Genetic parameters for milk yield and reproductive traits in Honduran Holstein cattle.

The aim of this study was to estimate the (co)variance components and genetic parameters for milk yield adjusted to 305d (MY305), calving-to-conception interval (CCI), number of services per conception (NSC) and calving interval (CI) of Honduran Holstein cows, by fitting a bivariate animal model using Maximum Restricted Likelihood procedures. Model included the fixed effects of calving number, the contemporary calving group (farm-season-year of calving and the cow age as covariate). The estimated means and standard deviations for MY, CCI, NSC and CI were, 5098.60 ± 1564.32 kg, 168.27 ± 104.71 days, 2.46 ± 1.69 services, and 448.73 ± 109.16 days, respectively; and their estimated heritabilities were 0.21 ± 0.05, 0.03 ± 0.028, 0.02 ± 0.024 and 0.06 ± 0.04, respectively. The genetic correlations between MY305 and CCI, NSC and CI were positive and antagonist, with values of 0.64 ± 0.52, 0.99 ± 0.56, and 0.32 ± 0.24 respectively. Even though moderate to low heritability was estimated for MY305, systematic selection for milk yield, with a reduction in reproductive efficiency, if considered as the only selection criterion is important to be considered. By including reproductive traits and considering permanent environment effects into the breeding program, might yield a slow, but constant and permanent improvement over time.

Factors Affecting the Milk Production Traits and Lactation Curve of the Indigenous River Buffalo Populations in Bangladesh.

Household buffalo dairy farming is gaining popularity nowadays in Bangladesh because of the outstanding food value of buffalo milk as well as the lower production cost of buffalo compared to cattle. An initiative has recently been taken for the genetic improvement of indigenous dairy buffaloes. The present study was carried out to determine the influence of some environmental factors like age, parity, season of calving, calving interval, dry period on the lactation yield, and lactation curve of indigenous dairy buffaloes of Bangladesh. A total of 384 indigenous dairy buffaloes from the 3rd and 4th parity of seven herds under two different agroecological zones covering four seasons were selected and ear tagged for individual buffalo milk recording. A milk yield of 300 days (MY300d) was calculated following the International Committee for Animal Recording (ICAR) and the data were evaluated using the generalized linear model (GLM). In production traits, the mean of calculated lactation period (CLP), calculated lactation yield (CLY), and milk yield of 300 days (MY300d) of the overall population were 267.28 days, 749.36 kg, and 766.92 kg, respectively, whereas calving interval (CI) and dry period (DP) as reproductive traits were 453.06 days and 185.78 days, respectively. The season of calving, age of buffalo cows, population or herd, agroecological zone, calving interval, and dry period had significant effects on production traits (p < 0.05 to p < 0.001). The season of calving, level of milk production of 300 days, population, and agroecological zone significantly affected the reproduction traits (p < 0.01 to p < 0.001). Parity was found to be non-significant for both types of traits. The average peak yield of test day (TD) milk production was highest at TD4 (4.47 kg, 98th day of lactation). The average MY300d of milk production was the highest in the Lalpur buffalo population (1076.13 kg) and the lowest in the buffalo population of Bhola (592.44 kg). The correlations between milk production traits (CLP, CLY, and MY-300d) and reproduction traits (CI and DP) were highly significant (p < 0.01 to p < 0.001). Positive and high correlation was found within milk traits and reproduction traits, but correlation was negative between milk traits and reproduction traits. Therefore, these non-genetic factors should be considered in the future for any genetic improvement program for indigenous dairy buffaloes in Bangladesh.

Evaluation of breeding objectives, breeding practices and reproductive performance of indigenous dairy cows in selected districts of Kaffa Zone, South West Ethiopia.

BACKGROUND: Breeding objectives are designed to achieve targeted dairy cow production goals, which can be affected by production type, farmer preferences, environmental factors and genetic factors individually or in combination. Breeding practices, such as both controlled and uncontrolled, and artificial insemination (AI) are the tools used to obtain the desired breeding objectives. The lower reproductive performance of indigenous dairy cows affects the total milk production and calf crops that are produced during their lifetime. Designing appropriate breeding objectives and breeding practices can improve the reproductive performance of dairy cows and their overall production performance. MATERIALS AND METHODS: The current study was conducted with the objective of evaluating the breeding, practices and performance of indigenous dairy cattle in the south western part of Ethiopia. The districts of Gesha and Chena were purposefully chosen. The study design for the 384 household surveys was a cross-sectional survey with a simple random sample approach. Data analysis was carried out by MS-Excel (2010) and the general linear model procedure of SAS of 2008. RESULTS: The current study revealed that methods of breeding were predominantly natural-controlled mating, followed by natural-uncontrolled mating and AI in descending order. Breeding objectives were input function, output function, sociocultural and economic functions and assets and security functions in decreasing order of rank. Reproduction performance indexes of indigenous dairy cows age at first service (3.72 ± 0.05 years), age at first calving (AFC) (4.71 ± 0.07 years), calving interval (CI) (1.58 ± 0.03 years), days open (DO) (4.26 ± 0.11 months), services per conception in natural mating (1.4 ± 0.08) and AI (2.73 ± 0.14), age of bull at maturity (4.17 ± 0.74 years), interoestrus interval (23.18 ± 0.61 days), calves crop (7.53 ± 0.22) and the life span of indigenous dairy cow (11.94 ± 0.26 years) were significant (p < 0.01) between two districts, whereas the values of age of bull at maturity and number of services per conception in natural mating were significant (p < 0.05) between districts. CONCLUSIONS: Using AI and major reproduction performances, such as AFC, CI and DO of indigenous dairy cows in the study area, were very low. Therefore, concerned bodies should intervene to improve reproduction performance through the utilization of AI techniques, with the integration of forage development activities and improvements in livestock health care.

A randomized study on the effect of an extended voluntary waiting period in primiparous dairy cows on fertility, health, and culling during first and second lactation.

When the voluntary waiting period (VWP), defined as the days between calving and when the cow is eligible to receive the first insemination, is extended, high-yielding dairy cows may have better opportunities to regain energy balance before first insemination. This study investigated the effect of an extended (145-215 days in milk [DIM], n = 280) or conventional (25-95 DIM, n = 251) VWP treatment on fertility, disease incidence, and culling rate in cows during their first lactation. The cows were also followed through a second lactation without intervention regarding VWP, during which the farmers could decide when they wished to start the inseminations. This was done in a randomized-controlled study on 16 high-yielding commercial herds in southern Sweden, containing a total of 531 primiparous cows of the Holstein and Red Dairy Cattle breeds. Data from the Swedish national dairy herd recording scheme collected between August 2018 and September 2021 were used in the analysis, including records on breed, calvings, estrus intensity, inseminations, disease, somatic cell count, culling date, and culling reason. During first lactation, more cows receiving the extended VWP treatment showed strong estrus intensity (score 4-5, 55% vs. 48%) and fewer showed moderate estrus intensity (score 3, 35% vs. 43%) at first insemination, compared with cows receiving the conventional VWP treatment. First service conception rate (FSCR) was higher (67% vs. 51%) and number of inseminations per conception (NINS) was lower (1.6 vs. 2.0) during the first lactation for cows receiving the extended compared with the conventional VWP treatment. For disease incidence rate or culling rate expressed as number of events per cow-time in the study, we found no differences between the cows receiving the 2 VWP treatments in any lactation. Calving to first service interval during second lactation was longer (86 vs. 74 d) for cows with extended compared with conventional VWP. In conclusion, primiparous cows with extended VWP showed improved reproductive functions, in the form of higher estrus intensity, greater FSCR, and lower NINS, during the first lactation. However, we observed no apparent effect on these fertility measures during the following lactation (without VWP intervention) and no differences in disease prevalence or culling between cows receiving the 2 different VWP treatments in either lactation. Compliance with the planned VWP treatment was lower for cows with planned extended compared with planned conventional VWP treatment. We studied the "intention-to-treat" effect (i.e., the results for all cows randomized to each treatment regardless of whether the planned VWP was achieved or not) to identify any bias arising due to degree of compliance. However, we found no difference in culling rate between cows randomized to an extended VWP compared with those randomized to a conventional VWP. These findings can be used to support management decisions on VWP length in high-yielding dairy herds.

Prolonged baleen hormone cycles suggest atypical reproductive endocrinology of female bowhead whales.

Serial measurements of hormone concentrations along baleen plates allow for reconstructions of mysticete whale reproductive histories. We assessed gestation and calving interval in bowhead whales (Balaena mysticetus) by measuring progesterone, oestradiol, corticosterone and nitrogen stable isotope ratios (δ15N) along baleen of 10 females from the eastern Canada-west Greenland population. Three immature females (body size < 14.32 m) had uniformly low progesterone concentrations across their baleen, while seven mature females (body size ≥ 14.35 m) had repeated, sustained elevations of progesterone indicative of pregnancies. The mean duration of progesterone elevations (23.6 ± 1.50 months) was considerably longer than the approximately 14 month gestation previously estimated for this species. We consider several possible explanations for this observation, including delayed implantation or sequential ovulations prior to gestation, strategies that would allow females to maximize their fitness in variable Arctic conditions, as well as suggest modified criteria defining gestation as a shorter component of the entire progesterone peak. Calving intervals varied within and among individuals (mean = 3.7 years; range = range 2.8-5.7 years), providing population-specific reproductive estimates for growth models used in bowhead whale management and conservation.

Effect of voluntary waiting period on metabolism of dairy cows during different phases of the lactation.

An extended calving interval (CInt) by extending the voluntary waiting period (VWP) could be associated with altered metabolism in dairy cows. The aim of this study was first to evaluate the effects of VWP on metabolism and body condition during the first 305 d after the first calving in the experiment (calving 1), around the end of the VWP, and during pregnancy (280 d before calving 2). Second, the effects of the VWP on metabolism were determined from 2 wk before until 6 wk after calving 2. Third, individual cow characteristics were used to predict milk production and body condition of cows after different VWP. Holstein-Friesian cows (N = 154, 41 primiparous [PP], 113 multiparous [MP]) were blocked for parity, milk production, and lactation persistency, randomly assigned to a VWP of 50, 125, or 200 d (VWP50, VWP125, or VWP200) and followed from calving 1 until 6 wk after calving 2. In the first 6 wk after calving 1 and from 2 wk before until 6 wk after calving 2, weekly plasma samples were analyzed for nonesterified fatty acids (NEFA), ß-hydroxybutyrate, glucose, insulin, and insulin-like growth factor 1 (IGF-1). From wk 7 after calving 1 until 2 wk before calving 2, insulin and IGF-1 were analyzed every 2 wk. Fat- and protein-corrected milk (FPCM) and body weight (BW) gain were measured weekly. Cows were divided in two parity classes based on calving 1 (PP and MP) and remained in these classes after calving 2. During pregnancy, MP cows in VWP200 had greater plasma insulin and IGF-1 concentration and lower FPCM compared with MP cows in VWP125 (insulin: 18.5 vs. 13.9 µU/mL, CI 13.0-19.7, P < 0.01; IGF-1: 198.5 vs. 175.3 ng/mL ± 5.3, P = 0.04; FPCM: 22.6 vs. 30.0 kg/d ± 0.8, P < 0.01) or VWP50 (insulin: 15.8 µU/mL, P < 0.01; IGF-1: 178.2 ng/mL, P < 0.01; FPCM: 26.6 kg/d, P < 0.01) and had a greater daily BW gain compared with cows in VWP50 (3.6 vs. 2.5 kg/d ± 0.2; P < 0.01). After calving 2, MP cows in VWP200 had greater plasma NEFA concentration (0.41 mmol/liter) compared with MP cows in VWP125 (0.30 mmol/liter, P = 0.04) or VWP50 (0.26 mmol/liter, P < 0.01). For PP cows, the VWP did not affect FPCM or body condition during the first lactation in the experiment, or metabolism after calving 2. Independent of the VWP, higher milk production and lower body condition before insemination were associated with higher milk production and lower body condition at the end of the lactation. Variation in these characteristics among cows could call for an individual approach for an extended VWP.

Extending the voluntary waiting period (VWP) reduces the frequency of calvings. This may benefit cow health but includes the risk of fattening and low milk yield at the end of the lactation. The aim of this study was to evaluate the effects of the VWP on metabolism and body condition during different phases of the lactation and start of the next lactation. Moreover, individual cow characteristics in early lactation were used to predict milk production and body condition of cows after different VWP. An extended VWP did not affect milk production or metabolism of primiparous cows. Multiparous cows with an extended VWP had a greater plasma insulin concentration and a lower milk production around the end of the VWP and during pregnancy, and a greater body condition during pregnancy. A higher milk production and a lower body condition before successful insemination were associated with a higher milk production and a lower body condition at the end of the lactation. Therefore, selecting multiparous cows with a higher milk production and a lower body condition for an extended lactation may reduce the risk of fattening and low milk production at the end of the lactation, while still having the benefit of a reduced frequency of calvings.

Practical Application of a Urinary Zearalenone Monitoring System for Feed Hygiene Management of a Japanese Black Cattle Breeding Herd-Relevance to Anti-Müllerian Hormone and Serum Amyloid A Clarified from a Two-Year Survey.

In this study, a herd of Japanese Black (JB) breeding cattle with sporadic reproductive disorders was continuously monitored for an additional year to assess the effects of the urinary zearalenone (ZEN) concentration and changes in parameters (AMH and SAA) with time-lag variables and herd fertility (reproductive performance). This herd had high (exceeded the Japanese dietary feed regulations) urinary ZEN and rice straw ZEN concentrations (1.34 mg/kg). Long-term data of the herd with positive ZEN exposure revealed a decreasing ZEN concentration in urine and a gradual decrease in the AMH level with age. The AMH level was significantly affected by the ZEN value 2 months earlier and the AMH level in the previous month. The changes in ZEN and SAA values were significantly affected by the ZEN and SAA values in the previous month. Additionally, calving interval data between pre-monitoring and post-monitoring showed a significantly different pattern. Furthermore, the calving interval became significantly shorter between the time of contamination (2019) and the end of the monitoring period (2022). In conclusion, the urinary ZEN monitoring system may be a valuable practical tool for screening and detecting herd contamination in the field, and acute and/or chronic ZEN contamination in dietary feeds may affect herd productivity and the fertility of breeding cows.

Estimation of the Genetic Components of (Co)variance and Preliminary Genome-Wide Association Study for Reproductive Efficiency in Retinta Beef Cattle.

In this study, we analyzed the variation of reproductive efficiency, estimated as the deviation between the optimal and real parity number of females at each stage of the cow's life, in 12,554 cows belonging to the Retinta Spanish cattle breed, using classical repeatability and random regression models. The results of the analyses using repeatability model and the random regression model suggest that reproductive efficiency is not homogeneous throughout the cow's life. The h2 estimate for this model was 0.30, while for the random regression model it increased across the parities, from 0.24 at the first calving to 0.51 at calving number 9. Additionally, we performed a preliminary genome-wide association study for this trait in a population of 252 Retinta cows genotyped using the Axiom Bovine Genotyping v3 Array. The results showed 5 SNPs significantly associated with reproductive efficiency, located in two genomic regions (BTA4 and BTA28). The functional analysis revealed the presence of 5 candidate genes located within these regions, which were previously involved in different aspects related to fertility in cattle and mice models. This new information could give us a better understanding of the genetic architecture of reproductive traits in this species, as well as allow us to accurately select more fertile cows.

A randomized study on the effect of extended voluntary waiting period in primiparous dairy cows on milk yield during first and second lactation.

Extending the voluntary waiting period (VWP) for primiparous cows can have a positive impact on fertility without a negative impact on milk production per day in the calving interval (CInt). We investigated the effect of extended VWP during first lactation on milk yield (MY) during 2 consecutive lactations in primiparous cows. The study involved 16 commercial herds in southern Sweden. A total of 533 Holstein and Red dairy cattle (Swedish Red, Danish Red, Ayrshire) dairy cows were randomly assigned to a conventional 25 to 95 d VWP (n = 252) or extended 145 to 215 d VWP (n = 281). Data on calvings, inseminations, and test-day yields were retrieved from the Swedish Milk Recording System. Cows with VWP according to plan and completing 1 or 2 CInt with a second or third calving were included in the data analysis. Whole lactation and 305-d energy-corrected milk (ECM) yield were higher for the extended VWP group than the conventional VWP group in both the first lactation (12,307 vs. 9,587 and 9,653 vs. 9,127 kg ECM) and second lactation (12,817 vs. 11,986 and 11,957 vs. 11,304 kg ECM). We found no difference between the VWP groups in MY per day during the first CInt or during the first and second CInt combined, although MY per day during the second CInt was around 1.5 kg higher for cows with extended VWP than for cows with conventional VWP. Thus extended VWP for primiparous cows can be used as a management tool without compromising MY.

Hormone use for reproductive diseases and heat induction in relation to herd-level reproductive performance in Dutch dairy farms.

This ecological study aimed to associate hormone use for reproductive diseases and heat induction with reproductive performance at herd level. Hormone use, herd characteristics, and test-day recording data were obtained from 754 representative Dutch dairy farms belonging to five large veterinary practices from 2017 to 2019 (1679 observations in total). Hormone use was classified into prostaglandin, gonadotropin-releasing hormone (GnRH), and progesterone, and was expressed at herd level as the annual number of hormone doses per 100 adult dairy cows. Hormone use was categorized into four levels (no usage, low, medium, and high use), following the 33rd and 66th percentiles of herds that applied them. Three herd-level reproductive performance indicators (calving interval, calving-to-1st insemination interval, number of inseminations per cow) were analyzed using multivariable General Estimating Equations models. The median annual total hormone use was 36.1 (mean=43.1; min=0.0; max=248.2) doses per 100 adult dairy cows in all herds while the median was 39.2 (mean=46.8; min=0.4; max=248.2) doses per 100 adult dairy cows among the user-herds. The median annual group-specific hormone use was 21.3 (mean=26.1; min 0.0; max=180.0), 11.0 (mean=15.3; min=0.0; max=127.0) and 0.0 (mean=1.8; min=0.0; max=40.3) doses per 100 adult dairy cows for prostaglandin, GnRH, and progesterone, respectively. The final statistical models identified that herds with a high hormone use had a calving interval and a calving-to-1st insemination interval that was 9.3 ± 2.6 and 16.4 ± 2.1 days shorter than that of non-user herds (424.0 ± 2.7 and 114.0 ± 2.1 days), respectively. Furthermore, high-user herds needed on average 0.3 ± 0.04 inseminations more to get their cows pregnant compared to non-user herds (1.83 ± 0.04 no. of inseminations per cow). Medium-user herds had a 6.5 ± 2.6 days shorter calving interval and a 12.0 ± 2.1 days shorter calving-to-1st insemination interval with 0.2 ± 0.04 additional inseminations per cow compared to non-user herds. Low-user herds had a 6.2 ± 2.7 days shorter calving interval and a 7.9 ± 2.2 days shorter calving-to-1st insemination interval compared to non-user herds. The model produced the same trend for prostaglandin and GnRH use, with the higher use being associated with a shorter calving interval, a shorter calving-to-1st insemination interval, and a higher insemination per cow number. For progesterone use the opposite effect was observed. In conclusion, using a large representative herd-level dataset, hormone use was associated with a better reproductive performance in terms of calving interval and calving-to-1st insemination interval but gave extra average number of inseminations per cow. It should be monitored how reproduction performance changes when striving for a more prudent hormone use.

Effect of the percentage of Bos taurus inheritance on the fertility of Holstein×Zebu and Brown Swiss×Zebu cows in the Mexican tropics

Background: No dairy breed or crossbreed has superior overall performance in all environments; therefore, it is necessary to determine which crossbreed is the most suitable for the Mexican tropic and what proportion of European breed is optimum for reproduction. Objective: To assess the effect of the proportion of Bos taurus (Bt) genes on reproductive performance of Holstein×Zebu (HZ) and Brown Swiss×Zebu (BZ) cows, and compare reproductive performance of these genotypes in a dual- purpose production system. Methods: Cows were maintained in a rotational grazing system on African star grass (Cynodon plectostachyus) in Veracruz, Mexico. Cows were milked twice daily. Calves were kept tied to the side of their dams while the cows were milked. Results: The percentage of Bt genes did not affect (p>0.05) fertility traits (age at first calving, days to first service after calving, services per conception, conception rate at first service, days open until conception, gestation length, and calving interval) of BZ cows. In contrast, HZ cows with less than 75% Holstein (H) genes were 0.3 years younger (p<0.05) at first calving and had 39.8 fewer days open (p<0.05) than HZ cows with 75% H genes or more. In addition, the calving interval of HZ cows with less than 75% H genes was 44.8 days shorter (p<0.05) than that of HZ cows with 75% H genes or more. The HZ cows had five fewer days pregnant and were 22.8 kg heavier at calving (p<0.05) than BZ cows. Conclusions: The effect of the percentage of Bt genes on cow fertility depends on the dairy breed used. In general, BZ and HZ cows present similar reproductive performance.

Antecedentes: Ninguna raza lechera o cruce tiene un desempeño general superior en todos los ambientes; por lo tanto, es necesario determinar cuál cruce lechero es más apropiado en el trópico mexicano y qué proporción de raza europea es óptima para la reproducción. Objetivo: Evaluar el efecto de la proporción de genes Bos taurus (Bt) en el desempeño reproductivo de vacas cruzadas Holstein×Cebú (HC) y Pardo Suizo×Cebú (PC), y comparar el desempeño reproductivo de estos dos genotipos en un sistema de producción doble propósito. Métodos: Las vacas se mantuvieron en un sistema de pastoreo rotacional en zacate Estrella de África (Cynodon plectostachyus) en Veracruz, México. Las vacas se ordeñaron dos veces al día. Los becerros se mantuvieron atados, a un costado de sus madres mientras éstas se ordeñaron. Resultados: El porcentaje de genes Bt no afectó (p>0,05) ninguna característica de fertilidad (edad a primer parto, días a primer servicio después del parto, servicios por concepción, tasa de preñez a primer servicio, días abiertos a la concepción, duración de la gestación, e intervalo entre partos) de las vacas PC. En contraste, las vacas HC con menos de 75% de genes Holstein (H) fueron 0,3 años más jóvenes (p<0,05) al primer parto y tuvieron 39,8 días abiertos menos (p<0,05) que las vacas HC con 75% de genes H o más. Además, el intervalo entre partos de las vacas HC con menos de 75% de genes H fue 44,8 días más corto (p<0,05) que el de las vacas HC con 75% de genes H o más. Las vacas HC tuvieron cinco días de gestación menos y fueron 22,8 kg más pesadas al parto (p<0,05) que las PC. Conclusiones: El efecto del porcentaje de genes Bt sobre la fertilidad de la vaca depende de la raza lechera usada. En general, las vacas PC y HC tienen similar desempeño reproductivo.

Antecedentes: Nenhuma raça ou cruza leiteira tem desempenho geral superior em todos os ambientes; portanto, é necessário determinar qual cruza leiteira é mais apropriada no trópico mexicano e qual proporção da raça europeia é ideal para a reprodução das vacas. Objetivo: Avaliar o efeito da proporção de genes Bos taurus (Bt) no desempenho reprodutivo de vacas Holandês×Zebu (HZ) e Pardo Suíço×Zebu (PZ), e comparar o desempenho reprodutivo desses dois genótipos em sistema de produção de dupla aptidão. Métodos: As vacas foram mantidas em sistema de pastoreio rotacional em capim Estrela de África (Cynodon plectostachyus) em Veracruz, México. As vacas foram ordenhadas duas vezes por dia. Os bezerros foram mantidos ao lado de suas mães enquanto eram ordenhadas. Resultados: A porcentagem dos genes Bt não afetou (p>0,05) nenhuma característica de fertilidade (idade ao primeiro parto, número de dias para o primeiro serviço pós-parto, serviços por concepção, taxa de prenhes no primeiro serviço, dias abertos, período de gestação e intervalo entre partos) das vacas PZ. Em contraste, vacas HC com menos de 75% dos genes Holandês (H) eram 0,3 anos mais jovens (p<0,05) no primeiro parto e tiveram 39,8 dias abertos a menos (p<0,05) do que as vacas HZ com 75% ou mais dos genes H. Além disso, o intervalo de parto das vacas HZ com menos de 75% dos genes H foram 44,8 dias mais curtos (p<0,05) do que as vacas HZ com 75% ou mais de genes H. As vacas HZ tiveram cinco dias de gestação a menos e foram 22,8 kg mais pesadas no parto (p<0,05) do que as PZ. Conclusões: O efeito da porcentagem de genes Bt na fertilidade da vaca dependeu da raça leiteira utilizada. Em geral, as vacas PZ e HZ tiveram desempenho reprodutivo semelhante.

Population genetic features of calving interval of the Limousin beef cattle breed in Hungary.

Variance, covariance components, heritability, breeding values (BV) and genetic trends in calving interval (CI) of the Limousin population in Hungary were evaluated. A total of 3,008 CI data of 779 cows from three herds in 1996-2016 were processed. For influencing effects GLM method, for population genetic parameters and BV estimation BLUP animal model, for trend analyses linear regression was applied. The average CI obtained was 378.8 ± 3.1 days. The variance distribution components of the phenotype were as follow: age of cow at calving 34.30%, season of calving 26.09%, year of calving 23.00%, sire 7.45%, herd 3.23%, sex of calf 0.33% and type of calving 0.30%. The heritability of CI proved to be low (h2 d = 0.04 ± 0.02 and 0.03 ± 0.02; h2 m = 0.01 ± 0.02). The repeatability was low (R = 0.03 ± 0.02). Based on the phenotypic trend calculation, the CI of cows decreased by an average of 0.60 days per year (R 2 = 0.19; P < 0.05). In case of genetic trend calculation, the average BV of sires in CI increased 0.07 and 0.17 days per year (R 2 = 0.23 and 0.27; P < 0.05).

Revenues and costs of dairy cows with different voluntary waiting periods based on data of a randomized control trial.

Based on modeling studies, a 1-yr calving interval for dairy cows is generally considered optimal from an economic point of view. Recently some dairy farmers are deliberately extending the voluntary waiting period for insemination (VWP) to extend the calving interval. Reasons to extend the VWP are to reduce the frequency of transitions such as dry-off and calving to improve health, to reduce labor associated with these transitions, and to reduce the number of surplus calves. This study aimed to evaluate yearly revenues, yearly costs, and yearly net partial cash flow (NPCF) for individual cows with a VWP of 50, 125, or 200 d based on data from a randomized control trial. The NPCF included revenues and costs for milk yield, calves born, inseminations, concentrate supply, partial mixed ration (PMR) supply, veterinary treatments, discarded milk due to veterinary treatments, culling, and labor (for milking, calving cows, inseminations, and veterinary treatments). Holstein-Friesian dairy cows (n = 153) within one herd were blocked for parity, calving season, and expected (primiparous cows) or previous (multiparous cows) 305-d milk yield. Cows were randomly assigned within the blocks to 1 of 3 VWP (VWP50, VWP125, or VWP200) in wk 6 after calving, and monitored from wk 6 after calving until wk 6 after the next calving or until culling. Revenues and costs were calculated per individual cow and expressed per cow per year. Revenues from milk and costs for PMR and concentrate contributed most to the yearly NPCF. Total yearly revenues were greater in VWP50 compared with VWP200 (€3,169 vs. €2,832), mainly because of €334 greater milk revenues. Total yearly costs were also greater in VWP50 compared with VWP200 (€1,964 vs. €1,729), mainly because of €102 greater concentrate costs. The VWP was not significantly associated with the NPCF per cow per year. A change in milk, feed, or calf price, or a change in labor costs for calving cows or for inseminations had a greater effect on the yearly NPCF of cows in VWP50 compared with cows in VWP200. To investigate variation in NPCF, cows were grouped for yearly NPCF and categorized into 3 economic classes (EC): EC1 (<€1,100/yr), EC2 (€1,100-€1,400/yr), and EC3 (>€1,400/yr). Cows in EC3 had greatest lactation production per day in the experiment (i.e., kg of milk, protein, fat, lactose), and lowest number of veterinary treatments during the experiment.

Effect of the rob(1;29) translocation on the fertility of beef cattle reared under extensive conditions: A 30-year retrospective study.

The Robertsonian translocation 1/29 (rob(1;29)) is the most worldwide widespread chromosomal abnormality in domestic animals. Previous studies have demonstrated its negative effect on fertility in dairy herds, but not in beef cattle extensively bred. In this study, we analysed the effect of rob(1;29) in a Retinta cattle breed data set gathered during the last 30 years. The data presented herein include rob(1;29) analysis of 11,505 cows from 251 herds, pedigree information of 24,790 animals and 67,457 calving records. Fertility was evaluated using estimated breeding values for the reproductive efficiency (Re), calculated as the percentage ratio between the number of calvings of an individual and the number expected in an optimal situation. Our results showed that cows carrying the heterozygote genotype showed a significant decrease in their Re (-5.10%, p < .001). No decrease was detected in free rob(1;29) animals and homozygous carriers. In addition, the incidence of rob(1;29) in the breed fertility was decreased to very low values after 30 years of avoiding selection of bulls' carrier as stallions. The effect of rob(1;29) on cattle fertility is only significant when the prevalence of carrier individuals is high. Selecting against the disease only by the paternal side reduced the incidence to negligible values.

[Impact of lameness on fertility traits in Austrian Fleckvieh cows - results from the Efficient-Cow-project]. / Auswirkung von Lahmheit auf Fruchtbarkeits­merkmale bei Fleck­vieh-Kühen in Österreich ­ Ergebnisse aus dem Efficient-Cow-Projekt.

INTRODUCTION: The impact of lameness on fertility in dairy cows has already been investigated, however predominantely in Holstein cows. The aim of this study was to evaluate the impact of lameness during the dry period, between calving and first service and between calving and conception (days open) on selected fertility traits in Austrian Fleckvieh cows. Locomotion scoring of dairy cows was performed during the course of routine performance testing in 2014 and 2015. Using the observed maximum locomotion score (MLSC) during pre- and postcalving periods, the cows were classified into three groups: cows never lame (MLSC 1), cows that showed MLSC 2, and cows with MLSC ≥3 during these defined periods. Data sets of 3,998 lactations of 3,058 Austrian Fleckvieh cows from 97 dairy herds could be evaluated. In several statistical models the fixed effects of MLSC (1, 2, ≥ 3), farm, year and season of calving, parity*age class at calving, and early fertility disorders were considered for analysis of the traits days from calving to first insemination, interval from first to last insemination, days from calving to conception and calving interval (CI), as well as the non-return-rate90 (NRR90). Mean lameness prevalence during the dry period was 19,43 %, and reached 27,70 % in the period between calving and conception. Lameness (MLSC ≥ 3) during the dry period significantly (P = 0,030) prolonged the period between calving and conception, and lameness (MLSC ≥ 3) during the period from calving to first service had a significantly detrimental effect on the periods calving to first insemination, days open and CI (P < 0,001). Further, highly significant associations (P < 0,001) in cows showing MLSC ≥ 2 during the period between calving and conception on all fertility traits were determined. Apart from lameness, farm, year and season of calving, parity*-age class at calving, early fertility disorders and, partly, the interaction of the latter two effects significantly (P.

INTRODUCTION: L'impact de la boiterie sur la fertilité chez les vaches laitières a déjà été étudié, mais principalement chez les vaches Holstein. Le but de cette étude était d'évaluer l'impact de la boiterie pendant la période de tarissement, entre le vêlage et la première saillie et entre le vêlage et la conception (« days open ¼) sur certains indices de fertilité chez les vaches autrichiennes Fleckvieh. La notation de la locomotion des vaches laitières a été effectuée au cours des tests de performance de routine en 2014 et 2015. À l'aide de la note de locomotion maximale observée (MLSC) pendant les périodes de pré-vêlage et de post-vêlage, les vaches ont été classées en trois groupes : vaches jamais boiteuses (MLSC 1), vaches ayant montré un MLSC 2 et les vaches avec MLSC ≥3 pendant ces périodes définies. Des ensembles de données de 3 998 lactations de 3 058 vaches autrichiennes Fleckvieh de 97 troupeaux laitiers ont pu être évalués. Dans plusieurs modèles statistiques, les effets fixes de la MLSC (1, 2, ≥ 3), de l'exploitation, de l'année et de la saison de vêlage, de la classe d'âge au vêlage et des troubles de la fertilité précoce ont été pris en compte pour l'analyse des caractéristiques de fertilité : jours du vêlage à la première insémination, intervalle de la première à la dernière insémination, jours du vêlage à la conception et intervalle de vêlage (IC), ainsi que taux de non-retour90 (NRR90). La prévalence moyenne de boiterie pendant la période sèche était de 19,43 % et atteignait 27,70 % entre le vêlage et la conception. La boiterie (MLSC 3) pendant la période tarie (P = 0,030) prolongeait significativement la période entre le vêlage et la conception et la boiterie (MLSC ≥ 3) pendant la période allant du vêlage à la première insémination avait un effet significativement néfaste sur les périodes vêlage-première insémination, « days open ¼ et IC (P < 0,001). De plus, des associations hautement significatives (P < 0,001) chez les vaches présentant une MLSC 2 pendant la période entre le vêlage et la conception sur tous les traits de fertilité ont été relevées. Hormis la boiterie, l'exploitation, l'année et la saison de vêlage, la classe d'âge au vêlage, les troubles de la fertilité précoce et, en partie, l'interaction de ces deux derniers effets a affecté de manière significative (P < 0,05) à très significative (P < 0,001) les caractères de fertilité étudiés. Des associations négatives significatives sur certains caractères de fertilité uniques et tous ceux étudiés ont été évaluées chez des vaches souffrant de MLSC ≥ 2, et en particulier de MLSC ≥ 3, pendant trois périodes définies avant et après le vêlage. La prévention ou la réduction de la boiterie chez les vaches présentant une MLSC2 pendant la période de tarissement et de « days open ¼ aurait probablement un effet bénéfique significatif sur la fertilité et le bien-être des vaches laitières.

Effects of dietary starch content and body condition score at calving on reproductive parameters in Holstein dairy cows.

Nutritional modifications can potentially impact the reproductive performance and ultimately the economic results of dairy herds. The objectives were to investigate the effects of feeding a high starch (HS) diet and body condition score (BCS) at calving on reproductive responses and uterine health in Holstein dairy cows. One hundred seventy-four multiparous cows were randomly assigned to 1 of 2 experimental diets from 16 until 50 days in milk (DIM; n = 87 per group); normal starch (228 g/kg diet DM; NS) or high starch (270 g/kg diet DM; HS) diets. Each dietary treatment group was further subdivided based on BCS at calving as normal BCS (BCS ≤ 3.5; NBCS; n = 45) and high BCS (BCS ≥ 3.75; HBCS; n = 42). Transrectal ultrasonography was carried out at 10 DIM, and thereafter twice weekly until the onset of ovarian cyclicity or d 50 DIM. Feeding HS diet significantly affected the proportion of cows cycling by 30 and 40 DIM. Number of services per conception and calving interval (CI) were significantly improved in cows fed the HS compared to the NS diet (2.08 vs. 2.51 and 427.14 vs. 445.30 days for cows fed HS and NS diets, respectively). In summary, feeding higher starch diets from 16 till 50 DIM could be an effective strategy to improve the economic variables related to reproduction in dairy cows.

Genetic relationship of age at first calving with conformation traits and calving interval in Hanwoo cows.

This study was performed to investigate genetic relationship of age at first calving (AFC) with body development and reproduction capacity in female Hanwoo. The data sets of 52,299 reproduction records of 19,566 heads calved from 2011 to 2019 and conformation records of 19565 heads born from 1997 to 2017 were analyzed by separating them based on age at first calving. In the analysis, conformation traits included the body condition score (BCS), height (HT), body width (BW), hip bone length (HL), hip bone width (HW), and final score (FS). The heritability and genetic correlation of AFC with conformation traits and calving interval (CI) were analyzed. The heritability for AFC was 0.716, 0.087, and 0.097 for the before and after 24 months and combined data, respectively. The genetic correlation of AFC before 24 months with BCS was -0.778, -0.600 with BW, and 0.442 with HT. The genetic correlation of AFC after 24 months with HT was -0.826, -0.706 with BW, -0.623 with HL, -0.456 with HW, and -0.675 with FS. When the first calving age of young heifers approached 24 months, BCS and BW decreased, and HT increased. When first calving is delayed to after 24 months, the conformation traits become smaller, which indicates that conformation to some extent affects the delay in AFC. The genetic correlation between CI and AFC was -0.116, 0.307, and 0.250 for the before and after 24 month of AFC and combined data, respectively. When first calving date approached 24 months, CI was reduced. The obtained results suggest that it is important that first calving occurs at an appropriate age. Additional research is needed to perform proper genetic evaluation of first calving age in Hanwoo cattle in Korea.

Comparison of reproductive performance of AI- and natural service-sired beef females under commercial management.

The objective of this study was to assess differences in reproductive performance of natural service and artificial insemination (AI) sired beef females based on pregnancy outcomes, age at first calving, and calving interval. Data were sourced from 8,938 cows sired by AI bulls and 3,320 cows sired by natural service bulls between 2010 and 2017. All cows were in a commercial Angus herd with 17 management units located throughout Virginia and represented spring and fall calving seasons. All calves were born to dams managed with estrus synchronization. Pregnancy was analyzed with generalized linear mixed models and other reproductive measures with linear mixed models in R. Six models were evaluated with the dependent variables of pregnancy status at the first diagnosis, pregnancy status at the second diagnosis, pregnancy type (AI or natural service) at the first diagnosis, pregnancy type at the second diagnosis, calving interval, and age at first calving. Independent variables differed by model but included sire type of the female (AI or natural service), prebreeding measures of age, weight, and body condition score, postpartum interval, sex of the calf nursing the cow, and management group. No differences were observed between AI- and natural service-sired females based on pregnancy status at first and second pregnancy diagnosis (P > 0.05). Sire type was only found to be significant for age at first calving (P < 0.05) with AI-sired females being 26.6 ± 1.6 d older at their first calving, which was expected because AI-sired females were born early in the calving season making them older at breeding. Surprisingly, age and body condition score were not significant predictors of pregnancy (P > 0.05). Body weight at breeding was not significant for pregnancy (P > 0.05) but was significant for age at first calving (P < 0.05). These data suggested that lighter heifers calved earlier which contradicts our original hypothesis. Overall, commercial Angus females sired by AI or natural service bulls had similar reproductive performance. Factors that were commonly associated with reproductive success were not significant in this commercial Angus herd managed with estrus synchronization. Given the size of these data, the importance of body condition, age, and weight should be reassessed in modern genetics and management practices.

The effect of new bovine viral diarrhea virus introduction on somatic cell count, calving interval, culling, and calf mortality of dairy herds in the Dutch bovine viral diarrhea virus-free program.

Bovine viral diarrhea virus (BVDV) infection has a major effect on the health of cows and consequently on herd performance. Many countries have implemented control or eradication programs to mitigate BVDV infection and its negative effects. These negative effects of BVDV infection on dairy herds are well documented, but there is much less information about the effects of new introduction of BVDV on dairy herds already participating in a BVDV control program. The objective of our study was to investigate the effect of a new BVDV introduction in BVDV-free herds participating in the Dutch BVDV-free program on herd performance. Longitudinal herd-level surveillance data were combined with herd information data to create 4 unique data sets, including a monthly test-day somatic cell count (SCC) data set, annual calving interval (CIV) and culling risk (CR) data sets, and a quarterly calf mortality rate (CMR) data set. Each database contained 2 types of herds: herds that remained BVDV free during the whole study period (defined as free herds), and herds that lost their BVDV-free status during the study period (defined as breakdown herds). The date of losing the BVDV-free status was defined as breakdown date. To compare breakdown herds with free herds, a random breakdown date was artificially generated for free herds by simple random sampling from the distribution of the breakdown month of the breakdown herds. The SCC and CIV before and after a new introduction of BVDV were compared through linear mixed-effects models with a Gaussian distribution, and the CR and CMR were modeled using a negative binomial distribution in generalized linear mixed-effects models. The explanatory variables for all models included herd type, BVDV status, year, and a random herd effect. Herd size was included as an explanatory variable in the SCC, CIV, and CMR model. Season was included as an explanatory variable in the SCC and CMR model. Results showed that free herds have lower SCC, CR, CMR, and shorter CIV than the breakdown herds. Within the breakdown herds, the new BVDV introduction affected the SCC and CMR. In the year after BVDV introduction, the SCC was higher than that in the year before BVDV introduction, with a factor of 1.011 [2.5th to 97.5th percentile (95% PCTL): 1.002, 1.020]. Compared with the year before BVDV breakdown, the CMR in the year of breakdown and the year after breakdown was higher, with factors of 1.170 (95% PCTL: 1.120; 1.218) and 1.096 (95% PCTL: 1.048; 1.153), respectively. This study reveals that a new introduction of BVDV had a negative but on average relatively small effect on herd performance in herds participating in a BVDV control program.

Relationship between calving interval and profitability of Brown Swiss cows in a subtropical region of Mexico.

Brown Swiss cattle have replaced Zebus in some dual-purpose farms in tropical and subtropical regions of Mexico, under extensive grazing management. There is limited information about the productive and reproductive performance of this breed under tropical conditions; the lack of records from small farms may be the main reason. The objectives of the study were to evaluate the relationship between calving interval (CI) and milk and beef (weaned male calves) profit in Brown Swiss cows from a dual-purpose farm under extensive management in a subtropical region of Mexico. Data from 156 cows calving from 2000 to 2014 were analysed with both a linear and a survival model. Mean CI was 438 ± 49 days, mean age at first calving was 40 ± 6 months and length of productive life was 7 ± 3 years. The effects of parity, calving year and calving season were significantly related to CI (P < 0.05), whereas the effect of calf sex was not. Cows calving in the autumn and winter had shorter calving intervals, probably because supplements received during the dry season months improved energy balance. The highest culling rate was 28% at 45 months of age. Milk yield and total profit increased as CI increased from 12 to 20 months; beef contribution to total profit decreased as CI and milk yield increased. Calving intervals of more than 12 and up to 20 months had a positive effect on the milk production and profitability of dual-purpose cows in a subtropical region of Mexico.