Peas as a Source of Protein in Milk Replacers for Holstein Calves
Much research is being done in using alternative sources of plant protein to replace costly milk protein in the diets of pre-ruminant calves (Madrigal-Ambriz et al. 1992 {589}; Lalles 1993 {580}; Molchanov et al. 1983 {687}). Soyabean protein is the most common alternative for veal calves, but pea protein also has potential for this use (Kolar and Wagner 1991 as cited by Lalles 1993 {580}) (Table 3). Peas contain approximately one-half the protein as soybean, but the protein quality is high (Lalles 1993 {580}). The first limiting amino acids for pre-ruminant calves are the sulfur amino acids followed by lysine, threonine and isoleucine (van Weerden and Huiman 1985 as cited by Lalles 1993 {580}). Therefore pea protein should be adequate as long as methionine is added (Lalles 1993 {580}). The limiting factor in incorporating pea flour into milk replacers is the high concentration of starch (Lalles 1993 {580}). This limitation is reduced with the use of pea concentrates and isolates. A pea concentrate, from alkaline extraction and precipitation of pea flour, has a lower starch concentration (2.99 vs. 39.96 g/100 g dry basis), total carbohydrates (20.91 vs. 53.87), crude fiber (0.77 vs. 11.92), and ether extract (2.58 vs. 3.55) and a higher level of crude protein (68.19 vs. 27.39), ash (7.55 vs. 3.27) and DM (92.73 vs. 91.80) than pea flour (Madrigal-Ambriz et al. 1992 {589}). Pea isolates are characterized by a further reduction in starch and oligosaccharides.
Results using pea proteins are variable and seem to reflect the age of the animal, processes used before incorporation, the level included in the milk replacer and the level and type of anti-nutritional factors (Table). Milk substitutes containing peas are less readily accepted by young calves compared to skim milk replacers (Mbugi et al. 1989 {628}; Drean et al. 1995 {565}). Replacing skim milk powder with legume proteins reduces calf growth in proportion to their incorporation rate (Troccon and Toullec 1989 as cited by Lalles 1993 {580}; Kvasha and Gritsai 1990 {616}). In 5- to10-week-old calves, when 34% of the protein was replaced with raw pea flour gains decreased from 0.66 kg/day in week 1 to 0.11 kg/day by week 4 compared to calves fed the all-milk diet 0.97 kg/day(Bush et al. 1992 {583}; Bush et al 1991 {600}). In another experiment with 50 day-old calves, replacing 16.5% milk protein with dehulled raw pea flour significantly reduced liveweight gain compared to the control (milk protein) (1145 g/day vs. 1366 g/day). However, when flaked pea flour replaced raw pea flour at 16.5% of the milk protein, there was no difference in gain compared to the all milk control (Drean et al. 1995 {565}). The low tolerance to the raw pea flour appeared to be due to anti-nutritional factors since flaked pea flour, in which most anti-nutritional factors had been destroyed, had no negative effect on the growth of calves. In 0- to 45-day-old calves, 30% of the milk protein was replaced with pea protein concentrate (80% CP). Gains did not differ from the skim milk control, but at 60% they were significantly reduced (Mbugi et al. 1989 {628}). When milk proteins were replaced with either raw or flaked pea protein, pancreas weight decreased significantly (16-18%), and amylase-specific activity increased significantly (43%) (Drean et al. 1995 {565}) indicating a change in digestive processes.
Pea protein concentrate and gelatinized pea flour have been reported to have a low digestibility in preruminant calves (Bell et al. 1974 as cited by Bhatty and Patel 1983 {683}; Prado et al. 1989 {625}; Kirilov et al. 1988 {645}). Pea isolate has a greater digestibility, but is not equal to a skim milk replacer (Bhatty and Christison 1980 as cited by Bhatty and Patel 1983 {683}). Lower protein digestibility in comparison to milk replacer has been contributed to higher levels of starch and oligosaccharides, the presence of resistant proteins or peptides (Bhatty and Patel 1983 {683}; Spencer et al. 1988 {641}) and anti-nutritional factors that are difficult to destroy completely with common technology (Lalles 1993 {580}). Extruded or heated peas have a higher fiber digestibility and feeding value than raw peas in starter diets (Kolobov 1985 {664}; Natsyuk 1985 {668}; Kirilov et al. 1988 {645}). Inclusion of pea proteins cause changes in digestion including increased digesta flow rates (Seegraber and Morrill 1986 as cited by Bush et al. 1992 {583}; Prado et al. 1989 {626}); increased volumes of digesta (Bush et al. 1992 {583}) and decreased nutrient digestibility (Bush et al. 1992 {583}).
Bell et al. (1974 as cited by Mbugi et al. 1989 {628}) reported that a milk replacer with pea protein used at 50% in the milk replacer for young calves was 25% digestible by calves < 2 weeks old and 65-70% digestible by 3 weeks of age. The apparent digestibility of DM, crude protein, and energy were lower (P < 0.05) for a milk replacer containing 60% protein from pea concentrate than the all-milk diet (Mbugi et al. 1989 {628}). The total volume and DM content of digesta were increased (P < 0.01) at week 1 and further by week 4 due to the substitution of pea protein (Experiment 1) (Bush et al. 1992 {583}). Ileal digestibility of DM, organic matter, nitrogen, fat, minerals and nitrogen-free extract decreased (P < 0.01) with the substitution of pea protein. The lower digestibility of the nitrogen free extract in the pea diet resulted from its high content of raw starch (18% of DM) and from cellulose and oligosaccharides (1 and 3% DM, respectively). A large amount of starch escaping through the small intestine may have increased bacterial growth in the hindgut. The proliferation of bacteria in the hindgut tended to reduce nitrogen digestibility (83 vs. 72%) and increase pea nitrogen-free extract (53 vs. 69%) (Bush et al. 1992 {583}). The decreasing apparent digestibility of the pea protein appeared to result from the increased endogenous and bacterial protein loss. An overall increase in ileal flow of dietary, endogenous and bacterial protein is observed with the supplementation of pea protein (Lalles 1993 {580}). This was consistent with decreased digestion of legumin (Bush et al. 1991 as cited by Lalles 1993 {580}) and a fourfold increase in the flow of active trypsin at the ileum (Lalles 1992 as cited by Lalles 1993 {580}). The pea diet was lower in ileal digestibility for individual and total amino acids as well as amino acid nitrogen (Bush et al. 1992 {580}).
Pea proteins are able to induce antibody formation when given to calves (Bush et al. 1992 {583}; Hessing et al. 1993 {575}; Prado et al. 1989 {626}; Nunes et al. 1988 {638}; Nunos et al. 1988 {639}). Preruminant calves at weaning are prone to developing a gut immune-mediated hypersensitivity reactions. Unlike piglets that become tolerant after a few weeks, calves remain hypersensitive for months (Lalles and Peltre 1996 {558}). The antibody response consists mainly of immunoglobulin (Ig) G isotypes, but IgE and IgA may be involved. At the first introduction of pea protein (21.6 legumin mg/g of DM) to calves the concentration of immunoreactive legumin found in the ileal digesta was much higher (1.04 and 1.27 vs. 0.03 mg/g of DM) in comparison to calves receiving the all milk diet (Bush et al. 1992 {583}). Antibodies were formed against both legumin and vicilin with a titer of 1 (start), 5.5 (7 d) and 9-9.5 at 28 d. After 28 d calves were placed on an all-milk diet and antibody titers dropped immediately. Following the second 4-week introduction to pea protein, antibody titers increased, but not until d 9 and by d 35 titers were 9-9.5, similar to the previous experiment. Between 0.5-3.0% of the legumin fed was still immunologically active in the ileal digesta and the feces (Bush et al. 1992 {583}; Prado et al. 1990 {609}). These results indicate that the effects of incorporating peas into calf milk replacer depend on the level of processing, the age of the calf, the inclusion level and the level of anti-nutritional factors.
Results using pea protein in calf milk
replacer report that nutrient digestibility, nitrogen balance
and blood urea concentrations in calves were lower with diets
containing pea meal compared to those containing SBM or rapeseed
meal until the age of 80 d. Performance and digestibility numbers
for calves older than 80 d fed SBM, pea or canola protein are
expected to be similar (Namiotkiewicz et al. 1987 {651}).
| Table 3. Average daily gains (g/d) and apparent digestibility (%) of nutrients of milk replacer diets including pea proteins fed to young Holstein calves | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Protein Source | Diet SMP:Pea | Age | ADG | Apparent digestibility % | Ref | ||||
| Day | g/d | DM | CP | Energy | Ether Extract | OM | |||
| Pea flour-dehulled, pregelatinized | 66:34 | 0.92 | a | ||||||
| Pea flour-dehulled, raw week 1 | 66:34 | 0.89 | b | ||||||
| Pea flour-dehulled, raw week 4 | 66:34 | 0.78 | b | ||||||
| Pea concentrate (80% CP) | 70:30 | 0-45 | 421 | 91.2 | 85.9 | 91.4 | 91.0 | c | |
| Pea concentrate (80% CP) | 40:60 | 0-45 | 358 | 87.1 | 78.7 | 86.5 | 84.5 | c | |
| Skim milk replacer | 100:0 | 0-45 | 478 | 92.1 | 87.6 | 92.0 | 91.6 | c | |
| pea flour-flaked | 83.5:16.5 | 50-140 | 1324 | d | |||||
| pea flour-raw, dehulled | 83.5:16.5 | 50-140 | 1145 | d | |||||
| Milk substitute | 100:0 | 50-140 | 1366 | d | |||||
| Pea flour-raw, dehulled | 66:34 | 35 | 660 | 81 | N-89 | N-Free-76 | 90 | 83 | e |
| Skim milk powder | 100:0 | 35-135 | 970 | 93 | N-93 | N-free-94 | 96 | 95 | e |
| Pea flour-raw, dehulled | 66:34 | 70 | 110 | 71 | N-78 | N-free-71 | 70 | 74 | e |
aDo Prado et al. 1989 as cited by Lalles 1993 {580}; bBush et al. 1991 as cited by Lalles 1993 {580};
cMbugi et al. 1989 {628}; dGwenola et al. 1995 {565}; eBush t al. 1992 {583}.