Browsing by Author "Clay, John S."

Now showing 1 - 2 of 2
  • Milk production of Holstein dairy cattle that were conceived in winter or summer months
    Stallings, Jon; Clay, John S.; Rhoads, Michelle (Virginia Tech, 2016)
    This dataset contains the milk production records (mature equivalent milk, kg) of Holstein dairy cows in the United States during their first lactation. These records were obtained from dairy farms in three states (Georgia, Florida and Texas) from 1999 to 2011. For each production record, the season in which the cow calved is indicated. Winter encompasses the months of December, January and February; spring includes March, April and May; summer includes June, July and August; fall includes September, October and November. Cows included in this dataset were either conceived during summer (indicated as "1" in the HSCONCP column) or winter (indicated as "0" in the HSCONCP column). This dataset was anonymized to ensure privacy of the dairy producers. For a full dataset, interested parties should contact Dairy Records Management Systems, North Carolina State University, 313 Chapanoke Road, Suite 100, Raleigh, NC 27603 (Attn: Dr. John S. Clay, Director, john_clay@ncsu.edu).
  • Thumbnail Image
    Periconceptional Heat Stress of Holstein Dams Is Associated with Differences in Daughter Milk Production and Composition during Multiple Lactations
    Brown, Britni M.; Stallings, John W.; Clay, John S.; Rhoads, Michelle (PLOS, 2015-10-23)
    Heat stress at the time of conception affects the subsequent milk production of primiparous Holstein cows; however, it is unknown whether these effects are maintained across multiple lactations. Therefore, the objective of the current study was to examine the relationship between periconceptional heat stress and measurements of milk production and composition in cows retained within a herd for multiple lactations. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records included milk production data and milk composition data from over 75,000 and 44,000 Holstein cows, respectively, born between 2000 and 2010 in Florida, Georgia, and Texas. Conception dates were calculated by subtracting 276 d from the recorded birth date. Records for cows conceived within the months of June, July, and August were retained as heat stress conceived (HSC) cows; cows conceived within the months of December, January, and February were retained as thermoneutral conceived (TNC) contemporaries. Adjusted 305-d mature equivalent milk, protein percent and fat percent were evaluated with a mixed model ANOVA using SAS. Milk production was significantly affected by periconceptional heat stress. When a significant difference or tendency for a difference was detected between the HSC and TNC cows, the TNC produced more milk in all but one comparison. The advantage in milk production for the TNC cows over the HSC cows ranged from 82 ± 42 to 399 ± 61 kg per lactation. Alterations in fat and protein percentage were variable and most often detected in first lactations (first > second or third). Overall, the most striking result of this study is the consistency of the relationship between HSC and milk production. The nature of this relationship suggests that heat stress at or around the time of conception impairs cow milk yield throughout her lifetime.