Essential fatty acid profiles differ across diets and browse of black rhinoceros

Assessment of the effects of storage temperature on fatty acid analysis using dried blood spot cards from managed southern white rhinoceroses (Ceratotherium simum simum): implications for field collection and nutritional care

BACKGROUND

Southern white rhinoceroses (Ceratotherium simum simum) are an endangered species in decline due to poaching and negative habitat changes. Conservation of the species has become increasingly important and a focus on better human management has become prevalent. One area of management that impacts southern white rhinoceroses is nutritional health monitoring, which is often conducted through blood analysis. Blood analysis conducted during field research can be difficult due to temperature, distance, and limited technological resources, so new methods of fast, and relatively stable blood collection are being pursued. One method that has been used in humans for many years is beginning to make its way into wildlife studies: the use of dried blood spot (DBS) cards. These cards are used as a tool to store single drops of whole blood on specialized filter paper and, once dried, can be used for nutritional biomarker analysis. An area of interest for southern white rhinoceroses and nutrition is monitoring fatty acid percentages for cardiovascular, immune, and reproductive health. The time and temperature limitations for storing blood fractions or liquid whole blood when analyzing fatty acids have been investigated, but few studies have performed storage studies on DBS cards colder than -20 °C or in non-human species.

METHODS

In order to better understand the limitations of DBS cards and the impact of temperature on fatty acid DBS samples in long-term storage, triplicate samples from seven adult southern white rhinoceroses at the North Carolina Zoo were collected and subjected to three storage treatments (immediate, room temperature (23 °C), or frozen (-80 °C) for 1 year).

RESULTS

Stearidonic (18:4w3) (Δ 0.3%), arachdic (20:0) (Δ 0.1%), eicosatetraenoic (20:4w3) (Δ 0.2%), and erucic acid (22:1w9) (Δ 0.1%) were in higher concentration in frozen than initial. Fatty acids in higher concentrations in the initial samples than frozen were myristic (14:0) (Δ 0.2%), mead (20:3w9) (Δ 0.1%), docosatetraenoic (22:4w6) (Δ 0.2%), nervonic (24:1) (Δ 0.1%), and total highly unsaturated fatty acids (HUFAs) (Δ 0.7%). Stearic (18:0) (Δ 2.2%), stearidonic (18:4w3) (Δ 0.3%), arachdic (20:0) (Δ 0.2%), paullinic (20:1w7) (Δ 0.4%), eicosatetraenoic (20:4w3) (Δ 0.1%), eicosapentaenoic (20:5w3) (Δ 0.1%), docosatetraenoic (22:4w6) (Δ 0.2%), nervonic acid (24:1) (Δ 0.2%), monoenes (Δ 1.9%), and total saturates (Δ 3.6%) had higher concentrations in room temperature than initial. Linoleic (18:2w6) (Δ 4.9%), mead acid (20:3w9) (Δ 0.1%), total polyunsaturated fatty acids (5.3%), and total omega-6 fatty acids (Δ 4.8%) had higher concentrations in initial compared to room temperature. Arachidonic (20:4w6) (Δ 0.4%) and omega-3 docosapentaenoic acid (22:5w3) (Δ 0.1%), had higher concentrations in frozen than in room temperature.

DISCUSSION

The frozen samples had the fewest statistical differences compared to room temperature samples and essential omega-3 and -6 fatty acids were stable with freezing up to 1 year. While more research is still warranted, current results suggest that DBS samples are best utilized when immediate analysis or -80 °C storage is available.

Implications of Nutritional Management on Fatty Acid Profiles of Southern White Rhinoceroses (Ceratotherium simum simum) Housed at Two Zoological Institutions

Southern white rhinoceroses (Ceratotherium simum simum) are African megaherbivores that are considered near threatened by the International Union for the Conservation of Nature. The fatty acid circulating values of these animals have not been thoroughly investigated. Fatty acids are critical for immune, heart, skin, and reproductive health, and may have a significant impact on the management and conservation of this species. Published data on fatty acids in this species is limited to incomplete profiles with very few animals in managed environments. The objectives of this research were to provide novel fatty acid percentage profiles for managed healthy southern white rhinoceroses, as well as to provide comparisons between two zoological institutions with differences in diet and climate during two distinct pasture growth periods. Whole blood samples were collected as dried blood spots from six rhinoceroses at the North Carolina Zoo (NC Zoo) and five rhinoceroses at Busch Gardens Tampa (BGT) in the low growth period (February to April) of 2019 and during the high growth period (July to September) of 2020. Fatty acid results indicated numerous differences when comparing the institutions within the same growth period and when comparing the same institution between its two growth periods. Most noteworthy were the higher levels of α-linolenic acid (18:3w3) and total omega-3 fatty acids and the lower linoleic acid (18:2w6), total omega-6 fatty acids, and omega-6 to omega-3 ratio found in the BGT population in both growth periods. This study provides novel percentages of fatty acids in managed southern white rhinoceroses and data on how fatty acid profiles may be altered between two housing locations via dietary differences in hay type and quantity, pasture availability via season, and pellet inclusion levels.

Evaluation of season-related dietary changes on the serum profiles of fat-soluble vitamins, mineral, fatty acids, and lipids in the captive greater one-horned rhinoceros (Rhinoceros unicornis)

Circulating concentrations of fat-soluble vitamins A, D, and E, minerals, fatty acids, and lipids were quantified in five captive greater one-horned rhinoceroses (Rhinoceros unicornis) throughout two time periods, during which two diets were offered. Animals were fed mixed-grass hay and concentrate pellets while managed in barns for winter housing (April sampling, winter diet). During the spring and summer, animals were fed the same amount of concentrate pellet but had free access to North American browse and grasses instead of dried forage (November sampling, summer diet). Levels of 25-hydroxyvitamin D and α-tocopherol were statistically higher in summer diet samples than in winter diet samples. Retinol was not statistically different between seasons, and β-carotene concentrations were undetectable at both time periods. Cholesterol, triglycerides, and non-esterified fatty acids were all significantly elevated following access to unlimited fresh forages in summer. Serum electrolytes were not different between the two time periods but differences in circulating minerals were noted (cobalt, inorganic iodine, and magnesium elevated in winter diet samples; selenium and zinc elevated in summer diet). Access to non-native fresh green forages resulted in improvement of several nutritional parameters in greater one-horned rhinoceroses, implying a benefit when fresh browse and access to grass is provided.

Fatty acids in mountain gorilla diets: implications for primate nutrition and health

Little is known about the fatty acid composition of foods eaten by wild primates. A total of 18 staple foods that comprise 97% of the annual dietary intake of the mountain gorilla (Gorilla beringei) were analyzed for fatty acid concentrations. Fruits and herbaceous leaves comprise the majority of the diet, with fruits generally having a higher mean percentage of fat (of dry matter; DM), as measured by ether extract (EE), than herbaceous leaves (13.0% ± SD 13.0% vs. 2.3 ± SD 0.8%). The mean daily EE intake by gorillas was 3.1% (DM). Fat provided ≈14% of the total dietary energy intake, and ≈22% of the dietary non-protein energy intake. Saturated fatty acids accounted for 32.4% of the total fatty acids in the diet, while monounsaturated fatty acids accounted for 12.5% and polyunsaturated fatty acids (PUFA) accounted for 54.6%. Both of the two essential PUFA, linoleic acid (LA, n-6) and α-linolenic acid (ALA, n-3), were found in all of the 17 staple foods containing crude fat and were among the three most predominant fatty acids in the diet: LA (C18:2n-6) (30.3%), palmitic acid (C16:0) (23.9%), and ALA (C18:3n-3) (21.2%). Herbaceous leaves had higher concentrations of ALA, while fruit was higher in LA. Fruits provided high amounts of fatty acids, especially LA, in proportion to their intake due to the higher fat concentrations; despite being low in fat, herbaceous leaves provided sufficient ALA due to the high intake of these foods. As expected, we found that wild mountain gorillas consume a diet lower in EE, than modern humans. The ratio of LA:ALA was 1.44, closer to agricultural paleolithic diets than to modern human diets.

Plasma and erythrocyte fatty acids in captive Asian (Elephas maximus) and African (Loxodonta africana) elephants

The fatty acid components of the plasma triglycerides and the phospholipid fractions of the red blood cells of a captive group of two African (Loxodonta africana) and four Asian (Elephas maximus) elephants were investigated. All the animals received the same diet of hay, fruits and vegetables, and concentrates. A comparison with data from free-ranging African elephants or Asian work-camp elephants showed that the captive elephants had lower proportions of polyunsaturated fatty acids (PUFAs), and for several lipid fractions a higher n-6:n-3 ratio, than their counterparts in the wild or under the more natural, in terms of diet, work-camp conditions. The difference in PUFA content was smaller in the African than in the Asian elephants. The captive Asian elephants tended to have lower levels of n-3 and total unsaturated fatty acids in their red blood cells than the captive African elephants.