Tanya Kilminster

Does the fat tailed Damara ovine breed have a distinct lipid metabolism leading to a high concentration of branched chain fatty acids in tissues

Fat tailed sheep breeds are known for their adaptation to nutritional stress, among other harsh production conditions. Damara sheep, native to Southern Africa, have recently been exported to other areas of the world, particularly Australia, aiming to produce lamb in semi-arid regions. Damaras have a unique hanging fat tail, a fat depot able to be mobilized under nutritional stress. In this article we perform an in-depth characterization of the fatty acid profiles of the fat tail in underfed and control Damara rams. Profiles were very similar between experimental groups, with the exception of palmitic acid (16:0) that was lower (P = 0.014) in underfed animals. However, the most striking result was the very high proportions of non-terminal branched chain fatty acids found in the fat tail adipose tissue, as well as the gastrocnemius muscle of Damara rams. The muscle of Dorper and Merino rams used in the same experiment did not present non-terminal branched chain fatty acids, suggesting that Damara rams have a unique lipid metabolism. Herein, we interpret this trait relating it to a higher ability of Damara sheep to digest fibrous fodder and to putative differences in the propionate metabolism by comparison to other sheep breeds.

Influence of feed restriction on the wool proteome: A combined iTRAQ and fiber structural study

UNLABELLED Seasonal weight loss is the main limitation to animal production worldwide, significantly affecting the productivity of milk, meat and wool farms, particularly in drought-prone areas of the world where most of the large-scale wool production farms are located. Although the effect of nutritional status on wool quality parameters has been extensively studied, little is known on how it affects wool protein composition. Here, a proteomic approach has been applied to study changes in fiber structure and protein composition in wool from merino sheep subjected to experimentally induced weight loss. Results indicate that there is a significant reduction in the fiber diameter of wool from the animals on a restricted diet over a 42-day period. At the same time, significant increases in the expression of the high sulfur protein KAP13.1 and proteins from the high glycine-tyrosine protein KAP6 family in the wools from the animals on the restricted diet were also detected. Such findings have strong implications for the wool industry that favors finer wool. BIOLOGICAL SIGNIFICANCE Seasonal weight loss caused by poor pasture availability has strong effects on wool productivity parameters and quality traits. In this work we determine that experimentally induced weight loss causes a decrease in fiber diameter associated with an increase in the level of high sulfur protein KAP13.1 and proteins from the high glycine-tyrosine protein KAP6 family. The implication of this is that decreasing the fiber diameter of the wool by this process could result in a fiber reduced prickle but with reduced wearability and appearance retention.

The Effect of Weight Loss on the Muscle Proteome in the Damara, Dorper and Australian Merino Ovine Breeds.

Seasonal Weight Loss (SWL) is an important constraint, limiting animal production in the Tropics and the Mediterranean. As a result, the study of physiological and biochemical mechanisms by which domestic animal breeds respond to SWL is important to those interested in animal breeding and the improvement thereof. To that end, the study of the proteome has been instrumental in gathering important information on physiological mechanisms, including those underlying SWL. In spite of that, little information is available concerning physiological mechanisms of SWL in production animals. The objective of this study was to determine differential protein expression in the muscle of three different breeds of sheep, the Australian Merino, the Dorper and the Damara, each showing different levels of tolerance to weight loss (low, medium and high, respectively). Per breed, two experimental groups were established, one labeled “Growth” and the other labeled “Restricted.” After forty-two days of dietary treatment, all animals were euthanized. Muscle samples were then taken. Total protein was extracted from the muscle, then quantified and two-dimensional gel electrophoresis were conducted using 24 cm pH 3–10 immobiline dry strips and colloidal coomassie staining. Gels were analyzed using Samespots® software and spots of interest were in-gel digested with trypsin. The isolated proteins were identified using MALDI-TOF/TOF. Results indicated relevant differences between breeds; several proteins are suggested as putative biomarkers of tolerance to weight loss: Desmin, Troponin T, Phosphoglucomutase and the Histidine Triad nucleotide-binding protein 1. This information is of relevance to and of possible use in selection programs aiming towards ruminant animal production in regions prone to droughts and weight loss.

Fatty acid composition of the ovine longissimus dorsi muscle: Effect of feed restriction in three breeds of different origin

BACKGROUND Muscle fatty acid profile reflects the body condition of animals and has a noticeable effect on meat quality. Herein, longissimus dorsi muscle of three different sheep breeds, Damara (a fat-tailed breed), Dorper and Australian Merino sheep, was analysed for fatty acid composition. The three breeds were subjected to two distinctive feeding levels (ad libitum and restricted feeding) over 42 days. RESULTS The Damara sheep revealed several differences compared to the other two breeds, namely a higher concentration of polyunsaturated fatty acids, which can be related to being a fat-tailed breed. Even in restricted feeding conditions, this breed revealed the highest levels compared to Merino and Dorper sheep respectively, of linoleic acid (+31% and +28%), linolenic acid (+97% and +51%), eicosapentaenoic acid (EPA) (+65% and +37%), docosapentanenoic acid (DPA) (+31% Merino) and dodosahexanenoic acid (DHA) (+63% and +77%). EPA, DPA and DHA are three omega-3 fatty acids, with described beneficial characteristics. CONCLUSION With this work we show other qualities (higher levels of the omega-3 fatty acids, EPA, DPA and DHA) of Damara meat that might present this breed as an interesting alternative for animal production in semi-arid climates.

The hepatic and skeletal muscle ovine metabolomes as affected by weight loss: A study in three sheep breeds using NMR-metabolomics

Sheep are a valuable resource for meat and wool production. During the dry summer, pastures are scarce and animals face Seasonal Weight Loss (SWL), which decreases production yields. The study of breeds tolerant to SWL is important to understand the physiological mechanisms of tolerance to nutritional scarcity, and define breeding strategies. Merino, Damara and Dorper sheep breeds have been described as having different levels of tolerance to SWL. In this work, we assess their liver and muscle metabolomes, and compare the responses to feed restriction. Ram lambs from each breed were divided into growth and feed restricted groups, over 42 days. Tissue metabolomes were assessed by 1H-NMR. The Dorper restricted group showed few changes in both tissues, suggesting higher tolerance to nutritional scarcity. The Merinos exhibited more differences between treatment groups. Major differences were related to fat and protein mobilization, and antioxidant activity. Between the Damara groups, the main differences were observed in amino acid composition in muscle and in energy-related pathways in the liver. Integration of present results and previous data on the same animals support the hypothesis that, Dorper and Damara breeds are more tolerant to SWL conditions and thus, more suitable breeds for harsh environmental conditions.

Gene expression of regulatory enzymes involved in the intermediate metabolism of sheep subjected to feed restriction

The effect of feed restriction on gene expression of regulatory enzymes of intermediary metabolism was studied in two sheep breeds (Australian Merino and Dorper) subjected to two nutritional treatments: feed restriction (85% of daily maintenance requirements) and control (ad libitum feeding), during 42 days. The experimental animals (ram lambs) were divided into four groups, n = 5 (Australian Merino control (MC), Australian Merino Restriction (MR), Dorper control (DC) and Dorper Restriction (DR)). After the trial, animals were sacrificed and samples were taken from liver tissue to quantify glucose levels and gene expression of relevant intermediary metabolism enzymes (phosphofructokinase (PFK), pyruvate kinase (PK), phosphoenolpyruvate carboxykinase, fructose 1,6-bisphosphatase, glucose-6-phosphatase, glycogen synthase (GS), fatty acid synthase (FAS), glutamate dehydrogenase (GDH) and carbamoyl phosphate synthase (CPS)) through real-time PCR. During the experimental period, the MR animals lost 12.6% in BW compared with 5.3% lost by the Dorper lambs. MC and DC rams gained, respectively, 8.8% and 14% during the same period. Within the Dorper breed, restricted feed animals revealed a significant decrease over controls in the transcription of PFK (1.95-fold) and PK (2.26-fold), both glycolytic enzymes. The gluconeogenesis showed no change in the feed restricted animals of both breeds. DR feed group presented a significant decrease over the homologous Merino sheep group on GS. In both experimental breeds, FAS mRNA expression was decreased in restricted feed groups. GDH expression was decreased only in the DR animals (1.84-fold) indicating a reduced catabolism of amino acids in these animals. Finally, CPS was significantly (P < 0.05) higher in the Dorper sheep, indicating a facilitated urea synthesis in this breed. These results indicate a better adaptation of metabolic intermediate regulatory enzymes and hepatic glucose production of Dorper sheep to feed restriction concurring with the BW results in the experimental groups.

The sheep (Ovis aries) muscle proteome: Decoding the mechanisms of tolerance to Seasonal Weight Loss using label-free proteomics

Seasonal Weight Loss (SWL) is one of the most pressing issues in animal production in the tropics and Mediterranean. This work aims to characterize muscle proteome changes as a consequence of SWL in meat producing sheep, using a label-free proteomics approach. We compare three breeds: the Australian Merino (SWL susceptible), the Damara (SWL tolerant) and the Dorper (SWL intermediate tolerance). We identified 668 proteins of the sheep proteome, 95 with differential regulation. Also we observe that the more vulnerable to SWL a breed is, the more differential abundance proteins we find. Protein binding was the most frequently altered molecular function identified. We suggest 6 putative markers for restricted nutritional conditions independently of breed: ferritin heavy-chain; immunoglobulin V lambda chain; transgelin; fatty acid synthase; glutathione S-transferase A2; dihydrodiol dehydrogenase 3-like. Moreover, we suggest as related to SWL tolerance: S100-A10 Serpin A3-5-like and Catalase, subject however to necessary validation assays. The identification of SWL-tolerance related proteins using proteomics will lead to increased stock productivity of relevant interest to animal production, particularly if identified at the muscle level, the tissue of economic importance in meat production. BIOLOGICAL SIGNIFICANCE Seasonal Weight Loss (SWL) is the most pressing issue in animal production in the tropics and the Mediterranean. To counter SWL, farmers often use animal breeds that have a natural ability to withstand pasture scarcity. Here we study the sheep muscle proteome at the muscle level, the tissue of economic importance in meat production. Furthermore, the identification of proteins that change their abundance in response to SWL using proteomics can contribute to increased stock productivity of relevant interest to animal production. We identified 668 proteins of the sheep proteome. We demonstrate that the following proteins are affected by restricted nutritional conditions: ferritin heavy chain; immunoglobulin V lambda chain; transgelin; fatty acid synthase; glutathione S-transferase A2; dihydrodiol dehydrogenase 3-like. Furthermore, S100-A10, Serpin A3-5-like and Catalase are proteins that changed their abundance in response to SWL. Nevertheless, it is important to highlight that Catalase values for the merino breed were close to significance and therefore catalase validation is of utmost importance.

The fat-tail of Damara sheep: an assessment of mineral content as influenced by weight loss

Seasonal weight loss is the major constraint to animal production in the tropics. To counter seasonal weight loss, the use of breeds better adapted to it is of major importance. Damara sheep are an important breed in tropical animal production, as they are not only able to tolerate seasonal weight loss, but also have a characteristic fat-tail adipose tissue, often discarded, but that may be of interest to the food industry. The objective of this work is to determine the effect of weight loss on mineral profiles (zinc, manganese, iron, potassium, sodium, magnesium and calcium) in the fat-tail of Damara sheep. The trial lasted 42 days and was conducted in Western Australia. Twenty-four Damara sheep lambs were randomly allocated to an underfed (growth rate –100 g/day) and a control group (growth rate 100 g/day). Upon slaughter, fat-tail adipose tissue was sampled and analysed by atomic absorption spectrophotometry for mineral content. The results showed no significant differences regarding minerals concentrations/quantities, with the exception of zinc and calcium concentrations that were higher in the restricted group, likely as a consequence of feed restriction and a decrease in fat tissue amount. In conclusion, we have quantified for the first time several minerals in Damara sheep fat-tail and demonstrated that reducing their bodyweight does not affect mineral quantity in fat-tails of Damara sheep.

Muscle proteomics profiles in sheep: the effect of breed and nutritional status

Seasonal Weight Loss (SWL) is the most relevant constraint to animal production in the tropics and Mediterranean countries (Almeida et al., 2006). In fact, during the dry season characteristic of such climates animals may lose up to 20% of their initial weight, significantly affecting their productive performances with strong economic implications (Almeida et al., 2006).

Ovine liver proteome: Assessing mechanisms of seasonal weight loss tolerance between Merino and Damara sheep

The effect of feed restriction on the liver protein profiles of two different breeds of sheep was studied. We compared Merino with the Damara, breeds with respectively low and high tolerance to nutritional stress. Each breed was grouped into two nutritional treatments: restricted (12-14% loss of live weight) and control (maintenance). The trial lasted 42 days. Animals were sacrificed and liver samples subjected to label free shotgun proteomics. The resultant proteins had both their fold change and statistical significance in an unpaired t-test calculated to identify differential protein abundance. The tool WebGestalt was utilized to perform an Overrepresentation Enrichment Analysis (ORA) for gene ontology terms associated with the significant proteins. We further validated shotgun proteomics findings using a selected reaction monitoring (SRM)-based targeted proteomics approach, where similar trends in regulation were obtained for a subset of relevant proteins across an independent cohort of animals. Results confirm that Damara has adapted to nutritional stress by mobilizing stored fatty acids within adipose tissue and converting them to energy more efficiently than Merino. Finally, Merino had an overabundance pattern primarily directed to protein synthesis pathways. Regulated proteins identified may be used as a basis for marker selection towards tolerance to nutritional stress. BIOLOGICAL SIGNIFICANCE: Sheep are one of the most important livestock animals. They remain however poorly understudied and described. Seasonal weight loss (SWL) due to pasture scarcity during the dry season is one of the most limiting conditions to ruminant production in the tropics. To counter SWL, farmers may use supplementation, expensive or difficult to implement. A more suitable long-term solution would be to use breeds that are naturally adapted to nutritional stress. This work contrasts two breeds with different levels of tolerance to SWL, the Damara and the Merino, respectively well and poorly adapted. Comparison is conducted at the level of the hepatic tissue and using label free proteomics. This work identifies a series of pathways in the liver of the Damara via label free proteomics that suggest a unique fatty acid metabolic process within this breed. Proteins that have increased abundance in the Damara in association with fatty acid metabolism may be used as potential markers of tolerance to nutritional stress. This research will pave the way for more viable, long-term solutions for farmers facing annual production problems due to drought in the tropics and the Mediterranean region.