This study aims to evaluate the effect of the Tifton 85 hay (Cynodon dactylon L. Pers) replacement by Orelha de Elefante Mexicana spineless cactus (Opuntia stricta [Haw.] Haw) on the nutrient intake and digestibility, growth performance, microbial protein synthesis, and efficiency of dietary nitrogen compound utilization in the diets of Girolando heifers. Twenty-four (3.5 months and 100 kg ± 3.5 kg) Girolando heifers (5/8 Holstein x Gyr) were used and arranged in a completely randomized design. Dry matter, organic matter, crude protein, and neutral detergent fiber decreased linearly as a function of the levels of Tifton hay (TH) replacement by Orelha de Elefante Mexicana spineless cactus (OEM). The non-fiber carbohydrate intake and coefficient of dry matter digestibility increased, while the neutral detergent fiber (NDF) digestibility decreased linearly with the OEM inclusion. After evaluating the growth performance by observing weight gain and morphometric measurements, there were no significant alterations. The urinary volume, nitrogen balance as well as the efficiency of nitrogen retention had increased, while the urinary and plasma urea concentrations had decreased linearly with the OEM inclusion. The results obtained in this study show that Orelha de Elefante Mexicana spineless cactus should replace Tifton hay in post-weaned heifer diets.

The objective of this work was to evaluate the effects of different levels of sugarcane bagasse, as exclusive roughage, on nutrient intake and digestibility, feeding behavior, microbial protein synthesis, and dairy performance of crossbred cows. Ten lactating Girolando breed cows (600±34.3 kg body weight) were assigned to a replicated 5×5 Latin square design. The control diet, based on spineless cactus, sugarcane bagasse, and concentrate, was formulated to meet the average production of 20 kg of milk per day, with 3.5% fat. The evaluated levels of sugarcane bagasse were: 30, 38, 46, and 54% dry matter bases. The intake and digestibility of dry matter decreased linearly with sugarcane bagasse levels. Rumination time was higher in cows fed 54% sugarcane bagasse. The inclusion levels had no effect on non-esterified fatty acid contents or on the efficiency of microbial protein synthesis, but beta-hydroxybutyrate concentrations showed a quadratic pattern to the bagasse levels. Higher yields of 3.5% fat-corrected milk were obtained with cows fed 30% sugarcane bagasse. Sugarcane bagasse inclusion in the diet of crossbred dairy cows decreases their performance; however, the bagasse can be used as exclusive roughage when associated with 70% concentrate.

Little is known about milk fatty acid (FA) profile of cows fed diets based on sugarcane (Saccharum officinarum L.) bagasse. This study aimed to evaluate FA profile and nutritional quality indexes of milk fat of cows fed sugarcane bagasse and concentrate in the Brazilian northeast semiarid region. Multiparous Girolando cows were allocated in four diets based on different levels of sugarcane bagasse (30%, 38%, 46%, and 54% total DM) added to concentrate. Fatty acids C18:1 trans-11 (lowest value for 46% inclusion) and conjugated linoleic acid (CLA) cis-9, trans-11 (lowest value for 46% inclusion) in milk fat presented a quadratic pattern (P < 0.05). This trend was also observed for C18:1 cis-9 (P < 0.05), but at a lower magnitude. There was a reduction in concentration of C18:1 trans-10 (0.320 to 0.148 g 100 g-1 total FA) and CLA trans-10, cis-12 (0.008 to 0.004 g 100 g-1 total FA) according to the levels of sugarcane bagasse increase. The greater inclusion of bagasse and consequent reduction in the proportion of concentrate, notably corn, cause an increase in concentration of medium-chain saturated FA and a linear reduction of C18:3 n-3 and C18:2 n-6, with a consequent increase in the indexes of atherogenicity (2.82 to 3.2) and thrombogenicity (3.39 to 3.84) and a decrease in ratio of hypo/ hyper-cholesterolemic (0.44 to 0.37) and ω-6:ω-3 (12.44 to 8.80) in milk fat. Results indicate that different levels of sugarcane bagasse change the FA content in cows' milk when bagasse is an exclusive roughage source in the diet. The greater inclusion of sugarcane bagasse reduces the quality of milk fat of dairy cows. The lowest level of sugarcane bagasse inclusion tested (30%) promotes greater milk yield and healthier milk fat.

O trabalho foi realizado com o objetivo de avaliar o teor de caseína e albumina no leite de vacas da raça Girolanda em diferentes fases de lactação. O período experimental teve duração de 45 dias (dezembro/2005 a janeiro/2006), dividido em duas fases: I-avaliação o teor de caseína e albumina; II-investigação os efeitos de climatização, número de ordenha, alimentação e manejo. Os resultados indicam redução do teor de proteínas, e consequentemente, redução da quantidade de caseína e aumento proporcional do teor de albumina. Concluiu-se que vacas Girolanda alimentadas a base de capim-elefante, silagem de milho e farelo de algodão elevou o teor de proteínas.

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