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A 30-kDa heparin-binding protein named fertility-associated antigen (FAA) was identified in sperm membranes of beef bulls with greater fertility potential. In a survey of 2,191 beef bulls, 88% had FAA present in sperm membranes (FAA-positive), and 12% were FAA-negative. In the first study, 54 Santa Gertrudis and 51 Santa Cruz bulls were grouped (1 to 14 bulls per group) according to FAA profiles and were bred to 2,403 cows at ratios of 1 bull: 25 cows. Fertility for 14 groups of FAA-positive bulls averaged 88%, whereas three groups of FAA-negative bulls impregnated 79% of the cows. Thus, FAA-positive bulls were nine percentage points more (P < .01) fertile than FAA-negative bulls. In the second study, 2-yr-old Santa Cruz bulls (n = 26) were grouped according to FAA profiles and serving capacity. The fertility of the group of 12 high-serving-capacity, FAA-positive bulls was 87% of 270 cows. The group of six FAA-negative bulls with high serving capacity impregnated 78% of 143 cows. Among the groups of bulls with high serving capacity, FAA-positive bulls were nine percentage points more (P < .05) fertile than FAA-negative bulls. The group of eight FAA-positive bulls with low serving capacity impregnated the least (P < .01) percentage (69%) of 238 cows. Serving capacity of bulls should be considered when optimizing fertility potential. Among bulls with acceptable physical characteristics and serving capacity, determination of FAA profiles in sperm can be used as a tool to identify subfertile bulls.

No abstract

Presence or absence of three distinct bovine seminal heparin‐binding proteins (21–31 kDa) recognized in sperm extracts by a monoclonal antibody, M1, is a diagnostic indicator of fertility differences among bulls producing normal semen. We recently identified a 31 kDa fertility‐associated antigenin bovine seminal fluid as a unique DNase I‐like protein. We now report purification and identification of a 24 kDa seminal heparin‐binding protein (HBP‐24) recognized by M1. N‐terminal microsequence analysis of HBP‐24 purified from seminal fluid yielded 20 amino acid residues that displayed 90% identity to the N‐terminus of a bovine metalloproteinase inhibitor identified as tissue inhibitor of metalloproteinases‐2 (TIMP‐2). A single immunoreactive band migrating at 24 kDa was detected in Western blots of cauda epididymal sperm extracts following incubation with purified seminal heparin‐binding proteins and subsequent washing in vitro, indicating TIMP‐2 bound to sperm membranes. Expression of TIMP‐2 mRNA was detected by RT‐PCR in bovine bulbourethral gland, prostate, and seminal vesicles. Mobility of the 24 kDa heparin‐binding protein increased under nonreducing SDS‐PAGE to ∼ 21 kDa, characteristic of the reported molecular mass of TIMP‐2. To our knowledge, this is the first report of TIMP‐2 binding to spermatozoa and of TIMP‐2 mRNA expression in bovine accessory sex glands. These results corroborate previous reports regarding the site of production of heparin‐binding proteins that are related to bull fertility, and suggest that TIMP‐2 influences fertility of bulls, either through inhibition of metalloprotease activity in semen or via undefined activities independent of matrix metalloproteinase (MMP) inhibition. Mol. Reprod. Dev. 58:336–341, 2001. © 2001 Wiley‐Liss, Inc.

Trials were performed to determine the relationship of heparin-binding proteins (HBP) to fertility of bulls. Red Angus (142), Santa Gertrudis (59), Gelbvieh (59), and Santa Gertrudis x Gelbvieh (40) bulls were identified according to the presence or absence of the greatest affinity HBP (HBP-B5) on sperm membranes and in seminal fluid. Nine to 20 bulls with the same HBP-B5 profiles were assigned to pastures with Santa Gertrudis cows at a ratio of 1 bull:25 cows. Fertility for Group 1 (80 bulls with HBP-B5 in sperm membranes but undetectable HBP-B5 in seminal fluid, in six pastures) was 82% pregnant of 1,692 cows. Group 2 bulls (48 bulls with HBP-B5 detectable in seminal fluid and in sperm membranes, in four pastures) impregnated 67% of 919 cows. Fertility for Group 3 (37 bulls with HBP-B5 in seminal fluid but undetectable HBP-B5 in the sperm membranes, in three pastures) and Group 4 (56 bulls with undetectable HBP-B5 in seminal fluid and sperm, in four pastures) was 63% pregnant of 747 and 1,208 cows, respectively. Group 1 had an average of 17% greater fertility compared with Groups 2, 3, and 4 (P < .05). In conclusion, groups with the greatest affinity HBP-B5 in sperm membranes but not in seminal fluid had greater fertility than did groups with other HBP-B5 profiles.