Exogenous and endogenous factors in seasonality of reproduction in buffalo: A review.

Seasonal breeding in buffalo is influenced by exogenous (photoperiod, climate, nutrition, management) and endogenous (hormones, genotype) factors. Buffalo are negatively photoperiodic and show a natural increase in fertility during decreasing day length. The hormone melatonin is produced by the pineal gland and has a fundamental role in photoperiodic time measurement within the brain. This drives annual cycles of gonadotropin secretion and gonadal function in buffaloes. Some melatonin is released into the systemic circulation and, together with peripherally produced melatonin, acts at somatic tissues. In the ovaries and testes of buffalo, melatonin acts as an antioxidant and scavenges oxygen free radicals to reduce both oxidative stress and apoptosis. This has beneficial effects on gametogenesis and steroidogenesis. Female buffalo treated with melatonin show an improved response to estrus synchronization protocols in out-of-season breeding. Melatonin acts through melatonin receptors MT1 and MT2 and the gene for MT1 (MTNR1A) is polymorphic in buffaloes. Single nucleotide polymorphisms (SNPs) in gene MTNR1A have been associated with fertility in female buffalo. The knowledge and tools are available to lift the reproductive performance of buffalo. This is highly important as the global demand for nutritious buffalo food products has undergone a sharp rise, and continues to grow. Buffalo can make an important contribution to affordable, nutritious animal protein. This will help address global nutritional security.

Vascularization to preovulatory follicle and corpus luteum-a valuable predictor of fertility in dairy cows.

The aim of the present study was to predict pregnancy rate based on vascularization to follicle and corpus luteum (CL). 26 Holstein Friesian cows were synchronized using Ovsynch protocol. On day 10 of the protocol, vascularization and morphological characteristics [sectional area (SA), volume (V) and mean diameter] of follicle was assessed and animals underwent artificial insemination (AI). Morphological evaluation and vascularization to CL was assessed on day 12 and 21 following AI and blood samples were obtained for estimation of plasma progesterone (P4). Pregnancy diagnosis was performed on day 60 of AI and was classified as normal, complicated and non-pregnant. The overall conception rate was 76.92% (20/26); normal pregnancy was 53.85% (14/26). Complications observed in pregnancy were intrauterine growth retardation, late embryonic death and infection. Cows with a highly vascularized follicle (>550 pixel2) underwent a normal pregnancy, whereas those that had moderately (250-550 pixel2) and poorly (<250 pixel2) vascularized follicle experienced complicated pregnancy or remained non-pregnant, respectively. On day 12, there was no significant variation (P > 0.05) between mean diameter, SA, V, luteal blood flow (LBF) or plasma P4 concentration among CL of cows that remained pregnant (PCL), non-pregnant (NPCL) or that had a complicated pregnancy (CPCL). LBF alone was not beneficial in differentiating among the three groups (P > 0.05), but assessment of LBF along with turbulence to blood flow in day 21 CL proved highly valuable due to an increased turbulence in CPCL (66.67%) compared to PCL (16.67%). Assessment of turbulence and LBF on day 12 and 21 can also be used to predict luteolysis with accuracy.