Effect of dietary protein content on the fertility of dairy cows during early and mid lactation

• Published in: Journal of dairy science 2009-06, Vol.92 (6), p.2737-2746
• Main Authors: Law, R.A., Young, F.J., Patterson, D.C., Kilpatrick, D.J., Wylie, A.R.G., Mayne, C.S.
• Format: Article
• Language: English
• Subjects: Animal productions; Animals; Biological and medical sciences; Cattle; Cattle Diseases - physiopathology; conception; dairy cows; Dairying; Diet - veterinary; dietary protein; Dietary Proteins - administration & dosage; early lactation; Eating - physiology; Endometriosis - veterinary; energy balance; Energy Metabolism - physiology; experimental diets; Female; female fertility; Fertility - physiology; Food industries; Fundamental and applied biological sciences. Psychology; Holstein; Hormones - blood; Lactation - physiology; mid lactation; Milk - secretion; Milk and cheese industries. Ice creams; pregnancy rate; progesterone; Progesterone - blood; protein content; protein intake; reproduction; ruminant nutrition; Terrestrial animal productions; Vertebrates
• ISSN: 0022-0302; 1525-3198
• DOI: 10.3168/jds.2008-1420

Ninety autumn-calving Holstein dairy cows (45 primiparous and 45 multiparous; mean parity, 3.1) were allocated to 1 of 3 treatments; 173, 144, or 114g of crude protein (CP)/kg of dry matter (DM) from calving until d 150 of lactation. On d 151 of lactation, half the animals receiving 114g of CP/kg of DM went onto 144g of CP/kg of DM, half of the animals receiving 144g of CP/kg of DM went onto 173g of CP/kg of DM, and half of the animals receiving 173g of CP/kg of DM went onto 144g of CP/kg of DM, with the remaining animals staying on their original treatments. This resulted in 6 treatments in mid to late lactation: 114/114; 144/144; 173/173; 114/144; 144/173; and 173/144g of CP/kg of DM. Overall, 95.3% of cows intended for breeding conceived during a 6-mo breeding period. The average pregnancy rates to first service and first plus second service were 30.9% [standard error of the difference (SED), 0.05] and 56.7% (SED, 0.05) respectively. The average 100 d in-calf rate from the start of the breeding period was 70.5%, and at least one abnormal progesterone profile was observed in 62% of animals. An increase in dietary protein content decreased the requirement for treatment of metritis. There was no effect of dietary protein content on any of the reproductive or progesterone measures; for example, days to conception, calving interval, 100 d in-calf rate (from commencement of breeding), days to onset of luteal activity, average luteal phase, average interovulatory interval, or average interluteal interval. An increase in dietary protein content decreased the average daily energy balance. A more positive energy balance was associated with an increased requirement for the treatment of metritis in the current study. Cumulative energy balance was positively associated with conception. There was no effect of the concentration of plasma urea on any of the reproductive variables; however, the concentration of serum leptin was favorably associated with the time to progesterone increase above 3ng/mL, which has been deemed essential for embryo survival. Additionally, the average peak concentration of progesterone and the duration of the average luteal phase were favorably associated with the interval from calving to conception. The latter relationships emphasize the importance of progesterone in achieving and maintaining pregnancy.