Gyr Cows Research Articles

Use Intensity of Progesterone Devices for Fixed-time Artificial Insemination in Gyr Crossbred Cows from the Peruvian Tropics

Background: The implementation of routine fixed-time artificial insemination programs can generate significant waste and costs, which good management practices can help mitigate. The objective of the study was to assess the effects of second- and third-use progesterone devices on estrus characteristics and pregnancy rates in synchronized crossbred Gyr cows. Methods: Ten cows were synchronized with first-use Bovine Intravaginal Progesterone Devices (DIB), nine with second-use DIB and ten with third-use DIB. All cows were ³90 days postpartum, had an average milk production of 6.9±1.9 L/day and were aged 4-10 years. Estrus signs were recorded at insemination and pregnancies were confirmed at 60 days by ultrasonography. Result: No significant associations were found between DIB use intensity and estrus detection patch response, mucus color, body condition score (CC), calvings, or breed purity (p greater than 0.05). Body condition was associated with uterine turgor tone (p less than 0.05) and 100% of cows with CC 3.0 showed turgor tone 3. The highest pregnancy rate was found in second-use DIB (55.6%) and CC 2.8 (47.1%), though neither association was significant (p greater than 0.05). DIBs may be used up to a second-use, as cervical mucosal stimulation and pregnancy rate remain unaffected.

Effect of replacing ground corn with cactus pear Nopalea cochenillifera (L.) on feed intake and digestibility, water intake, milk production and composition in Holstein × Gyr cows.

The objective of this study was to evaluate the intake and digestibility of nutrients, production and composition of milk, and water intake of lactating dairy cows fed standard diets in which ground corn (C) was replaced by up to 100% in the diet by cactus pear (CP). Eight Girolando cows (½ Gyr x ½ Holstein), 3rd calf multiparous, with 60 to 80 days of lactation and an average weight of 450.0 ± 30.0kg, were randomly distributed in a double Latin square (4 × 4). Four experimental diets were evaluated: (100% C + 0% CP), (66.6% C + 33.3% CP), (33.3% C + 66.6% CP), and (0% C + 100% CP). There was a difference (P < 0.05) in the intake of CP and EE (kg.day- 1), with a quadratic effect and a linear reduction, respectively, with substitution. The maximum CP intake of 3.05kg.day- 1 was found at 46.07% and EE intake fell by 3.81g for each percentage unit of cactus pear added to the diet. There was a quadratic difference (P < 0.05) for DM intake in %BW and g.kg BW0,75, with maximum values of 3.97%BW and 186.8g.kg BW0,75 with the substitution of 54.83 and 53.17%, respectively. There was a quadratic effect (P < 0.05) for the intake of NDF in %BW, with the maximum intake of 1.3% at the 74.69% substitution level. There was a linear reduction (P < 0.05) in the digestibility of DM, NDF, and TDN, and for the other nutrients there was no substitution effect (P > 0.05). There was no difference (P > 0.05) in milk production and composition. There was a linear reduction (P < 0.05) in water intake. Cactus pear can be used in a promising way to replace ground corn up to 100% in the diet of lactating dairy cows.

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.

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.

Intake, digestibility, energy and nitrogen utilisation, and enteric methane emission in Holstein and Girolando-F1 cows during the transition period

ABSTRACT This study aimed to evaluate intake, energy and nitrogen balance as well as methane emission in Holstein and ½ Holstein ½ Gyr (Girolando-F1) cows during the transition period. Twenty-four cows (12 Holstein and 12 Girolando-F1) were used to evaluate feed intake, apparent digestibility, heat production and methane emission, carried out in two periods: from 28 to 19 days pre-calving and from 15 to 23 days post-calving. A completely randomised design was used and data were analysed by ANOVA within periods (pre- and post-calving) considering the main effect of genetic groups. Girolando-F1cows presented greater body condition score (BCS) compared with Holstein. During pre-calving, there were no differences between genetic groups, except for highest heat production per kilogram of metabolic body weight for Holstein cows. After calving, Holstein cows had greater intake of DM, nitrogen, NDF per kg of BW and produced more heat per kg of metabolic body weight. Holstein cows yielded more milk and fat-corrected milk (FCM4%) compared with Girolando-F1 cows. Holstein cows presented higher methane emission per unit of BW and of metabolic weight. Emissions of enteric methane per kilogram of milk and per kilogram of FCM4% tended to be lower for Holstein compared with Girolando-F1 cows. Nitrogen and energy retention were similar for both Holstein and Girolando-F1 at pre- and post-calving. Despite differences in BCS, DMI, and milk yield, Girolando-F1 and Holstein cows present overall similar energy efficiency, albeit Holstein cows tended to present less methane emission per kg of eligible product (milk).

Marcadores externos para estimativa de consumo por vacas leiteiras em confinamento

Abstract The accurate determination of individual dry matter intake (DMI) is an important parameter for evaluating the nutritional value of a diet and allows for an adequate supply of food according to the nutritional requirements of each animal. When it is not possible to measure this parameter using a direct method, the DMI can be estimated based on faecal production markers and the in vitro digestibility of dry matter (IVDMD) of the diet. The objective of this study was to evaluate the effects of the external marker titanium dioxide (TiO2) and enriched and modified hydroxyphenylpropane (LIPE®) on DMI. Four multiparous Holstein × Gyr cows with an average of 60 days in milk and 488 kg of body weight were used. The animals were housed in a free stall barn and fed diets based on sugarcane silage supplemented with concentrate composed of ground corn, cottonseed meal and 0%, 5%, 10% and 15% whole cottonseed on a dry matter (DM) basis. A 4 x 4 Latin square design was adopted. The DMI was determined by the ratio between the faecal production estimated by the markers and the IVDMD of the diet, with faeces collected by rectal grabbing twice a day for a period of seven days. There was no difference (P&gt;0.05) in the DMI estimated by the external markers TiO2 and LIPE® (10.3 vs. 12.1; 11.1 vs. 12.5; 10.2 vs. 12.9; and 12.7 vs. 10.9 kg/cow/day in relation to the measured DMI for diets with 0%, 5%, 10% and 15% inclusion of whole cottonseed, respectively). The external markers LIPE® and TiO2 proved to be suitable for estimating cow DMI. Regardless of the diet offered, both external markers can be used to replace the external marker chromic oxide, as the DMI estimated by them did not differ from the DMI measured in the trough.

Protein requirements for pregnant dairy cows

We aimed to estimate the protein requirements of pregnant Holstein × Gyr cows. Sixty-one Holstein × Gyr (HG) cows were used, with an average initial BW of 480 ± 10.1 kg and 5 ± 0.5 yrs of age. Cows were divided into 3 groups: pregnant (n = 43), non-pregnant (n = 12), and baseline (n = 6). Baseline animals were slaughtered before starting the experiment to estimate the initial body composition of the remaining animals. Pregnant and non-pregnant cows received 2 diets: maintenance and ad libitum. Pregnant cows were slaughtered at 139, 199, 241, and 268 gestation days (GD). First, we used data only from non-pregnant cows to determine the requirements for maintenance and growth in adult cows. The requirements of metabolizable protein for maintenance (MPm; g/EBW0.75/d) were estimated using a linear regression between the metabolizable protein intake (MPI, g/d) and average daily gain (g/d), and the MPm was defined as the intercept divided by the average BW0.75. Net protein requirements for gain (NPg; g/d) were estimated by the first derivative of the allometric equation between final crude protein (CP) in the body (kg) and the final EBW (kg). The efficiency of use of metabolizable protein for gain (k) was calculated from the regression between the retained protein (g/EBW0.75/d) and the MPI (g/EBW0.75/d), and k was the slope of this regression. The MPI was estimated by combining microbial protein synthesis (purine derivatives) with the digestible rumen undegradable protein [(total protein intake minus RDP) × intestinal digestibility]. Second, an exponential model was used to fit the protein accumulation in the gestational components in the function of GD. The first derivative of that model was considered the net requirement for gestation (NPgest). The efficiency of protein utilization for gestation (kgest) was calculated by the iterative method using the equation: Δ = MPI - (MPm + NPg/kg + NPgest/kgest). The iteration was performed aiming at a zero deviation between observed MPI and MP estimated by the requirements determined herein. We obtained a value of 3.88 g/EBW0.75/d for MPm. The estimation of NPg can be calculated according to the following equation: NPg = 0.716 × (EBWopen-0.308) × EBGcorrected, where EBWopen is the empty BW (kg) for non-pregnant animals and EBGcorrected is the empty body gain (kg/d) corrected for the gestational component. The k was determined as 0.347. The net protein requirements for gestation (NPgest) were determined as NPgest (g/d) = 0.0008722 × exp(0.01784 ×GD) × (calfweight/35). The efficiency of using metabolizable protein for gestation (kgest) was 0.625. It is important to highlight that different methods of MP estimates should not be mixed and that the proposed method requires the estimate of microbial protein (estimate it via urinary estimates) and might be a limitation for practical application. In conclusion, new studies should be conducted to validate our results and the methodology adopted to determine protein requirements for pregnancy in dairy cows. Due to the pattern of protein accumulation in the gestational components, we suggest that exponential model to describe protein requirements for pregnancy for dairy cows.

Effect of Parity, Body Condition Score at Calving, and Milk Yield on the Metabolic Profile of Gyr Cows in the Transition Period.

This study aimed to evaluate the effects of parity, body condition score (BCS) at calving, and milk yield on the metabolic profile of Gyr (Zebu) cows. Healthy cows in late pregnancy were grouped according to parity (primiparous, biparous, and multiparous); to BCS scale at calving (high-HBCS and normal-NBCS); and to milk yield (high-HP and moderate-MP production). BCS was assessed, and blood samples were collected on -21, -7, 0, 7, 21, and 42 days relative to parturition. The concentrations of non-esterified fatty acids (NEFA), beta-hydroxybutyrate (BHB), cholesterol, glucose, total protein (TP), albumin, total calcium (Ca), phosphorus (P), and magnesium (Mg); and activities of aspartate aminotransferase and gamma-glutamyltransferase were measured. Data were analyzed by two-way repeated measures ANOVA. The frequencies of high lipomobilization, subclinical ketosis, subclinical hypocalcemia (SCH), and the occurrence of diseases during early lactation were established. Regardless of grouping, NEFA, BHB, and cholesterol increased during early lactation; glucose showed higher values at calving; TP and albumin were higher at 21 and 42 DIM; and Ca, P, and Mg were lower at calving. Parity had little effect on the metabolic profile, HBCS did not differ from NBCS cows, and HP did not differ from MP cows in most metabolites. High lipomobilization in early lactation and SCH at calving were the most common imbalances but were not related to postpartum diseases. High-yielding Gyr cows have a balanced metabolic profile during the transition period, with few biologically relevant effects of parity, BCS at parturition, or milk yielded.

Assessment of heat production and methane emission using infrared thermography in lactating Holstein and Gyrolando-F1 (½ Holstein ½ Gyr) crossbreed cows

Infrared thermography (IRT) is a non-invasive and efficient tool to detect changes in the animal's body surface temperature, which is directly associated with the animal's energy loss. Methane emission represents a significant energy loss, particularly in ruminants, as well as heat production. Therefore, the aim of this study was to correlate skin temperature measured using IRT with heat production (HP) and methane emission in lactating Holstein and crossbred ½ Holstein x ½ Gyr (Gyrolando-F1) cows. Six Gyrolando-F1 and four Holstein cows, all primiparous, at mid lactation were used to evaluate daily HP and methane emission using indirect calorimetry in respiratory chambers. Thermographic images were taken at anus, vulva, ribs (on the right side), left flank, right flank, right front foot, upper lip, masseter and eye; IRT was performed every hour during 8 h after the morning feeding. Cows received the same diet ad libitum. Daily methane emission was positively correlated with IRT taken at the right front foot 1 h after feeding in Gyrolando-F1 cows (r = 0.85, P < 0.05) and with IRT taken at the eye 5 h after feeding in Holstein cows (r = 0.88, P < 0.05). HP was positively correlated with IRT taken at the eye 6 h after feeding in Gyrolando-F1 cows (r = 0.85, P < 0.05) and with IRT taken at the eye 5 h after feeding in Holstein cows (r = 0.90, P < 0.05). Infrared thermography was positively correlated with HP and methane emission in both Holstein and Gyrolando-F1 lactating cows, although the anatomical points and times of image acquisition yielding the greatest correlation coefficients varies among breeds.

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.

Effect of lactation on oocyte quality and in vitro embryo production of Bos indicus cows

The objective of the current study was to evaluate the effect of lactation on oocyte quality and in vitro embryo production in Gyr (Bos indicus) cows. A total of 187 multiparous cows (92 lactating and 95 non-lactating) were subjected to a single session of follicular aspiration. Follicle puncture was performed on a random day of the estrous cycle, without prior application of hormonal drugs. The reco­vered oocytes were subjected to maturation, fertilisation, and in vitro culture. The results indicated that in lactating Gyr cows had the following values of studied variables: number of follicles visualised (22.1±11.38), number of recovered oocytes (17.4±10.21), number of grade III oocytes (7.0±5.86), rate of viable oocytes (72.1±13.11%), number of blastocysts D7 (2.5±2.26) and blastocyst rate (18.3±15.61%), in relation to non-lactating cows (27.7±11.53; 21.1±10.06; 9.8±6.08, 77.4±10.08%; 4.9±3.34; 30.2±15.41%, respectively). In conclusion, the lactation period in Gyr cows affects the performance of in vitro embryo production programmes.

Nitrogen balance and microbial protein synthesis in dairy cows fed with peanut meal to replace soybean meal.

This research was carried out to evaluate the effect of replacing dietary soybean meal with peanut meal, on intake and digestibility, microbial protein synthesis, and nitrogen balance in lactating cows. Twelve crossbred Holstein × Gyr cows at 84days in milk (DIM) were distributed in a triple 4 × 4 Latin square. The treatments consisted of increasing peanut meal levels (0, 330, 670, and 1000g/kg dry matter basis) in replacement of soybean meal in the diet. Replacing soybean meal with peanut meal had no effect on the intake and digestibility of dry matter and nutrients. Nitrogen balance and percentage of retained were similar among treatments. Microbial nitrogen synthesis and microbial protein synthesis efficiency were similar among treatments. Thus, in regions where its cost is lower, peanut meal can totally replace soybean meal in dairy cow diets without affecting nitrogen balance and microbial protein synthesis.

Is maternal defensiveness of Gyr cows (Bos taurus indicus) related to parity and cows' behaviors during the peripartum period?

The maternal care of cows can influence both the milk production and the performance of their calves, making this a topic of important relevance for the production industry that uses zebu cattle. The aims of this study were to 1) investigate the effects of parity on the behaviors of Gyr cows during the peripartum period; 2) characterize the maternal defensiveness of primiparous and multiparous cows towards handlers during the first handling of their calves; and 3) evaluate the relationships between cows’ behaviors at the peripartum period and maternal defensiveness. Thirty-one Gyr cows (primiparous and multiparous), from Empresa de Pesquisa Agropecuária de Minas Gerais (Brazil), were used. The animals were placed in a maternity paddock monitored by video cameras. The behaviors of the animals were collected in four periods: Pre-calving, Post-calving, First handling of calf and Post-handling. Primiparous cows presented more pain signs, reflected in arched spine (P = 0.05), and tended to move more (P = 0.07) than the multiparous in the Pre-calving period. Trends were observed for both Maternal Composite Score (P = 0.06) and Maternal Protective Behavior score (P = 0.06), indicating that both primiparous and multiparous were protective, but only multiparous cows were aggressive toward the caretakers on the first handling of their calves. The most protective cows spent more time eating during the prepartum period (P = 0.03), while the least attentive cows spent more time lying down (P = 0.02) in the prepartum period. The cows who nursed and stimulated their calves more were also calmer (P = 0.02) and more attentive (P = 0.01). In conclusion, the peripartum behaviors of Gyr cows were related to maternal care and maternal defensiveness. Multiparous cows tended to be more aggressive than primiparous cows at the time of the first handling of their calves.

Feed intake, milk production and metabolism of Holstein, Gyr and Girolando-F1 heifers with high body condition score during the transition period

The transition period in taurine dairy cows is widely reported in the literature. However, little is known about the metabolism of zebu animals and their crossbreeding with taurine breeds during this phase. Considering the importance of these breeds in tropical and subtropical regions, this study aimed to evaluate the feed intake, milk production and hepatic metabolism in Holstein, Gyr and Girolando-F1 (½ Holstein × ½ Gyr) heifers presenting high body condition score (BCS) during the transition period (prepartum weeks −2 and −1 and postpartum weeks +1 and + 3). Twelve heifers of each genetic group were used, totaling 36 animals. Variables considered were blood metabolites related to liver function, dry matter intake (DMI), body condition score (BCS), body weight (BW), milk yield (MY), and fat and protein concentrations in milk. Gyr heifers had the lowest concentrations of paraoxonase in weeks −2 (43.13 U/mL), −1 (62.10 U/mL) and + 3 (77.89 U/mL), albumin in week −1 (3.07 g/dL), and the highest concentration of non-esterified fatty acids (NEFA) in weeks −2 (1.35 mmol/L) and −1 (1.19 mmol/L). β-hydroxybutyrate (BHB) and NEFA values were negatively correlated with prepartum DMI (−0.82 and −0.57, respectively), while paraoxonase was positively correlated to DMI (0.54). Gyr cows were more susceptible to inflammation despite having intermediate BCS and lower milk yield. Girolando-F1 animals showed the highest BCS among groups, although their hepatic metabolism had better results than Gyr cows. Holstein animals had lower lipomobilization and higher DMI and MY between breeds. These results suggest that the metabolism of zebu and crossbred cows does not react equally to the metabolism of Holstein cows concerning stress factors such as transition period and obesity. Therefore, the present study addresses an emerging theme that highlights the need for differentiated management during the transition period between the different breeds studied in order to ensure the maximum health and welfare of these animals

Replacement of soybean meal with alternative protein sources in the concentrate supplement for lactating Holstein × Gyr cows in an intensive tropical pasture-based system: Effects on performance, milk composition, and diurnal ingestive behavior

The purpose of this study was to evaluate the effects of total replacement of soybean meal (SBM) with three alternative protein sources in the concentrate supplement on performance, feed efficiency, milk composition, and diurnal ingestive behavior of Holstein × Gyr cows under an intensive system of grazing on tropical pasture. Twelve cows with 512 ± 61 kg of BW (mean ± standard deviation), 20.4 ± 4.14 kg/d of milk yield, and 86 ± 40 days in milk were distributed in a triplicated 4 × 4 Latin square design. The treatments consisted of four concentrate supplements formulated with SBM (Control), cottonseed meal (CSM), peanut meal (PM), or sunflower meal (SFM). The animals were kept in intensive rotational grazing (n = 24 paddocks) on Tanzania grass (Panicum maximum syn. Megathyrsus maximus) pasture, with 1 day of occupation per paddock and a stocking rate of 4.3 AU/ha. The daily amount of concentrate supplement offered to the cows was 1 kg DM of concentrate per 3 kg of milk produced. Fat-corrected milk yield (FCM) for the SBM group (21.1 kg/d) was similar to that of the other groups (21.5 kg/d on average); however, milk fat content and milk urea nitrogen were lower in the SBM group (36 g/kg and 12.6 mg/dL) than in the PM group (38.4 g/kg and 14.2 mg/dL). The protein source did not affect the intakes of DM (17.14 kg/d on average) and forage (9.66 kg DM/d on average). However, cows fed CSM had a lower concentrate supplement intake compared to those fed PM (7.11 vs. 7.78 kg DM/d). The lowest and the highest ether extract intake levels were observed in cows fed with SBM (0.31 kg/d) and CSM (0.39 kg/d). No effect of the protein source was detected on the time spent on grazing, rumination, and idleness, with mean values of 4.73, 2.01, and 5.26 h within a 12 h observation period (06:00–18:00 h). Soybean meal can be replaced with CSM, PM, or SFM in the concentrate supplement without affecting the FCM, feed intake, feed efficiency, and diurnal ingestive behavior of lactating Holstein × Gyr cows in an intensive tropical grazing system. The replacement of SBM with PM is recommended since the latter promotes the best results in terms of milk fat content.

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.

Modelos lineares e não lineares para a descrição da curva de lactação da raça Girolando

Abstract The objective of this work was to compare the main linear and nonlinear models used to describe lactation curves and to evaluate the nonlinearity of the nonlinear models, in order to obtain the most adequate model to describe the lactation curves of the Girolando breed. Data from 165 lactations of 89 3/4 Holstein + 1/4 Gyr cows were used, and average yield was calculated every 20 days up to 310 days of lactation. Seventeen models of lactation curves available in the literature were compared. The selection of the best model was based on the curvature measures of Bates &amp; Watts, the bias of Box, adjusted coefficient of determination, Akaike’s information criterion, and residual standard deviation. The linear model of Cobuci estimated a yield peak of 16.7 kg at 40 days of lactation, whereas the nonlinear model of Wood estimated a yield peak of 16.8 kg at 41 days of lactation and a persistence of 6.82. Nonlinearity measures were the most appropriate for selecting the most suitable nonlinear model for the description of lactation curves. To describe the lactation curves of the Girolando breed, the most suitable linear model is that of Cobuci and the nonlinear model is that of Wood.

Estimation of lactation curves of Gyr cattle and some associated production parameters in the Colombian low tropic

Background: The Gyr breed is widely used in Colombian low tropic dairy production systems. During the last 10 years, the Asociación Colombiana de Criadores de Ganado Cebú† - ASOCEBU, has been leading a dairy milk control program which led to the creation of a dataset that permits to carry out the first analysis of milk yield in Gyr cattle in the country using records from several herds. Objectives: To study milk production dynamics of Gyr cattle in the Colombian low tropic through the estimation of lactation curves and four derived production parameters: total milk yield between 5 and 305 days (TMY305), peak milk yield (PMY), days at peak (DP) and persistency (P). Methods: 13,798 daily milk yield records from 1,510 cows performing in 103 herds were used; the total number of lactations was 2,480. Four models were considered: Wood, Wiltmink, Papajcsik &amp; Bordero, and a second-degree polynomial. Mean square error, mean absolute error, mean square error of prediction, Akaike and Bayesian information criteria were used to select the model better describing each lactation using the majority rule, that is, the model selected by most criteria was the chosen one. The shape of each fitted lactation curve was checked using basic results from calculus which permitted the classification of the estimated curves into two groups: typical and atypical; only typical functions were used to compute the four aforementioned production parameters. Results: The second-order polynomial was the model most frequently selected, while the Papajcsik &amp; Bordero model had the lowest frequency. Average TMY305, PMY, DP and P were 3,489.86 kg, 17.28 kg, 57.17 days, and 0.83, respectively, with coefficients of variation: 0.27, 0.21, 0.41, and 0.16. Conclusions: This study permitted to identify individuals with outstanding phenotypic performance. To the best of our knowledge, this is the first study of this kind involving thousands of lactations from Gyr cows performing in several regions of Colombian low tropic.

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