Dr. Maurice Eastridge, Extension Dairy Specialist, The Ohio State University
The Ohio Dairy Research Fund was developed to support research by voluntary dairy producer contributions. Much research is needed to address today's complex issues relative to dairy production, milk quality, and milk products. Since 1982, over $730,000 in producer investments have funded research that has greatly benefited Ohio's dairy industry. From time to time, results of this research will be included in the Buckeye Dairy News. For this issue, the results from two recent projects are provided below.
Occurrence and Control of the Fescue and Ryegrass Toxicosis Endophytes in Ohio Dairy Pastures
Dr. Landon H. Rhodes, Department of Plant Pathology, and Dr. David J. Barker, Department of Horticulture and Crop Science, The Ohio State University
Objective 1: Determine the incidence and distribution of endophytes in ryegrass and tall fescue in Ohio dairy pastures.
A significant finding was that 11% of the ryegrass pastures sampled in 2003 had high (> 40%) incidence of endophyte infection. Intensive grazing on such pastures is likely to result in poor animal performance or animal health problems. Those pastures with moderate levels of endophyte (5 to 40% endophyte infection) are also cause for concern, with 24% of the ryegrass pastures sampled falling into this category. Of the fescue fields tested, 3 (18%) had moderate infection and 8 (47%) had high infection. For those fields re-sampled in 2004, levels of endophyte were similar to those found in 2003. The factor most consistent with high endophyte levels in ryegrass and tall fescue was greater seed of unknown origin. This finding points out the importance of obtaining endophyte-free seed for establishing new pastures. The use of endophyte-free seed to establish new ryegrass (and tall fescue) pastures is probably the best method to ensure that endophytes will not become a problem.
Objective 2: Determine the ability of selected fungicides to eradicate or permanently reduce the incidence of endophytes in established tall fescue and ryegrass.
A field experiment was conducted to determine if certain fungicides could eradicate or reduce the incidence of endophyte in established pasture. Results indicated that none of the 10 fungicide treatments significantly reduced endophyte levels. The unsprayed control plots had 47.5% incidence of endophyte. Considering that plots received four applications of each fungicide and that the maximum label rate of each fungicide was used each time, it appears unlikely that fungicide eradication of endophytes in established pastures will be successful. However, it should be noted that neither the antibody method nor the staining method used to assess endophyte levels in plant tissue are capable of discriminating between living and dead endophyte. Fungicides may have killed some of the endophyte within the grass plants, but these samples would appear identical to samples with live endophyte. Further work is necessary to assess the amount of dead versus living endophyte in tissue samples.
Additional Implications of Findings: Data obtained from these studies has led to improvements in methodology that may be helpful in assessing endophyte levels in the future. In 2003, pre-application sampling in small plots (96 square feet) revealed high spatial variation in endophyte distribution at both Columbus and Jackson. Therefore, in summer 2004, we initiated two field studies (Columbus and Coshocton) investigating the spatial variability of endophyte using 'precision agriculture' methodologies. In each study, 425 tillers were sampled from a 192 square foot area and analyzed for endophyte. We were able to draw spatial maps that showed distinct spatial variability in the distribution of endophyte. Patches ranged from 60 to 100% within the 192 square foot areas. Future work will aim to repeat the spatial mapping studies in an additional year, as well as investigate the implications of this spatial variability (e.g. on livestock grazing patterns). Also, we will continue studies on the mechanisms of endophyte re-infestation of endophyte-free tall fescue pastures, including financial analysis of the costs and returns to livestock producers.
Production of Conjugated Linoleic Acid (CLA) Rich Milk
C. K. Reynolds, S. Loerch, V. Cannon, P. Tirabasso, D. Clevenger, and G. Lowe, Department of Animal Sciences, The Ohio State University
Justification: Milk and dairy products are the major source of dietary CLA for humans, and 'naturally' enriched high CLA butter has been shown to reduce the number and incidence of mammary tumors in rats. There is now considerable interest in the development of 'naturally' enriched CLA milk and milk products for niche markets.
Objectives: Assess the effects of ration forage type (corn silage versus alfalfa pellets or haylage) and novel oil supplements (combination of soybean and marine algal oils) on the enrichment of milk fat conjugated linoleic acid (CLA) content.
Results: Two studies were conducted in 2 calendar years using lactating ewes at the OARDC sheep center. Ewes were used as a model for cows in order to increase the number of observations obtained, and the studies were designed to be complimentary to studies in cows conducted simultaneously at the University of Reading in England using grass- and corn silage-based rations.
Study 1. Feed dry matter intake was lower for corn silage and was reduced by feeding oil. Milk yield was not affected, but milk fat concentration was increased by feeding oil. The concentration of medium chain (12 to 16 carbon) saturated fatty acids was relatively high compared to cows. Their concentration was decreased by feeding oil with alfalfa, but increased by feeding oil with corn silage. The concentration of total (largely cis-9, trans-11) CLA was higher for corn silage than alfalfa and increased by feeding oil, and the response was greater for alfalfa. As for CLA, the total trans-18:1 isomer concentration was higher for corn silage and increased by oil, but the response to oil was greater when corn silage was fed. This difference in total trans-18:1 concentration was due to differences in both trans-10 and trans-11 isomers.
Study 2: As in study 1, feed dry matter intake was reduced by feeding oil and tended to be lower when corn silage was fed. Milk yield was reduced by feeding oil with alfalfa haylage but increased by feeding oil with corn silage. Milk fat concentration was increased by feeding oil with alfalfa haylage, but reduced by feeding oil with corn silage. In contrast to study 1, the concentration of CLA (largely cis-9, trans-11) was higher for alfalfa haylage and increased by oil, and the response to oil was greater with alfalfa haylage. The concentration of trans-10, cis-12 CLA (a known inhibitor of milk fat synthesis in cows) was also increased by oil and was higher when corn silage was fed. As in study 1, the concentrations of trans-11 C18:1 and total trans C18:1 were higher when corn silage was fed, were increased markedly by feeding oil, and the response was greater when oil was fed with corn silage.
Conclusions: The response of milk fatty acid concentrations to supplemental oil was influenced by the type of forage fed, but reasons for the greater increase in CLA concentration when oil was fed with alfalfa in both studies are not certain. Based on diet analysis, the greater basal CLA concentration was associated with greater intakes of linoleic acid in both studies. This suggests that the fatty acid content of the forage fed is an important determinant of basal concentration of milk CLA. In contrast, the greater response of CLA to supplemental oils when alfalfa was fed may be due to greater fiber intake relative to starch, which has been shown to influence CLA levels in milk of dairy cows fed similar oils with diets differing in forage level. This may be due to the effects of diet carbohydrate type on rumen microbes and their ability to saturate fatty acids.
In both studies, the concentration of trans-C18:1 isomers were higher when corn silage was fed, were increased by feeding oil, and the response to oil was greater for corn silage. This also may relate to differences in the amount of starch consumed relative to fiber, and subsequent effects on rumen microbes.
Despite large increases in trans-fatty acid concentration, including trans-10, cis-12 CLA, total milk fat concentration was increased by feeding highly unsaturated oils to ewes. This is opposite to the expected response based on a number of studies in cows. Reasons for this difference are not certain, but if they can be identified, then our understanding of the causes of milk fat depression in dairy cows, and how to manage it, will be improved.