Welcome to latest Dairy Research from March! The Dairy Research Bulletin delivers a brief synopsis of the most current Human, Animal, and Environmental dairy research that is going on in the World, and also that which is of special interest to California dairy producers and consumers alike. 

If you would like to peruse the most pertinent dairy research from months past, then visit the Dairy Research Bulletin Archive


Selected Publications on Animal Health, Food Safety, and Sustainability

Greenhouse gas emissions and energy use associated with production of individual self-selected US diets. Martin C Heller, Amelia Willits-Smith, Robert Meyer, Gregory A Keoleian, and Donald Rose. Environmental Research Letters, Volume 13, Number 4. March 20, 2018.

  • Human food systems are a key contributor to climate change and other environmental concerns, including climate change, biodiversity loss and land and freshwater degradation. Repeated projection studies have shown that closing global yield gaps through sustainable intensification measures will not be sufficient to simultaneously prevent further agricultural expansion and achieve the deep emission cuts needed to meet the COP-21 Paris Agreement on combating climate change. Demand-side reductions will also be necessary. Thus, diet composition has been identified as an important leverage point in reducing the environmental impact of food systems and in freeing up production capacity to feed future population growth.
  • Individual-level data are needed for more nuanced modeling of dietary change policies since they allow for understanding the range of impacts within a population and for linking of individual-level demographics (e.g. age, gender, race-ethnicity, education, nutrition knowledge, environmental attitudes, etc.) to the dietary behaviors of these groups and their environmental impacts.
  • Food production impacts of US self-selected diets averaged 4.7 kg CO2 eq. person per day. Meats (56.6%) and dairy (18.3%) were shown to contribute the most to GHGE and energy demand of US diets; however, beverages also emerged in this study as a notable contributor (5.9%). For the total population, 80.6% of the meats group GHGE comes from beef, 9.5% from poultry, 8.5% from pork, with other meats making up the remaining 1.5%.
  • When ranked by GHGE, diets from the top quintile (the 20% of the population who consumed the highest GHGE diet) accounted for almost 8 times the GHGE as those from the bottom quintile (the 20% of the population who consumed the lowest GHGE diets), showing the importance of utilizing individual dietary behaviors rather than just population means when considering diet shift scenarios.

Variations in methane yield and microbial community profiles in the rumen of dairy cows as they pass through stages of first lactation. Lyons T, Bielak A, Doyle E, Kuhla B. J Dairy Sci. 2018 Mar 14. pii: S0022-0302(18)30253-4.

  • Considerable interest exists both from an environmental and economic perspective in reducing methane emissions from agriculture. In ruminants, CH4 is produced by a complex community of microorganisms that is established in early life but can be influenced by external factors such as feed. Although CH4 emissions were thought to be constant once an animal reached maturity, recent studies have shown that CH4 yield significantly increases from early to late lactation in dairy cows.
  • The aim of this study was to test the hypothesis that increases in CH4 yield over the lactation cycle are related to changes in rumen microbial community structure. Nine cows were monitored throughout their first lactation cycle.
  • A significant difference in bacterial and archaeal community structure during early and late lactation was observed. Furthermore, when ruminal short-chain fatty acid concentrations were measured, the ratio of acetate and butyrate to propionate was significantly higher in late lactation compared with early lactation. Propionate concentrations were higher in cows with low CH4 yield during late lactation.
  • In general, positive correlations were stronger between the most relatively abundant bacterial genera (Prevotella, Succinclasticum, Treponema, Fibrobacter, Ruminococcus, and Bifidobacterium) and acetate and butyrate concentrations in the cows with high CH4, and weaker between these bacterial genera and propionate concentration. This study indicates that increased CH4 yield in late lactation is reflected in significant changes in microbial community structure.

The impact of dairy cows’ bedding material and its microbial content on the quality and safety of milk – A cross sectional study of UK farms. Bradley AJ, Leach KA, Green MJ, Gibbons J, Ohnstad IC, Black DH, Payne B, Prout VE, Breen JE. Int J Food Microbiol. 2018 Mar 23;269:36-45.

  • The introduction of bedding dairy cows on recycled manure solids in the UK led to concern that there could be an increased, unacceptable risk to animal and human health.
  • A cross-sectional study was designed to evaluate the microbial content of different bedding materials, when used by dairy cows, and its impact on the microbial content of milk. Data were collected from farms bedding lactating cows on sand (n=41), sawdust (n=44) and recycled manure solids (n=40).
  • There were substantial differences in bacterial counts (Streptococcus/Enterococcus spp., Staphylococcus spp., Bacillus cereus, thermophilic, thermoduric and psychrotrophic bacteria) both within and between bedding materials. However, there were no significant differences between bedding groups in counts in milk for any of the organisms studied (Listeria monocytogenes, Salmonella spp. and Yersinia enterocolitica), and no significant correlations between bacterial load in used bedding and milk.
  • The detection of pathogens in a small proportion of milk samples, independent of bedding type, indicates that pasteurization of milk prior to human consumption remains an important control measure.

Factors Influencing the Flavour of Bovine Milk and Cheese from Grass Based versus Non-Grass Based Milk Production Systems. Kilcawley KN, Faulkner H, Clarke HJ, O’Sullivan MG, Kerry JP. Foods. 2018 Mar 13;7(3). pii: E37.

  • There has been a surge in interest in relation to differentiating dairy products derived from pasture versus confined systems. The impact of different forage types on the sensory properties of milk and cheese is complex due to the wide range of on farm and production factors that are potentially involved.
  • The main effect of pasture diet on the sensory properties of bovine milk and cheese is increased yellow intensity correlated to β-carotene content, which is a possible biomarker for pasture derived dairy products.
  • Pasture grazing also influences fat and fatty acid content which has been implicated with texture perception changes in milk and cheese and increased omega-3 fatty acids. Changes in polyunsaturated fatty acids in milk and cheese due to pasture diets has been suggested may increase susceptibility to lipid oxidation but does not seem to be an issue to due increased antioxidants and the reducing environment of cheese.
  • Sensory evaluation studies of milk and cheese have, in general, found that untrained assessors who best represent consumers appear less able to discriminate sensory differences than trained assessors and that differences in visual and textural attributes are more likely to be realized than flavour attributes. This suggests that sensory differences due to diet are often subtle.

Semen as a source of Mycoplasma bovis mastitis in dairy herds. Haapala V, Pohjanvirta T, Vähänikkilä N, Halkilahti J, Simonen H, Pelkonen S, Soveri T, Simojoki H, Autio T. Vet Microbiol. 2018 Mar;216:60-66.

  • Mycoplasma bovis infections are responsible for substantial economic losses in the cattle industry, have significant welfare effects and increase antibiotic use. The pathogen is often introduced into naive herds through healthy carrier animals.
  • In this study, the researchers describe how M. bovis was introduced into two closed and adequately biosecure dairy herds through the use of contaminated semen during artificial insemination (AI), leading to mastitis outbreak in both herds.
  • In both farms the primary clinical cases were M. bovis mastitis in cows inseminated with the semen of the same bull four weeks before the onset of the disease. One semen straw derived from the semen tank on the farm and other semen lots of this bull were positive for M. bovis. In contrast, semen samples were negative from other bulls that had been used for insemination in previous or later oestrus to those cows with M. bovis mastitis.
  • This is the first study describing the introduction of M. bovis infection into a naive dairy herd via processed semen. The antibiotics used in semen extenders should be re-evaluated in order to provide farms with M. bovis-free semen or tested M. bovis-free semen should be available.


Selected Articles on Dairy Intake and Human Health

Personal exposure of dairy workers to dust, endotoxin, muramic acid, ergosterol, and ammonia on large-scale dairies in the high plains Western United States. Davidson ME, Schaeffer J, Clark ML, Magzamen S, Brooks EJ, Keefe TJ, Bradford M, Roman-Muniz N, Mehaffy J, Dooley G, Poole JA, Mitloehner FM, Reed S, Schenker MB, Reynolds SJ. J Occup Environ Hyg. 2018 Mar;15(3):182-193.

  • Dairy workers experience a high degree of bioaerosol exposure, composed of an array of biological and chemical constituents, which have been tied to adverse health effects. A better understanding of the variation in the magnitude and composition of exposures by task is needed to inform worker protection strategies.
  • To characterize the levels and types of exposures, 115 dairy workers grouped into 3 task categories on 9 farms in the high plains Western United States underwent personal monitoring for inhalable dust, endotoxin, 3-hydroxy fatty acids (3-OHFA), muramic acid, ergosterol, and ammonia through one work shift.
  • The results showed that 89% percent of dairy workers were exposed to endotoxin at concentrations exceeding the recommended exposure guidelines. The proportion of workers with exposures exceeding recommended guidelines was lower for inhalable dust (12%), and ammonia (1%). Ergosterol exposures were only measurable on 28% of samples, primarily among medical workers and feed handlers. Milking parlor workers were exposed to significantly higher inhalable dust, endotoxin, 3-OHFA, ammonia, and muramic acid concentrations compared to workers performing other tasks.
  • Development of large modern dairies has successfully made progress in reducing worker exposures and lung disease prevalence. However, exposure to endotoxin, dust, and ammonia continues to present a significant risk to worker health on North American dairies, especially for workers in milking parlors. There remains a need for cost-effective, culturally acceptable intervention strategies integrated in Occupational Health and Safety Risk Management and production systems to further optimize worker health and farm productivity.

Dairy Products, Dairy Fatty Acids, and the Prevention of Cardiometabolic Disease: a Review of Recent Evidence. Yu E, Hu FB. Curr Atheroscler Rep. 2018 Mar 21;20(5):24.

  • Dairy composes about 10% of the calories in a typical American diet, about half of that coming from fluid milk, half coming from cheese, and small amounts from yogurt.
  • Most meta-analyses report no or weak inverse association between dairy intake with cardiovascular disease and related intermediate outcomes. There is some suggestion that dairy consumption was inversely associated with stroke incidence and yogurt consumption was associated with lower risk of type 2 diabetes.
  • Odd chain fatty acids (OCFAs) found primarily in dairy (15:0 and 17:0) appear to be inversely associated with cardiometabolic risk, but causation is uncertain.
  • Current evidence suggests null or weak inverse association between consumption of dairy products and risk of cardiovascular disease. More research is needed to examine health effects of different types of dairy products in diverse populations.

Dairy Fats and Cardiovascular Disease: Do We Really Need to be Concerned? Lordan R, Tsoupras A, Mitra B, Zabetakis I. Foods. 2018 Mar 1;7(3). pii: E29.

  • The negative perception of dairy fats stems from the effort to reduce dietary saturated fatty acid (SFA) intake due to their association with increased cholesterol levels and the increased risk of CVD development. Institutions that set dietary guidelines have approached dairy products with negative bias and used poor scientific data in the past. As a result, the consumption of dairy products was considered detrimental to our cardiovascular health.
  • In western societies, dietary trends indicate that generally there is a reduction of full-fat dairy product consumption and increased low-fat dairy consumption. However, recent research and meta-analyses have demonstrated the benefits of full-fat dairy consumption, based on higher bioavailability of high-value nutrients and anti-inflammatory properties.
  • In this review, the relationship between dairy consumption, cardiometabolic risk factors and the incidence of cardiovascular diseases were investigated. In general, evidence suggests that milk has a neutral effect on cardiovascular outcomes but fermented dairy products, such as yogurt, kefir and cheese may have a positive or neutral effect.

Intake of Milk or Fermented Milk Combined With Fruit and Vegetable Consumption in Relation to Hip Fracture Rates: A Cohort Study of Swedish Women. Michaëlsson K, Wolk A, Lemming EW, Melhus H, Byberg L. J Bone Miner Res. 2018 Mar;33(3):449-457.

  • Milk products may differ in pro-oxidant properties and their effects on fracture risk could potentially be modified by the intake of foods with antioxidant activity.
  • Researchers aimed to determine how milk and fermented milk combined with fruit and vegetable consumption are associated with hip fracture. They used data from 38,071 women from the Swedish Mammography Cohort study.
  • Individuals who consumed a low intake of milk (< 1 glass/day) and high intake of fruits and vegetables (>5 servings/day) had a lower risk for hip fracture than those consuming a high intake of milk (≥3 glasses/day) with a low intake of fruits and vegetables (<2 servings/day).
  • However, the combination of fruits and vegetables with fermented milk (yogurt or soured milk) yielded a different pattern, with lowest rates of hip fracture in high consumers of both, (≥2 servings/day of fermented milk and ≥5 servings/day of fruits and vegetables) compared with low consumption of both.
  • In conclusion, the amount and type of dairy products as well as fruit and vegetable intake are differentially associated with hip fracture rates in women.

Whey protein lowers systolic blood pressure and Ca-caseinate reduces serum TAG after a high-fat meal in mildly hypertensive adults. Fekete ÁA, Giromini C, Chatzidiakou Y, Givens DI, Lovegrove JA. Sci Rep. 2018 Mar 22;8(1):5026.

  • Epidemiological studies show an inverse association between dairy consumption and blood pressure (BP) but there are few data on the post-meal effects of milk proteins.
  • This double-blinded, randomized, cross-over, controlled study examined the effects of whey protein and casein protein, compared to maltodextrin, on post-meal BP and other CVD risk markers in 27 adult volunteers with mild and pre-hypertension. Participants ingested a high-fat breakfast and lunch with 28 g whey protein, 28 g Ca-caseinate or 27 g maltodextrin, and were then monitored for 8 hours.
  • Whey protein reduced systolic BP compared with Ca-caseinate (-15.2 ± 6 mmHg) and maltodextrin (-23.4 ± 10.5 mmHg) up to 5 h post-ingestion. There was also an improvement in arterial stiffness after whey protein compared with maltodextrin, but not compared to Ca-caseinate. Despite similar glucose levels after both whey protein and Ca-caseinate, whey protein induced a higher insulin response than Ca-caseinate.
  • Ca-caseinate inducedless suppression of non-esterified fatty acids than whey protein and maltodextrin, and Ca-caseinate induced a smaller postprandial triacylglycerol response than whey protein.
  • Overall, this research shows that different milk proteins consumed with high-fat meals may have the different potential to maintain or improve CVD risk factors.