on performance, nutrient digestibility, volatile fatty acid production and digestive tract thermal profiles of broilers fed on wheat- or maize-based diet

Abstract 1. A previous experiment reported that caecal temperature was negatively correlated with d 49 feed conversion ratio (FCR). This increased temperature in the caeca may indicate a prebiotic effect. An experiment was designed to investigate whether caecal temperature was affected in diets based on maize and whether other portions of the tract were affected. 2. A total of 25 Ross 308-d-old male broilers were allocated to each of 8 replicate pens per treatment. Treatments followed a 2 × 3 factorial design: two diets based on wheat or maize and three levels of enzyme addition, 0, 16 000 or 32 000 BXU/kg. Growth performance was assessed between d 1 and 49. Digestibility measurements were taken at d 28 and 49. On d 49, the excised small and large intestine of each bird was thermally imaged, weighed and volatile fatty acids (VFA) measured. 3. On d 28 and d 49, birds on the maize diets had higher feed intake and weight gain than those offered wheat diets. Additionally, on d 28, birds that received the maize diet had lower FCR than those offered the wheat diet. Enzyme improved FCR at d 49, independently of cereal. On d 28, enzyme improved the coefficient of apparent ileal DM digestibility and the coefficient of apparent ileal nitrogen digestibility. Enzyme only improved apparent ileal digestible energy in wheat-based diets (interactive term). On d 49, all digestibility parameters were improved by enzyme. Enzyme increased gizzard weight in maize-fed birds and the caeca of those fed wheat were heavier. The higher enzyme dose decreased duodenal temperature. In summary of VFA data, wheat-based diets produced more total VFAs and the total amount also increased with enzyme. 4. It appears from this study that there is equal potential in both wheat and maize diets for xylanase to improve performance of broilers probably through different mechanisms.

Comparisons of management practices and farm design on Australian commercial layer and meat chicken farms: Cage, barn and free range

There are few published studies describing the unique management practices, farm design and housing characteristics of commercial meat chicken and layer farms in Australia. In particular, there has been a large expansion of free range poultry production in Australia in recent years, but limited information about this enterprise exists. This study aimed to describe features of Australian commercial chicken farms, with particular interest in free range farms, by conducting on-farm interviews of 25 free range layer farms, nine cage layer farms, nine barn layer farms, six free range meat chicken farms and 15 barn meat chicken farms in the Sydney basin bioregion and South East Queensland. Comparisons between the different enterprises (cage, barn and free range) were explored, including stocking densities, depopulation procedures, environmental control methods and sources of information for farmers. Additional information collected for free range farms include range size, range characteristics and range access. The median number of chickens per shed was greatest in free range meat chicken farms (31,058), followed by barn meat chicken (20,817), free range layer (10,713), barn layer (9,300) and cage layer farms (9,000). Sheds had cooling pads and tunnel ventilation in just over half of both barn and free range meat chicken farms (53%, n = 8) and was least common in free range layer farms (16%, n = 4). Range access in free range meat chicken farms was from sunrise to dark in the majority (93%, n = 14) of free range meat chicken farms. Over half of free range layer farms (56%, n = 14) granted range access at a set time each morning; most commonly between 9:00 to 10.00am (86%, n = 12), and chickens were placed back inside sheds when it was dusk.

Demographics and practices of semi-intensive free-range farming systems in Australia with an outdoor stocking density of ≤1500 hens/hectare

Baseline information on demographics and practices on semi-intensive free-range egg farms with an outdoor stocking density of ≤1500 hens/hectare in Australia is presented. Free-range egg production is changing the structure of the egg industry in Australia and a broad variety and tiers of free-range systems have emerged due to lack of concrete legislative standards on outdoor stocking densities in the past. Information was extracted from a pre-existing online free-range poultry survey dataset, consisting of a total of 79 questions related to nutrition, pasture management, welfare and health, animal housing, environmental impact and economics. Forty-one free-range egg farms, with an outdoor stocking density of ≤1500 hens/hectare, were identified in the dataset from all major Australian states. Two types of semi-intensive free-range housing systems were documented: mobile (modified caravan/trailer) housing (56%), and fixed sheds (44%). Seventy-two percent of respondents reported >75% of the hens in the flock used the outdoor range. All respondents reported ingestion of range components by hens in the form of vegetation, insects, stones and grit. Up to 10% mortality was reported by 40% respondents with predation (34%), cannibalism (29%), heat stress (24%) and grass impaction (19.5%) as major causes. Biosecurity on farms was sub-optimal with 8 of the 10 actions implemented by <50% respondents. Customer demand, consumer sentiment and welfare were the major factors for farmers moving into free-range egg production. This study resulted in identification of current practices and key challenges on semi-intensive free-range egg farms. Applied research and communication of results to farmers is highly recommended to ensure optimum health and welfare of free-range laying hens and sustained egg production.

Influence of chick hatch time and access to feed on broiler muscle development

The effect of hatch time and the timing of access to feed on growth rate and breast muscle development was assessed in Ross 308 broiler chickens. Chicks were removed from the incubator upon hatching, and classified as early (EH), midterm (MH), or late (LH) hatchers, based on the duration of their incubation. Feed and water were available either immediately at hatch, or 24 h after the conclusion of the hatch period. Hatchling body weight was uniform regardless of hatch time. Subsequently, bodyweight was increased in EH compared to LH birds following immediate access to feed, until 7 d in female, and 14 d in male birds. Relative breast weight was increased until 28 d in birds with immediate access to feed, and also EH and MH birds regardless of access to feed. Pectoralis major muscle morphology and expression of the myogenic regulatory factors myogenic determination factor 1 (MYOD1) and myogenin, and the proteoglycans syndecan-4, glypican-1, and decorin were measured. Myogenin and glypican-1 stimulate satellite cell (SC) differentiation. Glypican-1 expression was unaffected by treatment. A late increase in myogenin expression was observed in MH birds with delayed access to feed, and all LH birds. Syndecan-4 and MYOD1, expressed in proliferating SC, and decorin, which stimulates satellite cell proliferation and differentiation, were variably upregulated in the first wk posthatch in the same birds. These data suggest SC were activated and proliferating, but had reduced differentiation in later hatching and feed deprived birds. Conversely, EH birds with immediate access to feed had maximal myofiber width at 7 d, while fiber width was increased in birds with immediate access to feed compared to those with delayed access to feed through 40 d of age. These results demonstrate that delaying chick access to feed for 24 h upon removal from the incubator will impair muscle growth. Additionally, hatch time influences muscle development, with accelerated muscle growth in EH and MH, compared to LH birds, irrespective of access to feed.

Comparative transcriptome analyses reveal conserved and distinct mechanisms in ovine and bovine lactation

A combined analysis of a bovine and ovine mammary gland transcriptome from two similarly designed microarray experiments suggested a strong positive association between the differentially expressed genes (DEGs) implying that major pathways regulating the lactation process were evolutionarily conserved within the two species. Some distinct pathways identified indicate the physiological differences underlying the species. Novel techniques were established for the combined analysis of the transcriptomes of different species or heterogeneous platforms for comparative gene expression analysis allowing for greater experimental power to detect conserved pathways. Conserved DEGs were mainly related to lipid metabolism, amino acid synthesis, cell proliferation, signaling and immune systems indicating functional processes involved in the regulation of lactation including milk synthesis and lactation persistency. There were no functionally annotated DEGs that show antagonistic expression between sheep and cattle suggesting that the lactation process is essentially the same in the two species. DEGs that were found exclusively in sheep were mostly associated with gland morphogenesis while DEGs exclusively expressed in cattle, indicated that certain immune response and milk composition mechanisms were different in the bovine as compared to sheep. The conserved processes across the two species suggest the use of the ovine as a suitable model for lactation studies, considering the challenges and expense of conducting lactation physiology and genomics studies within the cow.

Biosecurity practices on Australian commercial layer and meat chicken farms: Performance and perceptions of farmers

This paper describes the level of adoption of biosecurity practices performed on Australian commercial chicken meat and layer farms and farmer-perceived importance of these practices. On-farm interviews were conducted on 25 free range layer farms, nine cage layer farms, nine barn layer farms, six free range meat chicken farms and 15 barn meat chicken farms in the Sydney basin bioregion and South East Queensland. There was a high level of treatment of drinking water across all farm types; town water was the most common source. In general, meat chicken farms had a higher level of adoption of biosecurity practices than layer farms. Cage layer farms had the shortest median distance between sheds (7.75m) and between sheds and waterbodies (30m). Equipment sharing between sheds was performed on 43% of free range meat chicken farms compared to 92% of free range layer farms. There was little disinfection of this shared equipment across all farm types. Footbaths and visitor recording books were used by the majority of farms for all farm types except cage layer farms (25%). Wild birds in sheds were most commonly reported in free range meat chicken farms (73%). Dogs and cats were kept across all farm types, from 56% of barn layer farms to 89% of cage layer farms, and they had access to the sheds in the majority (67%) of cage layer farms and on the range in some free range layer farms (44%). Most biosecurity practices were rated on average as ‘very important’ by farmers. A logistic regression analysis revealed that for most biosecurity practices, performing a practice was significantly associated with higher perceived farmer importance of that biosecurity practice. These findings help identify farm types and certain biosecurity practices with low adoption levels. This information can aid decision-making on efforts used to improve adoption levels.

Low- and High-Pathogenic Avian Influenza H5 and H7 Spread Risk Assessment Within and Between Australian Commercial Chicken Farms

This study quantified and compared the probability of avian influenza (AI) spread within and between Australian commercial chicken farms via specified spread pathways using scenario tree mathematical modeling. Input values for the models were sourced from scientific literature, expert opinion, and a farm survey conducted during 2015 and 2016 on Australian commercial chicken farms located in New South Wales (NSW) and Queensland. Outputs from the models indicate that the probability of no establishment of infection in a shed is the most likely end-point after exposure and infection of low-pathogenic avian influenza (LPAI) in one chicken for all farm types (non-free range meat chicken, free range meat chicken, cage layer, barn layer, and free range layer farms). If LPAI infection is established in a shed, LPAI is more likely to spread to other sheds and beyond the index farm due to a relatively low probability of detection and reporting during LPAI infection compared to high-pathogenic avian influenza (HPAI) infection. Among farm types, the median probability for HPAI spread between sheds and between farms is higher for layer farms (0.0019, 0.0016, and 0.0031 for cage, barn, and free range layer, respectively) than meat chicken farms (0.00025 and 0.00043 for barn and free range meat chicken, respectively) due to a higher probability of mutation in layer birds, which relates to their longer production cycle. The pathway of LPAI spread between sheds with the highest average median probability was spread via equipment (0.015; 5–95%, 0.0058–0.036) and for HPAI spread between farms, the pathway with the highest average median probability was spread via egg trays (3.70 × 10−5; 5–95%, 1.47 × 10−6–0.00034). As the spread model did not explicitly consider volume and frequency of the spread pathways, these results provide a comparison of spread probabilities per pathway. These findings highlight the importance of performing biosecurity practices to limit spread of the AI virus. The models can be updated as new information on the mechanisms of the AI virus and on the volume and frequency of movements shed-to-shed and of movements between commercial chicken farms becomes available.

Use of n-alkanes for determination of Kikuyu grass (Pennisetum clandestinum) intake in free-range broilers

N-alkanes, long-chained saturated hydrocarbons occurring in plant cuticles, were used for estimating grass intake in fast-growing, free-range broilers. A total of 1440 as hatched mixed sex Cobb 500 broilers were equally divided between one of four experimental treatments in a 2 by 2 factorial arrangement involving conventional (barn) or free-range (barn and range access) production systems and diets (crude protein: 21%, metabolisable energy: 13 MJ/K) with or without in-feed antibiotic (Zinc Bacitracin: Albac® G 150 antibiotic feed premix, Pfizer Australia Pty Ltd, Sydney, NSW, Australia). Day-old chicks were randomly allocated to 48 pens (12 replicates/treatment) with 30 birds in each pen. Chicks were assigned to treatment diets on Day 1 while free-range access was available to birds from Day 21 onwards. Alkane concentrations in litter were measured and compared with alkane profiles of the intake components (grass, diet pellets and woodchip). Correction for incomplete recovery followed by estimation using a non-negative least square procedure resulted in calculation of total grass intake from the range area. Kikuyu grass consumption was estimated to be 13.5–14.7% of total ‘as-fed’ intake, equating to 6.34–6.78 g of grass per bird per hour of range access in this study. Taking into account grass consumption, this resulted in a significant increase in feed intake by 8.7–8.9% (P < 0.01) and feed conversion ratio from 2.30 to 2.54 points (P < 0.01). It can be concluded that broilers reared under free-range conditions eat a substantial quantity of grass. However, the nutrient profile of grass is not complementary to the formulated ration and its consumption is likely to lead to an array of nutritional changes for the bird, thus affecting performance.