Impact of management on carcass outcomes
- Project Leads: Kim Ominski, Professor and Argenis Rodas- González, Assistant Professor, University of Manitoba
- MBFI Location(s):Johnson Farm
- Collaborating Partners: Emma McGeough and Karin Wittenberg, University of Manitoba; Kim Vonnahme, Kendall Swanson, Larry Reynolds, Marc Bauer, Allison Ward, Gerald Stokka and Carl Dahlen, North Dakota State University
- Start Date: Sept 2016
- Status: In progress
Impact of cow-calf feeding on carcass outcomes in beef cattle
The common practice of keeping cows in drylots during the winter period has been replaced by practices such as use of stock-piled forage, swath and bale grazing. Our 2012 survey of Canadian cattle producers demonstrated predominant use of extensive non-confined overwintering practices, with only 19% of farms still using confined feeding areas compared to almost 50% of producers using this method for overwintering cattle when surveyed in 20051.
Cattle wintered both in extensive, as well as drylot environments, are exposed to long periods of cold and fluctuating weather patterns including precipitation. In both environments, nutrient deficiencies may occur if forage quality does not meet the increased nutrient demand associated with decreased temperature and increased fetal growth over the winter period. A 2013 survey of forage in Saskatchewan indicated that only 38% of all the forages sampled met the requirements for cows that were at -25°C and were six months pregnant. Only 29% of the alfalfa and alfalfa-grass hays provided adequate energy. As cows enter the final month of pregnancy and nutrient requirements increase, only 5% of all the sampled forages would have provided adequate energy2. Furthermore, it appears that a portion of the alfalfa grass hay and grass hay samples collected would not have met the protein requirements of pregnant cows. In the last several years, extreme weather events (flooding) in the prairie region in the spring, followed by lack of rainfall later in the growing season have led to decreased forage availability, as well as decreased forage quality as a consequence of increased forage maturity.
Compromised maternal nutrition during gestation can impact progeny performance of heifers (reproductive performance) and steers (body weight gain, final body weight, hot carcass weight, back fat and marbling) as described by Funston et al3. More specifically, the fetal stage is important for muscle development, as muscle fibers do not increase in number after the animal is born4. The impact of nutrient restriction during gestation (i.e. two to seven months) is of significance for muscle development as muscle is of lower priority in nutrient partitioning compared to other organs5, resulting in reduced muscle mass. In addition to muscle fiber number, intramuscular adipocytes, which are associated with intramuscular fat accumulation or marbling, are affected during fetal development6. Most notably, Du et al6 have suggested that the opportunities to alter marbling through nutrition are greater for the fetal stage than for all growth phases thereafter.
Several studies have been conducted in the United States (Wyoming/Nebraska) that have examined the impact of maternal protein restriction or supplementation on progeny performance for cows grazing dormant winter range7, 8, 9, 10, 11. Benefits of protein supplementation have included increased birth weight, average daily gain to weaning, increased hot carcass weight, marbling scores and a greater proportion of steers grading USDA Choice or greater. In addition, several researchers have reported an increased number of live calves9, as well as a decreased proportion of the steers from supplemented cows being treated for respiratory disease7, 12. For energy-deficient diets, benefits of supplementation during gestation have been reported in swine, leading to an increase in muscle fiber numbers, improved feed efficiency and a greater percentage of adipose tissue13.
These studies are particularly relevant to the western Canadian production environment, where cows may experience increased nutrient demands associated with exposure to extreme temperatures and further exacerbated by feeding of low-quality forages which may be deficient in both energy and protein, as described above. For spring-calving cows, it is likely that this nutrient restriction will occur in late fall/winter (approximately 100 days of gestation) as nutrients demands are increased due to decreased temperatures and increased fetal growth. Our understanding of the long-term impacts of nutrient restrictions at this stage in gestation is lacking. Muscle growth and development are impacted by blood metabolites (including growth hormone, thyroid hormones, IGF-1, insulin concentrations) as described in Beerman et al14 and Eisemann et al 15.We propose to examine uterine blood flow and circulating metabolic compounds in nutrient restricted and non-restricted cows and their offspring from gestation through to slaughter to determine nutrient/metabolite availability and subsequent impacts on growth and development, as well as carcass outcomes. Additionally, as the quantity of blood flow determines, to a large extent, nutrient delivery to the developing muscle and thus its final composition14,15, we also will determine muscle composition (fiber numbers and sizes as well as types, and adipocyte numbers and types) and vascular development and function in the calves at two time-points postnatally and at slaughter.
Impact of vaccination strategies on carcass outcomes in beef cattle
As calves in the study will be monitored from birth to finish, we also have the unique opportunity to concurrently examine the impact of vaccination strategy at weaning and in the feedlot on carcass outcomes. Recent work conducted in Manitoba16, 17 has demonstrated that use of needle-free (NF) vaccination technology provides a comparable immune response in calves. However, visual inspection of the site of vaccination demonstrated that calves vaccinated using the NF technique has an increased occurrence of injection site reactions, particularly with Clostridial vaccines. Although a reaction is necessary to stimulate an immune response, carcass evaluation is necessary to ensure that the reactions/lesions do not persist until slaughter. Both Manitoba Beef Producers and Manitoba Agriculture are interested in the on-farm use of this technology.