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The Manager - Milk Yields and Health Research

JULY 2018

New Milk Analysis Metrics for Dairy Herd Management

By Dave Barbano, Heather Dann and Rick Grant

New mid-infrared milk analysis metrics have been developed to provide actionable dairy herd management data. New milk analysis metrics are: 1) groups of milk fatty acids [i.e., de novo (DN: C4 to C15), mixed origin (MO: C16:0, C16:1), and preformed fatty (PF: C18 and longer) acids], 2) fatty acid (FA) chain length (expressed as carbon number), 3) FA unsaturation (expressed as double bonds per FA) and 3) estimated blood non-esterified FA (NEFA).
 

Somatic Cell Counts – Using the Magic 200,000 cells/mL Cut-Point to Diagnose Subclinical Mastitis 

By Kathryn Bach and Jessica McArt 

Mastitis is one of the most common and costly diseases facing the dairy industry today. Annually, over $2 billion are lost to mastitis alone, with an average per-case cost estimated at $444. Nearly two-thirds of these economic losses are attributed to the consequences of subclinical infections, which result in decreased milk production, increased discarded milk and lost milk premiums. 

In our study population, results showed that at the 200,000 cell/mL cut-point, composite sampling appeared to have similar effectiveness as quarter sampling to identify subclinically infected animals on a herd level. However, our results also suggest in a large population of first-lactation animals, a high proportion of coagulase negative staphylococci infections, or both, might play a large role in the effectiveness of this cut-point on herds, and optimal cut-points may vary between farms.  
 

Postpartum Ketosis Treatments – Propylene Glycol, Dextrose, or Both? 

By Sabine Mann and Jessica McArt 

In a controlled study of early lactation hyperketonemic cows (defined as BHB concentrations in blood of 1.2 mmol/L and greater), we compared the effects of drenching with PG alone, intravenous dextrose alone, or both in combination, to an untreated control group. Results of this study showed that the combined treatment with dextrose and PG lowered BHB concentrations to the greatest extent during the treatment period compared with dextrose or PG alone. The increase in glucose and insulin concentrations due to intravenous dextrose was short-lived, as was the decrease in NEFA concentrations. Difference in the effects of the treatments on health outcomes, intakes, and milk production could not be described due to the small sample size and short duration of the study. Follow-up studies of a larger scale are planned to compare disease and production effects for these parameters and to assess the economic cost and benefit of each treatment strategy. 
 

Milk Like a Cow, Eat Like a Pig: Developments in Nitrogen Efficiency and Amino Acid Balancing for Dairy Cattle 

By Andrew LaPierre, Ryan Higgs and Mike Van Amburgh 

In the nitrogen nutrition realm of the dairy industry, dietary crude protein is the go-to indicator for the overall nitrogen content within a given ration. But fallacies exist and bias emerges when using crude protein as a proxy for nitrogen status. Because each amino acid has its own percentage nitrogen which makes it up, and the amino acid profile for a given feed or forage may be different from one another, the assimilation of every amino acid into a generalized crude protein can either over or under-predict the nitrogen in a given diet. 

A study conducted in our lab focused specifically on nitrogen efficiency. Four dietary treatments were formulated, varying in the degree of amino acid balancing and overall nitrogen content in the diets. Data from this trial, along with several others, has provided the information to begin calculating optimum amino acid ratios when regressed against the energy content of the diet, much like what is done in swine nutrition. 
 

Strategies to Optimize Dietary Energy in Fresh Cow Rations 

By Sarah LaCount, Mike Van Amburgh and Thomas Overton 

The transition period from pregnancy to lactation is one of great adaptation for dairy cattle, which too often can lead to metabolic disease and consequently subpar performance throughout lactation. After parturition, cattle enter negative energy balance, as DMI is not able to meet nutrient demands for several weeks, and body reserves are mobilized to compensate for these differences. In fresh cattle diets, the use of Rumensin, an ionophore that increases ruminal production of propionate through a shift in rumen bacteria population, has been shown to increase energy balance, decrease body reserve mobilization, and increase milk yield. Another strategy to increase energy density of the diet is use of higher digestibility corn silage hybrids, such as brown mid-rib (BMR) corn silage. BMR corn silage, which has less overall cross linking within the plant structure, typically provides more digestible aNDFom to the cow than conventional corn silage. Feeding BMR through the periparturient period has been shown to increase DMI and milk production in the early lactation period when compared to conventional corn silage. 

To investigate any possible synergism of Rumensin and higher digestibility corn silage, 85 multiparous Holstein cattle were moved to a tie-stall 28 days prior to expected parturition to be enrolled in our study. Cattle were fed a common close-up diet for the first seven days consisting of corn silage, chopped straw, and a grain mix, and assigned to treatment diets at 21 days before calving. 

Cattle fed BMR corn silage performed better overall than those fed conventional corn silage through the transition period. Higher intakes prepartum, as well as higher yield and more favorable circulating blood metabolites in the postpartum period, suggest these cows were in a more positive energy balance than cows fed CON corn silage, likely due to the increased digestible fiber. Cattle fed Rumensin, despite having slightly lower intakes prepartum, had lower circulating BHBA prepartum, as well as lower BHBA and NEFA in the postpartum period. This again suggests that animals were in a better metabolic status. Although we saw 

minimal statistical interactions between corn silage type and Rumensin, both use different strategies to increase the overall energy availability of the cow. The interaction seen in milk yield data suggests a potential synergism between these two strategies. In this vital transition period these strategies, alone or together, can be key to increase overall cow health and productivity through their impacts on energy availability and overall energy balance. 
 

Balancing Dairy Cow Health and Performance: Dietary Fat Supplementation and the Role of Ceramide 

By Joseph W. McFadden 

Fat supplementation of dairy cattle diets is a common practice to increase dietary energy and to thereby enhance milk and milk fat yields. However, the ability of dietary fat supplementation to modulate digestion, metabolism and performance can be influenced by the type of fatty acid (chain length and degree of saturation). 

Ceramide is a type of sphingolipid found in tissues and circulation that is formed by saturated fatty acids, including palmitic acid and the nonessential amino acid serine. Collectively, ceramide has emerged as a novel biomarker for insulin antagonism in dairy cattle and a target for the development of nutritional strategies aimed at modulating nutrient partitioning. Although studies have repeatedly demonstrated the ability of palm fat supplementation to induce ceramide synthesis in dairy cows, ongoing work aims to delineate the ceramide-related effects of very long-chain saturated fatty acids and PUFA that escape biohydrogenation, and the influence of emulsifiers that may enhance palmitic acid digestibility. Moreover, we should consider how palmitic acid-induced ceramide accrual is influenced by dietary energy density, co-supplementation with other fatty acids, level of milk production, stage of lactation, and parity. Unraveling these uncertainties has the potential to optimize fatty acid nutrition in dairy cattle. 
 

What Can Farmers Do to Reduce or Prevent Spores from Entering Raw Milk? 

By Rachel Evanowski and Sarah Murphy 

As demand for low-spore raw milk increases, and with it prospects for premiums, the dairy industry needs evidence-based recommendations to give producers the tools to take advantage of this opportunity. Research by the Milk Quality Improvement Program (MQIP) at Cornell University is aimed at understanding spore sources, farm practices associated with the transmission of spores into raw milk, and providing a set of best practices to producers to achieve low-spore raw milk. 

Recent studies led by MQIP researchers suggest that presence and levels of spores in bulk tank raw milk are associated with 1) bedding practices, 2) housing area characteristics and management, and 3) cow-level factors. Building on these studies, MQIP research is focused on measuring the impact of implementing intervention strategies at the farm level to disrupt the transfer of spores into the bulk tank raw milk from the environment. These strategies involve: training milking staff to focus on teat end cleaning during milking preparation and implementing changes in laundered towel preparation (use of detergent, chlorine bleach and drying). Preliminary analysis of the data collected from this study shows an approximate spore reduction of 40 percent for mesophilic and thermophilic spore counts. 
 

Measuring Fiber Digestibility 

By Michael Dineen and Michael Van Amburgh 

Through neutral detergent chemistry, feed is divided into a soluble fraction that is rapidly and almost completely available, and a fiber fraction that is more slowly and incompletely degraded by microbial enzymes. However, this fiber fraction might contain contaminants, such as starch, protein and ash, that can artificially inflate the concentration of NDF measured. If an artificially high NDF concentration is measured, for example in feeds with high soil contamination, the diet formulation becomes difficult, especially when balancing to low levels of diet NDF concentration. To overcome these issues, David Mertens published a method that included the option of using alpha-amylase, sodium sulfite and correcting for ash contamination and abbreviated aNDFom. Nutritionally, this is the most useful approach as it reduces the unwanted variability and contaminants in the measurement of the cell wall material. 

From the analysis required to quantify the intrinsic plant factors involved in aNDFom digestion we can determine the size of the fast, slow and undigested aNDFom pools and their respective rates of degradation. Within the construct of the CNCPS, this information is integrated with animal factors such as dry matter intake, passage rate, rumen pH and ammonia levels in a dynamic mechanistic approach. The latest version of CNCPS 7.0 has the capability to predict rumen pools of fast, slow and undigested aNDFom over time. These calculations are based on the constant battle between degradation and passage out of the rumen. Such an approach can help forward predict the animal response to variable feed quality, such as this years corn silage inventory. 
 

Reproductive Tools to Improve Dairies 

By Rob Lynch and Julio Giordano 

Opportunities for improvement exists on many dairies in second and subsequent insemination (2nd+) efficiency for lactating cows and age at first calving (AFC) for heifers. Recently completed research by Dr. Julio Giordano, a Cornell University Animal Science Professor, evaluated ways to manage these two components. 

Results from these trials show that herds with good heat detection and weekly re-breeding programs can improve their reproductive efficiency by choosing protocols based on ovarian status. Shortened Resynch protocols can result in a high proportion of cows bred in heat while shortening the interbreeding interval, and improving CR in cows most likely to benefit from progesterone supplementation.

By accounting for breeding program expenses, rearing cost savings and additional first lactation profit, this research provides the dairy industry with a better understanding of the financial impacts of improving AFC with good heifer reproductive management.