Omega-3 (n3) fatty acid supplemented diets reduces bone breakage and increases bone strength in free range laying hens

Introduction. There are 29 million laying hens in the UK, producing 8.8 billion eggs. Our recent estimates of keel bone breakage rates in free range systems have shown that up to 86% suffer bone breakage. Skeletal health in laying hens is therefore a major welfare and economic problem, and seriously damages the public perception of egg production. This problem is made all the more urgent by the imminent ban on cage systems requiring that 18 million birds are "transferred" to non-cage systems, with a potential “epidemic” of broken bones. Current interest in omega-3 (n3) polyunsaturated fatty acid (PUFA) supplementation in human diets results from evidence that many diseases prevalent in Western societies are due to excessive dietary n6 and a deficit in n3. Similarly, farmed laying hens are exposed to unnaturally low levels of n3. PUFAs are the immediate precursors to a number of inflammatory mediators such as prostaglandins (PG), with n3s generating mediators which are less active than those from n6. Therefore it is likely that promoting a natural balance of n3 and n6 in the food chain would improve human and animal health. Bone fragility and breakage is a problem for both humans and farmed hens, and there is evidence from human and animal studies that a balanced n3/n6 dietary intake reduces signs of osteoporosis, probably by modulating prostaglandin activities. Therefore, there is potential to reduce rates of bone breakage in laying hens by dietary supplementation with n3 PUFA. Materials and Methods. As part of a DEFRA study in collaboration with Noble Foods, we compared 6 commercial egg production flocks fed a standard diet high in 18:2n6 linoleic acid (LA; n6:n3=8), with 6 flocks fed a “Columbus” diet supplemented with 18:3n3 alpha linolenic acid (ALA; n6:n3=0.8) from flaxseed. Assessments were made at 30 weeks of age, 50 weeks and at end of lay (70 weeks). Keel bone breakage was evaluated by dissection of 10 birds/flock/time point. Dual energy X-ray absorptiometry was performed on the humerus collected at dissection to determine bone mineral density (BMD). Biomechanical tests were performed on the tibia using an Instron Materials Testing apparatus, measuring ultimate stress, Young’s modulus and energy to break. The humeri were pulverised and extracted to separate soluble metabolic mediators from the organic and inorganic bone fraction. Alkaline phosphatase (AP), a marker of osteoblastic bone formation, tartrate resistant acid phosphatase (TRAP), a marker of osteoclastic bone resorption were measured colorimetrically, and matrix metalloproteinase-2 (MMP-2), a marker of collagen turnover, were quantified by zymography from the soluble bone fraction. Mature pyrrolic collagen cross link (inverse correlate of bone turnover) was measured in the insoluble bone fraction. One way ANOVAs were used to confirm treatment effects, and unpaired two tailed t tests (with Welch’s correction where variances are unequal) were performed to compare groups. Results. Bone breakage rates in standard free range systems were 56.2% (±7.2) at 50wks and 62% (±5.6) at 70wks. Rates were significantly lower in the n3 flocks (Fig 1) at both 50wks (21.7 ±3.1, p