The ability of pigs to consume sufficient nutrients for optimal performance is an important consideration in commercial pork production. Nutrient intake levels are directly related to voluntary fee...

Voluntary feed intake in growing-finishing pigs: A review of the main determining factors and potential approaches for accurate predictions

Feeding patterns in pigs: the effects of amino acid deficiency.

1. 14C-labelled lysine, glutamic acid and methionine were each administered as single infusions through catheters in the jugular veins of pigs between 28 and 42 d old, receiving either a low-protein (LP) (140 g protein/kg), or a high-protein (HP) (200 g protein/kg) diet. The pigs received 40 g diet/kg body-weight per d. 2. L-[U-14C]lysine and L-[U-14C]glutamic acid were both rapidly removed from the plasma; 3 min after completion of the infusion less than 10% of the activity from the [14C]-lysine, and between 10 and 20% of the activity from the [14C]glutamic acid remained in the plasma. 3. In pigs killed 15 min after infusion of either [14C]lysine or [14C]glutamic acid 26% of the activity from the dose of lysine was in the liver of those receiving the LP diet, whereas the corresponding value was only 16% for those which had received the HP diet. The uptake of activity from [14C]glutamic acid by the liver was unaffected by the level of protein in the diet. More activity from [14C]lysine than from [14C]glutamic acid was recovered in the spleen, heart and brain. 4. The recovery of the activity from [14C]lysine as 14CO2 in the 6 h after the infusion of the dose was lower for the pigs on the LP diet (2-7%) than for those on the HP diet (4-8%). The corresponding values for [14C]glutamic acid infusion were 34 and 52% respectively. 5. Supplementing the LP diet with five successive increments of 1-5 g DL-methionine/kg resulted in an increase from 8 to 17% dose in the recovery of activity as 14CO2 from a dose of L-[I-14C]methionine, whereas with the same supplementation of the HP diet the recovery increased from 8 to 24% dose.

Amino acid metabolism in the piglet: influence of level of protein and of methionine in the diet on tissue uptake and in vivo oxidation.

The importance of intake in feed evaluation.

Responses of gross energy intake and body weight of mice from weaning to maturity to dietary composition of energy-yielding nutrients were studied. Twenty-four groups of ddY male mice were fed for 70 days purified diets with a range of 0·08 to 0·75 protein, 0 to 0·92 fat and 0 to 0·92 carbohydrate concentration, calculated on a gross energy basis. Food intake and body weight data in each group were analysed by non-linear regression to obtain values of the parameters in the feeding and growth equation of Parks (1982). Prediction equations for these parameters were obtained with mixture model forms as a function of dietary protein, fat and carbohydrate. These equations for the parameters were then used to construct the response surfaces of body weight and growth rate at a given time on a triangular graph. The response surfaces of body weight at any time were convex, peak positions of which shifted from 043 protein and 0·29 fat at 10 days to 0·36 protein and 0·52 fat at 70 days. The configuration of response surfaces of growth rate (dW/dt) to the three components depends on feeding periods and at the longer periods of feeding the convex configuration of the surfaces became planar. The response surfaces of food efficiency (dW/dF) at any age were almost parallel to those of dW/dt, whereas a parallelism was observed between response surfaces of dW/dt and dF/dt only in young animals. These results suggested that the responses of body weight in young animals to dietary composition of energy-yielding nutrients depended on those of daily energy intake as well as food efficiency, but that those in older animals were affected by food efficiency only.

H.S. Bayley

Papers

Food intake regulation in pigs. I. The relationship between dietary protein concentration, food intake and plasma amino acids.