Ram Management

By Tim Barnes Ohio State Extension Marion County

To achieve maximal fertility, rams should be physically examined for reproductive fitness to detect abnormalities that may affect breeding performance.  A breeding soundness examination can be completed before breeding season.  The scrotum and its contents and the penis and prepuce must be carefully examined.  The size and symmetry of both testes and epididymides should be assessed, and both testes should be firmly palpated for consistency and resilience. Semen can be collected and evaluated to check potential sires, particularly in ram lambs.  All screening procedures should be done 2-3 weeks before mating to allow management changes if a ram needs to be replaced in the breeding program.

Supplementary feeding of the ram can be started 6 weeks prior to breeding season.  High protein rations can increase both testicular size and number of cells in the germinal layers of the testicle, resulting in increased sperm production.

Mating activity may be monitored by using a breeding harness on the ram and changing the color of the crayon color every 14-17 days.  When fewer than expected ewes are marked, poor ram libido, insufficient number of rams to breed the flock, or anestrus is suspected.  When ewes are serially marked with different colors, conception failure or early embryonic death is possible.

The ram to ewe ratio varies with breed and whether synchronization or induction of estrus has been practiced.  For ram effect, the ration should be 1:20; for estrus synchronization, 1:10 to 1:15 (in season); and estrus induction (out of season), 1:15 to 1:17.

Length of ram exposure during the breeding season should be limited to two or three cycles so the lambing period will be shorter and this will optimize lambing management.  Excellent fertility can be achieved with a breeding exposure of 35-42 days.  Poor fertility indicates an issue with the ram management.  Flock movement should be avoided at mating, but normal handling should not affect mating.  Because younger ewes have a shorter, less intense estrous period, they are better mated separately from older ewes with experience rams.

MANAGEMENT FACTORS AFFECTING SHEEP FERTILITY

 

Introduction

An Arab horse breeder in the early 13th century carried out the first insemination reported,

by trapping stallion semen in wool placed in the vagina of a mare and transferring this to

the vagina of another mare (Heape, 1898). Later, in 1780, an Italian priest and physiologist

named Lazzaro Spallanzani performed artificial insemination with dog semen, and

revolutionised the way scientists thought. Since then, scientist and farmers have striven to

improve this technology, motivated by the benefits that could be achieved. Sheep is one

of the species subsequently linked to this technology and in which many questions still

remain to be resolved to improve fertility. However, the potential impact of this technique

on the genetic progress of sheep is high and further studies are needed to improve its

efficiency.

Artificial insemination programs in sheep are linked to the genetic selection

schemes of the breeds, but it has not been successfully integrated with reproductive

technology on farms as happen in sows or cows. The technical difficulty and weak fertility,

ranged between 15 to 60 % for pregnancy rate, limits its application.

Female associated factors

Management factors associated with artificial insemination in the ewe can modify fertility.

In reproductive planning, intervals between lambings, season, age of ewe, heat stress,

nutrition state or breed are some of the factors which have a great effect on fertility results.

David et al. (2008), using a joint model combining two main traits, one relative to female and

the other relative to the male, reported that the main variation factors of AI success were

relative to non-sex-specific effects and to female effect, suggesting that choosing females to

inseminate might slightly improve the AI results.

Season

Seasonal variations are described as a limiting factor in sheep reproduction. In natural

conditions, seasonality, which is mediated by photoperiod, modifies hormonal balance and

causes seasonal reproductive variations in sheep (Karsch, et al. 1984; Yeates, 1949), giving

rise to a decrease in reproductive activity during long days (anoestrous season).

Photoperiodic information is translated into neuroendocrine changes through variations in

melatonin secretion from the pineal gland (Bittman, et al., 1983). Melatonin, secreted in

pineal gland, triggers variations in the secretion of luteinising hormone-releasing hormone

(GnRH), luteinising hormone (LH) and follicle stimulating hormone (FSH) (Arendt, et al.,

1983, Karsch, et al., 1984). In any case, seasonal changes in reproductive activity are clearly

defined in sheep breeds from high latitudes (>40º)(Pelletier, et al., 1987), where the

differences in daylight duration between short days and long days are more notable.

As in natural mating, season affects fertility after AI, although hormonal treatment is used

to synchronise and induce oestrus. Windsor (1995) reported low cervical AI fertility rates in

non-breeding season in Merino ewes, a shallow seasonal breed. According to this, Anel et al.

(2005) found a season effect on the AI fertility in Churra ewes, which was more important in

cervical than laparoscopic artificial insemination. In cervical AI, semen is deposited in the

external portion of the cervix and the sperm transport is affected by cervical mucus quality.

Theses authors suggest that photoperiod could alter progestagens and so cervical mucus

characteristics, making it scarcer and more viscous. In consequence, sperm transport in the

cervix can be interfered with. It is important to note that seasonality affects the ram

reproductive parameters in the same way and changes in seminal quality during anoestrous

season may decrease the fertility results after AI.

Heat stress

It has been reported than in tropical and sub-tropical areas the local sheep show restricted

sexual activity in the summer months (Marai et al., 2004). Marai et al., 2007 reviewed how

exposure to high ambient temperature causes impairment of reproductive functions in

sheep. The heat effect is aggravated when heat stress is accompanied with high ambient

humidity (Marai et al., 2000, 2004, 2006, 2007). Heat stress evokes a series of drastic changes

in animal biological functions, which include a decrease in feed intake efficiency and use,

disturbances in the metabolism of water, protein, energy and mineral balances, enzymatic

reactions, hormonal secretions and blood metabolites. (Shelton, 2000; Marai et al., 2006).                        Male associated factors

It has been reported that variation in fertility of ram ejaculates exists independently of the sperm quality (Choudhry,

et al., 1995; Paulenz, et al., 2002). Variations in the fertility of rams have been reported after

cervical inseminations with fresh semen (Anel, et al., 2005; Paulenz, et al., 2002), with frozen

semen (Colas, 1979; Windsor, 1997; Soderquist, et al., 1999; Paulenz, et al., 2005, 2007) and

after laparoscopic inseminations with frozen semen (Eppleston et al., 1986; Maxwell, 1986;

Eppleston, et al., 1991; Eppleston & Maxwell, 1995). In a large scale epidemiological study,

Anel et al. (2005) observed that the male factor significantly influenced fertility. Despite the

restrictions in the choice of ejaculates, the authors found important differences in fertility

among rams. Salamon and Maxwell (1995) proposed that ram differences in fertility could be both genetic and

environmental, whereas ejaculate differences are probably due to nutrition, management

and previous frequency of ejaculation.

Whereas differences in fertility have been demonstrated among fertile males in different

species, the causes of these differences remain unclear (Ostermeier, et al., 2001). Saacke et al.

(1988, 1994) have suggested in bulls that factors associated with semen quality which affect

fertility can be classified as either compensable or non-compensable. It was suggested that

the effects of compensable factors on fertility might be sensitive to the number of sperm

inseminated, whereas those of non-compensable factors were not. As the number of sperm

inseminated increases, fertility increases until a plateau is reached (den Daas, 1992). At this

point, compensable factors no longer have an effect on fertility. Commercial insemination of

ovine in Mediterranean Countries provides at least the plateau number of sperm in an

insemination dose. It is thus the non-compensable factors that contribute most to the fertility

level of a ram. A non-compensable defect in sperm would be one in which a sperm reaches

the fertilisation site and initiates the egg activation process, but fails to sustain zygotic,

embryonic, or foetal development (Ostermeier, et al., 2001). Evidence of such defects in

sperm has been described in bulls with fertility differences (Eid, et al., 1994). Likely

candidates for non-compensable factors would be incorrectly assembled chromatin or

damaged DNA within the sperm nucleus. It seems logical to assume that the transfer of a

complete and intact DNA molecule from sperm to ovum is crucial to obtain fertilisation

with certain prospects of success. It is well-known that the presence of defects in the genetic

material, such as anomalies in chromatin condensation related with the sperm maturation

process, the integrity of the DNA molecule associated with the presence of breaks both of

single and double DNA strands, or the presence of chromosomal anomalies, are closely

associated with infertility (Aravindan, et al., 1997).

 

Pilar Santolaria, Inmaculada Palacin and Jesús Yániz

Instituto Universitario de Ciencias Ambientales y Departamento de Producción Animal y

Ciencia de los Alimentos. Escuela Politécnica Superior, Huesca

Universidad de Zaragoza

Spain

How Do They Do It?

The sexed semen process explained:

The X chromosomes (determines female) in most animals contain more genetic material than the Y chromosome.  The sorting process revolves around detecting the difference.

After a sample passes an initial quality control check, it is combined with a media that nourishes and invigorates the sperm.  The media also contains a fluorescent dye that binds with genetic material.  The more genetic material a sperm contains the more dye it absorbs.

The sample is then put though a sorting machine called a flow cytometer.  The machine arranges the sperm in single file line and then sends them past a laser.  The laser hits each sperm causing the dye to fluoresce.  The amount of fluorescence tells the flow cytometer whether the sperm is carrying an x or y chromosome.  The cytometer then attaches a slight electric charge to the sperm based on the chromosome it is carries.

As the sperm exits the cytometer, they pass between two charged plates- one with a positive charge and one with a negative charge.  The charge applied to the sperm cell and the charge of the plates combine to direct the sperm cell into the appropriate gender specific vial.

Source: Jim Hiney Sexing Technologies

Use of CIDRs in Sheep

Tim Barnes Ohio Extension Educator

The use of the CIDR has shown to be an effective tool for many producers in the purebred sheep industry.  It has allowed flocks to condense lambing into shorter periods of time and also moved the lambing period into the old traditional “Out of Season” lambing periods.

A CIDR, a T-shaped nylon insert molded with silicone rubber skin containing progesterone that’s released at a controlled rate into the bloodstream after insertion; sheep CIDRs contain 0.3g progesterone per insert.  Progesterone is released from the skin of the insert, causing the ewes blood progesterone concentrations to increase rapidly; maximum concentrations are reached within an hour after insertion. After CIDR removal, a rapid drop in concentration of systemic progesterone occurs, thus promoting a synchronized estrus effect within the flock, allowing for natural or AI to take place.

The wings of the CIDR fold together for intravaginal insertion.  Once inserted, the wings return to their original T-shape and apply pressure to the vaginal walls, thereby holding the CIDR in place.  CIDR are removed by simply pulling the plastic tail protruding from the vulva.

To insert a CIDR, first restrain the animal and then clean the area of the vulva thoroughly.  Put the body of the insert into the applicator, with the plastic tail in the slot.  Apply lubricant to the tip of the insert and position the insert with the tail on the underside of the applicator, curling down.  Open the labia and slide the applicator in at a slight upward angle, then depress the plunge and withdraw the applicator slowly.  To remove, pull gently on the tail and dispose properly.

Sheep CIDRs are available from most livestock supply providers and come in a protected minimum bag of twenty.  Extra CIDRs may be repackaged and frozen to use at a later date.  One CIDR cost about the price of a full breakfast meal at a fast food restaurant.  A special applicator is a one time cost.

We have learned that CIDRs are effective in mature ewes in good body condition that are not lactating and have been isolated from a ram for at least a month for best results.  The ewe ram ratio of 18:1 is recommended when using CIDRs.

REMEMBER STRESS DECREASES FERTILITY.  During the six weeks before mating and five weeks after, avoid transport, rough handling, and abrupt changes in diet or location. Hauling the day of the breeding is the only acceptable transportation time.