Effect of raw or roasted whole soybeans on early lactational performance and ruminal and blood metabolites in Iranian cows

Abstract

SUMMARYThe current study evaluated responses of early lactation Iranian Holstein cows to feeding roasted whole soybeans (SB) plus cottonseed meal (CSM), raw SB plus CSM and soybean meal (SBM) plus cottonseed (CS) in diets with lucerne hay and maize silage as the primary forage source. Treatments consisted of a total mixed ration that included 387 g forage/kg, supplemented with: (1) 120 g roasted SB/kg and 82 g CSM/kg, (2) 120 g raw SB/kg and 82 g CSM/kg, or (3) 120 g SBM/kg and 82 g CS/kg on a dry matter (DM) basis. Diets were offered to 14 multiparous Holstein cows (body weight=617·0 kg, days in milk=16·9) that were assigned randomly to one of three experimental diets for a 45-day trial. Dry matter intake (DMI) was significantly higher for the roasted SB plus CSM diet than for the raw SB plus CSM diet but the difference between the SB plus CSM diets and SBM plus CS was not significant. Yields of milk and 35 g fat-corrected milk (FCM)/kg and milk fat were significantly higher for the roasted SB plus CSM diet than for raw SB plus CSM and also for the SB plus CSM diets than for SBM plus CS. Milk protein concentration was significantly increased by about 2·0 g/kg by the SBM plus CS diet, but milk protein yield was the same for cows fed SBM plus CS, roasted SB plus CSM and raw SB plus CSM diets. Rumen ammonia N, plasma urea N (PUN) and milk urea N (MUN) concentrations were lower when the roasted SB plus CSM diet was fed. Ruminal pH and plasma glucose and β-hydroxybutyrate concentrations were not affected by dietary treatments. Plasma concentrations of essential amino acids (EAA), except Leu and Phe, were higher in cows fed the roasted SB plus CSM diet than in those fed raw SB plus CSM. The cows fed the SBM plus CS diet had the same concentrations of EAA, except Phe, as cows fed SB plus CSM diets. For diets based on lucerne hay and maize silage as the primary forage source, roasting of SB provides additional benefits over raw SB.