Anti-Müllerian Hormone (AMH), antral follicle count (AFC), external morphometrics and fertility in Tabapuã cows.

The intense selection of characteristics related to animal performance may affect the reproductive efficiency of beef cows negatively. Selection for fertility along with production traits is, therefore, readily justifiable. The objective of the present study was to evaluate possible relationships among AFC, serum AMH concentrations and external morphometrics with reproductive efficiency in Tabapuã (a Brazilian Bos indicus beef breed) females. Antral follicle counts and external morphometrics were measured in nulliparous (n = 162), primiparous (n = 80) and multiparous (n = 351) cows, from four farms. Age at first parturition (AFP), parturition interval (PI), maternal ability (MA), precocity, rusticity and survival (PRS) and overall reproductive efficiency (RE) were evaluated according to the Brazilian Association of Zebu Breeders (ABCZ) data bank indexes. A single blood sample per animal was collected at random stages of the reproductive cycle from a subset of animals (nulliparous = 84, primiparous and multiparous = 136) to determine serum AMH concentrations. The AFC classes were defined as lesser (<28), intermediate (28-50) and greater (>50). Correlations between all variables and the effects of parity and AFC on reproductive traits, AMH and external genitalia size were analyzed by the PROCORR and by the PROCGENMOD procedures of SAS® (SAS, Cary, NC, USA), respectively. Antral follicle count did not differ (P = 0.71) among nulliparous (38.6 ±â€¯23.96) primiparous (47.54 ±â€¯26.16) and multiparous (41.08 ±â€¯25) cows and was negatively correlated with pregnancy interval (PI), such that, as PI decreased (r = -0.28; P < 0.005), AFC increased. Vulva width was not affected (P = 0.08) by parity and was larger (P < 0.05) for females in the greater AFC class (8.81 ±â€¯0.12 cm) compared with the intermediate (8.42 ±â€¯0.11 cm) and lesser (8.38 ±â€¯0.13 cm) classes. As vulva width increased, parturition interval decreased (r = -0.15; P < 0.005) and overall reproductive efficiency increased (r = 0.17, p < 0.005). Thoracic depth was associated with greater AFCs (r = 0.10; P < 0.001). Anti-Müllerian hormone concentrations were greater (P < 0.05) for animals in the greater AFC class (1.15 ±â€¯0.09 ng/mL) compared with the lesser (0.44 ±â€¯0.02 ng/mL) and intermediate (0.73 ±â€¯0.05 ng/mL) classes. Vulva width, AFC, external morphometrics and AMH concentrations were moderately associated, considering the low heritability of fertility traits, and should be studied further to be considered in the selection for fertility in Bos indicus cattle.

Curvas de crescimento de fêmeas da raça nelore e seus cruzamentos / Growth curves of female nelore and their crosses

Seleção para características do crescimento pode ser feita após ajustadas funções de crescimento para todos os animais sob seleção. Porém, a curva de crescimento de fêmeas é influenciada pelas gestações e lactações subsequentes. Neste trabalho, métodos são descritos para selecionar uma função que ajuste a curva de crescimento de fêmeas bovinas considerando-se os efeitos de variação de peso corporal devido a gestação e a lactação. Foram utilizados dados provenientes do Instituto Agronômico do Paraná, constituindo-se de 15.271 observações de pesos de 103 fêmeas, sendo 43 Nelore, 10 F1 Guzerá x Nelore, 29 F1 Red Angus x Nelore, 5 F1 Marchigiana x Nelore e 16 F1 Simental x Nelore. Comparou-se o ajuste das funções de Brody, Gompertz, Logística, Von Bertalanffy e Michaelis-Menten reparametrizada (MMr) aos efeitos do ganho de peso em função da idade, sendo adicionado a todas as funções o ganho de peso durante a gestação e a perda de peso na lactação de fêmeas da raça Nelore e Cruzadas. Ao ajustar as funções, observou-se um Coeficiente de Determinação Múltiplo Ajustado variando entre 0,7552 e 0,9267. Observou-se o menor Quadrado Médio do Resíduo e o Desvio Médio Absoluto para a função de MMr. Para descrição da curva de crescimento em função da idade das fêmeas, deve ser ajustada a função de MMr.

Selection for growth characteristics can be done after fitting growth functions for all breeding animals. However, in the female population the growth curve is influenced by gestation and subsequent lactations. In this work methods are described to select a function that fits a growth curve of bovine females considering the varying effects of body weight due to gestation and lactation. Data from the Paraná Agronomic Institute (IAPAR) were used consisting of 15.271 weight observations of 103 females distributed as 43 Nelore, 10 F1 Guzerá x Nelore, 29 F1 Red Angus x Nelore, 5 F1 Marchigiana x Nelore and 16 F1 Simental x Nelore. The function adjustment of Brody, Gompertz, Logística, Von Bertalanffy and Michaelis-Menten reparametrized MMr were compared to the effects of weight gain as a function of age, adding to all functions the weight gain during gestation and the weight loss in the lactation of Nelore and crossbreed females. It was observed an Adjusted Coefficient of Multiple Determination varying from 0.7552 to 0.9267. Lower Residue Mean Square and Absolute Mean Deviation were observed for the MMr function. The MMr function must be adjusted in order to describe the growth curve as a function of the female age.