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Title:The effect of rumen- protected protein and amino acids, and genetic milk casein polymorphism on dairy cows’ performance
Author(s):Rivelli Bixquert, Maria Ines
Director of Research:Cardoso, Felipe C.
Doctoral Committee Chair(s):Cardoso, Felipe C.
Doctoral Committee Member(s):Cecava, Michael; Stein, Hans H.; Drackley, James K.; Doane, Perry H.
Department / Program:Animal Sciences
Discipline:Animal Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):nitrogen efficiency
rumen-protected AA
rumen-protected protein, milk protein polymorphism
Abstract:As world population increases, food security is an issue that needs to be addressed. There is a need to produce more food, particularly protein, to feed the growing population and lower hunger and diminish food insecurity. One of FAO (2018) targets is “ by 2030, end hunger and ensure access by all people, in particular the poor and people in vulnerable situations, including infants, to safe, nutritious and sufficient food all year round”. Food security is linked not only to food quantity but also quality. Therefore, the question is: how, we, as animal scientists are going to address this objective? Improving dairy industry’s production, particularly N efficiency, can effectively improve the supply of milk and reduce ammonia emissions per unit of milk. Furthermore, a more ample knowledge on genetic milk protein variants could help to improve milk yield efficiency. Rumen protected (RP) technologies could help to lower the total amount of CP offered, and enhance milk production and N efficiency. The aim of a first study was to determine the effects of two RUP sources (processed soybean meal or a processed blend of canola meal and soybean meal) on digestibility, degradability, and performance of lactating dairy cows. Cows fed a RUP source based on canola and soybean meal (TCSM) had greater milk lactose concentrations and casein (CN) as a percentage of protein than cows fed a RUP source based on soybean meal (TSBM); and lower BHB and MUN concentrations compared to cows not receiving a RUP source (CON) and TSBM. Nitrogen intake was lower for cows fed TCSM, they had greater milk nitrogen efficiency compared to cows fed CON and a tendency for lower urinary N excretion as a percentage of N intake than cows fed TSBM. Results suggested that diets containing certain type of RUP have the potential for improving milk CN concentration and N utilization, thereby reducing potential negative impacts on the environment. In a second study, 2 experiments were carried out. The objective of the first experiment was to test 8 encapsulated RP Lys prototypes (ADM). The second experiment had the objective to determine the short-term effects of RP and post-ruminal Lys (NPL) supplementation to dairy cows on protein and AA in blood, production of milk, and milk components. Plasma Lys concentration as a percentage of total amino acids was greater for cows fed a commercially available RP Lys (Ajinomoto) source throughout both experiments. There were no differences in plasma Lys concentration as a percentage of indispensable amino acids between cows fed the commercially RP Lys source and certain NPL prototypes. Cows fed NPL had greater milk yield and milk protein yield than cows fed the commercially RP Lys source. Lastly, a third study was performed to evaluate the correlation between Holstein cow’s genetic milk protein variants and diet (RDP) composition on feed intake and milk yield. We hypothesized that milk and milk protein yield differences among Holstein cows are due to the differences in dietary RDP:RUP proportions and not to cows’ genetic milk protein variant. Results indicated that under the conditions of the present study, cows fed lesser RDP and greater RUP proportions had greater milk, milk protein, casein, and lactose yields. There were no differences for casein as a percentage of protein between cows fed lesser or greater RDP proportions. Hence, diet manipulation, particularly RDP:RUP ratio, is a promising strategy to enhance milk and milk products quality. There were differences in casein as a percentage of protein and numerical differences in milk and protein yield between homozygotes and heterozygotes for the three casein genetic variants (α, β, and κ). Selecting herds for desired milk protein alleles such as B_B homozygotes κ-CN, β-LG, and A1_A1 β-CN could beneficially impact the dairy industry by enhancing milk yields that yield greater quality and quantity cheese. Milk and milk protein yields differences were found between A1_A1 and A2_A2 cows but the genetic polymorphism of bovine β-CN and the impact of these two variants on human health still remains an open matter.
Issue Date:2019-07-03
Type:Text
URI:http://hdl.handle.net/2142/105622
Rights Information:Copyright 2019 Ines Rivelli
Date Available in IDEALS:2019-11-26
Date Deposited:2019-08


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