PhD

A study was conducted in two phases to assess the influence of level and
degradability of dietary protein on early lactation in crossbred cows. In phase I.
eighteeen crossbred cows in early lactation (within one month of lactation) were
selected and grouped into three as uniformly as possible with regard to age. Sex-
parity. previous production and stage of lactation and were fed with the
experimental rations comprising of concentrate mixtures having 26. 20 and 17 per
cent CP on DM basis and paddy straw. which were fed in the ratio 70:30 of total
DM. The three rations contained 20, 15.41 and 13.2 per cent CP and 63.86, 61.28
and 62.S per cent TDN on DM. respectively. Individual records of daily intakes
of concentrate and paddy straw. daily milk production. fortnightly data on body
weight and milk composition were maintained throughout the experimental period
of 100 days. Blood samples were collected for assessing levels of haemoglobin.
blood glucose. blood urea nitrogen (BUN). plasma calcium and plasma
phosphorus. Rumen liquor samples were collected for assessing pH. rumen
ammonia nitrogen (NH3-N) total volatile fatty acid (TYFA) and lactic acid
contents. A digestibility trial was conducted towards the end of experiment and
reproductive performance of the animals during the experimental period was also
assessed.
The average dry matter intake (DMI) of animals in the first group (2.99 per
cent of body weight) was lower (P<0.05) than those of group II and III (3.54 and
3.79 per cent of the body weight. respectively). The body weight of animals of the
three groups were similar. except in the fourth and sixth fortnight. when the
weight of animals in the second group was significantly higher (P<0.01) than
those of first and third. There were no significant differences in the milk
production or composition between the groups during the course of study. except
during the fifth fortnight. milk fat content of group III was lower (P<0.05) than
that of groups I and II. The pH and lactic acid contents of the rumen liquor


collected from animals of group I were higher (P<0.05) than those of groups II and
Ill. while the rumen NH3-N concentration was lower (P<0.05) for the third group
than that of the first and second groups. There was no significant difference on
the blood parameters such as haemoglobin. blood glucose. plasma calcium and
plasma phosphorus. between the groups while the blood urea nitrogen (BUN)
level in the 50th day collection was significantly higher (P<0.01) in the second
group than that of the third group. The digestibility coefficient of the nutrients
such as ether extract (EE). crude fibre ( CF). neutral detergent fibre (NDF) and
acid detergent fibre (ADF) were significantly higher (P<0.01) in the first group.
All the animals in the second group and one each in the first and third group
conceived during the experimental period. The average number of days from
calving to first AI of the animals of the three groups were 122. 79.4 and 80.
respectively. the difference being nonsignificant. The cost of producing one kg
milk in the three groups fed 20. 15.41 and 13.2 per cent CP rations was Rs. 7.79.
7.91 and 7.71. respectively. Results of the study suggest that CP level of 13.2 per
cent in the total ration was sufficient to meet the requirements of cows in early
lactation. producing a peak of 10 kg milk.
During phase II. 12 crossbred cows in early lactation (within one month
of lactation) were selected and grouped into two as uniformly as possible as done
"
in phase 1. They were fed 17 per cent CP concentrate mixture with two levels of
undegradable protein (UDP) (26.8 and 42.9 per cent of CP) and paddy straw as the
roughage in 70:30 ratio. The rations had 64.33 and 66.98 per cent TDN
respectively on DM basis. The experiment was conducted similar to that of phase
I for a period of 100 days. In addition to the parameters estimated in the first
phase. milk urea nitrogen also was estimated.
There was no significant difference in the body weight of animals of the two
groups during the experiment. The weekly average DMI was significantly higher
(P< 0.01) in the first group from the third week of experimental period. The milk

production of the animals of the two groups was significantly different during the
second and fourteenth week (P<0.01). during the seventh. eighth and thirteenth
week (P<0.05) and during the ninth. eleventh and twelfth week (P=0.06). There
was no significant difference in the milk constituents between the two groups
. except for the fat and total solids which were higher (P<0.01) for the first group.
There was no significant difference in the protein and urea nitrogen levels in the
milk. or any of the rumen parameters studied except for the rumen NH3-N level
which was significantly higher (P<0.01) in group I. Except for a significantly
higher (P there was no significant difference in the blood parameters studied between the
groups. The digestibility coefficient of the nutrients of the two rations were not
different. except EE. which was higher (P<0.01) for the second ration. The
reproductive performance of the animals were not affected by the UDP level of
the ration since three animals of the first group and two animals of first group
conceived during the experimental period. However the average days from calving
to first service was numerically lower. though not significant. for the animals of
the second group (90.7 in the first group and 74.8 in the second). The cost of
production of one kg milk in the two groups was Rs. 6.33 and 7.36. respectively.
The ration containing higher UDP (42.9 per cent of CP of concentrate mixture)
maintained the milk production better than the low UDP ration. but the cost of
production was also higher for high UDP fed group. .
From the overall results obtained in the present study it could be concluded
that a level of 13.2 per cent of CP in the total ration was sufficient for meeting the
protein requirements of early lactating crossbred cows producing around 10 kg per
day. Increasing the UDP level from 26.6 to 42.9 per cent of the CP maintained
production better. but cost of milk production was higher indicating that it is not
economical to provide high UDP ration for cows when the average daily
production is around 10 kg