Serving capacity tests for beef bulls

Sir:— I would like to commend Don Fraser on his letter in the New Zealand Veterinary Journal Jan/Feb. issue, in bringing to the attention of the profession a practice that was exceedingly offensive for me to read about.     

The knobbed acrosome defect in beef bulls

The knobbed acrosome defect was found at levels of 25 to 100 percent of spermatozoa from 16 of 2054 beef bulls. The incidence of this defect appeared to be particularly high in the Charolais breed. Pedigree analysis of some of the affected Charolais bulls indicated there may be a genetic predisposition for this sperm defect. In eosin-nigrosin stained semen smears the most common form of the abnormality was a flattened or indented apex of the sperm head. A refractile bead at the apex of the sperm head was seen less commonly. Electron microscopy of the spermatozoa from one bull showed that the abnormality was similar to the knobbed sperm defect previously described in Friesian bulls. A breeding trial confirmed that bulls producing spermatozoa with a high incidence of knobbed acrosomes are infertile.     

Breeding soundness examination of yearling beef bulls

Yearling beef bulls were subjected to a breeding soundness examination (BSE) at completion of performance testing programs at 4 locations over 5 years. Of 862 bulls, 80.1% were classified as satisfactory potential breeders, 7.3% as questionable potential breeders, and 12.7% as unsatisfactory potential breeders. Year (P less than 0.01), location (P less than 0.01), and breed (P less than 0.01) affected the percentage of bulls classified as satisfactory; age of the bulls did not affect this percentage. Adjusted mean scrotal circumference (SC) measurements were 31, 33.2, and 34.8 cm for bulls classified as unsatisfactory, questionable, and satisfactory (P less than 0.01), respectively. Of 109 bulls classified as unsatisfactory, 2.8% were so classified because of poor semen quality alone; 41.3% had no ejaculate in 4 separate electroejaculation attempts. Other abnormalities in these 109 bulls included reproductive tract infections (22%), persistent penile frenulum (16.5%), testicular abnormalities (8.3%), fibropapilloma (1.8%), hernia (1.8%), aplastic epididymis (1.8%), penile abnormalities (1.8%), pendulous sheath (0.9%), and eye abnormalities (0.9%). Age had a significant effect on SC in bulls at 3 locations and on percentage of normal cells, primary abnormalities, and secondary abnormalities as well as BSE score at 1 location. Percentage of primary and secondary abnormalities as well as SC were different across years at 2 locations, and percentage of normal and motile cells as well as BSE score were different across years at 1 location. Breed effects were significant for SC, percentage of primary abnormalities, and BSE score at 3 locations and for percentage of normal and motile cells at 1 location.     

Causes of copulatory failure in beef bulls

A cow in full standing estrus is required to assess a bull's ability to copulate. Insufficient libido is not involved if the bull sniffs the cow's vulva and attempts to mount. Blood or pus exiting the penis or prepuce indicates penile or preputial lacerations or other lesions. Rear foot or stifle lesions, seminal vesiculitis, traumatic reticulitis or lumbar spinal injuries may prevent the bull from mounting. Preputial stenosis, penile adhesions, desensitization, hematomas or deviations, peripreputial abscess, cavernosal shunts, insufficient penile length and occlusions of the cavernosal canals may prevent intromission after mounting.     

Observations on the Modified Serving Capacity Test for beef bulls

Over the period 1979-83, 466 beef bulls were examined physically and by Blockley's Modified Serving Capacity Test (M.S.C.T.). Seventy-eight bulls were diagnosed as unsound for breeding, of which 64 were detected by the M.S.C.T. Problems included locomotor abnormalities (6), low libido (14), penile deviation (33) and intromission failure (11). The animal welfare aspects of M.S.C.T. are discussed and its value in increasing herd fertility is illustrated with studies of two beef herds, which showed improvements of 4-5% in vetting in-calf rates after using the test.     

Observations on the modified serving capacity test for beef bulls

Over the period 1979–83,466 beef bulls were examined physically and by Blockley's Modified Serving Capacity Test (M.S.C.T.). Seventy-eight bulls were diagnosed as unsound for breeding, of which 64 were detected by the M.S.C.T. Problems included locomotor abnormalities (6), low libido (14), penile deviation (33) and intromission failure (11). The animal welfare aspects of M.S.C.T. are discussed and its value in increasing herd fertility is illustrated with studies of two beef herds, whichshowed improvements of 4–5% in vetting in-calf rates after using the test.     

Efficacy of ipronidazole against trichomoniasis in beef bulls

Preputial smegma samples from 195 beef bulls were collected repeatedly and cultured for Tritrichomonas foetus. Seventy-five (38.5%) of these bulls were positive for trichomonads on at least 1 culture. Sensitivity of the culture procedure (number of positive cultures/number of total cultures from known-positive bulls) was 81.6%. Storage of preputial smegma in lactated Ringer's solution at 5 C for 24 hours resulted in a 14% loss of sensitivity. Seventy-three of the 75 infected bulls were available for treatment and were alloted randomly to 2 groups. Bulls in both groups were treated with procaine penicillin (7,000 IU/kg, IM) for 2 days before ipronidazole treatment. Thirty grams of ipronidazole powder was dissolved in 60 ml of sterile water, and was given IM to group 1 bulls. Group 2 bulls were given a similar 30-g ipronidazole solution IM on day 1, and were given 15 g of ipronidazole dissolved in 30 ml of sterile water on days 2 and 3. Efficacy of treatment (ie, negative cultures of preputial smegma for trichomonads for 6 consecutive weeks after treatment) was 92.8% for the 42 bulls treated once and 100% for the 31 bulls treated 3 times.     

Sexual development in beef bulls following zeranol implants

Two trials were conducted to study the effect of zeranol implants on growth and sexual development of bull calves. Trial 1 compared the effects of implanting with 72 mg of zeranol at 48 d of age (branding), at 215 d of age, or at both times with nonimplanted control bulls. Implanting at branding resulted in decreased scrotal circumference, testicle weight and proportion of bulls that could produce an ejaculate at 14 mo of age (P less than .01). Implanting at 215 d of age had no effect on any of these traits. Growth rate was not increased by implanting at either time but was decreased (P less than .02) in animals implanted at both times when compared with control bulls. In trial 2, both bulls and steers were implanted with zeranol and compared with nonimplanted control bulls and steers. Thirty-six-milligram implants were given at 21, 103, 260 and 343 d of age. Scrotal circumference, testicle weight and serum testosterone concentrations decreased (P less than .01) and the occurrence of penis abnormalities increased (P less than .01) in implanted bulls compared with control bulls. By the time of slaughter, however, testosterone concentrations were equal in control and implanted bulls; and the difference in scrotal circumference was diminishing. This is interpreted as evidence that as the bulls get older, they can overcome the effect of the implants. Carcass weights were heavier in implanted steers than in control steers but were lighter in implanted bulls than in control bulls (P less than .02). Carcasses of implanted bulls had higher quality scores and more marbling than control bulls, but carcasses of implanted steers had lower quality scores and less marbling than control steers (both interactions, P less than .01). Implanting bulls with zeranol at an early age resulted in restricted sexual development but not in total sterility. Repeated zeranol implants throughout the growing and finishing phase enhanced carcass quality in bulls slaughtered at 14 to 16 mo of age.     

Scrotal circumference adjustment factors for age and weight differences in beef bulls

Scrotal circumference measurements were analyzed to develop appropriate adjustment factors for age and body weight differences in beef bulls. Age, body weight, and scrotal circumference measurements were collected on 863 Angus, 753 Polled Hereford, and 302 Simmental bulls from the Missouri tested bull sale, 1169 Polled Hereford bulls from the American Polled Hereford Association, and 465 Polled Hereford and 264 Simmental bulls from Nichols Farms in Bridgewater, Iowa. Within sources, data were subdivided into appropriate subsets and then each subset was statistically analyzed. Adjustment factors to remove differences in scrotal circumference due to age and body weight were developed for bulls of each of the 3 breeds studied.     

The effect of physical structure in maize silage-based diets for beef bulls

To investigate the influence of physical structure on zootechnical performances, four feeding regimens were evaluated with 52 Belgian Blue double-muscled bulls starting from 327 kg until slaughter (646 kg). All diets were fed ad libitum and consisted of concentrates and maize silage in different ratios. The structural value (SV), currently used in Belgium as an evaluator of physical structure in the diet for dairy cows, amounted to 0.95 (control group), 0.74 and 0.52 per kg dry matter for the treatments with a high (HSV), medium (MSV) and low (LSV) SV, respectively. The fourth group (LSVs) received the same diet as group LSV, but additional straw was provided ad libitum, as a possible corrector for a lack of physical structure. No significant differences were found for growth rate, intake and feed conversion data. However, between 600 and 650 kg, growth rate and intake of group LSV and LSVs tended to be reduced. The influences on the carcass quality were of minor importance. Remarkably, meat tenderness of the LSV group was improved (32.3 N) in comparison (p=0.08) with the other groups (42.6 N). The height of the rumen papillae was not affected by the diets. Histological examination of the ruminal epithelium revealed that the LSV group showed the severest morphological changes. Examination of the cross-sections of the digits showed no influence of the diet on the incidence of laminitis. From these results, it is concluded that maize silage-based rations with a SV of 0.74 provide enough structure for optimal zootechnical performances of finishing Belgian Blue double-muscled bulls.     

中国荷斯坦奶公牛肉用研究进展

奶公犊资源的充分利用,不仅能缓解国际市场上牛肉供应不足的紧张局面,而且可以满足广大消费者对高品质牛肉的需求。如何利用现有的奶公犊资源,借鉴国外先进的产业模式和饲养技术,构建我国特色的肉牛产业,成为当前养牛人关注的焦点。我国在奶公犊育肥利用上起步较晚,但随着牛源紧缺,围绕奶公牛生产的相关研究已经陆续展开,在犊牛肉生产技术、小牛肉生产技术、普通牛肉生产技术以及高附加值牛肉生产技术等4个方面取得了长足进展。本文就近几年中国荷斯坦奶公牛在这4方面的研究进展进行了综述。     

Long-term supplementation of lasalocid-sodium for beef bulls during grazing and subsequent finishing period

117 white-red beef bulls were involved to investigate the effect of lasalocid-sodium when fed either during the grazing period, or the finishing period, or during both subsequent periods. The ionophore was fed at 250 mg daily per head incorporated in 1 kg dry sugar beet pulp on pasture and at 65 mg per kg concentrate afterwards (corresponding with 27 ppm in the ration DM). The finishing diet consisted of maize silage ad libitum and 0.75 kg concentrate per 100 kg liveweight per day. On pasture lasalocid significantly increased daily gain form 0.6 to more than 0.7 kg, without affecting the grazed area per animal. During the finishing period growth rate was only slightly affected by lasalocid, but feed intake was reduced (P less than 0.05) and feed conversion improved (P less than 0.05). Feeding lasalocid permanently for more than 400 days did not reduce these positive effects. Cumulative daily gain, total feed intake per head and feed conversion were 1.12 kg, 2176 kg dry matter (DM) and 4.70 kg DM. These figures amounted to 1.05 kg, 2283 kg DM and 5.16 kg DM when no lasalocid was fed; 1.06 kg, 2141 kg DM and 4.87 kg DM when lasalocid was only fed during the finishing period and 1.09 kg, 2246 DM and 4.99 kg DM when lasalocid was only fed during the grazing period. Daily gains of 1.05 and 1.06 kg were significantly lower (P less than 0.05) than 1.12 kg. Most carcass data were unaffected, except fatness. The permanent feeding of lasalocid increased carcass fatness, mainly as the result of a higher final weight.     

Observations on spiral deviation of the penis in beef bulls

Premature spiral deviation of the penis was investigated in 1083 British breed beef bulls in 42 herds in Victoria (35) and Western Australia (7) by means of the serving capacity test. The herd prevalence was 60%. The prevalence of the defect at the initial test for all bulls was 10%. The prevalence in 635 polled bulls was 16% compared to a prevalence of 1 % in 448 horned bulls. The breed prevalence and the number of bulls tested per breed was Red Poll 27% (15), Murray Grey 25% (4), Poll Shorthorn 21 % (34), Angus 17% (415), Poll Hereford 10% (167) and Hereford 1 % (448). The difference between the last 2 breed types was highly significant (P<0.001). The prevalence of the defect increased from 0 to 30% over 9 years in one Victorian herd. The age of affected bulls varied from 2 to 11 years with most affected bulls aged from 3 to 6 years. Common ancestry was found between affected bulls in Western Australia, providing circumstantial evidence that it may be an inherited defect. None of the 103 affected bulls examined in this study had suffered obvious injury to the penis or prepuce. Eighty per cent of 56 affected bulls from Victoria had low serving capacity. Four bulls (2 from each state) with moderate to severe spiral deviation of the penis attained pregnancy rates of 43%, 33%, 3% and 3% respectively, in single sire mating trials. Recommendations for culling defective bulls are presented, based on the herd prevalence and severity of the defect in individual bulls.
It is concluded that bulls with moderate to severe spiral deviation of the penis have reduced fertility and remain permanently affected. The serving capacity test is a valuable diagnostic test for this serving defect in unhandled beef bulls. It is a common, although frequently undiagnosed disorder of polled beef breed bulls in Australia.