Pre-breeding blood urea nitrogen concentration and reproductive performance of Bonsmara heifers within different management systems

Abstract

This study investigated the association between pre-breeding blood urea nitrogen (BUN) concentration and reproductive performance of beef heifers within different management systems in South Africa. Bonsmara heifers (n = 369) from five herds with different estimated levels of nitrogen intake during the month prior to the commencement of the breeding season were sampled in November and December 2010 to determine BUN concentrations. Body mass, age, body condition score (BCS) and reproductive tract score (RTS) were recorded at study enrolment. Trans-rectal ultrasound and/or-palpation was performed four to eight weeks after a three-month breeding season to estimate the stage of pregnancy. Days to pregnancy (DTP) was defined as the number of days from the start of the breeding season until the estimated conception date. Logistic regression and Cox proportional hazards survival analysis were performed to estimate the association of pre-breeding BUN concentration with subsequent pregnancy and DTP respectively. After stratifying for herd and adjusting for age, 2 heifers with relatively higher pre-breeding BUN concentration took longer to become pregnant when compared to those with relatively lower BUN concentration (P = 0.011). In the herd with the highest estimated nitrogen intake (n = 143), heifers with relatively higher BUN were less likely to become pregnant (P = 0.013) and if they did, it was only later during the breeding season (P = 0.017), after adjusting for body mass. These associations were not present in the herd (n = 106) with the lowest estimated nitrogen intake (P > 0.500). It is concluded that Bonsmara heifers with relatively higher pre-breeding BUN concentration, might be at a disadvantage because of this negative impact on reproductive performance, particularly when the production system includes high levels of nitrogen intake.

The role of condensed tannins in ruminant animal production: advances, limitations and future directions

“…Common dietary N sources for ruminant diets, such as Medicago sativa and soybean meal, are highly degradable in the rumen, resulting in high ruminal ammonia (NH 3 ) concentrations and low N utilization efficiency -typically around 25% (Calsamiglia et al, 2010). This inefficiency is confounded by high RDP levels that downregulate N recirculation efficiency (Agle et al, 2010) and increase blood urea N (BUN) concentrations, which are associated with reproductive and fertility problems (Elrod and Butler, 1993;Westwood et al, 2000;Roche, 2006;Tshuma et al, 2014).…”

“…Rumen available N in excess of microbial growth requirements is absorbed as NH 3 , metabolized to urea in the liver, and either recycled or excreted in urine. High protein degradation rates increase urinary N excretion, which can negatively impact the environment (Powell et al, 2010), decrease N utilization efficiency, and impart a metabolic burden associated with increased urea synthesis and excretion that hinders animal performance (Van Duinkerken et al, 2005;Kohn et al, 2005) and fertility (Westwood et al, 2000;Tshuma et al, 2014).…”

Effects of oil and grape seed tannin extract on intakes, digestibility, milk yield and composition of Saanen goats

“…High rates of ruminal protein degradation increase N excretion via urine, which causes negative impact on the environment (Powell et al, 2011). Moreover, it decreases N utilization efficiency and animal performance (Kohn et al, 2005;Van Duinkerken et al, 2005) and fertility (Westwood et al, 2000;Tshuma et al, 2014). Krishnamoorthy and Moran (2012) reported that oil has 2.25 folds higher caloric value compared with carbohydrate (9 calories/g and 4 calories/g, respectively), thus oil-supplemented diet had higher energy density resulting in higher energy intake at similar feed intake level.…”

Serum albumin concentration of donor cows as an indicator of developmental competence of oocytes

“…Albumin significantly controls the ionized concentrations of important metals, it serves as a major circulatory protein responsible for the transport of Ca 2+ and Mg 2+ , is the principle carrier of hydrophobic and normally insoluble fatty acids and it inactivates toxic lipophilic metabolites such as bilirubin [4,47]. It further acts as transport agent for a wide range of smaller molecules such as fatty acids, metabolites, hormones, drugs, nutrients, minerals, gonadotrophins, steroids, growth factors and ions which are essential building blocks for oocyte maturation and growth [48,49].…”