The effect of sire predicted transmitting ability for production traits on fertility, survivability, and health of Holstein dairy cows

The effect of Presynch-Ovsynch protocol with or without estrus detection on reproductive performance by parity, and the long-term effect of these different management strategies on milk production, reproduction, health and survivability of dairy cows

During the Presynch-Ovsynch protocol, at least half of the cows enrolled display signs of estrus, which can present as an opportunity for cows to be inseminated before the completion of the protocol. The primary objective of this study is to compare two management strategies for first service using the Presynch-Ovsynch protocol: insemination at completion of the Presynch-Ovsynch program (TAIonly) or insemination after estrus detection during the Presynch-Ovsynch protocol, with the remainder of cows being inseminated at timed artificial insemination (ED + TAI). Cows inseminated at completion of the protocol have a longer voluntary waiting period, which could potentially extend their lactation length, allowing them to recover BCS at the end of their lactation and ultimately impacting their subsequent lactation. Therefore, this study has a secondary objective to evaluate the long term impact of these two strategies on reproductive outcomes, culling, milk production and health during the subsequent lactation. A total randomized field trial study design was used, and a total of 3489 cows were randomly enrolled to one of the treatment groups: ED + TAI or TAIonly. Cows enrolled in the TAIonly started the Presynch protocol receiving two injections of PGF2α at 55 ± 3 and 69 ± 3 DIM. They were subsequently submitted to the Ovsynch protocol: GnRH at 81 ± 3 DIM, PGF2α at 88 ± 3 DIM, and GnRH at 90 ± 3 DIM, and then inseminated at fixed time at 91 ± 3 DIM. Cows enrolled in the ED + TAI were submitted to the same synchronization protocol, but they were eligible to be inseminated at any time after the beginning of the synchronization protocol, if detected in estrous. During the experimental lactation, the effect of treatment on first service conception rate (FSCR) was conditional to parity: no difference among primiparous cows, but for multiparous cows, the FSCR was 41.2% and 35.3% for TAIonly and ED + TAI, respectively. Although TAIonly strategy increased the lactation length for primiparous and multiparous, no differences were observed on lactation and reproductive performances. The rate at which cows conceived, and the calving to conception interval during the subsequent lactation was not affected by management strategy. Additionally, no differences were observed in milk production during the experimental and subsequent lactations. The effect of management strategy on survivability was conditional to parity: no differences were observed for multiparous cows, while primiparous ED + TAI cows tended to be less likely to be culled than TAIonly counterparts. Additionally, no differences in health outcomes during the subsequent lactation were observed.

Comparison of breeding values among cows with exceptional longevity and their contemporary herdmates in German Holsteins

Abstract. The present analysis compares the estimated breeding values (EBVs), relative breeding values (RBVs), and daughter yield deviations (YDs) of cows with exceptional longevity with their contemporary herdmates. In addition, the relative breeding values of their sires were compared among these two daughter groups; the RBVs of the sires were also compared with the proportion of their daughters with exceptional longevity. Data included 5037 sires born between 1963 and 1996 with a total of 61 988 daughter; of these sires, 486 had sired daughters that completed more than nine lactations (exceptional cows) and 4957 sires had sired the contemporary herdmates. Exceptional cows had on average significantly lower EBVs for milk yield, fat and protein yield, and significantly lower YDs for milk and protein yield in the first three lactations, significantly lower RBVs for milk production and type but significantly higher RBVs for somatic cell score and functional longevity. The sires of exceptional cows had significantly higher RBVs for somatic cell count (RZS), functional longevity (RZN), and fitness (RZFit) in comparison to the sires of contemporary herdmates. Correlations among the proportion of exceptional cows per sire and RZN, RZS as well as RZFit were positive, whereas milk production (RZM) showed a negative correlation. An increase in the number of cows with exceptional longevity may be possible through a relative total breeding value with high positive weights for RZN, RZS, and RZFit but negative weights for RZM and type (RZE).

Genetics of bovine abomasal displacement

Displacement of the abomasum (DA) is a common inherited condition in Holstein cows. This article reviews the genetics of DA including risk factors, genetic parameters and molecular genetic results. Breeds other than Holsteins affected by DA include Guernseys, Jerseys, Brown Swiss, Ayrshires and Simmental-Red Holsteins. In most DA cases, left displacements of the abomasum (LDA) are seen. Lactation incidence rates are higher for DA in first lactation Holsteins compared to later lactations. For Holstein cows, heritability estimates for DA are between 0.03 and 0.53. Genetic correlation estimates among DA and milk production traits range from positive to negative. Genome-wide significant genomic regions associated with LDA are located on bovine chromosomes (BTA) 1, 3, 11, 20 and 23. Motilin-associated single nucleotide polymorphisms on BTA23 exhibit a functional relationship with LDA. Pathways for deposition of calcium, insulin-dependent diabetes mellitus and synaptic transmission are significantly related to LDA in Holsteins. Deciphering the DA-associated genomic regions and genes may be an important step in the quest to understand the underlying disease-causing mechanisms and in unravelling mutations with a causal relationship to DA.