Administration of internal teat sealant in primigravid dairy heifers at different times of gestation to prevent intramammary infections at calving

Abstract

Intramammary infections (IMI) are common in primigravid dairy heifers and can negatively affect future milk production. Bismuth subnitrate-based internal teat sealants (ITS) have been used to prevent prepartum IMI in dairy heifers by creating a physical barrier within the teat, preventing pathogens from entering the gland, though determination of when to administer ITS in heifers has yet to be investigated. The objectives of this study were to determine if administration of ITS in primigravid heifers reduced the odds of IMI at calving and if administration of ITS at different stages of gestation (75 vs. 35 d prepartum) affected the odds of IMI at calving. A total of 270 heifers were used at a single farm. One quarter of each heifer was randomly chosen to be aseptically sampled and administered ITS 75 d prepartum (ITS75), another quarter of each heifer was sampled and received ITS 35 d prepartum (ITS35), whereas the remaining 2 quarters of each heifer served as control quarters (CON) and were not sampled before calving. Within 12 h of calving, aseptic colostrum samples were collected from all quarters to determine quarter infection status. When an IMI was caused by mastitis pathogens other than non-aureus staphylococci (NAS), CON quarters were 3 times [95% confidence interval (CI): 1.4-6.3] and 2.5 times (95% CI: 1.2-4.9) more likely to be infected at calving than ITS75 and ITS35 quarters, respectively. For IMI with NAS, CON quarters were 5.8 (95% CI: 3.2-10.5) and 6.4 (95% CI: 3.4-12.0) times more likely to be infected than ITS75 and ITS35 quarters, respectively. Odds of IMI at calving was similar between ITS75 and ITS35 quarters for both NAS (odds ratio = 0.9) and other pathogens (odds ratio = 1.2). Results indicate that ITS administration at either 75 and 35 d prepartum reduced IMI prevalence at calving in primigravid dairy heifers. Farm specific factors may influence prevalence and timing of heifer IMI and earlier administration of ITS provides an extended period of protection for the developing gland.

Characteristics of mammary secretions collected from infected and uninfected primigravid dairy heifer mammary glands

“…Heifers were housed on a sawdust-bedded open pack with a concrete feed alley outfitted with headlocks. During the study period, heifer quarter-level IMI prevalence was 26% at 75 d prepartum, 28% at 35 d prepartum, and 30% at parturition for primiparous cows (Larsen et al, 2021). The predominant causative agents in quarters prepartum were NAS, particularly Staphylococcus chromogenes (20% IMI prevalence) and Staphylococcus simulans (1.9% IMI prevalence); environmental streptococci infected 2.4% of quarters, and gram-negative IMI prevalence was 1.1%.…”

“…Heifer secretion samples were collected from 270 heifers at the STgenetics Ohio Heifer Center (South Charleston, OH) from June 30 to October 23, 2020, as part of another study (Larsen et al, 2021). No sample size calculation was conducted, and all quarters sampled in Larsen et al (2021) were included in the present study. The farm operates with approximately 3,000 heifers on site.…”

“…This included approximately 5% of the heifers that we intended to enroll in the study. Further explanation of sampling protocols can be found in Larsen et al (2021). At 75 d before expected calving date, 1 quarter of each enrolled heifer was randomly selected and aseptically sampled; these samples were denoted "75 d prepartum" (75PP) secretions.…”

“…Enrolled heifers were sampled once more at 35 d prepartum from a different quarter; these samples were denoted "35 d prepartum" (35PP) secretions. The remaining 2 quarters of each heifer were not sampled because they were serving as unsampled control quarters in a separate study (Larsen et al, 2021).…”

“…Quarters were sampled as previously detailed by Larsen et al (2021). Briefly, teats were disinfected by fully immersing the teat in a commercial iodine teat disinfectant (Teat-Kote 10/III, GEA Farm Technologies), which remained on the teat skin for 5 to 10 min; the disinfectant was removed with a single-use paper towel, and the teat was immersed once more in the same disinfectant that remained on the skin for 30 s Larsen et al: PRIMIGRAVID HEIFER MAMMARY SECRETIONS before being wiped away with a single-use paper towel.…”