Substitution effect of protein source with tea waste on productive performances and ruminal fermentation in crossbred Saanen lactating goats

Tea waste (TW) has a protein content of approximately 30% and the potential to replace other protein sources. However, the effect of dietary TW supplement is still ambiguous. The objective of this study was to investigate the effect of three levels of a dietary TW supplement on the performances and physiological changes in goats. Nine multiparous crossbred Saanen lactating goats were arranged in three replicates of a 3 x 3 Latin square. The three groups of goats were fed with 0, 5, or 10 by weight [wt%] dry matter [DM] basis TW, respectively, for a 21-day period. All diets were a total mixed ration (TMR) containing a 40:60 (DM basis) ratio of concentrate: roughage. The goats were weighed at 15 and 21 days. Faeces and urine were collected during the last 7 days of each period. The TW addition had no effect on the DM intake (DMI), DMI% and body weight. The milk protein content in goats on a 10 wt% TW diet was significantly higher (p < 0.05) than that of goats on the other diets. The milk lactose of both TW diets significantly decreased when compared to the control diet (p < 0.01). Goats with 5 and 10 wt% TW tended to decrease digestibility of crude protein (p = 0.10). There were no changes in the DM digestibility, blood glucose, blood urea nitrogen, triglyceride, total protein, ruminal pH, ammonia-nitrogen, total volatile fatty acids, acetic acid (A), propionic acid (P), A:P ratio, nitrogen balance, allantoin excretion and methane emission among treatments. Diets with 5 or 10 wt% TW (DM basis) could be used to replace other plant protein sources.