11th International Conference on Pig Reproduction

The 11^th ICPR was held in the city of Ghent and saw some 150 scientists and representatives from the pig industry attending. The ICPR is historically known as a truly scientific conference, however, in this edition there were a large number of more practical contributions from the industry and associated organisations such as SEGES in Denmark. Invited speaker sessions were alternated with short oral presentations and ‘flash’ poster presentations. Key topics at the conferecne were embryo development, endocrine regulation of reproduction, male/sperm function, puberty and gilt management, perinatal management and piglet survival.

As usual, quite a number of presentations addressed the latest advances in the science of embryo development, maternal recognition of pregnancy, and embryo survival. Dr Geisert from the USA presented new identified factors produced by the conceptus that induce and subsequently control localised inflammation in the endometrium, to regulate vascularisation and implantation. Other speakers presented work on elongation of the conceptus during early pregnancy and metabolic pathways in the pig conceptus. Trouw Nutrition presented data on how sow weight loss during lactation negatively affects the size of the conceptus at day 8 of the pregnancy following weaning and mating. This relationship indicates the importance of feeding sows to requirements during lactation as much as possible and illustrates the impact of negative energy balance on ovarian physiology during and after lactation. 

Ovarian function

The current state of knowledge on ovarian function and follicle development in pigs was presented by speakers from the USA (Rob Knox) and The Netherlands (Katja Teerds - WUR). Given the effect of lactation on ovarian function and subsequent pregnancy, a number of studies were presented on ‘flush feeding’. In two studies, one in mixed parity sows and one in gilts, providing extra energy before mating and even in lactation had no effect on subsequent litter size. In another study, feeding 400 g of extra glucose on top of the standard diet (4.4 kg/d) from weaning to oestrus increased litter size (23.7 vs 22.8), but not birth weight (1218 g vs 1226 g).

Pubert/gilt management

The impact of today’s large litters in high prolific sows on the rearing and reproductive performance of their offspring was one of the central themes at the conference. An interesting paper by dr Flowers (USA) described the ‘litter of origin’ paradigm, which in short dictates that a large part (around 50 %) of the variation in lifetime reproductive performance of both gilts and boars is determined by the litter that they come from and the rearing conditions before weaning. Birth weight, weaning weight, and rearing (suckling) litter size all influence lifetime performance. The best gilts are born in large litters (good genetic potential), have a good birth weight, and are reared in relatively small litters (good weaning weight). Similarly, intra-uterine growth retardation has long-lasting effects on ovarian function and lifetime reproductive performance. Colostrum intake is critical to ensure proper early development of breeder gilts. Danish research indicates that delaying the first mating to mate at older age and larger body weight results in more piglets, however, with less gilts reaching second parity. Therefore, for Danish sows BW at mating is recommended not to be over 164 kg, and BF>13 mm.

Perinatal management

As mentioned, management of litters from high prolific sows was a recurring theme. The increase in litter size over the years has resulted in sows taking longer to farrow smaller piglets than in the past. Based on research by Alexander Grahofer (Switzerland), longer farrowings are associated with higher progesterone in colostrum. Nutrition of the high prolific sow around farrowing and in lactation was discussed by dr Feyera in a paper co-authored by the late dr Theil. He described the importance of energy intake around farrowing to reduce the duration of farrowing. This was also illustrated by a study where an energy supplement provided to the farrowing sow by means of a drench, improved the poor Apgar score normally observed in piglets born later in the litter (Carnevale, Brasil). In a large scale commercial Danish study, 2.8 kg/d and 3.7 kg/d of a lactation diet were compared with 3.7 kg/d of a fibre rich transition diet in the days before farrowing. The treatments resulted in daily intakes of 499, 649, and 659 g/d of fibre , and 361, 476, and 421 g/d of SID protein. Stillbirth was 12 %, 11 % and 10 %. There are also indications that oversupply of protein may compromise farrowing duration and increase stillbirth, but it is not clear how. Injection with dexamethosone just before farrowing did not seem to benefit stillbirth or survival, although glycemic status of the sow and farrowing duration were improved (Bortolozzo, Brasil).

Reduced birth weights of piglets in large litters is directly linked with survival. Data presented by Hornstra (Netherlands) illustrated this: piglets in weight categories of <0.7 kg, 0.7-0.8 kg, 0.8-0.9 kg, 0.9-1.0 kg, and 1.0-1.1 kg had survival rates of 6 %, 29 %, 42 %, 61 %, and 80 %, respectively. Scientists at the conference clearly recognised the importance of research to improve birth weight. Trouw Nutrition presented data showing the strong relationship between placenta size and birth weight. In a gestation study, chelated or glycinated trace minerals (Cu and Mn) did not affect birth weight. A few studies were presented on the potential of colostrum to increase survival of small piglets, and on factors that influence colostrum. Feed allowance prior to farrowing still seems to be one of the few factors that are recognised to improve colostrum yield. In a study with feed allowance in transition ranging from 1.8 kg/d to 5.0 kg/d, the optimum feed allowance in terms of colostrum yield appeared to be 4.2 kg/d. Other ways to influence colostrum yield and quality are under research. For example, algaeal beta-1,3-glucans during the last 5 weeks of gestation may improve colostrum yield and IgG.

Lactation

Nutritional management of lactating sows was discussed by dr Feyera from Denmark. A good performing lactating sow is one with high feed intake to cover the lactational needs for energy and protein, and one that can compensate insufficient feed intake by mobilising her own body reserves of fat and protein. Having said that, body weight loss is not necessarily a sign of good milking ability, on the contrary. Energy and protein intake in lactation limit milk production, and therefore it is important to ensure adequate intake, as otherwise sows need to mobilise to the extent where litter gain is compromised. Litter gain (or milk production) is increased at higher protein (lysine) intake, however, only to a certain point where a plateau is reached. Excess protein and lysine result in deamination and reduced nitrogen efficiency. The message here was to maximise milk from feed rather than body reserves.

A summary of all the research shared can be read  here.