Texas Tech University

High-Starch Diets for Jersey Cows Alter Nitrogen Partitioning

Norman Martin

June 11, 2020

Jersey Cows

The study, which involved a researcher from Texas Tech University, was published in the Journal of Dairy Science.

Feedstuffs, an online animal agriculture industry source of news, information and analysis based in Bloomington, Minnesota, recently detailed the work of a research team that included Kristin Hales, the Thornton Distinguished Chair in Animal Science in Texas Tech University's Department of Animal & Food Sciences. Here is an excerpt from that report.

Jersey cows are known to produce milk with higher component values than Holsteins, leading to specialized nutrient requirements for the smaller-sized Jersey dairy cow. Now, in the Journal of Dairy Science, a research team has determined the effects of isoenergetic high-starch or high-fat diets on energy and nitrogen partitioning, as well as energy utilization of Jersey cows.

Kristin Hales
Kristin Hales

Kristin Hales, a nationally recognized expert in ruminant nutrition and beef cattle energetics and an associate professor in Texas Tech's College of Agricultural Sciences & Natural Resources, along with Logan Morris, Tami Brown-Brandl and Paul Kononoff at the University of Nebraska-Lincoln and Kevin Harvatine at Pennsylvania State University, found a high-starch diet had greater metabolic energy and net energy lactation (NEL) content, increased nitrogen partitioning toward milk secretion and away from urinary excretion and may have increased energy partitioning toward tissue energy deposited as fat.

In other words, the composition of energy supply, starch vs. fat in this case, may alter milk protein synthesis and should be incorporated into future nutritional models focused on lactating dairy cows. Hales' role in the project included providing input on the dietary treatments, assisting in data interpretation and analysis and assisting in publication of results. She also serves as a member of Morris' doctoral committee and mentors him on cattle energetics.

In developing the study, the research team enrolled 12 multiparous Jersey cows in the study in a crossover design with 28-day periods to compare two treatment diets. Treatments were high starch or high fat. Diets were formulated to have NEL content of 1.55 Mcal/kg of dry matter, according to the National Research Council dairy model.

Nutrient composition was varied primarily by replacing corn grain in the high-starch diet with a rumen-inert fat source and cottonseed hulls in the high-fat diet, the researchers noted. Gross energy content was lower for the high-starch diet, whereas digestible energy, metabolizable energy and NEL content were all greater than for the high-fat diet.

Jersey cow
Jersey cow

Tissue energy deposited as body fat tended to be greater for the high-starch diet, the researchers reported. For nitrogen partitioning, the high-starch diet increased milk nitrogen secretion and decreased urinary nitrogen excretion. In addition, the high-starch diet increased apparent total-tract digestibility of dry matter, organic matter, energy and 18-carbon fatty acids, compared with the high-fat diet. However, the team reported that apparent total-tract digestibility of starch decreased for the high-starch diet from 97 percent to 94.5 percent.

Hales, a Texas Panhandle native, indicated that her research efforts are broadly focused on beef cattle nutrition and management, specifically focusing on rumen microbiome, antimicrobial resistance, beef cattle energetics and improving feed efficiency of beef cattle. For eight years, prior to joining the Texas Tech faculty last year, she served as a research animal scientist with the United States Department of Agriculture Agricultural Research Service's U.S. Meat Animal Research Center in Clay Center, Nebraska. Hales received her bachelor's and master's degrees in animal science from Oklahoma State University and her doctorate in animal science from Texas Tech.