Effect of norgestomet or norgestomet and gonadotropin-releasing hormone on attainment of puberty in beef heifers

1996 ◽  
Vol 76 (3) ◽  
pp. 477-479 ◽  
Author(s):  
C. L. Henderson ◽  
H. L. Miller
Keyword(s):  
Key Words ◽  
Reproductive Performance ◽  
Hormonal Treatment ◽  
Subsequent Pregnancy ◽  
Gonadotropin Releasing Hormone ◽  
Beef Heifers ◽  
Releasing Hormone

An experiment was conducted using 133 crossbred beef heifers randomly assigned to three treatments. All heifers were bled weekly to monitor concentration of progesterone. Norgestomet-treated heifers were 26.2 d younger (P < 0.01) and 21.6 kg lighter (P < 0.05) than controls at puberty. Norgestomet plus GnRH-treated heifers were 30.9 d younger (P < 0.01) and 18.8 kg lighter (P < 0.05) than controls at puberty. The effects of hormonal treatment on subsequent pregnancy and calving rates were variable. Key words: Beef heifers, puberty, norgestomet, GnRH, reproductive performance

A comparison of two estrus synchronization methods in beef heifers

1998 ◽  
Vol 78 (3) ◽  
pp. 437-439
Author(s):  
L. A. Stephens ◽  
R. Rajamahendran
Keyword(s):  
Key Words ◽  
Pregnancy Rate ◽  
Gonadotropin Releasing Hormone ◽  
Estrus Synchronization ◽  
Beef Heifers ◽  
Releasing Hormone ◽  
Prostaglandin F

This study compared the use of two injections of prostaglandin F2α(PGF2α) given 11 d apart with the use of gonadotropin releasing hormone (GnRH) followed by PGF2α after 7 d for synchronizing estrus in beef heifers. Heifers synchronized with GnRH and PGF2α showed weak signs of estrus and were more difficult to inseminate. There were no significant differences in synchronization rate and pregnancy rate. Key words: Estrus synchronization, beef heifers, gonadotropin releasing hormone, prostaglandin F2α

7 PREGNANCY RATES IN BEEF HEIFERS SYNCHRONIZED WITH A SHORTENED OESTRADIOL-BASED TREATMENT THAT PROVIDES FOR A PROLONGED PROESTRUS

2015 ◽  
Vol 27 (1) ◽  
pp. 96 ◽  
Author(s):  
A. Menchaca ◽  
R. Nuñez-Olivera ◽  
F. Cuadro ◽  
G. Bo
Keyword(s):  
Treatment Group ◽  
Day Treatment ◽  
Fixed Time ◽  
Gonadotropin Releasing Hormone ◽  
Pregnancy Rates ◽  
Device Removal ◽  
Beef Heifers ◽  
Releasing Hormone ◽  
Secondary Objective ◽  
To Receive

An oestradiol-based protocol (named J-Synch) has been developed recently with the aim of providing for a longer proestrus, enhancing the development of the dominant follicle before ovulation, and increasing pregnancy rates following fixed-time AI (FTAI) in heifers (de la Matta and Bo 2012 Taurus 55, 17–23). Two experiments were performed in Uruguay with 1953 Angus × Hereford crossbred heifers to compare pregnancy rates obtained with the J-Synch protocol with the conventional 7-day oestradiol-based protocol. A secondary objective was to determine the effects of the time of FTAI and the addition of eCG at the time progestin device removal on pregnancy rates. In Experiment 1, 966 heifers received a DIB device (0.5 g of progesterone, Syntex, Buenos Aires, Argentina) plus 2 mg of oestradiol benzoate IM (Syntex) on Day 0. Heifers in the conventional treatment group (n = 485) received cloprostenol (500 μg, Ciclase DL, Syntex) and oestradiol cypionate (0.5 mg, Cipiosyn, Syntex) IM and had their DIB removed on Day 7 a.m. Heifers in this group were then subdivided to be FTAI on Day 9 a.m. or p.m. (i.e. 48 or 56 h after DIB removal). Heifers in the J-Synch treatment group (n = 481) received cloprostenol IM and DIB removal on Day 6 p.m. and received gonadotropin-releasing hormone (100 μg gonadorelin acetate, Gonasyn Gdr, Syntex) on Day 9 a.m.; heifers were then FTAI on Day 9 a.m. or p.m. (i.e. 60 or 72 h after DIB removal). All heifers in this experiment were also treated with 300 IU of eCG (Novormon, Syntex) at DIB removal. In Experiment 2, 987 heifers were treated with the J-Synch protocol as described in Experiment 1. At device removal (Day 6 p.m.), heifers were divided to receive (n = 488) or not (n = 499) 300 IU of eCG IM at that time and were further subdivided to receive gonadotropin-releasing hormone and FTAI on Day 9 a.m. or p.m. (i.e. 60 or 72 h after DIB removal). Pregnancy rates were determined by ultrasonography 30 days after FTAI. Data were analysed using logistic regression, and results are shown in Table 1. J-Synch-treated heifers tended (P < 0.1) to have higher pregnancy rates following FTAI, whereas time of FTAI only affected pregnancy rates following the conventional 7-day treatment (P < 0.05). However, removal of eCG from the J-Synch protocol in Experiment 2 resulted in reduced pregnancy rates when inseminations were done on Day 9 p.m. (P < 0.05). In summary, the addition of eCG to the J-Synch protocol provided for a wider window of insemination times facilitating FTAI in large groups of beef heifers. Table 1.Effect of length of progestin insertion, time of insemination and eCG treatment on pregnancy rates in beef heifers

The effects of catch-up (compensatory) growth on reproductive performance of beef heifers

1996 ◽  
Vol 76 (4) ◽  
pp. 523-529 ◽  
Author(s):  
Dinah Boadi ◽  
M. A. Price
Keyword(s):  
Key Words ◽  
Reproductive Performance ◽  
Compensatory Growth ◽  
Reproductive Efficiency ◽  
Feed Restriction ◽  
Early Weaning ◽  
Beef Heifers ◽  
Catch Up ◽  
Calving Performance

Fifty-four heifer calves were allocated to five feeding/weaning treatments at birth in April/May 1990: 1) VEW (n = 11) dams feed-restricted for 3 mo before and 2 mo after calving; calves weaned in June onto gram-supplemented pasture and then into a drylot in October; 2) EW1 (n = 10) dams not restricted; calves weaned in August (unsupplemented pasture) into drylot in October; 3) EW2 (n = 10) dams not feed-restricted; calves weaned directly into drylot in August; 4) LW1 (n = 12) dams feed restricted for 3 mo before, but not after calving; calves weaned directly into drylot in October, 5) LW2 (n = 11): dams not restricted; calves weaned directly into drylot in October. The very early (VEW) and early (EW1, EW2) weaned heifers grew significantly slower than the later-weaned ones (LW1, LW2) from birth to September, and were still significantly lighter at 12–13 mo of age (May 1991). Recovery of liveweight-for-age was achieved by EW2 heifers by 18 mo and VEW and EW1 by about 23 mo of age. Early weaning treatments delayed age but not weight at first estrus (P < 0.05) yet the number of heifers conceiving and calving, and all associated reproductive data, including rebreeding success were unaffected by treatment (P > 0.05). Despite a delay in first estrus, reproductive efficiency and calving performance were not impaired by early feed restriction in heifers conceiving at 15 mo of age. Key words: Beef heifers, feed restriction, fertility, reproduction, catch-up growth

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