Improving Performance of Free-Range Laying Hens

Abstract

<p>Laying hens selected and bred for high performance in a controlled environment face various challenges when exposed to free-range housing systems. Gut impaction with grass, nutritional imbalances, and social stress such as feather pecking are some of the major challenges that the modern free-range egg industry in Australia is facing. The research subject to this thesis aims to improve the performance of commercial laying hens by comprehending the aforementioned challenges with the use of feed additives.</p><p> In this thesis, it was demonstrated that pasture consumption significantly (<i>P</i> < 0.05) reduced the digestibility of crude protein (CP), acid detergent fibre (ADF), neutral detergent fibre (NDF), insoluble arabinose and insoluble xylose. The digestibility of CP, ADF and NDF was significantly (<i>P</i> < 0.05) improved in hens fed a diet supplemented with multi enzymes (T2) or a diet supplemented with organic acid and essential oils (T3), compared to hens fed a control diet (T1). Similarly, hens fed the T2 diet had a greater digestibility (<i>P</i> < 0.05) of free oligosaccharides containing arabinose and xylose compared to hens fed T1 or T3 as discussed in Chapter 3. This higher digestibility of nutrients and non-starch polysaccharides can be linked to the heavier body weight of hens fed T2. In general, pasture consumption increased the body weight and egg weights of hens. However, non significant changes were observed on internal and external egg quality except a significant increase in yolk color colour score as a result of pasture consumption as discussed in Chapter 4.</p><p> The effect of pecking stones were tested in two commercial free range layer farms. On Farm A, using fixed sheds and flock sizes of 20,000 hens, access to pecking stones reduced (<i>P</i> = 0.001) hen mortality per week. Hens with access to pecking stones also had better wing feather conditions compared to hens of the control group (pecking stone × age, <i>P</i> = 0.002). These results provide evidence that access to pecking stones reduces feather loss and mortality. However, pecking stone consumption also caused hens to decrease large sized feed particles consumption and subsequently modified feed intake as discussed in Chapter 6.</p><p> The results of these experiments indicated that feed additives (dietary enzymes as well as freely available pecking stones) can be powerful tools to improve hen performance and welfare under free range conditions. In conclusion, the negative effects associated gut impaction, feather pecking in free-range hens' performance, health and welfare can be reduced with feed additives. However, further research is warranted to establish the role of various feed additives in freerange layer diets on commercial farms.</p>