Fertility-associated antigen on Nelore bull sperm and reproductive outcomes following first-service fixed-time AI of Nelore cows and heifers.

The objective was to determine whether the presence of fertility-associated antigen (FAA) on sperm collected from Nelore (Bos indicus) bulls can be used to assess potential fertility of sperm for use at first-service fixed-time AI (TAI). Six Nelore bulls were selected based on FAA status (FAA-negative: N = 3; FAA-positive: N = 3) and the ability to produce neat semen with ≥ 70% morphologically normal sperm and 60% estimated progressive motility before cryopreservation. In Experiment 1, suckled multiparous Nelore cows (N = 835) were evaluated for body condition score (BCS) and received an intravaginal progesterone device (CIDR) and 2.0 mg of estradiol benzoate (Day 0). On Day 9 the CIDR was removed, 12.5 mg of PGF(2α) and 0.5 mg of estradiol cypionate were administered, and calves were removed for 48 h. All cows received TAI on Day 11 (48 h after CIDR removal). Pregnancy per TAI (P/TAI) was not different between FAA-positive and FAA-negative bulls (41.5% vs. 39.3%, respectively). There was an effect of AI technician on P/TAI (36.0% vs. 43.9%; P < 0.05) and BCS tended to affect P/TAI (P = 0.09), as cows with BCS ≥ 2.75 were 1.4 times more likely to become pregnant compared with cows with BCS < 2.75. In Experiment 2, nulliparous Nelore heifers (N = 617) were evaluated for BCS and received a CIDR and estradiol benzoate (2.0 mg) on Day 0. On Day 7, all heifers received PGF(2α) (12.5 mg). On Day 9, CIDR inserts were removed and all heifers received estradiol cypionate (0.6 mg) and 200 IU eCG. All heifers received TAI on Day 11 (48 h after CIDR removal). Pregnancy/TAI was different (P = 0.04) between FAA-positive and FAA-negative bulls (33.7% vs. 40.7%, respectively). Presence of FAA on sperm was unsuccessful in assessing the potential fertility of sperm for use in TAI.

Effect of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones, and on sperm production and semen quality in AI bulls in Brazil.

The objectives were to determine the effects of age and genetic group on characteristics of the scrotum, testes and testicular vascular cones (TVC), and on sperm production and semen quality in 107 Bos indicus, B. taurus and cross-bred bulls at three artificial insemination (AI) centers in Brazil. In addition, predictors of sperm production and semen quality were identified. In general, scrotal circumference (SC), scrotal shape score, scrotal neck perimeter, and testicular size (length, width and volume) increased (P < 0.05) with age. Although there were no significant differences among genetic groups for SC or testicular size, B. indicus bulls had the least pendulous scrotal shape, the shortest scrotal neck length, and the greatest scrotal neck perimeter (P < 0.05). Fat covering the TVC was thinner (P < 0.05) in bulls < or = 36 months of age and in B. taurus bulls than in older bulls and B. indicus bulls, respectively. Age and genetic group did not affect testicular ultrasonic echotexture. B. indicus bulls tended (P < 0.1) to have the lowest average scrotal surface temperature (SST). In general, ejaculate volume, total number of spermatozoa and number of viable spermatozoa increased (P < 0.05) with age. However, there was no significant effect of age on sperm concentration, motility, major and total defects. The proportion of spermatozoa with minor defects was highest (P < 0.05) in bulls 37-60 months of age. B. indicus bulls had higher (P < 0.01) sperm concentration, total number of spermatozoa and number of viable spermatozoa than B. taurus bulls, with intermediate values for cross-bred bulls. Increased sperm production was associated with increased testicular volume, SC, TVC fat cover, and SST top-to-bottom gradient. Decreased semen quality was associated with increased SC and bottom SST, and decreased scrotal shape, scrotal neck perimeter and vascular cone diameter. In summary, age and genetic group affected the characteristics of the scrotum, testes, and TVC, sperm production and semen quality. In addition, characteristics of the scrotum, testes and TVC were associated with sperm production and semen quality in bulls and could be assessed for breeding soundness evaluation.

Effects of environmental factors, age and genotype on sperm production and semen quality in Bos indicus and Bos taurus AI bulls in Brazil.

The effects of ambient temperature and humidity, month, age and genotype on sperm production and semen quality in AI bulls in Brazil were evaluated. Data from two consecutive years were analyzed separately. Seven Bos indicus and 11 Bos taurus bulls from one artificial insemination (AI) center were evaluated in Year 1 and 24 B. indicus and 16 B. taurus bulls from three AI centers were evaluated in Year 2. Ambient temperature and humidity did not significantly affect sperm production and semen quality, probably because there was little variation in these variables. Month accounted for less than 2% of the variation in sperm production and semen quality. Increased bull age was associated with decreased sperm motility (P<0.10) and increased minor sperm defects (P<0.001) in Year 1. B. indicus bulls had greater (P<0.005) sperm concentration than B. taurus bulls in both years (1.7 x 10(9)/ml versus 1.2 x 10(9)/ml in Year 1 and 1.6 x 10(9)/ml versus 1.2 x 10(9)/ml in Year 2, respectively). Ejaculate volume was not significantly affected by genotype in Year 1 (6.6 ml versus 6.9 ml in B. indicus and B. taurus bulls, respectively), but B. indicus bulls had greater (P<0.05) total (11.4x10(9) versus 8.2 x 10(9)) and viable (6.7 x 10(9) versus 4.9 x 10(9)) numbers of spermatozoa in the ejaculate than B. taurus bulls. In Year 2, B. taurus bulls had greater (P<0.05) ejaculate volume than B. indicus bulls (8.2ml versus 6.7 ml, respectively) and total and viable number of spermatozoa in the ejaculate were not significantly different between genotypes (10.3 x 10(9) versus 9.1 x 10(9) and 6.1 x 10(9) versus 5.4 x 10(9) in B. indicus and B. taurus bulls, respectively). Sperm motility was not significantly affected by genotype (mean, 59%). In Year 1, B. indicus bulls tended (P<0.10) to have more major sperm defects and had more (P<0.05) total sperm defects than B. taurus bulls (11.8% versus 8.7% and 13.6% versus 10.0%, respectively). In Year 2, B. indicus bulls tended (P<0.10) to have more total sperm defects than B. taurus bulls (16.2% versus 13.3%, respectively). In conclusion, neither ambient temperature and humidity nor month (season) significantly affected sperm production and semen quality. B. indicus bulls had significantly greater sperm concentration and B. taurus bulls had significantly fewer morphologically defective spermatozoa.

Remoçäo do folículo dominante por aspiraçäo transvaginal guiada por ultra-som e resposta superovulatória em vacas Nelore / Dominant follicle removal by ultrasound guided transvaginal aspiration and superovulatory response in Nellore cows

O presente estudo analisou o significado fisiológico do folículo dominante (FD) e sua remoçäo na resposta superovulatória de 42 vacas Nelore e testou a hipótese de que o número de folículos subordinados pequenos (3-8mm) poderia ser usado como critério único para a avaliaçäo da presença ou ausência de um FD nos ovários. Exames ultra-sonográficos foram realizados dois dias antes do início do tratamento superovulatório (D0) e as vacas foram divididas em três grupos: grupo sem FD (SFD), grupo com FD (FD) e grupo com um FD aspirado (FDA). A resposta superovulatória das doadoras näo diferiu entre os grupos, mas a taxa de viabilidade embrionária foi maior nos grupos SFD (69,40 por cento) e FDA (68,99 por cento) grupos, comparados ao FD (48,54 por cento). O número de estruturas näo fertilizadas näo diferiu entre os grupos SFD e FD nem entre SFD e FDA, mas foi maior no grupo FD comparados ao FDA. Pode-se concluir que, em vacas Nelore, a determinaçäo do número de folículos subordinados é um critério seguro para a avaliaçäo da presença ou ausência de um FD nos ovários, mas erros poderiam ser evitados se apenas folículos de 4-8mm fossem considerados, e que a presença de um FD no início da superovulaçäo reduz a taxa de viabilidade embrionária e sua remoçäo por aspiraçäo transvaginal guiada por ultra-som induziu taxas de viabilidade embrionárias semelhantes àquelas observadas na ausência de um FD

Correlaçäo fenotípica entre medidas corporais e peso em touros Nelore / Phenotypic correlation between body measures and live weight in Nelore bulls

Foram analisados 125 touros Nelore de acordo com suas características de peso vivo (P), altura da cernelha (A), comprimento do corno (C) e perímetro torácico (T), com idade (I) entre 24 e 120 meses. As médias e erros padräo foram: 61,47ñ2,41 meses de idade, 839,20ñ10,96kg de peso vivo, 1,73ñ0,07m de comprimento do corpo, 2,18ñ0,01m de perímetro torácico e 1,55ñ0,004m de altura da cernelha. As correlaçöes encontradas foram IxP, 0,41; PxC; 0,81; PxA, 0,65; TxC, 0,71; TxA, 0,61 e AxC, 0,65. Com base nas equaçöes de regressäo testadas, é possível estimar qualquer das características estudadas tendo por base uma delas; perímetro torácico e comprimento do corpo avaliaram com precisäo o peso do animal

Avaliaçäo da circunferência escrotal em touros Nelore / Scrotal circunference Nelore bulls

Foram analisadas as medidas da circunferência escrotal (CE) de 165 touros da raça Nelore, com idades variando de 18 a 48 meses, nas Exposiçöes Nacionais da Associaçäo Brasileira de Criadores de Zebu, em Uberaba/MG. A idade média observada foi de 30,71ñ0,71 meses e a média da CE foi 34,13ñ0,26 cm.A correlaçäo da idade com a CE, foi de 0,61. A equaçäo de regressäo que estimou a CE, utilizando funçäo quadrática da idade do animal (I) foi: CE=18,4531 + 0,806814 (I) - 0,00887585 (I2)