Interactions between nutrition and reproduction in the management of the mature male ruminant

Abstract

In mature male sheep and goats, changes in feed intake seem to have little effect on gonadal endocrine function but induce profound changes on sperm production. These outcomes are due to changes in size of the seminiferous tubules and in spermatogenic efficiency. Except with severe underfeeding, there are only minor changes in the endocrine function of the testis (testosterone production) unless season-long treatments are imposed. For cattle, nutrition clearly affects testicular development and the production of spermatozoa in young bulls, as it does in other species but, after the period of rapid growth has ended, there appears to be little or no response to nutrition. We are developing a clear picture of the metabolic signals, neuroendocrine processes and hormonal control systems that are involved, particularly for the mature male sheep. The energetic components of the diet, rather than protein, seem to be responsible, so we have envisaged a model of the relationship between energy balance and reproduction that has 4 'dimensions': genotype, structure (organs), communication (chemical and neural signals, nutrient sensing) and time (dynamics, metabolic memory, programming). We have linked these perspectives to 'resource allocation theory' and incorporated them into strategies for 'clean, green and ethical animal production'. In contrast to the clear outcomes with respect to spermatogenesis, the effects of nutrition on sexual behaviour are more difficult to define, perhaps because the behaviour is affected by a complex mix of physiological factors and because of flawed methods for quantifying male behaviour. For example, sexual behaviour is compromised by severe feed restriction, but male sexual behaviour requires intensive motor activity so a decline in libido could be caused by general weakness rather than specific nutritional limitations. The interaction between sexual activity and feeding behaviour also complicates the issue under field conditions. At the other end of the scale, overweight males can show reduced sexual success because they have difficulty courting and mounting. For this reason, exercise can enhance the fertilising capacity of rams. This will be important in extensive mating systems where males need to assemble and guard a harem and then mate many times for several weeks. For artificial insemination centres, there seems to be very few data on the nutritional management of males, but problems with overfed animals appear to be a risk. Future research should concentrate on the intra-testicular systems mediating the effects of nutrition on the production of spermatozoa.

Characterization of the productive performance of Highlander sheep in Southern Chile. I. Female reproductive traits

“…Reproductive traits exhibited by Highlander ewes are similar to what has been described for sheep (Goodman and Inskeep, 2006;Bartlewski et al, 2011). These ewes were selected only for having had a normal lambing and were subjected to maintenance diets to keep a BCS to facilitate the normal operation of the reproductive axis (for review: Martin et al, 2010;Clarke, 2014;Dupont et al, 2014). It is interesting to note that the number of follicles ovulated averaged near 2.0 and that 30/33 (90.9%) of ovulatory-sized follicles at estrus, actually ovulated.…”

Improving Libido and Sperm Quality of Bali Bulls by Supplementation of Moringa oleifera Leaves

“…The semen quality of a bull is influenced by the nutritional factor (Martin et al, 2010), age, season (Bhakat et al, 2011), and breed (Lemma & Shemsu, 2015). The nutrition status of a bull controls sperm production, the secretion of gonadotropin, and sexual development.…”

“…The nutrition status of a bull controls sperm production, the secretion of gonadotropin, and sexual development. The capacity of testes of an adult male animal to produce sperm and testosterone is influenced by the ability of the seminiferous tubules and the Leydig cells or interstitial cells under the stimulation of Follicle Stimulating Hormone (FSH) and Luteinizing Hormone (LH) (Martin et al, 2010).…”

Characterization of the productive performance of Highlander sheep in Southern Chile. II. Male reproductive traits

“…The significant difference found in scrotal circumference and its impact on sperm concentration of their ejaculates may just represent an expression of the rearing condition of lambs from both breeds as Suffolk rams performed relatively low compared to the breed (Martin et al, 2010). Suffolk stock in Chile is reared usually under more exigent conditions than Highlander lambs (Odepa, 2013).…”