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Ajuste do peso corporal de bovinos para condições fisiológicas e de alimentação ……………………………………………………………….

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An experiment was conducted to evaluate intake and nutrient digestibility, performance, milk composition, and microbial efficiency of Nellore cows and their calves during lactation. Fifteen Nellore cows were fed corn silage and concentrate (85:15). After calving, calves were kept with their dams for 2 months then separated and housed in individual pens adjacent to their dams. Cows were milked every 15 days over 7 months to estimate milk intake of the calves. During lactation, nutrient intake decreased (P < 0.01) for cows, while nutrient digestibility increased (P < 0.001). Starting 2 months post-calving, calves were offered concentrate (5 g/kg body weight (BW)) and roughage. An increase in DM digestibility was observed for calves in the third month of age, probably due to an associative effect between milk, concentrate, and roughage, which increased DM digestibility without increasing DM intake. Average daily gain (ADG) of the calves increased (P < 0.001) during lactation period. Microbial efficiency (g mCP/kg total digestible nutrients (TDN)) did not change (P > 0.05) in either cows or their calves during lactation period. However, nutrient digestibility decreased for calves during this period. Nellore cows produced milk with average of 4.58 % lactose, 5.61 % fat, and with milk protein increasing from 3.6 to 4.0 % as lactation progressed.

This study investigated how feeding regimen (FR) alters apparent total-tract digestibility, performance, N balance, excretion of purine derivatives, and fat deposition in Holstein × Gyr cows at different days of gestation (DG). Forty-four pregnant multiparous Holstein × Gyr cows with an average initial body weight of 480±10.1 kg and an initial age of 5±0.5 yr old were allocated to 1 of 2 FR: ad libitum (AL; n=20) and maintenance level (ML; n=24). Maintenance level was considered to be 1.15% of body weight on a dry matter (DM) basis and met 100% of the energy requirements, whereas AL provided 190% of total net energy requirements. Data for hot and cold carcass dressing, fat deposition, average daily gain, empty body gain, and average daily gain without the gravid uterus were analyzed as a 4×2 factorial design. Intake, apparent total-tract digestibility, N balance, urinary concentration of urea, and purine derivatives data were analyzed as repeated measurements taken over the 28-d period (122, 150, 178, 206, 234, and 262 d of gestation). Cows were individually fed a corn silage-concentrate based diet composed of 93% roughage and 7% concentrate (DM basis) as a total mixed ration. Pregnant cows were slaughtered on 4 different DG: 139 (n=11), 199 (n=11), 241 (n=11), and 268 d (n=11). Overall, DM intake decreased as DG increased. This decrease observed in DM intake may be associated with the reduction in ruminal volume caused by the rapid increase in fetal size during late gestation. We observed an interaction for DM and organic matter apparent total-tract digestibility between FR and DG; at 150, 178, and 206 d of gestation, ML-fed cows had greater DM and organic matter apparent total-tract digestibility values than AL-fed cows. Rib fat thickness, mesentery, and kidney, pelvic, and heart fat were greater in AL-fed than in ML-fed cows at all DG, with the exception of rib fat thickness on d 139. Ad libitum-fed cows excreted more N in their feces and urine compared with ML-fed cows. Pregnant cows that were fed at maintenance had greater digestibility during some DG, excreted less N in feces and less N and urea in urine, and deposited less fat in the body. We therefore recommend ML (1.15% of body weight with 93% of roughage) as a FR for pregnant dry cows; however, during the last month of gestation, AL seems to be the most appropriate FR to avoid loss of body weight.

The objective of this experiment was to assess ruminal outflow and apparent total-tract digestibility using digesta samples from 3 sites (reticulum, omasum, and abomasum) and 3 marker methods (single marker: indigestible NDF [iNDF; sample without separation]; double marker: iNDF + Co-EDTA [filtered sample]; and triple marker: iNDF + ytterbium [Yb] acetate + Co-EDTA [filtered and centrifuged]) in bulls fed corn silage and sugarcane-based diets. Eight crossbred (Holstein × Zebu) bulls (353 ± 37 kg of BW; 24 ± 1 mo of age) with ruminal and abomasal cannulas were randomly distributed into two 4 × 4 Latin squares that were balanced for residual effects. The following experimental diets were used: 1) 60% corn silage + 40% concentrate, 2) 40% corn silage + 60% concentrate, 3) 60% fresh sugarcane + 40% concentrate, and 4) 40% fresh sugarcane + 60% concentrate. Reticular, omasal, and abomasal digesta samples were collected at 9-h intervals over 3 d. At the end of the experiment, a composite sample was prepared for each bull, and these samples were subsequently assigned to the 3 marker methods. The concentrations of CP, NDF, and iNDF of reticular digesta differed (P < 0.01) from those of the omasum and abomasum. Use of omasal and abomasal samples led to similar estimates of ruminal outflow and ruminal digestibility for DM (P = 0.65), OM (P = 0.68), CP (P = 0.85), and NDF (P = 0.57). In contrast, the ruminal outflow of digesta based on reticular sampling appeared to be underestimated. We recommend sampling from the omasum because sampling from this region is less invasive than sampling from the abomasum. Although we did not observe differences in ruminal NDF digestibility among the different marker methods, we did observe that ruminal digestibility of CP was greater for the single marker method than for the double and triple marker methods; we therefore recommend the use of the double or triple marker method.

-The objective of this study was to estimate the urinary creatinine excretion by the shrunk body weight (SBW). In experiment I, 32 Nellore bulls with initial body weight of 259±24.9 kg and 14±1 months-old were used. The group was divided in four animals to maintenance and twenty eight animals feeding ad libitum and separated in four groups; each group was slaughtered at different times of feedlot (42, 84, 126 and 168 days). The diet was composed of corn silage and concentrate (55:45). Before the slaughters, the total urinary collection was realized during three days. A database of creatinine excretion was collected from other five studies that had been conducted with Nellore cattle. In all the studies, the total urinary collection was realized during at least three days. At the end of each collection, the animals were weighted.Urinary creatinine excretion (UCE) was related with the shrunk body weight and it can be estimated by the equation: UCE (g/day) = 0.0345 × SBW 0.9491 .

RESUMO -Este trabalho foi conduzido com os objetivos de determinar as frações A e B e a taxa de degradação ruminal (Kd) da matéria seca (MS) e da proteína bruta (PB) de 27 alimentos e avaliar a digestibilidade intestinal da proteína não-degradada no rúmen pelas técnicas do saco de náilon móvel e de três estágios. Os alimentos avaliados foram farelos de arroz, babaçu, gérmen de milho e trigo; milho desintegrado com palha e sabugo, milho desintegrado com sabugo, milho, polpa cítrica, sorgo, amireia, farelos de algodão com 28, 38 e 46% de PB, farelos de amendoim, girassol e soja; feijão-bandinha, glúten de milho, grão de soja, levedura, promil, refinazil, cascas de cacau, café e soja e silagens de capim-elefante e milho. Para obtenção da degradabilidade ruminal da MS e PB dos alimentos, utilizaram-se sacos de náilon de 10 × 20 cm e os tempos de incubação de 0, 2, 4, 6, 12, 16, 24, 48 e 72 horas. A digestibilidade intestinal foi determinada pelas técnicas do saco de náilon móvel e de três estágios. Os dados de degradação ruminal da matéria seca e da proteína bruta, em sua maioria, estão de acordo com a literatura. A técnica dos três estágios não estimou de forma satisfatória a digestibilidade interstinal de todos os alimentos estudados em conjunto, mas foi adequada para os alimentos proteicos. A maioria dos alimentos possui aproximadamente 90% de digestibilidade da PB, com exceção das cascas de soja, café e cacau e das silagens de milho e capimelefante. A técnica de três estágios estimou corretamente a digestibilidade intestinal dos alimentos proteicos, mas recomenda-se a utilização da equação DIPB (%) = -5,1906 + 1,1053 × X para corrigir a digestibilidade obtida pela técnica dos três estágios para alimentos não-proteicos.Palavras-chave: babaçu, feijão, promil, saco de náilon móvel, subprodutos da indústria, três estágios Rumen degradation and intestinal digestibility of crude protein in feeds for cattleABSTRACT -The objective of the present study was to determine the A and B fractions and the rumen degradation rate (Kd) of dry matter (DM) and crude protein (CP) in 27 feeds and determine the intestinal digestibility of non-degraded rumen protein by the three steps and mobile nylon bag techniques. Rice meal, babassu meal, wheat and corn germ, ground corn cobs and straw, ground corn cobs, corn, citrus pulp, sorghum, starea and cottonseed meal with 28, 38 and 46% CP, peanut meal, sunflower meal, soybean meal, bean byproduct, corn gluten, soybean grain, dry yeast, corn gluten meal, cacao hulls, coffee hulls, soybean hulls, elephant-grass silage and corn silage were sampled. To obtain the ruminal degradation of DM and CP, 10 × 20 cm nylon bags with incubation times of 0, 2, 4, 6, 12, 16, 24, 48 and 72 hours were used. The intestinal digestibility was determined by the three steps and the mobile nylon bag techniques. The ruminal degradation data of the dry matter and crude protein were similar to the literature. The three step technique did not estimate properly the intestinal digestibility of all the feeds evaluated, exc...