Variables influencing ovarian cycles in post partum dairy cows

Variables Influencing Ovarian Cycles in Postpartum Dairy Cows C. J. Callahan, R. E. Erb, A. H. Surve and R. D. Randel J ANIM SCI 1971, 33:1053-1059.

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VARIABLES INFLUENCING OVARIAN CYCLES POSTPARTUM DAIRY COWS 1 C. J.

CALLAHAN,

IN

R. E. ERB, A. H. SURW 2 AND R. D. RANDEL3

Purdue University, La/ayette, Indiana 47907 VARIAN follicles may rupture and corO pora lutea (CL) may form after calving without prior evidence of estrus in milked cows. Among studies reported, the average period after calving to rupture of the first ovarian follicle (ovulation) ranged from 14 to 35 days and only 14 to 35% of the cows showed estrus at the beginning of the first ovarian cycle (Casida and Wisnicky, 1950; Menge et al., 1962; Morrow et al., 1966; Saiduddin et al., 1968; Marion and Gier, 1968; Wagner and Hansel, 1969). Growth and persistence of the CL may be subnormal and time from the first to the second ovulation averages about 15 days as compared to about 21 days from the second to the third ovulation (Morrow et al., 1966; Marion and Gier, 1968). These studies suggest that hormonal balances established to support pregnancy and its subsequent termination are gradually readjusted after calving to reestablish normal estrous cycles. The time period required after calving for readjustment by individuals is variable and appears to be influenced by a variety of environmental and genetic factors (Erb, Ehlers and Morrison, 1958a; Erb et al., 1958b; Labhsetwar, Tyler and Casida, 1963; Morrow et al., 1966; Marion and Gier, 1968). The objective of the present study was to survey the influence of such variables as twinning, time from calving to release of the fetal membranes (placenta) and gross clinical symptoms of uterine infection (metritis) on ovarian cycles, cystic ovaries, reproductive efficiency and reproductive hormones. Results of this study were briefly referred to in a recent review (Erb, Randel and Callahan, 1971a). Quantitative data on reproductive hormones are reported in a companion paper (Erb et aL, 1971b).

Experimental Procedure All heifers and cows calving between August 21 and October 21, 1966 at the Purdue Dairy Center were used in some phase of this study. There were 14 and 29 first calf heifers and 24 and 35 cows of the Red Danish and HoP stein-Friesian breeds, respectively. Eighty-nine of these animals were included in the prepartum study reported by Hunter et al. (1970) and the time from calving to release of the placenta was known for 82 following single births and for 10 following twin births. Based on clinical examinations, 65 cows scheduled for rebreeding were classified into postpartum groups consisting of 23 controls, 20 metritis, 10 cystic ovaries and 12 metritis plus cystic ovaries in combination. Each cow was assigned to only one group even though the abnormalities were not diagnosed at every rectal examination. The rationale for this approach was to isolate clinically normal cows (control group) from other conditions believed to adversely influence reproductive efficiency. The control group was never diagnosed as having metritis and CL were always detected after each estrus or after ovulation without estrus. The ovarian cycles all were 14 to 28 days in length. The metritis group consisted of cows showing fluid accumulation in the uterine horn(s) after 8 days postpartum and presence of pus in vaginal mucus discharged 13 or more days after calving. Such criteria would identify obvious cases of metritis or pyometra but would not detect all cows with low levels of infection. Cows not showing evidence of metritis were classified as cystic if ovarian follicles persisted in the absence of palpable CL for as long as 14 days, if ovulation was delayed more than 7 days after estrus or if CL were nondetectable for at least 7 days after ovulation. Marion and Gier (1968) have shown that diagnosis of cystic ovarian structures by palpation is accurate as compared to the micr0morphology of the ovary. Cows diagnosed cystic and showing evidence

1Journal-Paper No. 4387, Purdue Agricultural Experiment Station, Lafayette, Indiana 47907. Supported in part from a trust agreement between Purdue University and Normandy Farm, New Augusta, Indiana, Mr. and Mrs. Herman C. Krannert, owners. A contribution from Western Regional Project W-95. 2Present address: Sandoz Pharmaceuticals, Hanover, New Jersey. 3 Fellow, Purdue Research Foundation, Grant No. 5076. 1053

JOURNAL OF ANIMAL SCIENCE, vol. 33, no. 5

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CALLAHAN ET AL.

of metritis comprised a fourth group designated metritis-cystic. Beginning on day 8 after calving, rectal examinations were made at intervals to determine ovarian and uterine changes with special emphasis on follicular development and rupture, subsequent CL (corpus luteum) formation and evidence of metritis. The length and width of each ovary were recorded in centimeters as estimated by rectal palpation. Ovary size was summarized by multiplying length and width (cm2). Diameters of palpable follicles and CL were estimated and recorded in increments of 0.5 cm for those judged to be 1 cm or larger in diameter. Observations for estrous behavior were made at 2-hr. intervals. A cow was recorded in estrus based on mounting behavior and condition of the reproductive tract as determined by rectal palpation. Behavior characterized as estrus included attempts by the cow to mount other cows and partial acceptance of mounts by other animals as commonly seen during initiation of estrus. The cows were housed in two free stall barns, milked twice daily (0300 and 1500 hr.) in a milking parlor and fed outside from open feed bunks. All areas were well lighted and readily visible from working areas. Under the conditions available for observation, all cows showing signs of behavioral estrus for at least 2 hr. should have been detected. Before calving, the cows and heifers, managed as a group, were fed daily an average of 5 kg of concentrate containing 2% urea and low-moisture alfalfa-grass silage. After calving the same concentrate mixture was blended with the silage and fed ad libitum as a complete feed at a dry matter grain to forage ratio of 50:50 (high energy) for cows producing more than 22 kg of milk per day and at a ratio of 40:60 (medium energy) for cows producing less than 22 kg of milk per day. Corn silage was substituted for alfalfa-grass silage on October 7 and crude protein equivalent was maintained at earlier levels by addition of soybean meal. The complete high energy and medium energy mixtures, respectively, contained on a dry-matter basis about 14.5% and 12.6% crude protein and 42% and 35% of the crude protein was protein equivalent from urea. An earlier study had shown no differences in general health, milk production (Howard et al., 1968) and average services per conception (Howard, 1967) between least-cost rations containing similar

levels of dietary urea as compared to a control ration containing only protein from plant sources. An effect of dietary urea, if any, in the present study should have been similar for all animals unless incorporation with a forage base of alfalfa-grass results in a different response as compared to corn silage. In this case, the 16 cows which calved between October 7 and 21 only received corn silage forage after calving. The data were analyzed by analysis of variance (Steel and Torrie, 1960) and group averages were tested for significant differences (Kramer, 1956). Results and D i s c u s s i o n

Twinning. Twinning rate was 7% for 42 heifers and 14% for 50 cows. None of three heifers and five of seven cows producing twins retained the placenta from 60 to 192 hr. after calving. The placenta was not retained by three animals producing twin females (/~--7• hr.) and was retained following birth of one of two sets of twin males and four of five sets of mixed sex. Among 43 cows producing single calves, the placenta was retained 12 or more hours following 21% of the male birth and following 13% of the female births. The difference associated with sex of calf is in agreement with other data (Erb et al., 1958b). All twin calves were born alive 269 to 284 days after breeding. Among the I0 cows producing twins, eight developed metritis and four of these also were diagnosed cystic. Placenta. Six percent of the heifers and 24% of the cows (table 1) retained the placenta 12 or more hours after calving T A B L E 1. T I M E A F T E R C A L V I N G TO R E L E A S E OF F E T A L M E M B R A N E S B Y 39 H E I F E R S AND 43 COWS F O L L O W I N G B I R T H OF S I N G L E CALVES Fetal membranes released ( % ) Hr. after birth

Heifers

Cows

Total

2.0 to 2.9 3.0 to 3.9 4.0 to 4.9 5.0 to 5.9 6.0 to 6.9 7.0 to 7.9 8.0 to 8.9 9.0 to 9.9 10.0 to 11.9 12.0 1o 14.0 over 14.0

10 36 27 3 3 5 8 3 0 3 3

5 16 23 14 2 5 2 7 2 5 19

7 26 25 9 2 5 .5 5 1 4 11

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OVARIAN CYCLES IN POSTPARTUM TABLE 2. POSTPARTUM CLINICAL CONDITION OF COWS DELIVERING SINGLE CALVES AND RETAINING THE PLACENTA LESS THAN 7, 7 TO 12 AND MORE THAN 12 HR. AFTER CALVING Placenta release after calving (hr.) Groups

~7

7 to 12 >12

No. of cows observed 58 14 10 A Controls (%) 50 50 10 B Cystic (%) 15 0 0 C Metritis (%) 24 29 80 D Metritis and cystic (%) 11 21 10 E Totalcystic(B+D) (%) 26 21 10 F Totalmetritis (C+D) (%) 35 51 9O Reproductive efficiency (% calving) 75 63 67 No. bred ~ 48 8 9 a Some cows were cuIled for low production, mastiffs, poor udder conformationor used for nurse cows and were not rebred. (1274-20 hr.). Differences between heifers and older cows have been previously reported ( E r b et al., 1958b). Breed of animal and length of gestation were not significantly related to length of time the placenta was retained. B y 6 hr. postpartum, 76% of the heifers and 58% of the cows had released the placenta. Based on the accumulative frequencies b y hours after calving, a departure from a normal distribution was evident by 7 hr. p o s t p a r t u m (table 1). This suggests that retention of the placenta longer than 6 to 7 hr. m a y be abnormal. F i f t y percent of the animals releasing the placenta within 12 hr. p o s t p a r t u m were subsequently classified into the control group as compared to 10% of those retaining the placenta longer than 12 hr. (table 2). R a t e of metritis in the absence of ovarian dysfunction (cystic) was 80% in the latter group, as compared to 24 and 29%

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COWS

for animals retaining the placenta less than 7 and 7 to 12 hr., respectively. Reproductive efficiency based on subsequent calving was 63 and 67% for the two groups retaining the placenta 7 to 12 hr. and more than 12 hr., respectively, compared to 75% for the less than 7 hr. group (table 2). These results do not show t h a t cows retaining the placenta 7 to 12 hr. had subsequent reproductive histories differing from those releasing the placenta within 7 hours. T h e major differences were a lower rate of metritis and a higher reproductive efficiency for the less than 7-hr. group. Reproductive efficiency for twinning cows was 43% as compared to 67% for nontwinning cows retaining the placenta more than 12 hr., and 90% for controls (table 3). Cows showing evidence of having cystic ovaries with no other genital complications conceived as efficiently as the controls. I n comparison, cows having metritis averaged 50% and those suffering a combination of metritis and cystic ovaries averaged only 22% (table 3). There is little evidence in the present d a t a t h a t twinning in combination with metritis and retained placenta reduces conception efficiency more than metritis alone. Morrison and E r b (1957) reported that placentae are retained longer than 18 hr. b y 4 3 % of the cows following birth of twins which compares favora b l y to 50% in the present study. Services per conception following birth of twins are comparable to single births when the placenta is not retained and post calving pathological conditions are minimal ( E r b and Morrison, 1959). W h e n the placenta is retained there is some evidence t h a t reproductive efficiency is reduced even when pathological conditions are not observed ( E r b e t al., 1958b). T h e

TABLE 3. EFFECT OF POSTPARTUM CLINICAL ABNORMALITIES ON REPRODUCTIVE EFFICIENCY

Group

No. bred

First service conceptions (%)

Months in calving interval (% of animals) 15

Twinning 7 14 14 14 14 Retained placenta ~ 9 22 56 11 0 Control" 20 55 70 10 10 Metritis b 10 30 40 10 0 Cystic b 10 40 60 30 0 Metritis and cystic b 9 0 11 11 0 Total 65 32 48 14 5 Twinning cowswere omitted. b Cowstwinningand having retainedfetal membranewereomitted. e Either diagnosedinfertileor nonpregnant followingmating 6 or moremond~s after calving.

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Total % calving

Not conceiving (%) ~

43 67 90 50 90 22 67

57 33 10 50 10 78 33

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CALLAHAN E T AL.

increased rate of retained placenta by cows producing twins plus the markedly increased rate of metritis following retention of the placenta indicates that metritis is the primary cause of reduced fertility among such cows (table 3). Ovarian' Cycles. Initiation of postpartum ovarian cycles was not significantly different for cows producing twins or retaining the placenta more than 12 hr. as compared to those having metritis and cystic ovaries or only metritis, respectively. On this basis twinning and retained placenta were not included as variables for the summaries on ovarian cycles (table 4). This changed the number of cows in each subgroup and slightly altered the respective averages from results briefly summarized in a recent review paper (Erb et al., 1971a). Small, hard and firm CL of pregnancy were detected on the ovaries of five of 38 cows 8 days after calving. In the remaining cows both ovaries were not palpated at 8 days because they were out of reach. No effort was made to retract the uterus by use of instruments. Postpartum genital tract condition was associated with differences in time to first ovulation, first estrus, first 1.5 cm CL (all P < . 0 1 ) , first 1.0 cm follicle ( P < . 1 0 ) and length of the first ovarian cycle ( P < . 0 5 ; table 4). Time from calving to first ovulation by the control group was ( P < . 0 1 ) less as compared to the cystic and metritis-cystic groups. The metritis group showed the highest frequency of initial ovulations without detection of estrus (80%) and the longest interval to first estrus as compared to the control and cystic groups ( P ~ .01). The first ovarian cycle of the metritis group was longer than the other groups (table 4) and significantly ( P < . 0 5 ) different from TABLE

4. E F F E C T

OF

CLINICAL

that of the cystic group. The metritis-cystic group did not form 1.5 cm CL by 7 days after ovulation until 49__+5.0 days after calving which was significantly ( P ~ . 0 1 ) longer than the control (25+__1.5 days) and metrifis (30• days) groups. Moreover, following 67% of the first ovulations in the metritiscystic group, no CL were detected or were less than 1.5 cm in diameter as compared to 22 and 35%, respectively, for the control and metritis groups. Presumably the incidence of CL less than 1.5 cm at 7 days after ovulations was associated more with cystic ovarian changes (70%) than with metritis (35%). Follicles 1 cm in diameter were detected earlier (15• days) in the cystic group as compared to the other three groups (20 to 24 days), but only 40 to 50% ruptured within 9 days in the cystic and metritis-cystic groups as compared to 100% of the controls and 90% of those having only metritis. Compared to controls, the most obvious effect of metritis was an extended interval to first estrus ( P ~ .01). Similarly compared, the cystic group showed earlier follicle development, delayed follicle rupture, a longer interval to first ovulation ( P < . 0 1 ) and delayed formation of 1.5 cm CL ( P < . 0 1 ) . No cow in the cystic and metritis-cystic groups demonstrated persistent estrus during the first 8 weeks after calving. The first ovarian cycle exceeded 25 days for 42% of the cows in the metritis group as compared to 4, 0 and 17% of the control, cystic and metritis-cystic groups, respectively. First ovarian cycles were less than 18 days in 43% of the control group, 60% of the cystic group, 26% of the metritis group and 58% of the metritis-cystic group. The second and third ovarian cycles each averaged 23 days and

REPRODUCTIVE TRACT OVARIAN CYCLES

CONDITION

ON

POSTPARTUM

D a y s a f t e r c a l v i n g to o b s e r v a t i o n of f i r s t " Group

N

Ovulation Avg b

Control 23 Metritis (M) 20 Cystic (C) 10 MandC ~ 12 Total 65 G r o u p differences

Estrus % ~

17+---1.2 g 2 1 - + 1 . 6 g' ~ 2 9 - + 3 . 9 ~''~ 33"+-4.4 i 23--+1.4 P~.01

65 80 60 42 65

Avg 34• g 46-!---3.0~' 25-+3.0 ~ 37-----6.g g'h 37-+2.1 P~.01

CL--1.5

cm

Avg 25-+1.5 30-+2.3 39+3.7 49+'5.0 33-+1.8 P~.01

Avg g ~'~ u'~ i

Days from first to s e c o n d ovulation

Follicle--1 cm

20-I-2.3 24-+2.4 15-+1.2 20-+2.2 20-+1.0 P~.10

% '~ g'h g h g'h

Avg

100 90 40 S0

18-+1.3 24-+2.4 15-+1.8 20-+4.0

78

20-+1.2 P~.05

a Averages in columns with dissimilar superscripts (g, h, i) are significantly different ( P < . 0 5 to P < . 0 1 ) . i, Average+standard error. e Estrus not detected prior to ovulation. a Ovarian follicle 1 cm in diameter ruptured within 9 days after first detected by rectal examination. Diagnosed as having cystic ovaries subsequent to metritis.

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% r g'h g h g'h

32 33 23 8 24

OVARIAN CYCLES IN POSTPARTUM COWS groups were not significantly different, though the abnormal groups had a smaller percentage of cycles in the 18 to 25-day range (50%) than the controls (83%). Estimated Size o/Ovaries. Ovaries increased in size between 8 and 20 days after calving (P