MATERIALS AND METHODS

Method Adopted to Enrich and Ensile Sugarcane Tops
About 72 tones of sugarcane tops were collected and allowed to wilt for 4-5 h in the harvesting field itself. The tops were then chopped to a length of 4-5 cm using chaff-cutter and ensiled in silo pits with one per cent urea, 0.5% common salt and two percent molasses on air-dry basis. The value addition was based on the earlier work conducted in this laboratory to assess the precise level of additives (Wilhelmina, 2001). The silo was opened after 60 days of ensiling.

The Bajara-Napiar hybrid (Pennisetum glaucum and P. purpureum) grass was mixed with Alfalfa (Medicago sativa) in the ratio of 1:1.09 in order to match the nitrogen and energy content of SCTS.

Replacement Value of SCTS to GG and its Effect on Reproductive Performance in Crossbred Heifers. Experiment I
A study was carried out for 180 days in eight Jersey X Sindhi crossbred heifers (Bos tourus x Bos indicus) of 13-19 months age with a mean body weight of 158.75±13.27 kg. The animals were randomly distributed into two treatment groups of four animals each. The heifers were individually penned giving adequate floor space in a well-ventilated shed. The heifers in the one group received ad libitum of GG while the other group received ad libitum of SCTS. Both groups received one third of dry matter requirement as concentrate. The concentrate mixture was formulated with maize (14%), damaged wheat (16%), Wheat bran (21%), rice bran (20%), groundnut cake (13 %), Sunflower oil cake (10%), molasses (2%), urea (2%) and mineral mixture (2%) so as to contain 22% of crude protein and 70% of total digestible nutrients. Records were maintained on feed offered, left over and reproductive performance traits like occurrence of oestrous cycle, duration of oestrum, intensity of oestrum and conception. The intensity of oestrum was measured using a scorecard outlined by Rao and Rao (1981) and Callesen et al. (1993). The conceived animals were continuously fed with respective rations up to third month of pregnancy to observe incidence of any early abortion.

Replacement Value of SCTS to GG in Advanced Stage of Pregnancy and its Effect on Post Partum Milk Yield and Composition in Cows- Experiment II
Eight Jersey x Sindhi crossbred cows (Bos tourus X Bos indicus) in advanced stage of pregnancy (last three months) were randomly allotted to two groups of four animals in each. The housing, feeding and management of the animals were the same as in experiment I. The concentrate mixture was formulated with maize (20%), wheat bran (22%), rice bran (17%), mung chuni (15%), groundnut cake (10%), Sunflower oil cake (12%), molasses (2%) and mineral mixture (2%) so as to contain 17% of crude protein and 65% of total digestible nutrients. The experimental animals were fed with respective rations for a total period of 120 days. Records were maintained on feed / fodder offered, left over, incidence of abortion, birth weight of calf, daily milk yield and milk quality. Milk parameters were studied by collecting the milk samples during the data collection period of 10 days after 8 days post calving. Milk samples were collected at morning and evening milking. These samples were analyzed for fat content by Gerber’s method (BIS, 1977). Solids not fat (SNF) in the milk were calculated using the BIS (1982) formula, SNF = (CLR/4) + 0.25+0.6, where CLR = corrected lactometer reading at 27°C, F =% of fat content of milk. The total solids in milk were calculated by addition of fat and SNF.

Statistical Analysis
The data collected in both the trials was analyzed using paired t-test as per the procedure of Snedecor and Cochhran (1967).

Results

Replacement Value of SCTS to GG and its Effect on Reproductive Performance in Crossbred Heifers. Experiment I
The dry mater intake and reproductive parameters viz. Occurrence of oestrum, intensity of oestrum, duration of oestrum, number of heifers conceived and incidence of early abortion due to feeding of SCTS and GG are presented in Table 1. The dry matter intake kg^-1 metabolic body weight of heifers fed with SCTS was significantly (p<0.05) lower than the heifers fed with GG. Out of four animals in control group, 75% showed the occurrence of oestrum. In heifers fed with SCTS, the occurrence of oestrum was also 75%. In 66.66% of animals fed with either GG or SCTS, the intensity of oestrum was observed as intense (20-30 points) with remaining 33.33% of animals showing moderate (10-20 points) intensity of oestrum. Pregnancy was confirmed in 50% animals in both groups without any incidence of abortion in the pregnant animals during the first trimester of pregnancy.

Replacement Value of SCTS to GG in Advanced Stage of Pregnancy and its Effect on Post Partum Milk Yield and Composition in Cows-experiment II
The data on the dry matter intake, pregnancy and milk yield and composition are presented in Table 2. Similar to the results of experiment I, the daily dry matter intake kilogram- metabolic body size was significantly lower (p<0.05) in cows fed with SCTS (119.72±2.41 g) compared to GG (136.64±4.46). The mean gestation period was 277±5.98 days for cows fed in GG group and 265±8.67 days for cows fed with SCTS. No incidence of abortion was observed in the experimental animals fed in the both groups. The birth weight for calves born to cows fed with SCTS was increased (p>0.05) by 22%.

Table 1:	Dry matter intake and the effect of feeding sugarcane tops silage for 180 days on reproductive traits in crossbred heifers (Mean±SE)
Mean value in a row with different superscripts differ, significantly (p<0.05); Mean of four observations; SE = Standard Error

Table 2:	Effect of feeding sugarcane tops silage to crossbred cows in advanced stage of pregnancy on feed intake, reproductive traits and post partum milk yield and composition (Mean±SE)
Mean value in a row with different superscripts differ significantly, (p<0.05), Parenthesis indicate the total number of observation, SE = Standard Error

The average daily post partum milk yield was did not vary between cows fed with GG and SCTS. The corresponding daily fat corrected milk yield was marginally decreased in cows fed SCTS (Table 2).

DISCUSSION

The significant (p<0.05) reduction in the dry matter intake of SCTS could be attributed to the degree of proteolysis and the concentration of fermentation acids (Steen et al., 1998). Keady and Mayne (2001) reported similar significant reduction in the feed intake with increased level of grass silage in the ration of the cattle.

In spite of significant (p<0.05) lower level of dry matter intake, SCTS did not affect the parameters studied. It could be argued that enhanced absorption and there by the digestibility of fermented volatile fatty acids and microbial protein in ensiled material was responsible to off set the difference in intake.

The duration of oestrum observed in the present study was in agreement with observation of Sood and Nanda (2006) in normal crossbred cows. Similarity in reproductive traits in both the groups is suggestive of no ill effect on the reproductive performance due to feeding SCTS. Gestation period in the advanced pregnant cow experiment was closer to the findings of Rahman and Rahaman (2006). Non-significant variation in the birth weight between GG and SCTS indicates that GG could be replaced by SCTS as pre calving diets had no deleterious effect (Butler et al., 2002; McNamara et al., 2003). However, cows fed SCTS produced calves with relatively higher birth weight than those fed with GG. Indicating the efficacy of utilization of nutrients in SCTS. The birth weight of calves born to cows fed with the SCTS corroborated with the reports of Jesudasan (1979) and Govindarajan (1983) in Jersey crosses.

The milk yield and daily fat corrected milk yield was reduced only marginally in cows fed in cows fed with SCTS. On the other hand no appreciable variation could be observed in the composition of milk from those cows in both the groups. Huhtanen et al. (2003) reported similar results and found more profound decrease in milk fat yield than the milk yield, because milk fat and protein concentrations decreased with increasing lactic acid or total acid concentration in the silage.

It is observed in experiments I and II that on feeding SCTS in spite of reduced dry matter intake, had no adverse effect on the reproductive traits in early as well as late pregnancy in the experimental animals. Replacing the mixed green grass (GG) completely with sugarcane tops silage (SCTS) did not affect the occurrence, intensity and duration of oestrum in crossbred heifers. There was no incidence of early abortion in pregnant heifers on feeding the SCTS. Replacing the GG completely with SCTS did not have any adverse effect on the late pregnancy, birth weight of calves, post partum milk yield and composition. Hence apart from concluding that SCTS can replace GG to serve as alternate fodder source, the myths among the farmers on the incidence of repeat breeding and early abortion on account of feeding the sugarcane tops could also be considered as false.

ACKNOWLEDGMENT

Authors are grateful to the National Bank for Agriculture and Rural Development (NABARD) and Tamil Nadu Veterinary and Animal Sciences University (TANUVAS), Chennai, India, for the financial assistant rendered to carryout this research.