Recipient Organization
TENNESSEE STATE UNIVERSITY
3500 JOHN A. MERRITT BLVD
NASHVILLE,TN 37209
Performing Department
College of Agriculture, Human and Natural Sciences
Non Technical Summary
Beef cattle generate a major proportion of agricultural income in the United States. Beef cattle have been the top agricultural commodity in Tennessee for cash receipts. Tennessee is a major beef producing state, ranking 5th in the US for the number of beef cattle operations. Most Tennessee operations are small-scale with 27 beef cows on average. The average US beef cow weight has increased in the last 30 years. Beef cow production efficiency decreases with increasing cow weight. The push for greater growth leads to reduced reproductive efficiency. Reproductive output is a principal determinant of profitability in cow-calf enterprises. Another result has been increased carcass weights. Beef portion sizes within the USDA guidelines are limited with the total daily recommendations for meat and protein alternatives to be 142 to 198 g. Increasing carcass sizes pose issues with fabrication to produce acceptable whole muscle retail cuts that meet USDA dietary recommendations. Beef cuts must 'fit the plate' within the current USDA My Plate guidelines. A smaller breed of beef cattle could contribute to animal production by addressing the issues addressed above. Dexter cattle is a heritage breed from the British Isles that is about half the weight of commercial beef cattle. The small size would seem to make Dexter cattle suited for the small acreage, part-time farms that are typical in Tennessee. Direct sales, local marketing, and grass fed-to-finish are all emerging areas of beef production that would favor a smaller breeds with smaller carcasses.As a British Bos taurus breed, the Dexter are prone to heat stress in the southern US just like the larger commercial breeds such as Angus and Hereford. Elevated ambient temperatures and humidity along with tall fescue pastures pose risks of hyperthermia in Bos taurus cattle. Average summer high temperature in Nashville, TN is 32.2?C. The region of origin for Dexter cattle (Kerry, Ireland) has an average summer high temperature of 18.9?C. Managing for spring-born calves to match high nutrient demand with greatest forage nutrient value requires summer breeding. Breeding cattle in the summer poses the challenge of achieving satisfactory pregnancy rates (> 80%) because heat stress is a noted suppressor of fertility. Timely shedding of winter coat in cattle can help to lessen the impact of summer conditions on thermal status in cattle, whereas delayed shedding can exacerbate the risk of hyperthermia and reduced fertility. Studies are scarce that have addressed the possible relationship between warm season levels of retained winter hair coat and summer cow fertility. This is an important relationship to study when understanding the adverse effect of heat stress on cow fertility.The aim of the project is to determine if hair shedding levels affect small-breed cow-calf performance. Dexter cows will be managed in a low-input grazing system with planned pure breeding and crossbreeding to characterize cow-calf production values from breeding to weaning. Cows will be scored periodically during the spring (calving season) and summer (breeding season) for the amount of winter hair loss. Cows will be classified as high or low hair shedders and those two groups will be compared for calf growth rates and cow fertility rates. Tall fescue is a primary southern pasture forage so early winter hair shedding would be beneficial in grass finishing systems where heat intolerance because of fescue toxicosis would be a problem. Early shedding of winter hair preceding summer breeding could alleviate some of the heat stress that lowers cow fertility and milk yield. Findings of this project will be shared with both the academic community at professional meetings and current and potential ruminant livestock managers at industry events. If early shedding cows can be identified and demonstrated to have improved cow-calf performance, this trait may be added to a set of phenotypic assessments small-scale managers of traditional and alternative cattle breeds could use in cow herd evaluations.
Animal Health Component
50%
Research Effort Categories
Basic
50%
Applied
50%
Developmental
(N/A)
Goals / Objectives
The general aim of this project is determining how relative spring hair shedding levelsin cows are associated with cow-calf performance in a spring calving Dexter herd. Work will be conducted to 1) determine relative hair sheddingscores and repeatability in Dexter cows,2) evaluate the effect of cow hair coat scores on reproductive rates, and 3) assess the influence of dam hair coat scores on calf preweaning growth. Project activities involve assessing preweaning calf growth and cow weight and reproductive performance in Dexter cattle. The expectation is that information will generated indicating the extent to which hair shedding is a trait to be recorded in spring-calving beef cattle as an influencer of cow-calf performance.
Project Methods
Dextercows (Bos taurus;n = 80; 3+ years of age) in the TSU herd will be managed on mixed-forage pasture. at 2 cows/ha.Winter management includes free-choice mixed-grass hay. Water and minerals for ad libitum consumption are provided year-round. Over fouryears, cows will be bred by natural service in July to Dexter and Mashona bulls to produce spring calves. Mashona is a small, heat tolerant, rare Sanga breed. All cows will calve to each service sire breed at least once over the three years. Cows are culled after a second failure to wean a calf. At two-week intervals from April until August of 4successive years, cows will be scored for hair coat shedding based on the percentage of body exhibiting winter hair loss (0% = thick winter coat, 100% = slick summer coat). Scores will be recorded in 5% intervals. Cow body condition scores will also be recorded along with hair coat scores. Cows will be weighed at breeding and calf weaning. Calves will be weighed at birth, at 3 mo of age, and at weaning when the median age of the contemporary is 180 d of age.Cow-calf trait datawill be tested using mixedmodel statistical procedures. Cows will be classified each year as high (> 50%) shedders or low (0 to 50%) shedders atdifferent times before and during thesummer breeding season.Cow age, cow physiological status (pregnant/lactating or dry), calf breed (straightbred Dexter or Mashona crossbred) and calf sex (bull or heifer) will also be included in statistical models along with hair coat class. Probability levels (P-value) less than 0.05 for the F statistic will indicate that significant differences exist within a main effect or that an interaction between main effects exists.Cows will be ranked for hair shedding within the herd each year and rank correlations performed to determine if they are consistent across years. Correlations of dates when individual cows achieve 50% shed score across years will also be run. The correlations will provide indicators of repeatability. Preliminary findings will be presented at American Society of Animal Science meetings. Manuscripts presenting final results will be submitted to refereed publications such as the Journal of Animal Science and Livestock Science.