Mitigation of subclinical mastitis during early lactation and effects of subclinical mastitis on milk yield, lamb growth, and lamb survival


University of Wyoming


Performance Narrative:
To date, we have completed all sample collections, milk component analysis, and preliminary milk production and lamb performance statistical analysis.


Activities Performed





# Accomplishment/Activity Relevance to Objective


1 - Lambed out 45 ewes during April 2021.  Collected milk samples for future microbial

DNA extraction, milk components (e.g., fat, protein, lactose, solids, etc.), and yield on d 1, 7, 14, 21, 28, 35, 42, 49, 56, and 63 post parturition, along with ewe and lamb body

weights and ewe back fat depth. Collected ewe feces on d 1 post-parturition. Collected lamb rumen fluid on day 7, 28, and 63. Measured litter creep feed intake from day 28 through 63 when lambs were weaned.
All samples associated with future laboratory work have been collected.


Challenges and Developments


# Challenge or Development Corrective Action or Project Change


1 - The mitigation of mastitis during early lactation was removed as a study component.

Additional focus was placed on quantifying the prevalence of subclinical mastitis throughout the entire lactation.


2 - How to measure milk yield to accurately represent daily milk yield without impacting

ewe and lamb behavior and performance. Many things can influence milk yield that we

tried to account for by leaving the building lights on, milking ewes in the same environment where they could see their lambs on the other side of the gates, consistent

milking techniques/technicians.


3 - How to measure creep feed intake. The more experimental units that observations

can be observed for, the more likely to observe statistical significance. Rather than

measuring group intake from 4 or 5 group pens, we measured creep intake for each

ewe’s litter (single or twin-reared lambs). This was labor-intensive setting up more than 40 individual pens to keep the ewe and her lambs with creep feeding areas and required daily manual removal of soiled bedding.


Outcome and Indicator Results to Date


# Outcome/Indicator Quantifiable Results


1 - Milk yield Estimated daily milk yields were measured weekly and adjusted to assume equal production of both udder halves for a 24- hour period.


2 - Milk components and somatic cell count Each milk sample was sent to a Dairy Herd

Improvement Association certified commercial laboratory to measure somatic cell count, milk fat, protein, lactose, ureanitrogen, other solids, and total solids.


Upcoming Activities


# Activities Anticipated  Completion


1 - Preliminary analysis of quantitative data, including identifying correlations and linear regressions of somatic cell count, milk yield and components, creep feed intake, litter size, day of lactation, back fat depth, and ewe/lamb body weight gain/loss.
     January 2022


2 - Extend the hiring of an undergraduate researcher through Summer 2022 who helped collect these samples to begin microbial DNA extraction of milk samples. To maximize cost effectiveness, these samples will be collected from the extreme somatic cell counts

(lowest average, median average, highest average; least and most weekly fluctuation)

       September 2022