- Email: [email protected]
Ram and buck management
Animal Reproduction Science 130 (2012) 180–183
Contents lists available at SciVerse ScienceDirect
Animal Reproduction Science journal homepage: www.elsevier.com/locate/anireprosci
Ram and buck management夽 A.L. Ridler ∗ , S.L. Smith, D.M. West Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
a r t i c l e
i n f o
Article history: Available online 25 January 2012 Keywords: Breeding soundness Buck Genital system Goat Male Reproduction Ram Sheep
a b s t r a c t Careful management is necessary to ensure the reproductive success in any small ruminant farm and to maximise the productive longevity of rams and bucks. Rams and bucks are frequently overlooked outside of the breeding period, but year-round attention to nutrition, parasite control and general disease control is important in keeping them healthy and sound for breeding. Pre-mating soundness examinations are an inexpensive and relatively easy way to assess the potential ability of a ram or buck to perform during the breeding period and should be incorporated annually into the management of any flock. During the breeding period, careful thought should be given to the appropriate use of males, and the effectiveness of mating should be monitored.
1. Introduction A breeding ram or buck represents a significant investment and the aim of every farmer should be to ensure that their working life is as productive and long as possible. Poor management may result in rams or bucks that are either not sound for breeding or are culled or die well before the end of their productive lives.
8 weeks prior to start of the mating season, because factors affecting scrotal temperature, such as transportation, stress or crowding, can affect spermatogenesis and semen quality (Moule and Waites, 1963). Following purchase, they should be held in quarantine, undergo the administration of an appropriate anthelmintic program, vaccinated as appropriate and inspected for diseases such as footrot (Sargison, 2008).
2. Selection and purchase
3. General considerations – seasonality and puberty
Depending on where in the world they are, rams and bucks for breeding are usually selected primarily on the basis of phenotype or genotype. Regardless, prior to purchase they should be inspected or come with an assurance that they are genitally sound, free from physical abnormalities and where appropriate free from specific diseases. They should be purchased and transported to the farm at least
Breeds of sheep and goat range from breeding all year round to being short-day breeders. In general, breeds that originated from countries in between 35◦ N and 35◦ S are likely to breed all year round; northern European breeds are likely to be distinctly short-day breeders, while breeds from intermediate latitudes may have a short anoestrous period. There is also a large variation within breeds (Rosa and Bryant, 2003). Of those breeds that display seasonality, females exhibit oestrous primarily during autumn, whereas the males are capable of breeding all year round, but their sexual activity and sperm production is greater during the breeding season (Rosa and Bryant, 2003). In seasonal breeds, exposure of the females to males shortly before the start of their normal breeding season
夽 This paper is part of the special issue entitled: Reproductive Health Management of Sheep and Goats, Guest Edited by G.S. Amiridis and G.C. Fthenakis. ∗ Corresponding author. E-mail address: [email protected] (A.L. Ridler). 0378-4320/$ – see front matter doi:10.1016/j.anireprosci.2012.01.012
A.L. Ridler et al. / Animal Reproduction Science 130 (2012) 180–183
results in a small advancement of the start of oestrous activity; this is sometimes referred to as the ‘ram effect’ (Rosa and Bryant, 2002). It also results in oestrous synchronisation which is more evident in goats than sheep (Jainudeen et al., 2000; Martin et al., 1986). Vasectomised males are used in some flocks to advance the start of the breeding season, to advance the mean date of parturition (Thompson et al., 1990) or to advance the onset of puberty in 7- to 9month-old ewes (Kenyon et al., 2006). The recommended timing of introduction of vasectomised males is 14–17 days prior to the start of mating period (Knight, 1980; Kenyon et al., 2006; Sargison, 2008). Puberty in small ruminants is related to age and body weight. Most rams/bucks reach puberty at the age of 4–6 months and 60% of mature body weight (Jainudeen et al., 2000). Once the animals have reached puberty, they may be used for breeding, although, in seasonal breeds, it is common to wait until the following breeding season, when they are 17–19 months old. 4. Management outside the mating period Despite their economic value, rams and bucks are often largely ignored outside of the breeding period. As with all livestock, attention to health, in particular nutrition, parasite control and foot health, throughout the year is essential. Annual breeding soundness examinations are recommended. 5. Breeding soundness examinations Sperm development in the ram and buck takes approximately 50 days. Therefore, examination for breeding soundness is recommended to take place at least 6–8 weeks before the onset of the breeding season, to allow time for resolution of temporary problems or purchase of new animals if necessary. Parametres routinely evaluated include general health, body condition score and genital examination, which includes evaluation of scrotal circumference, testicular tone and lesions. In some cases, semen evaluation, mating tests and general disease testing may also be performed. Rams/bucks are subsequently classified as ‘sound/satisfactory’, ‘temporarily unsound/questionable’ or ‘unsound’. 5.1. Scrotal circumference Scrotal circumference is a widely used parametre in assessing breeding soundness of rams and bucks. In rams, the correlation between scrotal circumference and testicular weight, number of sperm in the testes and number of sperm in the epididymides has been estimated at around 0.92, 0.77 and 0.82 respectively (Lino, 1972; Knight, 1977; Foster et al., 1989). Increased scrotal circumferences has also been associated with increased ejaculate volume and sperm motility in mature rams (Weimer and Ruttle, 1987). Scrotal circumference shows marked variation in seasonal breeds. In rams, differences of up to 30% in testicular volume have been reported between spring and autumn (Rosa and Bryant, 2003); similar findings have been reported in seasonal-breed goat bucks (Walkden-Brown
181
Table 1 Interpretation of scrotal circumference in rams. Ram age
Exceptional
Satisfactory
Questionable
8–14 months >14 months From Bulgin (1992).
et al., 1994). Appropriate cut-off values for classifying an animal based on scrotal circumference are controversial, as they can vary due to age, season, breed and individual variation. In a USA study, involving examination and semen evaluation of over 3000 range rams, Ruttle and Southward (1988) reported that rams with a scrotal circumference of <30.8 cm were more likely to be classified as unsatisfactory. Bulgin (1992) suggested scrotal circumference guidelines for rams (Table 1), but recommended that no ‘unsatisfactory’ rating be used and that practicing veterinarians use their common sense in interpretation of scrotal circumference. Other relevant factors, such as age, breed, season, testicular tone, nutrition, parasite and other concurrent disease status, previous reproductive history and other abnormalities, should be taken into account when evaluating scrotal circumference. 5.2. Testes tone In an animal ready for breeding, the testes should be firm. Testes that are soft in texture may be due to season, age, a congenital defect or subsequent to injury or infection of either the genitalia or systemic illness. Temporary heat stress results in soft testes, testicular degeneration and a transient decrease in semen quality (Blanchard et al., 1991), as does under-nutrition. 5.3. Lesions or abnormalities of the testes and epididymides Lesions of the epididymides are relatively common in rams and are usually due to congenital abnormalities or bacterial infections; more often, the Gram-negative pleomorphic group of bacteria Histophilus ovis and Actinobacillus seminis and Brucella spp. are involved, although, occasionally other bacterial infections or lesions may occur. There is no effective treatment for most epididymal and testicular lesions. 5.4. Semen evaluation Some veterinarians routinely include semen evaluation, as part of a breeding soundness examination, whilst others only do so when there is a clear indication for it. In most clinical situations collection of semen can be achieved by electro-ejaculation (Sargison, 2008). Generally a thorough genital examination will identify most genital defects and it is debatable whether routine semen evaluation of commercial sires that are to be mated as a group of males (‘syndicate’) can be justified. However it may be useful in situations where males are of unproven fertility, are valuable, are to be single-sire mated, have a history of poor reproductive performance or abnormalities are detected on
182
A.L. Ridler et al. / Animal Reproduction Science 130 (2012) 180–183
clinical examination. Today, an array of modern diagnostic techniques has been developed for evaluation of semen and can be used in animals used to provide semen for artificial insemination (Tsakmakidis, 2010). 5.5. Mating tests A number of mating tests (also referred to as serving capacity tests or libido tests) have been described, including introducing rams to ewes in open or closed pens, using long or short test intervals, using ewes in oestrous or not either restrained or unrestrained and putting one or multiple rams in the test arena at a time (Gouletsou and Fthenakis, 2010). There is conflicting evidence on the relationship between mating tests and flock fertility (Fowler, 1984). It is likely that these differences exist due to differences in application and interpretation of the tests, variations in breeding management, as well as interdependence between mating tests, body weight and testicular size (Barwick et al., 1989). The practical difficulties in carrying out mating tests and the uncertainty in their interpretation mean they are rarely applied in a commercial situation. Commercial farmers frequently use more rams than necessary and in groups, so it could be argued that even if a proportion of males are relatively inactive, this is unlikely to have a large impact on flock reproductive performance. 6. Breeding management A successful breeding period relies on mating an appropriate number of sound males to reproductively active females and monitoring to identify any problems.
are used in a group (Vipond and Greig, 2007) to decrease impact of any ram with poor performance. Ram age has an influence on mating ratios. Younger rams produce less total ejaculate than mature rams (Lightfoot, 1968; Allison, 1978; Weimer and Ruttle, 1987) and several studies have suggested that, when 1.5 yearold rams were used for mating, the number of ewes per ram should be reduced (Lightfoot and Smith, 1968; Allison, 1978). There is limited scientific literature regarding the use of 7- to 9-month-old rams for mating, although the general recommendation is to use ratios of 1:30 (Vipond and Greig, 2007) and to avoid mating between ram-lambs and ewe-lambs (Kenyon et al., 2007). Factors related to the female animals can also influence mating ratios. Younger ewes (<2.5 years of age) tend to have better reproductive performance when there are fewer ewes per ram (Lightfoot and Smith, 1968; Kenyon et al., 2010). When oestrous cycle of ewes is controlled by using progesterone inserts, mating ratios of ≤1:10 are recommended (Sargison, 2008). Similarly, when vasectomised rams have been introduced prior to mating, resulting in a degree of synchronisation, fewer ewes per ram are recommended. Other considerations when determining mating ratios include nutritional status, mating management, time of the year, terrain and feed availability. Under-nutrition of rams results in a reduction in testicular size and fewer sperm produced per gram of testicular tissue (Dunn and Moss, 1992). The effect of paddock size is likely to be influenced by the topography of the paddock, the area to be covered by ewes and rams, feed availability, flock dispersion, ram-ewe contact and mating activity (Fowler, 1984). 6.2. Mating management
6.1. Mating ratios The appropriate mating ratio (number of male to female animals) for any situation would vary depending on the numbers, ages and nutritional status of the animals involved, the mating management, the time of the year, terrain and feed availability. Mating ratios of 1 ram per 30–50 ewes (2–3% rams) are frequently mentioned in texts (Jainudeen et al., 2000; Vipond and Greig, 2007); similar ratios have been reported for goat herds. However, a number of studies have demonstrated that, when mature rams are mated to mature ewes, fewer rams can be used with no impact on reproductive performance. Allison (1975) reported no significant difference in reproductive performance between groups at ratios of 3:210, 3:420 or 3:630, although it should be emphasised that the rams used were experienced, sound for breeding and aged between 2.5 and 3.5 years; moreover, they were mating mature ewes in relatively small fields (6–8 ha). As the mating ratio increases above about 1:100, there may be a reduction in the mean number of rams mating each ewe (Fowler, 1984) and a reduction in the number of ewes served in the first 14 days of mating (Lightfoot and Smith, 1968). When ratios of greater than 1:80 to 1:100 are used, it is recommended that the rams are assessed for breeding soundness prior to mating and that at least three rams
Rams or bucks are usually joined with females for 2–3 oestrous cycles. Males are often rotated between groups of females and ‘follow-up’ males may be introduced for the final oestrous cycle. Such practices reduce the impact of any poor performing males. The effectiveness of mating can be monitored by use of mating harnesses or daily application of paint to the sternum of male animals. It is common for rams or bucks to develop lameness, injuries or other health problems during the mating period, hence regular inspection during mating is recommended. 7. Concluding remarks Careful management is necessary to ensure the reproductive success of any sheep flock/goat herd and to maximise the productive longevity of rams and bucks. Rams and bucks are frequently overlooked outside of the breeding period, but year-round attention to nutrition, parasite control and general disease control is important in keeping them healthy and sound for breeding. Pre-mating soundness examinations are inexpensive and relatively easy for assessing potential ability of a ram or buck to perform during the breeding period; they should be incorporated annually into the management of any flock. During the breeding period careful thought should be given to the
A.L. Ridler et al. / Animal Reproduction Science 130 (2012) 180–183
appropriate use of males and the effectiveness of mating should be monitored. Conflict of interest statement The authors have nothing to disclose. References Allison, A.J., 1975. Flock mating in sheep. I: effect of number of ewes joined per ram on mating behaviour and fertility. N. Z. J. Agric. Res. 18, 1–8. Allison, A.J., 1978. Flock mating in sheep. III: comparison of two-tooth and six-tooth rams joined with different numbers of ewes per ram. N. Z. J. Agric. Res. 21, 113–118. Barwick, S.A., Kilgour, R.J., Fowler, J.F., Wilkins, J.F., Harvey, W.R., 1989. Ram mating performance in Border Leicesters and related breed types. 3: relationships of ram serving capacity, testis diameter, liveweight, breed and age with flock fertility. Aust. J. Exp. Agric. 29, 17–22. Blanchard, T.L., Varner, D.D., Bretzlaff, K.N., Elmore, R.G., 1991. The causes and pathologic changes of testicular degeneration in large animals. Vet. Med. 86, 531–536. Bulgin, M.S., 1992. Ram breeding soundness and SFT form. In: Soc. Therio. Ann. Mtg., San Antonio, pp. 210–215. Dunn, T.G., Moss, G.E., 1992. Effects of nutrient deficiencies and excesses on reproductive efficiency of livestock. J. Anim. Sci. 70, 1580–1593. Foster, R.A., Ladds, P.W., Hoffmann, D., Briggs, G.D., 1989. The relationship of scrotal circumference to testicular weight in rams. Aust. Vet. J. 66, 20–22. Fowler, D.G., 1984. Reproductive behaviour of rams. In: Lindsay, D.R., Peirce, D.T. (Eds.), Reproduction in Sheep. Cambridge University Press, pp. 39–46. Gouletsou, P.G., Fthenakis, G.C., 2010. Clinical evaluation of reproductive ability of rams. Small Rumin. Res. 92, 45–51. Jainudeen, M.R., Wahid, H., Hafez, E.S.E., 2000. Sheep and goats. In: Hafez, E.S.E., Hafez, B. (Eds.), Reproduction in Farm Animals. , seventh ed. Lippincott, Williams & Wilkins, Maryland, pp. 172–181. Kenyon, P.R., Morel, P.C.H., Morris, S.T., Burnham, D.L., West, D.M., 2006. The effect of length of use of teaser rams prior to mating and individual liveweight on the reproductive performance of ewe hoggets. N. Z. Vet. J. 54, 91–95. Kenyon, P.R., Morel, P.C.H., Morris, S.T., West, D.M., 2007. Effect of the age of rams on reproductive performance of ewe hoggets. N. Z. Vet. J. 55, 184–187.
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Kenyon, P.R., Morris, S.T., West, D.M., 2010. Proportion of rams and the condition of ewe lambs at joining influences their breeding performance. Anim. Prod. Sci. 50, 454–459. Knight, T.W., 1977. Methods for the indirect estimation of testes weight and sperm numbers in Merino and Romney rams. N. Z. J. Agric. Res. 20, 291–296. Knight, T.W., 1980. Onset of mating activity in Romney ewes after short periods of teasing. N. Z. J. Agric. Res. 23, 277–280. Lightfoot, R.J., 1968. Studies on the number of ewes joined per ram for flock mating under paddock conditions. III: the effect of mating on semen characteristics. Aust. J. Agric. Res. 19, 1043–1057. Lightfoot, R.J., Smith, J.A.C., 1968. Studies on the number of ewes joined per ram for flock mating under paddock conditions. I: mating behaviour and fertility. Aust. J. Agric. Res. 19, 1029–1042. Lino, B.F., 1972. The output of spermatozoa in rams. II: relationship to scrotal circumference, testis weight and the number of spermatozoa in different parts of the urogential tract. Aust. J. Biol. Sci. 25, 359–366. Martin, G.B., Oldham, C.M., Cognie, Y., Pearce, D.T., 1986. The physiological responses of anovulatory ewes to the introduction of rams – a review. Liv. Prod. Sci. 15, 219–247. Moule, G.R., Waites, G.M.H., 1963. Seminal degradation in the ram and its relation to the temperature of the scrotum. J. Reprod. Fertil. 5, 1–16. Rosa, H.J.D., Bryant, M.J., 2002. The ‘ram effect’ as a way of modifying the reproductive activity in the ewe. Small Rumin. Res. 45, 1–16. Rosa, H.J.D., Bryant, M.J., 2003. Seasonality of reproduction in sheep. Small Rumin. Res. 48, 155–171. Ruttle, J.L., Southward, G.M., 1988. Influence of age and scrotal circumference on breeding soundness examination of range rams. Theriogenology 29, 945–949. Sargison, N.D., 2008. Sheep Flock Health, A Planned Approach. Blackwell Publishing, Oxford, pp. 23–25. Thompson, L.H., Stookey, J.M., Giles, J.R., Thomas, D.L., 1990. Reproductive response of mature ewes of different breeds to teasing prior to mating. Small Rumin. Res. 3, 373–381. Tsakmakidis, I.A., 2010. Ram semen evaluation: development and efficiency of modern techniques. Small Rumin. Res. 92, 126–130. Vipond, J., Greig, A., 2007. Management and care of rams. In: Aitken, I.D. (Ed.), Diseases of Sheep. Blackwell Publishing, Oxford, pp. 61–65. Walkden-Brown, S.W., Restall, B.J., Taylor, W.A., 1994. Testicular and epididymal sperm content in grazing cashmere bucks: seasonal variation and prediction from measurements in vivo. Reprod. Fertil. Dev. 6, 727–736. Weimer, K.E., Ruttle, J.L., 1987. Semen characteristics, scrotal circumference and bacterial isolates of fine wool range rams. Theriogenology 28, 625–637.
Contents lists available at SciVerse ScienceDirect
Animal Reproduction Science journal homepage: www.elsevier.com/locate/anireprosci
Ram and buck management夽 A.L. Ridler ∗ , S.L. Smith, D.M. West Institute of Veterinary, Animal and Biomedical Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand
a r t i c l e
i n f o
Article history: Available online 25 January 2012 Keywords: Breeding soundness Buck Genital system Goat Male Reproduction Ram Sheep
a b s t r a c t Careful management is necessary to ensure the reproductive success in any small ruminant farm and to maximise the productive longevity of rams and bucks. Rams and bucks are frequently overlooked outside of the breeding period, but year-round attention to nutrition, parasite control and general disease control is important in keeping them healthy and sound for breeding. Pre-mating soundness examinations are an inexpensive and relatively easy way to assess the potential ability of a ram or buck to perform during the breeding period and should be incorporated annually into the management of any flock. During the breeding period, careful thought should be given to the appropriate use of males, and the effectiveness of mating should be monitored.
1. Introduction A breeding ram or buck represents a significant investment and the aim of every farmer should be to ensure that their working life is as productive and long as possible. Poor management may result in rams or bucks that are either not sound for breeding or are culled or die well before the end of their productive lives.
8 weeks prior to start of the mating season, because factors affecting scrotal temperature, such as transportation, stress or crowding, can affect spermatogenesis and semen quality (Moule and Waites, 1963). Following purchase, they should be held in quarantine, undergo the administration of an appropriate anthelmintic program, vaccinated as appropriate and inspected for diseases such as footrot (Sargison, 2008).
2. Selection and purchase
3. General considerations – seasonality and puberty
Depending on where in the world they are, rams and bucks for breeding are usually selected primarily on the basis of phenotype or genotype. Regardless, prior to purchase they should be inspected or come with an assurance that they are genitally sound, free from physical abnormalities and where appropriate free from specific diseases. They should be purchased and transported to the farm at least
Breeds of sheep and goat range from breeding all year round to being short-day breeders. In general, breeds that originated from countries in between 35◦ N and 35◦ S are likely to breed all year round; northern European breeds are likely to be distinctly short-day breeders, while breeds from intermediate latitudes may have a short anoestrous period. There is also a large variation within breeds (Rosa and Bryant, 2003). Of those breeds that display seasonality, females exhibit oestrous primarily during autumn, whereas the males are capable of breeding all year round, but their sexual activity and sperm production is greater during the breeding season (Rosa and Bryant, 2003). In seasonal breeds, exposure of the females to males shortly before the start of their normal breeding season
夽 This paper is part of the special issue entitled: Reproductive Health Management of Sheep and Goats, Guest Edited by G.S. Amiridis and G.C. Fthenakis. ∗ Corresponding author. E-mail address: [email protected] (A.L. Ridler). 0378-4320/$ – see front matter doi:10.1016/j.anireprosci.2012.01.012
A.L. Ridler et al. / Animal Reproduction Science 130 (2012) 180–183
results in a small advancement of the start of oestrous activity; this is sometimes referred to as the ‘ram effect’ (Rosa and Bryant, 2002). It also results in oestrous synchronisation which is more evident in goats than sheep (Jainudeen et al., 2000; Martin et al., 1986). Vasectomised males are used in some flocks to advance the start of the breeding season, to advance the mean date of parturition (Thompson et al., 1990) or to advance the onset of puberty in 7- to 9month-old ewes (Kenyon et al., 2006). The recommended timing of introduction of vasectomised males is 14–17 days prior to the start of mating period (Knight, 1980; Kenyon et al., 2006; Sargison, 2008). Puberty in small ruminants is related to age and body weight. Most rams/bucks reach puberty at the age of 4–6 months and 60% of mature body weight (Jainudeen et al., 2000). Once the animals have reached puberty, they may be used for breeding, although, in seasonal breeds, it is common to wait until the following breeding season, when they are 17–19 months old. 4. Management outside the mating period Despite their economic value, rams and bucks are often largely ignored outside of the breeding period. As with all livestock, attention to health, in particular nutrition, parasite control and foot health, throughout the year is essential. Annual breeding soundness examinations are recommended. 5. Breeding soundness examinations Sperm development in the ram and buck takes approximately 50 days. Therefore, examination for breeding soundness is recommended to take place at least 6–8 weeks before the onset of the breeding season, to allow time for resolution of temporary problems or purchase of new animals if necessary. Parametres routinely evaluated include general health, body condition score and genital examination, which includes evaluation of scrotal circumference, testicular tone and lesions. In some cases, semen evaluation, mating tests and general disease testing may also be performed. Rams/bucks are subsequently classified as ‘sound/satisfactory’, ‘temporarily unsound/questionable’ or ‘unsound’. 5.1. Scrotal circumference Scrotal circumference is a widely used parametre in assessing breeding soundness of rams and bucks. In rams, the correlation between scrotal circumference and testicular weight, number of sperm in the testes and number of sperm in the epididymides has been estimated at around 0.92, 0.77 and 0.82 respectively (Lino, 1972; Knight, 1977; Foster et al., 1989). Increased scrotal circumferences has also been associated with increased ejaculate volume and sperm motility in mature rams (Weimer and Ruttle, 1987). Scrotal circumference shows marked variation in seasonal breeds. In rams, differences of up to 30% in testicular volume have been reported between spring and autumn (Rosa and Bryant, 2003); similar findings have been reported in seasonal-breed goat bucks (Walkden-Brown
181
Table 1 Interpretation of scrotal circumference in rams. Ram age
Exceptional
Satisfactory
Questionable
8–14 months >14 months From Bulgin (1992).
et al., 1994). Appropriate cut-off values for classifying an animal based on scrotal circumference are controversial, as they can vary due to age, season, breed and individual variation. In a USA study, involving examination and semen evaluation of over 3000 range rams, Ruttle and Southward (1988) reported that rams with a scrotal circumference of <30.8 cm were more likely to be classified as unsatisfactory. Bulgin (1992) suggested scrotal circumference guidelines for rams (Table 1), but recommended that no ‘unsatisfactory’ rating be used and that practicing veterinarians use their common sense in interpretation of scrotal circumference. Other relevant factors, such as age, breed, season, testicular tone, nutrition, parasite and other concurrent disease status, previous reproductive history and other abnormalities, should be taken into account when evaluating scrotal circumference. 5.2. Testes tone In an animal ready for breeding, the testes should be firm. Testes that are soft in texture may be due to season, age, a congenital defect or subsequent to injury or infection of either the genitalia or systemic illness. Temporary heat stress results in soft testes, testicular degeneration and a transient decrease in semen quality (Blanchard et al., 1991), as does under-nutrition. 5.3. Lesions or abnormalities of the testes and epididymides Lesions of the epididymides are relatively common in rams and are usually due to congenital abnormalities or bacterial infections; more often, the Gram-negative pleomorphic group of bacteria Histophilus ovis and Actinobacillus seminis and Brucella spp. are involved, although, occasionally other bacterial infections or lesions may occur. There is no effective treatment for most epididymal and testicular lesions. 5.4. Semen evaluation Some veterinarians routinely include semen evaluation, as part of a breeding soundness examination, whilst others only do so when there is a clear indication for it. In most clinical situations collection of semen can be achieved by electro-ejaculation (Sargison, 2008). Generally a thorough genital examination will identify most genital defects and it is debatable whether routine semen evaluation of commercial sires that are to be mated as a group of males (‘syndicate’) can be justified. However it may be useful in situations where males are of unproven fertility, are valuable, are to be single-sire mated, have a history of poor reproductive performance or abnormalities are detected on
182
A.L. Ridler et al. / Animal Reproduction Science 130 (2012) 180–183
clinical examination. Today, an array of modern diagnostic techniques has been developed for evaluation of semen and can be used in animals used to provide semen for artificial insemination (Tsakmakidis, 2010). 5.5. Mating tests A number of mating tests (also referred to as serving capacity tests or libido tests) have been described, including introducing rams to ewes in open or closed pens, using long or short test intervals, using ewes in oestrous or not either restrained or unrestrained and putting one or multiple rams in the test arena at a time (Gouletsou and Fthenakis, 2010). There is conflicting evidence on the relationship between mating tests and flock fertility (Fowler, 1984). It is likely that these differences exist due to differences in application and interpretation of the tests, variations in breeding management, as well as interdependence between mating tests, body weight and testicular size (Barwick et al., 1989). The practical difficulties in carrying out mating tests and the uncertainty in their interpretation mean they are rarely applied in a commercial situation. Commercial farmers frequently use more rams than necessary and in groups, so it could be argued that even if a proportion of males are relatively inactive, this is unlikely to have a large impact on flock reproductive performance. 6. Breeding management A successful breeding period relies on mating an appropriate number of sound males to reproductively active females and monitoring to identify any problems.
are used in a group (Vipond and Greig, 2007) to decrease impact of any ram with poor performance. Ram age has an influence on mating ratios. Younger rams produce less total ejaculate than mature rams (Lightfoot, 1968; Allison, 1978; Weimer and Ruttle, 1987) and several studies have suggested that, when 1.5 yearold rams were used for mating, the number of ewes per ram should be reduced (Lightfoot and Smith, 1968; Allison, 1978). There is limited scientific literature regarding the use of 7- to 9-month-old rams for mating, although the general recommendation is to use ratios of 1:30 (Vipond and Greig, 2007) and to avoid mating between ram-lambs and ewe-lambs (Kenyon et al., 2007). Factors related to the female animals can also influence mating ratios. Younger ewes (<2.5 years of age) tend to have better reproductive performance when there are fewer ewes per ram (Lightfoot and Smith, 1968; Kenyon et al., 2010). When oestrous cycle of ewes is controlled by using progesterone inserts, mating ratios of ≤1:10 are recommended (Sargison, 2008). Similarly, when vasectomised rams have been introduced prior to mating, resulting in a degree of synchronisation, fewer ewes per ram are recommended. Other considerations when determining mating ratios include nutritional status, mating management, time of the year, terrain and feed availability. Under-nutrition of rams results in a reduction in testicular size and fewer sperm produced per gram of testicular tissue (Dunn and Moss, 1992). The effect of paddock size is likely to be influenced by the topography of the paddock, the area to be covered by ewes and rams, feed availability, flock dispersion, ram-ewe contact and mating activity (Fowler, 1984). 6.2. Mating management
6.1. Mating ratios The appropriate mating ratio (number of male to female animals) for any situation would vary depending on the numbers, ages and nutritional status of the animals involved, the mating management, the time of the year, terrain and feed availability. Mating ratios of 1 ram per 30–50 ewes (2–3% rams) are frequently mentioned in texts (Jainudeen et al., 2000; Vipond and Greig, 2007); similar ratios have been reported for goat herds. However, a number of studies have demonstrated that, when mature rams are mated to mature ewes, fewer rams can be used with no impact on reproductive performance. Allison (1975) reported no significant difference in reproductive performance between groups at ratios of 3:210, 3:420 or 3:630, although it should be emphasised that the rams used were experienced, sound for breeding and aged between 2.5 and 3.5 years; moreover, they were mating mature ewes in relatively small fields (6–8 ha). As the mating ratio increases above about 1:100, there may be a reduction in the mean number of rams mating each ewe (Fowler, 1984) and a reduction in the number of ewes served in the first 14 days of mating (Lightfoot and Smith, 1968). When ratios of greater than 1:80 to 1:100 are used, it is recommended that the rams are assessed for breeding soundness prior to mating and that at least three rams
Rams or bucks are usually joined with females for 2–3 oestrous cycles. Males are often rotated between groups of females and ‘follow-up’ males may be introduced for the final oestrous cycle. Such practices reduce the impact of any poor performing males. The effectiveness of mating can be monitored by use of mating harnesses or daily application of paint to the sternum of male animals. It is common for rams or bucks to develop lameness, injuries or other health problems during the mating period, hence regular inspection during mating is recommended. 7. Concluding remarks Careful management is necessary to ensure the reproductive success of any sheep flock/goat herd and to maximise the productive longevity of rams and bucks. Rams and bucks are frequently overlooked outside of the breeding period, but year-round attention to nutrition, parasite control and general disease control is important in keeping them healthy and sound for breeding. Pre-mating soundness examinations are inexpensive and relatively easy for assessing potential ability of a ram or buck to perform during the breeding period; they should be incorporated annually into the management of any flock. During the breeding period careful thought should be given to the
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appropriate use of males and the effectiveness of mating should be monitored. Conflict of interest statement The authors have nothing to disclose. References Allison, A.J., 1975. Flock mating in sheep. I: effect of number of ewes joined per ram on mating behaviour and fertility. N. Z. J. Agric. Res. 18, 1–8. Allison, A.J., 1978. Flock mating in sheep. III: comparison of two-tooth and six-tooth rams joined with different numbers of ewes per ram. N. Z. J. Agric. Res. 21, 113–118. Barwick, S.A., Kilgour, R.J., Fowler, J.F., Wilkins, J.F., Harvey, W.R., 1989. Ram mating performance in Border Leicesters and related breed types. 3: relationships of ram serving capacity, testis diameter, liveweight, breed and age with flock fertility. Aust. J. Exp. Agric. 29, 17–22. Blanchard, T.L., Varner, D.D., Bretzlaff, K.N., Elmore, R.G., 1991. The causes and pathologic changes of testicular degeneration in large animals. Vet. Med. 86, 531–536. Bulgin, M.S., 1992. Ram breeding soundness and SFT form. In: Soc. Therio. Ann. Mtg., San Antonio, pp. 210–215. Dunn, T.G., Moss, G.E., 1992. Effects of nutrient deficiencies and excesses on reproductive efficiency of livestock. J. Anim. Sci. 70, 1580–1593. Foster, R.A., Ladds, P.W., Hoffmann, D., Briggs, G.D., 1989. The relationship of scrotal circumference to testicular weight in rams. Aust. Vet. J. 66, 20–22. Fowler, D.G., 1984. Reproductive behaviour of rams. In: Lindsay, D.R., Peirce, D.T. (Eds.), Reproduction in Sheep. Cambridge University Press, pp. 39–46. Gouletsou, P.G., Fthenakis, G.C., 2010. Clinical evaluation of reproductive ability of rams. Small Rumin. Res. 92, 45–51. Jainudeen, M.R., Wahid, H., Hafez, E.S.E., 2000. Sheep and goats. In: Hafez, E.S.E., Hafez, B. (Eds.), Reproduction in Farm Animals. , seventh ed. Lippincott, Williams & Wilkins, Maryland, pp. 172–181. Kenyon, P.R., Morel, P.C.H., Morris, S.T., Burnham, D.L., West, D.M., 2006. The effect of length of use of teaser rams prior to mating and individual liveweight on the reproductive performance of ewe hoggets. N. Z. Vet. J. 54, 91–95. Kenyon, P.R., Morel, P.C.H., Morris, S.T., West, D.M., 2007. Effect of the age of rams on reproductive performance of ewe hoggets. N. Z. Vet. J. 55, 184–187.
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Kenyon, P.R., Morris, S.T., West, D.M., 2010. Proportion of rams and the condition of ewe lambs at joining influences their breeding performance. Anim. Prod. Sci. 50, 454–459. Knight, T.W., 1977. Methods for the indirect estimation of testes weight and sperm numbers in Merino and Romney rams. N. Z. J. Agric. Res. 20, 291–296. Knight, T.W., 1980. Onset of mating activity in Romney ewes after short periods of teasing. N. Z. J. Agric. Res. 23, 277–280. Lightfoot, R.J., 1968. Studies on the number of ewes joined per ram for flock mating under paddock conditions. III: the effect of mating on semen characteristics. Aust. J. Agric. Res. 19, 1043–1057. Lightfoot, R.J., Smith, J.A.C., 1968. Studies on the number of ewes joined per ram for flock mating under paddock conditions. I: mating behaviour and fertility. Aust. J. Agric. Res. 19, 1029–1042. Lino, B.F., 1972. The output of spermatozoa in rams. II: relationship to scrotal circumference, testis weight and the number of spermatozoa in different parts of the urogential tract. Aust. J. Biol. Sci. 25, 359–366. Martin, G.B., Oldham, C.M., Cognie, Y., Pearce, D.T., 1986. The physiological responses of anovulatory ewes to the introduction of rams – a review. Liv. Prod. Sci. 15, 219–247. Moule, G.R., Waites, G.M.H., 1963. Seminal degradation in the ram and its relation to the temperature of the scrotum. J. Reprod. Fertil. 5, 1–16. Rosa, H.J.D., Bryant, M.J., 2002. The ‘ram effect’ as a way of modifying the reproductive activity in the ewe. Small Rumin. Res. 45, 1–16. Rosa, H.J.D., Bryant, M.J., 2003. Seasonality of reproduction in sheep. Small Rumin. Res. 48, 155–171. Ruttle, J.L., Southward, G.M., 1988. Influence of age and scrotal circumference on breeding soundness examination of range rams. Theriogenology 29, 945–949. Sargison, N.D., 2008. Sheep Flock Health, A Planned Approach. Blackwell Publishing, Oxford, pp. 23–25. Thompson, L.H., Stookey, J.M., Giles, J.R., Thomas, D.L., 1990. Reproductive response of mature ewes of different breeds to teasing prior to mating. Small Rumin. Res. 3, 373–381. Tsakmakidis, I.A., 2010. Ram semen evaluation: development and efficiency of modern techniques. Small Rumin. Res. 92, 126–130. Vipond, J., Greig, A., 2007. Management and care of rams. In: Aitken, I.D. (Ed.), Diseases of Sheep. Blackwell Publishing, Oxford, pp. 61–65. Walkden-Brown, S.W., Restall, B.J., Taylor, W.A., 1994. Testicular and epididymal sperm content in grazing cashmere bucks: seasonal variation and prediction from measurements in vivo. Reprod. Fertil. Dev. 6, 727–736. Weimer, K.E., Ruttle, J.L., 1987. Semen characteristics, scrotal circumference and bacterial isolates of fine wool range rams. Theriogenology 28, 625–637.