Culled sweet potato can effectively replace cassava chips for lactating dairy cows in tropical dairy production

The aim of this study was to evaluate the effects of replacing cassava chips with culled organic sweet potato in concentrate diets on feed intake, rumen fermentation characteristics, estimated methane production, milk yield, and milk composition in dairy cows. Four multiparous Holstein Friesian cows (4 years of age; 325 ± 15 kg initial body weight) were assigned to a 4 × 4 Latin square design. The concentrate diets were formulated by progressively replacing the cassava chip fraction with culled organic sweet potato at levels of 0%, 33.3%, 66.6%, and 100%. Cows were fed concentrate twice daily (05:00 and 16:00 h) according to a concentrate-to-milk ratio of 1:2, while rice straw, minerals, and water were offered ad libitum. The experiment consisted of four 21-day periods. Feed intake was not affected by dietary treatments. Likewise, ruminal pH, temperature, ammonia-N, and blood urea nitrogen were not influenced by treatments. Total volatile fatty acid concentration decreased linearly at the highest replacement level (P < 0.05), whereas acetate, propionate, butyrate, and the acetate-to-propionate ratio were not affected. Estimated methane production decreased linearly with increasing levels of sweet potato inclusion (P < 0.05). Milk yield, fat-corrected milk, energy-corrected milk, protein, and solids-not-fat were not affected by dietary treatments. However, milk fat, total solids, and lactose increased with increasing sweet potato inclusion (P < 0.05). In conclusion, replacing cassava chips with culled organic sweet potato had no adverse effects on feed intake, rumen fermentation, or milk production, while reducing estimated methane production and improving selected milk composition parameters in lactating dairy cows.