Performance of calves as related to the proportion of plant protein in milk replacer and to feeding frequency

Forty-two Black-and-White bull calves 8-11 days of age were divided into two equal groups and fed two types of milk replacer to 120 days of age. In the control group (C) the milk replacer (MR) contained 40%, in the experimental group (E), up to 87% crude protein. Whey protein supplement made up the level of protein in both groups to 100%. Liquid feed was given once, twice or three times daily, and concentrate was provided ad libitum. Prior to weaning, group E calves and those given liquid feed once daily consumed slightly more concentrate than bulls from group C or those offered liquid feed twice or three times daily. Throughout the whole experimental period, concentrate consumption was not affected by either the frequency or the type of milk replacer (P>0.05). Group C calves showed a faster growth rate and better feed conversion.


INTRODUCTION
Plant protein as a component of milk replacer is more poorly digested than milk protein and can negatively affect the absorptive capacity of intestinal mucosa (Montagne et al., 2000) and thus the growth of calves.The rearing efficiency of calves can also depend on the frequency of liquid feeding (Laerke et al., 2000;Strzetelski et al., 2001;Nussbaum et al., 2002).It is still not known how much benefit frequent feeding of liquid feeds with a high plant protein content has on the rearing performance of calves.The aim of this study was to determine the effects of feeding milk replacers with different proportions of plant protein once, twice or three times daily on the intake of solid feed and growth of calves.

MATERIAL AND METHODS
Forty-two Black-and-White bull calves from 8-11 to 120 days of age were divided into two groups taking into account initial liveweight and age.In the control group (C) 40% crude protein (CP) of the milk replacer (MR) was derived from soya protein concentrate, whereas in the experimental group (E) the milk replacer contained additional protein from linseed and dried brewer's yeast, reaching 87% CP.A whey protein supplement made up the protein level in both groups to 100%.Liquid feed (LF) was given in both groups up to day 56 of age in the same proportion but with different frequency: once, twice or three times daily.LF and solid feed were offered individually according to IZ-INRA (2001) standards.Refusals were recorded daily.Pelleted (ø 8 mm) concentrate (PC) was given ad libitum, meadow hay, in the amount of 0.1 to 0.3 kg/day.PC contained, %: wheat grain 23, barley grain 20, soyabean meal 20, oat grain 15, wheat bran 12.6, rapeseed meal 3, molasses 3, mineral-vitamin supplement 3, pellet binder 0.3 (Lignobond), mycotoxin binder 0.1 (Mycobond).The chemical composition of the feed was determined using AOAC procedures (1990).The results were analysed statistically by two-way variance analysis using the GLM procedure of the SAS packet (1989).Differences among treatments were determined using the LSM method.

RESULTS
One kg dry matter of both milk replacers contained on average 237.5±5g crude protein (CP), 214.5±0.6 g total digestible protein (TDP) and 1.575±0.005UFL.One kg of each liquid feed contained 0.194 UFL and 26.5 g TDP.Prior to weaning, calves of group E consumed, more concentrate and derived mainly from liquid feed DM, CP and UFL (Table 1).Calves fed milk replacers once daily, compared to those frequently given MR consumed slightly more (P>0.05)concentrate and nutrients, but the intake DM and CP from liquid feed was significantly higher (P=0.03 and P=0.02).Calves receiving milk replacer C had higher (P<0.05)daily weight gains than in group B (Table 2) and showed better (P<0.06)feed conversion (Table 3).Calves receiving liquid feed twice daily had tendency to faster rate of growth than those fed once or three times daily and showed better feed conversion (P<0.06).

DISCUSSION
The lower weight gains of calves in group E than in group C suggest that 87% of plant protein in CP of MR and its somewhat different composition negatively affect protein digestibility (Toullec et al., 1994).Once daily feeding with MR probably provoked the interest of calves in solid feed and they consumed more concentrate.However, the digestive tract was not completely ready to digest solid feeds, conversion was low and consequently calves showed poorer growth rate and feed conversion (Laerke, 2000).3.37 a 0.06 3.28 0.04 P-level of significance; P>0.05 -differences were not statistically significant; interaction was not significant A significant interaction between kind of milk replacer and frequency of feeding MR obtained for daily weight gains suggests that 40% of plant protein in milk replacer and administration of liquid feed twice daily probably have the most beneficial effect on the development of digestive function in calves (Laerke et al., 2000).

CONCLUSIONS
A lower content of plant protein in milk replacer ensures better utilization of nutrients by calves.Twice daily feeding of calves with milk replacers containing plant protein seems to be a reasonable feeding system for calves.

Table 1 .
Daily intake of liquid feed, concentrate and nutrients before weaning (56 days of age)

Table 2 .
Body weight and weight gains of calves