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.

Beef cows' milk yield is typically determined by measuring milk yield once daily and then doubling this value to estimate daily production. However, it is not known whether this is accurate. Thus, we aimed to determine the association between morning and afternoon milk yield in grazing Nellore cows. Eighty Nellore cows were used, with initial weight of 516.0 ± 1.0 kg. The experiment was a completely randomized factorial scheme, with 20 replications and four treatments (i.e., + or - pre-partum supplementation in combination with + or - post-partum supplementation): PRMM-1 kg of supplement/cow/day for 90 days pre-partum; MMPS-1 kg of supplement/cow/day for 90 days post-partum; PRPS-1 kg of supplement/cow/day for 90 days pre-partum and 90 days post-partum; and MM-only mineral mix ad libitum during pre- and post-partum. Milk was sampled on days 45, 135, and 225 post-partum (early, middle, and late lactation, respectively). No effects were observed of pre- and post-partum supplementation on milk yield (P > 0.05). The afternoon/morning proportion of 0.45 in the early third of lactation was higher than other stages, which had a proportion of 0.41 (P < 0.05). Post-partum supplementation increased milk protein in the morning and afternoon milking (P < 0.05). There was also no effect of pre- and post-partum supplementation on afternoon-morning proportion other milk components (P> 0.05). We conclude that estimating daily milk production of grazing beef cattle by multiplying a once daily milking amount times two is not accurate. Under the conditions of this study, proportion of total daily production represented by the ratio of afternoon/morning milking was 0.45 in early lactation (first third) and 0.41 in mid- and late lactation.

The objective of this study was to estimate the nutritional requirements of energy and protein in crossbred (Holstein × Zebu) bulls. An experiment of comparative slaughter was conducted with 44 (24 months old) crossbred bulls of 338 ± 39 kg. Bulls were randomly separated as follows: four bulls to the control group, four bulls to the maintenance level group and 36 bulls were fed ad libitum. Corn silage (CS) and sugar cane in natura (SC) at 60 or 40% of dry matter (DM) of total diets were utilized in the diets. The bulls of the last group were randomly assigned to one of six different diets: 1) 60CS:40C(84 days); 2) 60CS:40C (42 days) and 40CS:60C (42 days); 3) 40CS:60C (84 days); 4) 60SC:40C (84 days); 5) 60SC:40C (42 days), and 40SC:60C (42 days), and 6) 40SC:60C (84 days). At the end of the experiment, bulls were slaughtered at Universidade Federal de Viçosa for estimation of the empty body weight. One sample located between the 9 th and the 11 th ribs of each bull was taken and completely dissected for estimation of the empty body composition using equations developed by BR-CORTE 2010. The data were analyzed as nonlinear models built by means of command NLIN of SAS (version 9.2), adjusted by the method of Gauss-Newton. For all the tests, 0.05 was utilized as critical level for probability of type I error. The net (NE m ) and metabolizable (ME m ) energy requirements for maintenance were 78. libitum. Foram utilizadas a silagem de milho (SM) e a cana-de-açúcar in natura (CA) nas proporções de 60 ou 40% na base da matéria seca (MS) total das dietas. As seis dietas experimentais foram constituídas da seguinte forma: 1) 60 SM: 40% de concentrado (C) durante 84 dias; 2) 60SM: 40C (42 dias) e 40SM:60C (42 dias); 3) 40SM:60C (84 dias); 4) 60CA:40C (84 dias); 5) 60CA:40C (42 dias) e 40CA:60C (42 dias) e 6) 40CA:60C (84 dias). Ao final do experimento, todos os animais foram abatidos para determinação do peso de corpo vazio (PCVZ). Uma amostra compreendida entre a 9ª e a 11ª costelas da meia carcaça esquerda foi retirada e completamente dissecada para a estimação da composição química do PCVZ utilizando as equações descritas no BR-CORTE em 2010. Os dados foram analisados como modelos não lineares elaborados por médias do comando NLIN do SAS (versão 9.2), ajustados pelo método de Gauss-Newton. Para todos os testes, 0.05 foi utilizado como nível crítico de probabilidade para o erro tipo I. As exigências de energia líquida (EL m ) e metabolizável (EM m ), para mantença foram de 78,7 e 114,2 kcal/PCVZ 0,75 /dia, respectivamente. A k m foi de 0,6891. As equações obtidas para as exigências líquidas para ganho de energia (EL g ) e proteína (PL g ) foram: EL g (Mcal/dia) = 0,0493 × PCVZ 0,75 × GPCVZ 1,0013 e PL g (g/dia) = 279,19 × GPCVZ -22,8691 × ER, respectivamente. A k g foi de 0,4634. As eficiências de utilização da energia metabolizável para a deposição de proteína e gordura foram de 0,2048 e 0,8848, respectivamente. O modelo obtido para a percentagem de energia retida na forma de proteína (%ER p ) foi: %ER p = 1,7...