Date of Award

Winter 2019

Project Type


Program or Major

Animal and Nutritional Sciences

Degree Name

Master of Science

First Advisor

Peter S. Erickson

Second Advisor

Andre F Brito

Third Advisor

Kayla M Aragona


Much of the research on sodium butyrate (SB) has been conducted with pre-ruminant calves. Previous research with post-weaned calves was shown to be beneficial. The objective of this study was to compare sodium butyrate to monensin (MON) on the growth, digestibility, and health of post-weaned heifers. Forty Holstein dairy heifers with a mean age of 84.2 d ± 1.2 d (mean ± SD) and average body weight (BW) of 99.78 kg ± 10.77 (mean ± SD) were housed in a naturally ventilated freestall barn. Heifers were blocked by birth date and randomly assigned to 1 of 4 treatments in a completely randomized block design: (1) 100 g of soybean meal carrier (control; CON); (2) 0.75 g SB/kg of BW + carrier; (3) 1 mg monensin/kg of BW + carrier; (4) monensin + 0.75 g SB per kg of BW (MSB). Data were statistically analyzed using single degree of freedom contrasts evaluating CON vs. all other treatments; SB vs. MON; and SB and MON vs. MSB. Treatments were top-dressed and hand-mixed into a total mixed ration (TMR) once daily. Heifers had free access to water. Amount of orts and feed offered to each heifer was measured daily. Feed and orts samples were frozen at -20°C for future analysis. Orts samples were taken daily and subsampled for later DM determination, while TMR samples were taken weekly and composited monthly for later DM and nutrient analysis. Initial BW, heart girth, paunch girth, and body length were measured before the start of the study and every week thereafter during the 12 wk trial (168 d old). Blood samples were obtained, and glucose and ketone concentrations were determined prior to the start of treatment and weekly until the conclusion of the study. Fecal grab samples were taken prior to treatment and every week from each heifer for coccidia counts. Apparent total-tract nutrient digestibility samples were taken in two different phases: 21 d on study until 27 d, and again at 63 d until 69 d. Apparent total tract nutrient digestibility was taken during this time and determined through acid-insoluble ash. Additives had a positive effect, tending to increase average BW and final BW. Any additive tended to increase heart girth, while MSB tended to be greater than either SB and MON. No other effects were seen on skeletal growth. Daily dry matter intakes (DMI) were increased in the diets containing additives as compared to control. Dry matter intake values were 4.00, 4.47, 4.16, and 4.46 kg/d for CON, SB, MON, and MSB, respectively. Feed efficiency (FE) was improved in MON supplemented heifers as compared to SB. Fecal samples from each heifer indicated the presence of coccidia. Compared to control, additives decreased the number of coccidian oocysts present in feces. Monensin and SB treatments tended to have greater plasma glucose as compared to MSB. Average blood ketone concentrations were greater with any additive compared to CON, in SB vs. MON, and in MSB as compared to SB and MON. During the week 3 digestibility period, DMI tended to be greater in heifers fed SB when compared to MON, as well as heifers fed MSB when compared to SB and MON. Apparent total tract digestibility of DM, NDF, ADF, Hemicellulose, OM, and fat digestibility showed no differences among treatments. Starch digestibility was increased in heifers fed the combination diet when compared to SB and MON. During the week 9 digestibility period, DMI, along with apparent total tract digestibility of DM, CP, ADF, Hemicellulose, Starch, OM, and fat digestibility were not different among treatments. Neutral detergent fiber digestibility tended to be greater in control diets when compared to any additive. Overall, additive supplementation offers positive results in growth performance, digestive functions, and improvement in overall health.