Tackling the future challenges of Organic Animal Husbandry - vTI

RAHMANN G & GODINHO D (Ed.) (2012): Tackling the Future Challenges of Organic Animal Husbandry.
Proceedings of the 2 nd OAHC, Hamburg/Trenthorst, Germany, Sep 12-14, 2012
experimental groups, including 14 cows each, were housed in separate loose housing pens. Cows
were on pasture from the beginning of May until the middle of October. Cows were paired according
to their expected calving date, lactation number and their previous 305 days milk yield or breeding
index for the heifers, and then randomly allocated to the two treatments: 100 % organic feed
ration containing a mineral feed without vitamins (NSV - no synthetic vitamins), and the same 100
% organic ration containing the same mineral feed but including the synthetic vitamins A, D3 and E
(C – control). The experimental vitamin treatment started at least one month before expected calving.
All cows calved between November and February.
Cows were fed a partially mixed ration of grass-clover silage and rolled barley ad libitum, which
was supplemented with a barley/pea mixture, cold-pressed rapeseed cake and mineral feed in automatic
feeders. Cows were fed a minimum of 50 % roughage during the first three months after calving
and thereafter a minimum of 60 % roughage according to the standards for organic feeds. Minerals
and vitamins were fed according to Swedish recommendations. Control dry cows and control
cows in later lactation in year 1 were supplemented with 450 IU α-tocopherol and 60000 IU vitamin
A per day in the diet. Control cows in early lactation both years and in later lactation year 2 were
supplemented with 600 IU α-tocopherol and 80000 IU β-carotene per day in the diet. Nutrient composition
in DM of the silage (67 mg α-tocopherol, 56 mg β-carotene, 9.7 MJ ME, 140 g CP, 548 g
NDF in year 1 and 51 mg α-tocopherol, 48 mg mg β-carotene, 11.4 MJ ME, 129 g CP, 488 g NDF
in year 2) and concentrates were analysed by conventional methods. All vitamin analyses were performed
in the laboratories at Aarhus University, Research Centre Foulum, Denmark.
Five blood samples were taken from each cow and lactation at 3 weeks before expected calving
(BEC), within 24 hours after calving (PC – post calving) and at 3 to 4 weeks PC. In addition, samples
were taken 3 to 5 months and 7 to 9 months PC. Five milk samples were collected during lactation,
from colostrum (within 15 hours after calving), 4 days PC, and thereafter at morning milkings
on the same day as blood were collected. Milk yield was recorded and milk composition (fat, protein,
urea and somatic cell count) was analysed. Fertility of the cows was determined as number of
artificial inseminations (AI) per conception and number of days between calving and the first AI as
well as calving interval. All veterinary input was registered continuously as a measure of cow
health.
Statistical data on the 28 cows from year 1 and year 2 were analysed separately as there were no
interactions between year and treatment, with the exception of health parameters. Statistical analyses
of variance were made using the Mixed Model procedure of SAS (2003). The first three vitamin
samples were treated as repeated measurements. Values for somatic cell count (SCC) in milk
were logarithmically transformed (natural logarithm) to obtain a normal distribution of the data. For
each treatment group (NSV and C) and year, the number of animals with no diseases was counted,
as well as numbers of cows treated for mastitis, paresis and other diseases. Statistical analyses were
done (comparisons between treatments within each category, within each year and between years)
with Fischer´s exact test. Results with a P-value less than 0.05 were regarded as significantly different,
whereas 0.05 < P < 0.10 indicated that the results tended to be significant.
Results
In both treatment groups the plasma α-tocopherol concentrations were low during the transition
period, especially at calving (1.73 and 1.66 mg/l plasma year 1 and 2, respectively), when it was
significantly lower (P < 0.001) than at 3 weeks BEC and 3 to 4 weeks PC (year 1: 3.17 BEC and
3.35 PC, year 2: 3.02 BEC and 3.58 PC). The concentration of β-carotene at calving was 2.86 and
3.08 mg/l plasma and the retinol concentrations were 0.21 vs. 0.30 mg/l plasma year 1 and 2, respectively.
A tendency for a lower level of β-carotene in plasma from C cows than in plasma from
NSV cows at 3-5 months PC was found in year 1 (NSV: 10.81; C. 8.28 mg/l plasma, P=0.068). No
other differences were found in α-tocopherol and β-carotene in blood plasma between NSV and C
cows.
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