Some effects of level of feeding and body condition upon sperm production and gonadotropin concentrations in the ram

Abstract

1982). Some effects of level of feeding and body condition upon sperm production and gonadotropin concentrations in the ram. ABSTRACT 1. In two experiments. Scottish Blackface and Finnish Landrace cJ x Dorset Horn $ rams were housed in lightproof buildings and subjected to a constant 10-h light: 14-h dark photoperiod 70 days before and during the experiment. In experiment 1, four rams from each breed type were given either 750kJ/MJ(L) or 1250 to 1500 kJ/MJ(H) of their maintenance requirement for 20 weeks. In experiment 2, four rams of each breed were given either 750kJ/MJ(T) or 2000 kJ/MJ(F) of their maintenance requirement for 20 weeks, and were then fed to maintain live weight for a further 10 weeks. Daily sperm output in the urine and scrotal circumference were measured in both experiments. Various characteristics of ejaculated semen were measured in experiment 1. Sequential blood samples were collected from the rams on both experiments and assayed for follicle stimulating hormone and luteinizing hormone. At the end of each experiment the rams were slaughtered, and their testes, epididymides and anterior pituitary glands recovered.2. In Experiment 1, the L feeding level depressed progressively the numbers of sperm voided in the urine, scrotal circumference, and the concentration and total numbers of sperm in ejaculated semen. The testes and epididymides of L rams were lighter (/ > <001) and fewer sperm were recovered from the reproductive tract than in H rams (P<001). The pituitary glands were lighter (P<005) and contained less luteinizing hormone (/ ) <0-01) but amounts of follicle stimulating hormone similar to the H rams. Plasma luteinizing hormone levels were lower in L than in H rams at 20 weeks (/ > <005).3. In experiment 2, the T rams showed a progressive depression of numbers of sperm in the urine and scrotal circumference, such that at 20 weeks differences between F and T treatments were statistically significant (/ > <005 and 001 respectively). Subsequently, some recovery occurred which, with a reduction in these measures on F treatments, led to there being no statistically significant difference at 30 weeks. There were no statistically significant differences between F and T treatments in testes and epididymes weights, total number of sperm in the tract, and anterior pituitary weight, follicle stimulating hormone and luteinizing hormone content.

The Interaction Between Photoperiod and Nutrition and Its Effects on Seasonal Rhythms of Reproduction in the Ewe1

“…The results suggest that the site of integration is hypothalamic. However, in our study, as for similar experiments [38][39][40], the conclusion concerning direct effects of nutrition on the characteristics of LH pulsatility may be biased, because it was not determined at the same physiological moment in the annual reproductive cycle for each nutritional group (i.e., the sampling window was closer to the termination of the active reproductive neuroendocrine season for the R-OVX group than it was for the WF-OVX group), a factor known to influence the characteristics of LH pulsatility [41]. In this regard, the only …”

Seasonal pattern of LH and testosterone secretion in adult male fallow deer, Dama dama

“…Moreover, the decline in pulse frequency and amplitude occurred in April despite the continuing occurrence of decreasing daylength until the winter solstice in June. Thus, although it is tempting to ascribe the post-rut (May) decline in LH, and subsequently testosterone, in the entire bucks to their deteriorating body condition, as postulated for rams (Alkass et al, 1982), the same decline in LH secretion occurred in the castrated bucks which, for obvious reasons, did not exhibit rut-related liveweight losses. Various authors have proposed, on the basis of fixed light intervals, that seasonal breeders become refractory to long or short days (e.g.…”

Contrasting effects of different levels of food intake and adiposity on LH secretion and hypothalamic gene expression in sheep

“…However, reproductive neuroendocrine output, measured by pulsatile luteinising hormone (LH) secretion, is stimulated by short-term increases in food intake ('flushing') in ewes (Rhind et al 1985(Rhind et al , 1991 and rams (Martin & Walkden-Brown 1995), but not by long-term increases in body fat reserves in ewes (Rhind & McNeilly 1986, Rhind et al 1989. Similarly, LH secretion is reduced in rams on restricted feeding, but pituitary LH content is not different between maintenance-fed rams with different levels of body fat (Alkass et al 1982). Since LH secretion is an indirect measure of hypothalamic gonadotrophin-releasing hormone (GnRH) pulsatile output (Clarke & Cummins 1982), these findings suggest that the hypothalamus can dissociate long-and short-term nutritional feedback with respect to GnRH activity.…”