Phenotypic relationships between milk protein percentage, reproductive performance and body condition score in Irish dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Sciences (MSc) at Massey University, Palmerston North, New Zealand

Simple item page
dc.contributor.authorYang, Linna
dc.date.accessioned2010-05-24T01:56:13Z
dc.date.availableNO_RESTRICTIONen_US
dc.date.available2010-05-24T01:56:13Z
dc.date.issued2009
dc.description.abstractA positive phenotypic correlation between milk protein percentage and reproductive performance in dairy cattle, especially during early lactation has been recently reported. The objective of this study was to quantify the relationship between milk protein percentage and different measures of fertility in Irish, seasonal calving, dairy cattle using data from experiments comparing strains of Holstein-Friesian cows under different feeding systems. The relationships between body condition score, milk production and fertility were also investigated. The data used in this study consisted of 584 lactation records over a 5-yr period. Principal component analysis and logistic regression was used to study the relationship between milk protein percentage and fertility performance of the cow. Greater milk protein percentage during the first 60 days post-calving was associated with better reproductive performance. The probability of a cow being submitted in the first 21 days of the breeding season increased with increased milk protein percentage during early lactation. Similarly, the probability of a cow becoming pregnant to its first service or to the whole breeding season also increased. Cows were classified as either high or low milk protein percentage based on their protein percentage over the whole lactation. Cows in the high milk protein group had a 7% greater conception rate compared to cows in the low protein percentage group. In conclusion, cows with higher protein percentage, especially during early lactation are submitted earlier in the breeding season, and have a higher conception rate. Physiologically, the shortage of glucose caused by negative energy balance restricts the synthesis of milk protein in the udder. On the other side, negative energy balance also causes the reduction of IGF-I, LH and oestradiol, which consequently delay the ovarian follicular development and finally reduces fertility. Therefore, there is a biological explanation for the association between milk protein percentage and fertility performance.en_US
dc.identifier.urihttp://hdl.handle.net/10179/1337
dc.language.isoenen_US
dc.publisherMassey Universityen_US
dc.rightsThe Authoren_US
dc.subjectMilk protein percentageen_US
dc.subjectDairy cattle reproductionen_US
dc.subjectHolstein-Friesian cattleen_US
dc.subject.otherFields of Research::300000 Agricultural, Veterinary and Environmental Sciences::300400 Animal Production::300402 Animal reproductionen_US
dc.titlePhenotypic relationships between milk protein percentage, reproductive performance and body condition score in Irish dairy cattle : a thesis presented in partial fulfilment of the requirements for the degree of Master of Sciences (MSc) at Massey University, Palmerston North, New Zealanden_US
dc.typeThesisen_US
massey.contributor.authorYang, Linna
thesis.degree.disciplineAnimal Scienceen_US
thesis.degree.grantorMassey Universityen_US
thesis.degree.levelMastersen_US
thesis.degree.nameMaster of Sciences (M.Sc.)en_US
Files
Original bundle
Now showing 1 - 2 of 2
Thumbnail Image
Name:
02_whole.pdf
Size:
763.44 KB
Format:
Adobe Portable Document Format
Description:
Download
Thumbnail Image
Name:
01_front.pdf
Size:
107.03 KB
Format:
Adobe Portable Document Format
Description:
Download
License bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
license.txt
Size:
896 B
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Theses and Dissertations