PSVII-6 Effects of heat stress on proteolysis in dairy cattle skeletal muscle

Abstract Heat stress (HS) occurs when internal body temperatures are elevated above a thermoneutral zone in response to extreme environmental temperatures. In the U.S. dairy industry, HS results in economic loss due to decreased feed intake, milk quality, and milk yield. Previous work has demonstrated increased plasma urea nitrogen in heat stressed dairy cattle which is thought to originate from increased skeletal muscle proteolysis, however this has not been empirically established. The objective of this investigation was to determine the extent to which HS promotes proteolysis in skeletal muscle of dairy cattle. We hypothesized HS would increase activation of the calpain and proteasome systems in skeletal muscle. To test this hypothesis, following a 3-d acclimation period in individual box stalls, all lactating dairy cows were held under thermoneutral (TN) conditions for 4-d for collection of baseline measures and then exposed to TN or HS conditions for 7-d followed by a biopsy of semitendinosus (n=8/group). To induce HS, cattle were fitted with electric heating blankets, which they wore for the duration of the heating period. This approach increased rectal temperature 1.1°C (P< 0.05), respiratory rate by 33 bpm (P< 0.05), plasma urea nitrogen by 19% (P=0.08) and milk urea nitrogen by 26% (P< 0.05), and decreased dry matter intake by 32% (P< 0.05) and milk production by 26% (P< 0.05) confirming HS. Contrary to our expectations, we discovered that calpain I and II abundance and activation, and calpain activity were similar between groups. Likewise, protein expression of E3 ligases, MafBx and Murf1, were similar between groups as was total ubiquitinated proteins and proteasome activity. Collectively, and counter to our hypothesis, these results suggest skeletal muscle proteolysis is not increased following 7-d of HS. These data question the presumed dogma that increased blood urea nitrogen is due to elevated proteolysis in skeletal muscle.

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Corn supplementation on milk urea nitrogen content of dairy cows grazing on temperate annual pasture

Ciência Rural ◽

10.1590/0103-8478cr20190077 ◽

2020 ◽

Vol 50 (2) ◽

Cited By ~ 1

Author(s):

Aline Cristina Dall-Orsoletta ◽

João Gabriel Rossini Almeida ◽

Márcia Maria Oziemblowski ◽

Henrique Mendonça Nunes Ribeiro-Filho

Keyword(s):

Dairy Cows ◽

Protein Production ◽

Milk Protein ◽

Live Weight ◽

Corn Silage ◽

Utilization Efficiency ◽

Urea Nitrogen ◽

Plasma Urea ◽

Lactation Stage ◽

Milk Urea

ABSTRACT: The excretion of urinary nitrogen (N), one of the most important environmental contaminants from livestock systems, is highly correlated with milk urea N content. The objective of this research was to evaluate the use of different types of corn supplementation on milk urea N in grazing dairy cows. Twelve Holstein × Jersey lactating dairy cows were divided into six uniform groups according to milk production, lactation stage and live weight. Treatments were compared according to a 3 × 3 replicated Latin square experimental design, with three periods of seventeen days (twelve days to adaptation and five to measurements). The experimental treatments were exclusively grazing (G); grazing + supplementation with 4.2 kg DM of corn silage (CS) and grazing + supplementation with 3.2 kg DM of ground corn (GC). The pasture used was annual ryegrass (Lolium multiflorum L.) and white oats (Avena sativa L.). The milk protein production increased 65 g/day in the GC treatment group compared to the G and CS groups. The supplemented dairy cows showed lower milk urea N (-2.8 mg/dL) than unsupplemented cows, but the N utilization efficiency (g N output in milk/ g N intake) did not change between treatments (average = 0.26). Additionally, there was a relationship between milk and plasma urea nitrogen concentrations (R2 = 0.64). In conclusion, for dairy cows grazing annual temperate pastures, corn ground supplementation increased milk protein production and reduced the excretion of milk urea N, whereas corn silage reduced the excretion of milk urea N without affecting milk protein production.

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Relationship among concentrations of milk urea nitrogen and plasma urea nitrogen and feeding time

Kansas Agricultural Experiment Station Research Reports ◽

10.4148/2378-5977.3197 ◽

2000 ◽

pp. 48-53

Author(s):

E.E. Ferdinand ◽

M. J. Meyer ◽

A.F. Park ◽

M. J. VanBaale

Keyword(s):

Feeding Time ◽

Urea Nitrogen ◽

Plasma Urea ◽

Milk Urea ◽

Milk Urea Nitrogen

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Prediction of ammonia emission from dairy cattle manure based on milk urea nitrogen: Relation of milk urea nitrogen to ammonia emissions

Journal of Dairy Science ◽

10.3168/jds.2009-2415 ◽

2010 ◽

Vol 93 (6) ◽

pp. 2377-2386 ◽

Cited By ~ 28

Author(s):

S.A. Burgos ◽

N.M. Embertson ◽

Y. Zhao ◽

F.M. Mitloehner ◽

E.J. DePeters ◽

...

Keyword(s):

Dairy Cattle ◽

Cattle Manure ◽

Ammonia Emission ◽

Ammonia Emissions ◽

Urea Nitrogen ◽

Milk Urea ◽

Milk Urea Nitrogen

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Breeding strategies to reduce environmental footprint in dairy cattle

Advances in Animal Biosciences ◽

10.1017/s2040470013000289 ◽

2013 ◽

Vol 4 (s1) ◽

pp. 28-36 ◽

Cited By ~ 3

Author(s):

Donagh P. Berry

Keyword(s):

Dairy Cattle ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Milk Production ◽

Nitrogen Excretion ◽

Environmental Footprint ◽

Gas Emissions ◽

Urea Nitrogen ◽

Milk Urea ◽

Milk Urea Nitrogen

Animal breeding should be considered as a permanent and cumulative approach to reducing the environmental footprint of dairy cattle production systems within an overall national and global mitigation strategy. Current international dairy cattle breeding goals do not explicitly include environmental traits, but observed improvements in milk production and both fertility and longevity contribute substantially to improving the environmental footprint relative to output. Ideally, however, environmental related traits, most notably greenhouse gas emissions and nitrogen excretion, should be explicitly included in national breeding goals with their own economic weight. Access to routine phenotypic observations for the environmental traits or other information including genomic information or information on heritable correlated traits is required for inclusion in the selection index. There is, however, a considerable paucity of information on the genetic parameters for, in particular, greenhouse gas emissions in dairy cattle; these parameters include genetic variance estimates, as well as genetic and phenotypic (co)variances with other performance traits. Large studies with well phenotyped animals across a range of environments are needed to estimate such parameters and also investigate the extent, if any, of genotype-by-environment interactions across contrasting environments. Considerable genetic variation in milk urea nitrogen, as a proxy for nitrogen excretion in the urine, exist and suggest that breeding programmes to improve nitrogen use efficiency will be fruitful. However, because of the antagonistic genetic correlations between milk urea nitrogen and milk production, genetic gain in milk yield is expected to be compromised within a breeding goal that includes milk urea nitrogen.

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Genetic variation in milk urea nitrogen concentration of dairy cattle and its implications for reducing urinary nitrogen excretion

animal ◽

10.1017/s1751731119000235 ◽

2019 ◽

Vol 13 (10) ◽

pp. 2164-2171 ◽

Cited By ~ 3

Author(s):

P.R. Beatson ◽

S. Meier ◽

N.G. Cullen ◽

H. Eding

Keyword(s):

Genetic Variation ◽

Dairy Cattle ◽

Nitrogen Concentration ◽

Nitrogen Excretion ◽

Urea Nitrogen ◽

Milk Urea ◽

Urinary Nitrogen Excretion ◽

Urinary Nitrogen ◽

Milk Urea Nitrogen

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Using Milk Urea Nitrogen to Evaluate Diet Formulation and Environmental Impact on Dairy Farms

The Scientific World JOURNAL ◽

10.1100/tsw.2001.265 ◽

2001 ◽

Vol 1 ◽

pp. 852-859 ◽

Cited By ~ 4

Author(s):

J.S. Jonker ◽

R.A. Kohn

Keyword(s):

Environmental Impact ◽

Dairy Cattle ◽

Dairy Cows ◽

Chesapeake Bay ◽

Dairy Farms ◽

Utilization Efficiency ◽

Urea Nitrogen ◽

Lactating Dairy Cows ◽

Milk Urea ◽

Lactating Dairy Cattle

Reducing nitrogen (N) excretion by dairy cattle is the most effective means to reduce N losses (runoff, volatilization, and leaching) from dairy farms. The objectives of this review are to examine the use of milk urea nitrogen (MUN) to measure N excretion and utilization efficiency in lactating dairy cows and to examine impacts of overfeeding N to dairy cows in the Chesapeake Bay drainage basin. A mathematical model was developed and evaluated with an independent literature data set to integrate MUN and milk composition to predict urinary and fecal excretion, intake, and utilization efficiency for N in lactating dairy cows. This model was subsequently used to develop target MUN concentrations for lactating dairy cattle fed according to National Research Council (NRC) recommendations. Target values calculated in this manner were 8 to 14 mg/dl for a typical lactation and were most sensitive to change in milk production and crude protein intake. Routine use of MUN to monitor dairy cattle diets was introduced to dairy farms (n = 1156) in the Chesapeake Bay watershed. Participating farmers (n = 454) were provided with the results of their MUN analyses and interpretive information monthly for a period of 6 months. The average MUN across all farms in the study increased in the spring, but the increase was 0.52 mg/dl lower for farmers receiving MUN results compared to those who did not participate in the program. This change indicated that participating farmers reduced N feeding compared to nonparticipants. Average efficiency of feed N utilization (N in milk / N in feed x 100) was 24.5% (SD = 4.5). On average, farmers fed 6.6% more N than recommended by the NRC, resulting in a 16% increase in urinary N and a 2.7% increase in fecal N compared to feeding to requirement. N loading to the Chesapeake Bay from overfeeding protein to lactating dairy cattle was estimated to be 7.6 million kg/year. MUN is a useful tool to measure diet adequacy and environmental impact from dairy farms.

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