Location: Dairy Forage Research2021 Annual Report
Objective 1: Develop and evaluate strategies that optimize growth and development; maximize feed nutrient use efficiency; increase milk production potential; and increase the lifetime productivity, health, and well-being of dairy heifers. Objective 2: Develop and evaluate dietary feed formulation strategies that increase the utilization of conventional feeds/forages and alternative feeds/forages that reduce competition with human food consumption, enhance nutrient use efficiency, and increase milk production. • Sub-objective 2.A. Evaluate effects of forage type, amount, and quality on animal performance, nutrient digestibility, and feed conversion efficiency. • Sub-objective 2.B. Evaluate effects of alternative/byproduct feeds that replace or reduce grain in the diet on animal performance, nutrient digestibility, and feed conversion efficiency. Objective 3: Develop and evaluate dairy diets that enhance milk production and quality, reduce manure nutrient excretions, and reduce environmental impacts of dairy farms.
Objective 1. Dry matter intake, body weight, and growth measurements at prepubertal (6 months of age) and postpubertal (12 months of age) stages of dairy heifers growth will be determined as part of a study that will help us determine whether efficiency of growth changes during the lifetime of the dairy animal. Growth measurements for prepubertal and postpubertal dairy heifers will be combined with calfhood and mature cow measurements to evaluate if growth efficiency is correlated through the lifespan of a dairy animal. Objective 2. A series of lactating dairy cow studies will be conducted to evaluate the effect of forage type, forage amount, and forage quality on animal performance, nutrient digestibility, and feed conversion efficiency. In addition, alternative forages and byproduct feedstuffs will be evaluated as replacements for traditional feedstuffs used in dairy cow diets. We will collect production measurements, gaseous emissions, digesta, and feces to determine the effects of altering fiber digestibility on ruminal fermentation, lactation performance, and environmental output. Objective 3. Several studies will be conducted to evaluate dairy diets that enhance milk production, reduce nutrient excretion, and reduce the environmental impacts of dairy production systems. Cows will be fed diets with differing ratios of alfalfa silage and corn silage at high and low forage inclusions and at different dietary crude protein concentrations to evaluate the effect of diet formulation on production measures, gas emissions, and nutrient excretion. Manure collected from these experiments will further studied in laboratory emission chambers to determine effect of manure chemistry on gaseous emission during storage. Stored manure will then be applied to a field to determine plant nutrient uptake during a growing season. Gas measurements will be taken to evaluate the impact of manure application on carbon dioxide, ammonia, and nitrous oxide emissions.
A study was conducted to evaluate the inclusion of different forage types (corn silage vs alfalfa silage) on lactation performance, milk composition, nutrient utilization, and feed conversion efficiency of lactating cows from two different breeds of cattle (Holstein and Jersey) (Objective 2.A). Previous research found that the nitrogen use efficiency of a corn silage diet is higher than an alfalfa silage diet and that milk protein content was higher with the corn silage forage, even though the corn silage forage has a lower protein content than the alfalfa silage, however alfalfa more efficiently used nitrogen in the field compared to corn silage. Evaluating the production of forages, how they are efficiently utilized as feed, and the resulting quality of milk for human consumption is needed to produce healthier milk more efficiently and more sustainably. Laboratory analysis is currently underway. Additional analysis will be completed before a manuscript can be written. A study was conducted to evaluate diets formulated with extreme mechanical processed alfalfa silage compared to traditionally harvested alfalfa silage on lactation performance, nutrient digestibility, and rumen fermentation of lactating dairy cows (Objective 2.A). Laboratory analysis has been completed except for the in vivo nutrient digestibility. A manuscript related to production responses of cows fed extreme mechanical processed alfalfa vs conventional alfalfa silage is currently in preparation and will be submitted once digestibility data is completed. A study was conducted to evaluate diets formulated with reduced-lignin alfalfa silage compared to conventional alfalfa silage at two different harvest intervals on lactation performance, nutrient digestibility, and rumen fermentation of lactating dairy cows (Objective 2.A). Improvements in fiber digestibility will allow producers to formulate greater amounts of forages in diets without compromising milk yield resulting in similar or more milk production at lower input costs. Laboratory analysis has not yet started. Sample analysis will begin soon. Once sample and statistical analysis has been completed, a journal manuscript will be written.
1. Replacement of protein and non-fiber feedstuffs with high quality alfalfa silage in the diets of lactating dairy cows. Inclusion of reduced-lignin varieties of alfalfa are proposed as a way to increase forage concentrations in lactating dairy cow diets without decreasing lactation performance. Higher forage diets often decrease intake resulting in lower milk production; however, reduced-lignin varieties of alfalfa may potentially result in higher overall nutrient digestibility and greater rates of passage in the rumen, resulting in similar milk production to a control diet at lower forage concentrations. Recent research by ARS researchers in Madison, Wisconsin, demonstrate that substitution of protein and non-forage fiber feedstuffs up to 18% of the diet with high-quality alfalfa silage decrease dry matter intake without affecting milk production. In addition, milk fat percentage and milk fat yield increased with increasing concentration of forage in the diet. Because milk production was unaffected by diet, feed conversion efficiency increased linearly from 1.63 to 1.83 when high quality alfalfa increased in the diet. These findings demonstrate to dairy producers that high quality, highly digestible alfalfa silage can be used as replacement for purchased protein and non-fiber feedstuffs without negatively affecting milk production, while improving the dairy cow’s ability to convert feed to milk.
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