PREVALENCE OF ABORTION

Taranaki Daily News, 8 August 1930, Page 15

PREVALENCE OF ABORTION

RESEARCH IN TARANAKI METHODS USED IN MANAGEMENT. INVESTIGATIONS BY SCIENTIST. To discover the prevalence of abortion and sterility in North Taranaki dairy herds and to ascertain to what extent the breeding efficiency of a herd is influenced by the methods of management and maintenance adopted, practically every dairy farmer in the North Taranaki district was circularised early in September, 1929. Writing in the New Zealand Journal of Agriculture, Mr. W. Maurice Webster, B.Sc., M.R.C.V.S., of the live stock division of the Department of Agriculture, gives the result of the researches.

Information was sought on the following points by means of a questionnaire to the following effect: — (1) Acreage of farm. ' ' ■ . ' (2) Number of cows in herd. (3) Whether (a) cows were ' handserved—that is, bull kept separate and cows taken to him as required; or (b) bull was allowed to run with the herd. ,(4) Date on which breeding operations commenced.

(5) (In case of 3a). Number- of cows holding to first service. (6) (In case of 3b). Number of cows calving to full time or before August 31, 1929. (7) Number of cows which failed to become pregnant. (8) Number of "slips” or abortions during the winter. (9) Method of herd maintenance—(a) solely by home-reared heifers; (b) by outside purchases. (10) Whether the cows were given to ehewing bones, etc. One thousand four hundred and eightynine copies of this questionnaire were posted and 644 replies were received; 71 of the latter were discarded, mainly owing to incomplete or approximate figures being entered, and the remainder have been systematically tabulated. BREEDING DIFFICULTIES. Twenty-three herds were picked out in which the owners reported considerable breeding difficulty. The returns 1 showed only from 30 per cent, down to nil of the cows to have calved on or before August 31 and/or to have held to the first service. Sterility apparently existed in epidemic form in these herds, which will be dealt with later as a separate group. The remaining 550 returns were regarded as normal, with 50 per cent, and upwards of the cows calving on or before August 31. The returns were tabulated to contrast the following points: — (1) Herd management —hand service as opposed to allowing the bull a free run with the herd.

(2) Herd maintenance—’home-reared heifers-as opposed to outside purchases of cows and/or heifers. In a number of returns it was stated that the bull was running with the herd, but full service records had been kept as for hand service. Such returns, however, were not classified as handserved. Similarly, in regard to maintenance, where it was stated that the herd was chiefly maintained by home-reared heifers and only occasional! yby outside purchases, it was nevertheless classified under the latter heading. By means of a table Mr. Webster shows the average results obtained by the four alternative combinations of herd management and maintenance. In Group 1 (hand-served) there were 141 herds with home-reared heifers, the total number of cows in these herds being 5555. Of these 4108, or 73.9 per cent., calved on or before August 31, there were 234 abortions, or 4.2 per cent., while the number of empty cows was 215, or 3.9 per cent. Under the same group, but in which , outside purchases of stock were made,! there were 07 herds, with a total of i 4036 cows., 2776, or 68.7 per eent., calved on or before August 31, and the number of abortions was 260, or 6.4 per cent., and of empty cows 229, or 5.7 per cent. In Group II (bull running with the herd) there were 180 herds in which home-reared heifers were kept, the total ' number of cows being 7724, of which 360, or 4.7 per cent., aborted, and 213, or 2.7 per cent., were empty; while in the case of herds where outside purchases were made there was a total of 132, representing 6488 cows. Of these 368, or 5.7 per cent, aborted, and 288, or 4.4 per cent., were empty. “It should be stated here,” Mr. Webster continues, “that in the ‘hand-ser-vice’ group the figures show as ‘calved on or before August 31’ were actually the numbers shown in the returns as ‘holding to first service.’ The reason for this was that in the wording of the questionnaire the former question was unfortunately made’ optional in the case of hand-served herds from which exact breeding records were available. Both questions were, however, answered in respect of 85 herds, in which 2302 cows were returned as ’held to first service’ and 2291 as ‘calved on or before August 31.’ As a rule, where breeding ' commenced towards the end of October, these returns showed more cows ‘held to first service’ than ‘calved in August 31’, whereas when it was commenced early in October the reverse was the ease. In the aggregate, however, these discrepancies almost exactly balanced—a difference of 11 in 2302 records, representing only 0.4 per cent, error. In view of this it may be safely assumed that the total for the whole group which ‘held to first service’ was to all intents identical with the number ‘calved on or before August 31.’” Apart from this, the variations in the percentages in each 'column may be considered wholly significant, the probable margin of error in so large a cow population being extremely small. The results indicate quite definitely that hand service increases the average breeding efficiency of a herd, taking the numbers calving on or before August 31 as a basis. Group 1 (hand-served) gives ■ an average of 71.8 per cent., compared with 64.8 per cent, for Group IL, a difference of 7 per cent, in favour of hand-service. HERD MAINTENANCE. Breeding efficiency is also influenced i by the method of herd maintenance. In both groups there is a definite decrease in the breeding efficiency of the subgroup shown as maintained by outside purchases compared with that maintained by home-reared heifers. In addition to this general decrease in breeding efficiency in the “outside purchase” subgroups, there, is air increase in the num-

I ber of both “slips or abortions” and of "empty cows” to the extent of roughly 2 per cent. The relative figures for '"slips or abortions” in the sub-divisions of each group show little or no significant variation, but those for "empty eows,” although the relative variation between the sub-divisions of either group is approximately the same, are definitely less in Group 11. than in Group I. The explanation of this prob-. - ably lies, in the fact that breeding operations are carried on to a later date; in those herds in which the bull is running. In quite a number of instances the .date at which breeding ceased for the season was given in the space left for “Remarks” in the questionnaire. These replies showed that it was often the practice to give up attempts to breed about the end of January and to carry through any cows empty at that date in hand-served herds, whereas the bull was frequently allowed to run with the herd until.the end of February, or later. This would undoubtedly result in a few cows holding to service very • late in the season, and so lower the percentage for this group. THE BREEDING SEASON. The date on which breeding operations commenced for the season varied to some extent with the district. Coastal districts had a. tendency to begin early in October, while older and more backward inland districts, as a rule, were two or three weeks later. Replies were not furnished in every instance regarding this question, but •n 334 returns a definite date was given,' the results being as follow: — September 24-30 24 herds October 1-7 ............ 44 „ October 8-14 ........ .. 53 „ October .15-21 101 „ October 21-28 ...' 59 „ October 29-November 4 .. 53 ' „ In a few instances the date was later still, but such returns were included in the group of .71 discards mentioned earlier and not used.in the general analysis. . ' ■ i These figures show that there, is avery definite peak in the third week irt October. Cows bred from this date will calve from August 1 onwards. In the case of hand-served herds, it has already been shown that "holding, to first service” and “calving on or before August 31” were in the aggregate practically synonymous terms, and it is' a safe assumption that this statement holds good over the whole series of returns, since the great majority of cows which fail to hold to their first service must, obviously, calve subsequently to August 31. It follows, therefore, that any decrease in the percentage of cows calving on or before August 31 represents an increasing percentage which failed to hold to the first service. An analysis of some 700 individual breeding records has shown that, while a few cows return to the bull at a shorter interval than the normal three-, weekly period, a considerable number exceed this time, and the average interval over the whole series was 25 days. As a concrete example of the significance of the figures already quoted, the breeding efficiency (number of cows holding to first service) of a herd of 100 cows on the hand-service and homereared heifers system is 73.9 per cent., while a similar herd run with the bull and maintained by outside purchases shows only 61.8 per cent, efficiency, a difference of 12.1 per cent., or a loss on the production of 12 cows for a period of 25 days—a considerable item. Herd management and maintenance are both influenced to some extent by the size of the herd. Two hundred and thirty-eight hand-served herds averaged 40.3 cows per herd, while 312 herds with which the bull runs average 45.5 cows per herd. Of the 238 hand-served herds, 141 are maintained solely by home-reared 'heifers and average 39.4 cows per herd, while 97 maintained by outside purchases average 41.6. The 312 herds with which the bull runs show 180 maintained by home-reared heifers and averaging 42.9 eows per head, while the remaining 132 maintained by outside purchases average 49.1 cows per herd. Contrary to expectations, however, closer sub-division, leading to a better ■ utilisation of the land, is apparently not • a factor influencing the system of herdmanagement, adopted, The average size < of the farms comprising Group I. (hand- 1 service) is 117.7 acres, while that of Group n. is 133.3 acres. However, the i area required to support each cow in < Group I. is 2.92, and in Group 11. 2.93 : acres —practically a. constant. The in- s creased acreage per farm in Group 11. < (15.6 acres) compared with .Group I. is i exactly accounted for by the increased : average size of the herd in the former ] group (5.2 eows). ■. i

SIGNIFICANCE OF BONE-CHEWING. The importance of adequate mineral supplies in the diet of stock is universally admitted at the present time. The mineral requirements of various classes of stock vary to some .extent. Those of the modern daily cow are particularly high, especially as regards phosphortin. This is becoming more and more universally appreciated, as evidenced by the annually increasing application of phosphatic manure to dairy pastures. The significance of bone-chewing lies in the fact that about 84 per cent, of the mineral matter of bone consists of calcium phosphate, and when cattle arc grazing on minerally deficient pasture they instinctively endeavour to satisfy their craving for further phosphorus by eagerly chewing any bone which they can find. It is a well-known scientific fact that an extreme phosphate deficiency may reduce the breeding efficiency by bringing about a total inhibition of any sexual desire (heat periods). Such an extreme deficiency on dairy pasture is rare and was not reported in any instance.

However, bone-chewing is a safe indication of some degree of phosphatie deficiency, and the last query in the questionnaire was designed to ascertain to what extent a slight deficiency influenced the breeding efficiency. Seventy-two herds which reported bone-chewing gave a decrease of 4.5 per cent, in their breeding efficiency (number calving normally on or before August 31) compared with the remainder of the returns which reported no bonechewing. The figures for “abortions” and “empty cows” are both higher, al though only slightly. The differences are probably wholly significant, as the number of herds under each of the alternative methods of management and maintenance are proportionally almost identical with those of the complete series.

The increases of “abortions” and “empties,” though slight, are interesting in view of the fact that the United States Department of Agriculture has reported an increase of abortion and sterility on mineral-deficient pasture. In addition to the 72 herds whose owners reported bone-chewing, a further 48 farmers stated under “Ro-

marks” that this habit was formerly in evidence in their herds, but had ceased of recent years as a result of regular phosphatie top-dressing. APPARENT EPIDEMIC STERILITY. As stated earlier, returns from 23 herds revealed evidence of the existence of what appeared to be an epidemic form of sterility. These herds totalled 1289 cows, with 226, or 17.5 per cent., calving on or before August 31; 72, or 5.6 per cent., “slips or abortions ; and 129, or 10 1 per cent, “empty cows. A discussion of the specific cause of sp.ch outbreaks of sterility is outside the scope of the gresent article. It will suffice to state that it appears to be a definitely infectious disease, and not directly related to contagious abortion, since the percentages of abortions (o.u per cent.) is similar to the normal average (5.1 per cent.). Herd management does not appear to affect the incidence of such outbreaks, since approximately equal numbers were “hand-served” and “run with the bull. Herd maintenance, on the other hand, appears decidedly significant. Whereas in the 550 herds considered “normal 321 were maintained by home-reared heifers and 229 by outside purchases a ratio of 1: o.7—in this group the numbers are 8 and 15 respectively, a ratio of 1: 1.87. Purchases in the open market would therefore appear tp greatly increase the risk of introducing an epidemic form of sterility into a herd. Conclusions arrived at are: —

ll) In North Taranaki the proportions of cows calving on or before August 31, aborting, or failing to become pregnant, are approximately 68 per cent., 5 per cent, and 4 per cent, respectively, calculated on returns totalling 23,803 cows. (2) Hand service combined with herd maintenance by ’means of home-reared heifers results ’ in the highest average breeding efficiency, while the practice of allowing the bull to run with the herd, coupled with maintenance by means of sale-yard purchases, gives the worst results. (3) Irrespective of the method of herd management, maintenance by outside purchase results in decreased breeding efficiency, together with increased numbers of abortions and empty cows.

(4) The methods of herd management and maintenance adopted are influenced by the size of the herd; the smallei the herd the greater the tendency to hand srvicc and maintenance by homereared stock, and vice versa. (5) The size of the farm is not a factor influencing the system of management and maintenance. (6) Bone-chewing is a sign of mineral deficiency, and is reflected in a decreased general breeding efficiency, and possibly in increased abortion and empty cow rates.

(7) Epidemic sterility apparently exists in about 3.5 per cent, of herds, and its incidence seems to ; be markedly influenced by the system of herd maintenance, being nearly twice as prevalent in herds kept up by outside purchases (see also No. 3 above). (8) Apparent, epidemic sterility is not i. directly, connected vVitli contagious abor|‘tion, since the abortion rate in affected i herds is similar.;tp.',that ;

PREVENTION OF CRUELTY NEW PLYMOUTH SOCIETY MEETS. TREATMENT OF BOBBY CALVES. Mr. R. C. Hughes presided over a meeting of the New Plymouth branch of the” Society for the Prevention of Cruelty to Animals yesterday, when there were also present: Mesdames Martin, Ridling, Miss Hammer ton, Messrs. Shimmins, Grace and Tippins (inspector). The inspector’s report elated that owina to the plentiful supply of feed, cattle were in good order. Regarding the bobby calf question he was satisfied that the farmers themselves were largely responsible for any cruelty. At Lepperton, on July 31, he had eeen two trucks of bobby calves on the train from Hawera and Normanby.. The calves had been in the trucks all night and, as the weather had been cold, he reported, the matter to the president of the society. The same day he had travelled on the •lorry which picked up bobby calves, and on several occasions had forbidden the driver to pick up calves which were not three days’ old. He considered that tnis was the only way to ascertain how the ealven were being treated. Mrs. Martin stated that the proposal of the Auckland society to provide at a small cost lethal chambers for ;he painless destruction of small animals Should be considered. She -uggested that, • as interest in the essay competitions was waning, the Colvill memorial fund could, be diverted for the purchase of one of these .chambers and its upkeep. The suggestion was adopted and the secretary was instructed to write, ior particulars, of the cost. . • . -< The chairman reported that he had attended the conference at Wellington; He-gave a brief resume of the proceedings. A donation of £5 towards the funds of the society was received from Mrs. Earp. She was accorded a vote of thanks.