Higher Sperm Concentration Research Articles

Fertility of ram spermatozoa frozen by the pellet method. 3. The effects of insemination technique, oxytocin and relaxin on lambing.

Summary. A series of five experiments was conducted to examine ewe fertility following insemination with ram spermatozoa frozen by the pellet method. With thawed semen of low concentration and relatively poor quality, fertility was very poor with an overall non-return rate of 5·6% (269 ewes). Following insemination with thawed semen of low and high sperm concentration (0·5 versus 1·5×109 motile cells/ml) the proportions of ewes lambing were 23·7 and 43·8% respectively. There was no difference in the proportion of ewes lambing when the inseminate volume was reduced from 0·3 to 0·1 ml (Exp. 2, dilute semen) or from 0·15 to 0·05 ml (Exp. 3, concentrated semen). Two inseminations gave higher fertility than a single insemination (Exp. 2, 38·8% versus 22·6%; Exp. 3, 53·0% versus 39·7%) but the magnitude of the response varied according to both the time of insemination and the concentration and volume of the inseminate. High doses of oxytocin (5 or 10 i.u., i.m.) depressed the proportion of ewes lambing and relaxin (100 to 12,500 guinea-pig units/ewe) did not affect the depth to which the inseminating pipette could be inserted into the cervix. Overall lambing results (percentage of ewes lambing) for Exps 2, 3, 4 and 5 were 30·5% (266 ewes), 46·3% (231), 49·3% (69) and 27·5% (291) respectively, whereas results for the best treatment combinations in these experiments were 61·9%, 56·7%, 64·7% and 40·4%.

EVALUATION OF SEMEN FROM YOUNG BEEF BULLS

Semen was collected over a 30-day period from 18 yearling beef bulls, nine Herefords and nine hybrids. Average age at the start of the test was 380 ± 20 days. A total of 112 attempted collections resulted in 94 samples. Fifty percent of ejaculates were considered acceptable for freezing from Herefords and 79% from hybrids, respectively. The hybrid bulls produced significantly more semen per ejaculate (3.3 vs. 2.2 ml), higher sperm concentration (1092 × 106 vs. 657 × 106 per ml), higher sperm numbers per ejaculate (3,834 × 106 vs. 1,499 × 106) and higher total motile sperm per ejaculate (1,999 × 106 vs. 669 × 106). Bull-within-breed variance was significant for semen volume, concentration, initial motility and progressive motility. Progressive motility was in favor of semen from the hybrid bulls but was not statistically significant (48% vs. 36%). It is suggested that the superiority of the hybrid bulls was related to earlier onset of puberty. The trial also suggests that useable semen for progeny test purposes can be obtained soon after bulls reach one year of age.

Protein Levels in Growing Diets and Reproductive Performance of Cockerels

Two experiments were conducted with Single Comb White Leghorn cockerels to determine the effect of dietary protein during the growing period on sexual maturity and various reproductive characteristics. Dietary protein levels of 16.0, 9.0, 6.75 and 4.5% were fed beginning when the cockerels were 9 weeks of age and 7 weeks of age in experiments 1 and 2, respectively. A 17% protein breeder diet was fed from 23 weeks until 37 weeks of age. Body growth was depressed with each decrease in dietary protein. The 4.5% protein level approximated a maintenance diet. Sexual maturity was delayed in the low protein groups, without apparent permanent damage to the reproductive system. After the recovery diet had been fed for 7 weeks, there was little difference between dietary groups in the number of birds producing sperm or in semen scores. By the end of the recovery period the low protein groups had higher sperm concentrations and greater testes weights. Fertility was higher in the 9.0 and 6.75% protein groups than in the 16.0 and 4.5% protein groups at the end of the recovery period. Hatchability of fertile eggs was not affected by protein levels during the growing period.

Reproductive Capacity of Dairy Bulls. V. Detection of Testicular Deficiencies and Requirements for Experimentally Evaluating Testis Function from Semen Characteristics1,2

Summary Six ejaculates per week using intensive sexual preparation (6×) were collected from eight 2.5-yr.-old Holstein bulls for 5 wk. before unilateral vasectomy. Daily sperm output (DSO) averaged 4.58 billion and was correlated with paired testes weight at slaughter (+0.97). First ejaculates consistently contained a higher sperm concentration and more total sperm than second ejaculates. After unilateral vasectomy, two bulls were placed on sexual rest, three on two ejaculates per week (2×), and three on eight ejaculates per week (8×) for 20 wk. Even with the 50% decrease in potential sperm output resulting from unilateral vasectomy, sperm concentration (1.07 billion/ml) and total sperm per ejaculate (4.99 billion) for the 2× bulls were essentially normal. However, at the higher frequency (8×), these semen characteristics were clearly deficient (0.63 billion/ml and 1.90 billion). Four requirements suggested for detecting deficiencies in testicular function or for estimating daily sperm production on the basis of DSO under experimental conditions are: (a) high frequency of ejaculation with intensive sexual preparation, (b) short, uniform interval between collections, (c) pre-experimental stabilization of extra-gonadal sperm reserves and rate of sperm resorption, and (d) adequate duration of the experimental period. If sexual activity is adequate, these requirements are met best by collection of two ejaculates daily, preceded by intensive sexual preparation, for an eight- to ten-day pre-experimental period followed by ejaculation at the same frequency for a 2- to 8-wk. experimental period.

INVESTIGATION OF THE FERTILIZATION INHIBITING ACTION OF ARBACIA DERMAL SECRETION

1. Sperm washed from Arbacia dermal secretion fertilize eggs as readily as sperm washed from sea water. 2. Eggs washed from Arbacia dermal secretion do not fertilize as readily as controls. At best such eggs require high sperm concentrations to achieve fertilization. In some experiments the treated eggs show a marked cleavage delay. It is concluded that the dermal secretion inhibits fertilization by action on the egg, not on the sperm. 3. Addition of dermal secretion to eggs several minutes after insemination has no effect on the development of the eggs. Similar treatment a few seconds after insemination results in arrest of fertilization membrane elevation and sperm penetration. The dermal secretion also inhibits the formation of blebs in inseminated oocytes. It is concluded that dermal secretion inhibits by blocking an initial stage(s) in fertilization. 4. Jellyless (acid-treated) eggs fail to fertilize after treatment with dermal secretion. They have undiminished sensitivity to the inhibiting action of the dermal secretion. 5. Proteolytic enzyme-treated eggs are relatively insensitive to the inhibitor. They fertilize as readily as controls after treatment with dermal secretion, provided they are washed free of this inhibitor. They fail to fertilize if inseminated in dermal secretion. 6. The dermal secretion has undiminished fertilization inhibiting action in the presence of an excess of fertilizin. 7. The experiments suggest that the dermal secretion inhibits fertilization by combining with some egg substance that is essential for fertilization of the normal egg. The egg substance is apparently not the sperm isoagglutinin, fertilizin. Treatment of the egg with proteolytic enzymes eliminates the essential egg substance and simultaneously exposes an alternative pathway to fertilization. The latter is reversibly inhibited by dermal secretion.

Relation of Nutrition to Growth and Breeding Performance in Dairy Bulls. I. Alfalfa Hay Rations

Summary Four bulls, two each purebred Jersey and Holstein, fed a basal ration of alfalfa hay containing between 14 and 15 per cent crude protein, disodium phosphate, salt, and potassium iodide solution after 5 to 7 months of age and until disposal at 32 to 41 months of age, grew at a 10 to 15 per cent below normal rate until about 2 years of age. Semen samples showed more desirable characteristics after 18 months of age than before. All bulls proved fertile on service at from 24 to 40 months of age. Two bulls, one each purebred Jersey and Holstein, fed the basal ration plus a daily supplement of one pound each of skim milk powder and oat groats after 7 months of age, grew at a normal rate. They produced semen with more desirable characteristics, especially up to 18 months of age, as compared with the bulls fed the basal ration. The bulls proved fertile on service. Jersey bulls produced a smaller volume of semen with higher sperm concentration compared to Holsteins. The total sperm per ejaculation, averaging for the individual animals between 4 and 5 1 2 billion, the average initial motility and the original pH of the semen was not greatly different for the two breeds. A higher percentage of abnormal forms, particularly tail deformities, was found in semen from Jersey bulls, but the number was not usually high enough to characterize the semen as of poor quality. Sixty-seven samples of semen with excellent original motility, disregarding breed and age, measured 5.4 cc, showed a sperm concentration of 1,120,000 per cmm., had 11 per cent abnormal spermatozoa and in 70 per cent of the samples gave initial pH readings between 6.40 and 6.80.