EFFECT OF FORMALDEHYDE TREATMENT AND FEEDING REGIME OF DIETS FOR CROSSBRED FRIESIAN COWS ON MILK PRODUCTION AND MICROBIOLOGICAL STATUS

Abstract

SUMMARY Sixteen lactating crossbred Friesian cows, in early lactation, were divided into 4 groups using 4 x 4 Latin square design throughout 30 days experimental period. Rations used consisted of berseem hay (BH) or whole corn silage (WCS) as a source of roughage and concentrate feed mixture either untreated or formaldehyde-treated. The ratio of roughage to concentrate was 40 to 60 on the basis of dry matter. Before the commencement of the experiment, the experimental rations were evaluated on sheep for their digestibility and nutritive values. Results indicated significant (P<0.05) increase in digestibility coefficients of organic matter (OM) and nitrogen-free extract (NFE) of the whole corn silage (WCS) compared to BH rations. The same effect was found for the nutritive value in terms of digestible energy (DE) and metabolizable energy (ME) of WCS. On the other hand, a significant effect was recorded on digestible crude protein (DCP) values for animals when received BH rations compared to those received WCS. Formaldehyde treatment of concentrate feed mixture (CFM) significantly increased the CP digestibility coefficients and DCP% as well. No significant differences were recorded for other nutrients digestibility coefficients and/or the feeding values of the tested rations. Yield of 4% fat corrected milk (FCM) was improved by 8.3% for cows fed on formaldehyde-treated concentrate feed mixture (F-CFM) than those fed untreated ones. Milk component yields were significantly higher in case of formaldehyde treated group than untreated corresponding. Residual formaldehyde levels in milk from cows fed F-CFM found to be negligible. The microbiological examination included nine pathogenic bacteria namely E. coli, Shigella spp., Salmonella spp., Proteus spp., Yersinia spp., Brucella spp., Staphylococcus spp. and Enterococcus spp. besides fecal colifoms and total bacterial count. In addition, some mesophilic and thermophilic members of lactic acid bacteria as useful and naturally occurring microinhabitants in milk were also examined in the produced milk. The obtained milk was also used for making yoghurt to examine the effect of the residual formaldehyde on the yoghurt characters such as pH, acidity, fats, total solids and specific gravity. Results showed that Proteus spp. exhibited the highest decrease percentage (58.91) followed by Enterococcus spp. (52.43). E. coli and Shigella spp. exhibited decrease equal to (49.93) and (49.91), respectively. Streptococcus lactis showed the