The capacity of the mature cow to lose and recover nitrogen and the significance of protein reserves

Abstract

I . Six experiments were undertaken with mature, dry, non-pregnant cows to determine the capacity to lose and recover nitrogen and to study the significance of the labile and total protein reserves.2. It was concluded that, without altering its ability to reach N equilibrium, the mature cow is able to store and lose large amounts of body proteins (certainly more than 15 kg), when its N and energy intakes are greatly varied. The repletion or depletion of protein reserves can occur over a long period of time (sometimes more than 5 months). Total protein reserves include a very labile part. This part is more rapidly lost during fasting than during feeding on low-protein diets; it can be used to meet temporarily the energy requirements of the animal.3. N balance and body-weight gains were generally very well correlated.More than a century ago, Voit (1866) concluded that the body of the well-nourished animal contains a store of labile proteins. The magnitude and significance of this store are still not clearly established. According to many authors (see Munro, 1964), the amount of labile protein deposited in the body does not exceed 5% of the total body protein and this labile protein disappears within a few days when the subject is fasted, or fed on a protein-free diet. But Allison (1964)) Allison, Wannemacher, Banks & Wunner (1964) and Allison & Wannemacher (1965) concluded that there was a larger protein reserve which can contribute to the maintenance of essential tissue structure. The protein reserve includes a very labile part.Most of the previous experiments were undertaken with simple-stomached animals. The present paper describes the results of six experiments intended to determine the capacity of the mature, dry, non-pregnant cow to lose and regain nitrogen and to study the significance of labile and total protein reserves. E X P E R I M E N T A LFriesian cows were used and were kept in metabolism stalls allowing the separation of urine from faeces. One of the stalls was so arranged that the cow's weight was automatically recorded every hour.Expt I. After being undernourished for z months, a 7-year-old cow received 4 kg pea-straw hay and 4 kg ground barley each day for a period of 5 months. According to Kellner & Becker (1962), this ration provided 130% of the energy maintenance requirements of the cow. During another 5-month period the ration was reduced by half ( z kg pea-straw hay and 2 kg barley). Urine and faeces were collected during Expt 2. Two groups of four and three cows, 6-10 years old and of almost the same body-weight, were so nouiished during 3 months that the cows in one group became nearly I 30 kg heavier than those in the other. Later, all the cows were given the same ration (3 kg barley straw, 2 kg ground barley, 2 kg concentrated foods each day) during a 2-month period. Urine and faeces were collected three times during 6 d periods.Expt 3. Three cows, 7-9 years old, received a winter ration of 3 kg hay and 3 kg ground barley for a month. Afterwards, grass, freshly cut each day, was given a...

Hormones and metabolites in lactating dairy cows fed insufficient amounts of proteina

“…Protein reserves are much more limited than fat reserves (PAQUAY et al 1972;BOOTS et al 1979;JOURNET and REMOND 1981;BELEYA et al 1986). Skeletal muscle constitutes the most important protein reserve (REID et al 1980;MOTYL et al 1984).…”

Reducing dietary protein in dairy cow diets: implications for nitrogen utilization, milk production, welfare and fertility

“…Efficacy of low protein diets for dairy cows which can be equivalent to an extra daily dietary protein supply over the first 100 days of lactation of~250 g, or 5% to 10% of protein intake (Paquay et al, 1972;Botts et al, 1979). The mobilised amino acids, particularly Met, may be used to enhance the rate of lipid transport from the liver and reduce the risk of FLS in early lactation, as described previously.…”

Effects of increasing days of exposure to prepartum transition diets on reproduction and health in dairy cows

“…If the diets were consumed as formulated, cattle were provided with an average positive MP balance of 286 g/day, which provides sufficient protein to meet fetal needs and gain the equivalent of more than 1 kg of muscle mass per day. Estimates of body protein reserves mobilised at calving are 25% to 27% of total body protein, which equates to approximately 10 to 17 kg of protein in a mature Holstein cow 24–26 . An increase in labile protein could provide for increased flux of glucogenic precursors after calving and a greater capacity to oxidise non‐esterified fatty acids without production of ketone bodies.…”

“…Estimates of body protein reserves mobilised at calving are 25% to 27% of total body protein, which equates to approximately 10 to 17 kg of protein in a mature Holstein cow. [24][25][26] An increase in labile protein could provide for increased flux of glucogenic precursors after calving and a greater capacity to oxidise nonesterified fatty acids without production of ketone bodies. Increased MP availability may upregulate the somatotropic axis and favour IGF-1 (insulin-like growth factor-1) production, a hormone associated with improved reproductive performance.…”