Effect of formaldehyde-treated sunflower meal on the milk production of grazing dairy cows

Abstract

Forty-five Friesian cows grazing kikuyu pastures in the first 3 months of lactation were fed pasture alone or pasture supplemented with cracked barley or cracked barley mixed with sunflower meal untreated or treated with 0.5 or 0.7% formaldehyde. All supplements were isoenergetic and differed only in the level of formaldehyde treatment of the protein meal. The experimental rations were given for 8 weeks. The milk production of cows fed sunflower meal treated with 0.5% formaldehyde was significantly higher (P.< 0.05) than that of cows fed either barley or untreated sunflower meal and it was suggested that the level of formaldehyde added to protein meals may be important for optimum responses. The feeding of untreated sunflower meal did not significantly increase the protein content of milk above that of the pasture-fed control group. The feeding of barley and sunflower meal treated with both levels of formaldehyde significantly increased the protein content of milk above that of controls (P.< 0.05). The fat content of milk from cows receiving supplements did not differ significantly between treatment groups, but all were significantly lower than from cows in the control group fed pasture (P.< 0.05). All supplemented groups gained weight over the period of the experiment whereas the pasture-fed control group lost weight. Pasture intake of individual cows was estimated with controlled release chromic oxide capsules. The rate of substitution of pasture by supplement was 0-16 kg/kg concentrate eaten and this is below the rates observed for cows grazing temperate pastures.