Publications by authors named "J M Heguy"

10 Publications

Feeding high amounts of almond hulls to lactating cows.

J Dairy Sci 2021 Aug 10;104(8):8846-8856. Epub 2021 May 10.

Department of Animal Science, University of California, Davis 95616. Electronic address:

California is the leading state for the production of almonds, with more than 400,000 bearing hectares of orchards that produced approximately 1 billion kilograms of shelled nuts in 2017. Almond hulls (AH) are a regional by-product feedstuff fed predominantly to dairy cattle in California. A 2012 study surveyed 40 dairy farms in California and found that 39 out of 104 total mixed rations contained AH, with a mean daily feeding rate of 1.45 kg/cow. In 2017, approximately 2 billion kilograms of AH was produced. At a feeding rate of 1.45 kg/cow daily, even if all 1.7 million lactating cows in California are consuming AH, there will be a surplus of AH on the market as the approximately 130,000 nonbearing hectares come into nut production. Therefore, the potential of feeding varying amounts of AH to lactating dairy cows was investigated using 12 Holstein cows with 4 primiparous and 8 multiparous cows. The dietary treatments were 4 total mixed rations containing 0, 7, 13, or 20% AH. The AH used contained 12.8% crude fiber (as-is basis), which was below the 15% legal limit set by state feed regulations. Diets were formulated so that as the inclusion rate of AH increased, the amount of steam-flaked corn and soyhull pellets decreased and soybean meal inclusion increased. Experimental design was a replicated 4 × 4 Latin square. Diet had a cubic effect on actual milk yield, energy-corrected milk yield, and dry matter intake, with the 7% AH diet having the highest values and the 13% AH diet having the lowest. The percent and yield of total solids and the yields of lactose and fat did not differ with diet, but percent and yield of protein declined linearly with increased AH inclusion, and fat percent increased linearly. Apparent total-tract digestibilities of dry matter and organic matter were higher with the inclusion of AH in the diet. Total percentage of the day spent ruminating increased linearly with higher amounts of AH. Overall, this work demonstrated that AH can be fed at varying amounts, up to 20% of the diet, to lactating dairy cows to support high levels of milk production and that increasing amounts of AH (up to 20%) in the diet could lead to improved digestibility and milk fat percentage but decreased milk protein production.
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http://dx.doi.org/10.3168/jds.2020-19109DOI Listing
August 2021

Needs assessment for cooperative extension dairy programs in California.

J Dairy Sci 2019 Aug 6;102(8):7597-7607. Epub 2019 Jun 6.

University of California Agriculture and Natural Resources, Cooperative Extension, Orland 95963.

The present study aimed to identify dairy producer needs and how best to direct and deliver cooperative extension (CE) programming. In March 2017, we mailed a needs assessment survey to grade A dairy producers in California (n = 1,080). The response rate was 15.4% (n = 166) and herd size averaged 1,405 milking cows (range 83-5,500). The geographic distribution of survey responses was representative of the distribution of dairies throughout the state. Producers were asked to indicate the level of concern for a predetermined list of 11 issues. Rank of concern had 3 numeric levels: (1) very concerned, (2) somewhat concerned, or (3) not concerned. Mean and percentage of responses in each rank for each issue topic were calculated. The top 5 concerns/obstacles indicated were (1) milk price, (2) labor availability/quality, (3) environmental issues/regulations, (4) labor costs, and (5) water quality/availability. Surveyed respondents were also asked to determine the level of priority of a predetermined list of 13 CE research and educational opportunities. Producers ranked topics as low, medium, or high priority. The 5 highest priority research topics were (1) herd health, (2) environmental issues, (3) reproduction, (4) milk quality, and (5) water quality. The 5 highest priority educational topics were (1) herd health, (2) milk quality, (3) reproduction, (4) environmental issues, and (5) calf and heifer management. Producers were then asked to identify the target audience for CE information delivery and preferred information delivery method. Most respondents indicated that the target audience should be dairy owners (93%) or managers (66%). Fewer producers indicated a target audience of dairy employees (27%) or allied industry (23%). Preferable information delivery methods were newsletter or magazine articles (81%), half-day/short meetings (47%), and on-farm training/meetings (39%). Webinars and 2- or 3-d destination meetings were the least preferable methods (27 and 9%, respectively). Survey results will serve to develop future dairy cooperative extension programs in California.
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http://dx.doi.org/10.3168/jds.2018-15959DOI Listing
August 2019

Fecal Microbial Communities in a Large Representative Cohort of California Dairy Cows.

Front Microbiol 2019 16;10:1093. Epub 2019 May 16.

Department of Animal Science, University of California, Davis, Davis, CA, United States.

Improved sequencing and analytical techniques allow for better resolution of microbial communities; however, the agriculture field lacks an updated analysis surveying the fecal microbial populations of dairy cattle in California. This study is a large-scale survey to determine the composition of the bacterial community present in the feces of lactating dairy cattle on commercial dairy operations. For the study, 10 dairy farms across northern and central California representing a variety of feeding and management systems were enrolled. The farms represented three typical housing types including five freestall, two drylot and three pasture-based management systems. Fresh feces were collected from 15 randomly selected cows on each farm and analyzed using 16S rRNA gene amplicon sequencing. This study found that housing type, individual farm, and dietary components significantly affected the alpha diversity of the fecal microbiota. While only one Operational Taxonomic Unit (OTU) was common among all the sampled individuals, 15 bacterial families and 27 genera were shared among 95% of samples. The ratio of the families to was significantly different between housing types and farms with pasture fed animals having a higher relative abundance of . A majority of samples were positive for at least one OTU assigned to and 31% of samples contained OTUs assigned to . However, the relative abundance of both taxa was <0.1%. The microbial composition displays individual farm specific signatures, but housing type plays a role. These data provide insights into the composition of the core fecal microbiota of commercial dairy cows in California and will further generate hypotheses for strategies to manipulate the microbiome of cattle.
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http://dx.doi.org/10.3389/fmicb.2019.01093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6532609PMC
May 2019

Optimizing accuracy of sampling protocols to measure nutrient content of solid manure.

Waste Manag 2019 Feb 26;85:121-130. Epub 2018 Dec 26.

Department of Animal Science, One Shields Avenue, University of California, Davis, CA 95616, USA. Electronic address:

Precise applications of manure to cropland can help optimize productivity and minimize environmental nutrient losses. Applying manure precisely is a challenge because the nutrient content of manures is inherently variable and the accuracy of sampling protocols are unknown. This study aimed to quantify the accuracy of sampling protocols for static solid manure piles considering both the number and depth of grab samples entering a composite sample. Over 35 grab samples were collected from each of ten static piles of dairy manure in California's Central Valley. Grab samples were individually analyzed for dry matter (DM), ash, total nitrogen, potassium, and phosphorous concentrations. Resampling simulations quantified the precision and bias of sampling protocols varying in both grab sample number and depth. Results showed that number of grab samples required for measurements to meet an accuracy standard of ±10% of the true value varied significantly by pile makeup. Over 25 grab samples were often required for multi-source manure piles, where an average of six grab samples were required from single source piles. The DM concentration of manure piles decreased at depths greater than 0.4 m, and sampling simulations showed that measurements were biased unless 70-80% of grab samples were collected from the pile interior. Both the number and location of grab samples necessary to create a representative composite require resource investments by farmers, and should be considered to manage nutrient applications cropland.
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http://dx.doi.org/10.1016/j.wasman.2018.12.021DOI Listing
February 2019

Optimizing accuracy of protocols for measuring dry matter and nutrient yield of forage crops.

Sci Total Environ 2018 May 14;624:180-188. Epub 2017 Dec 14.

Department of Animal Science, One Shields Avenue, University of California, Davis, CA 95616, USA. Electronic address:

Farmers around the world must precisely manage nutrients applied to and removed from crop fields to maintain production and without causing nutrient pollution. This study is the first to quantify the baseline accuracy of current industry measurement protocols and achievable accuracy from intensifying protocols for measuring dry matter (DM), nitrogen (N), potassium (K), and phosphorus (P) yields from forage crops harvested for silage. The 'true' DM and nutrient yields of three fields each of corn, sorghum, and small grain were intensively measured by weighing and sampling every truckload of harvested forage. Simulations quantified the accuracy of practical sampling protocols by repeatedly subsampling the complete dataset for each field to measure average truckload weight and average DM and nutrient concentrations. Then uncertainty was propagated to DM, N, P, and K yield calculations using standard error equations. Yields measured using current industry protocols diverged from the true yields of some fields by more than ±40%, emphasizing the need for improved protocols. This study shows that improving average DM and nutrient concentration measurements is unlikely to improve accuracy of yield measurements if average load weight is not precisely measured. Accuracy did not come within 27% of true yields without weighing all truckloads on some fields even when DM and nutrient concentration measurements were perfectly accurate. Once all truckloads were weighed, the timing of forage sample collection to measure average DM concentration had the greatest impact on accuracy; precision improved by an average of 6.2% when >3 samples were evenly spaced throughout the harvest compared to the same number of consecutive samples. All crop fields are affected by within field variation in growing conditions that results in heterogeneity in DM and nutrient yield. Globally, this study provides foundational methodology to quantitatively evaluate and improve yield measurement protocols that ultimately support sustainable crop production.
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http://dx.doi.org/10.1016/j.scitotenv.2017.11.203DOI Listing
May 2018
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