Gyr Dairy Research Articles

Performance and grazing behavior of Gyr dairy heifers in integrated production systems in the Cerrado biome

The study aimed to assess the performance of Gyr dairy heifers in four pasture systems: renovated pasture (RP), non-renovated pasture (NRP), crop-livestock integration (CLI) and crop-livestock-forest integration (CLFI). For our study, we used a Marandu Palissadegrass pasture with a slight to moderate stage of degradation. The experimental area had 7.5 hectares which were divided into 3 blocks with four grazing systems: RP, NRP, CLI and CLFI. Thirty-four Gyr dairy heifers with an initial body weight (BW) of 206.9 kg were used. There was no difference in total forage production between the grazing systems. The RP system had a higher % of leaves, while the NRP showed a lower % of leaves and a higher % of dead material. The CLFI showed the highest % of crude protein (CP) in the forage, and lowest levels in the NRP. There was no difference between the grazing systems in the % of neutral detergent fiber (NDF) and acid detergent fiber (ADF). When the BW factor was analyzed in isolation, it was observed that the NRP had a higher BW and there was a linear increase in BW as the grazing cycles progressed. There was an interaction between grazing systems and evaluation periods for the variables related to grazing behavior, with emphasis on the heifers in the NRP system, which ruminated for longer and grazed for less time during the evaluation period. The RP, CLI, and CLFI systems, when established, promoted a pasture of better morphological and nutritional quality for rearing Gyr dairy heifers.

Genetic parameters for oocytes and embryo production and their association with linear type traits in dairy Gyr cattle

In vitro embryo production is one of the main reproductive techniques used in dairy Gyr cattle. In addition, linear type measures are well characterized and have been used in dairy Gyr breed selection for the last 4 decades. The estimation of genetic parameters for the number of aspirated oocytes and in vitro-produced embryos associated with the linear type measures would support genetic progress for animal breeding programs toward embryo production. This study aimed to estimate genetic parameters for aspirated oocytes, embryo in vitro production, and linear type traits, exploring the association between them. The repeatability model was applied to 14,251 ovum pick-up events from 1,916 Gyr donors. A subset of 604 donors from the same group had their body measurements taken. Single- and 2-trait analyses were carried out using the BLUPF90 family programs. Heritability estimates of 0.38, 0.34, and 0.20 were obtained for total oocytes, viable oocytes, and embryos, respectively, and the heritability of the linear type traits ranged from 0.22 to 0.40. High genetic correlations between total oocytes and viable oocytes (0.99), and between oocytes (total and viable) and embryos (0.83) were obtained. Low to high genetic (-0.07 to 0.92) and phenotypic (0.32-0.86) correlations were obtained between the linear type traits. Moreover, low phenotypic correlations (0.01-0.13) were observed for oocytes (total and viable) and embryos with the linear type traits, whereas low to moderate genetic correlations (0.07-0.42) were observed between the same traits, especially for ilium width (0.42), rump area (0.38), and hip height (0.33). Thus, selection for in vitro production is achievable in Gyr dairy cattle, and superior genetic progress is associated with the selection of oocytes (total and viable). Furthermore, the moderate genetic association between oocytes and embryos with linear type traits, especially ilium width suggests that progress on in vitro embryo production may be achieved by accessing these measurements.

Energy requirement for primiparous Holstein × Gyr crossbred dairy cows

Our objective was to estimate the requirements of metabolizable energy (ME) and NEM of lactating and dry cows, the efficiency of ME utilization for milk production (kl) and tissue gain (kg), and the use of body energy mobilization for milk production (kt) throughout the lactation of primiparous crossbred Holstein × Gyr cows, using open-circuit respiration chambers. Twenty-nine primiparous Holstein × Gyr crossbred cows with an initial BW averaging 563 ± 40.1 kg and 2.5 ± 0.09 yr old were used throughout lactation and dry periods. The cows were kept nonpregnant throughout the study to eliminate possible confounding factors. Apparent digestibility assays, followed by calorimeter measurements, were performed 6 times throughout the lactation period. In the dry-off period, the cows were also evaluated but fed with restricted intake (DMI = 1.1% BW/d) to achieve heat production close to maintenance. After 21 d of diet adaptation, an apparent digestibility assay followed by calorimeter measurements was performed. Parameter estimates for lactation period were obtained by mixed models including lactation stage as repeated measures. For restricted feeding at dry-off and fasting period assays, the requirements were estimated by exponential regression. For whole lactation, the values of the ME requirement for maintenance (MEM) and NEM were 0.588 and 0.395 MJ/BW0.75, respectively. The efficiencies of kl, kg, and kt were 0.672, 0.771, and 0.814, respectively. However, MEM and NEM were higher in early and mid lactation than late, whereas kl was higher in early than other lactation stages. Dry and nonpregnant cows had MEM of 0.434 MJ/BW0.75 and NEM of 0.351 MJ/BW0.75 for maintenance level, and MEM of 0.396 MJ/BW0.75 and NEM of 0.345 MJ/BW0.75 for fasting metabolism level, and efficiency of ME utilization for maintenance was 0.80. Our findings confirmed that F1 crossbred Holstein × Gyr dairy cows have differences in energy requirement and efficiency throughout the lactation stages, suggesting the use of different values in each stage. The estimated values of energy requirement for maintenance and efficiencies for primiparous lactating crossbred Holstein × Gyr were similar to those reported in the literature in specific studies and requirements systems.

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

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-1β 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). 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. 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-1β 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. Adaptations in Holstein × Gyr heifers such as ruminal microbiota, tick resistance, nucleotide substitutions in IL-1β gene, and hormone concentration suggest a better energy metabolism and thermoregulation resulting in better performance in tropical grazing systems.

Milk fatty acid profile of cows grazing elephant grass BRS Kurumi pasture with and without energy supplementation

This study evaluated the effects of energy supplementation on the intake and milk fatty acid composition of cows grazing BRS Kurumi elephant grass pasture during the rainy season. Two treatments (with and without supplementation) were evaluated using a switchback design with six Holstein × Gyr dairy cows after the peak of lactation. The average milk yield, body weight, and days in milk of the cows at the beginning of the study were 18.0±2.89 kg day−1, 560±66 kg, and 99±12, respectively. The evaluations were performed over three grazing cycles, with adaptation periods of 14 days and six days of sampling. In the energy supplementation treatment, each cow received 3 kg day−1 of ground corn (as-fed basis), with 2 kg day−1 at the morning milking and 1 kg day−1 at the afternoon milking. The ground corn presented 87.5% dry matter, 7.3% crude protein, 5.1% ether extract, and 85% of total digestible nutrients. The cows supplemented with ground corn consumed more oleic (+567%) and linoleic (+88%) acids. Unsupplemented cows consumed 26% more α-linolenic acid and produced milk with more oleic (+10%), vaccenic (+23%), and rumenic (+21%) acids, and less (−7%) pro-atherogenic fatty acids (lauric + myristic + palmitic acids). Milk fat from unsupplemented cows showed better nutritional quality, with lower atherogenicity and thrombogenicity indices and a higher hypo/hypercholesterolemic fatty acid ratio.

Relationship among thermal environment, stage of lactation, body characteristics, yield and milk constituents of dairy Gyr cows managed on pasture.

Our aims were to evaluate changes in body characteristics, milk yield and milk constituents as well as to determine the relationship between the thermal environment and production characteristics during the first lactation of dairy Gyr cows managed on pasture. Between 2013 and 2015, forty-five primiparous dairy Gyr cows were evaluated from prepartum to 10 months of lactation in Southeast of Brazil. Body weight, body condition score (BCS), subcutaneous fat thickness (SFT), milk yield (305 d), and milk constituents were collected monthly and progesterone was collected weekly. Additionally, we determined the temperature humidity index (THI) based on microclimate data. Overall, the cows lost body weight until six months of lactation and there was a progressive decrease in BCS, SFT, milk yield and milk lactose as the months in lactation progressed. In contrast, there was an increase in milk fat, milk protein and milk solids. The thermal environment did not pose a consistent heat challenge, nevertheless, we found a positive correlation between the average THI two days before milk collection with milk yield, fat and lactose contents, but in contrast a negative correlation was found with total solids and protein. In conclusion, the THI and months of lactation affected the yield and constituents of milk. However, more studies are necessary to understand the impacts of body characteristics and thermal environment on yield and milk constituents throughout the productive life of Gyr dairy cows.

Phenotypic and genetic relationships among anogenital distance, anti-Müllerian hormone, and in vitro embryo production in Gyr dairy cattle

Anti-Müllerian hormone (AMH) concentration and number of recovered oocytes (ROOC) are phenotypic parameters associated with in vitro embryo production (IVEP). More recently, anogenital distance (AGD) has been proposed as a proxy for fertility in dairy cattle that is easy to collect at a low cost. The aim of this study was to characterize the AGD and its phenotypic and genetic associations with AMH and IVEP in Bos indicus Gyr dairy cattle. The hypothesis was that the number of ROOC, in vitro-produced embryos, and AMH concentration would increase as the AGD decreases. From July to December 2021, a single morphometrical measurement of AGD was collected in 552 donors from 6 herds in Brazil. A subset of donors had AMH assayed on the same day. Only ovum pick-up events that occurred up to 12 mo preceding and 7 mo succeeding the AGD measurement were used to assess the association between AGD, AMH, and IVEP. Thus, 472 donors (1,551 ovum pick-up events and 140 donors with AMH) were considered in the analysis. A raw average was calculated for each individual donor's ROOC, viable oocytes, total produced embryos, viability rate, and embryo rate (defined as total produced embryos/viable oocytes). Comparisons were conducted within the age categories of 3 to <6 yr or 6 to <10 yr. Phenotypic associations were performed in SAS software (SAS Institute Inc., Cary, NC). Genetic correlations were estimated using the BLUPF90 family of programs. The AGD (128.7 mm ± 14; mean ± standard deviation) had a normal distribution and was highly variable (83 to 172 mm) among the Gyr population. Our experimental hypothesis was partially supported by a phenotypic association of a greater number of total produced embryos (R2 = 0.023) as AGD decreased. Our results failed to support an increase in AMH concentration along with a decrease in AGD. In addition, positive and low genetic correlations were observed between AGD and viable oocytes (r = 0.08), and embryo rate (r = 0.20). A greater number of viable oocytes and embryos were observed in donors in the high compared with intermediate and low ROOC categories within both age categories. The age interval of 3 to <6 yr showed a greater number of recovered and viable oocytes for the high AMH compared with the low category, but no differences were observed among the AGD categories. In summary, for the Gyr breed, AGD was phenotypically inversely associated with a quantity-related parameter, such as the total number of produced embryos. In contrast, AGD showed a low genetic correlation with qualitative-related outcomes such as viable oocytes and embryo rate. Further studies should be performed to validate these retrospective analyses and to better understand the association between AGD and IVEP.

Differential average daily gain of pregnant Holstein × Gyr dairy heifers causes placental adaptations to support fetal growth and development

This study aimed to evaluate the effects of differential average daily gain targets of dairy heifers throughout gestation on placental hemodynamics, uterine involution, colostrum production of the heifers, and effects on newborn calf weight and immunity transfer. Fourteen Holstein × Gyr heifers with an average body weight of 446 ± 46.7 kg and age of 25 ± 3.9 mo were randomly assigned to the following treatments: moderate body weight gain (MOD, n = 7), where heifers were fed to achieve 0.50 kg/d; and high body weight gain (HIG, n = 7), where heifers were fed to achieve 0.75 kg/d. Target average daily gains were established based on common tropical dairy production systems. The heifers received a total mixed ration feed twice daily starting at 70 d of gestation. Placentome vascularization was assessed using a color Doppler ultrasound at 180, 210, and 240 d of gestation. After calving, cotyledons were counted and sampled to analyze the mRNA expression of placental angiogenesis markers. After birth, calves were weighed and fed colostrum, and transfer of passive immunity efficiency was assessed. A significant increase in cotyledons was detected for MOD placenta soon after expulsion (81.5 ± 12.91 vs. 63.6 ± 10.52). Placentome vascularization at the final third of gestation increased for MOD heifers compared with HIG. Greater mRNA expression after membrane expulsion of VEGFB and IGFR1 in cotyledons and a greater estradiol concentration in circulation 1 d before calving was found for MOD heifers compared with HIG heifers; however, uterine involution postpartum was not different between treatment groups. Greater colostrum production was observed in HIG heifers (3.9 ± 1.05 vs. 2.2 ± 1.57 L) but with lower quality (25.2 ± 0.51 vs. 29.5 ± 0.65 Brix). No differences were observed in birth weight or transfer of passive immunity efficiency between treatments; however, HIG calves had significantly greater vitality scores than MOD calves. The results of this study indicate that a moderate feeding regimen enhances placental blood flow by increasing angiogenesis, which suggests improved nutrient transfer to the fetus without major effects on its development during the neonatal stage, colostrum production, or uterine involution in the heifers.

Sensor validation to record rumination and analysis of behavioral parameters of dairy Gyr heifers in feedlot systems

The use of sensors for livestock monitoring has grown in the last decade, motivated not only by the search for improvements in animal production and health, but also by the better use of physical, financial, and human resources in the management of livestock. Since precision livestock farming depends on technological innovation, including the use of sensors, it is essential to validate their applicability in confined animals. Therefore, the objective was to evaluate the functioning of the SCR Heatime® HR System sensor in heifers and analyze the behavioral differences of these animals in two feedlot systems (tie-stall and loose-housing). Eleven Gyr heifers of 10months of age and an average body weight of 179 ± 26kg were used. Animals were equipped with the SCR Heatime® HR System 7days before the evaluations for adaptation, with the behavioral and system studies carried out during two periods each of 5days, for 8h a day. Five heifers were housed in tie-stall bedding and six were housed in loose-housing. After the evaluations for a period, animals have been switched systems in the following period. While the animals had the sensors attached to their bodies, behavioral evaluations were also performed visually, every 3min by two evaluators per system. Behavior activities were characterized as standing, lying, idle standing, idle lying, ruminating standing, ruminating lying, feed, and water intake. The regression for the rumination activity recorded between the sensor and the visual assessment was significant only for loose-housing (P = 0.0002), but the Pearson correlation between both was negative and low (r = - 0.25; P = 0.0002). The sensor overestimated rumination by 27.3% in loose-housing (28 vs. 22min/2h) and 38.5% in tie-stall (36 vs. 26min/2h). Thus, when considering the different feedlot systems, validation was not possible due to the overestimation of time spent on rumination activity determined by the sensor. In the behavioral comparison between the systems by visual assessment, there was a significant difference (P < 0.05) for the behaviors of motor activity, idle lying, total idle time, and feed intake between the animals in the two housing systems. As for idle standing, ruminating standing, total rumination time, and water intake, there was no difference (P > 0.05). However, the time spent ruminating lying was greater from 10:00 to 12:00h (43 ± 3min/2h) in the tie-stall, whereas in the loose-housing the animals distribute more uniformly their rumination from 08:00 to 16:00h (26min/2h on average). Therefore, the use of the SCR Heatime® HR System sensor is not recommended for Gyr heifers housed in tie-stall and loose-housing systems. Regarding the daytime range of rumination and the accuracy improvements of similar sensors, it is recommended to develop them in both feedlot systems using the periods of less rumination in early morning in tie-stall and late afternoon in loose-housing.

Effects of Training for First Milking Involving Positive Tactile Stimulation on Post-Calving Maternal Behaviors in Primiparous Gyr Dairy Cows

In dairy systems with Zebu breeds, calves are not immediately separated from their dams after calving; consequently, maternal care and protective behavior are important, influencing both productive performance and stockpeople's safety. Our objectives were to: (1) investigate the effects of a training protocol involving pre-calving positive stimulation, delivered prior to calving, on the maternal care of primiparous Gyr cows; and (2) evaluate the effects of this training protocol on maternal protective behavior towards handlers during the first calf handling. Primiparous dairy Gyr cows (n = 37) were allocated into two groups: training (n = 16) and control (n = 21). Animal behaviors were recorded in three periods: post-calving, first calf handling, and post-handling. Maternal protective behavior during calf handling was assessed from measures of aggressiveness, attention, displacement, and agitation. Calf latency to stand up (p < 0.01) and sex (p < 0.01) differed between the training and control groups. The training group had less touching (p = 0.03), more time not interacting with the calf (p = 0.03), tended to be less protective (p = 0.056), and moved less (p < 0.01) during the first handling of their calves. In conclusion, the primiparous dairy Gyr cows subjected to pre-calving training protocol displayed less maternal care and displacement during the first handling of their calves and tended to be less protective.

How to use recombinant bovine somatotropin in crossbred Holstein × Gyr (3/4 and 7/8) cows?

The aim of this study was to evaluate the effects of dose, start time, and application interval of recombinant bovine somatotropin (rbST) on performance, health, and reproduction parameters of crossbred Holstein × Gyr dairy cows (3/4 and 7/8). A 2 × 2 × 2 factorial study was designed to test the effects of application dose (250mg rbST or 500mg rbST), start of application (40 or 63days in milk (DIM)), and application interval (12 or 14days); 180 crossbred Holstein × Gyr cows were enrolled. Treatments with 500mg rbST resulted in increased milk production, 3.5% fat-corrected milk (FCM), and energy-corrected milk (ECM). In the factorial design analysis, greater FCM, ECM, and milk solid production (kg/day) were observed when 500mg rbST was started at 63 DIM, while 250mg rbST resulted in greater milk production (kg/day), FCM, ECM, and milk solids (kg/day) when administered at 12-day intervals. Administration of 500mg rbST resulted in an increase of days open and number of services per pregnancy (P = 0.01). Holstein × Gyr cows (3/4 and 7/8) presented a superior productive response to rbST when treated with 500mg starting at 63 DIM and at 14-day intervals.

Taxonomic and predicted functional signatures reveal linkages between the rumen microbiota and feed efficiency in dairy cattle raised in tropical areas.

Ruminants digest plant biomass more efficiently than monogastric animals due to their symbiotic relationship with a complex microbiota residing in the rumen environment. What remains unclear is the relationship between the rumen microbial taxonomic and functional composition and feed efficiency (FE), especially in crossbred dairy cattle (Holstein x Gyr) raised under tropical conditions. In this study, we selected twenty-two F1 Holstein x Gyr heifers and grouped them according to their residual feed intake (RFI) ranking, high efficiency (HE) (n = 11) and low efficiency (LE) (n = 11), to investigate the effect of FE on the rumen microbial taxa and their functions. Rumen fluids were collected using a stomach tube apparatus and analyzed using amplicon sequencing targeting the 16S (bacteria and archaea) and 18S (protozoa) rRNA genes. Alpha-diversity and beta-diversity analysis revealed no significant difference in the rumen microbiota between the HE and LE animals. Multivariate analysis (sPLS-DA) showed a clear separation of two clusters in bacterial taxonomic profiles related to each FE group, but in archaeal and protozoal profiles, the clusters overlapped. The sPLS-DA also revealed a clear separation in functional profiles for bacteria, archaea, and protozoa between the HE and LE animals. Microbial taxa were differently related to HE (e.g., Howardella and Shuttleworthia) and LE animals (e.g., Eremoplastron and Methanobrevibacter), and predicted functions were significatively different for each FE group (e.g., K03395-signaling and cellular process was strongly related to HE animals, and K13643-genetic information processing was related to LE animals). This study demonstrates that differences in the rumen microbiome relative to FE ranking are not directly observed from diversity indices (Faith's Phylogenetic Diversity, Pielou's Evenness, Shannon's diversity, weighted UniFrac distance, Jaccard index, and Bray-Curtis dissimilarity), but from targeted identification of specific taxa and microbial functions characterizing each FE group. These results shed light on the role of rumen microbial taxonomic and functional profiles in crossbred Holstein × Gyr dairy cattle raised in tropical conditions, creating the possibility of using the microbial signature of the HE group as a biological tool for the development of biomarkers that improve FE in ruminants.

Genotype-environment interaction for milk production of Gyr cattle in Brazil and Colombia.

Genotype by environment interactions (G × E) can play an important role in cattle populations and should be included in breeding programs in order to select the best animals for different environments. The aim of this study was to investigate the G × E for milk production of Gyr cattle in Brazil and Colombia by applying a reaction norm model used genomics information, and to identify genomic regions associated with milk production in the two countries. The Brazilian and Colombian database included 464 animals (273 cows and 33 sires from Brazil and 158 cows from Colombia) and 27,505 SNPs. A two-trait animal model was used for milk yield adjusted to 305days in Brazil and Colombia as a function of country of origin, which included genomic information obtained with a single-step genomic reaction norm model. The GIBBS3F90 and POSTGSf90 programs were used. The results obtained indicate G × E based on the reranking of bulls between Brazil and Colombia, demonstrating environmental differences between the two countries. The findings highlight the importance of considering the environment when choosing breeding animals in order to ensure the adequate performance of their progeny. Within this context, the reranking of bulls and the different SNPs associated with milk production in the two countries suggest that G × E is an important effect that should be included in the genetic evaluation of Dairy Gyr cattle in Brazil and Colombia. The Gyr breeding program can be optimized by choosing a selection environment that will allow maximum genetic progress in milk production in different environments within and between countries.

Escherichia coli and Pseudomonas aeruginosa Isolated From Urine of Healthy Bovine Have Potential as Emerging Human and Bovine Pathogens.

The study of livestock microbiota has immediate benefits for animal health as well as mitigating food contamination and emerging pathogens. While prior research has indicated the gastrointestinal tract of cattle as the source for many zoonoses, including Shiga-toxin producing Escherichia coli and antibiotic resistant bacteria, the bovine urinary tract microbiota has yet to be thoroughly investigated. Here, we describe 5 E. coli and 4 Pseudomonas aeruginosa strains isolated from urine of dairy Gyr cattle. While both species are typically associated with urinary tract infections and mastitis, all of the animals sampled were healthy. The bovine urinary strains were compared to E. coli and P. aeruginosa isolates from other bovine samples as well as human urinary samples. While the bovine urinary E. coli isolates had genomic similarity to isolates from the gastrointestinal tract of cattle and other agricultural animals, the bovine urinary P. aeruginosa strains were most similar to human isolates suggesting niche adaptation rather than host adaptation. Examination of prophages harbored by these bovine isolates revealed similarity with prophages within distantly related E. coli and P. aeruginosa isolates from the human urinary tract. This suggests that related urinary phages may persist and/or be shared between mammals. Future studies of the bovine urinary microbiota are needed to ascertain if E. coli and P. aeruginosa are resident members of this niche and/or possible sources for emerging pathogens in humans.

Genetic parameters for body weight and milk production of dairy Gyr herds.

The aim of this study was to estimate genetic parameters for cow weight at calving (CW) and cumulative 305-day milk yield (MY305) in dairy Gyr cattle by two-trait analysis. The study used 1,847 CW records, in which 418 females presented more than one measure, and 4,048 MY305 records, wherein 1068 females provided repeated measures, from 2,339 females belonging to three herds, which calved between 1986 and 2019. Variance components were estimated by the restricted maximum likelihood method (REML) using a two-trait animal model. The model included direct additive genetic, permanent environmental and residual effects as random effects and the fixed effects of contemporary group, formed by animals that had calved on the same farm year and season, and age of cow at calving as covariates (fitted as linear and quadratic effect). The heritability estimates for CW and MY305 were 0.21 ± 0.06 and 0.29 ± 0.04, respectively, and repeatability estimates were 0.49 ± 0.03 and 0.49 ± 0.02. The genetic correlation between CW and MY305 was positive and of low magnitude (0.33 ± 0.18), indicating that selection for MY305 will cause little genetic change in the weights of dairy Gyr animals. The genetic trends of breeding values of analyzed traits showed marked genetic gains in MY305, with little changes in CW of dairy Gyr cows over the years in the herds studied, which is an important result considering the production systems adopted in the tropics.

Estrus Prediction Models for Dairy Gyr Heifers.

Simple SummaryIntraruminal devices are already being used to predict reproductive events in cattle. For this prediction, several models and approaches can be used. The aim of this study was to evaluate changes in rumen reticulum temperature (RRT) and activity (ACT) during estrus in Dairy Gyr heifers and to evaluate different models for estrus prediction. There was an increase in both RRT and ACT in the estrus period compared to the same period on the day before and the day after estrus. Among the mathematical models, Random Forest had the best performance. The present results suggest that RRT and ACT can contribute to the identification of estrus and be of value for improving the reproductive efficiency of Zebu herds in tropical regions.Technological devices are increasingly present in livestock activities, such as identifying the reproductive status of cows. For this, predictive models must be accurate and usable in the productive context. The aims of this study were to evaluate estrus-associated changes in reticulo-rumen temperature (RRT) and activity (ACT) in Dairy Gyr heifers provided by reticulo-rumen boluses and to test the ability of different models for estrus prediction. The RRT and ACT of 45 heifers submitted to estrus synchronization were recorded using reticulo-rumen boluses. The means of RRT and ACT at different time intervals were compared between the day before and the day of estrus manifestation. An analysis of variance of RRT and ACT was performed using mixed models. A second approach employed logistic regression, random forest, and linear discriminant analysis models using RRT, ACT, time of day, and the temperature-humidity index (THI) as predictors. There was an increase in RRT and ACT at estrus (p < 0.05) compared to the same period on the day before and on the day after estrus. The random forest model provided the best performance values with a sensitivity of 51.69% and specificity of 93.1%. The present results suggest that RRT and ACT contribute to the identification of estrus in Dairy Gyr heifers.

Determination of energy and protein requirements of preweaned dairy calves: A multistudy approach

The first studies concerning nutrient requirements for preweaned dairy calves were from the 1920s and 1930s; however, few studies were published in the following decades. We aimed to determine energy and protein requirements of preweaning Holstein and Holstein × Gyr dairy calves in a multistudy meta-regression. We used a database composed of individual measurements of 166 preweaned male calves (138 submitted to treatments and 28 used as the reference group) from 4 studies that used the methodology of comparative slaughter. Animals with less than 15/16 of Holstein genetic composition were considered crossbred Holstein × Gyr, whereas other animals were considered Holstein. Net energy requirements for maintenance (NEM) were determined by the regression between heat production and metabolizable energy intake (MEI). The metabolizable energy requirements for maintenance were calculated by the iterative method, and the efficiency of use of metabolizable energy for maintenance was obtained by NEM divided by the metabolizable energy requirements for maintenance. Net energy requirements for gain (NEG) were estimated using a regression of the retained energy (RE) as a function of empty body weight (EBW) and empty body gain (EBG). The efficiency of use of metabolizable energy for gain was estimated by the regression of RE as a function of MEI, but with partitioning the MEI into MEI from liquid feed and MEI from starter feed. Additionally, the effect of a liquid feed (milk or milk replacer) was tested on the slope of the regression. The metabolizable protein requirements for maintenance (MPM) were estimated using the intercept of the regression between the metabolizable protein intake (MPI) and average daily gain. The MPM was determined as the ratio between the intercept and the metabolic body weight. Net protein requirements for gain (NPG) were estimated by the regression between retained protein, EBG, and RE. The efficiency of use of metabolizable protein for gain was estimated by the regression of the retained protein as a function of MPI, but with partitioning the MPI into MPI from liquid feed and MPI from starter feed. Additionally, the effect of a liquid feed (milk or milk replacer) was tested on the regression slope. Breed did not influence any of the nutrient requirements' estimates. The NEM was estimated as 70.2 kcal/metabolic body weight per day. The efficiency of use of metabolizable energy for maintenance observed was 66%. The NEG was estimated by the equation NEG = 0.0901 × EBW0.75 × EBG0.9539. The efficiency of use of metabolizable energy for gain was estimated as 57.6, 49.3, and 41.2% for milk, milk replacer, and starter feed, respectively. The MPM was estimated as 4.22 g/EBW0.75 per day, and the NPG was determined by the equation: NPG = 30.06 × EBG + 70.98 × RE. The efficiency of use of metabolizable protein for gain was estimated as 71.9, 59.2, and 44.4% for milk, milk replacer, and starter feed, respectively. We concluded that no differences were observed in energy and protein requirements between Holstein and Holstein × Gyr crossbred cows. The efficiencies of use of metabolizable energy and protein are greater for milk when compared with milk replacer and starter feed. Therefore, we propose that the equations generated herein should be used to estimate energy and protein requirements of preweaned Holstein and Holstein × Gyr crossbred dairy calves raised under tropical conditions.

Shade Modifies Behavioral and Physiological Responses of Low to Medium Production Dairy Cows at Pasture in an Integrated Crop-Livestock-Forest System.

Simple SummaryThe husbandry of high-producing dairy cattle on pasture in tropical regions promotes heat stress and alters physiological and behavioral parameters. However, it is unknown how the physiological and behavioral responses of cows more adapted to tropical environments under heat stress conditions, with lower milk production under shaded pasture or full sun conditions. To respond to these questions, Gyr dairy and Girolando cows (5/8 Holstein 3/8 Gyr, and ½ Holstein ½ Gyr) were evaluated in full sun and under natural shade from trees. Behavioral, physiological, and morphological variables were measured, and it was concluded that shaded pasture for dairy zebu cows promotes animal welfare by mitigating animal surface temperature and increasing rumination time.Under conditions of high temperature, humidity, and incidence of solar radiation, dairy cows use behavioral changes as a strategy to decrease the metabolic heat production at pasture. The objective of this study was to evaluate the behavioral and physiological responses of Gyr and Girolando (5/8 Holstein 3/8 Gyr, and ½ Holstein ½ Gyr) dairy cows submitted to environments with and without shade. The experiment was conducted at Embrapa Cerrados (Technology Center for Dairy Zebu breeds—CTZL), Brasilia, Distrito Federal—Brazil, with 48 Gyr and Girolando cows total in the lactation group, with low to medium milk production, in full sun or shade with Eucalyptus urograndis (267 plants/ha−1). The physiological and behavioral characteristics evaluated were panting score, superficial temperature, and time spent grazing, ruminating, and lying down. Other traits included skin and coat thickness, hair diameter, density and length, and predominant coat color. In addition, body measurements, such as body length, the height of withers, chest circumference, and shin circumference, were measured. Shaded cows had 34% longer rumination times than cows in full sun (p = 0.01). With a temperature-humidity index ranging from 79 to 83, the rumination time was 1.7 times higher in cows under shade (p = 0.01) during a 24-h period of observation. There were no significant differences in the grazing time between the environments, but lying time was 23% longer in cows under the sun (p = 0.01). The panting score was not influenced by the environment (p = 0.17). Girolando cows had a 35% higher panting score than Gyr cows (p = 0.01) regardless of the environment. The panting score increased two and a half times during the afternoon compared with the morning (p = 0.01). The surface and rectal core temperatures had significant differences between treatments and time of the day. Body measurements were not different between cows in both environments, but there was a difference between breeds. The use of trees in pastures with a silvopastoral system for dairy zebu cows is indicated to improve grazing behavior, as well as time spent ruminating and lying down.

Seminal plasma insulin-like growth factor I and total protein concentration in peripubertal period of the Gyr bulls.

This study aimed to evaluate the correlation of seminal plasma IGF-I and total proteins from peripubertal bulls with semen characteristics and onset of puberty. Sixteen dairy Gyr bulls were separated into early (n=8) and regular (n=8) groups, according to the onset of puberty. Semen was monthly collected by electroejaculation from 14 to 26months of age, and the onset of puberty was retrospectively determined (17.0±1.6 and 19.2±1.5months, to early and regular group, respectively). Five time points were evaluated (day -60, day -30, day 0, day 30 and day 60days of puberty), being day 0 considered as beginning of puberty. Scrotal circumference and body weight were also assessed. Semen characteristics were evaluated, the seminal plasma was separated by centrifugation and total protein and IGF-I concentrations were determined. There was no difference between groups to concentration of the seminal plasma total proteins, but we found an interaction between group and age. Seminal plasma IGF-I concentrations were not different between early and regular groups; thus, the data were combined for analysis. Combined IGF-I concentrations were positively correlated with sperm motility and concentration, age, body weight and scrotal circumference. Negative correlation was found between IGF-I concentration and total sperm defects. Increased IGF-I was observed in day -30 and day 0 of puberty in early and regular groups, respectively. Seminal plasma total proteins are involved in peripubertal modifications and IGF-I from Zebus dairy bulls can influence the seminal characteristics and the growth factor increase occurs concomitantly with body growth but cannot be used to define puberty bulls earlier.

Performance of crossbred Holstein x Gyr dairy cows, with and without energy supplementation, in BRS Kurumi elephant grass pastures

This study evaluated the effect of energy supplementation with ground corn on the performance of crossbred dairy cows in BRS Kurumi elephant grass pastures managed under rotational stocking during the rainy season. Six Holstein × Gyr cows were used, with average milk production, body weight, body condition score, and days in milk of 18.0±2.89 kg day−1, 560±66 kg, 2.50±0.21, and 99±12, respectively. The experimental design used was the complete reversion (switchback), and the evaluations were conducted over three grazing cycles, with adaptation periods of 14 days and six days of sample collection. The concentrate supplement (ground corn) was supplied twice a day, at a rate of 2 kg cow−1 day−1 in the morning and 1 kg cow−1 day−1 in the afternoon (as-fed basis). A reduction of 23.4% was observed in the pasture dry matter (DM) intake (PDMI) in cows that received energy supplementation, which corresponds to 2.96 kg day-1 less of PDMI when compared to the group without supplementation. This corresponds to a substitution rate of 1.1 kg of pasture per kg of concentrate consumed (DM basis), which reduced the intake (kg cow−1 day−1) of neutral detergent fiber and crude protein by 18.9% and 13.9% in the cows that received ground corn. There were increases of 11.8%, 9.0%, and 10.1%, respectively, in the milk yield, the 3.5% fat-corrected milk yield, and the energy-corrected milk yield of the cows that received ground corn. The response to supplementation in kg of milk per kg of DM of concentrate consumed was 0.57, and the milk contents of fat, protein, and lactose did not differ between treatments. The energy supplementation with 3 kg cow−1 day−1 of ground corn resulted in an increase of 11.8% in the milk yield of Holstein × Gyr dairy cows grazed on BRS Kurumi elephant grass, as well as promoted increases in the daily protein, lactose, and total solids yields. In addition, the provision of 3 kg day−1 of ground corn for lactating cows grazing on BRS Kurumi increased the efficiency in the use of dietary nitrogen.