Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy and Food Science

First Advisor

Prafulla Salunke


Our objective was to determine the effects of isoacids (ISO; IsoFerm, Zinpro Inc.) on the lactation performances, feed efficiency, and milk fatty acids (FA) profile of Holstein cows under 2 forage neutral detergent fiber (NDF) levels (FL). The study was designed for a 10-wk long (including 2-wk for covariate) randomized complete block design. Sixty-four mid-lactating Holstein cows [662± 71 kg body weight, 119 ± 51d in milk (DIM), 2 ± 0.9 parity] were blocked by parity, DIM, and prior milk yield (MY) for multiparous cows or genetic merit for primiparous cows. Cows were randomly assigned to 1 of the 4 diets (n = 16 per treatment), which were arranged as 2 × 2 factorial, with 2 FL containing 16.6%(LF) and 20.7% forage NDF (HF) without (WIA) or with ISO (IA, Isobutyrate- 40 g/d per cow). Diets were formulated to meet NASEM (2021) requirements containing similar crude protein (16.5%), NDF (26.4% LF, 28% HF), and net energy for lactation (1.72 Mcal/kg DM). Dry matter intake (DMI) and MY were recorded daily, and milk composition were analyzed weekly. Data were analyzed in R using lme4, where the final model included wk., FL, ISO, and FL × ISO as fixed effects and block as a random effect. The ISO did not affect DMI, a greater DMI was observed in LF than HF (27.8 vs. 25.95 ±0.81 kg/d, P


South Dakota State University

Available for download on Monday, December 15, 2025



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