Articles 121-130

Eggs, endothermy and milk: A novel scenario for the evolution of lactation

O.T. Oftedal

Nutrition Laboratory, Conservation and Research Center, Smithsonian National Zoological Park, Washington DC 20008

Lactation is a primary mechanism for transfer of nutrients from mother to young in all mammals, but its evolutionary origin is shrouded in mystery. The synapsid branch that was to produce mammals separated from the sauropsid branch (ancestors of turtles, squamates, tuataras, crocodilians and birds) in the Carboniferous, more than 310 million years ago (mya). Mammary glands may be an ancient synapsid feature, but there are no preserved intermediate structures in living or fossil taxa that demonstrate how or when they came into being. Herein I report a new evolutionary scenario for their origin.
Early synapsids, like other early amniotes, produced flexible-shelled eggs that would require an environmental source of water, as do extant squamate eggs. The global increase in temperature and aridity in the Permian, coupled with the gradual development of endothermic metabolism among therapsids, would have exacerbated this need. Yet if incubated eggs had to be thermally isolated, access to environmental moisture would have been limited. I hypothesize that secretions of abdominal skin glands became an important moisture source for eggs, and were essential for endothermic incubation in advanced therapsids. [Birds produce eggs with highly calcified shells that are resistant to water vapor flux, and thus do not face the same constraints.] In monotremes and marsupials the mammary glands develop in intimate association with hair follicles, suggesting that the evolution of hair and mammary glands are linked. It is possible that hair evolved as a means of retaining and dispersing glandular secretions needed by eggs, and only subsequently proliferated over the body to provide insulation.
These secretions subsequently became important for hatchlings as an ingested fluid (“milk”). Evolutionary modification of lysozyme to alpha-lactalbumin made synthesis of lactose and its oligosaccharide derivatives possible, milk lipids came to be secreted as membranebounded globules, and novel casein proteins provided amino acids and calcium to the young. These supplemented and then supplanted yolk nutrients. Suckling per se may have required development of a secondary palate, as seen in therocephalian, dicyonodont and cyonodont therapsids. Lactation must have been well established in advanced cynodonts in the Late Triassic (ca. 200-225 mya), because early mammaliaforms appear to have produced altricial young. This conclusion is based on the presence of epipubic bones, the evolution of diphyodonty (reduction of tooth replacement to two sets), and the energetic consequences of small body size. Adult mammaliaforms in the Late Triassic and Early Jurassic were mostly very small; a recently discovered form was 2-3 g in mass.
Early mammaliaforms probably sucked from an areolar area that lacked nipples, as do extant egg-laying monotremes. Evolution of a nipple may only have become possible when it was no longer necessary to disperse secretions for egg uptake, i.e. with the development of livebearing after therians (ancestral to marsupials and eutherians) split off from the monotremes more than 125 millon years ago.

The protein-to-fiber ratio does not predict feeding selectivity among primate frugivores

N.L. Conklin-Brittain, A.J. Marshall, C.D. Knott, R.W.Wrangham, and M. Leighton

Department of Anthropology, Harvard University, Cambridge, MA 02138, USA.

The ability to dependably predict feeding selectivity would have many theoretical and practical applications. The protein-to-fiber ratio has been used, with varying degrees of success, to predict feeding selectivity in many species of animals. In primatology, this ratio has been used with a similarly sporadic success rate. In this report we will present new data from four species of frugivorous primates, and discuss why this ratio frequently fails, both here and in other literature reports.
The most common form of this ratio used in primatology is crude protein divided by acid-detergent fiber (CP/ADF) and compared to some measure of selectivity. Here we will use time spent feeding on the different food items. Our results, from Kibale Forest National Park, Uganda, show that CP/ADF did not predict the feeding choices made by chimpanzees (Pan troglodytes; r = 0.031, p = 0.6542, n = 212), Group 30 blue monkeys (Cercopithecus mitis: r = 0.071, p = 0.3447, n = 178), Group 14 mangabeys (Cercocebus albigena: r = 0.023, p = 0.7333, n = 230), Group 30 mangabeys (r = 0.024, p = 0.7042, n = 260), and Group 30 redtail monkeys (Cercopithecus ascanius: r = 0.095, p = 0.173, n = 206). However, it did predict Group 14 blue monkeys (r = 0.287, p <0.0001, n = 211), and Group 14 redtail monkeys (r = 0.195, p = 0.0054, n = 203).
In neither of the cases where the ratio predicted feeding time was protein by itself predictive (r = 0.075, p = 0.2873 and r = 0.038, p = 0.5864 respectively). The predictive power was probably coming from the fiber fraction (r = 0.304, p <0.0001 and r = 0.245, p = 0.0004 respectively). As an interesting twist, in three of the five cases where the ratio was not predictive, the fiber fraction did (negatively - as expected) significantly predict time feeding but the protein fraction also, negatively, significantly predicted time feeding. Overall, inconsistent results like these and those from the literature indicate that the CP/ADF ratio is not a dependable predictor of frugivore diet selection.

Australian marsupials eat Acacia !

N.A. Irlbeck1*, I.D. Hume2

1Department of Animal Sciences, Colorado State University, Fort Collins, CO USA;
2Department of Biology, University of Sydney; Sydney NSW Australia

Evaluation of Australian marsupial diets always emphasizes Eucalyptus, however, there is another food source of major importance – Acacia. Acacia species play a major role not only as a food source, but also in determining the characteristics of Australian landscapes. Acacia are legumes, relying on symbiotic bacteria for nitrogen fixation. Because Acacia’s ability to fix nitrogen, its nutritive value might be expected to be higher than most browse species (Gutteridge and Shelton 1994).
Due, however to the phyllode leaf structure and high tannin content; Australian Acacia tends to be lower in nutritive value - high fiber and low digestibility. Acacia rarely has toxic effects on animals, but some Acacia contain secondary metabolites that may be feeding deterrents. Secondary metabolites found within various Acacia include tannins, oxalates, cyanogens and fluroacetate. Evaluation of Australian marsupials and how they utilize Acacia to compliment other dietary ingredients is a unique opportunity into animal nutrition, gastrointestinal physiology, behavior and environmental circumstances. We will briefly look at Acacia gum, foliage, arils, seeds, pollen or flowers and the animals that have adapted to an Acacia-based diet. In order to utilize Acacia gum as an energy source, it is essential that mammals have the necessary gut flora capable of fermenting complex polysaccharides found in gum (Lindenmayer, 1996). These microflora are retained in enlarged fermentation chambers in the gastro-intestinal tracts of these marsupials, specifically the caecum and forestomach (Hume 1999).
There is a direct relationship between hindgut caecum size and proportion of Acacia gum consumed. The largest caecum sizes are found in animals consuming large amounts of gum. Conversely, those with smaller caecums consume little or no gum. Acacia foliage is consumed by few marsupial species except in times of drought or low food shortages. Dried Acacia leaves are more commonly consumed than fresh Acacia, probably due to a lower tannin concentration. The low intake may be due to high fiber content or secondary compounds that the animal would have to metabolize for detoxification. Acacia seeds are consumed only by a few species, and the lipid-rich arils consumed preferentially by lactating mahogany gliders. Acacia is critical to the survival of many native Australian marsupials as a food source - gum, foliage, arils and seeds, in addition to habitat. Many of these unique creatures have developed gastrointestinal compliments to enable them to ferment, digest and detoxify Acacia, having a seemingly innate ability to select those components needed. Often the use of Acacia species is opportunistic chosen, or is linked to environmental conditions, but there is no denying the role Acacia plays in the survival of these species and the Australian landscape.

Gutteridge, R.C. and H.M. Shelton 1994. The role of forage tree legumes in cropping and grazing systems. In Forage tree legumes in tropical agriculture ed by R.C. Gutteridge and H.M. Shelton. CAB International: Wallingford.
Hume, I.D. 1999. Marsupial nutrition. Cambridge University Press: Cambridge. Lindenmayer, D.B. 1996. Wildlife and woodchips – Leadbeater’s possum, a test case for sustainable forestry. University of New South Wales Press: Sydney.

Brookfield Zoo Databank Overview

Kimberly D. Ange1 and Susan D. Crissey2

1North Carolina State University, Department of Animal Science, Raleigh, NC 27695-762, USA
2Daniel F. and Ada L. Rice Conservation Biology and Research Center, Chicago Zoological Society, Brookfield Zoo, Brookfield, IL 60513 USA.

Currently nutritional challenges remain for those commonly managing many captive species and usually no indications of nutritional status exist. Even when biochemical nutritional status is assessed, limited information is available with which to compare to determine if a particular animal or nutrient is within normal ranges. Determinations of circulating levels of lipids (total cholesterol, HDL-cholesterol, measured LDL-cholesterol, and triacylglycerides), vitamin D metabolites and vitamins A and E, carotenoids and minerals can provide a base for examining the nutritional status of animals. Additionally, as free-ranging populations become more fragmented and resources more scarce, assessment of nutritional status in healthy populations will serve as a baseline from which to compare questionable populations. The purpose of examining nutritional status in many animals representing numerous species was to establish normal values for captive exotic animals.
The nutritional status data bank currently holds data for up to 8 canid species (n=45), 17 felid species (n=83), 25 primate species (n=235), 4 ursid species (n=22) and 22 miscellaneous grouped species (n=62) which were housed at four zoos (Brookfield Zoo, Fort Worth Zoo, Lincoln Park Zoological Gardens, and North Carolina Zoological Park) for over 5 years.
However, due to the quantity of blood needed, all analyses were not performed for all animals. These measurements are unique because they are derived from healthy animals with known diets and because they represent comparatively large groups of animals for most species measured. Several species-specific anomalies in the measured blood parameters became evident. It is important to examine these data to determine the potential impact on both zoo animal nutrition and ultimately animal conservation.
Some of the irregularities include the following: 1) Spectacled bears had the greatest total cholesterol (369 mg/dl (n = 7)) and triacylglycerides (1079 mg/dl (n = 7) levels of all species measured, 2) Compared to other canids, the maned wolves and the African wild dogs had the greatest total cholesterol (268 mg/dl (n=9) and 261 (n = 5), respectively) while the maned wolves possessed the greatest HDL-cholesterol (209 mg/dl (n = 5)) levels, 3) Sand cats had substantially greater retinyl palmitate (3149 nmol/L) and retinyl stearate (4882 nmol/L) than all other feline species measured, 4) Cholesterol and LDL-cholesterol were the highest in gorillas (247 mg/dl n=33 & 144 mg/dl n=32, respectively) and second highest in spider monkeys (195 mg/dl n=13 & 137 mg/dl n=12, respectively), and 5)
Vitamin D deficiencies in certain primate species despite adequate levels in diet. While examining the nutritional status of captive animals is important, often there are not data on free-ranging counterparts available for comparison. In addition, some research studies have shown that the nutritional status data obtained from free-ranging animals are somewhat different compared to those of their captive counterparts. Thus it is important to note that some inferences made on nutritional status of captive animals may not apply to free-ranging animals and vice versa. In summary, the nutritional status project provides a databank that gives a unique collection of information on normal circulating blood values in a large number of captive animals. These data provide a baseline to understanding the health and nutritional needs of captive animals. With the aid of future cooperative research studies in this area, the conservation of both freeranging and captive species may come closer.

Recent activities of the United States National Research Council Committee on Animal Nutrition

Jamie S. Jonker*1; Christopher Rogers1; Gary L. Cromwell2; Charlotte Kirk Baer1

1Board on Agriculture and Natural Resources, National Research Council, Washington, DC 20418;
2Department of Animal Sciences, University of Kentucky, Lexington, KY 40546

The Committee on Animal Nutrition (CAN) oversees The Nutrient Requirements of Domestic Animals covering approximately 30 species of economically important farm animals, laboratory species, wildlife, and companion animals. Reports are used as a standard worldwide by government agencies for research and regulatory purposes, by universities for teaching and research, by extension personnel, by food and feed industries and by veterinarians, livestock producers, and pet owners. In addition to the consensus reports in this series, CAN also addresses prevailing and emerging issues through Special Reports and Events. The primary focus of CAN changes over time in response to emerging issues and changing national needs. Early on, CAN’s focus was improving animal nutrition to ensure an adequate food supply for the population during times of war. Today, the major focus of its work is centered in environmental quality, animal production, food safety, and animal and human health. Advances in science and technology, such as genetically improved animals, require continual reassessment of nutrient requirements. Changes in management strategies to address environmental concerns necessitate on-going review of animal nutrition and feeding approaches.

Several reports that were published recently by CAN serve as examples of the continuing work of this committee and its response to emerging issues. Nutrient Requirements of Dairy Cattle, Seventh Revised Edition has expanded greatly in scope from earlier editions and is based on the wealth of information that has emerged in the past decade. The second edition of Nutrient Requirements of Nonhuman Primates is a much-needed comprehensive volume that addresses primate feeding, digestive physiology, and nutrient requirements of primates, many of which are endangered and threatened species. Scientific Advances in Animal Nutrition is a special report by CAN that is structured to highlight the critical role of animal nutrition in the future for a diverse readership. Responding to rapidly growing public concerns about air emissions from confined animal feeding operations in the United States, CAN’s report, The Scientific Basis for Estimating Air Emissions from Animal Feeding Operations, identifies the scientific criteria needed to ensure that estimates of air emission rates are accurate, assesses emission-estimating mitigation techniques, and identifies best management practices.

Nutritional aspects of the dry-season diet of mountain gorillas in Bwindi Impenetrable National Park, Uganda: preliminary results

Jessica M. Rothman1, Alice N. Pell1, Ellen S. Dierenfeld2,Colleen M. McCann3 and Eloy Rodriguez4

1Department of Animal Science, Cornell University, Ithaca NY 14850 USA
2Department of Wildlife Nutrition, Wildlife Conservation Society, Bronx, NY 10460 USA
3Department of Mammalogy, Wildlife Conservation Society, Bronx, NY 10460 USA
4Department of Plant Science, Cornell University, Ithaca NY 14850 USA

Plants (N=128) and fungi (N=2) eaten by highly endangered mountain gorillas (Gorilla gorilla beringei) in Bwindi Impenetrable National Park, Uganda were collected, processed, and analysed for their chemical composition. Plant parts and fungi were identified as food items when gorillas were observed feeding on them or by their trail remains. Foods were collected within the home range of the gorilla group observed and were dried, packaged, and transported to Cornell University’s animal nutrition laboratories in New York, USA and the nutrition laboratory at the Wildlife Conservation Society, New York, USA. Moisture content was recorded and foods were analysed for acid and neutral detergent fiber, lignin, crude protein, soluble carbohydrates, condensed tannins, and total phenolics using standard methods. Preliminary results indicate that Bwindi mountain gorillas eat protein rich leaves (4% to 26% crude protein) compared with their overall diet (2% to 14% crude protein). Neutral detergent fiber ranged from 22% to 78% and acid detergent fiber ranged from 9% to 42% dry matter in food parts. Preliminary results reveal that lignin values in foods were 2% to 22% dry matter. Compared with Virunga gorillas, Bwindi gorillas eat more foods containing condensed tannins. The chemical analysis of common forest plants that are not consumed is in progress to assess the importance of chemistry in food selection. We plan to analyze foods collected in other seasons and conduct observations of food intake to quantify frequency of consumption of each food item. The combination of chemical analyses and observations of food intake will provide the data for calculation of nutrient intake of the Bwindi gorillas. Understanding the feeding ecology and nutritional needs of Bwindi gorillas is essential to their management and conservation in situ, and provides useful comparative data for optimizing ex situ feeding management of gorillas.

Vitamin A nutrition of cockatiels

E.A. Koutsos* and K.C. Klasing

Department of Animal Science, One Shields Avenue, University of California, Davis Davis, CA 95616

The vitamin A (VA) requirements for Psittacine birds have not been experimentally determined, and often are extrapolated from the VA requirements for growth and egg production of chickens, turkeys, domestic ducks and Japanese quail. However, due to substantial differences between digestive physiology, rates of embryonic and post-hatch development, and desired performance of psittacine species, it is difficult and potentially erroneous to infer psittacine VA requirements based upon those of commercial poultry. Therefore, the purpose of these experiments was characterize the responses of adult and growing Psittacines (Cockatiels, Nymphicus hollandicus) to various dietary vitamin A levels. Adult female cockatiels at maintenance were randomly assigned to 1 of 4 dietary treatments, containing 0, 2000, 10000, or 100000 IU VA/kg. Birds were monitored for ~ 700 days for signs of VA deficiency or toxicity by a variety of parameters. Additionally, newly hatched cockatiel chicks were randomly assigned to 1 of 3 dietary treatments, containing 0 IU VA/kg, 4000 IU VA/kg, or 2.4 mg b-carotene/kg diet. Birds were fed their assigned diets for approximately 5 weeks, and were monitored for a variety of parameters.

After 269 days of feeding, adult cockatiels fed 100,000 IU VA showed poor conditioning (reduced feather quality and increased prominence of keel bone), although no significant change in body weight was observed due to dietary treatment (P=0.30). In contrast, birds fed 0, 2,000 or 10,000 IU VA maintained body weight and conditioning for 700 days. VA level influenced vocalization patterns; in general, 0 or 100,000 IU VA altered the number of vocalizations, and reduced the average length and peak frequency of each vocalization (P<0.05). Plasma VA levels were not affected by 0 IU VA, but were increased by 10,000 or 100,000 IU VA (P<0.05). After ~35 days post-hatch, cockatiel chicks fed 0 IU dietary vitamin A developed signs of vitamin A deficiency, including poor feathering on the head, neck and breast regions, as well as dermatitis on the face. However, body weights of chicks were not affected by dietary treatment through day 36 post-hatch.

These data demonstrate that adult cockatiels at maintenance are much more susceptible to vitamin A toxicity than to vitamin A deficiency. Considering their wild-type diet, which is seed-based and would likely contain low levels of pre-formed vitamin A, adaptation to low dietary VA levels, and efficient storage of VA is not surprising. Growth trial results demonstrate that 0 IU VA is insufficient for chick growth and development. 4,000 IU VA or 2.4 mg b-carotene was sufficient to prevent signs of vitamin A deficiency, providing valuable information regarding this psittacine birds’ ability to utilize carotenoids as a vitamin A source. Based upon the apparent susceptibility to vitamin A toxicity, it may be prudent to include b-carotene as a vitamin A source in psittacine diets.

Determination of 25-Hydroxy Vitamin D in seed fed grey parrots

M.D. Stanford BVSc MRCVS

Birch Heath Veterinary Clinic, Tarporley,Cheshire, CW6 9UU, UK

Vitamin D deficiencies are common in captive birds kept indoors in a UV deficient environment with insufficient dietary vitamin D. The domestic fowl does not have a dietary requirement for vitamin D if it receives adequate UV light in the 285-315nm spectrum. Psittacines are commonly fed a seed based diet deficient in vitamin D. In addition psittacines kept indoors receive inadequate UV for cutaneous synthesis.It is well established that grey parrots are particularly susceptible to hypocalcaemia. It is postulated that seed based diets deficient in vitamin D are a possible contributory factor to this condition leading to nutritional secondary hyperparathyroidism but no study has measured vitamin D in psittacines. The aim of this study was to assess the vitamin D status of a colony of grey parrots fed an unsupplemented seed diet.
Vitamin D status is best assessed by assay of 25-Hydroxy Vitamin D due to its long half life compared with other vitamin D metabolites. Traditionally radio immunoassays (RIA) have been used to assay 25-Hydroxy Vitamin D but more recently enzyme immunoassays (EIA) have become available with the advantages of both convience and economy.
100 grey parrots were fed on a mixed seed diet with no additional supplementation. The group were kept indoors under artificial lighting. 40 birds were selected at random and blood samples taken from the brachial vein under sevoflurane anaesthesia. The blood samples were subjected to a standard haematological and biochemical profiles and the birds had a standardised clinical examination:any birds considered unhealthy were withdrawn from the study. This left a sample size of 34 healthy grey parrots.
The IDS OCTEIA 25-Hydroxy Vitamin D kit was used on the samples for the quantitation of 25-Hydroxy vitamin D. Each sample was assayed in duplicate. The results indicated a range of 25-Hydroxy Vitamin D between 5.1-380nmol/l with a mean of 119nmol/l. The results show a wide variation in the level of 25-Hydroxy Vitamin D in seed fed grey parrots. In mammals vitamin D levels below 50nmol/l are considered a vitamin D deficiency. Chronic vitamin D deficiency would lead to hypocalcaemia due to nutritional secondary hyperparathyroidism.
Analysis of the diet using the Zootrition program indicated a vitamin D level of 0.1%.It is suggested that minimal levels for vitamin D in the domestic fowl is .4%.
This study suggests that the vitamin D levels were low in 18 of the 34 birds sampled. All the birds had normal ionised calcium levels at the time of the study. Further studies on the same group are being carried out to analyse the effect of increasing levels of UV light in the 285- 315nm spectrum and dietary changes to pelleted diets on the vitamin D levels. Initial observations on 5 grey parrots kept on pelleted food (Harrisons High Potency Course) under the same husbandry conditions indicate higher levels of 25-hydroxy vitamin D compared with the seed fed birds.

Differential absorption of natural versus synthetic alpha-tocopherol in Asian and African elephants

J.E. Swanson1, R.A. Pulver1, R.S. Parker1, E.S. Dierenfeld2

1Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA
2Department of Wildlife Nutrition, Wildlife Conservation Society, Bronx, NY, USA

alpha-Tocopherol (a-TOH) is the major antioxidant vitamin for mammalian species and the primary vitamer in the diet of free-ranging elephants. However, knowledge regarding the daily requirement, absorption and elimination of a-TOH in elephants is sparse. An investigation of the differences in absorption and elimination of a-TOH in Asian (Elephus maximus) and African (Loxodonta africana) elephants was conducted using differentially deuterium-labeled natural and synthetic a-tocopheryl acetate and a single dose pharmacokinetic experimental design.
An equimolar mixture of deuterated d3 -RRR-a-tocopheryl acetate (natural vitamer) and d6-all rac-a-tocopheryl acetate (synthetic vitamer) for a total of 4 g tocopheryl acetate was administered to healthy non-lactating adult female elephants (n=5 per species). Blood samples were collected at baseline (pre-dose) and 3, 9, 12, 24, 48, 72, 96, 120 and 144 hr post dose.
Comparison of the two elephant species found (1) A significantly greater plasma concentration of endogenous a-TOH in African elephants relative to Asian elephants: 0.70 ± 0.03 vs 0.26 ± 0.03 nmol/L . kg at baseline, P<0.001. (2) A greater plasma response to administration of the natural a-TOH vitamer in African elephants relative to Asian elephants: 0.20 ± 0.006 vs 0.011 ± 0.003 nmol/L . kg at 24 hr post-dose, P<0.001.
In addition, the area under the plasma concentration versus time curve for natural a-TOH was almost three times greater in African relative to Asian elephants, while no difference was found for synthetic a-TOH. (3) The rate of elimination of both tocopherol vitamers from the plasma pool was almost twice as fast in Asian elephants compared to African elephants. (4) The slower rate of loss of natural a-TOH compared to synthetic a-TOH in African elephants resulted in a significantly higher ratio of natural to synthetic a-TOH in plasma relative to the Asian elephants, P<0.01. These observations suggest that both African and Asian elephants may have mechanisms to discriminate between natural and synthetic a-TOH during absorption and elimination, and that these mechanisms may not be equivalent in both species. We also found that natural a-tocopherol is more bioavailable than synthetic a-tocopherol in both species of elephants.

Investigations on the influence of dietary cobalt supply on the vitamin B12 status of dairy cows

Kirsten Stemme1, U. Meyer2, G. Flachowsky2, H. Scholz3

1Institute of Animal Nutrition, School of Veterinary Medicine, Hanover
2 Institute of Animal Nutrition, Federal Agricultural Research Centre, Brunswick
3 Clinic for Cattle Diseases, School of Veterinary Medicine, Hanover

Micro-organisms in the forestomachs of ruminants are able to synthesize vitamin B12 (which is not present in feedstuffs of plant origin) in amounts which are sufficient to meet the animals’ requirements. However, a prerequisite is a sufficient supply of cobalt (Co), which is the central atom of the vitamin B12 molecule. As the recommendations for cobalt supply to dairy cows are mainly based on experiments which were carried out with sheep or beef cattle, the objective of this study was to analyse any effects of dietary cobalt supplementation on the vitamin B12 status of dairy cows.

The experiments encompassed a total of 20 dairy cows of the German Holstein breed, which were allotted to 2 groups (treatments) with different cobalt concentrations in the ration:
Group 1: controls without Co supplementation; » 0.1 mg Co/kg DM (» requirement) Group 2: extra supply of 0.2 mg/kg DM; » 0.3 mg Co/kg DM The animals were fed 1 kg balancing concentrate without or with a cobalt supplement. Additionally a dairy concentrate (0.15 mg Co/kg DM) was given according to milk yield. Wilted grass-silage was offered ad libitum as roughage; average daily intake amounted to about 12 kg DM.
During the experiment blood samples were taken at the beginning and subsequently in four week intervals for vitamin B12 analysis (chemilumineszenz technique). On experimental day 100, 200 and the day of calving samples were taken from the liver using the biopsy technique to determine the cobalt concentration by ICP-analysis. Dry matter intake from roughage and concentrates as well as milk yield were recorded daily, milk composition twice a week.

In both groups serum vitamin B12 concentrations increased during the course of lactation, without significant differences between groups which received a ration with an analysed cobalt content of 0.13 mg/kg DM (group 1) and 0.27 mg/kg DM (group 2). In the course of lactation vitamin B12 concentration in the liver decreased in both groups, but the concentration in group 2 showed a tendency towards higher levels on day 100 and 200. On the day of calving this difference proved to be significant (0.51 ± 0.06 mg vitamin B12/kg WW versus 0.64 ± 0.06 mg vitamin B12/kg WW). Differences in feed intake, milk yield and milk composition due to the different cobalt supply were not detected.

From the results it can be concluded that a cobalt content in the ration of 0.13 mg Co/kg DM seems to be sufficient. This value is lower than the GfE (1) allowances of 0.20 mg Co/kg DM.

(1) GfE (Gesellschaft für Ernährungsphysiologie) 2001: Empfehlungen zur Energie- und Nährstoffversorgung der Milchkühe und Aufzuchtrinder. DLG-Verlag, Frankfurt/Main

The study was supported by a grant from the H. WILHELM SCHAUMANN FOUNDATION