EVALUATION OF COMPLETE FEEDS WITH VARYING LEVELS OF NEUTRAL DETERGENT FIBRE FOR LACTATING DAIRY COWS
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Date
2015-12-30
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COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR
Abstract
A study of six months duration was conducted to assess the effect
of different levels of neutral detergent fibre (NDF) in complete feeds for lactating
dairy cows in early and mid lactation on the basis of production performance,
influence on rumen fermentation parameters and economics. Three isonitrogenous
and isocaloric complete rations, T1, T2 and T3 with 25, 30 and 35 per cent NDF,
respectively were formulated as per ICAR (1998). Eighteen dairy cows yielding
approximately 10 kg of milk per day and within two weeks of calving were
divided into three groups of six each, and allotted randomly to the three
experimental rations. The results revealed that during the first four fortnights the
body weight of cows fed on ration T3 was significantly higher (P<0.05) than those
fed on T1 and T2, with T1 and T2 being similar (P<0.05). The animals in T3
started gaining weight from the first fortnight itself, while those in T2 started
gaining weight from the second fortnight and those in T1 only in the third
fortnight, indicating that the animals in T3 were able to withstand the negative
energy balance at the start of lactation, better than T2 and T3. The average body
weight of animals fed on the experimental rations, T1, T2 and T3 over the total
180 days experimental period was 343.13, 344.83 and 361.60 kg, respectively and
the values were similar (P<0.05), even though it tended to be higher in T3 than T1
and T2. The average daily dry matter intake was 13.93, 14.36 and 14.64 kg for
the animals fed on the experimental rations T1, T2 and T3 respectively, indicating
that the intakes in the three dietary treatments were similar (P<0.05). The average
daily milk yield of cows fed on the experimental rations T1, T2 and T3, over the
total 180 days experimental period was 11.08, 11.81 and 12.09 kg, respectively;
indicating that the milk yields were similar (P<0.05). The milk yield of cows fed
on all the three experimental rations started increasing from the first fortnight
onwards with cows fed on ration T3 attaining peak milk yield in the second
fortnight while animals in T2 and T1 reached the peak in the third fortnight. The
animals fed on ration T3 remained in peak milk yield for a total of six fortnights,
while those fed on T2 and T1, remained in the peak for five fortnights, indicating
greater persistency of milk yield in cows fed on ration T3 than T2 and T1. There
was no significant difference (P<0.05) in various haematological parameters such
as haemoglobin, glucose and blood urea nitrogen in blood; plasma protein
parameters such as total protein, albumin, globulin and albumin: globulin ratio
and mineral parameters such as plasma calcium and phosphorus levels at 1, 90
and 180 days of the experiment, between the three dietary treatments, with all the
values being in the normal range for lactating dairy cows. There was no
significant difference (P<0.05) in milk composition parameters such as fat, total
solids, solids not fat and protein, between the three dietary treatments, with all the
values being in the normal range for milking cows. The milk urea nitrogen
(MUN) content of cows decreased linearly and significantly (P<0.05), with
increase in NDF content of the ration and the values in the total experimental
period was 13.14, 11.12 and 10.10 mg per cent, respectively for cows fed on the
experimental rations T1, T2 and T3, which were within the normal range.
There was no significant difference (P<0.05), between the dietary
treatments, in digestibility coefficients of all nutrients, except acid detergent fibre,
which was significantly higher (P<0.05) in T2 and T3 than T1, with T2 and T3
being similar (P<0.05). No significant difference was noted, in total purine
derivatives excretion in urine, in both early and mid lactation, even though, in
early lactation, the uric acid excretion was significantly lower (P<0.05) in T2 than
T1, with T3 being similar (P<0.05) to both T1 and T2. The microbial protein
synthesis of animals fed on the three experimental rations were similar (P<0.05).
The animals fed on all three experimental rations showed a positive nitrogen (N)
balance, with no significant difference (P<0.05) between the treatments. The pH
of rumen liquor collected at the end of the experiment was 6.10, 6.10 and 6.17 for
cows fed on the experimental rations T1, T2 and T3, respectively, with the values
being similar (P<0.05) and in the normal physiological range of 5.80 to 6.40. The
total volatile fatty acid content was highest in T3, followed by T2 and T1, in
descending order (P<0.05), with the values being 73.71, 80.51 and 83.68 meq/l in
cows fed on the experimental rations T1, T2 and T3, respectively. The rumen
ammonia production was significantly lower (P<0.05) in T3 than T1 and T2, with
T1 and T2 being similar (P<0.05) and the values were 26.02, 25.21 and 22.83 mg/
100 ml in cows fed on the experimental rations T1, T2 and T3 respectively. The in
vitro gas production values of the three experimental rations T1, T2 and T3 in
early as well as mid lactation were similar. The metabolisable energy and
digestible organic matter content of the three rations, calculated from the gas
production values were also similar. The average number of days to first post partum heat for cows fed on the experimental rations T1, T2 and T3 were 70.17,
80.33 and 65.50, respectively indicating that cows fed on ration T3 came into heat
earlier than cows fed on the other two rations. The average cost of production of
one kg of milk in the total experimental period was Rs. 31.64, 30.99 and 30.98 in
the groups T1, T2 and T3 respectively.
A thorough evaluation of the results obtained in both phases as well as the
total experiment revealed that cows in all the three dietary treatments performed
well, with the complete rations T3 with 35 per cent NDF and T2 with 30 per cent
NDF, showing better performance than T1 with 25 per cent NDF. Among T2 and
T3 which were more or less comparable, the cows fed on the diet T3 had a higher
body weight, was able to withstand negative energy balance better, had a higher
average daily milk yield, remained in peak milk yield for longer period and came
into heat earlier than those fed on T2. It could also be seen that animals fed on
ration T3 had a significantly lower (P<0.05) MUN and rumen ammonia, had a
higher (P<0.05) TVFA and lower rumen pH, a non-significant (P<0.05), but
higher digestibility for NDF, ADF and crude fibre and a more positive N balance
as well as per cent retention of N than T2, indicating that T3 was better than T2.
These results suggest that complete rations containing paddy straw as the sole
source of roughage, with 25 to 35 per cent NDF can be recommended for use
among early and mid lactation dairy cows of Kerala, with 35 per cent being the
ideal NDF level.
Description
Submitted in partial fulfillment of the requirement for the degree of
Doctor of Philosophy in Veterinary and Animal Sciences.