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Associations between pregnancy associated glycoproteins in milk and calving characteristics in seasonal-calving pasture-based dairy cows.

R. C. Doyle

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06-23-2020

Abstract:

277
Associations between pregnancy associated glycoproteins in milk and calving characteristics in seasonal-calving pasture-based dairy cows.
R. C. Doyle*1,2, M. M. Herlihy1, M. C. Lucy2, S. T. Butler1. 1Teagasc Fermoy, Cork, Ireland, 2University of Missouri Columbia, MO.

The objective was to retrospectively examine the effect of calf sex (CS; female, male), calf birth weight (CBW; small ≤ 30kg, medium 30—36kg, large ≥ 36kg) and calving difficulty (CD; normal or difficult) on weekly milk PAG S-N values between wk 5 and 21 of pregnancy. Only cows that conceived to first AI and maintained pregnancy were analyzed (n = 259). PAG S-N values were not normally distributed. An appropriate Box-Cox transformation was identified, therefore, and the transformed PAG S-N values were analyzed using generalized linear mixed-models (presented as back-transformed LS Means and 95% CI). There was an interaction (P = 0.001) between CS and week because pregnancies with female offspring had greater PAG S-N at wk 5 (2.11, [1.92, 2.30]) and 6 (1.88, [1.77, 1.99]) of pregnancy compared with pregnancies with male offspring (1.98, [1.81, 2.15] and 1.77 [1.66, 1.89]). An interaction (P < 0.001) between CBW and week of pregnancy was detected whereby medium CBW calves had greater PAG S-N values at wk 5 (2.20 [1.96, 2.45]) and 6 (1.95, [1.79, 2.1]) compared with low (1.83 [1.62, 2.05] and 1.74 [1.58, 1.90]) and high (2.10 [1.90, 2.32] and 1.80 [1.66, 1.95]) CBW calves, respectively. Pregnancies with female offspring had greater (P < 0.001) PAG S-N values pre-nadir (1.83, [1.80, 1.86]) and lesser values post nadir (2.50, [2.48, 2.52]) versus pregnancies with male offspring (1.67 [1.64, 1.70] and 2.56 [2.53, 2.58], respectively). Pregnancies with low CBW calves had greater (P < 0.001) pre-nadir peak S-N values (1.84 [1.81, 1.87]) than pregnancies with medium (1.73 [1.69, 1.76]) and large (1.69 [1.65, 1.71]) CBW calves. Normal CD had greater (P = 0.01) pre nadir PAG S-N values (1.78, [1.76, 1.80]) compared with cows with a difficult CD (1.72, [1.68, 1.76]). Cows carrying a female calf or carrying calves with less CBW had the greatest milk PAG S-N. Calf characteristics were associated with differences in weekly PAG S-N values. Calf characteristics, including CS and CBW, were associated with prior differences in weekly milk PAG S-N values between wk 5 and 21 of pregnancy.

Keywords: embryo, calf, pasture.

Biography: I completed a Bachelors of Agricultural Science in University College Dublin in 2016 for which I received a first class honors degree. I am currently a PhD student with the University of Missouri and Teagasc splitting my time between both institutions trying to elucidate the physiological mechanisms that underpin the most important drivers of productivity; milk output and fertility. The PhD I will be carrying out aims to examine the effects of nutrition and genetics on fertility in dairy cows of high and average EBI. I have a background in sheep farming but have been lucky to work with some of the Ireland's top researchers and farmers in the dairy industry. I've always had a huge interest in Agricultural Industry and its importance for our economy. My aim is to further the knowledge on the factors contributing to reproductive performance and improve the productivity and efficiency of the Irish dairy industry.