Accelerated lambing achieved by a photoperiod regimen consisting of alternating 4-month sequences of long and short days applied year-round1

Abstract

the World Wide Web at:The online version of this article, along with updated information and services, is located on www.asas.org at Bibliotheque De L'Univ. Laval Section Des Acquisitions on September 10, 2010. jas.fass.org Downloaded from ABSTRACT: The objective of this work was to evaluate the reproductive performance of ewes exposed to a photoperiodic regimen consisting of continuous alternating 4-mo periods of long days (LD: 16 h of light/d) and short days (SHD: 8 h of light/d) in an accelerated lambing program of 3 lambings in 2 yr. A total of 211 prolific Rideau Arcott ewes were assigned to the photoperiodic treatment, whereas 37 ewes were maintained under natural annual variation in day length (control group). Ewes under the photoperiod regimen were divided into 4 subgroups (A, B, C, D). All these groups of ewes were exposed to the same light regimen, but the LD and SHD light sequences were staggered by 2 mo to permit the evaluation of the effect of time and season of mating on performance of the ewes treated with the photoperiod. The control ewes were treated with intravaginal sponges in the out-of-season breeding periods (conventional approach). Each group of ewes was studied over 3 reproductive cycles. Two groups of rams exposed to alternating 2-mo sequences of LD and SHD were used for mating. The short mean interval between ram introduction and conception for the groups exposed to artificial photoperiod (9.4 d) confirmed the effectiveness of the treatment to induce intense sexual activity. For the 12 breeding periods studied (8 in outof-season and 4 in sexual season), fertility rate of the ewes treated with photoperiod, mated at various times of year, was 91.6%, which is comparable with the fertility normally seen in the natural breeding season. The number of lambs born/ewe remained constant across reproductive cycles and was greater in photoperiodtreated groups (2.81 vs. 2.27 for photoperiod and control groups, respectively; P = 0.0002). Groups exposed to photoperiod treatment obtained better fertility rate than the control group in out-of-season breeding (91.1 vs. 76.3%; P = 0.016). Ewes managed under the photoperiod regimen produced 1.38 lambings/yr and 69% of them lambed 3 times in 2 yr. Overall, the ewes in the photoperiodic treatment produced annually 3.78 lambs/ ewe. The reproductive performances achieved throughout the years indicate that the photoperiodic program tested, consisting of continuous alternating 4-mo periods of LD and SHD, allows control of the annual reproductive cycles in ewes.

Asynchrony in host and parasite phenology may decrease disease risk in livestock under climate warming:Nematodirus battusin lambs as a case study

“…Such non-linear effects of climate change on ecology have been described in other systems (Mooney et al 2009) and in some cases can be explained by relatively simple mechanistic models (Andre et al 2010). Future adjustments in lambing dates to take advantage of earlier grass availability in spring could change assumptions of host availability in the current model, although these are likely to be constrained by unchanging autumn photoperiod, at least in the absence of technically demanding or costly strategies such as breed selection, hormonal intervention or artificial lighting regimes (Cameron et al 2010). The present paper uses such an approach by applying experimentally-obtained parasite vital rates to predict regional effects on disease incidence in farm ecosystems.…”

Demographic, environmental and genetic determinants of mating success in captive koalas (Phascolarctos cinereus)

“…By focusing the breeding attempts during the peak breeding season and on younger females (or pairing them with older males), population managers could be able to increase the success rate of both copulations and joey production in captivity. In the case of day length, direct manipulation (e.g., the addition of artificial light) may also help increase mating success as in domestic animals (Cameron et al, ; Malinowski et al, ).…”

“…Many factors have been shown to affect mating in vertebrates. For example, age can affect the reproduction of both sexes (Costello, Creel, Kalinowski, Vu, & Quigley, ; Rughetti, Dematteis, Meneguz, & Festa‐Bianchet, ; Somashekar, Krishna, Hegde, & Jayaramu, ) and photoperiod can affect female reproductive behavior and fertility, which is leveraged in domestic species to improve reproductive success (Cameron, Malpaux, & Castonguay, ; Malinowski, Johnson, & Scanes, ; Moffatt & Nelson, ). Another determinant of reproductive success is sexual selection, which has two components: male competition and female choice (Darwin, ).…”

The Role of Melatonin in Ewes Reproduction: a Review

“…In ewes, the large environmental factor that controls the breeding is the day length (photoperiod) (43). The day light exposure variance modify the production and releasing of MLT from PG, and in turns that binds to the nuclei of hypothalamus and regulate the pulses releasing of GnRH (44).…”