How can sows be helped? Prof Silva discussed three different strategies that can be used to help sows cope with heat stress challenges. Genetics are possible, he said. Producers can choose animals for more ro- bustness or can use thermo-tolerant genetics. Changing the environment is by far the most efficient, he says, but this of- ten comes at a high cost. Nutritional strategies are a third option, with Prof Silva dis- cerning between the options “dietary density” and “feed addi- tives” – in short, a choice between trying to stimulate feed in- take or trying to improve digestibility. Before delving deeper into this subject, he touched on water intake. In summer, he said, the sows drink 57% more than in winter. And water can also play a role in hydrating piglets. Normally they will ask for milk from the sow about 25 times per day. Under heat stress conditions, Prof Silva said, that doubles as the sow reduces her milk production, leading to irritated piglets, aggressive sows and a risk of crushing.
Changing dietary density To change dietary density, the first step is to reduce crude protein levels in sow diets, Prof Silva said. Two studies, one of them by Prof Silva himself, showed that reducing crude pro- tein levels increased feed intake 12–15%, as less crude pro- tein lowers the TEF. Increasing dietary energy levels during lactation, however, did not make a difference. It makes sense, Prof Silva said; after all, under heat stress conditions the ani- mals have fewer nutritional requirements.
Feed additives He then moved on to discuss health and digestibility through feed additives. Betaine has the capacity to protect sows against osmotic and high temperature stresses. In studies by the UFMG, there were positive results for both the average in- dividual and total litter weight of piglets at weaning. Similar- ly, both protected and unprotected butyrate showed positive results in terms of piglet performance, Prof Silva said. He went on to discuss the effect of antioxidant minerals and vita- mins. If you throw heat stress on top of a systemic stress, it worsens the situation, he said. In addition, trace minerals like zinc could help to close gut leakage. Lastly, he looked into the use of live yeast (Saccharomyces cerevisiae var. boulardii), which can improve fermentation in the hindgut, reducing constipation levels. Adding the yeast to sow diets in late ges- tation helps to increase the number of piglets born alive, Prof Silva said. It also stimulated sow feed intake in lactation and changed the profile of the milk, having an indirect effect on piglet performance. He closed off his analysis with some comments on flavour and how that can influence sow feed intake – up to 23% higher. Prof Silva therefore concluded: “By playing around with the feed composition and feed additives, we could enhance feed intake.”
This article is an approved summary of a webinar organised by Lallemand Animal Nutrition in its “Meet the Expert” series. It was broadcast on Tuesday 26 May 2020.
▶PIG PROGRESS | Volume 36, No. 5, 2020 11
A sow nursing her piglets in southern Viet- nam, where dai- ly temperatures can easily be 35˚C.
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