BRAHMAN NEWS SEPTEMBER 2014 ISSUE #184 PAGE 30
By Paul Williams TBTS TECHNICAL OFFICER
A major research project within the Cooperative Research Centre for Beef Genetic Technologies (Beef CRC) studied ways to define the genetic control of traditional and novel measures of reproductive performance in Tropical cattle in Northern Australia. One of the major project aims was to estimate the genetic association of young bulls’ reproductive traits with female reproduction and to identify the male genetic indicator traits that can be used to increase the rate of improvement in female reproduction in Northern Australia.
PROJECT DESIGN
A total of 4063 male progeny were generated by natural mating between the years 2004-2010 from cows involved in the Beef CRC Lifetime Fertility Project. These were comprised of 1629 Brahmans and 2124 Tropical Composites. A total of 136 sires were used to generate the progeny, comprised of 60 Brahmans and 76 Tropical Composites. Of these, 40 sires, 13 Brahmans and 27 Tropical Composites, were used in multiple years and locations to generate genetic linkage.
The male progeny were breed and run till weaning on research stations at “Brian Pastures” Gayndah, “Toorak” Julia Creek, “Brigalow Theodore” ,“Swan’s Lagoon” Ayr and “Belmont” Rockhampton. After weaning the male progeny were transported and run at 2 locations being “Brigalow” (progeny from “Brian Pastures”, “Toorak”, “Brigalow” and “Swans Lagoon”) and “Belmont” (progeny from “Belmont”). A small number of male calves from Belmont were sent to Brigalow to maintain linkage.
The bulls were recorded pre-weaning (4 months), at weaning (6 months), and then every 3 months through to 2 years of age for a range of reproductive traits. The measurements that were recorded are outlined in Tables 1 and 2.
Reproductive trait measurements included scrotal circumference, bull breeding soundness evaluation (BBSE), sperm morphology assessment at 12, 18 and 24 months of age and analysis of blood hormones levels for Luteinising hormone (influences testosterone production and onset of puberty, Inhibin (influences the regulation of sperm production), and Insulin-like growth factor-1 (IGF-1).
In addition, male progeny were measured for a comprehensive range of other production traits such as live weight, flight time, fatness, eye muscle area (EMA) and hip height.
Table 1: Reproductive Trait Measurements Collected at Each Different Age
| AGE (MONTHS) | WEIGHT | SCROTAL | BLOOD SAMPLE | BBSE |
| 0 | 3 | |||
| 4 | 3 | 3 | ||
| 6 | 3 | 3 | 3 | |
| 9 | 3 | 3 | ||
| 12 | 3 | 3 | 3 | 3 |
| 15 | 3 | 3 | ||
| 18 | 3 | 3 | 3 | 3 |
| 21 | 3 | 3 | ||
| 24 | 3 | 3 | 3 | 3 |
Table 2 : Measurements Collected within Bull Breeding Soundness Evaluation (BBSE)
| PHYSICAL SCORES | REPRODUCTIVE CHECK | SEMEN EVALUATION | SPERM ASSESSMENT |
| Leg Structure | Scrotal Circumference | Mass Activity | Morphology |
| Feet | Testis Tone | Motility | – Percent normal sperm |
| Eyes | Sheath | – Percent abnormal sperm | |
| Body Condition | Penis |
RESULTS
YOUNG BULLS AND HEIFER PUBERTY
The research showed that the genetic correlation between male semen quality traits, mass activity, motility and percent normal sperm (PNS), and scrotal circumference were generally moderately correlated and consistent in the direction of their relationship with heifer puberty traits in both Brahmans and Tropical Composites. The genetic correlation between male hormone traits and heifer age of puberty were low with the exception of IGF-1 in Brahmans
YOUNG BULLS AND FEMALE REPRODUCTION AT MATING 1 AND MATING 2
Genetic correlations between male reproductive traits and female reproduction at mating 1 were generally low to moderate for both Brahmans and Tropical Composites and followed a similar pattern observed to their relationship with heifer age at puberty.
Genetic correlations between male reproductive and female traits at mating 2 were low for the male hormone traits, while semen quality traits in both Brahmans and Tropical Composites showed consistent correlations with mating 2 female traits when measured on male progeny at 18 and 24 months of age. Scrotal circumference was moderately correlated with mating 2 female traits when measured at 18 months of age in Brahman but had a low correlation with no consistent trend in Tropical Composites.
YOUNG BULLS AND LIFETIME FEMALE REPRODUCTION
Genetic correlations between male semen quality traits, mass activity and motility, were highly correlated with lifetime female reproduction when measured at 18 months of age. Scrotal circumference showed no consistent relationship with lifetime female reproduction. Genetic correlations between male reproductive traits and lifetime female reproduction were generally low for male hormone traits
The results also showed that bulls with a larger protruding prepuce were genetically related to female with lower reproduction performance
CONCLUSIONS
The results illustrate that substantial opportunity exists to improve female fertility in tropical beef cattle breeds by recording and selecting on early-in-life bull reproduction traits.
Scrotal circumference at younger ages is a modest genetic predictor of heifer age of puberty but not on lifetime female reproduction. Semen quality such as motility, mass activity and percent normal sperm, sheath traits and some male hormone levels, were highly correlated with female reproduction, particularly with the post partum anoestrus traits in first lactation females. The traits are consequently useful as indirect selection criteria for improving female reproduction in Tropical cattle.
Opportunities exist to improve lifetime weaning rates by using bulls that have some information on the fertility of the dams from which they were derived. Preferably, these bulls should have an EBV for Days to Calving (DTC) and at the minimum, a history of their female relatives’ previous calving outcomes. Replacement bulls should be measured and selected based on favourable Scrotal Circumference EBVs and favourable results in BBSE for semen traits such as motility, mass activity and percent normal sperm. It would also be advantageous to select bulls with good temperament and good sheath score.
Table 3: Genetic correlation between key bull and female reproduction traits
| BULL TRAITS | FEMALE TRAITS | ||
| AGE OF PUBERTY | POST PARTUM ANOESTRUS | LIFETIME FEMALE REPRODUCTION | |
| Brahman | |||
| IGF-1 (6) | -0.56 (0.11) | -0.21(0.15) | 0.20 (0.19) |
| Scrotal Circumference (18) | -0.27 (0.10) | -0.27 (0.13) | 0.12 (0.17) |
| Mass activity (18) | -0.51 (0.17) | -0.27 (0.18) | 0.54 (0.26) |
| Motility% (18) | -0.49 (0.20) | -0.37 (0.22) | 0.51 (0.28) |
| Percent Normal Sperm (18) | -0.48 (0.21) | -0.52 (0.31) | -0.01 (0.31) |
| Tropical Composites | |||
| IGF-1 (6) | -0.43 (0.11) | -0.10 (0.18) | -0.02 (0.17) |
| Scrotal Circumference (18) | -0.17 (0.11) | 0.13 (0.16) | 0.14 (0.16) |
| Mass activity (18) | -0.24 (0.20) | -0.68 (0.36) | 0.21 (0.25) |
| Motility% (18) | -0.38 (0.18) | -0.73 (0.35) | 0.29 (0.24) |
| Percent Normal Sperm (18) | -0.24 (0.17) | -0.30 (0.25) | 0.41 (0.22) |
For further information contact:
PAUL WILLIAMS
Tropical Beef Technology Services
Phone 07 4927 6066
or paul@tbts.une.edu.au
