LETTERS TO THE EDITOR

SELENIUM AND LOWERED REPRODUCTIVE EFFICIENCY IN PIGS

At a large commercial piggery close to Sydney in New South Wales the conception rate, farrowing to first service, had declined by approximately 10% in the early 1970’s. Examination of records showed that most of this problem was confined to the maidens or gilts. As selenium (Se) salts have been demonstrated to have a dramatic effect in enhancing ewe fertility (Hartley 1964), it was considered that this trace element might also improve female fertility on this piggery.

The piggery on which the trials to be described were carried out was newly constructed and consisted of four identical self-contained units each housing approximately 500 breeding females. The pigs were Large White x Landrace and in each unit approximately one third of the females were gilts, the remainder being second to sixth litter sows. A11 units had identical feeding and managemental regimes, the only difference being that each unit employed different boars and different staff.

Two controlled trials were carried out in 1974 through 1975. In the first trial the conception rates were compared between gilts receiving and not receiving Se prior to mating and in the second trial older sows were also included. Trial I - In this trial all gilts selected for mating in units 1 and 2 were injected with 2.5 mg Se (as sodium selenite in distilled water) by the subcutaneous route (s/c) at selection for entry into the breeding unit, at mating (approximately 6 to 8 weeks later) and within the last week of gestation. All gilts entering units 3 and 4 served as undosed controls. At this stage the gilts were 26-35 weeks old. The trial commenced at the beginning of January 1974 and continued for 18 weeks. Detailed records were taken and these are summarized in Table 1.

The results indicate that at the dose level used Se had a significant effect ( ~ 2 = 15.7, p < 0.001) in increasing the conception rate of gilts to first service. The figures used to assess fertility include only the numbers of gilts farrowing to the first service. The results for re-mated

gilts are not included. Other effects were minimal. AS different boars were used in each unit it is possible that a boar effect could have influenced the fertility between units, but no boar in use was known to be of reduced fertility. Trial 2 - Tn view of the beneficial effects of Se to gilts in the first trial a second controlled trial was set up to compare the effects of Se on both gilts and second litter sows and older. Unit 4 was chosen as this had the poorest conception rate in the gilt trial. From July 1974 for a period of 41 weeks approximately half the gilts entering this unit and half of the older sows in it were given Se s/c.

The gilts received 2.5 mg Se at mating and the sows 2.5 mg a few days before mating (when their offspring were weaned); both age groups received a second injec- tion of 2.5 mg Se within the last week of gestation. The remaining gilts and sows not given Se served as controls. In units 1, 2 and 3 all gilts and sows received 2.5 mg Se s /c at the same time as those in unit 4. Detailed records were taken and are summarized in Table 2.

In this trial a significant response ( ~ 2 = 4.2, p < 0.05) to Se was again demonstrated in the con- ception rates of gilts. A marginal but non-significant response was demonstrated in the sows. There was no effect on piglet mortality.

The diet of the gilts and sows in all units was identical and consisted of a wheat base together with sorghum and high protein mineral and vitamin supplements. The Se content of this diet was 0.1 ppm.

The significant and economic response to Se, par- ticularly by gilts, in this investigation was not expected. All the stock were in excellent health and none of the known disease syndromes responsive to selenium had been observed at the piggery. The level of Se in the diet was low but we have no knowledge of its biological availability to the pig. (Unfortunately, it was not pos- sible to obtain any blood samples from affected gilts to check blood selenium values. ) There was some sugges-

TABLE 1 The Fertility of Gi l t s Giverr Scleriitcm (urrits I and 2 ) Compured with Undosed Gilts (units 3 and 4 )

~~ ~~~ ~~ ~

Total Total Unit 1 2 1 & 2 3 4 3 & 4

No. at mating 115 155 770 195 182 377 No. retained 114 152 266 193 171 364 No. farrowed to 94 1 I7 21 I 131 105 236

No. returned” 38 98 No. not in pig:- 17 30 No. culled 4 13 No. pig born 1649 1832 NO. pigs alive at 1576 1735

Mean litter size 7.84 7.76 Mean birthweight 3.01 2.94 Farrowing % t82.5 77.0 79.3 67.9 61.8 64.8 Return % 14.3 26.6 Not in pig % 6.4 8.6

first service

birth

Dead piglet % 4.4 5.3 ‘a gilt which returned to service up to 6 weeks after first service. :a gilt which was served, was not observed to return and did not produce a litter. ?No. of pilts farrowing to the first service x 100. No. gilts re ta ined in unit.

Arrstrulitrri Vcteririary Jorrrrial. Vol. 53, November, 1977 553

TABLE 2 The Fertility of Gilts and Sows Supplemented with Selenium Compared with Undosed

i with Supplemented Animals on Other Units ( I , 2 and

No. at mating No. retained No. farrowed to first service No. returned No. not in pig No. culled No. of pigs born alive Mean litter size Mean birthweight Farrowing % Return % Not in pig %

Unit 4

Gilts Se No Se

153 148 118 19 I 1 5

95 I 8.06 2.80 79.3 12.8 7.4

244 232 163 52 18 12

1301 7.98 2.90 70.3 22.4 7.8

sows Se No Se

329 323 28 1

33 9 6

2589 9.21 2.94 87.0 10.2 2.8

525 492 413

66 16 33

3812 9.23 3.09 83.9 13.4

3.3

'onfrols on the Same Unit )

Units 1, 2 & 3

Gilts sows All Se

1591 1.547 1221 230 96 44

9144 7.49 3.07 78.9 14.9 6.2

3049 2934 2413

386 133 115

22357 9.27 3.13 82.2 13.2 4.5

tion that the fertility problem was connected with the The results of these two trials suggests that large replacement of barley by wheat in the diet. piggeries elsewhere with a suboptimal fertility, particu-

The cause of the selenium responsive infertility in I a rb in gilts, might benefit from Se supplementation. M. J. EDWARDS, sheep in New Zealand was shown to result from W. J . HARTLEY, embryo mortality at about 3-4 weeks gestation followed

by a delayed return to oestrus (Hartley 1964). In the Department of Veterinary Clinical Studies, present trial the exact cause of the gilt infertility was University of Sydney, Camden, New South Wales, 2570 not investigated. However, the evidence suggests a direct effect at the time of conception, although very early Mayfair Farms, Menangle, New South Wales, 2568 embryonic mortality could not be excluded. 13 A p r i l 1977

Reference The difference in gilt fertility in unit 4 between the two trials suggests that some other depressing factor was Hartley, W. J . (1964)--Proc. N . Z . SOC. Anim. Prod. 23:

E. A. HANSEN,

present at the time of the first trial. 20.

OXALATE NEPHROPATHY IN A HORSE

Jubb and Kennedy (1970) state that horses are re- sistant to oxalate poisoning as a nephrosis but succumb to acute gastroenteritis after receiving unnaturally large amounts of the chemical. However, Andrews (1971) describes a case of oxalate poisoning resulting in pro- gressive nephrosclerosis in a horse. We would like to record a case of chronic interstitial nephritis in a 14-year-old gelding associated with oxalate crystal deposition in the proximal convoluted tubules of the kidney.

The horse had been sick for 3 weeks prior to veterin- ary aftention. Initial clinical examination revealed anorexia, mild impaction, a rectal temperature of 39.7"C, dehydration and ventral oedema. Haemato- logical examinaton showed a packed cell volume of 42% erythrocytes and a total white blood cell count of 18,500 per mm-R. Faecal examination revealed 1,000 strongyle epg. Thiabendazole and paraffin were ad- ministered orally and supportive treatment with intra- venous fluids was commenced. Initial treatment with penicillin - streptomycin had no effect but a change to chloramphenicol reduced the temperature. Treatment was continued for 14 days without any apparent improvement in the animal's condition and it was finally killed using pentabarbitone given intravenously.

Immediate post mortem examination showed oedema of the gastric mucosa and a large (7.5 cm x 5 c m ) gastric ulcer which had haemorrhaged and filled the lumen of the stomach with blood. The small intestine was blood filled and showed a haemorrhagic enteritis while the mucosa of the large intestine was reddened and contained minute blood spots; the colon contained a large amount of sand. The liver was swollen, turgid and of a slight bronze yellow colour. The kidneys were small, pale, rounded and granular. The urine was pale in colour and thin in consistency. Urinalysis gave nega- tive results for glucose, ketones, blood and bilirubin, a +++ reading for proteins and it was acid to litmus.

Histopathological examination of the kidneys showed gross distension of the lumina of the proximal convo- luted tubules (Figure 1). There were numerous oxalate- type crystals within the lumina and widespread degener- ation of the tubular epithelium. The crystals were cuboidal in shape, strongly birefringent in polarised light (Figure 2) and stained positively with both von Kossa's stain for calcium salts (Mallory 1961) and with Pizzolato's (1964) stain for calcium oxnlate. Furthermore the crystals were soluble in hydrochloric acid but not in acetic acid (Benjamin 1973). There was an accompanying severe chronic interstitial nephritis.

554 Arrstraliari Veterinary Joiirrial, Vol. 53. November, 1977