Del Vecchio, R. P.

Neuendorff, Don A.

Randel, R. D.

Stahringer, R. C.

English

Texas A&amp;M Repository

    PUBLICATIONS 1990 THE ONSET OF PUBERTY IN THE BOVINE: UTERINE AND OVARYANHORMONAL INTERRELATIONSHIPSR. P. Del Vecchio, D. A. Neuendorff, R. C. Stahringer and R. D. RandelSUMMARYTwenty prepubertal Holstein heifers were utilized to determine the incidenceof abnormal estrous cycles during the onset of puberty in cattle. Upon observationof first behavioral estrus (d=O; 1st Estrus), daily blood samples were collected fromthe jugular vein until the heifers had experienced a minimum of 3 estrous cycleswith the last being of normal length (18 to 24 d). The average weight and age at1st Estrus was 549 ± 10.6 lb and 304.0 ± 7.5 days, respectively. Frequency ofabnormal length estrous cycles was greater (P < .02) during the first estrous cycle(30%; 1st cycle) and second estrous cycle (30%; 2nd cycle) compared to the thirdestrous cycle (0%; 3rd cycle). There was a greater (P < .05) incidence of abnormallylong estrous cycles compared to short cycles during the 1st cycle; whereas, shortcycles occurred more frequently during the 2nd cycle than long cycles. Theincidence of silent estrus was more frequent during the 1st cycle than the 2nd cycle(P < .07) or the 3rd cycle (P < .05). Behavioral estrus with inadequate corpusluteum formation occurred with greater frequency (P < .05) during the 1st cyclethan the 2nd cycle or 3rd cycle. In addition, behavioral estrus with elevatedprogesterone concentrations occurred in 10% of the heifers during the 1st cycle and2nd cycle; during the 3rd cycle, none of the heifers exhibited this behavior.Abnormally short or long estrous cycles, silent estrus and behavioral estrus duringelevated progesterone were observed in 45% of the heifers during the first 2 estrouscycles. These data demonstrate that there are anomalies which occur during the1st cycle and 2nd cycle of puberty. There appears to be a high incidence ofabnormally long and short estrous cycles along with silent and asynchronousbehavioral estrus as well as behavioral estrus with inadequate corpus luteumformation. Thus, it can be concluded that reproductive maturation continuesbeyond the occurrence of first behavioral estrus.INTRODUCTIONDetection of the first puberal estrus in heifers is generally considered to bethe point at which the animal has reached puberty. Conception rates, however,appear to be lower in heifers bred at their first spontaneous or induced estrus ascompared to the third estrus.215Abnormal estrous cycles and abnormal estrus activity may be contributingfactor involved in the decreased incidence of pregnancies occurring after breedingat the first behavioral estrus (1st estrus) as compared to subsequent estrus.The occurrence of a phenomenon termed nonpuberal estrus (NP estrus), hasbeen reported and is defined as instances of behavioral estrus in prepubertal heifersthat are not followed by ovulation and formation of a functional corpus luteum (CL;required for maintenance of pregnancy). Other researchers have concluded thatNP estrus is not an uncommon event, but NP estrus can bias the interpretation ofresults where behavioral estrus is the only criteria used to assign date of puberty.The objective of this study was to investigate the incidence of abnormallength (short and long) cycles and to evaluate silent and asynchronous behavioralestrus.PROCEDURESTwenty prepubertal Holstein heifers, born between March 1 and May 9,1987, were managed as a group and maintained on Coastal bermudagrass andryegrass pastures. The heifers were fed daily 6.1 to 8.0 lblhead of supplement (3parts corn : 1 part soybean meal) along with Coastal bermudagrass hay and tracemineral salt offered free choice which allowed for at least 1.5 lb of gain/day. Theheifers were weighed at 28 day intervals and within 24 hours after 1st estrus. Asterile marker bull was maintained with the heifers throughout the duration of thetrial to assist in detection of estrus.Heifers were observed for 30 minutes, four times daily for estrous activity.A heifer was considered to have been in estrus if she stood to be mounted by thebull and/or other heifers, or if mounting behavior was not observed (i.e., whenestrus occurred at night), more than one well defined mark along the back and tail-head area of the heifer by the bull was required.Blood samples were collected on a daily basis from the jugular veinbeginning at 1st estrus (d=O) and continuing until the heifer had experienced aminimum of three estrous cycles with the last being of normal length (18 to 24days). The blood samples were allowed to clot at 4°C overnight and were thencentrifuged to yield serum. The serum was stored at -20"C until radioimmunoassayfor progesterone concentration.RESULTSThe average weights and ages at 1st estrus were 549.7 ± 10.6 lb and 304.0216± 7.5 d, respectively, and were similar to the averages reported for Holstein heifersby other investigators. The occurrence of abnormal length estrous cycles « 17 to> 25 days) was more frequent (P < .02) during the first estrous cycle (1st cycle) andthe second estrous cycle (2nd cycle) than during the third estrous cycle (3rd cycle;Figure 1). This agrees with other researchers who reported that the occurrence oflong estrous cycles (25 to 57 d) was observed during the 1st cycle and 2nd cyclewhich caused the average length of the 1st cycle and 2nd cycle to be significantlylonger than subsequent estrous cycles. There was a higher incidence of long estrouscycles when compared to short estrous cycles during the 1st cycle; however, duringthe 2nd cycle, short estrous cycles were more frequent (P < .07) than long estrouscycles (Figure 1). The occurrence of silent estrus (as determined by hormoneprofiles) was more frequent during the 1st cycle than the 2nd cycle (P < .07) or3rd cycle (P < .05; Figure 2). The high incidence of silent estrus observed in thisstudy is similar to observations made by other researchers. Behavioral estrus withelevated serum progesterone concentrations (above 1 ng/ml) occurred in 10% of theheifers during the 1st cycle and 2nd cycle; while during the 3rd cycle, 0% exhibitedthis behavior (Figure 2). This phenomenon has not been previously reported.Although only 10% of the heifers exhibited this activity, the fact that the behaviorexists warrants mentioning. In addition, estrus followed by inadequate subsequentCL formation (NP estrus) occurred more frequently during the 1st cycle than duringthe 2nd cycle and the 3rd cycle (P < .05; Figure 3). The incidence of NP estrus wasnot as great in the present study as was reported by others where up to 62.8% ofbeef heifers exhibited NP estrus after their 1st estrus. Breed type has been shownto affect the occurrence of NP estrus which may account for the lower proportionof Holstein heifers demonstrating NP estrus. Collectively, abnormally short or longestrous cycles, silent estrus and behavioral estrus during elevated progesteroneconcentrations were observed in 45% of the heifers during the fIrst two estrouscycles.These findings support and lend additional evidence to the theory thatreproductive maturation continues beyond the 1st cycle. These data also indicatethat there are numerous behavioral and physiological anomalies that occur duringthe pubertal transition period. This suggests that a person should be cautiouswhen assigning a date of puberty to heifers where 1st cycle is the sole criteria.217Figure 1. Frequency of abnormal estrouscycles in Holstein heifers.THIRD0 SHORTEI LONG., , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ". ' , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " " 7'7'7'7'7',, , , , , ," " " " " " " " " " " ", , , , , , , , , , , ,FIRST SECONDESTROUS CYCLEo103040218Figure 2. Frequency of silent estrus andestrus during high progesterone.403010o0 ESTRUS WITH P4[3 SILENT ESTRUS·" " " " " ", , , , , ," " " " " "· ' , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " "· ' , , , , , ." " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , , , , , , , ," " " " " " " " " " " ", , , , , , , , , , , ,FIRST SECONDESTROUS CYCLE219THIRD302010oFigure 3. Frequency of estrus withoutformation of a corpus luteum." " " " " ", , , , , ," " " " " ", , , , , ," " " " " ". , , , , , ," " " " " ", , , , , ,, , , , , ,, , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " ", , , , , ," " " " " " " " " " " ", , , , , , """" " " " " " " " " " " ", , , , , , , , , , , ," " " " " " " " " " " ", , , , , , , , , , , ," " " " " " " " " " " ", , , , , , , , , , , ," " " " " " " " " " " ", , , , , , , , , , , ," " " " " " " " " " " ", , , , , , , , , , , ,FIRST SECONDESTROUS CYCLE220THIRD

The Onset of Puberty in the Bovine: Uterine and Ovarian Hormonal Interrelationships

https://oaktrust.library.tamu.edu/bitstream/1969.1/189984/1/article518.pdf

The Onset of Puberty in the Bovine: Uterine and Ovarian Hormonal Interrelationships

Abstract

Similar works

Full text

Available Versions

Texas A&M Repository

The Onset of Puberty in the Bovine: Uterine and Ovarian Hormonal Interrelationships

Abstract

Similar works

Full text

Available Versions

Texas A&amp;M Repository

Texas A&M Repository