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

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.

Effects of supplemental dietary biotin on performance of Holstein cows during early lactation.

This study determined the effects of supplemental dietary biotin (0, 10, or 20 mg/d) on performance of Holstein cows (n = 45; 18 primiparous and 27 multiparous). Treatments started at 14 d prepartum and continued until 100 d in milk (DIM). Blood samples were taken at 14 d prepartum, and blood and milk samples were taken at calving, and 30, 60, and 100 DIM. Dry matter intake during lactation was not different across treatments (19.7 kg/d). Milk production linearly increased with biotin supplementation (36.9, 37.8, and 39.7 kg/d for 0, 10, and 20 mg/d of supplemental biotin, respectively). Biotin supplementation did not affect milk fat and true protein percentages or fat yield but linearly increased true protein yield. Supplemental biotin increased concentrations of biotin in plasma and milk at all time points. Concentrations of biotin in plasma and milk (colostrum) at calving were higher than at other time points for cows fed supplemental biotin. In an ancillary experiment, plasma biotin concentrations were not as high when cows were fed 20 mg/d of supplemental biotin for 14 d during the middle of their dry period as when cows were fed 20 mg/d of biotin for the last 14 d of gestation. This suggests that events associated with parturition altered plasma biotin concentrations. Plasma concentrations of glucose, insulin, nonesterified fatty acids, and molar proportions of ruminal volatile fatty acids were not affected by biotin supplementation. Biotin supplementation had no effect on change in body weight or condition score. Supplemental biotin linearly increased milk and protein yields, however, the mode of action that caused these increases was not determined.