Use of RBST to Avoid Impairments in Mammary Gland Development in Early Breeding Heifers

Giulia BerzoiniCosta Leite

It is essential to devise new methods or strategies to overcome mammary gland development’s detriment provoked by early breeding management practices that are adopted as an attempt to reduce the heifer’s unproductive and non-profitable phase. Bovine somatotropin is an inexpensive hormone widely used in some countries as a milk persistency tool and was shown to promote mammary gland development in regular breeding heifers. However, the effect on early breeding heifers is not known. Therefore, the primary goal of this study project is to evaluate the use of rBSTas an alternative strategy to overcome constraints on mammary gland development of Holstein heifers caused by high feeding levels associated with early breeding practices. 36 animals will be split into 3 groups: a positive control receiving placebo injections and being bred at 11 months; a negative control receiving placebo injections and being bred at 14 months; and a treatment group receiving rBSTinjections and being bred at 11 months. All heifers will undergo mammary gland and liver biopsies, mammary gland ultrasounds, blood samplings, and average daily gain evaluations to gather data. Preliminary studies from our group have proven that the use of this synthetic hormone in regularly bred heifers may avoid impairments that would be expected on the mammary gland. We hypothesized that heifers treated with rBSTduring pre-puberty will exhibit improved gland development with an increased proportion of secretory tissue. These results might be used to improve nutritional and management practices for heifers.

Identifying Genomic Regions Associated with Bovine Respiratory Disease in Pacific Northwest Dairy Cattle

Allison Herrick

Bovine respiratory disease (BRD) is one of the costliest diseases within the cattle industry, with both acute and chronic affects among impacted individuals. A multifactorial, multi-pathogen disease, BRD infection is influenced by the genetics of the host. This study examined genetic components associated with susceptibility to BRD among pre-weaned dairy calves. The objective was to use genome-wide association analyses to identify loci associated with BRD. An Efficient mixed model association expedited analyses were performed on 482 genotyped animals and 603,420 SNPs, in addition to health records from three dairies in Washington. A WellcomeTrust threshold of < 1 x 10-5 was required for a moderate association, and a threshold of < 1 x 10-7 was required for a strong association. 195 SNPs identified within 13 chromosomes were moderately associated with BRD, with 12 of these SNPs meeting the threshold for a strong association with BRD. Positional candidate genes included OTUB1, SEMA4D, SLC22A23, and TRIM38. The identified candidate genes control a diverse range of biological functions, including immunological regulation, ion and membrane transport, and pulmonary development. These associated loci and positional candidate genes provide a basis for further research surrounding BRD, with the goal of creating selection tools for producers to reduce BRD incidence.