Abstract
This study evaluates the effects of fresh cassava root (CR) and a solid feed-block containing sulfur (S-FB) on fermentation in the rumen, feed utilization, milk yield, and milk composition in lactating dairy cows. Four Holstein-Friesian cows with 470 ± 50.0 kg body weight (BW), 10 ± 2 kg day−1 average milk yield, and 112 ± 15 days-in-milk were studied. A 2 × 2 factorial combination was arranged in a 4 × 4 Latin square design to evaluate the treatment-related effects. The treatments were obtained from a combination of two factors: (1) levels of CR at 10 g kg−1 BW (CR-1) and 15 g kg−1 (CR-1.5) and (2) levels of sulfur supplementation in solid feed-block at 20 g kg−1 (S-FB-2) and 40 g kg−1 (S-FB-4). The results showed that CR and S-FB had no interaction effect on feed intake, digestibility, fermentation, blood metabolites, milk yield, or its composition. Feeding CR up to 15 g kg−1 of the BW significantly increased (p < 0.05) the milk fat concentration while it decreased (p < 0.05) the somatic cell count. The S-FB-4 of the sulfur significantly (p < 0.05) increased the acid detergent fiber when compared with the S-FB-2 of the sulfur. CR could be fed up to 15 g kg−1 of BW with S-FB containing high sulfur (40 g kg−1) in dairy cows without a negative impact.
Highlights
Fresh cassava root (CR) is high in digestible carbohydrates, mainly starch, and is considered the main energy source for ruminants
Various approaches to achieving sulfur utilization, to reduce hydrogen cyanide (HCN) toxicity, have been conducted, such as adding elemental sulfur into a fermented total mixed ration (FTMR) containing CR for dairy cows [1,5], adding sulfur to a concentrate of cassava hay and foliage fed to dairy cows as a roughage source [4], and adding sulfur to a pellet diet with CR supplementation [6]
The concentrate was formulated to contain 167 g kg−1 DM of crude protein (CP) to ensure the nutrient requirement for cows according to National Research Council (NRC) [20] and a cassava chip was used as an energy source
Summary
Fresh cassava root (CR) is high in digestible carbohydrates, mainly starch, and is considered the main energy source for ruminants. Feeding CR to ruminants is limited in practice due to the highly toxic hydrogen cyanide (HCN) content of the roots. Sulfur has been studied and reported to reduce the cyanide toxicity [1,2]. HCN can be rapidly detoxified by the enzymes rhodanese and β-mercaptopyruvate sulfurtransferase, which are released by rumen microbes [3]. Various approaches to achieving sulfur utilization, to reduce HCN toxicity, have been conducted, such as adding elemental sulfur into a fermented total mixed ration (FTMR) containing CR for dairy cows [1,5], adding sulfur to a concentrate of cassava hay and foliage fed to dairy cows as a roughage source [4], and adding sulfur to a pellet diet with CR supplementation [6]
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