The relationship between blood and fertility parameters in post partum dairy cows

Factors influencing fertility of Holstein dairy cows: a multivariate description

Eighty-two multiparous cows of high and low genetic merit were fed one of two isonitrogenous (19.3% crude protein), isoenergetic (11.3 MJ of metabolizable energy) diets that differed in ratio of rumen-undegradable protein to rumen-degradable protein. Factors that influenced reproductive performance were investigated using logistic regression and survival analysis. Significant associations were identified between reproductive performance and indicators associated with nutrient balance. Cows with higher dry matter intake were more likely to show signs of estrus at first ovulation and to become pregnant by d 150 of lactation. Increased ratio of plasma glucose to 3-hydroxybutyrate was associated with a greater probability of estrous expression at first ovulation. Concentrations of plasma cholesterol were positively associated with expression of estrus at first ovulation, interval from calving to conception, and likelihood of conception and pregnancy. Greater concentrations of nonesterified fatty acids in plasma were associated with a lower probability of conception by d 150 of lactation. Increased yield of fat-corrected milk during early lactation was negatively associated with expression of estrus at first ovulation and probability of pregnancy by d 150 of lactation. Cows of high genetic merit were less likely to show signs of estrus at first ovulation. Cows fed the high rumen-degradable-protein diet that also lost more body weight during early lactation were less likely to conceive at first service and to have a prolonged interval from calving to conception. Continued selection for increased production of milk and a more negative nutrient balance during early lactation may reduce reproductive performance particularly for cows fed high concentrations of rumen-degradable protein.

Indications and implications for testing of milk urea in dairy cattle: A quantitative review. Part 2. Effect of dietary protein on reproductive performance

DIETARY PROTEIN AND DAIRY COW FERTILITY: Feeding more dietary protein has been negatively associated with dairy cow fertility in some but not all studies. We used meta-analysis to examine the relationship between dietary crude protein and conception rate. While a higher intake of dietary crude protein significantly lowered conception rate, the potential for feeding less degradable dietary protein to modify this relationship was not demonstrated. MILK UREA CONCENTRATIONS AND DAIRY COW FERTILITY: The use of milk urea as an indicator of dietary energy and protein intake and as an indicator of reproductive performance has been questioned. We found that changes in urea concentration in body fluids explained only 25% (p = 0.08) of the variance in conception rate after conducting a meta-analysis of available studies. INTERPRETATION OF MILK UREA CONCENTRATIONS: High intakes of dietary protein may induce adaptations in urea metabolism, and the negative relationship identified between high intakes of dietary protein and fertility for Northern Hemisphere dairy herds may not necessarily apply in Australasian dairy herds. Because of the potential for cows to adapt to high protein diets, the use of a single milk urea determination on a herd will have limited value as an indicator of nutritional status and little value as a predictor of fertility.

Indications and implications for testing of milk urea in dairy cattle: A quantitative review. Part 1. Dietary protein sources and metabolism

MILK UREA CONCENTRATIONS IN DAIRY CATTLE: There has been increased use of milk urea concentration as an indicator of dietary protein intake and protein metabolism in dairy cattle over recent years. The value of milk urea content data in predicting dietary composition, particularly for pasture-fed cattle, has not been well described. PROTEIN METABOLISM AND UREA SYNTHESIS: Many factors influence the degradation of dietary proteins in the rumen, post-ruminal protein metabolism and urea synthesis in cattle. Strong positive correlations between nitrogenous fertiliser use and the crude protein content of pastures were identified by use of meta-analysis. Similar strong positive correlations were noted between dietary protein intake, rumen ammonia and plasma urea concentrations. The costs of urea synthesis include energy losses, and importantly, the loss of endogenous amino acids, which are deaminated in the synthesis of urea. MILK UREA AS AN INDICATOR OF PROTEIN METABOLISM: Urea concentrations in blood, plasma and milk are strongly correlated. Milk is an adequate indicator of blood and plasma urea content, but non-nutritional factors may significantly influence milk urea concentrations. Recommendations for dietary protein management based on milk urea concentrations must be undertaken with care.

Resumption of ovarian activity in zebu cows (Bos indicus) in the humid tropics: influence of body condition and levels of certain blood components related to nutrition

This study investigated the relationship between resumption of ovarian activity and body condition in a herd of 20 zebu cows in the humid tropics. Blood chemistry profiles to monitor nutritional status were also evaluated. Plasma progesterone was used to determine ovarian activity. During the study, which lasted 18 weeks post partum, 7 of the animals resumed ovarian activity while 13 remained in the anoestrous stage. The beginning of the first luteal phase was registered on day 87 +/- 19 (range 60 to 106). The animals which resumed cyclicity were in significantly better body condition and had significantly higher mean body weight than anoestrous cows. In the group which resumed ovarian activity, calcium levels decreased significantly from 3 weeks before until the first rise of progesterone in the first normal cycle. The study was divided into 2 periods corresponding to weeks 0 to 8 (I) and 9 to 18 (II) based on the finding that until week 8 all animals were reproductively inactive. During period I there were no significant differences between the groups in blood concentrations of albumin, glucose, urea, cholesterol, calcium and phosphorus. During period II albumin was significantly higher and urea significantly lower in the cows resuming ovarian activity. The results suggest that cows able to maintain their body condition from calving through the early post-partum period will have shorter intervals to first post-partum oestrus than cows which have lost body weight. The lower urea and higher albumin levels in the cyclic animals probably reflected a better feed efficiency--the demands of lactation were compensated by an altered nitrogen metabolism.

Correlation between energy balance and fertility in Finnish dairy cows

The effect of serum glucose, ASAT and urea on reproductive performance was studied in 45 Finnish dairy cows from 8 different herds. Blood samples were taken a month before calving as well as 2 weeks and 2 months after calving. Serum urea, ASAT and glucose were used as indicators of metabolic and energy balance. Glucose and ASAT concentrations were significantly correlated with fertility 2 weeks after calving, but not before calving or 2 months after calving. Antepartum, 60% of the cows had a low urea level; at 2 weeks and at 2 months postpartum 89% and 65%, respectively had low levels of urea. The cows were divided into groups as follows: low or high (greater than or equal to 2.9 mmol/l) glucose level and low or high (greater than or equal to 2.5 mmol/l) urea level. Low levels of glucose and/or urea in puerperium were associated with poor fertility. The intervals from calving to first insemination and conception were shorter in the group with high glucose and high urea than in the group with low values. The cows with the shortest intervals from calving to first insemination and conception showed adequate metabolic balance (high levels of urea and glucose). Clinical ketosis had an adverse affect on intervals from calving to first insemination and on conception. Intervals from calving to first insemination and to conception were significantly (p less than 0.01) longer in ketotic cows than in non-ketotic ones. Liver damage, reflected as elevated activity of ASAT, was associated with poor fertility. If shorter calving intervals are desired, adequate energy balance in puerperium is essential.

Finnish dairy cows: energy balance and seasonal variation in fertility

The relationship between metabolic balance and seasonal variations in fertility was studied in middle Finland in 104 cows that had calved from February to June. The cows were kept indoors until the end of May when they turned out to pasture. Urea and acetone concentrations in milk were used to evaluate metabolic balance, and progesterone assays were used to determine the onset of ovarian activity. The length of ovarian quiescence was influenced by the season. All cows that calved in May had started their ovarian activity by 7 weeks postpartum, while 64% and 70%, respectively, of those that calved in March and April had increased levels of progesterone (p less than 0.01). Cows that calved in March had the highest concentrations of acetone beyond 4 weeks postpartum. On pasture the energy balance reached equilibrium in five weeks postpartum, whereas cows kept indoors had an increased level of acetone even 9 weeks after parturition. No correlation was found between urea levels and reproductive performance. The most harmful effect of increased acetone concentration was found in late puerperium. The adverse effect of low energy level was also observed when cows were on pasture; increased level of acetone was significantly correlated with a long interval from calving to first insemination and conception (p less than 0.05). Cows that calved in late spring had the shortest interval from calving to first insemination and conception. In dairy cows an imbalance in energy metabolism in late puerperium affects reproductive performance negatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlation between energy balance and fertility in Finnish dairy cows

The effect of serum glucose, ASAT and urea on reproductive performance was studied in 45 Finnish dairy cows from 8 different herds. Blood samples were taken a month before calving as well as 2 weeks and 2 months after calving. Serum urea, ASAT and glucose were used as indicators of metabolic and energy balance. Glucose and ASAT concentrations were significantly correlated with fertility 2 weeks after calving, but not before calving or 2 months after calving. Antepartum, 60% of the cows had a low urea level; at 2 weeks and at 2 months postpartum 89% and 65%, respectively had low levels of urea. The cows were divided into groups as follows: low or high (greater than or equal to 2.9 mmol/l) glucose level and low or high (greater than or equal to 2.5 mmol/l) urea level. Low levels of glucose and/or urea in puerperium were associated with poor fertility. The intervals from calving to first insemination and conception were shorter in the group with high glucose and high urea than in the group with low values. The cows with the shortest intervals from calving to first insemination and conception showed adequate metabolic balance (high levels of urea and glucose). Clinical ketosis had an adverse affect on intervals from calving to first insemination and on conception. Intervals from calving to first insemination and to conception were significantly (p less than 0.01) longer in ketotic cows than in non-ketotic ones. Liver damage, reflected as elevated activity of ASAT, was associated with poor fertility. If shorter calving intervals are desired, adequate energy balance in puerperium is essential.

Metabolic balance and reproductive performance in Finnish dairy cows

The relationships between energy level and reproductive performance were studied in 24 dairy cows, which were fed grass silage. Serum glucose and blood acetoacetate (AA) and beta-hydroxybutyrate (HB) were measured 10, 15, 30 and 50 days postpartum. The cows were examined clinically by rectal palpation 3 times a week during 8 weeks postpartum. The time required for the complete uterine involution and the onset of ovarian activity were recorded. The pregnancy rate at the first insemination and the interval from calving to conception were obtained for each cow. The correlations between blood glucose and ketone bodies were negative, but they were significant only at days 15 and 30 for AA and at day 30 for HB. A low energy level in early puerperium caused a delay in uterine involution and in the onset of ovarian activity. The low energy balance in puerperium prolonged the interval from calving to the first insemination and the interval from calving to conception. The earlier the ovarian activity started the shorter was the interval from calving to conception. The energy level in early puerperium had a greater influence on the interval from calving to conception, whereas in late puerperium it was more important with regard to the interval from calving to the first insemination. Blood glucose had also a significant effect on the reproductive performance. The adverse influence of ketone bodies on fertility depended on duration and timing of their increased levels; the longer and later in puerperium the cow has elevated ketone bodies, the lower is the fertility.(ABSTRACT TRUNCATED AT 250 WORDS)