EFFECTS OF PROTEIN-SOURCE AND LEVEL ON PERFORMANCE OF LACTATING DAMASCUS GOATS IN NEGATIVE-ENERGY BALANCE

Effect of protein source (untreated soybean meal vs. formaldehyde-trea ted soybean meal) at three levels (13, 15 and 18% CP in the concentrat e mixture, DM basis) on milk yield, milk composition, body weight (BW) change and rumen metabolites of 48 lactating Damascus goats was studi ed. Animals were fed to meet maintenance energy requirements and 60% o f milk production energy requirements. Animals were housed and fed con centrates in groups of two animals, whereas roughage was offered to a single group per treatment. Goats consumed 0.175 kg barley hay and 0.2 69 kg barley straw/d. There were no significant effects of protein con centration or source on milk yield, milk composition, BW change and ru men metabolites. Protein source did not affect rumen NH3-N and total V FA concentration, but dietary protein level had a significant effect ( P<0.001) on rumen NH3-N concentration. When all animals were changed t o a higher feeding level at the end of the 42-d trial, milk yield was increased slightly; most of the extra feed allowance was directed towa rds weight gain. Formaldehyde (HCHO) treatment of soybean meal reduced degradability of DM (21 percentage units) and CP (19.2 percentage uni ts) in the rumen. It was concluded that reduction in energy supply bel ow requirements will result in considerably reduced milk yield, and th at supply of a protein supplement of low degradability will not allevi ate reduction in milk yield through greater mobilization of body reser ves and subsequent use for milk production.