Effect of blood urea nitrogen,mineral status and uterine PH on fertility in dairy cows

Abstract

An investigation was carried out with the objective of studying the effect of BUN and uterine pH on fertility in dairy cows under farm and field conditions and also for correlating the mineral status with fertility using 40 crossbred dairy cows selected at random during oestrus, 20 each from those belonging to University Livestock Farm, Mannuthy (Group I) and those brought for insemination at Artificial Insemination Centres at Mannuthy and Kokkalai (Group II). All the cows in Group I were found to be maintained in a relatively high nutritious diet computed as per the scientific feeding standards compared to Group II animals.

Detailed clinico-gynaecological examination was carried out and blood samples and uterine mucus were collected from all the selected cows during oestrus for estimation of biochemical parameters and uterine pH respectively. They were inseminated during the most appropriate period of oestrus and were subjected to pregnancy diagnosis at 60 days post insemination. Conception rates in both the groups were compared in relation to each parameter.

The mean duration of oestrus was slightly higher in Group II (30.00 ± 2.11 hours) compared to Group I (26.10 ± 1.74 hours). Intensity of oestrus was high, medium and low in 40, 45 and 15 per cent of animals respectively in Group I and 50, 40 and 10 per cent in Group II. Physical changes of reproductive tract viz. degree of vulval oedema and hyperemia of vestibular mucous membrane were more pronounced in animals of Group II compared to Group I, where as degree of tonicity was high in Group I compared to Group II. Characteristics of cervical mucus were also found to be affecting fertility. Better conception rate was obtained in animals with clear and stringy cervical mucus exhibiting typical type of fern pattern. Spinnbarkeit value did not vary much between conceived and non-conceived animals. Uterine pH did not show a marked variation between groups, even though a slightly higher value was recorded in Group I. But, an inverse relationship could be obtained between BUN level in serum and uterine pH during oestrus. Correlation between uterine pH and BUN level was highly significant (P<0.01) with a correlation co-efficient of r = -0.896 and r = - 0.753 in groups I and II respectively. The mean blood urea nitrogen level in animals of Group I was significantly higher (P<0.05) than that in Group II. The BUN level also varied significantly (P<0.05) between conceived and non-conceived animals of both groups. A marginal increase in plasma glucose level could be noticed in conceived animals compared to non-conceived animals of Group I. The mean serum total protein was significantly higher (P<0.01) in Group I compared to Group II. The serum level of minerals viz. calcium, phosphorus, manganese, zinc and copper were also correlated with fertility. The mean level of serum calcium and manganese varied significantly between groups I and II, but there was no significant difference in serum phosphorus, zinc and copper between two groups. Also, a slightly higher mean value was observed for serum calcium, phosphorus, manganese and zinc in conceived animals compared to non-conceived. But serum copper level did not vary between conceived and non-conceived animals.

In light of these findings, it can be concluded that the elevation in systemic concentration of urea is likely to impair fertility in dairy cows as a consequence of alterations in uterine environment. The benefits of feeding excess dietary protein and urea to maintain peak milk production should be compared with potential negative effects on fertility. Hence, a good nutritional management is essential for improved fertility in dairy cows.