Is bovine somatotropin an alternative strategy to overcome the detrimental effects of high-gain diets on prepubertal Holstein × Gyr heifers?

Feeding high-gain diets and an inadequate energy and protein ratio during pre-puberty may lead to impaired growth and mammary gland development of heifers. Thus, frequent application of bovine somatotropin (bST) may prevent future losses in productivity, improve mammary development and animal performance. We aimed to evaluate the effects of bST on digestibility, performance, blood metabolites, mammary gland development, and carcass composition of high-performance prepubertal Holstein × Gyr heifers. Thirty-four Holstein × Gyr heifers with an average initial body weight of 218 ± 49 kg and 14 ± 4 months of age were submitted to an 84-day trial evaluating the effects of no bST or bST injections. Treatments were randomly assigned to each animal within one of the tree blocks. The bST did not influence digestibility or performance parameters. Regarding blood results, IGF1 concentration presented an interaction between treatment and day, where bST heifers had the highest IGF1 concentration. Heifers receiving bST also showed increased ribeye area; however, only an experimental day effect for backfat thickness was observed, with greater accumulation of carcass fat on day 84. Heifers receiving bST had lower pixels/mm² on parenchyma, characteristic of greater parenchymal tissue. Moreover, heifers on bST treatment also had reduced pixels/mm2, characteristic of reduced fat pad tissue. Lastly, bST injections did not influence liver and muscle gene expression, nor most genes evaluated in mammary gland tissue, except for IGFBP3 expression, which was greater for bST heifers. In summary, we confirm the efficacy of bST injections to overcome the detrimental effects of high-gain diets on mammary gland growth and to improve lean carcass gain of prepubertal Holstein × Gyr heifers.

Comparison of ruminal microbiota, IL-1ß gene variation, and tick incidence between Holstein × Gyr and Holstein heifers in grazing system.

Introduction: The variation in bacterial communities among breeds has been previously reported and may be one of the reasons why Holstein × Gyr dairy heifers have better development in grazing systems in tropical conditions. This study aimed to explore the ruminal microbiota composition, the IL-1ß gene variation, tick incidence, and blood parameters of Holstein × Gyr (½ Holstein × ½ Gyr) and Holstein heifers grazing intensely managed Guinea grass (Panicum maximum Jacq. cv. Mombaça). Methods: Sixteen heifers were divided into two groups consisting of 8 Holstein × Gyr and 8 Holstein heifers. The experimental period was comprised of 3 periods of 21 days. Ruminal samples were taken via the stomach tube technique. The sequencing of the V4 hypervariable region of the 16S rRNA gene was performed using the Illumina MiSeq platform. Counting and collection of ticks were conducted each 21 days. Blood and skeletal muscle tissue biopsies were performed at the end of the experiment. Results: Firmicutes were the most abundant phyla present in both breed rumen samples and Bacteroidota showed differences in relative abundance between breed groups, with greater values for Holstein heifers (p < 0.05 with FDR correction). The 10 most abundant unique OTUs identified in each breed included several OTUs of the genus Prevotella. Holstein heifers had a greater tick count and weight (9.8 ticks/animal and 1.6 g/animal, respectively) than Holstein × Gyr (2.56 ticks/animal and 0.4 g/animal, respectively). We found nucleotide substitutions in the IL-1ß gene that might be related to adaptation and resistance phenotypes to tick infestation in Holstein × Gyr heifers. Blood concentrations of urea, albumin, insulin-like growth factor 1, triiodothyronine, and thyroxine were greater in Holstein × Gyr than in Holstein heifers. Conclusion: Adaptations in Holstein × Gyr heifers such as ruminal microbiota, tick resistance, nucleotide substitutions in IL-1ß gene, and hormone concentration suggest a better energy metabolism and thermoregulation resulting in better performance in tropical grazing systems.

Peach palm shells (Bactris gasipaes Kunth) bioconversion by Lentinula edodes: Potential as new bioproducts for beef cattle feeding.

This paper aims to develop and assess the in vitro effects on ruminal fermentation and greenhouse gas parameters of new bioproducts for beef cattle diets, carried out by solid-state fermentation of peach palm shells colonized by Lentinula edodes (SSF) and after Shiitake mushroom cultivation in axenic blocks (SMS). In vitro experiments were performed to assess the in vitro gas production, digestibility, and fiber degradation of formulated total diets. Bioproducts presented high ß-glucans (9.44---11.27 %) and protein (10.04---8.35 %) contents, as well as similar digestibility to conventional diets. SMS diet had the lowest methane and carbon dioxide (19.1 and 84.1 mM/g OM) production, and the SSF diet presented lower carbon dioxide production (98.9 mM/g OM) than other diets, whereas methane was similar. This study highlighted a sustainable use of byproducts for beef cattle diets, promising for digestibility, nutritional value, ß-glucans incorporation, and environmental impact mitigation, favoring the circular bioeconomy.

Metabolic responses and performance of Holstein × Gyr heifers grazing Brachiaria decumbens supplemented with varied crude protein levels.

We aimed to evaluate the effect of supplemental CP on the nutritional characteristics and performance of Holstein × Gyr crossbreed heifers grazing intensively-managed Brachiaria decumbens throughout the year. Thirty-eight heifers with average initial body weight of 172.5 ± 11.15 kg (mean ± SE) and 8.2 ± 0.54 mo of age were randomly assigned to four treatments: three protein supplements (SUP) composed of soybean meal and ground corn fed at 5g/kg of BW, plus a control group (CON). The supplements had 12, 24 and 36% of CP for treatments S12 (n = 9), S24 (n = 10), and S36 (n = 9), respectively. The experiment latest one year, subdivided into four seasons: rainy, dry, rainy-dry transition (RDT), and dry-rainy transition (DRT). Feces and pasture samples were collected for 4 days in each season, using chromium oxide, titanium dioxide, and indigestible neutral detergent fiber (NDF) to estimate fecal excretion, supplement, and pasture intake, respectively. The data were analyzed using PROC GLIMMIXED of the SAS with repeated measures. No effects of supplementation were detected on pasture and NDF intake. However, SUP animals had a greater intake of DM, metabolizable energy, and metabolizable protein. A positive linear response on metabolizable protein intake was observed among SUP animals. We observed an interaction between treatment and season for all digestibility variables, with a positive linear response in CP digestibility among SUP animals during all seasons. For neutral detergent fiber (NDF) digestibility, we observed a positive linear response in RDT and rainy seasons and a quadratic response during the dry season. Furthermore, SUP animals had greater average daily gain (ADG) than non-supplemented animals, and among SUP animals, there was a quadratic response to ADG, with the greatest gain observed in S24. We observed greater nitrogen retention coefficient in SUP animals than in non-supplemented animals and a positive linear effect among SUP animals. Supplemental CP did not affect microbial protein production and efficiency. We observed an interaction between treatment and season for blood glucose, with SUP animals having greater glucose concentration in all seasons than non-supplemented animals. Additionally, we observed a quadratic response among SUP animals only during RDT and dry season, with the greatest glucose concentration in S24. SUP animals had greater blood concentrations of urea and IGF-1. In conclusion, SUP animals had greater intake, digestibility, and performance than non-supplemented animals, with the 24% CP supplement demonstrating the best metabolic responses and performance.

Protein requirements of hair sheep raised in warm areas: a multi-study approach.

The protein requirements of hair sheep are a key factor in increasing profitability and decreasing the environmental impacts of nitrogen excretion. The objective of this study was to evaluate the protein requirements of hair sheep. A database with 382 individual records (269 intact and 113 castrated males) comprising information from 11 studies was used. The studies provided different levels of metabolisable protein intake (MPI) and of N retention, allowing the development of equations to predict the net protein (NP) and the metabolisable protein (MP) requirements. The efficiency of MP use for gain (kpg) was calculated using the equation of daily protein retained against daily MPI above maintenance. The efficiency of MP use for maintenance (kpm) was computed as the ratio between the NP for maintenance (NPm) and the MP for maintenance (MPm). The NPm (1.32 g/kg0.75 EBW) did not differ between sex. The kpm was 0.34, and the kpg was 0.25. The MPm estimated was 3.21 g/kg0.75 BW. Sex affects the protein requirements for gain (NPg). The protein requirements of hair sheep differ from those recommended by feeding systems for sheep. The equations provided herein may improve the optimisation of protein nutrition of sheep, thereby minimising the environmental impacts of sheep production.

Macromineral and trace element requirements for Santa Ines sheep.

Minerals play an important role in animal metabolism. Knowledge of mineral requirements allows well-formulated diets to be provided, which is the main factor that affects performance. To determine the macromineral and trace element requirements for growth and maintenance, thirty-eight 2-month-old Santa Ines lambs with initial body weight (BW) of 13.0 ± 1.49 kg were distributed in a factorial design with feeding levels (ad libitum, 30% and 60% feed restriction) and sex classes [castrated (CM) and intact males (IM)]. The net mineral requirements for gain were higher (P < 0.05) with increasing BW and average daily gain, except for Ca and Na, which remained constant as the empty BW (EBW) increased. The macromineral net requirement for maintenance (g/kg EBW0.75) and the true retention coefficient (k; %) were 0.0784 and 65.2 for Ca, 0.0926 and 80.0 for P, and 0.0379 and 59.0 for K, respectively. The k of Mg was higher (P < 0.05) for IM (11.3 for IM and 7.9 for CM). Sex did not affect (P > 0.05) the maintenance requirement of the trace elements Co, Cu, Zn and Cr which were 0.0015, 0.037, 0.698, and 0.0055 (mg/kg EBW0.75), respectively. Our study indicated that the Santa Ines net mineral requirements are different from the main nutritional requirements established by committees for sheep, which may result in unbalanced diets.

'Meta-analysis of dry matter intake and neutral detergent fiber intake of hair sheep raised in tropical areas'.

Inadequate estimates of fiber and dry matter intake of sheep raised in tropical conditions may explain part of the inefficiency of those production systems. Therefore, we aimed to estimate dry matter intake (DMI) and neutral detergent fiber intake (NDFI) of hair sheep raised under tropical conditions. A meta-analysis of 61 independent performance experiments, comprising a total of 413 experimental units (treatment means or animals), was performed. Trials were conducted in tropical conditions, using hair sheep in growing and finishing phases and endowed with the following information: neutral detergent fiber (NDF) in diet, initial and final body weight (BW), average daily gain (ADG), DMI and NDFI of treatment means (51 studies) or individual data (10 studies). Data on organic matter and NDF digestibilities were collected to estimate D-value (Dv) and B-value (Bv) (20 and 33 studies, respectively). The equations obtained were: [Formula: see text] DMI (g/kg BW) as a function of Dv (g/kg DM) revealed a quadratic relationship, whose point of maximum DMI (38.69 g/kg BW) was obtained at 634.1 g/kg DM Dv. On the other hand, DMI decreased linearly as Bv (g/kg DM) increased. In conclusion, equations to predict DMI from BW and ADG as well to predict NDFI from dietary NDF were fitted with great accuracy and are recommended for hair sheep raised in tropical regions. DMI values were, in general, greater than those reported by the NRC, AFRC and INRA systems, which may be a reflection of the sheep breeds used in this study. Using Dv and Bv concepts was satisfactory to describe an integrated mechanism between metabolic and bulking regulation of DMI in sheep.

Effect of protein supplement level on the productive and reproductive parameters of replacement heifers managed in intensive grazing systems.

Evaluations of replacement heifers in intensively managed grazing systems in tropical conditions are warranted. Thus, we aimed to evaluate performance, muscle and mammary gland development, oocyte quality, and in vitro production of embryos of crossbred heifers grazing an intensively managed pasture and supplemented with high or low protein concentrates. Eighteen pubertal crossbred heifers (Holstein x Gyr) with an initial weight of 350 ± 8.0 kg were used in a 60-day trial. Two supplement types, 12% crude protein (CP) (S12CP) or 24% CP (S24CP), and a control treatment (mineral mixture, CON) were randomly distributed to the heifers. Throughout the experiment, four digestibility trials were performed over four consecutive days. Four ovarium pick-ups were performed to evaluate oocyte quality and in vitro embryo production. Lastly, ultrasounds of carcasses and mammary glands were performed. The intakes of dry matter (DM), digestible energy (DE), and CP were greater for supplemented (SUP) compared with CON heifers. The SUP heifers had a greater average daily gain (ADG) (645 versus 390 g/d) and rib eye area (58.78 versus 53.32 cm2) than the CON heifers. Oocyte recovery, quality, and follicle features were not affected by supplementation strategy. However, the cleavage rate (47.17% versus 30.31%) and blastocyst rate (27.91% versus 10.12%) were negatively affected by supplementation. The S12CP presented a blastocyst rate much lower than the S24CP (3.02% versus 17.23%). Carcass ultrasonography indicated a trend for greater rib eye area for S24CP and mammary ultrasonography indicated no effects of supplementation on mammary gland development. In summary, supplementation seems to be an appropriate strategy for satisfactory performance, with greater muscle deposition and no negative impacts on mammary gland development. However, in vitro embryo production was impaired when the animals received the supplementation with 12% CP.

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.

Milk microbial composition of Brazilian dairy cows entering the dry period and genomic comparison between Staphylococcus aureus strains susceptible to the bacteriophage vB_SauM-UFV_DC4.

Brazil has the second-largest dairy cattle herd in the world, and bovine mastitis still can cause significant losses for dairy farmers. Despite this fact, little information is available about milk microbial composition of Brazilian dairy cows, as well as the potential use of bacteriophages in the control of S. aureus. Here, we investigated milk bacterial composition of 28 Holstein Fresian cows (109 teats), selected in the dry-off period, using 16S rRNA analysis. Furthermore, a representative S. aureus strain (UFV2030RH1) was obtained at drying-off for isolation of a bacteriophage (vB_SauM-UFV_DC4, UFV_DC4) and bacterial genomic comparison purposes. Our outcomes revealed that Staphylococcus was the third most prevalent genus and positively correlated with subclinical mastitis events. As a major finding, genomic analyses showed the presence of adhesive matrix molecules that recognize microbial surface components (MSCRAMM) in UFV2030RH1 and might indicate great biofilm formation capability. A minimum inhibitory concentration (MIC) assay showed that resistance to ampicillin was the highest among the antibiotic tested in S. aureus 3059 and UFV2030RH1, displaying values four and sixteen times greater than MIC resistance breakpoint, respectively. Together, our results suggest that Staphylococcus is highly prevalent in dairy cows at drying-off and the use of the phage UFV_DC4 as a biocontrol agent must be investigated in future studies.

Nutritional planning for Nellore heifers post-weaning to conception at 15 months of age: performance and nutritional, metabolic, and reproductive responses.

The objective of this study was to evaluate the effects of strategic supplementation in the dry period and dry/rainy transition period on the performance and nutritional, metabolic, and reproductive responses of Nellore heifers grazing Urochloa decumbens. Forty-eight Nellore heifers with age and body weight (BW) of eight months and 235 ± 3.3 kg, respectively, were used. The experimental design was a completely randomized design, with four treatments, all with 12 replications. The evaluated strategies were as follows: low supplementation (LOHI; 0.2% of BW/heifer/day) in the first 90 days and high supplementation (0.6% of BW/heifer/day) in the 90 days thereafter; average supplementation (AVER) with 0.4% of BW/heifer/day for 180 days; high supplementation (HILO; 0.6% of BW/heifer/day) in the first 90 days and low supplementation (0.2% of BW/heifer/day) in the 90 days thereafter; only mineral mix (MM) ad libitum during the 180 days. Data were evaluated using orthogonal contrasts. Supplementation improved the performance of the animals during of dry period (P < 0.05) and dry/rainy transition period (P < 0.05). Supplemented animals had higher longissimus muscle area (LMA) and subcutaneous fat thickness (SFT) at the end of the experiment (P < 0.05). Multiple supplementation increased intake of dry matter (DM), organic matter (OM), and crude protein (CP) in kg/day throughout the experiment. The supplementation increased the digestibility of DM, OM, CP, apNDF, and TDN (P < 0.05). Serum urea nitrogen (SUN), glucose (GLUC), insulin (INS), and progesterone (PROG) were higher in supplemented heifers (P < 0.05). Supplementation reduced the concentrations of non-esterified fatty acids (NEFA) (P < 0.05) and increased conception rate (P < 0.05). In summary, the supplementation strategies adopted in this study improve the performance, metabolic status, and carcass traits of heifers under grazing, allowing an improvement in the conception rate of 15-month-old Nellore heifers.

Effects of grain processing methods on the expression of genes involved in volatile fatty acid transport and pH regulation, and keratinization in rumen epithelium of beef cattle.

Two experiments were carried out to evaluate the effects of corn and sorghum with different processing methods on the expression of genes involved in volatile fatty acids transport and pH regulation, and ruminal keratinization in rumen epithelium of finishing bulls. For Exp. 1, five rumen cannulated Nellore bulls were used in a 5x5 Latin square arrangement, with 14 d for adaptation and 9 d for sample collection. Treatments were: dry ground corn, dry ground sorghum, reconstituted corn, reconstituted sorghum, and control (forage-based diet). Samples of rumen epithelium from ventral sac were excised, rinsed, snap-frozen and stored at -80°C until total RNA isolation and quantitative real-time PCR analysis. In the Exp. 2, 24 Nellore bulls were assigned to a completely randomized design lasting 168 d. Experimental treatments were similar to those at Exp. 1, but without the control treatment. After the experimental period, bulls were slaughtered and rumen epithelium samples were rapidly excised for further histological analysis. Rumen epithelial tissue from animals fed reconstituted corn had lower expression of downregulated-in-adenoma (P = 0.03) and Na+/H+ exchanger 2 (trend; P = 0.09). The expression of Na+/ H+ exchanger 1 (P = 0.10) and putative anion transporter (P = 0.06) tended to be lower in rumen epithelium of bulls fed reconstituted grains. Ruminal concentration of valerate was greater for animals fed reconstituted grain (P = 0.01). Likewise, animals fed reconstituted corn tended to have greater butyrate ruminal concentration (P = 0.08). Keratinized layer thickness did not differ among treatments (P > 0.10). Therefore, reconstituted grains (especially corn) decrease the mRNA expression of genes involved in volatile fatty acids transport and pH control in the rumen epithelium.

Soybean grain is a suitable replacement with soybean meal in multiple supplements for Nellore heifers grazing tropical pastures.

The research aimed to evaluate the effect of replacing soybean meal with soybean grain on the nutritional parameters and productivity of heifers grazing on Urochloa decumbens in the rainy-dry transition period. Forty crossbred heifers with the initial age and weight of 18 months and 292 ± 6.1 kg, respectively, were used. The experimental design was a completely randomized design, with five treatments and eight replications. The evaluated treatments were as follows: SM0.5-supply of 0.5 kg/animal/day of soybean meal supplement; SG0.5-supply of 0.5 kg/animal/day of soybean grain supplement; SM1.0-supply of 1.0 kg/animal/day of soybean meal supplement; SG1.0-supply of 1.0 kg/animal/day of soybean grain supplement; MM-only mineral mix ad libitum. The supplement was isoprotein with 350 g of crude protein/kg of dry matter. Supplementation improved the performance of the heifers and this fact can be verified by the higher average daily gain (ADG) and final BW (fBW) of the supplemented animals (P < 0.10). The two supplemented treatments with 1 kg/day demonstrated similar performance (P > 0.10), the same happens for the two treatments receiving 0.5 kg/day (P > 0.10). However, animals receiving 1 kg/day of supplementation had an ADG and final BW higher than animals receiving 0.5 kg/day (P < 0.10). Supplementation (P < 0.10) affected the intake of dry matter (DM), organic matter, crude protein, ether extract, non-fiber carbohydrates, total digestible nutrients, and neutral detergent fiber corrected for ash and protein (apNDF). Supplementation improved DM digestibility and all constituents of the diet (P < 0.10), except for apNDF (P > 0.10). In summary, it is concluded that multiple supplementations improve the performance of grazing heifers in the rainy-dry transition period and the total replacement of soybean meal by soybean grain does not alter the performance of the animals.

Does partial replacement of corn with glycerin in beef cattle diets affect in vitro ruminal fermentation, gas production kinetic, and enteric greenhouse gas emissions?

Five in vitro experiments were conducted with the following objectives: 1) To evaluate the ruminal fermentation of three different single ingredients: corn, glycerin, and starch (Exp. 1 and 2); 2) To assess effects of partially replacing corn with glycerin in beef cattle diets on ruminal fermentation pattern (Exp. 3 and 4); and 3) To evaluate the effects of glycerin inclusion on the extension of ruminal DM digestibility of feeds with high (orchard hay) and low (corn) fiber content (Exp. 5). For Exp. 1 and 2, two in vitro systems (24-bottle AnkomRF and 20-serum bottles) were used in four consecutive fermentation batches to evaluate gas production (GP), fermentation profiles, enteric methane (CH4), and carbon dioxide (CO2) of corn, glycerin, and starch. The 24 h total GP, acetate concentration, and acetate: propionate ratio decreased only when glycerin was added to the diet (P < 0.01). The 48-h total GP and metabolizable energy were greatest for corn (P < 0.01), and similar between glycerin and starch. The starch treatment had the lowest total volatile fatty acids concentration (P = 0.01). Glycerin had greatest CH4 production, lag time, and maximum gas volume of the first pool (P < 0.05). However, the maximum gas volume of the second pool was greatest for corn (P < 0.05), and similar between glycerin and starch. The starch treatment had the greatest specific rates of digestion for first and second pools (P < 0.05). Production of CO2 (mL/g) was greater for corn (P < 0.01), but similar for glycerin and starch. For Exp. 3 and 4, the same systems were used to evaluate four different levels of glycerin [0, 100, 200, and 300 g/kg of dry matter (DM)] replacing corn in beef cattle finishing diets. Glycerin levels did not affect 24 and 48 h total GP, CH4, and CO2 (P > 0.05). The inclusion of glycerin linearly decreased acetate concentration (P = 0.03) and acetate: propionate ratio (P = 0.04). For Exp. 5, two DaisyII incubators were used to evaluate the in vitro dry matter digestibility (IVDMD) of the following treatments: orchard hay; corn; orchard hay + glycerin; and corn + glycerin. Glycerin inclusion decreased orchard hay IVDMD (P < 0.01) but did not affect corn IVDMD (P > 0.05). We concluded that, under these experimental conditions, glycerin has similar energy efficiency when used in replacement of corn and included at up to 300 g/kg in beef cattle diets.

Supplementation strategies for Nellore female calves in creep feeding to improve the performance: nutritional and metabolic responses.

The objective of this study was to evaluate the effects of supplementation strategy on performance, nutritional and metabolic characteristics of Nellore suckling female calves, on grazing Urochloa decumbens during the rainy-dry transition period. Forty-four Nellore female calves, averaging 147.6 ± 1.34 kg (4 months), were used. A single supplement 20% of crude protein of dry matter was provided, consisting of daily supplement at 0.0, 0.2, 0.4, or 0.6% of body weight. A positive linear effect (P < 0.05) on final body weight and average weight gain of female calves was observed with increased supplementation. Supplementation increased consumption, in kilograms per day, of dry matter (DM), organic matter (OM), crude protein (CP), digested dry matter, and total digestible nutrients (TDN), all calculated as % of dry matter. There was no effect of supplementation on the consumption in kilograms per day of neutral detergent fiber corrected for ash and protein (apNDF) (P > 0.05). Supplementation increased, in a quadratic way, the total apparent digestibility coefficient of DM, OM, CP, apNDF, and TDN (P < 0.05). There was no effect of supplementation (P > 0.05) on non-esterified fatty acid concentrations. There was a positive linear effect (P < 0.05) of supplementation on insulin concentrations. In this study, it is concluded that linearly increasing the feeding level of a supplement with 20% crude protein (% of DM) in the range of 0.2-0.6% of body weight improves the performance, nutritional and metabolic characteristics of the animals, considering these pasture characteristics.

Estimation of daily milk yield of Nellore cows grazing tropical pastures.

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.

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.

Dietary protein reduction on microbial protein, amino acids digestibility, and body retention in beef cattle. I. Digestibility sites and ruminal synthesis estimated by purine bases and 15N as markers.

The objectives of this study were to evaluate the effect of reducing dietary CP contents on 1) total and partial nutrient digestion and nitrogen balance and 2) on microbial crude protein (MCP) synthesis and true MCP digestibility in the small intestine obtained with 15N and purine bases (PB) in beef cattle. Eight bulls (4 Nellore and 4 Crossbred Angus × Nellore) cannulated in the rumen and ileum were distributed in duplicated 4 × 4 Latin squares. The diets consisted of increasing CP contents: 100, 120, or 140 g CP/kg DM offered ad libitum, and restricted intake (RI) diet with 120 g CP/kg DM. The experiment lasted four 17-d periods, with 10 d for adaptation to diets and another 7 for data collection. Omasal digesta flow was obtained using Co-EDTA and indigestible NDF (iNDF) as markers, and to estimate ileal digesta flow only iNDF was used. From days 11 to 17 of each experimental period, ruminal infusions of Co-EDTA (5.0 g/d) and 15N (7.03 g of ammonium sulfate enriched with 10% of 15N atoms) were performed. There was no effect of CP contents (linear effect, P = 0.55 and quadratic effect, P = 0.11) on ruminal OM digestibility. Intake of CP linearly increased (P < 0.01) with greater dietary CP. The NH3-N (P < 0.01) and urinary N excretion (P < 0.01) increased in response to dietary CP, whereas retained N increased linearly (P = 0.03). Liquid-associated bacteria (LAB) in the omasum had greater N content (P < 0.05) in relation to the particle-associated bacteria (PAB). There was no difference between LAB and PAB (P = 0.12) for 15N:14N ratio. The 15N:14N ratio was greater (P < 0.01) in RI animals in relation to those fed at voluntary intake. Microbial CP had a quadratic tendency (P = 0.09) in response to CP increase. Microbial efficiency (expressed in relation to apparent ruminally degradable OM and true ruminally degradable OM) had a quadratic tendency (P = 0.07 and P = 0.08, respectively) to CP increasing and was numerically greatest at 120 g CP/kg DM. The adjusted equations for estimating true intestinal digestibility of MCP (Y1) and total CP (Y2) were, respectively, as follows: Y1 =--16.724(SEM = 40.06) + 0.86X(SEM = 0.05) and Y2 = -43.81(SEM = 49.19) + 0.75X(SEM = 0.05). It was concluded that diets with 120 g/kg of CP optimize the microbial synthesis and efficiency and ruminal ash and protein NDF digestibility, resulting in a better use of N compounds in the rumen. The PB technique can be used as an alternative to the 15N to estimate microbial synthesis.

Bacterial Community Dynamics across the Gastrointestinal Tracts of Dairy Calves during Preweaning Development.

Microbial communities play critical roles in the gastrointestinal tracts (GIT) of preruminant calves by influencing performance and health. However, little is known about the establishment of microbial communities in the calf GIT or their dynamics during development. In this study, next-generation sequencing was used to assess changes in the bacterial communities of the rumen, jejunum, cecum, and colon in 26 crossbred calves at four developmental stages (7, 28, 49, and 63 days old). Alpha diversity differed among GIT regions with the lowest diversity and evenness in the jejunum, whereas no changes in alpha diversity were observed across developmental stage. Beta diversity analysis showed both region and age effects, with low numbers of operational taxonomic units (OTUs) shared between regions within a given age group or between ages in a given region. Taxonomic analysis revealed that several taxa coexisted in the rumen, jejunum, cecum, and colon but that their abundances differed considerably by GIT region and age. As calves aged, we observed lower abundances of taxa such as Bacteroides, Parabacteroides, and Paraprevotella with higher abundances of Bulleidia and Succiniclasticum in the rumen. The jejunum also displayed taxonomic changes with increases in Clostridiaceae and Turicibacter taxa in older calves. In the lower gut, taxa such as Lactobacillus, Blautia, and Faecalibacterium decreased and S24-7, Paraprevotella, and Prevotella increased as calves aged. These data support a model whereby early and successive colonization by bacteria occurs across the GIT of calves and provides insights into the temporal dynamics of the GIT microbiota of dairy calves during preweaning development.IMPORTANCE The gastrointestinal tracts (GIT) of ruminants, such as dairy cows, house complex microbial communities that contribute to their overall health and support their ability to produce milk. For example, the rumen microbiota converts feed into usable nutrients, while the jejunal microbiota provides access to protein. Thus, establishing a properly functioning GIT microbiota in dairy calves is critical to their productivity as adult cows. However, little is known about the establishment, maintenance, and dynamics of the calf GIT microbiota in early life. In this study, we evaluated the bacterial communities in the rumen, jejunum, cecum, and colon in dairy calves across preweaning development and show that they are highly variable early on in life before transitioning to a stable community. Understanding the dairy calf GIT microbiota has implications for ensuring proper health during early life and will aid in efforts to develop strategies for improving downstream production.