Masters Theses

Date of Award

8-2021

Degree Type

Thesis

Degree Name

Master of Science

Major

Animal Science

Major Professor

Gina M. Pighetti

Committee Members

Elizabeth Eckelkamp, Oudessa Kerro Dego

Abstract

The objective of this study was to assess the efficacy of a nutritional supplement (Omnigen-AF®; OG) proven to improve immune function, fed during the dry period through early lactation in enhancing selective dry cow therapy (SDCT) impacts on milk production, somatic cell count (SCC), and intramammary infections (IMI) of multiparous Holstein cows. We hypothesized that feeding OG beginning in the dry period through 28 days in milk (DIM) would increase milk yield, reduce somatic cell count and IMI rate while reducing antibiotic use through a SDCT program. To test our hypothesis, 113 multiparous pregnant Holstein cows were enrolled and alternately assigned at dry-off to either OG (n = 52) or control (CON, n = 61) treatments. Efforts were made to balance the number of cows and quarters receiving antibiotics across treatments. Quarter milk samples were taken 7 d before dry off to assess SCC and microbiological status used to make selective antibiotic treatment decisions. At dry off quarters that were considered uninfected SCC was again checked, if >150,000 SCC/ml of milk then quarter was treated with antibiotics. Internal teat sealant was used on every quarter regardless of antibiotic infusion. Both OG and CON (placebo) supplements were fed individually once per day at a rate of 60 g/d per head from dry off through 30 DIM by restraining in a headlock system. Consumption of grain mixture was observed and recorded daily. Milk samples and yield were taken approximately 3.7 ± .1 d after calving, and 7, 14, and 28 d into lactation to assess SCC and microbiological status. Our results indicated that cows supplemented with OG had greater (2.4 ± 1.1 kg) milk production compared to CON, while SCC did not differ between treatments. The selection criteria for use of antibiotic therapy resulted in 61.5% reduction in antibiotics over both treatments compared to using antibiotics in every quarter. Quarter-level IMI indicated no increased risk of new IMI over the dry period with the reduction of antibiotics use. In conclusion, supplementing an immunomodulatory feed additive in enhancing SDCT with an internal teat sealant to dry and early lactation dairy cows was associated with increased milk production and reduction of antibiotics with no effect on risk of new IMI over the dry period.

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