Seasonal changes in reproductive activity, sperm variables and sperm freezability in Blanca Andaluza bucks

Abstract

Interest in the preservation of endangered breeds such as the Blanca Andaluza goat, has increased and some steps should be therefore taken to ensure it. The study was designed to determine the seasonal reproductive pattern of Blanca Andaluza bucks, and whether this affects the quality of their semen and its freezability over the year. Seven bucks were used and their body weight, testicular weight, plasma testosterone concentration and fresh sperm quality determined every week. The collected sperm was cryopreserved and stored; it was then thawed and the same sperm quality variables measured every fortnight. High plasma testosterone concentrations were recorded during the summer and autumn, and low concentrations were recorded during winter and spring (p<0.001). No differences were seen between seasons in terms of the percentage of bucks ejaculating, the percentage of active bucks, or ejaculate volume. However, the sperm concentration, the total number of sperm per ejaculate, and the values for most fresh sperm variables were lower during the winter period (at least p<0.05). After freezing-thawing, the quality of winter-collected sperm was better, in some respects, than that of summer-collected sperm (at least p<0.05). These results reveal that Blanca Andaluza bucks show seasonal reproductive activity in terms of their plasma testosterone concentration, but no clear change in their sexual behaviour between seasons was observed. The values of fresh sperm variables also vary over the year, reaching their lowest during winter. However, after freezing-thawing, winter-collected sperm is of overall better quality than sperm collected during the summer.Additional key words: endangered goat breed; testosterone; seasonality; fresh semen; cooled semen; semen cryopreservation.

Cryopreservation and fertility of frozen thawed Chegu goat semen

“…Gross and microscopic seminal parameters in Chegu goats have been tabulate in Table 1 and 2, respectively. The average semen volume in Chegu bucks (Table 1) in present study was higher than West African Dwarf bucks 0.38-0.44 ml, Waidi et al, (2007), Chegu bucks 0.47 ml, Thakur et al,(2005b), Pashmina bucks 0.62 ml, Mohan et al, (1980), Gaddi bucks 0.66±0.04 ml Sharma, (2018), lower than Blanca Andaluza bucks 0.87-0.97 ml, Gallego-Calvo et al, (2015), Blanca-Celtiberica bucks 1.16 ml, Jimenez-Rabadan et al, (2013), Boer bucks 1.15 ml, Yodmingkwan et al, (2016), Majorera bucks 1.21±0.03 ml, Batista et al, (2009) and Blanca de Rasquera bucks 1 ml in 1 year and 1.8 ml in 2 year old Tabarez et al, (2017). Seminal plasma contributes to about 70 per cent of the volume of the ejaculate.…”

“…The concentration of sperms observed in Chegu bucks (2238.5±231.0 x10 6 spermatozoa/ml; Table 1) was higher than 1759.3± 79.79 x10 6 spermatozoa/ml observed earlier in same breed by Thakur et al, (2005b) and West African Dwarf bucks 1.77 x10 9 spermatozoa/ml, Waidi et al, (2007); but lower than Blanca-Celtiberica bucks 2845±142.64 x10 6 spermatozoa/ ml, Jimenez-Rabadan et al, (2013), Gaddi bucks 3401.0± 247.2 x10 6 spermatozoa/ml, Sharma, (2018), Blanca Andaluza bucks, 3336-7776 x10 6 spermatozoa/ml, Gallego-Calvo et al,(2015) investigated during different seasons.…”

When using photostimulated bucks to induce the male effect in female goats living at Mediterranean latitudes, a male: female ratio of 1:20 is optimum

“…Reproductive seasonality is commonly seen in goats living at temperate and subtropical latitudes. Does are normally receptive from early autumn to late winter (Chemineau et al 1992;Gómez-Brunet et al 2003;Zarazaga et al 2005;Gallego-Calvo et al 2014) while bucks show intense sexual behaviour from late summer to late winter (Delgadillo et al 1999;Gallego-Calvo et al 2015). On farms, however, year-round production is required; thus, females need to be brought into oestrus during the anoestrus period by males displaying sexual behaviour (made to do so if necessary).…”

“…At Mediterranean latitudes, anoestrus lasts from January-March to August-September (Zarazaga et al 2005;Gallego-Calvo et al 2014), whereas bucks experience a reduction in their testosterone levels and sexual behaviour between January-February and June-July (Zarazaga et al 2010;Gallego-Calvo et al 2015). Using bucks for the male effect during this period induces ovulation in very few does (Flores et al 2000;Chasles et al 2016).…”

The reproductive performance of female goats treated with melatonin is not improved after introduction to bucks displaying springtime sexual activity if these does are experiencing decreasing body weight/condition score

“…The photoperiod is the main environmental factor governing the seasonality of goat reproductive activity (Zarazaga et al, 2011a, b, c), and certainly in the Blanca Andaluza breed both the male (Gallego-Calvo et al, 2015a) and female (Gallego-Calvo et al, 2014) show reduced sexual activity during the lengthening days of spring. Information on the photoperiod is conveyed to the neuroendocrine system via the circadian secretion of melatonin from the pineal gland (Bittman et al, 1983).…”