This review (parts 1 and 2) discusses the latest results on lactate metabo-lism in horses and the practical questions in the measurement of lactic acid as an indicator of equine performance. The same subjects are also discussed in a recent review (Pösö 2002).
Lactic acid, the end product of anaerobic metabolism, has been regar-ded as metabolic "waste product", which causes muscle fatigue. Recent research has, however, changed this view, and lactic acid is now seen as an intermediate metabolite which can be utilised as an energy sour-ce in several tissues. For example, heart, during exercise, may produce up to half of its energy from oxidation of lactic acid, and also for brain tissue lactic acid is a substantial energy source. Lactate transporters on cell membranes in muscles and other tissues play an important role in the metabolism of lactic acid. These membrane proteins facilitate the rapid transport of lactate across cell membranes.
Piglet mortality and poor growth greatly effects the economic result and animal welfare of piglet producing units. Both the sow and the piglets may influence milk production, and thus the growth and mortality of piglets through their behaviour. For example, the sow may allow access to the udder by lying laterally or she may deny it by lying sternally. Piglets can enhance milk production by massaging the udder.
We studied the relationship between the overall activity of sow and piglets and piglet growth and mortality. We were mainly interested in if the lying position of sows (lateral or sternal recumbency), amount of nursing observations or the time piglets spent at the udder are associated with piglet growth.
Twenty-one sows with litters were videotaped on days 3, 6, 13, 20 and 30 post partum. From the videotapes we recorded, by five-minute interval sampling, the behaviour of the sow and the number of piglets at the udder at each moment.
On day 20, nursing observations (at least 50 % of the litter massaging the udder) and the piglet growth cor-related positively, whereas the correlation was negative during the whole lactation period. On days 1–4 the time the piglets spent at the udder and daily growth correlated positively, and on days 15–22 there was a positive tendency for a similar correlation (0,05<p<0,1). The more active sows tended to have less piglet mortality.
According to our study, litters with poor growth spent more time massaging the udder, propably to enhance the milk production or to initiate the next nursing sooner. Passive sows allowed longer udder massage, which may not necessarily have enhanced milk production.