Review of Tri-State Dairy Nutrition Conference: highlights

The 29thTri-State Dairy Nutrition Conference was held virtually April 19-21, 2021. The conference is organized by leadership of Extension and the Department of Animal Sciences at: Michigan State University, Purdue University, The Ohio State University, and allied industry personnel.

Minimizing Inflammation in Transition Cows

Dr. Barry Bradford, Michigan State University

Haptoglobin is a common blood biomarker, produced by the liver, used to detect inflammation. Haptoglobin concentration can rise due to oxidative stress, inflammatory signals from the immune system, or signs of infectious agents. For example, after calving cows experience an inflammation wave, however the length and severity of this “wave” can vary among cows, ranging from a couple days to weeks. Some animals may possibly never fully recover. A study administering a nonsteroidal anti-inflammatory drug (NSAID), Banamine (flunixin meglumine), several hours before calving and again in the day after calving resulted in high stillbirth rates (26.5% vs. 5.3% in controls). To avoid the threat of stillbirths, a follow up trial administered flunixin 2h and 24h after calving. Unfortunately, results indicated a 2.6-fold increase in retained placenta risks thus provoking greater risks of metritis (Newby et al., 2017).

This suggests that not all inflammatory signals are negative; in fact, these signals are important for recovery and are responsible for muscle contractions that assist in expelling the placenta. These results demonstrate that blocking inflammation signals by using NSAIDs can have detrimental impacts on the parturition process. On the other hand, many studies have proved negative consequences in cows with relatively high blood biomarkers for inflammation in early lactation. One question that needs further research is how does the inflammation wave around parturition effect long-term outcomes. Dr. Bradford hypothesizes that cows that can resolve inflammatory signals in the first 3-4 days of lactation may experience improved production, reproduction, and health outcomes during the remaining lactation compared to cows that had prolonged inflammatory signals after calving.

Variability in MUN Data

Dr. Kristen Reed, Cornell University

Milk Urea Nitrogen (MUN) is a useful measure for monitoring protein metabolism and nitrogen efficiency on dairy farms. Most farms utilize bulk tank MUN, but individual and/or pen-level MUN results would allow for more precise monitoring. Previous research highlighted variation in precision and accuracy of commercial MUN testing, raising questions about the utility of this measure. The data in this presentation showed that repeatability in commercial labs for MUN improved compared to previous research. Reproducibility values across lab is expected to be within ±1.6 mg/dL of the true MUN value. Repeated sampling within a lab is expected to be within ±1 mg/dL. The mid-infrared (MIR) spectroscopy analysis used by commercial labs tends to over predict MUN at lower levels (˂12.8 mg/dL) and under predicts MUN at higher levels (˃12.8 mg/dL).This systematic bias indicates that there is still a need for improvement in MIR methods. The recommended target for MUN is 8 to 12 mg/dL. Even under the same dietary conditions and lactation period, MUN for an individual cow is expected to vary by at least 1.45mg/dL from day to day.

Impact of Subclinical Hypocalcemia on Dairy Cattle

Dr. Rafael C. Neves, Purdue University

Recent research has focused on identifying subclinical hypocalcemia (SCH) based on blood Ca level. Typically, Ca level decreases around calving and recovers in the next few days. The shape of this curve might be related to associated effects of SCH. A large study including 1,453 cows distributed over 5 herds associated low postpartum plasma tCa with negative health events (Retained placenta; RP, Displaced Abomasum; DA, and clinical mastitis), 60 DIM culling risk, reduced pregnancy at 1st service, and reduced milk production across the first 9 Dairy Herd Improvement Association (DHIA) tests. Level of blood tCa within the first 4 to 12h of parturition in multiparous cows had no association with RP, metritis, clinical mastitis up to 60 DIM, or pregnancy to 1st service. For primiparous cows, there was no association of postpartum plasma tCa concentration with culling risk or lower milk production. This study discovered low blood tCa≤7.4 mg/dL within 12h of parturition had increased risk for DA diagnosis. However, lower tCa (≤7.8 mg/dL) in multiparous cows was associated with greater milk production. Other studies from Germany and Texas saw similar results of lower blood tCa and increased milk. Another study, conducted by Neves et al., looked at associations between plasma tCa concentration in the first 4 DIM with disease and milk production and found that associations were dependent on parity. Greater risk for metritis (diagnosed by the farm) in primiparous cows was observed with blood tCa of ≤8.6 mg/dL (2-4 DIM). Second parity cows at 2 DIM with blood tCa ≤7.9 mg/dL and ≥ 3 parity cows at 4 DIM with tCa plasma concentration of ≤8.8 were associated with greater risk of metritis and DA.

A drop and quick rebound in blood tCa around calving is normal. Cows that do not drop in Ca concentration are deemed the “average cows” and the delayed and persistent SCH cows are the ones that need to be monitored due to greater risk of disease within 60 DIM. If blood Ca is measured for screening of SCH time of sampling is relevant. For primiparous cows 2 DIM is recommended for multiparous cows 1 and 4 DIM is recommended. If 1 sample is desired 4-7 DIM is recommended. To compare results and use tCa level as intervention measure time of sampling after calving should be consistent.

Advancements in Dairy Nutrition over the Past 30 Years

Dr. Bill Weiss, The Ohio State University

Through better nutrition and production understanding over the past 30 years, milk production has notably increased. With improved knowledge of vitamin and mineral nutrition today, the industry experiences reduced health issues with more emphasis on the use of nutrition for enhanced animal health, not just milk production. Energy metabolism research over the last 3 decades has greatly improved industry knowledge. This, in addition to computing power, has led to more efficient diets through more advanced ration evaluation and formulation software, better predicting animal performance. Protein has moved from crude protein to metabolizable protein (MP) to formulating for specific amino acids, lowering overall diet cost while increasing milk protein yields. To continue to be a competitive contributor to the human food supply the dairy industry must continue to improve and stay proactive.

Reviews of highlighted topics courtesy of CSA Animal Nutrition.