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<p>Methionine (Met) is an essential amino acid (EAA) and is often considered one of the first limiting amino acids (AA) for milk production in dairy cattle. In diets of lactating dairy cattle, in the United States (U.S.), Met is considered limiting due to its low abundance in commonly fed ingredients like soybean and corn and its high degradability in the rumen. To circumvent this problem, rumen-protected Met (RPM) products were produced and are currently supplemented to dairy cattle. Supplemental RPM products protect Met from degradation in the rumen and deliver Met to the intestine to be absorbed into circulation, increasing metabolizable Met supply. Due to Met important roles in protein synthesis and as a methyl donor, dairy producers have supplemented RPM for decades. The primary benefit for supplementing RPM is improved milk protein concentration, which is important as a majority of dairy farms in the U.S. are paid based on milk components. </p> <p>Research is focused on finding a more economically viable RPM product that provides similar or better bioavailability of Met compared to commercially available products. This has led to the development of a novel rumen-protected Met product (EMT 3.4) in which Met is added to the soluble portion of distillers and incorporated with distillers grains. The result is distillers grains with solubles (DDGS) with elevated Met concentration. Incorporating Met into the solubles portion of DDGS has shown to protect Met from degradation when analyzed in vitro but has not been assessed in vivo. Thus, the primary objective of this study was to evaluate the bioavailability of EMT 3.4 via dilution of selenomethionine (SeMet) in milk protein and secondarily its impact on milk production and body composition. Dietary selenium (Se) yeast will deliver SeMet to the intestines and subsequently be absorbed. After adequate time feeding Se yeast, SeMet will label the different pools of Met similar to feeding radiolabeled nitrogen (N). Once pools of Met are labeled with SeMet, milk Se, a proxy for SeMet, can be measured in the milk. Concentrations of milk Se will fluctuate based on entry of Met, and as Met increases in the milk, the concentration of Se will decrease. To asses bioavailability milk Se is divided by milk N (Se:N) and the ratios of the treatments can be compared.</p> <p>The objective of this study was to evaluate the bioavailability of a novel rumen protected Met product and its effect on milk production and body composition compared to positive and negative controls. Dietary treatments consisted of a negative control treatment (NCT), not supplemented with RPM, a positive control treatment (PCT), supplemented Met via Smartamine M, and the experimental Met treatment (EMT), supplemented Met via EMT 3.4. Cattle fed PCT and EMT exhibited improved bioavailability indicated by a reduction in milk Se to milk N ratio when compared to NCT cows. Using milk Se concentration as an indicator of entry rate and amount of Met in the milk pool, PCT cows had a significantly lower milk Se concentration compared to NCT. Lower milk Se concentration of PCT cows indicates greater amount of Met in milk and subsequently a significantly greater milk protein yield was observed in PCT. Although EMT had similar bioavailability to PCT, the EMT cows had an intermediate response in milk Se but no production responses. The lack of production responses in EMT was observed alongside an elevated milk urea nitrogen (MUN) and a negative change in longissimus dorsi depth (LDD). A negative change in body weight (BW) was observed in NCT cows. Changes in body composition, as the ones observed in this study, are not usually observed unless cattle are energy or protein deficient. Given that diets of this study were formulated to meet requirements for producing 40 kg/day of milk and on average cattle were producing less, it is unlikely that cattle were energy or protein deficient. Results demonstrated that EMT provided similar Met bioavailability as Smartamine M in PCT demonstrated by responses in milk Se:N. The PCT tended to increase milk yield and increased milk protein, whereas EMT provided no observable production responses in this study.</p> <p><br></p>

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<p dir="ltr">The objective of the experiments conducted for this dissertation was to investigate the effects of exogenous enzymes on nutrient digestibility for broiler chickens and growing pigs. These experiments covered the effects of phytase, protease, and carbohydrases on the nutrient availability of various diet types and ingredients, as well as evaluations of regression methods for determining ingredient energy values. One study investigated a factorial of phytase and dietary phytate levels on the ileal digestibility of amino acids (AA) and phosphorus (P) for broilers and pigs. The results of these experiments indicated that phytase improved the ileal digestibility of P (P < 0.05) and all AA (P < 0.05) for broilers regardless of the dietary phytate level, and the ileal digestibility of P (P < 0.05) and many economically important AA (P < 0.05) for pigs. This study did not reveal any significant interactions between phytase and dietary phytate, but there were a number of numerical differences in the relative effect of phytase in the two diet types. In a subsequent experiment the effects of a factorial of phytase and protease on ileal P and AA digestibility were evaluated for growing pigs. Similarly to the first study, phytase was shown to improve the ileal digestibility of P (P < 0.05) and a majority of AA (P < 0.05). There were limited main effects of protease, however, it was found to decrease the digestibility of Lys, Met, and Thr (P < 0.05). There were a number of significant quadratic interactions (P < 0.05) of protease within phytase level, where the necessary concentration of protease to elicit positive effects was dependent on phytase inclusion. The next study evaluated the effects of two carbohydrase blends on the ileal AA digestibility and energy values of soybean meal. Both enzyme blends elicited modest improvements in the ileal and total tract digestibility of energy, but there were limited effects on the energy values of the test diets. Both enzyme blends improved the apparent metabolizable energy of soybean meal, but the blend with lower activity and no protease inclusion produced the greater results with an improvement of 15.2%. These enzyme blends resulted in the improved ileal digestibility of nearly all AA from soybean meal for broilers. The last study was a validation of the three-point model for the regression method against a four-point model over both the same test ingredient inclusion range or smaller range. This evaluation used both canola meal and wheat as test ingredients to evaluate if changes in dietary energy or protein levels affect the results of this method, which are representative of both cereal grains and protein concentrates, respectively. The results indicated that there was no difference in the three and four-point models for either ingredient as long as the overall range of test ingredient concentration was the same in both models. This proved more important for canola meal, as it was more susceptible to problems with the estimates or variability based on changes in inclusion. Based on the results of these experiments, it is clear that phytase can improve the AA digestibility for both pigs and chickens, but care must be taken when combinations are made with protease. These data indicate that the use of carbohydrase blends can improve the nutrient availability of soybean meal, and this could have significant implications in diet formulation. Lastly, the use of the three-point model for the regression method is appropriate, but is dependent on the inclusion level of the test ingredient test ingredient.</p>

This study evaluated the effects of an antibiotic (oxytetracycline HCL) on reproductive performance of turkey breeder hens. The antibiotic was administered in 1) drinking water or 2) drinking water and intravaginal infusion. Hens were assigned to fertility subclasses (low 0-70%, medium 71-90%, high 91-100%) based on performance from the 7th to 10th week of production. Hens receiving antibiotic in drinking water showed significantly higher apparent fertility than untreated controls, but had significantly higher early embryonic mortality than hens receiving antibiotic in water plus intravaginal infusion. In order to determine the duration of the effect of antibiotic treatment on the variables under study, the eggs were divided into two periods; one containing eggs laid during treatment periods and one week following treatment periods, and the second containing eggs laid two to four weeks post-treatment. The antibiotic in drinking water significantly improved hatchability during the treatment period. The antibiotic in drinking water plus intravaginal infusion had its greatest effect in reducing early embryonic mortality. This treatment had a longer term effect holding embryonic mortality below 10% during treatment and post-treatment periods, while a shorter term effect was observed when antibiotic was administered only in drinking water. In the latter case early embryonic mortality increased significantly during the post-treatment period compared to the treatment period. No correlation was found between mycoplasmal or bacterial population and fertility subclass or antibiotic treatment. Hen day and hen housed production, body weight, feed consumption, feed consumed per egg, egg weight and specific gravity were unaffected by antibiotic treatment. / M.S.