Br. vel. }. ( 197 7), 133,635
THE EFFECTS OF BODY WEIGHT CHANGES ON FERTILITY DURING THE POST-PARTUM PERIOD IN DAIRY COWS By P. C. YOUDAN * AND ]. O. L. KI NG
University of Liverpool, Veterinary Field Station, Neston, W irral, Merseyside
SUMMARY
T he results of the fortnightly wc:ighings of974 cows kept on 11 Cheshire farms from calving until diagnosed as pregnant are presented. The ranges of body weight loss, the number of days to maxim um weight loss and to service are given. The correlations between body weight changes and fertility are recorded as long term and short term stud ies. INTROD U CTION
The fact that body weight changes occur in mature dairy cows during lactatio n has been known for many years, b ut little significance was attached to these cha nges until co mparative ly recently. McClure (1961 ) showed that cows wh ich los t least weight after calving and were gaini ng weight at the time of service had a higher chance of conception to first service than other cows whi ch exhibited a slower recovery of body weight during earl y lactati on. Simi larly King (1968 ) found tha t 98 Ayrshire cows which gained weig ht over the service period had a 77 ·6% conception rate to first service, whereas 8 1 cows which lost weigh t had only a 16% concep tion rate to first service, but the res ults were not statistically sign ificant. Moller & Shannon (197 2) studied the records of 3658 matings, a nd demonstrated a statistically significant correlation between cows which gained more than 2% of their original body weight over the service period and fertility, as opposed to cows which gained less than 2% of their body weight or sh owed a body weight loss. Boyd (J 972 ) demonstrated a beneficial effect of body weigh t gain on fertility rate, but the results were not statistically significant. MATERIALS AND METHODS
During the winter and spring periods from September 1970 until July 197 3,9 74 cows were weighed fortnightly from calving until diagnosed as pregnant by rectal palpation on II Cheshire dairy farms . Most of these farms were situated in the Wirral and others were in the Tarporley region. Six of the farms were stocked with Friesian cows (B, C, 0, E, F a nd K), three of the farmers kept Friesians and Ayrshires and crosses between • Present address : Dalgety Crosfields Ltd ., Aston Mi ll , Aston, Na ntwich, Cheshire.
636
BRITISH VETE RI NA RY JO UR NAL , 133 , 6
these breeds (A, G a nd J ), one farm er bred J ersey cattle (J ) a nd the other b red Guernseys (H ). On each farm the weighing process LOok place a t the same time each fortn ig ht in order LO reduce to a minimum differences in th e weights due LO variatio ns in the amount of ingesta in the alimentary canal. As the survey progressed all the inseminati o ns were tabulated as either successful or not su ccessful.
RESULTS AND DISCUSSIO
Ranges oJbody weight loss A grap h was drawn for each animal showing th e weight reco rd ed against da ys a fter pa rturition . Eighty-six of the cows were recorded as barren and so 888 curves were constructed. So me he ife rs did not exhibit a weig ht loss a nd some cows did not start LO gain weight in the peri od between calving and success ful service. Five hundred and eightye ight (66%) of the cows and heifers lost weight during the p ost-parturient peri od and subsequently sho wed a weight gain during the recording p eriod. Th e average body weight loss in thi s gro up was 11 3 lb , that is 9 ·6% of the first reco rded weight after calving . Obviously this figure wou ld have been lower if a ll the cows had been included. Hodges (1966) using a different me thod demonstrated a weight loss of 25 lb, 60 days after ca lving in dairy cows. Number oj days to maximum weight loss From th e initial da ta this figure was found LO be 65 days, being a very similar figure to that reco rd ed by Hodges (1966 ), a nd the herd means in most cases fell within th e range o f 50 LO 70 days. Number oj days to first service For the 66% of the cows considered the average number of days LO first service was 72, but in no herd was the standard deviation less than six indicating the large range of the data . Obviously, on average, the cows would have b een gaining we ight before service, beca use lIIaximum weight loss occurred 65 days after calving, but owing to the large sta ndard deviat ions many cows were sti ll losing weight over the service period. T hu s if t he wei g ht loss co uld be reduced , or th e first service delayed , a n improvement in th e first servi ce non-return rate would seem to be possible. Correlations between body weight change and fertility Initia ll y th e cow weight data was set out in co lumns as shown in Table I. These li gures indicated tha t th e cows which were gaining weight over th e service period or 14 days had a higher p ercentage or success ful services than did those cows which were losing weight. Also, the cows which were gai ning weight had a sma ll er number or services per concep tio n . After th is initial stud y the figures were subjected LO more stringent statistical tes ts. These tests varied fi-OITI year LO year as th e work progressed and different relationships were demo nstrated .
FE RTILITY I N DAIRY COWS
637
TABLE I SE RV ICE DETAILS OF 888 WEIG H T PROF I LES , THE COWS BEING D IV ID ED I NTO THOSE W HI CH WE R E GA I NING I N WEIG HT AND T H OSE W HI C H WERE LOS I NG WE I GHTATTHE TIME OF SE RV I CE
1970- 71
1971-72
1972-73
1970-73
Cows gaining weight Success ful servi ces (%) No. o f" services pel' co n ceptio n
56 I · 77
60 1·66
68 1·48
62 1·6 1
Cows Losing weight Successful services (%) No . o f" servi ces per co nception
47 2· 12
46 2· 18
49 2·04
47 2· 11
1970to 7 1
First th e da ta from the we ighings were examined to check the rela ti o nships between long-term livewe ight change and ferti li ty, a nd short-term liveweight change and ferti lity. By plotting th e liveweights o f a few cows it was fo und that th e seco nd d egree po lynomia l regressio n equati o n Yx =a+ bx + cx 2
gave the best Ilt to the da ta, Y x = liveweight in lb at x days a fter ca lving. A lo ng term livewe ight cha nge was d efined a s th e ta ngent to th e curve a t th e da te o f insemina ti o n, wh ereas a sho rt-term liveweight change was d efined a s the daily change in weig ht between th e two we ighing occas io ns straddling th e inseminati o n . An es tim ate of random va ria ti on (error) between th e two types o f liveweight cha nge a t service was calculated, the res ults of which a re shown in Tab le II .
TABLE II ANALYSES OF VA RI ANCE OF L ONG,TE R M AND SHO RT , T ER M LIVE W E I G H T C HA NGES
Mean squares Source of variation
H erds Co ws Error
THE EFFECTS OF BODY WEIGHT CHANGES ON FERTILITY DURING THE POST-PARTUM PERIOD IN DAIRY COWS By P. C. YOUDAN * AND ]. O. L. KI NG
University of Liverpool, Veterinary Field Station, Neston, W irral, Merseyside
SUMMARY
T he results of the fortnightly wc:ighings of974 cows kept on 11 Cheshire farms from calving until diagnosed as pregnant are presented. The ranges of body weight loss, the number of days to maxim um weight loss and to service are given. The correlations between body weight changes and fertility are recorded as long term and short term stud ies. INTROD U CTION
The fact that body weight changes occur in mature dairy cows during lactatio n has been known for many years, b ut little significance was attached to these cha nges until co mparative ly recently. McClure (1961 ) showed that cows wh ich los t least weight after calving and were gaini ng weight at the time of service had a higher chance of conception to first service than other cows whi ch exhibited a slower recovery of body weight during earl y lactati on. Simi larly King (1968 ) found tha t 98 Ayrshire cows which gained weig ht over the service period had a 77 ·6% conception rate to first service, whereas 8 1 cows which lost weigh t had only a 16% concep tion rate to first service, but the res ults were not statistically sign ificant. Moller & Shannon (197 2) studied the records of 3658 matings, a nd demonstrated a statistically significant correlation between cows which gained more than 2% of their original body weight over the service period and fertility, as opposed to cows which gained less than 2% of their body weight or sh owed a body weight loss. Boyd (J 972 ) demonstrated a beneficial effect of body weigh t gain on fertility rate, but the results were not statistically significant. MATERIALS AND METHODS
During the winter and spring periods from September 1970 until July 197 3,9 74 cows were weighed fortnightly from calving until diagnosed as pregnant by rectal palpation on II Cheshire dairy farms . Most of these farms were situated in the Wirral and others were in the Tarporley region. Six of the farms were stocked with Friesian cows (B, C, 0, E, F a nd K), three of the farmers kept Friesians and Ayrshires and crosses between • Present address : Dalgety Crosfields Ltd ., Aston Mi ll , Aston, Na ntwich, Cheshire.
636
BRITISH VETE RI NA RY JO UR NAL , 133 , 6
these breeds (A, G a nd J ), one farm er bred J ersey cattle (J ) a nd the other b red Guernseys (H ). On each farm the weighing process LOok place a t the same time each fortn ig ht in order LO reduce to a minimum differences in th e weights due LO variatio ns in the amount of ingesta in the alimentary canal. As the survey progressed all the inseminati o ns were tabulated as either successful or not su ccessful.
RESULTS AND DISCUSSIO
Ranges oJbody weight loss A grap h was drawn for each animal showing th e weight reco rd ed against da ys a fter pa rturition . Eighty-six of the cows were recorded as barren and so 888 curves were constructed. So me he ife rs did not exhibit a weig ht loss a nd some cows did not start LO gain weight in the peri od between calving and success ful service. Five hundred and eightye ight (66%) of the cows and heifers lost weight during the p ost-parturient peri od and subsequently sho wed a weight gain during the recording p eriod. Th e average body weight loss in thi s gro up was 11 3 lb , that is 9 ·6% of the first reco rded weight after calving . Obviously this figure wou ld have been lower if a ll the cows had been included. Hodges (1966) using a different me thod demonstrated a weight loss of 25 lb, 60 days after ca lving in dairy cows. Number oj days to maximum weight loss From th e initial da ta this figure was found LO be 65 days, being a very similar figure to that reco rd ed by Hodges (1966 ), a nd the herd means in most cases fell within th e range o f 50 LO 70 days. Number oj days to first service For the 66% of the cows considered the average number of days LO first service was 72, but in no herd was the standard deviation less than six indicating the large range of the data . Obviously, on average, the cows would have b een gaining we ight before service, beca use lIIaximum weight loss occurred 65 days after calving, but owing to the large sta ndard deviat ions many cows were sti ll losing weight over the service period. T hu s if t he wei g ht loss co uld be reduced , or th e first service delayed , a n improvement in th e first servi ce non-return rate would seem to be possible. Correlations between body weight change and fertility Initia ll y th e cow weight data was set out in co lumns as shown in Table I. These li gures indicated tha t th e cows which were gaining weight over th e service period or 14 days had a higher p ercentage or success ful services than did those cows which were losing weight. Also, the cows which were gai ning weight had a sma ll er number or services per concep tio n . After th is initial stud y the figures were subjected LO more stringent statistical tes ts. These tests varied fi-OITI year LO year as th e work progressed and different relationships were demo nstrated .
FE RTILITY I N DAIRY COWS
637
TABLE I SE RV ICE DETAILS OF 888 WEIG H T PROF I LES , THE COWS BEING D IV ID ED I NTO THOSE W HI CH WE R E GA I NING I N WEIG HT AND T H OSE W HI C H WERE LOS I NG WE I GHTATTHE TIME OF SE RV I CE
1970- 71
1971-72
1972-73
1970-73
Cows gaining weight Success ful servi ces (%) No. o f" services pel' co n ceptio n
56 I · 77
60 1·66
68 1·48
62 1·6 1
Cows Losing weight Successful services (%) No . o f" servi ces per co nception
47 2· 12
46 2· 18
49 2·04
47 2· 11
1970to 7 1
First th e da ta from the we ighings were examined to check the rela ti o nships between long-term livewe ight change and ferti li ty, a nd short-term liveweight change and ferti lity. By plotting th e liveweights o f a few cows it was fo und that th e seco nd d egree po lynomia l regressio n equati o n Yx =a+ bx + cx 2
gave the best Ilt to the da ta, Y x = liveweight in lb at x days a fter ca lving. A lo ng term livewe ight cha nge was d efined a s th e ta ngent to th e curve a t th e da te o f insemina ti o n, wh ereas a sho rt-term liveweight change was d efined a s the daily change in weig ht between th e two we ighing occas io ns straddling th e inseminati o n . An es tim ate of random va ria ti on (error) between th e two types o f liveweight cha nge a t service was calculated, the res ults of which a re shown in Tab le II .
TABLE II ANALYSES OF VA RI ANCE OF L ONG,TE R M AND SHO RT , T ER M LIVE W E I G H T C HA NGES
Mean squares Source of variation
H erds Co ws Error
