THE PIG INDUSTRY

Manawatu Times, Volume 62, Issue 31, 6 February 1937, Page 12 (Supplement)

THE PIG INDUSTRY

Notes by M. J. Scott, BA, B.Sc. LITTER PRODUCTION Wheu a sow produces a good litter, the owner, unless he is an expert and knows exactly why the litter is so excellent, usually gets as much kick out of the event as if he had eellected on the last sweepstake. He takes a reasonable pride in the event, and tells his friends, but perhaps he also wonders just how it happened to be so good Even the experts are perhaps a littl* surprised sometimes at the excellent of' their results because they can recollect numerous incidents that were likely to do harm to the sow, while she was in pig. Although on the whole the exercise of care at the right tune and the intelligent use of the best‘information is likely to give good results, still, there is no royal roud to success in producing good litters. If there were these would be a commonplace, but instead of that, poor litters with their resultant los and disappointment make pigs unprofitable still on many farms.

A good litter should weigh between *>oo and 400 lb. at eight weeks old, the greater the number of piglets the better. Thus 10 piglets of 301 b. each is a better litter than 6 piglets of SOlb. each. A spring balance is a valuable adjunct in assessing litter value. The production of good litters begins with the shedding of the eggs from the ovaries of the sow, during the heat period. It is usually considered that 20 to 30 ova are shed over a period of 30 to 30 hours from the first onset of heat, by a sow that is in good condition for breeding. The actual onset of heat and the number of eggs produced during oestrum, are determined ,in the sow, as in every other animal, by the amount of improvement that is taking place in the animal at that time. This improvement if commonly sx>oken of as “ flushing. in the sow this flushing automatically takes place immediately after weaning, and is due to the re-absorption of milk from the udder back into the j sow's body, it is probably because of this automatic flushing that oetsrum occuis so regularly within three to six days of weaning, it is also probably true that where the first heat period is missed aud difficulty is subsequently experienced in getting a sow -in pig, ' this difficulty is because of the absence of flushing. Treatment of the bow at leaning hi any owners, at weaning, turn the sow out on a bare paddock and reduce her feed supply, and even let her back to the litter once a day, so as to dry her off. it the sow is in high condition : this may be all right, but if the sow is in low condition this treatment may result in delayed oestrum or the shedding of few eggs, and a small litter following. Where sows fail to come on heat after weaning, they should be shut up and fed heavily, for a week before the next heat period is due. On the other hand where maiden sows are in such high condition that they are incapable of rapid improvement at the onset of oestrum, small litters often result, and this can be prevented by keeping the sow always in good condition but somewhere below the peak of ter form. Time of Boar Service It was mentioned above that 20 to 30 ova may be shed over a period of 30 to 36 hours from the time the sow first comes on heat. These eggs are shed one at a time, and if service takes place wheu only a few eggs are shed, then only a few Vill be fertilised and a small litter will result. The sperm of the male remains active on the uterus for about 8 to 10 hours, so that if service takes place at 24 hours after heat begins all eggs shed up to 32 to 34 hours may be fertilised. If these points are appreciated the sow will be served ideally, that is with every prospect of a big litter, about 24 to 36 hours after she conies on heat. In practice the best thing is probably to give one service when the sow is well on heat, and a second one as late as the sow will stand service. Treatment During Gestation If the owner nus attended to these bus laid the foundation for a big litter, and provided the sow is treated for the uext four mu th.H, "tT? bhOftld 'not be disappointed. Experimental work at Cambridge University some years ago on in-pig sows shewed that a few days after service a sow's uterus showed the implantation! of 2U fertilised living embryo with a porrespuuding number of “corpora fit** 79 .in, tfie ovaries. A month alter sacvu;cl.there were found the implantations ul 20 fertilised embryo, and corresponding corpora lutea but only W*io 16 of the embryo were alive. Two months after service only 10 to 12 foetuses were found, and at four months ten to twelve pigs were farrowed. In xll about 50 sows were slaughtered in lollecting this information, and at the different killing stages it was found that on the average the same number of eggs were fertilised per sow, u%t that as the months went by the number surviving got less and less till only half the number fertilised were born alive. At birth while an average of Un live pigs were produced, some sows produced dead pigs, some weakly ones that died after birth and some, of course, produced litters of even-sized pigs. Causes of foetal Mortality Thu explanation of the observed

happenings appears to be that a sow sets out to produce a maximum number of offspring, but finds as time goes on that she cannot maintain her original intention, and by restricting the blood supply to any foetus, stops its develop ment, once tho blood supply is cut off tho foetus ceases to live and if time permits, it is absorbed back into the maternal system. If tho blood stream has been cut off late in the gestation period the little one may be born dead, absorption having been impossible iu a short time. If the blood supply has been restricted the pig may be undeveloped, weakly or undersized, and may survive to bo the runt of the litter.