DISCIZIA, sezione B. Ferrara, Università degli Studi di Napoli “Federico II”

 ABSTRACT: The influence of  protein degradability of diet on urea, ammonia, and K in the blood and vaginal mucus of lactating buffaloes was evaluated in two groups of buffaloes (T and C). Subjects  fed diet with lower protein degradability (T) showed  higher ammonia values in blood (P<0.01) but not in vaginal mucus. No differences were observed in the reproductive performance between the diets: in the 90 days of the trial, the conception rate was 37.9% and 41.4% respectively for T and C groups. The greater efficiency recorded in the buffalo compared with the dairy cow in transforming ammonia into urea suggests that diet protein concentration has not the same detrimental effects reported for the dairy cow.

Key words: buffalo cows, urea, ammonia, potassium, blood, vaginal  mucus.

 INTRODUCTION:  High levels of protein and especially the degradable fraction increase blood levels of urea and ammonia in bovines as well as buffaloes (Campanile et al., 1998). In bovines, such metabolites pass into the genital apparatus and have detrimental effects on reproductive performance, increasing the days open (Jordan et al., 1983; Rumello et al., 1999). Thus we aimed to verify the effect of two diets characterised by different protein degradability upon levels of urea, ammonia and potassium in the blood and vaginal mucus of lactating buffaloes.

 MaterialS AND metHodS: Fifty-eight lactating buffaloes were used at an average of 48 days open. The buffaloes were equally subdivided into two groups (T and C) with the same production and calving distance. The diet in both groups consisted of total mixed ration based on corn silage, wheat straw, soybean meal and concentrate fed ad libitum. The dietary proteins administered to the T buffaloes were made less degradable by addition of 350 g of a supplement containing microelements and Aspergillus oryzae (Sarubbi et al., 1997). The protein degradability was verified on 3 fistulated buffaloes and amounted to 79.3% for the diet of C group and 45.9% for that of T group. For each animal, within the whole (90-day) trial daily milk yield was registered, and every 15 days milk samples were taken from morning and evening milkings to determine fat and protein content (Milkoscan 133 B, Foss Electric, Dk, calibrated with appropriate buffalo standard). Production was expressed as energy corrected milk (ECM) using the formula calculated by Di Palo R. (1992). Feed intake and orts for each group were measured daily. Orts were sampled weekly on a random day. Analyses of individual feedstuff and orts were carried out per ASPA (1980) methods and energy values calculated according to INRA (1988) equations. Dry matter intake (kg) and average chemical composition of the diet throughout the period (%) are reported in the table below.

 From nine buffaloes not in oestrus of each group with about  30 days open at the beginning of the trial, two samples of blood and vaginal mucus (aspirated with an insemination pipette and syringe) were collected at distance of 20 days, to measure: ammonia (NH3), urea and potassium (K). For the blood sampling method and for the calculation of blood urea and potassium see Campanile et al. (1998). Ammonia was measured on whole blood immediately after sampling with a rapid method (Ammonia Tester II - Menarini). The vaginal mucus was diluted 1:1 with sterile physiologic solution and frozen up to analysis performed according to Jordan et al. (1983). Every collection day, BCS was evaluated by using the 1-9 scale (Wagner et al., 1988) suitably modified for buffalo. At the end of the trial the buffaloes underwent rectal palpation for possible pregnancies. Statistical analyses were performed using the GLM procedure for repeated measures between dietary groups, T and C, and between pregnant and non-pregnant buffaloes at the end of the study (P vs NP). We excluded from the analysis three buffaloes as they were already pregnant at the beginning of the trial and, for each variable, the buffaloes that scored anomalous values.

RESULTS Diet protein degradability did not result in differences in milk yield and quality of  T and C groups (ECM = 19.44 kg vs 19.38 kg respectively for T and C). Moreover, no differences emerged between the two groups when we compared blood and mucus data from the 18 subjects (ECM = 22.57 kg vs 23.03 kg respectively for T and C). The T group had higher blood values (P<0.01) in ammonia (Tab. 1) while there was no difference in urea and potassium values. Of all the subjects, irrespective of dietary characteristics, the P group had the lowest K values (P<0.05) in the blood. No significant differences emerged regarding the values of urea, ammonia and K measured in the vaginal mucus (Tab.1) between T and C groups and between non-pregnant (NP  group) or pregnant subjects (P group) by the end of the trial. No differences were observed in the reproductive performance between the treatments: in the 90 days of the trial, the conception rate was 37.9% and 41.4% respectively in buffaloes of  T and C groups. Examination of the data shows that although the subjects were fed 20% more protein than required for their milk yield, according to Campanile et al. (1998), the ammonia values recorded in their blood are always about 3-4 times lower while the urea values are higher than those reported elsewhere for dairy cows which received diets with a similar protein concentration. This suggests that the buffalo has greater hepatic efficiency in transforming ammonia into urea. The latter metabolite is less toxic and may be re-used by ruminal microflora for their own biosynthesis. The higher ammonia values in T group may result from the high level of undegradable protein which, not being completely digested in the jejune (NRC, 1985), may pass into the large intestine, where should be degraded by the microbial flora and transformed into ammonia which circulates once again. The low level of fermentable carbohydrates further promote the phenomenon (NRC, 1985). The urea values measured in the vaginal mucus of the buffalo were overlapping (Jordan et al., 1983) or higher (Rumello et al., 1999) than those reported in the dairy cow. By contrast, ammonia levels in vaginal mucus were considerably lower than those reported by Rumello et al. (1999) for dairy cows. The lack of differences between the groups in protein degradability contrasts with the findings of other authors (Jordan et al., 1983) who observed relations between potassium and dietary protein level in dairy cow. The greater efficiency recorded in the buffalo compared with the dairy cow in transforming ammonia into urea suggests that diet protein concentration, within the limits we studied, has not the same detrimental effects reported for the dairy cow.

 Table 1 - Estimated means (x ± s.e.) of the constants examined of T and C groups and in pregnant or non-pregnant subjects at the end of the trial (G and V).

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