Effect of Essential Amino Acids on Performance of Buffaloes

Fifteen lactating Nili-Ravi buffaloes having similar milk production (Group I- 9.88±1.59; Group II- 9.11±2.10; Group III- 9.52±1.07) were divided in to three groups (five buffaloes in each group) according to CRD for this study. Three iso-caloric and iso-nitrogenous diets with 3 levels of EAA (lysine, methionine and threonine) were formulated using NRC (2001) standards for energy, protein and EAA (Supplementary Table I).

The buffaloes fed individually at ad libitum intakes and were housed on concrete floor in separate pens (40 square feet covered area + double open space). The study lasted for 100 days (10 adaptation + 90 experimental), first ten days were adaptation period while every first week of each month of the remaining period served as collection periods. The buffaloes were weighed at start of the study and fortnightly thereafter.

Milk samples were taken for the analysis of milk fat, crude protein (CP), total solid contents (AOAC 1990). Feed offered, refusals and fecal samples were analyzed for dry matter (DM), CP (AOAC 1990), neutral detergent fiber (NDF) and acid detergent fiber (ADF) (Van Soest et al., 1991) while metabolizable energy (ME) was estimated according to Conrad et al. (1984).

Nutrients digestibilities and nitrogen balance were determined by the complete collection of urine and feces by the methods of Williams et al. (1984). Blood samples were collected from the jugular vein for hematological analysis by using standard kits method in hematology analyzer (AOAC 1990).

The data were analyzed according to Completely Randomized Design (SAS, 1988) Statistical model used for all parameters was; Yij = µ + τj + εij. Where, µ was overall mean, τj was the effect of treatment (3 treatments) and εij was difference within treatments (error term). In case of significance differences, the means were separated by DMR test (Steel et al., 1997).

The DM, CP, NDF, ADF and ME intake and nitrogen balance in buffaloes fed different EAA concentrations remained unaltered. However, there was a linear decrease in EAA and RUP intakes with reducing levels of these nutrients in the diets (Table I, II). The linear decrease in intake of EAA and RUP in buffaloes fed HEAA, MEAA and LEAA diets was because of gradual decreased dietary concentration of these nutrients in the experimental diets.

HEAA, MEAA and LEAA diets contained high, medium and low essential amino acids concentrations, respectively, means within row bearing different superscripts differ significantly (p<0.05), SE standard error of the means; ME, metabolizable energy; NDF, neutral detergent fiber; ADF, acid detergent fiber; DM, dry matter; CP, crude protein; DWG, daily weight gain.

Dry matter and NDF digestibility increased linearly with gradually decreased of dietary concentration of EAA and RUP in the diets but CP digestibility was similar statistically. The diets were iso-nitrogenous which did not influence CP digestibility, but improved DM and NDF digestibility in buffaloes fed decreased EAA and RUP concentrations might be attributed to gradual dietary increased RDP concentration which might have increased supply and availability of N in diverse forms (ammonia N, peptides and amino acids). This might have accelerated rumen microbial fermentation activities leading to improved feed consumption (DelCurto et al., 1990).

BUN, blood urea nitrogen. For other abbreviations, see Table I.

A positive correlation between increased rumen fermentation and dry matter digestibility has been reported previously by Nisa et al. (2004). Availability of N in diverse forms has also been documented to facilitate the synchronization of carbon and nitrogen units in rumen which has direct positive influence on rumen microbial proliferation and enzyme production which might have favored increased DM digestibility in buffaloes fed decreased EAA and RUP diets (Javaid et al., 2008; Nisa et al., 2008). Increased nutrient digestibility due to increased ruminal dynamics by availability of nitrogen in diverse form has also been documented by Haddad and Goussous (2005). Therefore, improvement in nutrient digestion in the current investigation might be due to increased ruminal dynamics by availability of nitrogen in diverse form to the host.

A linear (P<0.05) decrease in daily weight gain and milk yield was observed in buffaloes fed reducing EAA and RUP concentrations, however, milk fat content didn’t differ (Table III). This increased milk production and weight gain with increasing EAA concentrations might be attributed to better availability of dietary nitrogen in diverse forms which might have enhanced rumen microbial multiplication, per unit enzyme production and overall fermentation activities in the rumen leading to more volatile fatty acid production (Javaid et al., 2008). This might have enhanced nutrients supply for more milk synthesis. Furthermore, increasing dietary RDP concentration has been reported to increase rumen ammonia content (Nisa et al., 2008).

In the current study all the buffaloes were in positive N balance which led to spare more nutrients for milk production and daily gain. Ammonia, being alkaline in nature might have increased rumen pH which might have favored shifting the fermentation pattern in favour of acetate and butyrate production and ultimately increased milk production. The weight gain was also found to be affected by high input feeding systems in Nili-Ravi buffalo calves (Faraz et al., 2019). In addition to this, weight gain was also found affected by different feeding systems in dromedary camel calves (Faraz et al., 2017, 2018).

FCM, fat corrected milk. For other abbreviations, see Table I.

WBC, white blood cell count; RBC, red blood cell count; Hb, hemoglobin; MCV, mean corpuscular volume; Hct, hematocrit; Plt, platelets; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration. For other abbreviations, see Table I.

Observations of WBC, RBC, Hct, and MCHC remained unaltered across all diets, however, MCV and MCH concentrations decreased with gradual reduction of dietary RUP concentration (Table IV). Gradual reduction in MCV and MCH concentration with decreased dietary EAA and RUP concentration might have decreased the sustainable supply of EAA required for the normal biosynthetic activities aimed to synthesize these blood constituents. Gradual reduction in dietary RUP concentration might have limited the supply of these amino acids leading to their respective decreased contents in the blood, despite the fact that diets were iso-nitrogenous (Bergman and Heitmann, 1980).

Another plausible explanation of decreased MCV and MCH concentration might be that gradual increase in RDP fraction of dietary CP couldn’t ensure similar amino acid supply at post ruminal level to avoid any variation in blood amino acid profile which might have altered availability and sequence of amino acid supply for the synthesis of these blood constituents (Bergman and Heitmann, 1980). While Faraz et al. (2019) studied feedlot performance and serum profile of Nili-Ravi buffalo (Bubalus bubalis) calves under high input feeding systems and reported that hematological and biochemical profile was found to be altered in response to different dietary regimens.

A few reports available about hematology in Pakistan, however, in comparison to this, some studies also verified the effects of diet and feeding system on hematological parameters in dromedary camels (Faraz et al., 2017) and these measures could be used as indirect parameters for the evaluation of dietary management (Faraz et al., 2018) while these are the mirrors of general health status and physiological condition which may serve as a guide for these parameters (Faraz et al., 2020).

The results of present study testified the fact that varying levels of limiting amino acids have definite impact on the nutrient intake, utilization and milk yield. In this, milk production and daily weight gain decreased linearly with reducing dietary levels of EAA concentrations. While a positive nitrogen balance was also observed in buffaloes fed all the experimental diets. However, hematological analysis indicated decreased MCV and Hb concentrations in buffaloes fed gradual decreased dietary EAA concentrations. These results could be used for future studies in this field.

Authors are highly thankful to Senior Research Officer, Buffalo Research Institute (BRI), Pattoki for his valuable cooperation in provision of feed ingredients and animals for the current study. Authors are also thankful to field staff and laboratory personals for care and management of the experimental animals and carrying out the feed and fecal analyses. However, the BRI management had no involvement in the study design, conduction of the experiments, data analysis and interpretation, writing of the article or the decision to submit the article for publication.

There is supplementary material associated with this article. Access the material online at: https://dx.doi.org/10.17582/journal.pjz/20200419160408

The authors have declared no conflict of interest.