Comparison of F1 Bos indicus x Hereford cows in central Texas: II. Udder, mouth, longevity, and lifetime productivity.

Postpartum udder characteristics, aged mouth condition scores, and cow survival, longevity, and productivity were evaluated for 15 yr on F1 cows in central Texas (temperate winters and subtropical summers). The cows (n = 116) were progeny of Angus, Gray Brahman, Gir, Indu-Brazil, Nellore, and Red Brahman sires and Hereford dams. Crossbred cows sired by Nellore had smaller (P < 0.05) postpartum teat length than cows of all other crossbred groups and smaller (P < 0.10) postpartum teat diameter than Indu-Brazil and Red Brahman crossbreds. The Nellore crossbred cows had larger (P < 0.10) postpartum udder support scores (more well-supported udders) than Gir, Indu-Brazil, and Red Brahman crossbreds. As 14-yr-old cows, Angus crossbreds had lower (P < 0.05) mouth scores (indicative of one or more missing incisors) than Bos indicus crossbreds. Under actual and artificial (records were removed) culling procedures, Nellore crossbreds had the highest cow survival to age 14 and the highest longevity. Indu-Brazil crossbreds tended to be the lowest for both survival and longevity. Curves were fitted by nonlinear regression procedures to the adjusted frequencies of cows remaining at each age; scale and shape parameters were estimated and compared for the different breed groups. Breed group cow survival rates, calf crop weaned, and calf weaning weights were used 1) to construct population projection and production matrices for each breed group and 2) to generate breed group vectors containing projected age distributions and production information. Cows sired by Nellore and Gir were projected to require the fewest purebred cows to generate replacement heifers and to have the most calves and the largest total calf weight sold per year.     

Comparison of Bos taurus-Bos indicus breed crosses with straightbred Bos indicus breeds of cattle for maternal and individual traits

Data were analyzed to compare crossbred females produced by crossing exotic Angus and Red Poll males to indigenous Ankole, Boran and Small East African Zebu (Zebu) females with straightbred females of the Ankole, Boran and Zebu breeds at the Ruhengere Field Station in the Ankole District of Southwestern Uganda. Progeny of the straightbred and crossbred dams were by Friesian, Brown Swiss and Simmental sires. Crossbred exotic X indigenous dams were favored over straightbred indigenous dams by 13.7% (P less than .01) in calf birth weight and by 14.8% (P less than .01) in calf weaning weight. Cross-bred cows exceeded (P less than .01) straightbred cows by 61.9% (48.5 kg) in calf weight weaned per cow exposed to breeding. Crossbred cows weighed 37, 46 and 42 kg more (P less than .01) than straightbred cows at parturition, weaning and cow mean weight, respectively. Angus X Boran and Red Poll X Boran crossbred dams were compared specifically with straightbred Boran dams. Exotic (Angus, Red Poll) X Boran crossbred dams exceeded straightbred Boran dams by 27.0% (P less than .05) in calf crop born, by 8.3% (P less than .05) in progeny birth weight and by 14.7% (P less than .01) in progeny weaning weight. Weight of calf weaned per cow exposed to breeding favored (P less than .01) the Angus X Boran and Red Poll X Boran crossbred dams over the straightbred Boran dams by 50.5% (50 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Evaluation of reciprocal differences in Bos indicus x Bos taurus backcross calves produced through embryo transfer: I. Birth and weaning traits

Angus (A) and Bos indicus (B; Brahman or Nellore) reciprocal backcross, embryo transfer calves, belonging to 28 full-sib families, were evaluated for differences in birth weight, gestation length, and weaning weight. Two methods were investigated; method I made no distinction between how the F(1) parents were produced, whereas method II distinguished between the 2 types of F(1) parents (AB vs. BA corresponding to A x B vs. B x A, respectively). Bos indicus backcross calves had a 4.3 d longer (P < 0.05) gestation length but did not differ in their average birth weight from A backcrosses. Among B backcrosses, B x F(1) calves had a 5.2 d longer (P = 0.01) gestation length than F(1) x B calves (290.5 vs. 285.3, respectively). Under method II analysis, there was a consistent trend for gestation length, in which BA F(1) parents produced calves that ranked greater than calves from AB F(1) parents, as sires and dams. Crosses with a greater proportion of B in the sire in relation to the amount in the dam had a heavier (P < 0.05) birth weight (F(1) x A and B x F(1); 38.1 and 38.4 kg, respectively) than their respective reciprocal crosses (A x F(1) and F(1) x B; 34.3 and 33.5 kg, respectively). The F(1) x A and B x F(1) crosses showed a large difference in birth weight between males and females (5.3 and 4.1 kg, respectively), whereas A x F(1) and F(1) x B crosses showed a small difference (P > 0.10) in birth weight between males and females (1.5 and 1.1 kg, respectively). Further examination within each sex showed a difference between male reciprocals that was generally much larger than that between female reciprocals. Calves with a greater percentage of B in the sire compared with the proportion in the dam ranked heavier for weaning weight as for birth weight, though these differences were not significant. In breeding systems involving B x Bos taurus crosses, even when using embryo transfer, not only does the breed composition of the calves affect their preweaning performance, but the particular cross that produces the calves also should be considered in making breeding decisions.     

Characterization of breeds of Bos indicus and Bos taurus cattle for maternal and individual traits

Angus, Boran and Red Poll sires were mated to Ankole, Boran and small East African Zebu (Zebu) females to produce the cows characterized in this study, which produced calves by Friesian, Brown Swiss, Simmental, Boran and Red Poll sires. Individual traits included cow parturition weight, cow weight at weaning, cow mean weight and cow weight change from parturition to weaning; maternal traits included calf crop born percentage, preweaning viability percentage, overall viability percentage, birth weight, weaning weight, weight at 12, 18 and 24 mo and calf weight weaned per cow exposed to breeding (productivity index). Cows by Angus and Red Poll sires significantly exceeded cows by Boran sires (all cows in this comparison had Ankole and Zebu dams) in weaning weight of progeny and in cow weight at parturition and at weaning. Cows by Red Poll sires significantly exceeded cows by Boran sires in birth weight of progeny. Progeny of cows by Boran sires significantly exceeded progeny of cows by Angus and Red Poll sires in 24-mo weight. Cows by Angus and Red Poll sires did not differ (P greater than .05) in any of the traits analyzed. Cows with Ankole and Boran dams significantly exceeded cows with Zebu dams (all cows in this comparison had Angus and Red Poll sires) in progeny weight at birth, 18 mo and 24 mo and in cow weight at parturition and at weaning. Cows with Boran dams significantly exceeded cows with Zebu dams in weaning and 12-mo weight of progeny and significantly exceeded cows with Ankole dams in weaning weight of progeny. The significantly heavier weaning weight and significantly lighter 24-mo weight of the 3/4 Bos taurus progeny of cows with Angus and Red Poll sires relative to the 1/2 Bos taurus progeny of cows with Boran sires suggest that cattle that are 1/2 Bos taurus breed composition have greater general adaptation than cattle with 3/4 Bos taurus breed composition in the postweaning nutritive and climatic environment under which this experiment was conducted. Significantly heavier weights of Angus and Red Poll crossbred cows relative to Boran crossbred cows (all breeds crossed on Ankole and Zebu cows) indicate that the two Bos taurus breeds exceed the Boran (Bos indicus) breed in additive direct genetic effects for size when they have general adaptation to the environment.     

Metabolizable energy for maintenance of beef-type Bos taurus and Bos indicus x Bos taurus cows in a dry, temperate climate

Metabolizable energy for maintenance (MEm) was estimated using 123 mature cows of eight diverse breed groups. Cows in each breed group were allotted at random 1) to limit-feeding to approximate maintenance or 2) to ad libitum access to feed. The MEm values were calculated by regression of change in body energy on ME intake. The MEm values for mature Hereford, Red Poll, Hereford x Red Poll, Red Poll x Hereford, Angus x Hereford, Angus x Charolais, Brahman x Hereford, and Brahman x Angus breed types were as follows: 145, 169, 148, 149, 144, 152, 139, and 143 kcal.kg-.75.d-1, respectively. Bos indicus-cross cows ranked lowest for MEm/kg.75. Angus x Hereford cows averaged highest in terms of grams of calf weaned per mature female exposed divided by yearly MEm requirement. Hereford x Red Poll reciprocal crosses on average required 640 kcal less total daily MEm per animal than Hereford and Red Poll straightbreds.     

Induction of ovulation with GnRH and PGF2alpha in lactating Bos taurus x Bos indicus cows

Induction of ovulation for timed artificial insemination (TAI) with the Ovsynch protocol was evaluated in 49 anoestrous and lactating Bos taurus x Bos indicus cows. Palpation per rectum and transrectal ultrasonography were used on Days -30, -20, -10 and 0 (start of treatment) to confirm anoestrus but with the presence of follicles > or = 10 mm, and every other day during treatment to determine ovarian activity. Cows were randomly assigned to: (1) Ovsynch (n = 24; Day 0, 200 microg GnRH; Day 7, 150 microg PGF2alpha; Day 9, 200 microg GnRH + TAI 16 to 20 h later) and (2) control (n = 25; no treatment). Rates of ovulation for the first GnRH injection, detection of a corpus luteum (CL) at PGF2alpha injection, pregnancy and induction of cyclicity were greater (P < 0.05) with Ovsynch. There was no effect of body condition score (P > 0.05). In conclusion, the Ovsynch protocol was not effective in obtaining acceptable pregnancy rate for TAI, but it was effective for induction of cyclicity in anoestrous and lactating Bos taurus x Bos indicus cows under tropical conditions.     

Evaluation of reciprocal differences in Bos indicus x Bos taurus backcross calves produced through embryo transfer: II. Postweaning, carcass, and meat traits

Angus (A) x Bos indicus (B; Brahman or Nellore) reciprocal backcross, embryo transfer calves belonging to 28 full-sib families were evaluated for differences in feedyard initial BW, feedyard final BW, carcass weight, LM area, adjusted fat thickness, intramuscular fat, and Warner-Bratzler shear force. Two methods of analysis were investigated; method I made no distinction between how the F(1) parents were produced, whereas method II distinguished the 2 types of F(1) parents (AB vs. BA, corresponding to A x B vs. B x A, respectively). No significant reciprocal differences for these weight and carcass traits were detected under method I analyses, although the same trend existed for subsequent BW rankings as for birth weight and weaning weight. For each weight phase, the cross that involved a larger proportion of B in the sire in relation to the amount in the dam (F(1) x A and B x F(1)) ranked heavier than the respective reciprocal cross (A x F(1) and F(1) x B). As a whole, A backcross calves had larger (P < 0.001) LM area, more (P < 0.001) marbling, and lower (P < 0.001) Warner-Bratzler shear force than B back-cross calves, but no consistent trends were detected between reciprocal crosses for any of these traits, in contrast with the trends observed for the weight traits. Furthermore, males were heavier than females entering (P < 0.001) and leaving (P < 0.001) the feedyard, produced a heavier carcass (P < 0.001), and had larger LM area (P < 0.05) with less adjusted fat (P < 0.001). No difference existed between the sexes for Warner-Bratzler shear force or marbling. No interactions involving sex, sire type, and dam type were observed for any of these traits. The results were similar under methods I and II analyses, with the exception that a significant sire type x dam type interaction was observed for initial feedyard BW. Results from this study suggest that for weight-related traits, both the breed constitution of the embryo transfer calf and the cross that produces the calf play an important role in its ultimate performance for B crossbred calves. For body composition and meat-related traits, it appears that the breed makeup of the embryo transfer calf itself is more important to animal performance than the specific cross used to produce the calf.     

Purebred-crossbred performance and genetic evaluation of postweaning growth and carcass traits in Bos indicus x Bos taurus crosses in Australia

Growth and carcass data on 7,154 cattle from a purebred project and 1,241 cattle from a crossbred project, comprising 916 first-crosses and 325 purebred Brahman controls, were analyzed to estimate genetic parameters, including the genetic correlations between purebred and crossbred performance (rpc). The data also allowed the estimation of sire breed means for various growth and carcass traits. Crossbred calves were produced using 9 Angus, 8 Hereford, 7 Shorthorn, 14 Belmont Red, and 8 Santa Gertrudis sires bred to Brahman dams. These same sires produced 1,568 progeny in a separate purebreeding project. Cattle in both projects were managed under two finishing regimens (pasture and feedlot) to representative market live weights of 400 (domestic), 520 (Korean), and 600 kg (Japanese). The traits studied included live weight at around 400 d of age (400W), hot carcass weight (CWT), retail beef yield percentage (RBY), intramuscular fat percentage (IMF), rump fat depth (P8), and preslaughter ultrasound scanned eye muscle area (SEMA). Estimated breeding values (EBV) of sires from their BREEDPLAN genetic evaluations were used to assess their value in predicting crossbred performance. Regressions of actual crossbred calf performance on sire EBV for each of the traits differed little from their expectation of 0.5. Angus sires produced crossbred carcasses with the highest P8 and lowest RBY but highest IMF. In contrast, crossbred progeny from Belmont Red sires had the lightest 400W and CWT, lowest P8, and highest RBY. Estimates of rpc were 0.48, 0.48, 0.83, 0.95, 1.00, and 0.78 for 400W, CWT, RBY, IMF, P8, and SEMA, respectively. Commercial breeders selecting sires for crossbreeding programs with Brahman females, based on EBV computed from purebred data, might encounter some reranking of sire's performance for weight-related traits, with little expected change in carcass traits.     

Synchronization of Bos indicus x Bos taurus cows for timed artificial insemination using gonadotropin-releasing hormone plus prostaglandin F2alpha in combination with melengestrol acetate

Nonlactating Bos indicus x Bos taurus cows were used in three herds to determine the efficacy of different PGF2alpha treatments in combination with GnRH and melengestrol acetate (MGA) for a timed artificial insemination protocol. The start of the experiment was designated as d 0, at which time cows were assigned a body condition score and received 100 microg of GnRH. Cows were fed MGA (0.5 x mg x cow(-1) x d(-1)) on d 1 to 7. On d 7, cows received either a single injection of PGF2alpha (Lutalyse sterile solution; 25 mg; n = 297), a single injection of cloprostenol sodium (Estrumate; 500 microg; n = 297), or half the recommended dose of PGF2alpha (12.5 mg; n = 275) on d 7 and 8. On d 10, all cows were artificially inseminated and received 100 microg of GnRH. Pregnancy rates to the timed artificial insemination (39%) were not affected by treatment, herd, or treatment x herd. There was an effect (P < 0.01) of artificial insemination sire on timed artificial insemination pregnancy rate for one herd, but not the other two herds. Herd influenced (P < 0.05) 30-d pregnancy rates, but there were no treatment or treatment x herd effects as 72.3% of the cows became pregnant during the first 30 d of the breeding season. Results indicate that the type of PGF2alpha treatment administered 7 d after GnRH did not influence timed artificial insemination pregnancy rates in nonlactating Bos indicus x Bos taurus cows.     

Heterosis and breed effects on maternal and individual traits of Bos indicus breeds of cattle

Data were analyzed to estimate the effects of heterosis and breed on a series of maternal and individual traits. Crossbred cows were Boran X Ankole and Boran X Zebu; straight-bred cows were Ankole, Boran and Small East African Zebu (Zebu). Cows of all breed groups were mated to Friesian, Brown Swiss and Simmental sires to produce crossbred progeny. While not generally significant, the average effects of heterosis of both crosses for the traits analyzed were: calf crop born, 7.0%; preweaning viability, 7.2%; overall viability, 7.3%; birth weight, 6.0%; weaning weight, 5.4%; 12-mo weight, 4.2%; 18-mo weight, 3.7%; 24-mo weight, 3.6%; calf weight weaned per cow exposed to breeding (cow productivity index), 24.5%; cow parturition weight, 3.5%; cow weaning weight, 4.2% and cow mean weight, 4.0%. Boran cows weaned 31.8 kg (48.0%) more (P less than .05) calf weight per cow exposed to breeding than Ankole cows. Boran cows were generally superior to Zebu cows in progeny weights at all ages (P less than .01). Boran cows weaned 34.5 kg (54.3%) more (P less than .05) calf weight per cow exposed to breeding than Zebu cows. Boran cows weighed an average of 70.8 kg more (P less than .01) than Zebu cows. Although progeny of Ankole dams were heavier (P less than .05) than the progeny of Zebu dams at all ages, the two breeds did not differ (P greater than .05) in calf weight weaned per cow exposed to breeding. Mean weight of Ankole cows was 75.8 kg heavier (P less than .01) than mean weight of Zebu cows.     

Life span of beef-type Bos taurus and Bos indicus x Bos taurus females in a dry, temperate climate

Females representing Hereford, Red Poll, F1 Hereford x Red Poll, F1 Red Poll x Hereford, F1 Angus x Hereford, F1 Angus x Charolais, F1 Brahman x Hereford, and F1 Brahman x Angus breed types were evaluated from birth until 10 yr of age. Of 308 females born alive, 35.7% died or were culled because of injury, serious illness, or reproductive failure. Breed types differed (P less than .01) in total number of mating seasons per cow and total number of progeny born and weaned. Values for lifetime total number of calves weaned were as follows: Hereford, 4.54; Red Poll, 5.45; Hereford x Red Poll, 4.45; Red Poll x Hereford, 5.49; Angus x Hereford, 5.98; Angus x Charolais, 5.57; Brahman x Hereford, 6.96; and Brahman x Angus, 6.22. Brahman crosses (P less than .01) and Angus x Charolais (P less than .10) exceeded Hereford dams in lifetime total number of calves weaned but did not differ from Angus x Herefords. Analysis of the Hereford-Red Poll diallel showed no evidence of heterosis in life span traits. Results indicate that breed type was a major source of variation in reproductive life span of beef-type females. F1 Bos indicus crosses and Angus x Herefords were outstanding in longevity.     

Evaluation of reproductive traits in Bos taurus and Bos indicus crossbred heifers: effects of postweaning energy manipulation

Reproductive traits were evaluated in Bos taurus and Bos indicus crossbred heifers that were fed different diets during the postweaning period. The study was designed in a 2 x 2 x 2 factorial arrangement of treatments. Angus x Hereford (AH; n = 148) and Brahman x Hereford (BH; n = 148) heifers were sorted after weaning by body weight into light (LW) and heavy (HW) weight blocks. Heifers in each weight block were assigned to diets calculated to reach a target weight of 55% (LE) or 65% (HE) of their projected mature weights by the start of the breeding season. Puberty was determined after a 160-d observation period and characterized by the following criteria: 1) behavioral estrus, 2) presence of a palpable corpus luteum (d 6 to 10; estrus = d 0), and 3) rise in serum progesterone above 1 ng/ml (d 6 to 10). A higher (P = .01) proportion of AH heifers than of BH heifers reached puberty by the breeding season (93% vs 67%). Interactions of breed x weight block and energy level x weight block also contributed to this difference. Weight at puberty was heavier (P = .001) among HE than among LE heifers and greater for heifers in HW than for those in LW blocks (P = .02). Differences in prebreeding weight, body condition, average daily gain, hip height, and pelvic area were influenced selectively by breed, energy level, or weight block. Pregnancy rates were higher (P = .01) among AH than among BH heifers. Incidence and severity of dystocia was influenced by the breed x energy level interaction (P = .01). Brahman x Hereford heifers had less (P = .01) dystocia than AH heifers, HE heifers had less (P less than .02) dystocia than LE heifers, and HE-AH heifers had less (P less than .01) dystocia than LE-AH contemporaries. Subsequent duration of the postpartum interval to estrus was shorter (P = .002) among AH than among BH females. Pregnancy rates at the end of the 2nd yr were higher (P = .02) among LW than among HW females and weights were heavier (P = .001) at weaning among calves weaned from BH dams.     

Allele frequencies of gene polymorphisms related to economic traits in Bos taurus and Bos indicus cattle breeds

Allele frequencies of 10 representative polymorphisms for beef and milk traits were investigated for a total of 240 animals from Bos taurus and Bos indicus breeds, including two Japanese groups (Japanese Black and Japanese Brown), two East Asian groups (Korean and Mongolian), three European groups (Holstein, Angus and Hereford) and a Bos indicus group in South Asia (Myanmar, Laos and Cambodia). The Japanese Black revealed unique genetic construction in GH, FASN and SREBP‐1 and the other Asian populations show intermediate frequencies between European and Japanese populations. The Bos indicus group showed low favorable allele frequencies in most of the genes. The study showed the variability and distribution of 10 genes affecting economic traits among world representative cattle breeds. The genetic information would contribute to elucidating the genetic background for worldwide cattle breeds and the possibility of improvement using the markers.     

Output/input differences among nonpregnant, lactating Bos indicus-Bos taurus and Bos taurus-Bos taurus F1 cross cows

Nonpregnant F1 crossbred cows, progeny of either Hereford (H) or Angus (A) dams and sired by Brahman (Bm), Sahiwal (Sw), Pinzgauer (Pz), H, or A sires, were fed to maintain initial weight while rearing Charolais (C)-sired progeny for a period of 126 d in drylot commencing at about 48 d postpartum. Cow-calf pairs were assigned to equalize cow age, calf sex, and breed of cow's dam among three replicate pens of approximately 12 pairs each. Cows and calves were weighed every 2 wk and feed intake was adjusted to minimize change in cow weight. Metabolizable energy (ME) consumption for zero cow weight change was estimated by regression. Milk production was estimated by weight-suckle-weigh at 58, 85, 125, and 170 d of lactation. Calf gain (GAIN, kg) relative to cow weight (CWT1, kg) was higher (P less than .01) for calves from Bm-X (139.5/585) and Sw-X (132.2/534) than for calves from Pz-X (127.2/552) and HA-X (116.9/547) cows. Estimated mean daily production of milk was 7.40, 7.15, 7.28, and 6.37 kg for the Bm-X, Sw-X, Pz-X, and HA-X, respectively. Total cow ME intake (TMEcow) for breed groups ranked (P less than .05) with cow size and milk production, and calf creep-feed intake (FMEcalf) was inversely related to estimated milk intake. Proportion of total feed ME (TMEcow+calf) consumed by calves was higher (P less than .05) for HA-X cows (18%) than for the others (14%). Total efficiency of calf gain in weight (GAIN/TMEcow+calf) was 11% greater (P less than .05) for crossbred cows of Bos indicus X Bos taurus (Bm-X, Sw-X) than for Bos taurus X Bos taurus (Pz-X, HA-X) cows (35 vs 32 g/Mcal) in the 126-d lactation period.     

Effects of time of suckling during the solar day on duration of the postpartum anovulatory interval in Brahman x Hereford (F1) cows.

Previously published reports have indicated that postpartum anovulatory intervals can be markedly reduced and rebreeding performance enhanced in Bos taurus cows by eliminating nighttime suckling. We sought to confirm this hypothesis by examining the effects of day, nighttime, and ad libitum suckling on suckling behavior of calves, duration of the postpartum anovulatory interval, and pregnancy rates in 45 fall-calving Brahman x Hereford (F1) cows. Beginning on d 9 to 12 postpartum, calves were removed from lactating cows from 0700 to 1900 (Night-Suckled, n = 15) or from 1900 to 0700 (Day-Suckled, n = 15), or remained with their dams continuously (Ad Libitum-Suckled, n = 15). Cows in each group were maintained with fertile Angus bulls from d 10 postpartum until the first normal luteal phase or 100 d postpartum, whichever occurred first. Cows were observed for estrous behavior twice daily, and jugular blood samples were collected twice weekly for the determination of serum progesterone concentration. Mean number of suckling episodes per 24 h was greater (P < .0001) for the Ad Libitum-Suckled group than either Night- or Day-Suckled groups (5.9+/-.42 vs 3.8+/-.14, and 3.9+/-.32, respectively). Hourly analysis of suckling episodes in the Ad Libitum group indicated that they were not skewed toward a particular period, with suckling occurring at a periodicity of 4 to 6 h. Intervals to the first rise in progesterone > or = 1 ng/mL (32+/-2.5, 32+/-4.5, and 31+/-1.7 d, respectively), first normal luteal phase (38+/-3.1, 38+/-3.8, and 37+/-2.5 d, respectively), and first estrus (43+/-3.5, 40+/-3.9, and 36+/-1.1 d, respectively) did not differ (P > .05) among the three groups. Similarly, cumulative pregnancy rates within 100 d after calving did not differ (P > .05). These results in Bos indicus x Bos taurus (F1) cattle do not support the previous conclusions in Bos taurus that eliminating nighttime suckling reduces the postpartum anovulatory interval.     

Effects of induced hypothyroidism on ovarian response to superovulation in Brahman (Bos indicus) cows.

To evaluate the effects of hypothyroidism on ovarian function, multiparous, nonlactating Brahman cows (n = 18) were assigned randomly to dietary treatments containing either 0 (C; n = 9) or 4 mg x kg BW(-1) x d(-1) 6-n-propyl-2-thiouracil (PTU; n = 9), to suppress thyroid function, in the feed concentrate. Weekly changes in BW and body condition score (BCS) were recorded. Dietary treatments began on d 10 of the estrous cycle. Ten days after the first treatment estrus, all cows received daily i.m. injections of 25 IU of porcine FSH over a 3-d period. Seven days after AI, embryos were collected nonsurgically, and the ovaries were removed via midflank laparotomy. Based on thyroxine (T4) concentrations after 49 d of treatment, five cows were hypothyroid (H-PTU) and four were partially suppressed (P-PTU). Cows in the PTU group had greater (P<.01) ADG, (P<.05) ovarian weights, and numbers of large (> or =8 mm) (P<.05) follicles. Cows in the PTU group had lower embryo recovery rate (P<.001), fertilization rate (P<.001), and percentage of blastocysts (P<.1) than C cows. The H-PTU cows had greater numbers of luteinized follicles (P<.06), greater concentrations of progesterone (P4) in the follicular fluid at all size categories (P<.1), and greater numbers of corpora lutea (P<.05) than C cows. The ratio of luteal to serum P4 on d 7 was greater (P<.05) in hypothyroid cows. Induced hypothyroidism improved weight gain and BCS, increased ovarian response to FSH, and affected ovulation, fertility, and P4 secretion in superovulated Brahman cows.     

Effect of age at first calving and milking system on the lactation performance of F1 Bos indicus/Bos taurus crossbreds in Sabah

Summary This paper examines the effect of age at first calving and milking system on the overall lactation performance and incidence of lactation failure of 442 F₁ Bos indicus/Bos taurus dairy crossbreds in Sabah. The two types of crossbred used in the study were imported F₁ Sahiwal x Friesian and locally bred Friesian x Local Indian Dairy. Heifers which did not lactate for at least 120 days or produced less than 20 kg of milk during the fourteenth week of lactation were considered to have failed to establish a lactation. The imported and locally bred heifers recorded failure rates of 23·4 and 21·4% respectively. Three milking systems were examined namely machine milking without calf, machine milking with calf and hand milking. They produced failure rates of 30, 12 and 5·6% respectively. The cows that passed recorded 120 day milk production figures of 878, 1,134 and 1,054 kg respectively. The three age groups of <30 months, 30 to 34 months and >34 months recorded failure rates of 37, 22 and 10% respectively. The heifers machine milked without their calf which calved at <30 months of age recorded a failure rate of 44% while those which calved at >34 months recorded a failure rate of only 17%.

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Resumen Este artículo examina los efectos de la edad al primer parto y el sistema de orde?o, sobre la producción de leche e incidencia de fallas en la lactación, de 442 F₁ Bos Indicus/Bos Taurus en Sabah. Los dos tipos de cruces utilizados en el estudio fueron F₁ Sahiwal x Friesian y Friesian locales x animales Indúes locales. Las vaquillas que no lactaron en los primeros 120 días o produjeron menos de 20 kg de leche durante la semana 14 de lactación, fueron consideradas fallas para efectos del experimento. Las vaquillonas locales e importadas tuvieron fallas de 21·4% y 23·4% respectivamente. Se ensayaron tres sistemas de orde?o a saber, con màquina sin ternero, máquina con ternero, y orde?o manual. Estos produjeron fallas del 30%, 12% y 5·6% respectivamente. Las hembras que pasaron la prueba, produjeron en 120 días de lactación 878 kg, 1·134 kg y 1·054 kg respectivamente. Los tres grupos de menos de 30 meses, de 30 a 34 meses y de más de 34 meses de edad, registraron un fallo del 37%, 22% y 10% respectivamente. Las vaquillas orde?adas a màquina sin ternero y que tuvieron ternero antes de los 30 meses de edad, registraron un fallo del 44%, mientras que las que tuvieron ternero después de los 34 meses registraron un fallo del 17% solamente.

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Résumé Cet article examine l'effet de l'age au premier vêlage et du système de traite sur les performances globales de lactation et l'incidence des échecs de lactation chez 442 métis F₁ Bos indicus/Bos taurus au Sabah. Les deux types de métis examinés étaient des F₁ Sahiwal x Frison importés et des Frison x indien laitier local produits sur place. Les génisses qui n'ont pas produit de lait pendant au moins 120 jours ou ont produit moins de 20 kg de lait durant la 14e semaine de lactation ont été considérées comme impropres à établir une lactation. Les taux d'échecs ont été de 23,4% pour les génisses importées et de 21,4% pour celles produites localement. Trois systèmes de traite ont été examinés à savoir: machine à traire sans veau, machine à traire avec veau, traite manuelle. Ils ont produit des taux d'échecs de 30, 12 et 5,6% respectivement. La production des vaches qui ont passé le cap des 120 jours de lactation a été de 878, 1134 et 1054 kg respectivement. Les trois groupes agés de moins de trente mois, trente à trente-quatre mois et plus de trente-quatre mois ent enrigistré des taux d'échec de 37%, 22% et 10% respectivement. La machine de génisses sans veaux qui vélissaient à moins de 30 mois a enregistré des taux d'echec de 44% tandis que ceux qui velissaient à plus de 34 mois ont registre des taux d'échec de seulement 17%.