Service sire has been recognized as an important factor affecting dairy herd fertility. Our group has reported promising results on gene mapping and genomic prediction of dairy bull fertility using autosomal SNP markers. Little is known, however, about the genetic contribution of sex chromosomes, which are enriched in genes related to sexual development and reproduction. As such, the main goal of this study was to investigate the effect of SNP markers on X and Y chromosomes (BTAX and BTAY, respectively) on sire conception rate (SCR) in US Holstein bulls. The analysis included a total of 5,014 bulls with SCR records and genotypes for roughly 291k SNP located on the autosomes, 1.5k SNP located on the pseudoautosomal region (PAR), 13.7k BTAX-specific SNP, and 24 BTAY-specific SNP. We first performed genomic scans of the sex chromosomes, and then we evaluated the genomic prediction of SCR including BTAX SNP markers in the predictive models. Two markers located on PAR and 3 markers located on the X-specific region showed significant associations with sire fertility. Interestingly, these regions harbor genes, such as FAM9B, TBL1X, and PIH1D3, that are directly implicated in testosterone concentration, spermatogenesis, and sperm motility. On the other hand, BTAY showed very low genetic variability, and none of the segregating markers were associated with SCR. Notably, model predictive ability was largely improved by including BTAX markers. Indeed, the combination of autosomal with BTAX SNP delivered predictive correlations around 0.343, representing an increase in accuracy of about 7.5% compared with the standard whole autosomal genome approach. Overall, this study provides evidence of the importance of both PAR and X-specific regions in male fertility in dairy cattle. These findings may help to improve conception rates in dairy herds through accurate genome-guided decisions on bull fertility.

Milk fever is an important metabolic disorder that affects dairy cows around parturition. It is associated with a breakdown in the mechanisms of calcium homeostasis, resulting in very low blood calcium levels (hypocalcemia). The main objective of this study was to dissect the genetic basis underlying milk fever incidence in Holstein cattle. Data consisted of 31.6 k producer-recorded lactation incidence records from 15.3 k cows. The analysis included a whole-genome scan and a subsequent gene-set analysis in order to reveal individual genes, genetic mechanisms and biological pathways implicated in the incidence of periparturient hypocalcemia. The association analysis identified at least eight different genomic regions that explain considerable amounts of additive genetic variance for milk fever incidence. Notably, some of these regions harbor genes, such as CYP27A1, CYP2J2, GC, SNAI2, and PIM1, that are directly involved in vitamin D metabolic pathway. Moreover, the gene-set analysis revealed several functional terms, such as calcium ion binding, calcium ion transportation, T cell differentiation, B cell activation, protein phosphorylation, apoptosis, and protein kinase activity, among others, that could be implicated in the development of periparturient hypocalcemia. Overall, this comprehensive study contributes to a better understanding of the genetic control of this complex disease. In addition, these findings may contribute to the development of novel breeding strategies for reducing the incidence of milk fever in dairy cattle.

Dairy bull fertility is traditionally evaluated using semen production and quality traits; however, these attributes explain only part of the differences observed in fertility among bulls. Alternatively, bull fertility can be directly evaluated using cow field data. The main objective of this study was to investigate bull fertility in the Italian Brown Swiss dairy cattle population using confirmed pregnancy records. The data set included a total of 397,926 breeding records from 1,228 bulls and 129,858 lactating cows between first and fifth lactation from 2000 to 2019. We first evaluated cow pregnancy success, including factors related to the bull under evaluation, such as bull age, bull inbreeding, and AI organization, and factors associated with the cow that receives the dose of semen, including herd-year-season, cow age, parity, and milk yield. We then estimated sire conception rate using only factors related to the bull. Model predictive ability was evaluated using 10-fold cross-validation with 10 replicates. Interestingly, our analyses revealed that there is a substantial variation in conception rate among Brown Swiss bulls, with more than 20% conception rate difference between highfertility and low-fertility bulls. We also showed that the prediction of bull fertility is feasible as our cross-validation analyses achieved predictive correlations equal to 0.30 for sire conception rate. Improving reproduction performance is one of the major challenges of the dairy industry worldwide, and for this, it is essential to have accurate predictions of service sire fertility. This study represents the foundation for the development of novel tools that will allow dairy producers, breeders, and artificial insemination companies to make enhanced management and selection decisions on Brown Swiss male fertility.

RESUMO:Avaliou-se os efeitos de meio sobre a contagem bacteriana total (CBT) e logarítmico da contagem bacteriana total (logCBT) de amostras de tanque individuais, comunitário e latões coletadas pelas indústrias, analisadas pelo Laboratório da Qualidade do Leite (LQL) ). Resultados evidenciam a necessidade pelos produtores, técnicos e indústrias de reavaliarem seus procedimentos de higiene dos equipamentos de ordenha, resfriamento, temperatura e tempo de armazenagem do leite, melhorando a qualidade microbiológica do leite. Palavras-chave: ano de análise; escore da contagem de células somáticas; idade da amostra; mês de análise; região de análise ABSTRACT:. The effects of environment on total bacterial count (TBC) and logarithmic of total bacterial count (logCBT) of individual tank samples, community and cans collected by industries, analyzed by the Milk Quality Laboratory (LQL) the Paranaense Association Cattle breeders of Holstein (APCBRH) -Curitiba, PR were evaluated. Were analyzed 680 102 milk samples from January 2012 to May 2014 in ten regions. The estimated averages, standard deviation and coefficient of variation for CBT, logCBT and sample age were 1,307,000 ± 1.859 million (CFU / mL), 136.7%; 5.89 ± 1.93 (log10UFCxmL-1), 29.5% ± 1.48 and 2.95 days, respectively. The effects included in the mathematical model influenced significantly (p <0.01) the variables studied. Lower values for logCBT occurred in late winter and spring (ranging from 5.36 and 5.47 (log10UFCxmL-1)). Over the years, there was a decrease in values (5.66 to 5.51 (log10UFCxmL-1)). The region significantly influenced the logCBT (p <0.01), recording the lowest average of 3.64 in Campo Mourao and the highest 6.44 (log10UFCxmL-1) in the Metropolitan of Curitiba, justified by different levels of technologies adopted in differents regions. The score of Somatic Cell Count (ECS) influenced significantly (p <0.01) the CBT and the logCBT. When the age of the sample varied from zero to two days logCBT increased from 5.46 to 5.66 (x log10 CFU ml-1) and from three to seven days decreased from 5.66 to 5.57 (x log10 CFU ml-1). Results show the need for producers, technicians and industry reassess their hygiene procedures of milking equipment, cooling, temperature and milk storage time, improving the microbiological quality of milk.

Summary Bull fertility is a key factor for successful reproductive performance in dairy cattle. Since the semen from a single bull can be used to inseminate hundreds of cows, one subfertile bull could have a major impact on herd reproductive efficiency. We have previously identified five genomic regions, located on BTA8 (72.2 Mb), BTA9 (43.7 Mb), BTA13 (60.2 Mb), BTA17 (63.3 Mb), and BTA27 (34.7 Mb), that show large dominance effects on bull fertility. Each of these regions explained about 5–8% of the observed differences in sire conception rate between Holstein bulls. Here, we aimed to identify candidate causal variants responsible for this variation using targeted sequencing (10 Mb per region). For each genomic region, two DNA pools were constructed from n≈20 high‐fertility and n≈20 low‐fertility Holstein bulls. The DNA‐sequencing analysis included reads quality control (using FastQC), genome alignment (using BWA and ARS‐UCD1.2), variant calling (using GATK) and variant annotation (using Ensembl). The sequencing depth per pool varied from 39× to 51×. We identified a set of nonsense mutations, missense mutations, and frameshift variants carried by low‐fertility bulls. Notably, some of these variants were classified as strong candidate causal variants, i.e., mutations with deleterious effects located on genes exclusively/highly expressed in testis. Genes affected by these candidate causal variants include AK9, TTLL9, TCHP, and FOXN4. These results could aid in the development of novel genomic tools that allow early detection and culling of subfertile bull calves.

Avaliou-se os efeitos de meio com destaque para escore da contagem de células somáticas (ECS) sobre a contagem bacteriana total (CBT) e logarítmico da contagem bacteriana total (logCBT) de 685.032 amostras refrigeradas de leite de tanques individuais, comunitários e latões, coletadas pelas indústrias de laticínios em propriedades localizadas em dez regiões no Estado do Paraná, analisadas no período de janeiro de 2012 a maio de 2014. As médias estimadas, desvios-padrão e coeficientes de variação foram: CBT (1.307.000 ± 1.859.000 (UFC/mL), 136,7%); logCBT (5,89 ± 1,93 (log10UFCxmL-1), 29,5%); CCS (568 ± 575 (x1.000 células/mL) 96,10%); ECS (4,95 ± 1,36, 30,06%) e idade da amostra (2,95 ± 1,48 dias), respectivamente. O Escore da Contagem de Células Somáticas (ECS) influenciou significativamente (P<0,01) a CBT e o logCBT. Os coeficientes de correlação de Pearson obtidos entre a CBT, logCBT e o ECS, foram de magnitude média e positivos de 0,155 (P<0,001) e 0,267 (P<0,001), respectivamente. Os resultados evidenciam a necessidade pelos produtores, técnicos e indústrias de reavaliarem a gestão dos programas de controle da mastite que focam a saúde da glândula mamária, procedimentos de higiene dos equipamentos de ordenha, resfriamento, temperatura e tempo de armazenagem do leite, melhorando a qualidade microbiológica do leite e implantação de programas de pagamento por qualidade baseados na CCS e CBT.

The objective of this study was to investigate the effects of rumen-protected methionine (RPM) supplementation during early lactation on performance and metabolic parameters of dairy cows. Forty-two Holstein cows were blocked by parity (22 primiparous and 20 multiparous) and calving date, then randomly assigned to two groups, Control and RPM. From calving through 29 ± 8 d in milk, cows received an early lactation diet [1.59 Mcal/kg of DM, 10.7% rumen-degradable protein and 6.5% rumen-undegradable protein] with no added methionine (Control, n = 21) or with supplementation of Smartamine M (RPM, Adisseo Inc, n = 21). RPM cows were supplemented with 12 g/day Smartamine M (7.2 g of metabolizable methionine), individually top-dressed over the total mixed ration. Blood and milk samples were collected during the first two weeks of lactation and milk yield recorded until 30 days in milk. No differences in milk yield or blood metabolites were observed. Cows supplemented with RPM increased milk fat and total solids contents and fat-to-protein ratio by 0.48% units, 0.66% units, and 0.09 units, while tended to increase milk total protein content by 0.13% units, respectively. This study showed beneficial effects of early postpartum RPM supplementation on milk composition of dairy cows.

Avaliou - se os efeitos de meio sobre a porcentagem de sólidos totais de amostras de tanque coletadas pelas indústrias, analisadas pelo Laboratório de Qualidade do Leite do Programa de Análise de Rebanhos Leiteiros da Associação Paranaense dos Criadores de Bovinos da Raça Holandesa, Curitiba - PR. Foram analisadas 1.950.034 amostras de leite, do período de janeiro de 2005 a abril de 2012, em dez regiões do Estado do Paraná. As médias estimadas, desvios-padrão e coeficiente de variação para % de sólidos totais e idade da amostra em dias foram: 12,29 ± 0,85; 6,79% e 2,98 ± 1,57 dias, respectivamente. Todos os efeitos incluídos no modelo estatístico (mês e ano de análise, região, idade da amostra e escore da contagem de células somáticas) influenciaram significativamente (P<0,01) a variável estudada. Os maiores valores para a % de sólidos totais ocorreram no mês de maio (12,46 ± 0,0023), no ano de 2012 (12,37 ± 0,0026), na região de Curitiba (12,42 ± 0,0017), com seis dias de idade da amostra (12,27 ± 0,0030) e quando o escore da contagem de células somáticas (ECS) variou de zero a seis (zero a 1.130.000 células/ mL) a % de sólidos totais aumentou de 12,03 para 12,30%, respectivamente. A correlação de Pearson entre a % de sólidos totais com o ECS, foi baixa e positiva (0,039).