Article contents
Efficiency of utilization during pregnancy and lactation in the ewe of the protein reaching the abomasum and truly digested in the small intestine
Published online by Cambridge University Press: 02 September 2010
Abstract
In six experiments carried out on individually penned Finn Dorset ewes estimates were made of the quantities of non-ammonia nitrogen (NAN) reaching the abomasum and truly digested in the small intestine. For experiments 1 and 2 which each involved 33 ewes given a complete diet of milled hay and concentrates supplemented with varying amounts of a good-quality fish meal during late pregnancy, the overall regression estimate for the daily amount of truly digested NAN required for zero N retention (ewe plus conceptus) was 438 mg/kg M0·75 (441 and 434 for experiments 1 and 2 respectively). The coefficients for the efficiency of utilization of increments of truly digested NAN and maternal tissue N for net N accretion in the conceptus were 0·48 (s.e. 0·039) and 0·84 (s.e. 0·127) respectively.
In experiment 3, 24 lactating ewes had their diet supplemented with either soya-bean meal or fish meal. There was no effect of protein source on the amounts of NAN reaching the abomasum in ewes fitted with an abomasal cannula or on milk yield and these observations confirmed the unusually high degradability (measured by the polyester bag technique) of the fish-meal protein in the rumen. For experiments 4, 5 and 6 a total of 36 ewes were used to test the efficiency with which the NAN truly digested in the small intestine was used for the synthesis of milk protein. In the absence of data on the possible contribution of body tissue N to milk N the coefficient for the apparent efficiency of utilization of truly digested NAN when the ewes were given a basal diet containing approximately 10 g crude protein per MJ metabolizable energy was 0·63. For those ewes receiving the basal diet supplemented with either soya-bean meal, fish meal or blood meal the coefficients for the efficiency of utilization for the production of milk N of the increments in truly digested NAN supplied by the three protein sources were 0·61, 0·54 and 0·29 respectively. It is suggested that the low coefficient for blood meal may be due to its low content of methionine.
- Type
- Papers
- Information
- Copyright
- Copyright © British Society of Animal Science 1989
References
REFERENCES
- 5
- Cited by