Response of prime lambs to dietary omega-3-rich oils: impact on meat quality

Le, Hung Van (2019) Response of prime lambs to dietary omega-3-rich oils: impact on meat quality. PhD thesis, James Cook University.

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This thesis investigated the responses of confined and grazing weaner prime lambs to dietary omega-3 (n-3) polyunsaturated fatty acids (PUFA)-rich oil supplementation with regards to animal performance, carcass characteristics, feed conversion efficiency, feed costs and fatty acid profiles of longissimus dorsi muscle, liver, kidney and heart. The primary objectives were to systematically investigate and collect scientific evidence on the nutritional enhancement of health beneficial omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA) content of confined and grazing weaner lambs supplemented with or without canola, rice bran, flaxseed, rumen-protected and safflower oil-infused pellets and to evaluate the cost of producing premium quality lamb relative to liveweight gain.

Two on-farm experiments representing both indoor lot-fed and outdoor grazing production systems, were conducted to achieve the overarching objectives of the thesis. In Experiment 1 (indoor confined production system), seventy-two, 6 months old, White Suffolk x Corriedale first-cross weaner prime lambs were randomly assigned to six treatment groups: (1) Control: Lucerne hay only; wheat-based pellets infused with 50 ml/kg dry matter (DM) of oil from (2) rice bran (RBO); (3) canola (CO); (4) rumen-protected (RPO), (5) flaxseed (FSO) and (6) safflower (SO) dietary sources in a completely randomized experimental design. All lambs had ad libitum access to lucerne hay and clean fresh water and supplemented lambs were fed 1 kg of pellet/head/day for 10 weeks after three weeks of adaptation. Data on daily dry matter feed intake, weekly liveweight and body conformation measurements were recorded. At the end of the feeding trial, all lambs were humanely sacrificed at a commercial abattoir, carcass characteristics evaluated and samples of the longissimus dorsi muscle, heart, liver and kidney were taken. Fatty acid profiles of sampled tissues and organs were analysed by gas chromatography and gas chromatography mass spectrometry. All data were analysed in SAS utilising both general linear (PROC GLM) and mixed model (PROC MIXED) procedures with repeated measures that adjusted for fixed, random and interaction effects.

Supplementation of confined lambs resulted in improvement of dry matter feed intakes, lamb performance and carcass characteristics. RBO and CO treatments had lower feed costs and similar indices of lamb performance, carcass characteristics and over the hooks trade (OTH) incomes compared with other treatment groups. Eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) contents of the longissimus dorsi muscle of lambs supplemented with CO, FSO, SO and RPO were above the 30 mg per standard serve threshold for omega-3 "source" claim under the Foods Standard Australia and New Zealand (FSANZ) guidelines. The ≥C₂₀ n-3 LC-PUFA contents of the longissimus dorsi muscle did not differ among supplemented confined lambs. However, variation in fatty acid contents among and between different organs and tissues was observed and the liver and kidney could be labelled as 'good source' (above 60 mg per standard serve threshold) of n-3 LC-PUFA.

From the results in Experiment 1, the following research questions needed to be answered:

1. Given that CO and RBO were the cheapest supplements, was there any added advantage of supplementing lambs grazing lucerne and cocksfoot pastures with CO and RBO oil-based pellets in enhancing EPA+DHA contents in the muscle tissue and organs?

2. Could animal performance, carcass traits, feed conversion efficiency and OTH trade incomes of grazing lambs be improved by additional supplementation with RBO and CO?

Experiment 2 was designed to answer these questions. Therefore, forty-eight White Suffolk x Corriedale first-cross weaners were randomly allocated to one of the following four treatments in a split-plot experimental design: (1) Cocksfoot cv. porto (CFP) or lucerne pastures only (control); (2) CFP or lucerne pastures supplemented with pellets infused with oil from (3) canola (CO); (4) rice bran (RBO) or no oil pellets (NOP). Lucerne and CFP pastures were considered as the main plot effects and pellet supplementation as a sub-plot effect in a feeding trial that lasted for nine weeks.

The findings demonstrated that animal performance and carcass characteristics of lucerne grazing lambs were not affected by pellet supplementation. However, lambs grazing CFP and supplemented with CO had lower feed conversion efficiency (FCE) and higher OTH trade income than CFP only grazing lambs. Lucerne grazing lambs had higher average daily gain, hot carcass weight and OTH trade income than CFP grazing lambs. The addition of pellets to the diet of grazing lambs generally decreased α-linolenic acid (ALA, 18:3n-3) and n-3 LC-PUFA contents and increased the n-6/n-3 ratio in the longissimus dorsi muscle. Different types of pastures and pellet supplementation affected the fatty acid profiles of organs and tissues of grazing lambs. For instance, ALA, 20:3n-6, EPA, PUFA, n-3 PUFA, and n-6 PUFA contents in longissimus dorsi muscle of lucerne grazing lambs were higher than in CFP grazing lambs. Variation in fatty acid contents in different organs of grazing lambs indicated that the liver and kidney can be used as 'good sources' of n-3 LC-PUFA. Cocksfoot cv. porto produced premium quality, healthy lambs with high contents of ALA and n-3 LC-PUFA.

Taken together, dry matter feed intake, animal performance, carcass characteristics and fatty acid profiles of confined lambs were improved by supplementation with PUFA-rich, oil-infused pellets. RBO and CO can be used to improve n-3 LC-PUFA contents in the longissimus dorsi muscle of confined lambs at low feed costs, with comparable indices of animal performance and carcass characteristics with other sources of PUFA. Supplementation of CFP grazing lambs with CO can be used as a strategic nutrition tool for increasing OTH income with low FCE. CFP also demonstrated the potential for producing premium quality, healthy lambs.

Recommended future studies should focus on:

1) Whole farm production cost-benefit analysis;

2) Marketing omega-3 labelled lamb products;

3) Investigating potential new pasture varieties for improving n-3 LC-PUFA content of grazing lambs; and

4) Better understanding of the rumen biohydrogenation pathways in grazing lambs.

Item ID: 63741
Item Type: Thesis (PhD)
Keywords: lamb; n-3 LC-PUFA; muscle; liver; heart; kidney; rice bran; canola; cocksfoot; lucerne; omega 3; meat quality
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Copyright Information: Copyright © 2019 Hung Van Le.
Additional Information:

Three publications arising from this thesis are stored in ResearchOnline@JCU, at the time of processing. Please see the Related URLs field. The publications are:

Chapter 3: Le, Hung V., Nguyen, Quang V., Nguyen, Don V., Malau-Aduli, Bunmi S., Nichols, Peter D., and Malau-Aduli, Aduli E.O. (2018) Nutritional supplements fortified with oils from canola, flaxseed, safflower and rice bran enhance feedlot performance and carcass characteristics of Australian prime lambs. Animals, 8 (12). 231.

Chapter 4: Le, Hung Van, Nguyen, Don Viet, Nguyen, Quang Vu, Malau-Aduli, Bunmi Sherifat, Nichols, Peter David, and Malau-Aduli, Aduli Enoch Othniel (2019) Fatty acid profiles of muscle, liver, heart and kidney of Australian prime lambs fed different polyunsaturated fatty acids enriched pellets in a feedlot system. Scientific Reports, 9. 1238.

Chapter 6: Le, Hung V., Nguyen, Quang V., Nguyen, Don V., Otto, John R., Malau-Aduli, Bunmi S., Nichols, Peter D., and Malau-Aduli, Aduli E.O. (2018) Enhanced omega-3 polyunsaturated fatty acid contents in muscle and edible organs of Australian prime lambs grazing lucerne and cocksfoot pastures. Nutrients, 10 (12). 1985.

Date Deposited: 10 Jul 2020 03:06
FoR Codes: 07 AGRICULTURAL AND VETERINARY SCIENCES > 0702 Animal Production > 070204 Animal Nutrition @ 100%
SEO Codes: 83 ANIMAL PRODUCTION AND ANIMAL PRIMARY PRODUCTS > 8303 Livestock Raising > 830310 Sheep - Meat @ 100%
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