No description available.

<p>(From abstract) </p> <p>In the first study, the urine collection method was effectively applied for evaluation of intestinal permeability using Cr-EDTA, an indigestible oral marker, demonstrating the applicability of the procedure in 1-week-old and 6-week-old neonatal heifer calves (n=15 calves). Calf health observations were recorded during the entire urinary catheterization process and collection period to evaluate any negative health reactions to the procedure, or localized reactions. Proportion of localized reactions were analyzed, and the proportions did not exceed 20% for the calves catheterized at either 1 week or 6 weeks of age. </p> <p>In the second study, the developed catheterization procedure and urine collection method was applied using Cr-EDTA as an oral marker to investigate if L-GLN supplementation would offer improvement to intestinal permeability. In this larger study, 30 Holstein heifer calves [1.5 ± 0.5 days old; 37.1 ± 0.86 kg body weight (<strong>BW</strong>)] were blocked by serum total protein, BW, and age, and randomly assigned to 1 of 2 treatments: <strong>GLN</strong> [24% crude protein (<strong>CP</strong>)], 17% fat milk replacer (<strong>MR</strong>) +10 g L-GLN/kg MR powder) or <strong>NS</strong> (24% CP, 17% fat MR). MR was reconstituted to 12.5% solids with warm water and fed 3.8 L/calf/d until weaning. Calves were weaned at 56.4 ± 0.5 days of age, and had <em>ad libitum</em> grain (17% CP, 2% fat) and water access throughout the experimental period.</p> <p>During the preweaning period, calves were individually housed in hutches and health observations, which included respiratory and fecal scores, were assessed daily. Body weight was measured weekly, and grain and MR intake was assessed daily to calculate average daily gain (<strong>ADG</strong>), average daily feed intake [<strong>ADFI</strong>; grain intake (dry matter (<strong>DM)</strong> basis) + MR intake (DM basis)], and feed efficiency (<strong>G:F</strong>; ADG:ADFI). At weaning, calves were weighed, moved to pens (n = 3 pens/treatment, 4-5 calves/pen), provided free access to grain and grass hay, and then weighed 2 weeks post-weaning. Additionally, urinary catheters were placed at 1 and 6 weeks of age, and calves were orally dosed with 1 L Cr-EDTA in their MR. Urine samples were then collected over a 24-hr period for Cr output analysis as an <em>in vivo</em>biomarker of intestinal permeability. </p> <p>Blood was collected on study days 1, 2, 5, 7, 14, 21, 42, 56, and 70 to measure haptoglobin, serum amyloid A, leukocyte data, neutrophil: lymphocyte (<strong>N:L</strong>), glucose, non-esterified fatty acids, insulin, and cortisol. Two study periods were identified for data analysis representing greater (<strong>P1</strong>; weeks 1-3) and reduced (<strong>P2</strong>; weeks 4-8) enteric disease susceptibility. Data were analyzed using PROC GLIMMIX or PROC MIXED in SAS 9.4 with calf as the experimental unit. There was a decrease in total preweaning Cr output (<em>P</em> < 0.05) for GLN calves, and Cr output in 1 week old calves was decreased (<em>P</em> = 0.04) in GLN versus NS calves. The N:L was decreased overall (<em>P</em> = 0.03) and during P2 (<em>P</em> = 0.01) and P2 neutrophil count tended to be reduced (<em>P</em> = 0.07) in GLN versus NS calves. There were no MR treatment differences for ADFI, ADG, body measurements, post-absorptive metabolic biomarkers, disease scores, and therapeutic treatments (<em>P</em> > 0.10). In summary, L-GLN supplementation improved intestinal integrity and biomarkers of physiological stress in pre-weaned Holstein heifer calves managed under production-relevant conditions.  </p>

O rebanho brasileiro de bovinos leiteiros é composto predominantemente por vacas mestiças criadas em condições tropicais. Os principais modelos usados no Brasil para a formulação e avaliação de dietas são norte-americanos e baseados nas exigências de vacas Holandesas em clima temperado. A principal contribuição do primeiro capítulo deste estudo foi o desenvolvimento e avaliação de um novo modelo para estimar a ingestão de matéria seca (IMS) de vacas mestiças. A nova equação de predição da IMS foi desenvolvida e avaliada usando um banco de dados com 161 médias de tratamentos provenientes de 38 estudos brasileiros publicados com vacas mestiças [n = 446 vacas, 16,60 ± 5,70 (DP) kg leite/dia]. O modelo proposto foi: IMS (kg/dia): [0,5552 (± 0,06636 EP) × LC4%G + 0,06332 (± 0,009455) × PV0,75] × [1 - e (- 0,7732 (± 0,7019) × (SEM - 1,629 (± 1,9313))) ]. O novo modelo apresentou maior acurácia (QMEP = 1,64, r2 = 0,88) na predição da IMS quando comparado com modelos norte-americanos. O novo modelo de predição da IMS pode ser aplicado na formulação de dietas para vacas leiteiras mestiças em condições tropicais. No capítulo 2, um estudo avaliou as novas atualizações das exigências nutricionais de bezerras leiteiras sugeridas por Van Amburgh e Drackley (2005) e inseridas em programa comercial (AMTS, Agricultural Modeling and Training Systems, AMTS.Cattle.ProTM Calf Model versão 3.5.8.0, 2015). Dados de 16 estudos brasileiros envolvendo 51 dietas para bezerros leiteiros (n = 485, peso ao desmane de 62,02 ± 10,16 kg) foram usados para avaliar os modelos do NRC (2001) e o AMTS. Nas condições do conjunto de dados do presente estudo, ambos os sistemas superestimaram o ganho calculado a partir da proteína disponível. O ganho de peso estimado pela energia disponível da dieta, foi superestimado em 19 g/dia quando calculado pelo NRC e subestimado em 68 g/dia quando calculado pelo AMTS. O ganho de peso possível a partir da energia disponível foi menor quando calculado pelo AMTS em relação ao NRC (2001). Para o conjunto de dados experimentais brasileiros, os ganhos de peso de bezerros foram 32% inferiores aos descritos na literatura para sistemas norte-americanos. As razões para esta discrepância precisam ser compreendidas, pois somente assim novos modelos poderão ser desenvolvidos e parametrizados para estimar o desempenho animal de forma mais acurada e precisa. / The Brazilian dairy herd is mainly made up of crossbred cows fed under tropical conditions. The main models in use to formulate and evaluate diets in Brazil are from North America. These models are based on the requirements of Holstein dairy cows under temperate climate. Therefore, the main contribution of this first Chapter was the development and evaluation of a new model to estimate dry matter intake (DMI) of crossbred dairy cows. The new DMI equation was developed and evaluated using a database with 161 treatment means from 38 published studies of Brazilian crossbred cows [n = 446 dairy cows, mean milk production of 16.60 ± 5.70 (SD) kg/day]. The new model showed higher DMI prediction accuracy (MSEP = 1.64, r2 = 0.88) than American models. Therefore, this model can be used in the formulation of diets for crossbred dairy cows under tropical conditions. In Chapter 2, we evaluated the updates on the nutritional requirements of dairy calves suggested by Van Amburgh and Drackley (2005) and inputted into Agricultural Modeling and Training Systems (AMTS, AMTS.Cattle.ProTM Calf Model version 3.5.8.0, 2015). Data from 16 previous Brazilian studies involving 51 diets for dairy calves (n = 485 calves, weaning weight of 62.02 ± 10.16 kg) were used to evaluate the Nutrient Requirements of Dairy Cattle - NRC (2001) and AMTS models. According to the data set from this study, both systems overestimated the gain calculated from the available protein. The weight gain estimated by the energy available from the diet was overestimated by 19 g/day when calculated by the NRC and underestimated by 68 g/day when calculated by AMTS. Weight gain estimated by the dietary energy of the AMTS system was lower than the NRC (2001). The Brazilian data set showed a calf gain around 32% lower than those described in U.S. dairy farms. The reasons for this discrepancy need to be understood, for only then can new models be developed and parameterized to estimate animal performance more accurately and precisely.

O rebanho brasileiro de bovinos leiteiros é composto predominantemente por vacas mestiças criadas em condições tropicais. Os principais modelos usados no Brasil para a formulação e avaliação de dietas são norte-americanos e baseados nas exigências de vacas Holandesas em clima temperado. A principal contribuição do primeiro capítulo deste estudo foi o desenvolvimento e avaliação de um novo modelo para estimar a ingestão de matéria seca (IMS) de vacas mestiças. A nova equação de predição da IMS foi desenvolvida e avaliada usando um banco de dados com 161 médias de tratamentos provenientes de 38 estudos brasileiros publicados com vacas mestiças [n = 446 vacas, 16,60 ± 5,70 (DP) kg leite/dia]. O modelo proposto foi: IMS (kg/dia): [0,5552 (± 0,06636 EP) × LC4%G + 0,06332 (± 0,009455) × PV0,75] × [1 - e (- 0,7732 (± 0,7019) × (SEM - 1,629 (± 1,9313))) ]. O novo modelo apresentou maior acurácia (QMEP = 1,64, r2 = 0,88) na predição da IMS quando comparado com modelos norte-americanos. O novo modelo de predição da IMS pode ser aplicado na formulação de dietas para vacas leiteiras mestiças em condições tropicais. No capítulo 2, um estudo avaliou as novas atualizações das exigências nutricionais de bezerras leiteiras sugeridas por Van Amburgh e Drackley (2005) e inseridas em programa comercial (AMTS, Agricultural Modeling and Training Systems, AMTS.Cattle.ProTM Calf Model versão 3.5.8.0, 2015). Dados de 16 estudos brasileiros envolvendo 51 dietas para bezerros leiteiros (n = 485, peso ao desmane de 62,02 ± 10,16 kg) foram usados para avaliar os modelos do NRC (2001) e o AMTS. Nas condições do conjunto de dados do presente estudo, ambos os sistemas superestimaram o ganho calculado a partir da proteína disponível. O ganho de peso estimado pela energia disponível da dieta, foi superestimado em 19 g/dia quando calculado pelo NRC e subestimado em 68 g/dia quando calculado pelo AMTS. O ganho de peso possível a partir da energia disponível foi menor quando calculado pelo AMTS em relação ao NRC (2001). Para o conjunto de dados experimentais brasileiros, os ganhos de peso de bezerros foram 32% inferiores aos descritos na literatura para sistemas norte-americanos. As razões para esta discrepância precisam ser compreendidas, pois somente assim novos modelos poderão ser desenvolvidos e parametrizados para estimar o desempenho animal de forma mais acurada e precisa. / The Brazilian dairy herd is mainly made up of crossbred cows fed under tropical conditions. The main models in use to formulate and evaluate diets in Brazil are from North America. These models are based on the requirements of Holstein dairy cows under temperate climate. Therefore, the main contribution of this first Chapter was the development and evaluation of a new model to estimate dry matter intake (DMI) of crossbred dairy cows. The new DMI equation was developed and evaluated using a database with 161 treatment means from 38 published studies of Brazilian crossbred cows [n = 446 dairy cows, mean milk production of 16.60 ± 5.70 (SD) kg/day]. The new model showed higher DMI prediction accuracy (MSEP = 1.64, r2 = 0.88) than American models. Therefore, this model can be used in the formulation of diets for crossbred dairy cows under tropical conditions. In Chapter 2, we evaluated the updates on the nutritional requirements of dairy calves suggested by Van Amburgh and Drackley (2005) and inputted into Agricultural Modeling and Training Systems (AMTS, AMTS.Cattle.ProTM Calf Model version 3.5.8.0, 2015). Data from 16 previous Brazilian studies involving 51 diets for dairy calves (n = 485 calves, weaning weight of 62.02 ± 10.16 kg) were used to evaluate the Nutrient Requirements of Dairy Cattle - NRC (2001) and AMTS models. According to the data set from this study, both systems overestimated the gain calculated from the available protein. The weight gain estimated by the energy available from the diet was overestimated by 19 g/day when calculated by the NRC and underestimated by 68 g/day when calculated by AMTS. Weight gain estimated by the dietary energy of the AMTS system was lower than the NRC (2001). The Brazilian data set showed a calf gain around 32% lower than those described in U.S. dairy farms. The reasons for this discrepancy need to be understood, for only then can new models be developed and parameterized to estimate animal performance more accurately and precisely.