Influence of dietary protein of diets given in late gestation and during lactation on protein content and oestrogen concentrations in the colostrum and milk of gilts

Abstract

AbstractForty first cross hybrid gilts were used to study the effect of dietary protein during lactation on free amino acid, protein and total oestrogen concentrations in colostrum and milk. The diets were formulated to contain similar levels of digestible energy (DE) but with either 236 or 186 g protein per kg and 13·3 and 8·1 g lysine per kg air-dried diet respectively. Both diets were offered at 2·5 kg/day for 1 week prior to farrowing and ad libitum throughout a 24-day lactation (no. = 20 gilts per treatment). Colostrum and milk were collected manually at 3h (colostrum), 3, 7, 14 and 22 days (milk) post partum. Free amino acid concentrations in colostrum and milk were determined by high-performance liquid chromatography following derivatization of the amino acids by 9-fluorenylmethyl chloroformate. The lysine and glutamic acid concentrations in colostrum were the most abundant free amino acids followed by tryptophan and taurine in order of decreasing abundance. Milk free taurine concentrations increased to the greatest extent among all free amino acids over the 21 days of lactation. Gilts' mature milk was rich in free taurine, glutamic acid, glycine and lysine. During the first 3 h post partum, the protein content of colostrum was unaffected by dietary protein. However, milk protein content over 7 to 21 days of lactation was significantly higher in gilts offered the higher protein diet (P < 0·001). Total solids in colostrum and milk was not significantly affected by dietary protein. At 3h and 3 days post partum the concentrations of total oestrogen in colostrum and milk, determined by radioimmunoassay, were significantly higher in gilts offered the high protein diet (P < 0·05). These finding indicate that a high protein diet in late gestation and during lactation can influence protein content, amino acid and oestrogen concentrations of milk in gilts.