Estimating purine derivatives and nitrogen compound excretion using total urine collection or spot urine samples in grazing heifers.

The study aimed to evaluate the excretion of purine derivatives (PDs) and nitrogen compounds (NCs) and their ratios with creatinine in supplemented Zebu heifers kept on pastures by comparing total urine collection and spot sampling. Five Nelore heifers (400 ± 15 kg) were used in a 5 × 5 Latin square design. The treatments were the amount of concentrate (220 g of crude protein/kg dry matter) offered (0, 3, 6, 9 and 12 g/kg BW). In each period, the total urine collection was performed continuously for 3 days (subsampled at intervals of 4 h, 00:00-04:00 h, 04:00-08:00 h, 08:00-12:00 h, 12:00-16:00 h, 16:00-20:00 h and 20:00-24:00 h). The spot urine samplings were performed (in each period) for 24 h (0, 4, 8, 12, 16 and 20 h). Creatinine, total urinary nitrogen (UN), urea nitrogen (UreaN), allantoin and uric acid were analysed. Creatinine excretion was 23.01 ± 0.19 mg/kg BW and was not affected by collection day, treatment or their interactions (p > 0.05). Treatments affected (p < 0.05) PD excretions, however did not affect the ratio PD:creatinine (p > 0.05). Treatments and collection time affected (p < 0.05) NC excretion, whereas the UN:creatinine and UreaN:creatinine ratios were not affected (p > 0.05). Creatinine excretion and the PD:creatinine ratios in the urine samples estimated by the total or spot sampling were not different (p > 0.05). However, sampling method affected (p < 0.05) the UN:creatinine and UreaN:creatinine (p < 0.05) ratios. Creatinine can adequately estimate urinary excretion in grazing heifers, and a single spot urine sample at any time of the day can be used to estimate PD excretion in grazing heifers. But two spot urine samples are needed for proper NC excretion estimations in grazing heifers' urine.

Can the body composition of crossbred dairy cattle be predicted by equations for beef cattle?

OBJECTIVE: The aim of the study was to evaluate the efficiency of the Hankins and Howe (HH46), Valadares Filho (V06), and Marcondes (M12) equations for predicting the physical and chemical composition of dairy crossbred bulls carcasses, as well as the chemical composition of their empty bodies. METHODS: This study was conducted using 30 dairy crossbred bulls. One group of five animals was slaughtered at the beginning of the experiment, and the remaining were slaughtered 112 days later. Animals were distributed in a completely randomized design into treatments consisting different levels of concentrate (0%, 17%, 34%, 51%, and 68%). The physical and chemical compositions of the cattle were obtained from the right half of the carcass and using samples taken between the 9th and 11th ribs of the left half of the carcass. The estimated and experimentally determined values were compared using the correlation and concordance coefficient, as well as the mean square error of prediction (MSEP) and its components. RESULTS: The HH46 equations were better at estimating the amount of muscle plus fat in the carcass. The amount of bone in the carcasses could not be well estimated by the HH46 and M12 models. The M12, HH46, and V06 equations were worst at estimating the amounts of protein, ether extract, and water in the carcass, respectively. In the empty body, the amounts of protein and water were well estimated by the HH46 equations. Protein, ether extract, and water were accurately estimated by the V06 equations, and ether extract by the M12 equations. CONCLUSION: The physical and chemical composition of dairy crossbred bull carcasses, as well as the chemical composition of their empty bodies, can be predicted using the equations tested here. The amount of bone in these carcasses could not be accurately predicted.

Nutritional and productive performance of dairy cows fed corn silage or sugarcane silage with or without additives.

The objective of this study was to compare the intake, digestibility, and performance of dairy cows fed corn silage, fresh sugarcane, and sugarcane ensiled in three different forms. Twenty-five Holstein cows at 114 ± 12.6 days in milk (DIM) were used. A randomized block design was adopted, using an arrangement of repeated measures over time. The following treatments were tested: corn silage (CS); fresh sugarcane (FS); sugarcane silage without additives (SCS); sugarcane silage enriched with calcium oxide at 5 g/kg of forage (SCSc); and sugarcane silage enriched with Lactobacillus buchneri at 5 × 10(4) cfu/kg of forage (SCSb). The roughage to concentrate ratio was 60:40 for the CS diet and 40:60 for the sugarcane-based diets. The dry matter intake (DMI) as a function of body weight had a downward trend for the cows fed sugarcane silage, compared with those fed FS. The sugarcane silages had higher digestibilities of dry matter (DM), organic matter (OM), and neutral detergent fiber (NDFap), compared with FS. The use of L. buchneri or calcium oxide improved the diet's digestibility. The use of FS, sugarcane silage, or sugarcane silage with additives had no effects on milk and fat-corrected milk yield, compared to corn silage. Cows fed FS presented lower milk total solids content and had a downward trend for milk fat, compared with cows fed sugarcane-silage diets. Cows fed sugarcane silages produced milk with higher casein stability in the alcohol test than cows fed fresh-sugarcane diet. Sugarcane silage, with or without additives, did not reduce the intake of dairy cows, and the use of additives improved the fiber's digestibility.

Effect of feeding strategies on weaning weight and milk production of Holstein × Zebu calves in dual purpose milk production systems.

The objective of this study was to evaluate the effect of five feeding strategies on calf weaning weight, and cow milk production and composition in Brazilian Holstein × Zebu cows. A total of 60 cows and their calves were allocated to each of five treatments. Cows in treatments 1, 2 and 3 were milked for 270 days and cows in treatments 4 and 5 were milked for 180 days. Calves in treatment 1 (CON) were not supplemented with concentrate whereas calves from treatment 2 (CLPN) received 1 kg of concentrate daily from 90 to 270 days of age and calves from treatment 3 received 1 kg of concentrated from 180 to 270 days of age. Calves in treatment 4 (CCPS) were supplemented with 1 kg of concentrate from 90 to 180 days of age and calves in treatment 5 (CLPS) were supplemented with 1 kg of concentrate from 90 to 270 days of age. Calves from the CLPS treatment had greater milk and protein intakes (P < 0.05) and greater growth rate than calves from the other treatments. Our results indicate that the traditional system of feeding calves with no concentrate results in a weight gain of 600 g/day. The CLPS treatment produced calves with the highest live weight and growth rate. The nutritional strategy with restricted supply of milk for the calves with concomitantly short-term concentrate supplementation does not improve performance of calves but did increase feed costs.

Meat production in a feedlot system of Zebu-Holstein steers and heifers with dairy genetics: productive and biological analyses.

The aim of this study was to evaluate the productive and biological efficiency of steers and heifers from dairy genetics in a feedlot system in terms of meat production. Twenty-four steers and 24 heifers at 10 monthes of age, (3/4) Zebu × (1/4) Holstein were utilized. They were distributed over four feedlot times, 30, 60, 90, and 120 days with four replications for each sex, and were slaughtered at the end of each period. The productive and biological analyses were performed through comparative slaughter to determine the body composition. Heifers presented with greater intakes (P < 0.05) of dry matter in grams per kg of body weight. Steers presented with a greater (P < 0.05) final empty body weight, carcass gain, cold carcass weight, and meat proportion in the carcass; however, heifers presented with a greater subcutaneous fat thickness (P < 0.05) and, consequently, a greater (P < 0.05) fat proportion in the carcass. We conclude that steers are more efficient in their productive performance than heifers in a feedlot. For the finishing carcass fat cover, heifers need 90 days in the feedlot. The net energy requirements for maintenance are 67 kcal/EBW(0.75)/d, and the net requirements of energy (NEg) and protein (NPg) for gain can be estimated by the following equations: NEg(Mcal/d) = 0.067 × EBW(0.75) × EBG(1.095) and NPg = 162 × EBG - 5.62 × RE for the two sexes.

Predicting ruminal degradability and chemical composition of corn silage using near-infrared spectroscopy and multivariate regression.

The aim of this study was to develop and validate regression models to predict the chemical composition and ruminal degradation parameters of corn silage by near-infrared spectroscopy (NIR). Ninety-four samples were used to develop and validate the models to predict corn silage composition. A subset of 23 samples was used to develop and validate models to predict ruminal degradation parameters of corn silage. Wet chemistry methods were used to determine the composition values and ruminal degradation parameters of the corn silage samples. The dried and ground samples had their NIR spectra scanned using a poliSPECNIR 900-1700 model NIR sprectrophotometer (ITPhotonics S.r.l, Breganze, IT.). The models were developed using regression by partial least squares (PLS), and the ordered predictor selection (OPS) method was used. In general, the regression models obtained to predict the corn silage composition (P>0.05), except the model for organic matter (OM), adequately estimated the studied properties. It was not possible to develop prediction models for the potentially degradable fraction in the rumen of OM and crude protein and the degradation rate of OM. The regression models that could be obtained to predict the ruminal degradation parameters showed correlation coefficient of calibration between 0.530 and 0.985. The regression models developed to predict CS composition accurately estimated the CS composition, except the model for OM. The NIR has potential to be used by nutritionists as a rapid prediction tool for ruminal degradation parameters in the field.

Periparturient Changes in Voluntary Intake, Digestibility, and Performance of Grazing Zebu Beef Cows with or without Protein Supplementation.

We aimed to understand the changes in nutritional parameters and performance of beef cows during the peripartum, whether receiving or not receiving protein supplements. Forty cows were used, divided into two treatments: CON-mineral mix and SUP-protein supplementation. Digestibility trial was performed at 45, 30, and 15 days (d) before the parturition and at 20 and 40 d of lactation. The ADG of cows pre- and postpartum was recorded along with the BCS in gestational (GT) and maternal (MT) tissues in the prepartum. There was an effect of treatment and period (p ≤ 0.044) for intakes of DM and CP. The forage intake was similar (p > 0.90) but varied with the effect of days related to parturition (p < 0.001). There was a 14.37% decrease in DM intake from d -30 to d -15 of prepartum. In the postpartum, at 20 d of lactation, there was an increase of 72.7% in relation to d -15 of prepartum. No differences were observed in postpartum ADG or BCS at parturition and postpartum (p ≥ 0.12). However, higher total and MT ADG (p ≤ 0.02) were observed in animals receiving supplementation, while ADG in GT remained similar (p > 0.14). In conclusion, there is a decrease in intake for pregnant cows close to parturition and greater performance of animals supplemented in prepartum.

Performance, growth, and maturity of Nellore bulls.

The objectives of this study were to evaluate the dry matter intake (DMI), digestibility, average daily gain (ADG), microbial efficiency, empty body weight (EBW) gain, and body composition of Nellore bulls. Additionally, Nellore bull maturity was estimated, and the prediction equation for DMI, suggested by the Brazilian nutrient requirements system (BR CORTE; Azevêdo et al. 2010), was evaluated. Thirty-three Nellore bulls, with a mean initial weight of 259 ± 25 kg and age of 14 ± 1 months, were used in this study. Five animals were slaughtered at the beginning of the experiment (control group), and the remaining 28 were divided into 4 groups, each slaughtered at 42-day intervals. Their diet was composed of corn silage and concentrate (55:45). The power model was used to estimate muscle tissue, bone tissue, crude protein (CP), mineral matter (MM), and water present in the empty body, while the exponential model was used to estimate adipose tissue and ether extract (EE) present in the empty body. When expressed in kilograms per day, differences were observed (P < 0.05) only for the intake of EE and neutral detergent fiber as a function of feedlot time periods. Although there was a difference in relation to nutrient intake, it did not affect (P > 0.05) digestibility, with the exception of EE digestibility. The equation suggested by BR CORTE correctly estimates the DMI of Nellore bulls. ADG was not affected (P > 0.05) by time spent in the feedlot. No differences were observed (P > 0.05) for microbial efficiency; a mean value of 142 g microbial crude protein/kg total digestible nutrients was achieved. The muscle and bone tissues, CP, MM, and water present in the empty body increased as the animal grew, although at a lower rate. The adipose tissue and EE present in the empty body increased their deposition rate when the animal reached its mature weight. Maturity is defined as when an animal reaches 22 % EE in the empty body, which corresponds to 456 kg of EBW in Nellore bulls. Therefore, this study can conclude that the feedlot time period does not affect DMI, nutrient intake, ADG, or microbial efficiency. The equation proposed by BR CORTE (Azevêdo et al. 2010) correctly estimates the DMI of Nellore bulls, which reach maturity when an EBW of 456 kg is attained.

Creatinine recovery from bovine urine under the effect of different times and temperatures of storage.

Creatinine is a urinary marker used widely in ruminant's experimental trials. However, despite its great importance no data were found in the literature about the best way to store bovine urine samples. In the sheep urine, was observed an increase in the urinary concentration of creatinine when it was stored acidified (pH 2.5 to 3.5) at a temperature of 28 to 39 °C for 150 days of storage. Nevertheless, urine should be stored acidified (pH below 3) to avoid purine derivative degradation, So, aimed to evaluate creatinine recovery in bovine urine as a function of storage time and temperature. A total of 25 animals' urine (10 Nellore cattle and 15 Holstein cattle) were collected. The urine (40 mL) was diluted in 160 mL of distilled water and its pH was corrected to a value lower than 3 using sulfuric acid drops. A sample of the diluted urine was analyzed to obtain the creatinine concentration reference value on the collection day. The remaining urine was fractionated and preserved at room temperature, cooled (4 °C) or frozen (-20 °C and -40 °C). In the urine of five Holstein cattle was added creatine solutions (20, 40 and 60 mg/dL) to evaluate the creatine to creatinine conservation. These urine samples were analyzed on different days after collection (1, 3, 7, 15, 30 and 45 days). The urine without any added creatine was analyzed on Days 1, 3, 7, 10, 15, 30, 45, 60, 90, 120, and 150 of storage. The addition of creatine in the urine caused an increase in the creatinine concentration (P < 0.05) after 30 days of storage at room temperature and under refrigeration (4 °C). In frozen samples, there was no change in creatinine concentration (P > 0.05). However, creatinine recovery was constant (P > 0.05) until day 15 of storage, regardless of the temperature used, when creatine was not added. After 30 days of storage, an effect of time and/or temperature was observed on creatinine recovery (P < 0.05). Urine samples can be stored at any temperature for up to 15 days after collection to estimate the creatinine concentration. Samples that need storage times longer than 15 days should be frozen (at -20 °C and -40 °C) to avoid creatinine concentration variation.

Does Parity Influence the Magnitude of the Stress Response of Nellore Cows at Weaning?

Most studies investigate the impact of stress at weaning on calves; however, little is known about the responses of cows, and whether they would differ according to parity. This study aims to investigate whether parity would influence the weaning stress response in beef cows. Thirty pregnant Nellore cows with their respective calves were randomly allocated to five paddocks and two females from each parity group were placed in the paddocks. There was an interaction (p < 0.05) between parity and evaluation days regarding cortisol, where on d + 7, the higher concentration was observed for multiparous cows. There was an interaction (p < 0.05) between parity and evaluation day for red blood cells (RBC), hematocrit (HCT), and hemoglobin (HB), whereby higher RBC counts on d + 4 were observed for multiparous cows. For HCT and HB, on all post-weaning collection days, higher values were observed for multiparous cows. The day of evaluation had an (p < 0.05) effect on all recorded behaviors, except for rumination (p > 0.05). Nellore cows, regardless of parity, underwent behavioral and physiological changes on abrupt weaning. Physiological parameters indicated that the magnitude of stress was greater in multiparous cows.

Strategies of supplementation of female suckling calves and nutrition parameters of beef cows on tropical pasture.

The performance of female calves in creep feeding under different strategies of supplementation and milk production, intake, and digestibility of grazing Nellore and crossbred cows (Nellore × Holstein) during the dry-rainy transition season were assessed. Forty-four female beef suckling calves, with initial age between 90 and 150 days and average initial body weight of 117.7 ± 4.3 kg, and their respective dams (24 Nellore and 20 crossbred) with average initial body weight of 417.5 ± 8.3 kg, were used. The experimental treatments consisted of: control group--mineral mixture only; strategy 1--supplementation from 112 days prior to weaning (0.375 kg/animal/day); strategy 2--supplementation from 112 days prior to weaning, in increasing amounts of 0.15, 0.30, 0.45, and 0.60 kg/animal/day through the four experimental periods, respectively; and strategy 3--supplementation from 56 days prior to weaning (0.750 kg/animal/day). Calves from strategy 1 had greater (P < 0.05) average daily gain (0.672 kg/day) than control animals (0.582 kg/day) and greater (P < 0.05) efficiency of supplement use than the other groups. Crossbred cows produced more milk than Nellore cows (P < 0.05). Crossbred cows presented greater (P < 0.05) dry matter intake (DMI) than Nellore cows. However, no differences were found (P > 0.05) for nutrient digestibility among genetic types. It can be concluded that strategies of supplementation that present an equitable distribution of supplement provides greater weight gain in suckling female beef calves. Crossbred cows produce more milk and present greater DMI than Nellore cows. There are no differences in the nutrient digestibility between Nellore and Nellore × Holstein crossbred cows.

Intake, digestibility, performance, and carcass traits of beef cattle of different gender.

The performance, intake, feed efficiency, and carcass traits of beef cattle from different gender profile were assessed. Fifteen animals (five steers, five spayed heifers, and five intact heifers) with ±250 kg of initial body weight were randomly assigned in individual pens and fed the same diet for 106 days. At the end of the trial, all the animals were slaughtered and the pH, temperature, and weight of the carcass were recorded. The right side of each carcass was then separated into chuck, shoulder, flank sirloin, and round for evaluation of commercial cuts yield. The left carcass sides were ribbed between the 12th and 13th ribs where the rib eye area and fat thickness measurements were taken. The 9th-11th rib section was removed from the left half carcass and then dissected into muscle, fat, and bones in order to estimate carcass composition. Gender had no effect (P > 0.05) on performance, intake, digestibility of dry matter and all the nutrients evaluated, feed efficiency, and carcass characteristics. It can be concluded that steers and heifers (spayed or not) have the same potential to produce beef. From a productive and welfare standpoint, there is no reason to spay heifers.

Performance and meat quality traits of beef heifers fed with two levels of concentrate and ruminally undegradable protein.

The effects of two levels of concentrate and ruminally undegradable protein (RUP) on performance, intake, digestibility, carcass characteristics, meat quality traits, and commercial cuts yield were assessed. Twenty crossbred heifers (240 kg average body weight) were used. At the beginning of the trial, four animals were slaughtered as reference group and the 16 remaining animals were randomly assigned to four treatments, in a 2 × 2 factorial design: two levels of concentrate (40% and 80%, dry matter (DM) basis) and two levels of RUP (48.79% and 27.19% of CP). At the end of the trial, all the animals were slaughtered. There was no interaction (P > 0.05) between concentrate and RUP levels. Dry matter intake and nutrients digestibility was not affected (P > 0.05) by RUP level. Heifers fed the highest RUP level had greater (P < 0.05) average daily gain (ADG). Concentrate level did not affect (P > 0.05) DMI and ADG. Heifers fed diets with 80% concentrate had greater intake of TDN and EE, and lower intake of NDF (P < 0.05). The digestibilities of all nutrients, except the NDF, were greater (P < 0.05) for the 80% concentrate diets. The RUP levels did not affect (P > 0.05) the carcass characteristics and carcass gain composition. Heifers fed 80% concentrate diets had larger (P < 0.05) longissimus muscle area and lower gain of bones (P < 0.05). Concentrate level did not affect (P > 0.05) the composition of carcass gain. There was no effect (P > 0.05) of RUP and concentrate levels on meat quality traits and commercial cut yields.

Evaluation of Non-linear Models to Predict Potential Milk Yield of Beef Cows According to Parity Order Under Grazing.

This study aimed to evaluate the effect of parity order on milk yield (MY) and composition over time of grazing beef cows and to evaluate non-linear models to describe the lactation curve. Thirty-six pregnant Nellore cows (12 nulliparous, 2 years; 12 primiparous, 3 years; and 12 multiparous, 4-6 years) were included in the study. With calving day assigned as day 0, milking was performed using a milking machine to estimate MY on days 7, 14, 21, 42, 63, 91, 119, 154, and 203. Dummy variable analyses were applied to estimate its effects on MY, composition (kg and percentage), afternoon/morning, and afternoon/total proportions. Since multiparous cows had higher MY than nulliparous and primiparous cows, two different groups were used for lactation curve analysis: Mult (multiparous) and Null/Prim (nulliparous and primiparous). The MY estimated by the last edition of BR-Corte (Nutrient Requirements of Zebu and Crossbred Cattle) equation was compared with the observed values from this study. Five nonlinear models proposed by Wood (WD), Jenkins & Ferrell (JF), Wilmink (WK), Henriques (HR) and Cobby & Le Du (CL) were evaluated. Models were validated using an independent dataset of multiparous and primiparous cows. The estimates for parameters a, b, and c of the CL equation were compared between groups, and the BR-Corte equation used the model identity methodology. Nulliparous and primiparous cows displayed similar MY (P > 0.05); however, multiparous cows had an average MY that is 0.70 kg/day greater than that of nulliparous and primiparous cows (P < 0.05). Milk protein and total solids were higher for multiparous cows (P < 0.05). Effect of days in milking was found for milk fat, protein, and total solids (P < 0.05). The yield of all milk components was higher for multiparous cows than for nulliparous and primiparous cows. The afternoon/morning and afternoon/total proportions of milk production were not affected by parities and days in milking (P > 0.05), with an average of 0.76 and 0.42, respectively. The BR-Corte equation did not correctly estimate the MY (P < 0.05). The equations of WD, WK, and CL had the best estimate of MY for both Mult and Null/Prim datasets. The equations had a very similar Akaike's information criterion with correction and mean square error of prediction.

Nutrient requirements and evaluation of equations to predict chemical body composition of dairy crossbred steers.

OBJECTIVE: Objectives were to estimate energy and protein requirements of dairy crossbred steers, as well as to evaluate equations previously described in the literature (HH46 and CS16) to predict the carcass and empty body chemical composition of crossbred dairy cattle. METHODS: Thirty-three Holstein × Zebu steers, aged 19 ± 1 months old, with an initial shrunk body weight of 324 ± 7.7 kg, were randomly divided into three groups: reference group (n = 5), maintenance level (1.17% BW; n = 4), and the remaining 24 steers were randomly allocated to 1 of 4 treatments. Treatments were: intake restricted to 85% of ad libitum feed intake for either 0, 28, 42, or 84 d of an 84-d finishing period. RESULTS: The net energy and the metabolizable protein requirements for maintenance were 0.083 Mcal/EBW0.75/d and 4.40 g/EBW0.75, respectively. The net energy (NEG) and protein (NPG) requirements for growth can be estimated with the following equations: NEG (Mcal/kg EBG) = 0.2973(± 0.1212) × EBW0.4336(± 0.1002) and NPG (g/d) = 183.6(± 22.5333) × EBG - 2.0693(± 4.7254) × RE, where EBW = empty body weight, EBG = empty body gain, and RE = retained energy. Crude protein (CP) and ether extract (EE) chemical contents in carcass, and all the chemical components in the empty body were precisely and accurately estimated by CS16 equations. However, water content in carcass was better predicted by HH46 equation. CONCLUSION: The equations proposed in this study can be used for estimating the energy and protein requirements of crossbred dairy steers. The CS16 equations were the best estimator for CP and EE chemical contents in carcass, and all chemical components in the empty body of crossbred dairy steers, whereas water in carcass was better estimated using the HH46 equations.

Feed intake, nutrient digestibility, and selected rumen parameters in feedlot bulls fed diets with different feed additives.

An experiment was conducted to evaluate the feed intake, nutrient digestibility and selected rumen parameters in feedlot bulls fed diets containing different feed additives. Six rumen-cannulated Nellore bulls (age = 8 ± 1.0 months; initial BW = 225 ± 13.2 kg) were distributed in a 6 × 6 Latin square design. Six experimental diets based on 30% corn silage and 70% concentrate on a dry matter (DM) basis were evaluated. Diets differed in feed additive on a DM basis, as follows: 1.4% bicarbonate and magnesium oxide in 3:1 ratio (BOX); 36 ppm lasalocid sodium (LAS); 30 ppm monensin sodium (MON); 25 ppm virginiamycin (VIR); 30 ppm monensin sodium plus 25 ppm virginiamycin (MV); and 3.15% commercial mineral supplement containing D-limonene and exogenous α-amylase (EOA). The experiment lasted 144 d, with six periods of 24 d. Each period consisted of 14 d for dietary adaptation, 3 d for feces and urine collection, and 7 d for omasal and ruminal digesta collection. Bulls fed the BOX diet showed greater (P < 0.05) intake of DM, organic matter (OM), neutral detergent fiber (apNDF), crude protein (CP), and starch compared to the other diets. Diets with LAS, MON, VIR, MV, or EOA did not influence (P > 0.05) the DM, OM, apNDF, CP, or starch intake of feedlot bulls. Bulls fed the EOA diet showed greater (trend; P = 0.09) ruminal digestibility of starch compared to the other diets. The feed additives did not affect (P > 0.05) the intestinal or total tract digestibility of starch, rumen pH, microbial efficiency, total rumen fluid, dilution rate, rate of intake, rate of degradation, or passage rate of the DM, OM, apNDF, and starch. In conclusion, LAS, MON, VIR, MV, and EOA diets reduced nutrient intake compared to BOX. Although all feed additives presented similar effects on rumen pH, temperature, and kinetics the presence of exogenous α-amylase in the EOA diet may increase ruminal starch digestibility and apparent total tract digestibility of DM and OM.

Metabolizable Protein: 1. Predicting Equations to Estimate Microbial Crude Protein Synthesis in Small Ruminants.

Microbial crude protein (MCP) produced in rumen could be estimated by a variety of protocols of experimental sampling and analysis. However, a model to estimate this value is necessary when protein requirements are calculated for small ruminants. This model could be useful to calculate rumen degradable protein (RDP) requirements from metabolizable protein (MP). Then, our objective was to investigate if there is a difference in MCP efficiency between sheep and goats, and to fit equations to predict ruminal MCP production from dietary energy intake. The database consisted of 19 studies with goats (n = 176) and sheep (n = 316), and the variables MCP synthesis (g/day), total digestible nutrients (TDN), and organic matter (OM) intakes (g/day), and OM digestibility (g/kg DM) were registered for both species. The database was used for two different purposes, where 70% of the values were sorted to fit equations, and 30% for validation. A meta-analytical procedure was carried out using the MIXED procedure of SAS, specie was considered as the fixed dummy effect, and the intercept and slope nested in the study were considered random effects. No effect of specie was observed for the estimation of MCP from TDN, digestible Organic Matter (dOM), or metabolizable energy (ME) intakes (P > 0.05), considering an equation with or without an intercept. Therefore, single models including both species at the same fitting were validated. The following equations MCP (g/day) = 12.7311 + 59.2956 × TDN intake (AIC = 3,004.6); MCP (g/day) = 15.7764 + 62.2612 × dOM intake (AIC = 2,755.1); and MCP (g/day) = 12.7311 + 15.3000 × ME intake (AIC = 3,007.3) presented lower values for the mean square error of prediction (MSEP) and its decomposition, and similar values for the concordance correlation coefficient (CCC) and for the residual mean square error (RMSE) when compared with equations fitted without an intercept. The intercept and slope pooled test was significant for equations without an intercept (P < 0.05), indicating that observed and predicted data differed. In contrast, predicted and observed data for complete equations were similar (P > 0.05).

Energy requirements for pregnant dairy cows.

This study aimed to estimate energy requirements of pregnant Holstein × Gyr cows. Different planes of nutrition were established by two feeding regimens: ad libitum or maintenance. Sixty-two nonlactating cows with average body weight of 480 ± 10.1 kg and an age of 5 ± 0.5 years were used. Cows were divided into three groups: pregnant (n = 44), non-pregnant (n = 12), and baseline reference (n = 6). The 56 pregnant and non-pregnant cows were randomly allocated into a feeding regimen: ad libitum or maintenance. To evaluate the effects of days of pregnancy, pregnant and non-pregnant animals were slaughtered at 140, 200, 240, and 270 days of pregnancy. Energy requirements for maintenance differed between pregnant and non-pregnant cows, thus two equations were developed. Net energy and metabolizable energy requirements for maintenance of non-pregnant cows were 82 kcal/kg empty body weight0.75/day and 132 kcal/kg empty body weight0.75/day, respectively. The efficiency of use of metabolizable energy for maintenance of non-pregnant cows was 62.4%. Net energy and metabolizable energy for maintenance of pregnant cows were 86 kcal/kg empty body weight0.75/day and 137 kcal/kg empty body weight0.75/day, respectively. Efficiency of use of metabolizable energy for maintenance of pregnant cows was 62.5%. The efficiency of use of metabolizable energy for gain was 41.9%. The efficiency of use of metabolizable energy for pregnancy was 14.1%. Furthermore, net energy requirement for pregnancy was different from zero from day 70 of pregnancy onwards. In conclusion, net energy and metabolizable energy requirements for maintenance of non-pregnant cows are different from pregnant cows. Furthermore, we believe that the proposed non-linear equations to estimate net energy requirements for pregnancy are more adequate than current NRC equation, and should be recommended for Holstein × Gyr cows.

Reconstituted and ensiled corn or sorghum grain: Impacts on dietary nitrogen fractions, intake, and digestion sites in young Nellore bulls.

Two experiments were conducted: (1) to evaluate the effect of ensiling time and grain source on dietary nitrogen fractions; and (2) to verify the influence of concentrate level, processing method and grain source on intake, microbial efficiency, and digestibility by young Nellore bulls. In Experiment 1, corn and sorghum grains were milled, reconstituted to 35% moisture, and ensiled in a bag silo for 10 different times. There were three replications per ensiling time and grain source. Samples from each replication were analyzed in triplicate for total nitrogen (N), non-protein nitrogen (NPN), soluble N, insoluble N, and neutral detergent insoluble nitrogen (NDIN). In Experiment 2, five Nellore bulls were used in a 5 × 5 Latin square design. Four diets were comprised of 28.4% corn silage, 10.7% supplement, and 60.9% dry ground corn, dry ground sorghum, reconstituted and ensiled corn, or reconstituted and ensiled ground sorghum. An additional diet comprised of 45% corn silage, 10.7% supplement, and 44.3% dry ground corn (Roughage+) was used. Each experimental period lasted 22 days, with an adaptation period of 14 days followed by 5 days of total feces and urine collection and 3 days of collecting omasal samples. Data were analyzed using the MIXED procedure of SAS 9.4. The reconstitution and ensiling process reduced (P < 0.05) the insoluble N fraction, increased (P < 0.05) non-protein nitrogen of corn and sorghum grains, tended (P = 0.052) to increase microbial efficiency, and increased (P < 0.05) intestinal and total digestion of dry matter (DM), organic matter (OM), crude protein (CP), and starch. The concentrate level affected neither (P > 0.05) DM intake nor rumen pH. On the other hand, bulls fed diets based on 72% concentrate showed greater (P < 0.05) DM, OM, and CP digestibility compared with those fed a diet based on 55% concentrate. In addition, animals fed diets based on corn grains (both reconstituted and ensiled or dry) presented greater (P < 0.05) intestinal and total starch digestion compared to those fed sorghum grain. Therefore, the reconstitution process can reduce the insoluble N fraction and increase nutrient availability.

A suitable enzymatic method for starch quantification in different organic matrices.

Starch can represent 70-80% of the cereals grains (on a dry matter basis) used for livestock feeding. Several methods have been developed to estimate the feed starch contents of energy feed sources. However, the efficiency of these methods to evaluate the starch content in other feed sources, as well as other types of samples used to evaluate starch availability in the gastrointestinal tract, such as digesta and faeces, remains unclear. Furthermore, most of the currently used starch analysis methods have not been effectively evaluated, being only applied to samples of sporadic experiments, without a wide-ranging validation of the procedures and results. Here, we propose a modification of a method for analysing the starch content in different organic matrices normally evaluated in ruminant nutrition studies. The evaluated organic matrices were: soybean meal, soybean hull, Tifton 85 Bermuda grass hay, abomasal digesta, and faeces. •The modified method is more feasible than the original procedures.•The modified method estimates the starch contents in different organic matrices with accuracy and precision.