CPD article: Pre-breeding heifer examination and selection in UK beef herds

The objective of this review is to evaluate examination tools and how they can be used to assess the breeding potential of beef heifers prior to service. Reproductive tract examination techniques, pelvic measurement, and antral follicle counts (AFC) are methods that are used and could be of value to farmers where they can either identify pubescent heifers and/or those with the best reproductive potential. Reproductive tract scoring (RTS) to assess the pubertal state and therefore reproductive status of replacement heifers is explored alongside further adaptions of this method. The use of pelvic measurement is considered: first, where a small pelvic area or an abnormal shaped pelvic inlet is identified, which may result in elimination from the breeding cohort to reduce the potential risk of dystocia and poor performance; and second, since it may be advocated for use in conjunction with other methods. AFC are included since they too may help identify the reproductive potential of heifers. Evaluation of these examination tools demonstrates that the use of modified RTS methods, to include ultrasound examination to detect the absence of a corpus luteum (CL), absence of a follicle ≥ 13 mm and the uterine horn diameter as well as pelvic measurements, could add value to heifer breeding soundness examinations (HBSE) when carried out.

Gestational nutrition 1: alterations to gestational nutrition can increase indicators of fertility in sheep

The aim of this study was to examine the relationships between gestational nutrition, fetal ovarian development and offspring fertility in female sheep and to highlight the potential mechanisms underlying these relationships. Adult sheep (n = 79) were fed either a maintenance or 0.6 of maintenance plane of nutrition for the first 55 days of gestation and thereafter fed ad libitum. Fetuses were collected for analysis at days 55 and 75 of gestation. Female offspring were monitored from birth until 19 months of age. Effects of restricted nutrition were observed on maternal plasma concentrations of progesterone, creatinine, albumin and Ca2+ at day 55 and creatinine at day 75. Concentrations of metabolic factors and steroid hormones in day 75 fetal plasma were not affected by the restricted maternal plane of nutrition. At day 55 of gestation, fetal ovarian germ cell development was not affected by maternal plane of nutrition. At day 75 of gestation ovaries from fetuses whose dams were exposed to restricted nutrition contained more germ cells but had lower germ cell proliferation rates than controls. For female offspring at 8 months of age, the dams gestational plane of nutrition did not affect the onset of puberty, ovulation rate (OR) and antral follicle counts (AFC). At 19 months of age, ewes from dams exposed to the restricted plane of gestational nutrition had higher OR, AFC and progesterone concentrations while concentrations of FSH were lower. In conclusion, while effects on fertility per se are yet to be determined, a reduced maternal plane of gestational nutrition can improve indicators of fertility in female offspring.