Abstract
The present research project was designed to evaluate the effects of pre and post-partum energy level and feeding pattern on the performance of crossbred dairy cows and their calves under farm conditions. Dietary energy level recommended by MAFF in the year 1984 was considered as the standard level throughout the experiments. To achieve the desired objectives of the study, a series of experiments were conducted. In the first experiment a total of 16 crossbred dairy cows were selected from Bangladesh Agricultural University Dairy Farm and the cows were divided into two similar more or less equal groups on the basis of their body weight and milk production. Cows of one group was given MAFF recommended dietary energy level and another group was given ad libitum diet (restricted concentrate + ad libitum roughage) during the last trimester of pregnancy. In order to assess the effects of feeding during pregnancy on the subsequent lactation performance of the cow, same type of feeding (ad libitum) was given to the cows of all groups. It was observed that body weight gain of restricted group was significantly lower (p<0.05) than that of the cows of ad libitum group (21.37±8.04 vs. 38.50±6.04 kg/cow, Total gain). Birth weight of calves from restricted and ad libitum group was 21.31± 2.18 and 20.31±3.27 kg / calf, respectively There was no significant effect of pre-calving nutrition on the gestation length of cows. During lactation period cows on restricted group produced more milk than the cows of the ad libitum group (3.06±0.34 vs. 2.84±0.46 kg/cow / day). There was no significant effect on pregnancy or growth rate of calves. No appreciable effect of pre-calving dietary energy was noticed on reproductive parameters like time required for calving to first heat, conception rate, service per conception and calving interval. Restricted feeding i.e. (MAFF's recommendation) was found suitable for pregnant cows. In the second experiment another two groups of crossbred cows, having eight in each group, was given two levels of dietary energy during last three months of pregnancy. In that case one group was given 30 % less (L) and another group was given 30 % more (H) than MAFF's recommendation. After calving all cows were given same ad libitum diet to assess the effects of pregnancy feeding on their performance. From the result it was observed that just before calving cows on low energy group gained significantly (p<0.01) less weight than that of the cows of high energy group (12.9±11.71 vs. 42.25±12.74 kg/ cow; Total weight). Calves of L energy group was significantly (p<0.05) lower than that of the calves of high energy group (17.87±1.78 vs. 20.73±2.24 kg / calf). Cows that were on low level pre-calving dietary energy level produced less milk during lactation than the cows of high energy pre-calving group (3.45±0.75 vs. 4.27±0.79 kg/ cow). No significant difference was noticed on calf growth rate and reproductive parameters. In this experiment, low level of energy, which was 30 % less than MAFF's recommendation was found very low and was not suitable for crossbred cows. From first experiment MAFF's recommendation and from 2nd experiment 30 % more than MAFF's was found suitable during the last trimester of pregnancy. These two energy levels were selected for the third experiment and attempts were made to monitor the effects of strategic feeding on the performance of the cows during pregnancy and lactation. In third experiment one group was given MAFF's recommended (M) feeding and another group was given 30 % more than MAFF's recommendation (H) during the last three months of pregnancy. In this case after calving 'M' group was given 'H' diet (30% more than MAFF's, recommendation) and the H group was given 'M' diet (according to MAFFS). So the combination of the groups were 'M-H' and 'H- M' type. It was found that the body weight gain of cows of 'M-H' group just before calving was nonsignificantly lower than that of the cows of 'H-H' group (25.40±10.60 vs. 40.50±21.07 kg / cow; Total gain). No significant difference was found between the birth weight of calves (22.10±2.39 vs. 21.35±3.01). Similarly no effect of pre- calving energy was noticed on gestation length of cows. After calving, during the 120 days lactation period, milk yield was significantly higher (p<0.01) in 'M-H' group than 'H-H' group (5.28±0.25 vs. 4.50±0.18 kg/cow) Non significant effect was observed on reproductive parameters of the cows. The fourth experiment was similar to the 3rd experiment. In this experiment energy levels during the pregnancy period were same as were used in third experiment i. e. 'M' and 'H' level. However, after calving M group received 'M' dietary level (M-M) and 'H' group received 'H' dietary energy level (H-H). From the result it was found that the cows on 'M-M' group gained significantly less (p<0.01) weight than that of the cows of H-H group during pregnancy period. Calf birth weight was non-significantly higher in M-M group than that of H-H group. Milk production was significantly higher (p<0.05) in M-M group than that of the H-H group (5.21±1.28 vs. 3.94±0.96 kg / cow /day). No significant effect was noticed on calf growth rate and reproductive parameters of cows. Except calving to first heat (104 vs. 61 days) was found significant (p<0.05). Judging from the results of all experiments it was recommended that too low or, high level of feeding during last three months of pregnancy was not suitable for crossbred dairy cows available in Bangladesh. A combination of MAFF's recommended dietary energy level during pregnancy and MAFF's recommended dietary energy level also during lactation was found suitable for our crossbred dairy cows during pregnancy and lactation under farm management conditions of Bangladesh.